An electronic storage circuit for storing information, in particular switch control information for alternately switching circuit parts of integrated monolithic circuits, having two series connections inserted between the two poles of a voltage supply source each including an EPROM transistor and a MOS transistor, the control gates of the two EPROM transistors being connected jointly with a reference voltage source, and the gates of the two MOS transistors with the connection point of the EPROM transistor and the MOS transistor of the other series connection.

Integrated monolithic circuits are complicated structures, in particular if they have a high scale of integration, and necessitate great development effort and extensive preliminary work before they can go into volume production. High piece numbers are therefore desired for each integrated circuit. one occasionally requires several versions of a certain integrated circuit which often differ only slightly. For example it should be possible to choose between an RC oscillator and a quartz oscillator as a clock generator.
A conventional method for providing several similar versions of a certain type of integrated circuit is to provide all components for all versions of this certain type of integrated circuit on one and the same chip and to apply different conduction patterns for the various versions. However different masks are needed for producing the particular conduction pattern required.
This effort can be avoided by equipping one and the same integrated circuit with all circuit parts and conduction patterns necessary for its various versions and equipping this integrated circuit with switches for internally switching to the particular desired version with the aid of corresponding switch control signals. This also leads to the advantage that such an integrated circuit can be switched from the initially selected version to another version during the development phase or even during use.
For this purpose one can use a storage circuit of the type described in Design+Elektronik, no. 13, 27th June 1989, Markt & Technik, pages 46, 48 and 49, and in Electronic Engineering, September 1988, pages 44, 45, 48, 50 and 54. The switches of the integrated circuit can thereby be controlled in accordance with the storage state of the storage circuit.
As is well-known, erasable programmable read only memory (EPROM) transistors have a floating gate between the conduction channel and the control gate. The floating gate of the EPROM transistor contains no charges in the unprogrammed state, while it contains charges in the programmed state. Looking at an n-channel state. The EPROM transistor therefore becomes conductive when a voltage of about 1.9 V is applied to the control gate. With the programmed n-channel EPROM transistor negative charges are found on the floating gate, which means that such a transistor only conducts in the programmed state as of a control gate voltage of more than 5 V.
This different behavior between the programmed and unprogrammed EPROM transistor is utilized for information storage. This information can be used for example to control in the above-mentioned way the switching state of hardware switches located on the same semiconductor chip as the storage circuit.
With a storage circuit of the above-mentioned type no error can occur in terms of false storage information being delivered. After disturbances this storage circuit always independently resumes the correct circuit state in which it reliably delivers the programmed storage information. If there is a supply voltage drop, whether due to disturbances or to a deliberate shut-off, it suffices merely to turn the supply voltage back on to deliver the correct storage information again. No readout signal is required.
Such a storage circuit is not only suitable for providing switch control information for switches, but it can also be used advantageously wherever information is to be reliably stored and correctly outputted, over a very long time and without disturbances. This storage circuit is also excellently suited for nonvolatile memories for example.
It is generally necessary to perform repeated testing on the storage circuit and the circuit controlled by it. It may also become necessary to subsequently change the functions of the circuit controlled by the storage circuit, which means changing the storage fill of the storage circuit and thus reprogramming it. Testing and/or reprogramming might be necessary during operation of the controlled circuit without this operation being interrupted or impaired.


A method of planarizing a first side of a semiconductor wafer with a polishing system includes the step of polishing the first side of the wafer in order to remove material from the wafer. The method also includes the step of moving a lens of a confocal optical system between a number of lens positions so as to maintain focus on the first side of the wafer during the polishing step. The method further includes the step of determining a rate-of-movement value based on movement of the lens during the moving step. Moreover, the method includes the step of stopping the polishing step if the rate-of-movement value has a predetermined relationship with a movement threshold value. An apparatus for polishing a first side of a semiconductor wafer is also disclosed.

Semiconductor integrated circuits are typically fabricated by a layering process in which several layers of material are fabricated on or in a surface of a wafer, or alternatively, on a surface of a previous layer. This fabrication process typically requires subsequent layers to be fabricated upon a smooth, planar surface of a previous layer. However, the surface topography of layers may be uneven due to an uneven topography associated with an underlying layer. As a result, a layer may need to be polished in order to present a smooth, planar surface for a subsequent processing step. For example, a layer may need to be polished prior to formation of a conductor layer or pattern on an outer surface of the layer.
In general, a semiconductor wafer may be polished to remove high topography and surface defects such as scratches, roughness, or embedded particles of dirt or dust. The polishing process typically is accomplished with a polishing system that includes top and bottom platens (e.g. a polishing table and a wafer carrier or holder), between which the semiconductor wafer is positioned. The platens are moved relative to each other thereby causing material to be removed from the surface of the wafer. This polishing process is often referred to as mechanical planarization (MP) and is utilized to improve the quality and reliability of semiconductor devices. The polishing process may also involve the introduction of a chemical slurry to facilitate higher removal rates, along with the selective removal of materials fabricated on the semiconductor wafer. This polishing process is often referred to as chemical mechanical planarization or chemical mechanical polishing (CMP).
In these polishing processes, it is often important to determine when an outer layer or film has been polished to a desired planarity level. In particular, it is desirable to know when the outer layer of the semiconductor wafer has been polished to a planarity level which is acceptable for presentation of the wafer to a subsequent fabrication process.
In order to determine when a wafer has been polished to a desired planarity level, systems and techniques have heretofore been utilized which polish the wafer down to a predetermined thickness. For example, a typical method employed for determining when the wafer has been polished down to a predetermined thickness is to measure the amount of time needed to planarize a first wafer to the desired thickness, and thereafter polishing the remaining wafers for a similar amount of time. In practice this method is extremely time consuming since machine operators must inspect each wafer (e.g. measure the thickness thereof) after polishing. In particular, it is extremely difficult to precisely control the removal rate of material since the removal rate may vary during the polishing of an individual wafer. Moreover, the removal rate may be diminished in the process of polishing a number of wafers in sequence. Yet further, such methods do not actually measure the planarity of the outer layer, but rather simply make an assumption that the outer layer has been polished to an acceptable planarity level when the wafer is polished to the desired thickness.
Another method employed for determining if the wafer has reached the desired thickness is to impinge a light beam, such as a laser light beam, onto the semiconductor wafer in order to determine the thickness of the wafer. Various techniques have been used to detect when an outer film associated with the semiconductor wafer reaches the desired thickness. For example, the apparatus disclosed in U.S. Pat. No. 5,151,584 issued to Ebbing et al directs an incident laser beam onto the surface of a semi-transparent thin film (e.g. silicon dioxide) of a semiconductor wafer during etching thereof. A first portion of the incident beam is reflected from the top surface of the film, and a second portion of the incident beam is reflected from the bottom surface of the film. Since the film has a finite thickness, the two reflections will either constructively or destructively interfere with one another. As the layer is etched, its thickness is changed thereby cycling intensity of the reflected beam through constructive and destructive interference patterns which may be utilized to determine when the wafer has been etched to the desired thickness. Such a technique has a number of drawbacks associated therewith. For example, such a technique may only be utilized after certain steps in the fabrication process. For example, such a technique may be useful for measuring thickness of a blank wafer, but has been found to perform unsatisfactorily when utilized to measure thickness of a patterned wafer. Moreover, similarly to the manual inspection method discussed above, such a technique does not actually measure the planarity of the outer layer, but rather simply makes an assumption that the outer layer has been polished to an acceptable planarity level when the wafer is etched down to the desired thickness.
In order to overcome the above-mentioned drawbacks associated with wafer thickness-based polishing endpoint techniques, a number of techniques have heretofore been utilized in an attempt to measure the actual planarity of the outer layer of the wafer. For example, a method which has heretofore been employed for determining when the wafer has been polished to a desired planarity level is to periodically remove the wafer from the polishing system, and thereafter measure the planarity of the wafer with an instrument such as an atomic force microscope or a profilometer. If the wafer has been polished to the desired planarity level, the wafer is released to a subsequent fabrication step. However, if the wafer has not been polished to the desired planarity level, the wafer must be placed back into the polishing system for further polishing thereof. It should be appreciated that numerous measurements may be required to reach the desired planarity level. Hence, in practice this method is extremely time consuming since machine operators must measure each wafer (i.e. measure the planarity thereof) a number of times during the polishing process.
Thus, a continuing need exists for a method and an apparatus for in situ measurement of the planarity of the outer layer of a semiconductor wafer during polishing thereof.

Method and apparatus for detecting a planarized outer layer of a semiconductor wafer with a confocal optical system


A filament forming apparatus has a bushing that includes a high palladium content screen along with structural components and non-structural components. The structural components are formed of a first material having a high creep strength and the ability to withstand corrosive effects of molten mineral materials. The non-structural components are formed of at least a second material that is different from the first material.

