A liquid crystal display apparatus of the present invention includes: a liquid crystal display device, the liquid crystal display device including: a pair of light transmissive substrates; a transparent electrode layer and an alignment film which are provided on one surface of each of the light transmissive substrates, the surface facing the other one of the light transmissive substrates; and a liquid crystal layer interposed between the pair of light transmissive substrates, wherein: the liquid crystal layer includes liquid crystal molecules; the liquid crystal molecules on a surface on each of the alignment films are pre-tilted in the same direction and by the same angle as those on a surface of the other one of the alignment films; and the liquid crystal layer has a homogeneous orientation; a pair of polarizers provided on respective sides of the liquid crystal display device; and at least one inclined phase plate including an index ellipsoid having three principal refractive indices na, nb and nc, wherein: the three principal refractive indices na, nb and nc of the index ellipsoid satisfy a relationship of na=nb greater than nc; each of the principal refractive indices na and nb is a principal refractive index along a direction in a surface of the inclined phase plate, and the principal refractive index nc is a principal refractive index along a direction normal to the surface of the inclined phase plate; the index ellipsoid is inclined by inclining the direction of the principal refractive index nc and the direction of one of the in-plane principal refractive indices na and nb with respect to each other about an axis extending along the direction of the other one of the in-plane principal refractive indices na and nb; the inclined phase plate is provided between the liquid crystal display device and at least one of the polarizers; and the inclined phase plate is arranged so that an inclination direction of the index ellipsoid as being projected onto the surface of one of the light transmissive substrates is generally parallel or antiparallel to an orientation direction of the liquid crystal molecules.

1. Field of the Invention
The present invention relates to a liquid crystal display apparatus and, more particularly, to a liquid crystal display apparatus which employs in combination a liquid crystal display device and a phase plate, thereby improving the response characteristics and the viewing angle characteristics of the display screen.
2. Description of the Related Art
A liquid crystal display device using a nematic liquid crystal display device has conventionally been used widely in number segment type display devices such as clocks and desktop calculators. In recent years, such liquid crystal display devices have also been used in word processors, notebook type personal computers, car liquid crystal TVs, and the like.
A liquid crystal display apparatus typically includes a light transmissive substrate on which electrode lines, and the like, are provided for turning pixels ON/OFF. For example, in an active matrix type liquid crystal display apparatus, active elements such as thin film transistors are provided on the substrate, along with the electrode lines, as switching means for selectively driving the pixel electrodes by which voltages are applied through the liquid crystal layer. In a color liquid crystal display apparatus, a color filter layer for providing colors, e.g., RGB, is provided on the substrate.
An appropriate liquid crystal display mode can be selected for use with each of such liquid crystal display devices according to the twist angle of the liquid crystal molecules. For example, an active drive type twisted nematic liquid crystal display mode (hereinafter, xe2x80x9cTN modexe2x80x9d) and a multiplex drive type super twisted nematic liquid crystal display mode (hereinafter, xe2x80x9cSTN modexe2x80x9d) are well known in the art.
In the TN mode, nematic liquid crystal molecules are oriented in a 90xc2x0 twist so as to guide light along the twist, thereby producing a display. The STN mode effectively utilizes the phenomenon that when the twist angle of the nematic liquid crystal molecules is increased to be greater than 90xc2x0, the transmission therethrough changes rapidly for voltages in the vicinity of the threshold voltage applied through the liquid crystal layer.
In the STN mode, the background of the display screen is colored in a unique color due to interference of colors because the STN mode utilizes the birefringence effect of a liquid crystal material. In order to solve such problems so as to produce a black and white display with the STN mode, it is believed to be effective to employ an optical compensator. Display modes employing an optical compensator can be generally classified into the double super twisted nematic phase compensation mode (hereinafter, xe2x80x9cDSTN modexe2x80x9d) and the film type phase compensation mode in which an optically anisotropic film is employed (hereinafter, xe2x80x9cfilm added modexe2x80x9d).
The DSTN mode employs a two-layer structure including a display liquid crystal cell in which the liquid crystal molecules are twisted in a certain direction and another liquid crystal cell in which the liquid crystal molecules are twisted in the opposite direction. The film added mode employs a structure in which an optically anisotropic film is provided. It is believed that the film added mode is advantageous in that it is light in weight and low in cost. Since the black and white display characteristics with the STN modes have been improved by the employment of such phase compensation methods, color STN liquid crystal display apparatuses have been realized in the art in which a color filter layer is provided in an STN mode display apparatus.
On the other hand, the TN modes can be generally classified into the normally black mode and the normally white mode. In the normally black mode, a pair of polarizers are arranged so that their polarization directions are parallel to each other, whereby a black display is produced in the absence of an ON voltage through the liquid crystal layer (i.e., in the OFF state). In the normally white mode, a pair of polarizers are arranged so that their polarization directions are orthogonal to each other, whereby a white display is produced in the OFF state. The normally white mode is advantageous in the terms of the display contrast, the color reproducibility, the viewing angle dependency of the display, etc.
However, a liquid crystal display apparatus of the above-described TN mode has a problem as follows. In a TN mode liquid crystal display apparatus, the liquid crystal molecules have a refractive index anisotropy xcex94n and the liquid crystal molecules are in an inclined orientation with respect to the upper and lower substrates. As a result, the viewing angle dependency may be substantial such that the contrast of the displayed image substantially varies depending upon the direction and the angle from which the display is viewed by the observer.
FIG. 34 schematically illustrates in a cross-sectional view the structure of a TN liquid crystal display device. In the state as shown, a gray-level voltage is being applied through the liquid crystal layer, whereby the liquid crystal molecules are slightly raised. With the TN liquid crystal display device in this state, linearly-polarized light travelling in the direction normal to the surfaces of the pair of substrates (the xe2x80x9cnormal directionxe2x80x9d) passes through the liquid crystal molecules at an angle which is different from the angle at which linearly-polarized light travelling in a direction inclined with respect to the normal direction passes through the liquid crystal molecules. Since the liquid crystal molecules have the refractive index anisotropy xcex94n, passage of the linearly-polarized light from the different directions produces normal light and abnormal light with a phase difference therebetween. Due to such a phase difference, the incident light is converted into elliptically-polarized light, thereby causing the viewing angle dependency.
Within a liquid crystal layer in an actual liquid crystal display device, liquid crystal molecules in the vicinity of the midpoint between the substrates have a tilt angle which is different from that of other liquid crystal molecules on or near the substrate, and the liquid crystal molecules have a 90xc2x0 twist between the substrates about the normal direction.
Thus, the linearly-polarized light passing through the liquid crystal layer is subject to various degrees of birefringent effect depending upon its direction and angle, thereby exhibiting a complicated viewing angle dependency.
This viewing angle dependency causes phenomena such as the following: the display screen is colored when the viewing angle is inclined from the direction normal to the screen toward the normal viewing direction, i.e., toward the lower side of the screen by a certain angle or more (hereinafter, the xe2x80x9ccoloring phenomenonxe2x80x9d); and the black and the white are reversed (hereinafter, the xe2x80x9cblack and white reversal phenomenonxe2x80x9d). When the viewing angle is inclined toward the counter-normal viewing direction, i.e., toward the upper side of the screen, the contrast is reduced rapidly.
The above-described liquid crystal display apparatus has another problem follows. The larger the display screen, the narrower is the viewing angle. When a large liquid crystal display screen is viewed by the observer from the normal direction within a short distance from the screen, the display color in an upper portion of the screen may be different from the display color in a lower portion of the screen due to an influence of the viewing angle dependency. This is because the observer being so close to the screen, although in the normal direction makes the situation substantially the same as that where a small display screen is viewed from an inclined direction.
In order to address the problems associated with the viewing angle dependency, it has been proposed in the art to insert a phase plate (a phase film) as an optionally anisotropic optical element between a liquid crystal display device and one of a pair of polarizers (see, for example, Japanese Laid-Open Publication No. 5-313159).
According to this method, a phase plate is provided on one side or on both sides of the liquid crystal layer having a refractive index anisotropy. Linearly-polarized light, which has passed through the liquid crystal layer having the refractive index anisotropy and thus have been converted into elliptically-polarized light, passes through the phase plate so as to compensate for the change in the phase difference between the normal light and the abnormal light occurring within the viewing angle, thereby re-converting the elliptically-polarized light into linearly-polarized light. Thus, the viewing angle dependency is improved.
However, even with the use of the phase plate, the reversal phenomenon in a normal viewing direction and the reduction in the contrast in a counter-normal viewing direction cannot sufficiently be improved at the same time.
In view of this, Japanese Laid-Open Publication No. 6-75116 proposes a method which employs a phase plate in which a principal refractive index direction of the index ellipsoid is inclined with respect to the direction normal to the surface of the phase plate. In this method, the following two types of phase plates are used.
One of the two types of phase plates is as follows. The direction of the minimum principal refractive index of the three principal refractive indices of the index ellipsoid is parallel to the surface of the phase plate. The direction of one of the remaining two principal refractive indices is inclined at angle xcex8 with respect to the surface of the phase plate, with the direction of the other principal refractive index being inclined at angle xcex8 with respect to the direction normal to the surface of the phase plate. The value of xcex8 satisfies the relationship of 20xc2x0xe2x89xa6xcex8xe2x89xa670xc2x0.
The other one of the two types of phase plates is as follows. The three principal refractive indices na, nb, nc of the index ellipsoid satisfy the relationship of na=nc greater than nb. The direction of the principal refractive index nb, which is parallel to the direction normal to the surface of the phase plate and is orthogonal to one of the in-plane principal refractive index nc (or na), is inclined clockwise or counterclockwise from its original direction about an axis along the direction of one of the in-plane principal refractive indices na (or nc).
The former of the above-described two types of phase plates may be either uniaxial or biaxial. A phase plate of the second type may be either a single phase plate or a combination of two such phase plates in which the direction of the principal refractive index nb of one phase plate is at an angle of 90xc2x0 with respect to the direction of the principal refractive index nb of the other phase plate.
In a liquid crystal display apparatus in which at least one phase plate is provided between the liquid crystal display device and the polarizer, as described above, the change in the contrast, the coloring phenomenon and the reversal phenomenon occurring in the displayed image depending upon the viewing angle can be improved to a certain degree.