Fibrous products have been manufactured for many years using precious metal bushings, or feeders. Such feeders include a perforated bottom plate, or wall, commonly referred to in the art as a tip plate, which retains a pool of molten mineral material. Streams of molten mineral material issue from the openings, or tips, in the bottom bushing wall. By suitable means the streams of material are then attenuated and collected in the form of fibers.
The material feeders, or bushings, must be chemically resistant to the action of molten mineral material and must be dimensionally stable at high operating temperatures. Currently, such bushings are manufactured from elemental precious metals or binary alloys, such as, for example, Pt or Pt—Rh alloys. Precious metals are very expensive. If bushings could be formed with smaller amounts of such precious metals or could be formed with less expensive materials, a tremendous economic advantage would be realized.
Another difficulty also encountered in the use of precious metal bushings stems from the fact that, after a period of time, precious metal bushings tend to creep or deform in service. Such creep or deformation adversely affects the quality of the fibers. The deformation requires the bushing to be removed from service earlier than if only the corrosive and erosive effects of the material had taken their toll on the bushing. Since the precious metal feeders have a limited life, there is a need in the art to provide for bushings that have an improved operating life.

This patent is subject to a terminal disclaimer.

Palladium screens for bushing assembly and method of using


A testing system for digital transmission lines with a metallic loopback and direct current bypass for use with regenerative repeaters. The Bell telephone network typically includes transmit and receive lines interconnected to a central office. Regenerative repeaters positioned along the lines detect signals and regenerate new signals. The present invention includes a controller, loopback line, and bypass. The loopback line interconnects the transmit and receive lines upon receiving a test activation signal from the controller. The bypass allows direct current to pass through to the rest of the line during a test. Accordingly, when a test of the telephone lines is to be performed, lines will allow the test signal to loop back to the source of origin, but will block the loopback of DC power signals. Moreover, DC power is supplied to the rest of the transmission line, in the same manner as when the testing procedure is not occurring. Moreover, the loopback line is positioned such that the overload protection circuitry is also subject to the performance test.

The present invention relates generally to testing systems for digital transmission lines and, more particularly, to a testing system for digital telecommunications transmission lines that allows for a metallic loopback of test data and a direct current ("DC") bypass. Many digital telecommunications transmission facilities include a central office which may transmit data, or "payload," signals over transmission lines to customer premises equipment. Typically, the payload is sent over the transmission lines differentially on two copper conductors, known as the Tip-Ring pair.
The Bell telephone system in the United States, for example, has widely utilized Digital "D" multiplexing pulse code modulation systems. A "D" channel bank, for example, commonly provides multiple DS-1 signals that are carried on a T-1 Transmission system. Each T-1 carries 24 Full Duplex channels on two pairs of exchange grade cables. One pair of cables is provided for each direction of transmission.
For clarification and simplification of terminology, the pair of cables carrying signals from the central office to the customer premises equipment is designated as a "transmit" line, and the pair of cables transmitting data from the customer premises equipment to the central office is designated as a "receive" line. This designation is made for convenience only; of course, when an observer (or testing technician) changes position from a central office to the customer premises, what used to be a "transmit" line becomes a "receive" line, and the "receive" line becomes a "transmit" line.
Payload signals are received by the telephone company and are transmitted, via the transmission lines, to a series of regenerative repeaters. Such repeaters are spaced along the transmission lines approximately every 6,000 feet. Each length of approximately 6,000 feet of cable may be designated as a "span."
The first repeater receives the data from the central office repeater, but, because of transmission line losses, jitter, noise, interference, and distortion, the signal will have degraded. The repeater recognizes the presence or absence of a pulse at a particular point in time and, if appropriate, regenerates a relatively clean, new pulse.
The regenerative repeater, or line repeater, is powered through the transmission cable itself to generate new pulses. Longitudinal, or common mode, direct current is applied supplied to the simplex lead to power the T-1 line repeaters. New pulses are transmitted by the repeater along more cable to either another line repeater or to the customer premises equipment.
As a part of its maintenance program, the telephone company may interconnect a test set (such as, for example, a Hewlett Packard 3787B test set) between the transmit and receive channels. The telephone company may then test the integrity of the lines and isolate (or "sectionalize") malfunctions along the transmission lines.
Such diagnostics may involve simply the ascertaining whether or not a particular span of cable provides continuity along its entire length. For example, an activating signal may be sent by the test set in, for example, the central office. The signal may designate a first repeater to "loopback" the signal from the transmit line to the receive line. Accordingly, a signal sent down the transmit line should then be received immediately thereafter at the receive line in the central office, if the lines to and from the repeater are continuous and the repeater has performed a loopback between the transmit and receive lines. In such a case, if continuity is proven, the test set may then instruct the repeater to connect the lines in standard transmission mode but, however, instruct the next most proximate repeater to loopback signals. Thereafter, if the test signal applied to the transmit line is not then also received at the receive line, the telephone company technician will know that the malfunction has occurred between the loopback of the first repeater and the loopback of the second repeater. The error in the line has then been sectionalized to a 6,000 foot interval rather than the entire length of the transmission line.
New generation DS1 fault location systems may perform even more complex diagnostics which, in addition to checking for discontinuities, can also look for transmission abnormalities such as bi-polar violations, "stress" pattern errors and, for example, provide information on the number of seconds of severely errored data that is transmitted along the lines. The types of performance evaluation messages possible are defined, for example, in the American National Standards Institute Specification T-1.403-1989. The telephone company wishes to be able to quickly and inexpensively isolate the location of, or sectionalize, the malfunction.
The craftsman also wishes to obtain true sectionalization of the transmission lines, and thus more precisely locate the difficulty. Importantly, the test equipment should not affect line performance, such that a line might perform differently with and without the test equipment applied to the line. For example, the stress patterns (occurrences of severely distorted information) may vary if the line is significantly altered in order to perform a sectionalization test.
Moreover, it is important that all portions of the transmission lines be subjected to a test when the telephone company performs a diagnostic test on a line's performance. There is typically a metal interface forming part of the physical connection between the repeater and the beginning (or end) of another span. The data looped back from the transmit to the receive line should be close to such metal, thus providing a "metallic" loopback. Such a metallic loopback thus, for example, may allow for the testing not only of the regenerative features of the repeater itself, but also of other circuitry, such as overload protection equipment that may be within the repeater. The overload protection circuitry can be damaged by lightening surges during lightening storms and extremely high voltages from shorted power lines.
Also, it is important that the components of the test system used in the field have relatively small physical size and weight. Moreover, a test system should be inexpensive to manufacture and install. Furthermore, the testing system should be reliable, so as to increase the reliability of the telephone system itself.
Unfortunately, many of the presently available performance monitoring systems are not ideally suited to the demands of the telephone companies. Many of the presently available systems do not allow a "metallic" loopback during testing. Such systems may allow for the testing of the regenerative aspects of the line repeater, but not of its overload protection circuitry.
Also, many available systems may, during testing, remove the DC power applied to spans and repeaters located farther away from the test set than the repeater which has been instructed to loopback signals. Such blocking of DC signals from the outlying spans and repeaters may affect the test results received during interrogation. Furthermore, prior art systems may require the installation of bulky, heavy, and expensive equipment in the field.

Testing system for digital transmission lines


Methods and apparatus for vacuum distillation of samples suspected of containing pollutants are disclosed. The vacuum distillation apparatus contains a condenser for separating water and/or another common interfering contaminant. The distilled pollutants are assayed using a gas chromatograph/mass spectrometer.