However, both of the TN mode and the STN mode have a problem in that the response speed of the liquid crystal material is low. Typically, the response time is about 30 ms in the TN mode and about 100 ms in the STN mode. Normally, an image signal is updated with a frequency of 60 Hz, meaning that a new image is displayed for each frame period, i.e., for every 16.7 ms. Thus, with the liquid crystal mode with such a low response speed, the liquid crystal material cannot completely respond to an image signal within one frame period. In fact, existing liquid crystal display apparatuses have a ghost image problem in a motion picture display, which represents a significant reduction in the display quality.
A homogeneous orientation mode is well known in the art as a liquid crystal mode which has a shorter response time than those of the TN and STN modes. In this mode, the respective alignment films on two glass substrates have opposite and parallel (antiparallel) rubbing directions with respect to each other, and no chiral agent is added to the liquid crystal material. As a result, there is no twist of the liquid crystal molecules as those in the TN mode or the STN mode. It is believed that the response time of the homogeneous orientation mode is shorter than that of a twist mode because of the simple orientation. In fact, the homogeneous orientation mode gives a response speed which is about one half or less of that of the TN mode.
However, the homogeneous orientation mode also has some problem as follows.
First, with a structure as shown in FIG. 35, a voltage-transmission curve as shown in FIG. 36 is obtained, which indicates that a sufficient black display is not obtained for a voltage range over a few volts. In order to solve this problem, a phase plate of a uniaxially-drawn film has been employed in the art, as shown in FIG. 37. Thus, a voltage-transmission curve as shown in FIG. 38 is obtained, thereby realizing a black display over a greater voltage range.
However, as shown in FIG. 39, the viewing angle characteristics of such a display device are not desirable. While it is a well-known technique in the art to improve the viewing angle characteristics by adding a negative phase plate 301 having a negative refractive index anisotropy, as shown in FIG. 40, the improvement in the viewing angle characteristics may be insufficient as can be seen from FIG. 41.
It is known in the art that a negative inclined phase plate is widely employed in a TN panel for viewing angle compensation purposes (U.S. Pat. No. 5,506,706, Yamahara Patent of Sharp Co.). However, it has been believed in the art that it is not generally preferable to employ a negative inclined phase plate in combination with an ECB mode (e.g., the homogeneous orientation mode, the STN orientation mode, etc.) for the following reason.
Where an inclined phase plate is employed, the design optimization is limited by the following three parameters: the in-plane retardation; the retardation along the thickness direction; and the inclination angle of the symmetry axis of the index ellipsoid (the nz direction in the present invention) included in the phase plate with respect to the film surface. In principle, the inclined phase plate can be used with many liquid crystal modes by appropriately setting the three parameters.
In an actual production process, however, once two of the three parameters, e.g., the in-plane retardation and the inclination angle, are fixed, the retardation along the thickness direction is automatically determined. Thus, it is impossible to optimize all of the parameters. It may be possible to avoid this problem. However, it would be then necessary to change not only the thickness of the film but also the material of the phase plate itself each time the liquid crystal mode or the panel gap is changed. Thus, in view of the actual production process, it has been impractical to employ a phase plate in which the three parameters are optimized.
Recently, this technique has been more widely used in the TN liquid crystal mode for the following reason. Since the rubbing directions on the upper and lower substrates are orthogonal to each other, the in-plane remaining retardation of the liquid crystal layer becomes virtually zero (i.e., no need for compensation) when the voltage applied through the liquid crystal layer exceeds a certain level (which is in many cases set to 4 to 5 V). Therefore, the retardation along the thickness direction and the inclination angle can be utilized by employing an upper and lower film each having an arbitrary in-plane retardation so that their rubbing directions are orthogonal to each other.
According to one aspect of this invention, there is providing a liquid crystal display apparatus, including: a liquid crystal display device, the liquid crystal display device including: a pair of light transmissive substrates; a transparent electrode layer and an alignment film which are provided on one surface of each of the light transmissive substrates, the surface facing the other one of the light transmissive substrates; and a liquid crystal layer interposed between the pair of light transmissive substrates, wherein: the liquid crystal layer includes liquid crystal molecules; the liquid crystal molecules on a surface of each of the alignment films are pre-tilted in the same direction and by the same angle as those on a surface of the other one of the alignment films; and the liquid crystal layer has a homogeneous orientation; a pair of polarizers provided on respective sides of the liquid crystal display device; and at least one inclined phase plate including an index ellipsoid having three principal refractive indices na, nb and nc, wherein: the three principal refractive indices na, nb and nc of the index ellipsoid satisfy a relationship of na=nb greater than nc; each of the principal refractive indices na and nb is a principal refractive index along a direction in a surface of the inclined phase plate, and the principal refractive index nc is a principal refractive index along a direction normal to the surface of the inclined phase plate; the index ellipsoid is inclined by inclining the direction of the principal refractive index nc and the direction of one of the in-plane principal refractive indices na and nb with respect to each other about an axis extending along the direction of the other one of the in-plane principal refractive indices na and nb; the inclined phase plate is provided between the liquid crystal display device and at least one of the polarizers; and the inclined phase plate is arranged so that an inclination direction of the index ellipsoid as being projected onto the surface of one of the light transmissive substrates is generally parallel or antiparallel to an orientation direction of the liquid crystal molecules.
In one embodiment of the invention, the liquid crystal display apparatus further includes at least one negative phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz along an x axis, a y axis and a z axis, respectively, the three principal refractive indices nx, ny and nz satisfy a relationship of nx=ny greater than nz; the x axis and the y axis extend in the surface of the negative phase plate and the z axis extends in a direction normal to the surface of the negative phase plate; and the negative phase plate is provided between the liquid crystal display device and at least one of the polarizers.
In one embodiment of the invention, the liquid crystal display apparatus further includes at least one positive phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz, the principal refractive indices nx and ny being along an x axis and a y axis, respectively; the principal refractive indices nx and ny satisfy a relationship of nx greater than ny; the x axis and the y axis extend in the surface of the positive phase plate; the positive phase plate is provided between the liquid crystal display device and at least one of the polarizers; each of the polarizers has an absorption axis; and the positive phase plate is arranged so that the y axis substantially coincides with the absorption axis.
In one embodiment of the invention, the liquid crystal display apparatus further includes at least one negative phase plate including a negative index ellipsoid having three principal refractive indices nx1, ny1 and nz1 along an x1 axis, a y1 axis and a z1 axis, respectively; the three principal refractive indices nx1, ny1 and nz1 satisfy a relationship of nx1=ny1 greater than nx1; the x1 axis and the y1 axis extend in the surface of the negative phase plate and the z1 axis extends in a direction normal to the surface of the negative phase plate; the negative phase plate is provided between the liquid crystal display device and at least one of the polarizers; the liquid crystal display apparatus further includes at least one positive phase plate including a positive index ellipsoid having three principal refractive indices nx2, ny2 and nz2 along an x2 axis, a y2 axis and a x2 axis, respectively; the principal refractive indices nx2 and ny2 satisfy a relationship of nx2 greater than ny2; the x2 axis and the y2 axis extend in the surface of the positive phase plate; the positive phase plate is provided between the liquid crystal display device and at least one of the polarizers; each of the polarizers has an absorption axis; and the positive phase plate is arranged so that the y2 axis substantially coincides with the absorption axis.
In one embodiment of the invention, the inclined phase plate is arranged so that the inclination direction of the index ellipsoid and a pre-tilt direction of the liquid crystal molecules are substantially opposite to each other.
According to still another aspect of this invention, there is provided a liquid crystal display apparatus, including: a liquid crystal display device, the liquid crystal display device including: a pair of light transmissive substrates; a transparent electrode layer and an alignment film which are provided on one surface of each of the light transmissive substrates, the surface facing the other one of the light transmissive substrates; and a liquid crystal layer interposed between the pair of light transmissive substrates, wherein: the liquid crystal layer includes liquid crystal molecules; the liquid crystal molecules on a surface of each of the alignment films are pre-tilted in the same direction and by the same angle as those on a surface of the other one of the alignment films; the liquid crystal layer has a homogeneous orientation; a pair of polarizers provided on respective sides of the liquid crystal display device; and at least one inclined phase plate including an index ellipsoid having three principal refractive indices na, nb and nc, wherein: the three principal refractive indices na, nb and nc of the index ellipsoid satisfy a relationship of na=nb greater than nc; each of the principal refractive indices na and nb is a principal refractive index along a direction in a surface of the inclined phase plate, and the principal refractive index nc is a principal refractive index along a direction normal to the surface of the inclined phase plate; the index ellipsoid is inclined by inclining the direction of the principal refractive index nc and the direction of one of the in-plane principal refractive indices na and nb with respect to each other about an axis extending along the direction of the other one of the in-plane principal refractive indices na and nb; the inclined phase plate is provided between the liquid crystal display device and at least one of the polarizers; the liquid crystal display apparatus further includes at least one positive phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz, the principal refractive indices nx and ny being along an x axis and a y axis, respectively; the principal refractive indices nx and ny satisfy a relationship of nx greater than ny; the x axis and the y axis extend in the surface of the positive phase plate; the positive phase plate is provided between the liquid crystal display device and at least one of the polarizers; each of the polarizers has an absorption axis; the positive phase plate is arranged so that the y axis substantially coincides with an orientation direction of the liquid crystal molecules; and the inclined phase plate is arranged so that an inclination direction of the index ellipsoid as being projected onto the surface of one of the light transmissive substrates is generally parallel or antiparallel to an orientation direction of the liquid crystal molecules.
In one embodiment of the invention, the liquid crystal display apparatus further includes at least one negative phase plate including a negative index ellipsoid having three principal refractive indices nx1, ny1 and nz1 along an x1 axis, a y1 axis and a z1 axis, respectively; the three principal refractive indices nx1, ny1 and nz1 satisfy a relationship of nx1=ny1 greater than nz1; the x1 axis and the y1 axis extend in the surface of the negative phase plate and the z1 axis extends in a direction normal to the surface of the negative phase plate; and the negative phase plate is provided between the liquid crystal display device and at least one of the polarizers.
In one embodiment of the invention, an inclination angle of the index ellipsoid is equal to or greater than 10xc2x0 and less than or equal to 80xc2x0.
In one embodiment of the invention, the inclination angle of the index ellipsoid is equal to or greater than 20xc2x0 and less than or equal to 50xc2x0.
In one embodiment of the invention, where the inclined phase plate is provided on both sides of the liquid crystal display device, a product (naxe2x88x92nc)xc3x97d of a difference between the principal refractive index na and the principal refractive index nc and a thickness d of the inclined phase plate is set to be in a range from 15 nm to 700 nm; and where the inclined phase plate is provided only on one side of the liquid crystal display device, the product (naxe2x88x92nc)xc3x97d is set to be in a range from 30 nm to 1500 nm.
In one embodiment of the invention, where the inclined phase plate is provided on both sides of the liquid crystal display device, the product (naxe2x88x92nc)xc3x97d is set to be in a range from 33 nm to 159 nm; and where the inclined phase plate is provided only on one side of the liquid crystal display device, the product (naxe2x88x92nc)xc3x97d is set to be in a range from 66 nm to 318 nm.
In one embodiment of the invention, where the inclined phase plate is provided on both sides of the liquid crystal display device, a product (naxe2x88x92nc)xc3x97d of a difference between the principal refractive index na and the principal refractive index nc and a thickness d of the inclined phase plate is set to be in a range from 1 nm to 200 nm; and where the inclined phase plate is provided only on one side of the liquid crystal display device, the produce (naxe2x88x92nc)xc3x97d is set to be in a range from 2 nm to 400 nm.
In one embodiment of the invention, where the inclined phase plate is provided on both sides of the liquid crystal display device, the product (naxe2x88x92nc)xc3x97d is set to be in a range from 30 nm to 150 nm; and where the inclined phase plate is provided only on one side of the liquid crystal display device, the product (naxe2x88x92nc)xc3x97d is set to be in a range from 60 nm to 300 nm.
In one embodiment of the invention, each of the polarizers has an absorption axis; and an angle between a direction of the absorption axis and an inclination direction of the index ellipsoid in the inclined phase plate is greater than xe2x88x925xc2x0 and less than 50xc2x0.
In one embodiment of the invention, an angle between an orientation direction of the liquid crystal molecules and an inclination direction of the index ellipsoid in the inclined phase plate is greater than xe2x88x925xc2x0 and less than 5xc2x0.
In one embodiment of the invention, an angle between an orientation direction of the liquid crystal molecules and an inclination direction of the index ellipsoid in the inclined phase plate is 0xc2x0.
In one embodiment of the invention, an angle between an orientation direction of the liquid crystal molecules and an inclination direction of the index ellipsoid in the inclined phase plate is greater than 40xc2x0 and less than 50xc2x0.
In one embodiment of the invention, an angle between an orientation direction of the liquid crystal molecules and an inclination direction of the index ellipsoid in the inclined phase plate is 45xc2x0.
In one embodiment of the invention, where the negative phase plate is provided on both sides of the liquid crystal display device, a product (nxxe2x88x92nz)xc3x97d of a difference between the principal refractive index nx and the principal refractive index nz and a thickness d of the negative inclined phase plate is set to be in a range from 5 nm to 200 nm; and where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nxxe2x88x92nz)xc3x97d is set to be in a range from 10 nm to 400 nm.
In one embodiment of the invention, where the negative phase plate is provided on both sides of the liquid crystal display device, the produce (nxxe2x88x92nz)xc3x97d is set to be in a range from 35 nm to 105 nm; and where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nxxe2x88x92nz)xc3x97d is set to be in a range from 70 nm to 210 nm.
In one embodiment of the invention, where the negative phase plate is provided on both sides of the liquid crystal display device, a product (nxxe2x88x92nz)xc3x97d of a difference between the principal refractive index nx and the principal refractive index nz and a thickness d of the negative inclined phase plate is set to be in a range from 1 nm to 100 nm; and where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nxxe2x88x92nz)xc3x97d is set to be in a range from 2 nm to 200 nm.
In one embodiment of the invention, where the negative phase plate is provided on both sides of the liquid crystal display device, the product (nxxe2x88x92nz)xc3x97d is set to be in a range from 1 nm to 30 nm; and where the negative inclined phase plate is provided only on one side of the liquid crystal display device, the product (nxxe2x88x92nz)xc3x97d is set to be in a range from 2 nm to 60 nm.
In one embodiment of the invention, where the positive phase plate is provided on both sides of the liquid crystal display device, a product (nxxe2x88x92ny)xc3x97d of a difference between the principal refractive index nx and the principal refractive index ny and a thickness d of the positive inclined phase plate is set to be in a range from 1 nm to 125 nm; and where the positive inclined phase plate is provided only on one side of the liquid crystal display device, the product (nxxe2x88x92ny)xc3x97d is set to be in a range from 2 nm to 250 nm.
In one embodiment of the invention, where the positive phase plate is provided on both sides of the liquid crystal display device, the product (nxxe2x88x92ny)xc3x97d is set to be in a range from 30 nm to 90 nm; and where the positive inclined phase plate is provided only on one side of the liquid crystal display device, the product (nxxe2x88x92ny)xc3x97d is set to be in a range from 60 nm to 180 nm.
In one embodiment of the invention, where the positive phase plate is provided on both sides of the liquid crystal display device, a product (nxxe2x88x92ny)xc3x97d of a difference between the principal refractive index nx and the principal refractive index ny and a thickness d of the positive inclined phase plate is set to be in a range from 1 nm to 100 nm; and where the positive inclined phase plate is provided only on one side of the liquid crystal display device, the product (nxxe2x88x92ny)xc3x97d is set to be in a range from 2 nm to 200 nm.
In one embodiment of the invention, where the positive phase plate is provided on both sides of the liquid crystal display device, the product (nxxe2x88x92ny)xc3x97d is set to be in a range from 5 nm to 40 nm; and where the positive inclined phase plate is provided only on one side of the liquid crystal display device, the product (nxxe2x88x92ny)xc3x97d is set to be in a range from 10 nm to 80 nm.
In one embodiment of the invention, the inclined phase plate includes a support made of a transparent organic polymer and a discotic liquid crystal material cured on the support in an inclined orientation.
In one embodiment of the invention, the inclined phase plate includes a support made of a transparent organic polymer and a discotic liquid crystal material cured on the support in a hybrid orientation.
In one embodiment of the invention, a product of a thickness of the liquid crystal layer and a refractive index anisotropy (xcex94n) of the liquid crystal layer is in a range from 180 nm to 500 nm.
In one embodiment of the invention, the product of the thickness of the liquid crystal layer and the refractive index anisotropy (xcex94a) of the liquid crystal layer is in a range from 220 nm to 350 nm.
In one embodiment of the invention, the liquid crystal display apparatus lumber includes an element for diffusing transmitted light in normal and near-normal viewing directions toward upper and loner directions.
In one embodiment of the invention, the liquid crystal display apparatus further comprises at least one positive phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz, the principal refractive indices nx and ny being along an x axis and a y axis, respectively the principal refractive indices nx and ny satisfy a relationship of nx greater than ny; the x axis and the y axis exist is a surface of the positive phase plate; the positive phase plate is provided between the inclined phase plate and the liquid crystal display device; each of the polarizers has an absorption axis; the x axis, which is a slog axis of the positive phase plate, is substantially parallel or substantially orthogonal to an inclination direction of the index ellipsoid of the inclined phase plate as being projected onto the surface of one of the light transmissive substrates; and an angle between the absorption axle of each of the polarizers and the slow axle of the positive phase plate is substantially 45xc2x0.