In recent years there has been a growing concern over exposure to toxins in the environment and food supply. The Federal Water Pollution Control Act Amendments of 1972 (P.L. 92-500) recognized the need for monitoring and establishing the presence of toxic substances in water. Organic pollutants are frequently present in very small amounts and often comprise a large number of similar compounds which may have been deposited at a particular location through a variety of means. Some of these pollutants are concentrated in the tissues of plants and animals and can be hazardous to these life forms as well as animals, including humans, that eat them. Thus the need exists for accurate measurements of trace amounts of contaminating pollutants.
While conventional chromatography and detection techniques are effective measurers and detectors of organic compounds, the samples to be tested contain the organic compound components in matrixes or are in matrixes which may interfere with the proper extraction and detection of the compound components in questions. Using conventional techniques, it has been difficult to determine certain compounds, to assess the degree of matrix effects on compound recovery and to accurately quantify the amounts of these and other compounds.
Soil, biological samples, oils and water each present their own unique difficulties and interfering chemicals. Techniques prior to, and even after, the vacuum extractor described in applicant's earlier U.S. Pat. No. 4,600,559 have not been particularly effective at detecting an accurate amount of a chemical in certain samples due to low rates of extraction and poor separation. For example, U.S. Pat. No. 4,960,711.
In the prior art, investigators have attempted to measure trace organic compounds by a number of techniques. One method is to sample gas from the head space above a sample in a closed container. The gas sample is then injected into a gas chromatograph for measurement. Details and variations on this technique are described in the following four references:
1. "Interim Method for the Sampling and Analysis of Priority Pollutants in Sediment and Fish Tissue" Environmental Protection Agency, Environmental Monitoring and Support Laboratory, Cincinnati, Ohio, p 18 and 45-268, Aug. 23, 1977,
2. "Sampling and Analysis for Screening of Fish for Priority Pollutants," "Analysis of fish for Volatile Organics by Head Space Analysis", U.S. EPA, Environmental Monitoring and Support Laboratory, Cincinnati, Ohio p. 14, Aug. 23, 1977,
3. "The analysis of Fish for Volatile Organics by Head Space Analysis" U.S. Environmental Monitoring and Support Laboratory, Cincinnati, Ohio p. 21,
4. Going, "Priority Pollutant Removal from Mine Drainage" Final Report, MRI Contract 4409- L3, Industrial Environmental Research Laboratory, Office of Research and Development, EPA Cincinnati, Ohio.
These methods have several drawbacks. First, the chemical of interest may not readily disassociate from the sample to permit accurate measurement in the gas. Second, water and other volatile compounds frequently interfere with the detection of the compound of interest. If the compound being detected can form an azeotrope, further complications exist. Third, these techniques are only effective for very volatile compounds.
Another existing technique for measurement of trace organic compounds involves pentane extraction of organic compounds from fish as discussed by Pearson et al, Proc. Royal Soc. Lond. B, 189: p. 305-332 (1975). This technique has the disadvantage of only measuring compounds which are soluble in pentane, do not react with pentane, are released from the matrix by liquid pentane and do not participate in a chemical reaction with any other compound being extracted by the pentane.
Another standard technique for measurement of trace organic compounds is to purge and trap. According to this technique, the sample is heated and an inert gas is passed through the sample to "purge" volatile compounds from the sample. The gas containing the compounds is passed through a trap which adsorbs the compounds. One such adsorbent is activated charcoal. The adsorbent is then heated to elute the compounds from this trap into a gas chromatograph for detecting and measuring the compounds. One example of this technique is Murray, Analytical Chim. Acta, 65 p. 261-270 (1973).
The purge and trap technique also has certain drawbacks as different compounds have variable rates of adsorption on adsorbents. Furthermore, heating the sample may cause degradation of the compounds of interest. The compounds concentrated in the adsorbent may react with each other or degrade because they are in a different matrix than the one from which they were extracted. Also the compounds being tested may polymerize or react with other compounds present to give byproducts, thereby making it difficult to detect the correct compounds present and causing simultaneous detection of compounds which never were in the sample. While the purge and trap technique recovers a wide mix of compounds, it still fails to adequately recover many compounds.
This may be especially true when non-aqueous samples are analyzed. For non-aqueous samples recoveries are further complicated by any additional affinity for compounds of interest to the solid phase over the aqueous phase. Non-volatile compounds are particularly hard to extract and measure accurately using this technique.
Some of the problems with heating a sample and trapping the released compounds have been ameliorated by using a vacuum instead of heat to extract compounds. Examples of this technique are Easley et al, J. Assoc. Off. Anal. Chem., 64(3) p. 653-656 (1981) and applicant's earlier publication, Hiatt, Analytical Chemistry, 53: p. 1541-1543 (1981).
Improvements in the purge and trap method have been provided as described in Hiatt, Analytical Chemistry, 55: p. 506-516 (1983) and Hiatt, U.S. Pat. No. 4,600,559. These publications disclose a vacuum extractor with cold traps to condense and collect the compounds being measured. While such a system is more effective than conventional techniques, it is cumbersome with plural cold traps and does not readily lend itself to automation. Additionally, this and all other systems permit the measurement of compounds in the gaseous phase only and do not permit measuring the azeotrope phase, the condensed phase or the residue in the sample container. Thus the previous systems are limited in their capabilities.

Vacuum extractor incorporating a condenser column

The United States of American as represented by the Administrator of the Environmental Protection Agency


A laminated phase plate is formed by laminating a first optical phase difference compensation plate, having a retardation between 100 and 180 nm for transmitted light, with a wavelength of 550 nm and a second optical phase difference compensation plate having a retardation between 200 and 360 nm for transmitted light with a wavelength of 550 nm. The optical phase difference compensation plates are arranged so that |xcex81xe2x88x92(2xc3x97xcex82)| is between 80 and 100 degrees. The term xcex81 is an angle between a vibration direction of linearly polarized light and a slow axis direction of the first optical phase difference compensation plate when the linearly polarized light, which is visible light and has a fixed plane of vibration, is incident on the second optical phase difference compensation plate. The term xcex82 is an angle between the vibration direction of linearly polarized light incident on the second optical phase difference compensation plate and a slow axis direction of the second optical phase difference compensation plate.