In one embodiment of the invention, the liquid crystal display apparatus further comprises a positive phase plate including an index ellipsoid having three principal refractive indices nx, ny and nz the principal refractive indices nx and ny being along an x axis and a y axis, respectively; the principal refractive indices nx and ny satisfy a relationship of nx greater than ny; the x axis and the y axis exist in a surface of the positive phase plate; the positive phase plate is provided between the inclined phase plate and at least one of the polarizers; each of the polarizers has an absorption axis; the x axis, which is a slow axis of the positive phase plate, is substantially parallel or substantially orthogonal to an inclination direction of the index ellipsoid of the inclined phase plate as being projected onto the surface of one of the light transmissive substrates; and an angle between the absorption axis of each of the polarizers and the slow axis of the positive phase plate is substantially 45xc2x0.
In one embodiment of the invention, a difference between (1) a sum of an in-plane retardation of the negative inclined phase plate and an in-plane retardation of the positive inclined phase plate and (2) a retardation of the liquid crystal layer when a black display is produced by the liquid crystal display apparatus is within xc2x110 nm.
In one embodiment of the invention, the sum of the in-plane retardation of the negative inclined phase plate and the in-plane retardation of the positive inclined phase plate is less than or equal to 100 nm.
With the above-described structure, even when linearly-polarised light passes through the birefringent liquid crystal layer thus producing normal light and abnormal light and converting the linearly-polarised light into elliptically-polarised light due to the phase difference therebetween such elliptically-polarised light can be compensated for by the use of the optical phase plate in which the short axis of the index ellipsoid including the principal refractive index nc is inclined with respect to the direction normal to the surface of the optical phase plate.
Moreover, a liquid crystal display device having a homogeneous orientation may be provided with a negative phase plate where the direction along which the index ellipsoid of the phase plate is inclined is opposite to the pro-tilt angle of the liquid crystal molecules. In such a case, it is possible to compensate for the optical anisotropy of the liquid crystal molecules a gray-level display or a blank display even when the viewing angle is greatly inclined.
Moreover, a liquid crystal display device having a homogeneous orientation may be provided with a positive phase plate where the direction along which the index ellipsoid of the phase plate is inclined is opposite to the pre-tilt angle of the liquid crystal molecules. In such a case, it is possible to compensate for the optical anisotropy of the liquid crystal molecules in a gray-level display or a blank display oven when the viewing angle is greatly inclined.
Moreover, a liquid crystal display device having a homogeneous orientation may be provided with a positive phase plate and a negative phase plate where the direction along which the index ellipsoid of the phase plate is inclined is opposite to the pre-tilt angle of the liquid crystal molecules. In such a case, it is possible to compensate for the optical anisotropy of the liquid crystal molecules in a gray-level display or a black display even when the viewing angle is greatly inclined. The positive phase plate and the negative phase plate can be replaced with a single biaxial phase plate which has both the characteristics of the positive phase plate and those of the negative phase plate.
Moreover, a liquid crystal display device having a homogeneous orientation may be provided with a phase plate where the direction along which the index ellipsoid of the phase plots is inclined is opposite to the pre-tilt angle of the liquid crystal molecules. In such a case, it is possible to compensate for the optical anisotropy of the liquid crystal molecules in a gray-level display or a bleak display even when the viewing angle is inclined. While the optical phase plate is preferably provided on both sides of the liquid crystal display device, the optical phase plate may alternatively be provided only on one side of the liquid crystal display device, and the improvement of the viewing angle characteristics can still be obtained.
Moreover, the normal-viewing-direction display characteristics of the liquid crystal display devise having a homogeneous orientation can be optically compensated for by the use of a positive phase plate, while the inclined-viewing-direction display characteristics can be optically compensated for by the use of an inclined phase plate in which the index ellipsoid is inclined. Thus, it is possible to obtain a liquid crystal display apparatus having a wide viewing angle.
In a liquid crystal display apparatus of the present invention, the optical compensation for the liquid crystal molecules in the vicinity of the glass substrate is provided by the inclined phase plate in which the index ellipsoid is inclined. In another liquid crystal display apparatus of the present invention, the optical compensation for the liquid crystal molecules in the middle of the liquid crystal layer along the thickness direction thereof is further provided by the negative phase plate. Thus, it is possible to compensate for the optical anisotropy of the liquid crystal molecules in a gray-level display or a black display even when the viewing angle is greatly inclined.
The two plates, i.e., the inclined phase plate in which the index ellipsoid is inclined and the negative phase plate, can be replaced with a single biaxial or hybrid-orientation phase plate which is obtained by combining together the optical characteristics of such two plates.
The effect of combining a positive phase plate where nx less than ny with a negative inclined phase plate will be described. As already discussed, an inclined phase plate has three parameters, and each of the three parameters is represented by a function of the other two parameters. Thus, except for the TNT mode, optimizing the three parameters at the same time has been practically difficult as it imposes undue burden on the material selection end the deposition process.
As discussed above, we have found the optimal parameters within the currently available materials and processes. However, the design of a liquid crystal panel greatly depends upon its application, and these optimal parameters may not always be realized. Our further study has revealed that if one stresses on the improvement in the viewing angle characteristics, it is important to adjust the retardation along the thickness direction in accordance with the inclination angle, and the in-plane retardation has only a small effect on the viewing angle characteristics.
It has also been discovered that the contribution of the in-plane retardation is mostly to the remaining in-plane retardation compensation in the liquid crystal layer in a black display, and the in-plane retardation has substantially no contribution to the viewing angle characteristics. When the in-plane retardation is the liquid crystal layer in a black display does not exceed 100 nm, a practically sufficient contrast can be obtained for inclined viewing angles.
Therefore, the difference between the in-plane retardation of the liquid crystal layer and that of the inclined phase plate can be compensated for by providing a positive phase plate so that the slow axis is parallel or orthogonal to the rubbing direction of the liquid crystal layer. In such a ease, the improved viewing angle characteristics are comparable to those which are obtained only with an optimal inclined phase plate, and it is possible to provide, by the use of an appropriate positive phase plate, a desirable normal-viewing-direction contrast irrespective of the in-plane retardation of the inclined phase plate. It the sum of the respective in-plane retardation values of the liquid crystal layer, the inclined phase plate and the positive phase plate can be set to be less than or equal to xc2x110 nm, it is possible to obtain a practically sufficient contrast of 200 or more.
According to the present invention the positive phase plate is designed such that nx less than ny. In practice however, the positive phase plate may be designed such that nx greater than ny as the object is to compensate for the retardation of the liquid crystal layer. In an actual design of an inclined phase plots, the production of the phase plate becomes more difficult as the inclination angle is increased, and it is often the case that the in-plane retardation is insufficient for the liquid crystal layer used. In view of this, nx less than ny is employed is the present invention so that the design can be generally employed for various applications.
The positive phase plate can be arranged in any of various ways. For example, positive phase plate may be provided on one or both aides of the liquid crystal layer, or between the inclined phase plate and the liquid crystal layer or between the inclined phase plate and the polarizer. In practice, the positive phase plate would effectively function wherever it is placed. In view of obtained viewing angle characteristics which are more symmetrical and with which images are more easily viewed sad in view of the productivity of the panel, it is preferable to arrange two positive phase plates having substantially the same retardation on the respective sides of the liquid crystal layer. In each of the above-described arrangements, the liquid crystal layer has a homogeneous orientation which is obtained by combining two substrates together so that their rubbing directions are antiparallel to each other. The employment of such a homogeneous orientation, which has no twist in the liquid crystal orientation, results in an improvement, typically about a 2-fold increase, in the response speed to an applied voltage over those obtained by the TN mode which is widely employed in conventional liquid crystal display apparatuses. As a rebuilt the display quality in a high-speed motion picture display is improved over those of conventional liquid crystal display apparatuses.
The present invention described above provides an effect of sufficiently improving the viewing angle over those of the liquid crystal display apparatuses.
However, while the wide viewing angle characteristics obtained by the present invention are substantially symmetrical for left and right viewing angles, the viewing angle characteristics are not symmetrical for lower and upper viewing angles. In view of this, the above-described lens element is provided so as to obtain viewing angle characteristics with a high degree of cylindrical symmetry. Thus, the present invention provides a liquid crystal display apparatus which has substantially no drawbacks as compared to a CRT, i.e., the mainstream display apparatus currently need is television displays.
Thus, the invention described herein makes possible the advantage of providing a liquid crystal display apparatus having a wide viewing angle, a high display quality and a high response speed by employing a homogeneous orientation liquid crystal display device with a high response speed in combination with a phase plate of a special type and structure different from the conventional phase plates go as to improve the viewing angle dependency.
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.


A portable storage container with a lid that is removably positionable on the top of the container body and defines indents or grooves on opposite sides, is described. A strap is secured to opposing side walls of the container body and extends through the side indents to secure the lid on the top of the container body. The top of the container body may also define side indents/grooves that align with the side indents of the lid to provide a snug fit of the strap on top of the lid. The strap may also be moved to a bottom depression or groove on the underside of the bottom of the container body.

Portable storage devices otherwise known as caddies, bins, containers or totes are becoming popular in workplaces, presenting a relatively mobile storage alternative to drawers, cupboards and cabinets. These are typically in the form of rectangular shaped bins, often made of plastic, often of drawer size or larger, that can house papers, laptops, chargers, writing implements, and other office equipment.
Some typical problems with such bins include:
First, such bins need to be carried using two hands, preventing the use of a free hand while transporting the container and its contents. In containers with integrated central handles, such as a tool tray, caddy or tackle-box, a central part of the storage area may be partially occluded, resulting in a container with limited storage utility. A largely open, rectangular storage may be practical in that it maximizes use for file and folder storage and retrieval.
Second, there is a lack of options regarding secure closure of bins in an aesthetically pleasing manner, unless additional locking devices are used. Such devices often are not integrated into the container.
Thirdly, straps that may be used to carry such a bin may separate and may be lost, and such straps, handles or lids may be obtrusive and may serve no purpose most of the time, that is when the bid is not being carried.
Also, lids with integrated handles tend not to have a useful secondary purpose. Lids that are not integrated tend to get lost or set aside and neglected, even if they allow the container to be carried with a single hand.