The present invention relates to a laminated phase plate for use in direct-viewing-type liquid crystal display devices used for office machinery including word processors and notebook-sized personal computers, various types of visual equipment and game equipment, a projection-type liquid crystal display device which displays an enlarged image by projecting an image of a reflective liquid crystal display illuminated by light source, and liquid crystal display devices such as a head-mount display which is fixed at the head of a viewer, and also relates to liquid crystal display devices incorporating the laminated phase plate.
Conventionally, an optical phase difference compensation plate composed of an oriented polymer film has been used for various applications. Examples of the optical phase difference compensation plates includes a xc2xc waveplate for giving a phase difference of {fraction (xcfx80/2)} between two linearly polarized lights having vibration planes perpendicular to each other, and a xc2xd waveplate for giving a phase difference of xcfx80 between them. Since the phase differences of these optical phase difference compensation plates originated from their retardation vary according to the wavelength of light, it was difficult to provide a uniform polarization state, which is obtained as a result of a phase difference, for lights of different wavelengths by a structure including only a single optical phase difference compensation plate.
In order to solve such a drawback, Japanese laid-open patent publication No. (Tokukaihei) 5-100114 discloses a xc2xd waveplate produced by a combination of a polarizer and a plurality of xc2xd waveplates, and a circular polarizer obtained by further adding a xc2xc waveplate to the combination.
In the former structure of these structures, by combining xc2xd waveplates, a condition for giving a phase difference of xcfx80 to light whose linearly polarized component has been selectively transmitted by the polarizer is ensured within a wide wavelength range. On the other hand, in the latter structure, a condition for giving a phase difference of {fraction (xcfx80/2)} is ensured within a wide wavelength range by adding a xc2xc waveplate to the above-mentioned structure. As a result, light having a wavelength within a range satisfying the xc2xd wavelength condition for giving a phase difference of xcfx80 becomes linearly polarized light oriented in a different direction from linearly polarized light prepared by a polarizer. With this structure, it is possible to produce linearly polarized light having a uniform vibration plane for wavelengths satisfying the xc2xd wavelength condition.
Moreover, as a color display, a liquid crystal display device having thin and light weight characteristics has been put to practical use. At present, a transmissive type liquid crystal display device using a light source as an illumination from behind has been most widely used as a color display device, and the application thereof has increased to various fields because of the above-mentioned characteristics.
A reflective type liquid crystal display device does not require a backlight for display, and therefore it can lower the power consumption by cutting the power for the light source and reduce the space and weight by the space and weight of the backlight as compared with the transmissive type liquid crystal display device. In other words, the reflective type liquid crystal display device can achieve a reduction in the power consumption, and is suitable for use in apparatuses aiming at reductions in their thickness and weights.
Furthermore, regarding the contrast characteristic of the display screen, in a light emitting type display devices as CRTs, a substantial degradation in the contrast ratio, i.e., a so-called washout, occurs outdoors in daylight. Besides, in this aspect, even in a transmissive type liquid crystal display device to which a low reflection treatment was applied, a lowering of visibility is unavoidable in an environment in which ambient light such as direct sunlight is extremely strong compared with display light.
On the other hand, in the reflective type liquid crystal device, since display light proportional to the amount of ambient light is obtained, the reflective type liquid crystal device is particularly suitable for use as a display section of apparatuses used in outdoor, such as personal digital tools, digital still cameras, and portable comcorders.
However, although the reflective type liquid crystal display device has such very advantageous application fields, it does not have a sufficient contrast ratio and reflectivity, and performances for achieving multicolor display, high definition display, moving image display, etc. Therefore, a reflective type color liquid crystal display device having sufficient practical characteristics has not been realized so far.
The following description will explain a reflective type liquid crystal display device in detail.
Since a conventional twisted nematic (TN) liquid crystal element is constructed with the use of two polarizers, the contrast ratio and the viewing angle characteristic are improved. However, since a liquid crystal modulation layer and a light reflecting layer is separated from each other by a distance equal to the thickness of a substrate, etc., parallax occurs due to the difference between a light path along which illumination light is incident and a light path along which the light is outgoing. Thus, in particular, a structure in which the twisted nematic liquid crystal element is used for a normal conventional transmissive type liquid crystal display using a combination of a single liquid crystal modulation layer and color filters which apply a plurality of color elements to different pixels is not suitable for a high resolution, high definition color display device. The reason for this is that, when the traveling direction of light passing through a color element during the incidence of light and that of light passing through a color element after the light is reflected tilt with respect to each other, the light path varies according to the tilt direction and tilt angle. For such a reason, a color display of a reflective type liquid crystal display device using this display mode has not been put to practical use.
Meanwhile, a guest-host (GH) type liquid crystal display element in which no polarizer or one polarizer is used and dye is added to a liquid crystal has been developed. However, the guest-host type liquid crystal element suffers from problems that the reliability is not sufficient due to the addition of dye and a high contrast ratio is not obtained because the dichroism ratio of the dye is low. In particular, in a color display using color filters, since the reflected light of the pixel in the dark state is observed together with the reflected light of the pixel in the bright state, the color purity is substantially lowered by such an insufficient contrast. In order to prevent the degradation of color purity, it is necessary to apply color filters of high color purity. However, when color filters of high color purity are used, the brightness is lowered. Thus, there is a conflict between the lowering of brightness and an advantages of the GH technique of achieving a high brightness without using a polarizer because this advantage is spoilt.
In view of the above-mentioned circumstances, liquid crystal display devices employing a structure in which one polarizer which is expected to achieve a high resolution, high contrast display (hereinafter referred to as the single polarizer structure) have been developed. As one example, a reflective (450 twisted type) TN type liquid crystal display device using one polarizer and xc2xc waveplates is disclosed in Japanese laid-open patent publication No. (Tokukaisho) 55-48733.
According to this prior art, a layer of liquid crystal twisted at 45xc2x0 is used, and the vibration plane of incident linearly polarized light is switched between two states, i.e., a state in which the vibration plane is parallel to the optical axis of the xc2xc waveplate and a state in which the vibration plane is oriented in a direction which differs from the direction of the optical axis by 45xc2x0 by controlling an electric field applied to the liquid crystal layer so as to achieve a black and white display. This liquid crystal cell is constructed by arranging a polarizer, a 45xc2x0-twisted liquid crystal cell, a xc2xc waveplate, and a reflector in this order from the incident side.
Additionally, the present inventors filed a patent application directed to a reflective type homogeneous structure realized by a combination of one polarizer, homogeneous alignment liquid crystal cell, and optical phase difference compensation plate (see Japanese laid-open paten publication No. (Tokukaihei) 6-167708). In this display mode, a homogeneous (no twisted planer) alignment liquid crystal layer and one optical phase difference compensation plate are placed between a reflector disposed on the inner surface of the liquid crystal cell and a polarizer provided on the outside of the liquid crystal cell (and optical phase difference compensation plate). In this structure, the light paths comprising the incident light path and outgoing light path pass through the polarizer only twice, and also pass through a transparent electrode, which is formed on one of glass substrates (upper substrate) of the cell and can not avoid light absorption, only twice. Therefore, with this cell structure, a high reflectivity can be obtained.
Furthermore, a structure in which a layer of twisted nematic liquid crystal is placed between a reflector (disposed on the inner surface of the cell) and one polarizer is disclosed in Japanese laid-open patent publication No. (Tokukaihei) 2-236523 and Japan Display ""89, p. 192.
The following descriptions will explain the theory of such a single polarizer display as disclosed in Japanese lain-open patent publication Nos. (Tokukaihei) 6-167708 and 2-236523, and Japan Display ""89, p. 192.
A polarizer disposed on the incident side transmits only linearly polarized components in one direction among linearly polarized components of incident light and outgoing light, and absorbs linearly polarized components in the directions perpendicular to the transmissive directions. The incident light which has been transmitted through the polarizer is changed in its polarization state by an optical phase difference compensation plate such as a {fraction (xcex/4)} waveplate and then incident on a liquid crystal layer (in the case of Japanese laid-open patent publication No. (Tokukaihei) 6-167708), or incident on the liquid crystal layer without a change in the polarization state (in the cases of Japanese laid-open patent publication No. (Tokukaihei) 2-236523 and Japan Display ""89, p. 192). When the light incident on the liquid crystal layer passes through the liquid crystal layer, the polarization state thereof changes and the light reaches a reflector. The light which has reached the reflector passes through the liquid crystal layer and {fraction (xcex/4)} waveplate in reversed order to the order when it was incident, while changing in the polarization state, and reaches the polarizer again.
At this time, the final ratio of the polarized components in the transmitting direction of the polarizer determines the overall reflectivity of the liquid crystal layer. More specifically, the brightest display is obtained when the polarization state of the outgoing light just before passing through the polarizer is linear polarization in the transmitting direction of the polarizer, and the darkest display is obtained when the polarization is linear polarization in the absorbing direction.
The necessary and sufficient conditions for achieving these states with light which is normally incident on and outgoing from a liquid crystal display device are known as described below, but the detailed explanation thereof is omitted. In other words, the necessary and sufficient conditions are such that the polarization state on the reflector is linear polarization in any direction for the bright state, and the polarization state on the reflector is right- or left-handed circular polarization for the dark state. The above-mentioned conditions presume specular reflection without polarization scramble. In other words, with reflection which scrambles polarization, the brightness in the bright state is lowered, while the brightness in the dark state is increased, resulting in a degradation of the display contrast. Therefore, the reflection with polarization scramble is not suitable for the single polarizer structure aiming for a high contrast.
A reflective type liquid crystal display device in which one polarizer and a liquid crystal layer having a negative dielectric anisotropy and homeotropic alignment is disclosed. U.S. Pat. No. 4,701,028 (Clerc et al.) discloses a reflective type liquid crystal display device incorporating a combination of one polarizer, xc2xc waveplate, and homeotropically aligned liquid crystal cell. Moreover, Japanese laid-open patent publication No. (Tokukaihei) 6-337421 discloses a reflective type liquid crystal display device incorporating a combination of one polarizer, xc2xc waveplate, and hybrid aligned liquid crystal cell. Furthermore, a reflective type liquid crystal display device incorporating a combination of one polarizer, xc2xc waveplate, and homeotropically aligned liquid crystal cell is disclosed in Euro Display ""96, p. 464.
These devices are liquid crystal display devices which use a xc2xc waveplate, realize a dark state by making the retardation of the liquid crystal layer substantially zero in the absence of applied voltage and maintaining the polarization state, and produce a bright state by applying a voltage so that the retardation of liquid crystal layer has a finite value, i.e., liquid crystal display devices of a so-called normally black mode in which switching is executed using the retardation.
On the other hand, a projection type liquid crystal display device has a mechanism for enlarging and projecting a display image produced by liquid crystal elements, and provide a large-area display by a small device compared with the size of the display image. Therefore, the projection type liquid crystal display device has been used widely in practical image display devices such as large display devices and data projectors.
In addition, a head-mount display is a small device, and has such characteristics that it effectively provides a large display screen to a viewer, occupies the field of view of the viewer because it is fixed at the head, and provides independent display information to right and left eyes. The application of the head-mount display to virtual reality techniques, high quality image displays, three-dimensional picture reproduction-use displays, etc. in future is expected because of the above-mentioned merits.
Among these projection type liquid crystal display device and head-mount display, a reflective type liquid crystal display device has an advantage that it enables the production of a device with a multi-functional driving substrate by fabricating the liquid crystal element and peripheral circuits into the same device and extracting the light incident on the liquid crystal element from the illuminated surface of the device. In other words, the above-mentioned reflective type liquid crystal display device has an advantage that the non-light-transmitting substrate such as silicon wafer is usable, and an advantage that active elements for driving the liquid crystal layer and wiring can be designed without deteriorating the utilization efficiency of light even when the liquid crystal display element is designed in a small size.
Alternatively, it is possible to employ a technique such as a so-called liquid crystal light valve. With the use of the liquid crystal light valve, display information is written by illuminating light from a side opposite to the light projection side of the substrates holding the liquid crystal element therebetween. With this structure, the resistance of a photoconductive layer is changed, the voltage is allocated with respect to the liquid crystal layer to which a voltage has been applied during the application of the voltage to the photoconductive layer, and the strength of the projected light is varied according to the writing light. It is thus possible to apply the above-mentioned reflective type liquid crystal display to the projection type devices. In particular, the efficiency of light is important because it determines the overall brightness of the device.
Besides, since there is a possibility that ambient lighting environments in observing the display of such a projection type liquid crystal display device or head-mount display are very dark, a high quality display is required. Hence, in order to achieve a high contrast display by realizing a good black display in such lighting environments, high light blocking properties are required for the black display.
Moreover, Japanese laid-open patent publication No. (Tokukaihei) 8-62564 discloses a technique as an example of a liquid crystal projection type liquid crystal display which is fabricated using a polarizing beam splitter and achieves a high contrast display with the use of an optical phase difference compensation plate. According to the structure disclosed in this publication, in order to achieve a high contrast display, an optical element (birefringence element) for producing a phase difference is used so as to compensate for the phase difference of the liquid crystal layer in the dark state.
In a structure in which a homogeneous liquid crystal cell is used in a single polarizer liquid crystal display device of the above-mentioned prior art, when a bright state is provided by the application of a voltage or when a bright state is provided by an alignment state in a homeotropic liquid crystal cell in which the birefringence of the liquid crystal layer substantially disappears in the absence of applied voltage, it is preferred to satisfy the following. Specifically, it is preferred that a polarization state after the outgoing of the light from the optical phase difference compensation plate to liquid crystal layer is made linearly polarized light by a combination of the polarizer of the liquid crystal display device achieving a good bright state in a wide wavelength range and the optical phase difference compensation plate. However, when the linearly polarized light has a fixed plane of vibration in every wavelength range, the function of the liquid crystal layer of compensating the differences in the functions of the polarization states in the respective wavelengths is not achieved.
If the above-mentioned two conditions, i.e., light of each wavelength is linearly polarized light and a polarization state where the direction of the vibration plane varies depending on the wavelength, are satisfied, the phase plate can be used as an optical phase difference compensation plate which can serve as a color compensation plate aiming for the optical compensating function of the liquid crystal layer.
According to the one disclosed in the above-mentioned Japanese laid-open patent publication No. (Tokukaihei) 5-100114, a method for obtaining a xc2xd wavelength condition for a wide wavelength range is provided. However, polarized lights of different wavelengths have vibration planes of the same direction, and the resultant polarization state differs only in the direction from the polarization state immediately after the passage through the polarizer. In other words, the polarization direction does not vary depending on the wavelength.
Moreover, in the descriptions of the above publication, it is also disclosed that lights in a wide wavelength range is made circularly polarized lights by a method of providing a xc2xc wavelength condition for a wide wavelength range. However, this publication does not disclose a method of providing linearly polarized light of a direction varying according to the wavelength.
In a liquid crystal display device disclosed in the above-mentioned Japanese laid-open patent publication No. (Tokukaisho) 55-48733, it is necessary to provide a xc2xc waveplate between the liquid crystal layer and the reflector. Therefore, it is difficult in theory to form a reflective film on the inner side of the liquid crystal cell. Thus, this liquid crystal display device is not suitable for a high resolution, high definition display.
Besides, in a reflective homogeneous structure as disclosed in the above-mentioned Japanese laid-open patent publication No. (Tokukaihei) 6-167708, coloration occurs because of the wavelength dispersion between the liquid crystal cell and optical phase difference compensation plate. In such a conventional structure, the dark state tends to color. Thus, there is a problem that a black-and-white display can not be achieved.
Similarly, in the homeotropic structure as disclosed in the above-mentioned Japanese laid-open patent publication No. (Tokukaihei) 6-337421 and Euro Display ""96, p. 464, the liquid crystal is aligned parallel without being twisted during the application of a voltage. Hence, the dark state tends to color because of the effect of the wavelength dispersion between the liquid crystal cell and optical phase difference compensation plate. Consequently, there is a problem that a good black-and-white display cannot be achieved. Moreover, when the viewer sees the display in the absence of applied voltage from a directly front direction of the substrate (i.e., from a direction normal to the substrate), it is possible to achieve a good dark display because of zero retardation. However, when the viewer sees the display from a direction tilted from the direction normal to the substrate, retardation occurs. Therefore, the viewing angle characteristics related to the tilt angle of the display are very bad, and a good dark display is not achieved.
On the other hand, the structures as disclosed in Japanese laid-open patent publication No. (Tokukaihei) 2-236523 and Japan Display ""89, p. 192 have higher reflectivity in the bright state compared with a structure using two polarizers. However, since the transmissivity in the dark state depends greatly on the wavelength, a good black display is not achieved. Additionally, And that is the product of a difference of refractive indices (xcex94n) of the liquid crystal layer and a thickness (d) of the liquid crystal layer needs to have a very small value of around 200 nm. When And has such a value, if a liquid crystal panel is fabricated using a general liquid crystal material, i.e., a liquid crystal material having An of 0.065 or more, the cell gap in the liquid crystal layer has a very small value of substantially 3 xcexcm. Thus, it is difficult to manufacture the liquid crystal panel.
Furthermore, the structure disclosed in the above-mentioned Japanese laid-open patent publication No. (Tokukaihei) 8-62564 using a polarizing beam splitter and a birefringence element was designed to improve the contrast. However, since the brightness was not improved, the efficiency was not increased. Moreover, according to the descriptions in an embodiment disclosed in this publication, although the contrast was improved, the brightness was lowered and therefore the efficiency was rather worsened. According to an example described in the embodiment of this publication, in order to improve the projection efficiency, the liquid crystal alignment which is oriented homeotropically when a low voltage is applied is arranged to be a tilted alignment state by increasing the applied voltage so as to increase the brightness in this alignment state. However, in order to maintain the contrast, there is a requirement that an optical element used for this arrangement does not increase the brightness in the dark state. However, an optical element having such a function and the liquid crystal display device incorporating the optical element have never been disclosed.
In order to solve the above problems, i.e., the problems associated with a single polarizer liquid crystal display device capable of providing high resolution displays, or the problems associated with a reflected light projection type liquid crystal display device and head-mount display, objects of the present invention are to improve the function of a laminated phase plate, provide a laminated phase plate capable of achieving a reflective type liquid crystal display device with an excellent visibility or a projection-type liquid crystal display device with a high efficiency, and a liquid crystal display device incorporating the laminated phase plate.
In order to achieve the above objects, a laminated phase plate of the present invention is formed by laminating a first optical phase difference compensation plate and a second optical phase difference compensation plate. The first optical phase difference compensation plate has a retardation between 100 nm and 180 nm for transmitted light of a wavelength of 550 nm in a direction normal to the first optical phase difference compensation plate. The second optical phase difference compensation plate has a retardation between 200 nm and 360 nm for transmitted light of a wavelength of 550 nm in a direction normal to the second optical phase difference compensation plate. The first and second optical phase difference compensation plates are arranged so that, when linearly polarized light which is visible light and has a fixed plane of vibration is incident on the second optical phase difference compensation plate, the value of |xcex81xe2x88x922xc3x97xcex82|, wherein xcex81 is an angle between a direction perpendicular to the direction of vibration of the linearly polarized light or the direction of vibration of the linearly polarized light incident on the set off plates and a direction of a slow axis of the first optical phase difference compensation plate, and xcex82 is an angle between the direction perpendicular to the direction of vibration of the linearly polarized light or the direction of vibration of the linearly polarized light incident on the set off plates and a direction of a slow axis of the second optical phase difference compensation plate, is within a range between 80 degrees and 100 degrees.
The above invention was implemented by finding that, in a combination of an optical phase difference compensation plate which produces a phase difference of a xc2xd wavelength and an optical phase difference compensation plate which produces a phase difference of a xc2xc wavelength, it is important that the directions of the optical phase difference compensation plates are set to specific directions.
With the use of the laminated phase plate of the present invention, it is possible to achieve a liquid crystal display device in which a reflecting film formed surface of a reflector is located adjacent to a liquid crystal layer, and to provide a good dark state. Therefore, a reflective type liquid crystal display device capable of providing a high contrast, high definition display of a moving picture without parallax can be obtained. Moreover, if the laminated phase plate of the present invention is adopted into a liquid crystal display device for projecting reflected light or into a head-mount display, the projection efficiency can be improved.
In addition, in order to achieve the above object, a liquid crystal display device of the present invention includes a first substrate, a second substrate having light transmitting properties, a liquid crystal layer which is made of a liquid crystal compound containing liquid crystal and disposed between the first and second substrates, the laminated phase plate of claim 1 disposed on a display side of the second substrate, polarizing means, disposed on the second optical phase difference compensation plate side of the laminated phase plate, for causing linearly polarized light which is visible light and has a fixed plane of vibration to be incident on the second optical phase difference compensation plate, and light reflecting means, when the linearly polarized light which is visible light and has a fixed plane of vibration is caused to be incident on the second optical phase difference compensation plate by the polarizing means, for reflecting at least a part of the light which has transmitted through the second optical phase difference compensation plate, first optical phase difference compensation plate, second substrate and liquid crystal layer and gone out of the liquid crystal layer.
The above-mentioned invention was implemented by finding a structure of a liquid crystal display device which uses the laminated phase plate of the present invention most effectively for a display when the liquid crystal display device is constructed with the use of the laminated phase plate of the present invention.
The liquid crystal display device of the present invention achieves a reflective type liquid crystal display device with a high reflectivity and high contrast. Besides, the reflective film formed surface of the reflector can be located on the liquid crystal layer side of a transparent substrate, and thus a good dark state can be achieved. It is therefore possible to provide a high contrast, high definition display of a moving picture without parallax. Additionally, when a polarizing beam splitter is used for a liquid crystal display device having a layer of liquid crystal homeotropically aligned, an especially excellent contrast characteristic is obtained.
Moreover, when a color filter which has been adjusted for high brightness is used in a liquid crystal display device of the present invention, it is possible to achieve a reflective type color liquid crystal display device that provides high display quality with good color reproduction characteristics.
Furthermore, another invention is a liquid crystal display device (liquid crystal display device {circle around (1)}) which is based on the liquid crystal display device of the present invention, and in which the polarizing means is formed by a polarizer.
According to the liquid crystal display device {circle around (1)}, it is possible to achieve a direct viewing type liquid crystal display device which can most effectively use the laminated phase plate of the present invention. In other words, according to the liquid crystal display device {circle around (1)}, it is possible to provide a liquid crystal display device which achieves a good black display and good brightness with the laminated phase plate, and exhibits a good display characteristic that does not deteriorate the brightness.
Still another invention is a liquid crystal display device (liquid crystal display device {circle around (2)}) which is based on the liquid crystal display device of the present invention or the liquid crystal display device {circle around (1)}, and in which the liquid crystal compound has a positive dielectric anisotropy, the twist angle of the liquid crystal between the first and second substrates is between 60 degrees and 100 degrees, and the product of a difference of refractive indices of the liquid crystal of the liquid crystal layer and the thickness of the liquid crystal layer is between 150 nm and 330 nm.
According to the liquid crystal display device {circle around (2)}, it is possible to optimize the liquid crystal display device of the present invention or liquid crystal display device {circle around (1)}. In other words, according to the liquid crystal display device {circle around (2)}, it is possible to ensure sufficiently low reflectivity in a dark state for a visible wavelength range, and provide a liquid crystal display device which can be manufactured easily at a high yield.
Yet another invention is a liquid crystal display device {circle around (3)} which is based on any one of the liquid crystal display device of the present invention and liquid crystal display devices {circle around (1)} and {circle around (2)}, and in which the light reflecting means is a light reflecting film which is made of a conductive material, placed on the liquid crystal layer side of the first substrate, and has a surface with smoothly and continuously changing undulations.
In the direct viewing type liquid crystal display device, when the bright state is a white state rather than a mirror reflection, it is necessary to perform a diffuse reflection. According to the liquid crystal display device of the present invention, especially a liquid crystal display device with excellent display quality can be realized by the use of a reflector having smooth undulations.
More specifically, the liquid crystal display device {circle around (3)} was implemented by finding a structure of the light reflecting means, which is particularly suitable for the liquid crystal display device of the present invention. According to the liquid crystal display device {circle around (3)}, since the light reflecting film having undulations is provided, it is possible to prevent the reflection by the light reflecting means from becoming a mirror reflection. Consequently, it is possible to prevent the image in the surroundings of the device, such as the face of the viewer, from being reflected in the display surface of the liquid crystal display device, thereby realizing an excellent white display. Moreover, since no element having a scattering effect is disposed in front of the liquid crystal display device, it is possible to achieve an excellent black display. Accordingly, a liquid crystal display device with a high contrast ratio can be realized.
Besides, according to the liquid crystal display device {circle around (3)}, since the light reflecting film is formed by a conductive material, it also performs a function of an electrode for applying a voltage to the liquid crystal layer with a transparent electrode formed on the second substrate.
In order to achieve the liquid crystal display device {circle around (3)}, a plurality of protruding portions are formed on the liquid crystal layer side of the first substrate so that undulations are formed by the protruding portions and the first substrate, a planerization film for smoothing the surface of the undulations is formed on the protruding portions, and the light reflecting film is formed on the planerization film.
Yet another invention is a liquid crustal display device (liquid crystal display device {circle around (4)}) which is based on the liquid crystal display device {circle around (3)}, and in which a surface having the undulations of the light reflecting film has anisotropic properties that depend on the direction in the plane of the first substrate.
According to the liquid crystal display device {circle around (4)}, it is possible to further improve the reflection brightness of the reflecting type liquid crystal display device.
The liquid crystal display device {circle around (4)} can be realized by changing the average interval of the undulations of the undulating surface of the light reflecting film according to the direction in the plane of the first substrate.
More specifically, the liquid crystal display device {circle around (4)} includes a plurality of protruding portions and a planerization film between the light reflecting film and the first substrate as described above, and the protruding portions when seen from a direction normal to the first substrate have elliptical shapes whose longer axes are oriented in the same direction.
Still another invention is a liquid crystal display device (liquid crystal display device {circle around (5)}) which is based on any one of the liquid crystal display device of the present invention and liquid crystal display devices {circle around (1)} to {circle around (4)}, and in which the liquid crystal layer has a liquid crystal whose alignment direction varies according to an applied voltage, and dispersed polymer which has optical anisotropy and an alignment direction that does not vary according to the applied voltage.
In the liquid crystal display device {circle around (5)}, the liquid crystal and polymer are dispersed in the layer of the aligned liquid crystal, and the polymer has an alignment direction similar to that of liquid crystal molecules in the absence of applied voltage and optical anisotropy by itself. Accordingly, in the absence of applied voltage, the refractive index of the liquid crystal compound and that of the polymer are the same, and thus scattering does not occur. On the other hand, when a voltage is applied, the refractive index of the liquid crystal compound and that of the polymer differ from each other, and scattering occurs. Therefore, even with the use of a reflective film exhibiting a mirror surface, it is possible to provide a white display without mirror reflection in a direction other than the specular reflection, thereby achieving an extremely high contrast ratio.
In addition, still another invention is a liquid crystal display device (liquid crystal display device {circle around (6)}) which is based on the liquid crystal display device of the present invention, and in which the polarizing means is formed by a polarizing beam splitter.
The liquid crystal display device {circle around (6)} was implemented by finding that when a polarizing beam splitter was used as the polarizing means in a projection type or head-mount type liquid crystal display device with reflected light, the brightness in the dark state was not increased with the use of the optical phase difference compensation plate of the present invention.
According to the liquid crystal display device {circle around (6)}, it is possible to realize a projection type or head-mount type liquid crystal display device that maintains a high contrast ratio.
Furthermore, yet another invention is a liquid crystal display device (liquid crystal display device {circle around (7)}) which is based on the liquid crystal display device {circle around (6)}, and in which the liquid crystal compound has a positive dielectric anisotropy, the twist angle of the liquid crystal between the first and second substrates is within a range of from 60 degrees to 100 degrees, and the product of the difference of refractive indices of the liquid crystal and the thickness of the liquid crystal is between 150 nm and 330 nm.
In the liquid crystal display device of the present invention, the alignment direction of the liquid crystal layer needs to efficiently orient the linearly polarized light whose plane of vibration varies according to a wavelength, produced by the laminated phase plate of the present invention, in a transmitting direction of the polarizing beam splitter.
The liquid crystal display device {circle around (7)} includes the liquid crystal layer which is capable of increasing the efficiency when the polarizing beam splitter is used and optimized so as to provide a structure satisfying the above-mentioned condition.
Additionally, yet another invention is a liquid crystal display device (liquid crystal display device {circle around (8)}) which is based on the liquid crystal display device {circle around (6)}, and in which the liquid crystal compound has a negative dielectric anisotropy, and the liquid crystal of the liquid crystal layer is aligned in a direction perpendicular to the first and second substrates in the absence of applied voltage.
According to the liquid crystal display device {circle around (8)}, it is possible to provide a display in a normally white mode and achieve a bright display.
Furthermore, yet another invention is a liquid crystal display device (liquid crystal display device {circle around (9)}) which is based on the liquid crystal display device {circle around (8)}, and in which, when the natural pitch of the liquid crystal is denoted by p and the liquid crystal layer thickness is denoted by d, the value of |d/p| is larger than 0 but smaller than 0.5 and the product of the birefringence of the liquid crystal of the liquid crystal layer and the thickness of the liquid crystal layer is between 200 nm and 500 nm.
As a different structure from the liquid crystal display device {circle around (7)}, the liquid crystal display device {circle around (9)} is constructed to have the liquid crystal layer which is capable of increasing the efficiency when the polarizing beam splitter is used and optimized by the liquid crystal alignment of the liquid crystal display device of the present invention.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.