Portable storage device with security and closure mechanism


A dimmable arc lamp assembly comprises a lamp enclosure comprising a chamber enclosing a light-emitting material, first and second electrodes extending into the chamber of the lamp enclosure, and a heating element proximate the chamber configured to heat at least a portion of the lamp enclosure to a temperature greater than the boiling point of the light-emitting material such that the light-emitting material remains in a gaseous state. Because the light-emitting material remains above its boiling point during lamp operation, dimming is not susceptible to control issues that can result from condensation of the light-producing material. Such lamps may be used in various applications such as in flat panel displays.

An arc lamp is any light source in which an electric arc produces visible light. Typically, arc lamps include a glass or plastic tube that is filled with light-emitting materials such as argon, mercury, sodium or other inert gas. When an electric potential is applied between two electrodes inserted into the tube, the resultant electric arc breaks down the gaseous materials and produces an ongoing plasma discharge that results in visible light.
Arc lamps have provided lighting in numerous home, business and industrial settings for many years. More recently, arc lamps have been used as backlights in liquid crystal displays such as those used in computer displays, cockpit avionics, flat panel televisions and the like. Such displays typically include any number of pixels arrayed in front of a relatively flat light source. By controlling the light passing from the backlight through each pixel, color or monochrome images can be produced in a manner that is relatively efficient in terms of physical space and electrical power consumption.
Despite the widespread adoption of displays and other products that incorporate arc light sources, however, designers continually aspire to improve the performance of the light source, as well as the overall performance of the display. In particular, the nature of many arc lamps can lead to difficulties in controlling a dimmable display. As a result, various techniques for controllable dimming the light produced from an arc lamp have been attempted, with varying degrees of success.
Accordingly, it is desirable to provide devices and techniques for effectively and efficiently controlling the brightness of various arc lamps and arc lamp displays. Other desirable features and characteristics will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.

Dimmable high pressure arc lamp apparatus and methods


A self-diagnostic method for PON protection system, in which optical switch-related failure can be previously inspected, and a PON protection system. A circuit is configured while an optical switch is switched so that signal light from an ONU is input to both a normal system OSU and a redundancy system OSU of an optical access network including the ONU, and there are conducted a circuit configuration test in which the signal light to the normal system OSU and the signal light to the redundancy system OSU are monitored for a predetermined period of time, and when the signal light to one of the OSUs and the signal light to the other do not correspond to each other, it is judged as abnormality and an open state test in which an optical switch is opened so that the signal light from the ONU is input to only the normal system OSU of the optical access network including the ONU, a circuit of the redundancy system OSU and the ONU is brought into an open state, the signal light to redundancy system OSU is monitored for a predetermined time of period, and when the signal light to the redundancy system exists, it is judged as abnormality.

1. Field of the Disclosure
This disclosure relates to a failure detection technique in a communication system.
2. Discussion of the Background Art
A Passive Optical Network (PON) is an optical access network in a point-to-multipoint in which one or more optical subscriber line terminating devices (ONU: Optical Network Units) as user side transmission devices are connected to an optical subscriber line termination board (OSU: Optical Subscriber Unit) as a station-building side transmission device through an optical fiber and a splitter.
In the PON, PON protection is a technique of making an OSU, an ONU, an optical fiber, or a splitter as a constitutive factor of a system redundant and avoiding system down due to OSU failure, ONU failure, optical fiber breakage, and splitter breakage (non-patent document 1, pp. 113-116). Namely, upon applying the PON protection, when those constitutive factors of the system fail or are broken, operation is switched from a normal system to a redundancy system, whereby a service is continued.
To make OSU redundant is particularly considered important in the PON protection. As a first reason, since the OSU is an aggregation point of signals in point-to-multipoint communication, that is, PON, there is such a wide-range property of influence that when the OSU fails, all the subordinated ONUs (users) are affected. As a second reason, since the OSU is constituted of electronic components and software operating them, a possibility of a failure is highly likely to occur in comparison with an optical fiber/splitter as a mere optical waveguide. Accordingly, usually the OSU should be first made redundant in the PON protection.
One to a plurality of OSUs, an exchange switch (connected to the high-order side of the one to a plurality of OSUs), a high-order network interface (connected to the high-order side of the exchange switch), and an OLT controller controlling them are usually collectively stored in an optical subscriber line terminal station device (OLT: Optical Line Terminal). Namely, the OLT is a communication node exchanging the high-order network with PON, and a large number of OSUs which become interfaces on the PON side may be required. Accordingly, when the OSU is made redundant, an optimum constitution is required to be considered based on such a basic constitution of the OLT (in each drawing, the exchange switch, the high-order network interface, and input and output lines associated with them are omitted in terms of avoiding complexity).
In a first constitution in a conventional OSU redundant technique, as shown in FIG. 1, a redundancy system OSU 12 is provided for each normal system OSU 11 in an OLT 10 (Type-B of non-patent documents 1, p. 114). For convenience, the first constitution is referred to as a "redundancy system OSU independent type". Specific configuration and operation of the "redundancy system OSU independent type" are as follows. A normal system OSU 11-1 and a redundancy system OSU 12-1 are connected to an ONU 51 (the number of the ONUs is an integer not less than 0, and ports on the ONU side of a splitter may include a free port) through an N:2 splitter 41-1 (N is an integer of not less than 1) (a splitter is further installed farther away than the N:2 splitter, and further branching may be performed). The normal system OSU 11-1 transfers a signal from the lower ONU 51 to the upper exchange switch and transfers a signal from the upper exchange switch to the lower ONU 51 respectively. When the normal system OSU 11-1 fails during communication, an OLT controller 15 having detected the failure performs switching,
(i) the normal system OSU 11-1 is stopped,
(ii) the redundancy system OSU 12-1 is started, and
(iii) setting of the exchange switch is changed.
Then, the redundancy system OSU 12-1 starts to transfer the signal from the lower ONU 51 to the upper exchange switch and transfer the signal from the upper exchange switch to the lower ONU 51 similarly to before the occurrence of the failure and thereby continues a service.
A connection form between a normal system OSU 11-i and a redundancy system OSU 12-i (i=2, 3, . . . ) and the operation at the time of protection are the same as those in the relation between the OSU 11-1 and the OSU 12-1.
In the constitution of the "redundancy system OSU independent type", since the same number of the redundancy system OSUs and the normal system OSUs are required to be previously stored in the OLT, there are problems of OLT slot consumption and an increase in OSU introduction cost.
Meanwhile, in a second constitution of the conventional OSU redundant technique, as shown in FIG. 2, the redundancy system OSU 12 is provided in the OLT 10 with respect to a plurality of the normal system OSUs 11, whereby the problems of the OLT slot consumption and the increase in cost are suppressed (FIG. 2: FIG. 1 of patent document 1 and FIG. 1 of patent document 2). For convenience, the second constitution is referred to as a "redundancy system OSU sharing type". Specific configuration and operation of the "redundancy system OSU sharing type" are as follows.
The OLT 10 stores a normal system OSU 11-i (i=1, 2, 3, . . . , and M, M is an integer of not less than 1) and a redundancy system OSU 12-x. Input and output ports on the ONU side of the redundancy system OSU 12-x is connected to an input and output port (referred to as a port x) of an M:1 optical switch 32. The M input and output ports (referred to as ports 1, 2, 3, . . . , and M) on the ONU side of the M:1 optical switch 32 are paired as the port 1 and the OSU 11-1, the port 2 and the OSU 11-2, the port 3 and the OSU 11-3, . . . , and the port M and the OSU 11-M, and these pairs are connected to N or less ONUs 50 through N:2 splitters 41-i (i=1, 2, 3, . . . , and M) (N ports on the ONU side of the splitter may include a free port).
The normal systems OSU 11 each transfer a signal from the lower ONU 50 to the upper exchange switch and transfer a signal from the upper exchange switch to the lower ONU 50. When the normal system OSU 11-1 fails during communication, the OLT controller 15 having detected the failure performs switching,
(i) the normal system OSU 1 is stopped,
(ii) the port x and the port 1 are connected in the optical switch 32,
(iii) a redundancy system OSUx is started, and
(iv) setting of the exchange switch is changed.
Then, the redundancy system OSU 12-x starts to transfer the signal from the lower ONU 50 to the upper exchange switch and transfer the signal from the upper exchange switch to the lower ONU 50 respectively similarly to before the occurrence of the failure and thereby continues a service.
It is the same as the above description that the operation of the failure of other normal system OSUs 11-i (i=2, 3, and . . . ), except that the normal system OSU 11, the splitter 41, and the port of the optical switch 32 are exchanged.
In this description (FIG. 2), the optical switch 32 is controlled by the optical switch controller 31, and moreover, the OLT controller 15 controls the optical switch controller 31. However, the optical switch controller 31 may not be provided, and the optical switch 32 may be controlled directly by the OLT controller 15.
In the constitution of the "redundancy system OSU sharing type", since only the single redundancy system OSU 12 stored in the OLT 10 may be provided with respect to the M normal system OSUs 11, the problems of the OLT slot consumption and the increase in the OSU introduction cost have been solved. Further, under the condition that there is a sufficiently low probability that a plurality of the normal system OSUs fail simultaneously, it is easy to secure reliability by making the OSU redundant in this constitution and operation.
In the OLT, although the exchange switch, the high-order network interface, and the OLT controller may be made redundant, this case is not directly related in the disclosure, and therefore, description thereof will be omitted.