Laminated phase plate and liquid crystal display comprising the laminated phase plate


A method and an apparatus for monitoring and controlling the quality of the galvannealed coating of steel strip immediately following the galvannealing step, wherein the hot galvanized coating of the steel strip produced by hot dipping is converted into FeZn phases by diffusion reactions through a thermal treatment in an annealing furnace at temperatures above the melting point of zinc. The measurement value used for the quality of the galvannealed coating of the steel strip is the visual appearance of the galvannealed coating recorded by a visual recording device in the form of measurement signals as the quality measurement value, wherein the measurement signals are processed by measurement technology and the resulting measurement values are used after conversion into control variables for the direct control of the annealing furnace.

1. Field of the Invention
The present invention relates to a method and an apparatus for monitoring and controlling the quality of the galvannealed coating of steel strip immediately following the galvannealing step, wherein the hot galvanized coating of the steel strip produced by hot dipping is converted into FeZn phases by diffusion reactions through a thermal treatment in an annealing furnace at temperatures above the melting point of zinc.
2. Description of the Related Art
In order to improve the corrosion protection, the protection against wear, the surface hardness or the sliding behavior of metals, but also for reasons of a better appearance, it is known in the art to provide the metals with a coating with another metal, for example, to provide iron with a coating of zinc or chromium.
Various known methods have been found for applying the coating. They are:
Galvanic coatings, wherein the metal coating is applied in suitable baths containing acids or aqueous solutions by electrolysis of the metal immersed in the baths. When this method is used, coating thicknesses of up to about 10 .mu.m are achieved; PA1 Hot dip coatings, wherein the coatings are produced by immersing the metal to be coated in baths of liquid molten metal. In this method, a thin alloy layer is formed as a result of reactions between the metal atoms of the liquid coating metal and the atoms of the base metal, wherein a layer of pure coating metal is then placed on the alloy layer. The coating layer thicknesses achieved by this method are significantly higher than those achieved by galvanizing and are, for example, in the case of galvanizing iron (hot galvanizing) 4-50 .mu.m; an improvement of the hot dip coatings can be achieved by PA1 Galvannealing, wherein the term galvannealing is coined by combining the words galvanizing and annealing.
In the case of galvannealing, the steel strip which emerges from the molten metal bath and is now hot galvanized is thermally aftertreated by annealing at temperatures above the melting point of zinc. During this annealing step, diffusion processes take place which also penetrate through the upper layer composed of pure coating metal, i.e., zinc, so that different FeZn phases are formed.
When the galvannealing process is carried out in an optimum manner, the coating contains about 10-12% Fe. Higher Fe contents of greater than 12% Fe lead to an unfavorable deformation behavior of the steel strip, wherein increased powdering occurs during a later deformation.
In the case of lower Fe contents of less than 9% Fe, the coating is not yet completely alloyed through and residual zinc remains at the surface of the coating. This leads to an undesirable non-uniform appearance with inhomogeneous product properties.
In order to obtain a galvannealed coating which is reacted through in an optimum manner, the thermal treatment must be controlled with respect to the duration of the treatment and with respect to the temperature level to values which are adjusted to the layer thickness. Possible control variables for the duration of the treatment are the length of the annealing zone of the annealing furnace and the speed of the steel strip, and a possible control variable for the temperature is the temperature of the annealing furnace.
At the present time, monitoring and controlling the quality of the galvannealed coating is carried out on a large technical scale in such a way that the temperature of the steel strip above the galvannealing furnace is used as the parameter for the quality of the coating. However, this type of measurement, which is carried out without contact by means of pyrometers, has the problem that a change of the emission behavior of the strip surface at the moment of complete alloying of the coating and also with continuing formation of the alloy in the galvannealed state takes place. There is also the danger that an indicated temperature difference is not the result of an actual difference, but is caused by a changed emission. Consequently, a properly functioning control based on this measured temperature cannot be carried out satisfactorily.
Another disadvantage of the temperature measurement is the fact that the ideal temperature for reaching the desired galvannealed state depends on the reaction behavior of the steel, on the bearing weight, on the aluminum content in the zinc bath and on the temperatures during galvanizing. The galvannealing temperature mentioned above constitutes only an indirect measurement and must be considered in relation to the material used and the galvanizing conditions. The statement of an optimum galvannealed temperature can only always refer to a specific material and a specific combination of the galvanizing parameters which have an influence on the galvanizing process.
Another possibility for determining the quality of the galvannealed coating by measurement technology in order to carry out a control is the combination of temperature measurement and the Fe measurement at the cold measuring location. A disadvantage is the position of the measuring location which may be up to 100 m behind the galvannealing furnace and another disadvantage is the unsatisfactory accuracy of the iron measuring device. Also, it is not possible to recognize differences in the alloying condition over the strip width.

Method and apparatus for monitoring and controlling the quality of a galvannealed coating of steel strip


A fluid dispenser is disclosed for dispensing a fluid from a pouch having a discharge passage that extends along a tortuous path. The dispenser has a dispenser station and dispenser mechanism in the dispenser station. In one aspect the dispenser mechanism comprises a backstop on one side of the dispenser path and a cam operated cylindrical roller confronting the backstop located on the other side of the dispenser path. The roller is attached to a roller bracket which is pivotally attached to the interior of a hollow pushbutton. The pushbutton is mounted in an opening in the dispenser front cover. Springs are attached to the bracket and the front cover which maintain the roller against the flexible dispenser compartment of the pouch. Depressing the pushbutton forces the roller to trap the upper portion of the pouch flexible dispenser compartment between the roller and backstop to initially seal the dispenser compartment at its upper end and further pushbutton action forces the roller down the dispenser compartment thereby causing expulsion of the fluid trapped in the dispenser compartment.

This invention relates to improved fluid to dispensers of the type used to dispense liquid soap from a flexible pouch having a tortuous discharge passageway. An example of a pouch of this nature is disclosed in U.S. Pat. No. 4,491,245.
Fluid dispensers for dispensing small quantities of liquid soap from a pouch are well known. U.S. Pat. Nos. 4,463,876 and 4,564,127 are directed to typical fluid dispensers which include upper and lower jaws which can be manipulated to sequentially open and close to meter a predetermined quantity of fluid from the container. Difficulty has been experienced with this type of container in obtaining a tight seal between both upper and lower jaws.
Other dispensers use hard swash plates or cams having hard, curved surfaces to compress a portion of the pouch for expelling liquid therefrom. A drawback to such arrangements are that the swash plates or cams do not ride smoothly down the pouch since the surfaces thereof are hard with the result that the cam or swash plate jiggles side-to-side causing uneven pressure across the discharge portion of the pouch. Another drawback with current dispensers employing flexible dispenser pouches is that the pouches are designed to be hung from pegs or suspended in the dispenser housing. This necessitates wasting time aligning the dispenser pegs with holes in the pouch. Further, at present the only indication that a fluid pouch is nearly empty is when a reduced volume of fluid is being discharged from the pouch.
Accordingly, it would be advantageous to provide a fluid dispenser for dispensing liquids such as soap detergents, foodstuffs and the like which provides smooth fluid expulsion and which is provided with an indicator for indicating that the pouch is nearing empty.

Dispenser having roller for dispensing fluid from a collapsible bag


A method includes storing data in a memory, which includes multiple strings of analog memory cells arranged in a three-dimensional (3-D) configuration having a first dimension associated with bit lines, a second dimension associated with word lines and a third dimension associated with sections, such that each string is associated with a respective bit line and a respective section and includes multiple memory cells that are connected to the respective word lines. For a group of the strings, respective values of a property of the strings in the group are evaluated. Source-side voltages are calculated for the respective strings in the group, depending on the respective values of the property, and respective source-sides of the strings in the group are biased with the corresponding source-side voltages. A memory operation is performed on the strings in the group while the strings are biased with the respective source-side voltages.

Various types of three-dimensional (3-D) non-volatile memory devices, and methods for programming such devices, are known in the art. For example, U.S. Patent Application Publication 2012/0069657, whose disclosure is incorporated herein by reference, describes a memory device that includes a memory cell array, in some embodiments a three-dimensional Flash memory, a self interleaver configured to interleave and load data on the fly into a buffer circuit using an interleaving scheme, and a control logic configured to control programming of the interleaved data in the memory cell array.
U.S. Patent Application Publication 2012/0069664, whose disclosure is incorporated herein by reference, describes a Flash memory system and a word line interleaving method thereof. The Flash memory system includes a memory cell array, such as a three-dimensional array, and word line interleaving logic. The memory cell array is connected to a plurality of word lines. The word line (WL) interleaving logic performs an interleaving operation on WL data corresponding to at least two different word lines and programs data, including the interleaved data, to the memory cell array.
U.S. Patent Application Publication 2013/0028027, whose disclosure is incorporated herein by reference, describes a 3-D semiconductor memory device including a plurality of memory cell strings, includes a substrate and a channel that extends from the substrate. Memory cells may be disposed in layers in which the diameter of the channel varies. A programming verification operation may be carried out in a sequence whereby memory cells more likely to fail in programming are verified before attempting to verify memory cells that are less likely to fail programming. In an exemplary embodiment, the verification operation is performed on a memory cell disposed in a layer associated with a larger-diameter channel before performing the verification on a memory cell disposed in a layer associated with a smaller-diameter channel.
U.S. Pat. No. 8,036,043, whose disclosure is incorporated herein by reference, describes a non-volatile semiconductor memory device including a vertical array structure comprised of bit lines and source lines arranged in the same direction as the bit lines. Memory cell strings are vertically formed between each pair of the bit lines and source lines. Multiple strings of memory cells can be stacked in the vertical direction, and adjacent memory cell strings may share bit line or source line.
U.S. Pat. No. 8,203,882, whose disclosure is incorporated herein by reference, describes a non-volatile semiconductor storage device. When a data erase operation is performed in one memory cell block, a first voltage is applied to one source line selected from m source lines in the one memory cell block. A second voltage equal to a voltage of the source lines before the data erase operation begins is applied to the other source lines. Then, after a certain time delay from application of the first voltage, a third voltage smaller than the first voltage is applied to a third conductive layer of a source-side selection transistor connected to a selected source line. A fourth voltage is applied to one of first conductive layers connected to one of the memory transistor to be erased. The other first conductive layers are brought into a floating state.
U.S. Pat. No. 8,004,885, whose disclosure is incorporated herein by reference, describes a driving method of a three-dimensional memory device having a plurality of layers. One of the layers is selected. A well of the selected layer is biased with a first well voltage. A word line voltage is applied to a selected word line of the selected layer. A well of an unselected layer is biased with a second well voltage higher than the first well voltage.

Enhanced data storage in 3-D memory using string-specific source-side biasing


An intelligent intersection control system features an internal controller that receives digital messages containing detailed information items concerning, for example, the direction, speed, length and identity of a train. The controller generates appropriate commands that coordinate the functions of crossing safety devices. A controller is capable of receiving and using much more detailed train information than is possible with conventional warning systems. Railroad crossing warning features are capable of responding more flexibly to this more detailed train information. The controller also continuously adjusts the activation state for safety devices associated with the crossing. In particular embodiments, the control system provides and displays crossing status information including the amount of time remaining until a crossing is cleared of train traffic, the approach of a second train during blocking of the crossing by a first train, or a suggested alternate route for waiting road vehicles. The controller may also be used to actuate numerous standard crossing warning features, including crossing blocking arms, flashing lights, warning chimes and warning horns.

1. Field of the Invention
The present invention relates generally to systems and methods for the control of railroad crossing signals and devices. In other aspects, the invention relates to systems and methods for providing train location and travel information to remote locations and for tracking train traffic generally.
2. Description of the Related Art
Rail crossings, intersections where a railroad track crosses a roadway, have long presented a significant danger for vehicular traffic. Each year many car/train accidents occur at these locations.
There is a widespread belief that many such accidents result, directly or indirectly, from an inherent unreliability in the present "island circuit" arrangement used to actuate rail crossing safety devices. The island circuit system is an electromechanical system used to operate flashing crossing lights and crossing blocking arms. Functioning of this system is based upon the movement of a train into an "island circuit" which is located a short, predetermined distance around (i.e., on either side of) a railroad crossing. As the train passes over the island circuit, an electrical signal is generated indicative of the train's location within the "island" bounded by the predetermined distance. The signal is then transmitted along the track to a relay located near the railroad crossing. Upon receipt of the signal, the relay actuates flashing lights and lowers crossing blocking arms.
Unreliability in the island circuit system can cause rail crossing safety devices to be activated in error or even to fail to activate when necessary. Inadvertent activation occurs when salt, mud, water or other contaminants cause the island circuit system to shunt. It is believed by some that numerous such false alarms may lead to a conditioned disregard by some motorists of the crossing safety devices. On the other hand, the crossing devices can fail to activate due to contaminants, such as grease, that keep the train from completing the circuit. As a result, the signal indicating the presence of the train is not transmitted to the crossing.
Further, the warning time provided by island circuit systems is variable. Usually, the island circuit is configured so that safety devices adapted to govern vehicular traffic across a railway are activated when an approaching train is a certain distance from the rail crossing. These rail crossing safety devices include flashing lights and chimes as well as rail crossing blocking members or arms. Given the average speed of trains, this amount of time is on the order of twenty to thirty seconds warning before the train reaches the crossing and the crossing arms block the crossing. In actuality, however, trains may be either faster or slower than the planned average. Thus, the actual warning time varies based upon the actual speed of individual trains.
Some "constant warning time" systems are known which provide a predetermined amount of warning time regardless of the speed of an approaching train. These systems are complex electromechanical arrangements that measure the electrical resistance associated with passing trains and use the measurement to approximate the speed of the train. Variations in the train's speed are then compensated for so that, for a faster train, the safety devices at the crossing are activated earlier; for a slower train, the safety devices are activated slightly later.
A major drawback to both constant warning time systems and conventional island circuit systems is the expense associated with installing and maintaining these systems. Further, these arrangements provide only limited information to vehicle operators concerning the approaching train. Specifically, only the fact that a train is approaching the crossing is indicated.
A rail crossing collision avoidance system concept is discussed in U.S. Pat. No. 5,699,986 issued to Welk. This concept provides a general method whereby road vehicles in the vicinity of a rail crossing are informed of a train approaching the crossing. The patent discusses the use of data obtained from global positioning system (GPS) devices located on trains and/or at railroad crossings to provide such information. A processor/transmitter controller is located either on the train or at the train crossing itself to perform the calculations to determine train arrival times. If it is determined that an alarm condition exists, an alarm signal is transmitted to individual road vehicles which are equipped to receive it.
Another GPS-based rail crossing warning system is discussed in U.S. Pat. No. 5,554,982 issued to Shirkey et al. According to this patent, a GPS receiver is installed on top of a train and used to obtain information concerning the train's speed and position. This information is then transmitted to a rail crossing-based transceiver. When the train's estimated time of arrival at the crossing is within a predetermined range, the transceiver transmits the boundary coordinates of a warning zone. A road vehicle-based receiver receives the warning zone signal and the crossing's position. The receiver then determines the road vehicle's position and speed and produces an alarm to the road vehicle's operator when the vehicle is inside the warning zone and its distance to the crossing is within another predetermined range, which is a function of the road vehicle's speed.
The systems discussed in Welk and Shirkey et al. contain a number of disadvantages. First, they are useful to determine the position of only a single train in relation to a single railroad crossing. Thus, the system is not useful for deriving arrival time and train speed information for a number of different trains. Also, it is not possible to use them to derive information concerning the identity of individual trains. Further, centralized control and communications are not possible.
A system based upon the concepts discussed in the Welk and Shirkey et al. patents would also be expensive and perhaps impractical since specially-made receivers are needed in each individual road vehicle in order for the system to be fully operational. Because maintenance and upkeep of these receivers would undoubtedly be left to the discretion of the owners and operators of the individual road vehicles, the system might become unreliable.
In addition, it will be appreciated that the Welk and Sharkey et al. patents discuss only general concepts and do not reveal the structural and functional details of a controller which is capable of receiving a message and, in response thereto, controlling the safety features of a railroad crossing.
The present invention addresses the problems inherent in the prior art.

Intelligent rail crossing control system and train tracking system


The invention provides immunotherapeutic and prophylactic bacteriophage viral-like particle (VLPs) which are useful in the treatment and prevention of Respiratory Syncytial Virus (RSV) infections and related disorders, including bronchiolitis and viral pneumonia. Related compositions (e.g. vaccines), nucleic acid constructs, and therapeutic methods are also provided. VLPs and related compositions of the invention induce high titer antibody responses against RSV. VLPs, VLP-containing compositions, and therapeutic methods of the invention induce an immunogenic response against RSV infection, confer immunity against RSV infection, protect against RSV infection, and reduce the likelihood of infection by RSV infection.

Respiratory Syncytial Virus (RSV) is a human pathogen that is the predominant cause of acute lower respiratory tract infection in children [reviewed by (27)]. In the United States, nearly all children are infected with RSV by the age of three. Symptoms range from severe pneumonia and bronchiolitis to milder infections. Because of its prevalence, RSV is a major cause of serious respiratory illness requiring hospitalization in children. Significant morbidity and mortality are also associated with RSV infection of the elderly.
The viral genome encodes two major structural glycoproteins that are exposed on the surface of RSV virions, G and F. G is believed to play a role in viral attachment to a cellular receptor. F promotes fusion of the viral and cell membranes, allowing entry of the viral genome into the target cell. Antibodies against either G or F can neutralize RSV infectivity (18). The G protein is highly genetically diverse amongst RSV strains, thus anti-G neutralizing antibodies are only neutralizing against viruses of one of the two antigenic groups of RSV (either A or B). In contrast, F is highly conserved and anti-F neutralizing antibodies can protect animal models from infection by both group-A and group-B viruses (26, 31).
There is no current vaccine for RSV infection. (In the 1960s a formalin-inactivated RSV vaccine candidate actually increased disease severity in vaccinated children.) Moreover, there are no useful therapeutics for treating RSV infection. However, Palivizumab, also known by its trade name Synagis, a monoclonal antibody that targets a neutralizing epitope in the F glycoprotein, has been used prophylactically to prevent RSV infection. Although Synagis is effective, it is very expensive and only is cost-effective for use in infants that are at extremely high risk for developing severe RSV infection. Because of its expense, it is only used in developed countries.
Virus-like Particle (VLP) Based Vaccines.
Virus-like particles (VLPs) make excellent vaccines. They are non-infectious, often easier to produce than actual viruses, and, because the regularity of their capsid structure presents viral epitopes as dense, highly repetitive arrays that strongly stimulate B cells, they are highly immunogenic. VLPs are comprised of one or more proteins arranged geometrically into dense, repetitive arrays. These structures are largely unique to microbial antigens, and the mammalian immune system has apparently evolved to respond vigorously to this arrangement of antigens. B cells specifically recognize and respond strongly to the ordered array of densely spaced repetitive elements characteristic of virus surfaces (1, 16). Highly repetitive antigens provoke oligomerization of the membrane-associated immunoglobulin (Ig) molecules that constitute the B cell receptor (BCR) (2). There is evidence that the Ig crosslinking mediated by multivalent antigens leads to the formation of highly stable BCR-signaling microdomains that are associated with increased signaling to the B cell (34). This signaling stimulates B cell proliferation, migration, and upregulation of both major histocompatibility complex (MHC) class II and the co-stimulatory molecules that permit subsequent interactions with T helper cells that are required to trigger IgG secretion, affinity maturation, and the generation of long-lived memory B cells (8). Consequently, multivalent antigens such as VLPs can activate B cells at much lower concentrations than monomeric antigens (3, 13, 14, 25). Hence, VLPs are innately immunogenic: they induce high titer and long lasting antibody responses at low doses, often without requiring adjuvants (19, 36).
VLPs as Flexible Platforms for Vaccine Development.
VLPs can be used as the basis for vaccines targeting the virus from which they were derived (the Hepatitis B virus vaccine and HPV vaccine are two clinically approved VLP vaccines, other VLP vaccines are in clinical trials). However, they also can be used as platforms to display practically any epitope in a highly immunogenic, multivalent format. Heterologous antigens displayed at high density on the surface of VLPs exhibit the same high immunogenicity as unmodified VLPs. VLPs derived from a variety of different viruses have been exploited in this manner to induce antibody responses against heterologous targets that are poorly immunogenic in their native contexts. Although the VLP platform strategy has typically been applied to target antigens derived from pathogens, VLP-display can effectively induce antibody responses against practically any antigen. One example is the vaccine for nicotine addiction (designed to assist smokers who are trying to quit) developed by a biotechnology company, Cytos Biotechnology. This vaccine consists of nicotine, conjugated at high copy number to the surface of VLPs derived from a bacteriophage. In phase II clinical trials, VLPs displaying nicotine were well-tolerated and induced strong nicotine-specific IgG responses in 100% of immunized subjects (12). Even self-antigens, which are normally subject to the mechanisms of B cell tolerance, are immunogenic when displayed at high density on the surface of VLPs. Vaccines have been developed against self-molecules involved in several different diseases, including amyloid-beta (Alzheimers (11, 21)), TNF-α (arthritis (9)), CCR5 (HIV infection (7, 10)), gastrin (cancer, unpublished data), IgE (allergy, unpublished data), and others. VLP-based vaccines developed by pharmaceutical companies targeting amyloid-beta and angiotensin II (hypertension) are currently being evaluated in clinical trials; positive results from the trial of vaccine targeting angiotensin II (as a vaccine for hypertension) were reported in the spring of 2008 (35).

Immunogenic respiratory syncytial virus glycoprotein-containing VLPs and related compositions, constructs, and therapeutic methods