Self-diagnostic method for PON protection system, and PON protection system

Nippon Telegraoh and Telephone Corporation


A device for converting wave-motion power having a float, which, in use, is vertically movable in response to the wave-motion; the motion being transmitted to an input shaft which rotates with reciprocating rotary motion and is connected to an output shaft by way of a transmission unit. The transmission unit transfers torque from the input shaft to the output shaft along two torque paths and has two freewheels that are arranged respectively along the two paths, and are configured so as to make the rotation of the output shaft unidirectional, independently of the rotation direction of the input shaft.

As is known, the need is increasingly felt to exploit so-called alternative and/or renewable energy sources, to reduce the use of fossil fuels and, therefore, to not inflict environmental conditions with pollutants. In addition to solar energy and wind energy, another potential source of energy that could be used is that defined by the wave-motion of the seas. Said wave-motion involves a cyclical rise and fall of the upper surface of the sea and could be used to actuate mechanical members in a substantially continuous and inexhaustible way.
Devices are known which, through a combination of opposed overrunning clutches, turn the reciprocating and uneven motion of a float in a unidirectional rotary motion of a shaft connected to a generator of electricity. However, in order to optimize the efficiency of energy conversion, it is appropriate to optimize the size of the float in particular to reduce the device kinematic oscillation or torque output.

Device for converting the power of sea wave motion


A method and computing system for receiving, on a computing device, a plurality of individual audio/video streams from a plurality of client electronic devices used by a plurality of users. The plurality of individual audio/video streams are processed, on the computing device, to generate a synchronous communication session for the plurality of users. A broadcast request is received, on the computing device, from one of the plurality of users to provide the synchronous communication session to a media interface device. A session audio/video stream of the synchronous communication session is provided, via the computing device, to the media interface device, wherein the session audio/video stream includes at least a portion of the plurality of individual audio/video streams.

The Internet currently allows for the free exchange of ideas and information in a manner that was unimaginable only a couple of decades ago. One such use for the Internet is as a communication medium, whether it is via one-on-one exchanges or multi-party exchanges. For example, two individuals may exchange private emails with each other. Alternatively, multiple people may participate on a public website in which they may post entries that are published for multiple people to read. Examples of such websites may include but are not limited to product/service review sites and topical blogs.
As is known in the art, the Internet may also allow users to engage in a quasi-real-time, interactive dialogue. For example and through the use of the Internet, users may engage in synchronous communication sessions (e.g., video conferences). Unfortunately, such synchronous communication sessions may require the use of proprietary (and costly) video conferencing equipment such as e.g., specialized systems that incorporate video display equipment (e.g., a monitor), video capture equipment (e.g., a video camera), and audio capture equipment (e.g., a microphone).


A computer controlled system, method, and corresponding computer data product, for utilizing a normalized gray scale pattern find within a machine vision system. The system and method (a) correlates a reference image having a first spatial resolution having no particular degree of rotation within a first search region of interest of an acquired image to find a potential match location, (b) correlates a rotated reference image having the first spatial resolution at a particular degree of rotation within the first search region of interest to find a potential match location, (c) selects the potential match location and the particular degree of rotation corresponding to the highest correlation value, (d) increases the spatial resolution of the reference image at the particular degree of rotation to generate a new reference image and correlating the new reference image within a second search region of interest centered at the selected potential match location, (e) selects an updated potential match location corresponding to a location having the highest correlation value that is completely within the search region of interest, (f) repeats steps (d) and (e) for all available resolutions for the reference image, and (g) selects a match location and orientation of a reference image within the acquired image corresponding to the location having the highest correlation value.

Machine Vision has used numerous algorithms over the years to locate the object of interest in the Field Of View (FOV). Typically the user captures a reference image and identifies the object of interest by drawing a Region Of Interest (ROI) around it using a Graphical User Interface (GUI). The user also draws a search ROI to identify the maximum movement of the object of interest within the search ROI. Either the entire grayscale ROI or unique characteristics of the object of interest is saved in memory as a reference template. During an inspection the vision algorithm searches for the object of interest within the search ROI and if one is found and the match is within acceptable limits it can provide the match level and both the location and angular rotation of the object within the FOV. Key parameters are accuracy of match, accuracy of location, accuracy of rotation, and execution time of the algorithm
A vision algorithm that the machine vision industry has traditionally used is the Normalized Grayscale Correlation (NGC) algorithm. This algorithm basically performs a cross-correlation between a "reference image" and an "inspection image" using normalized values. Cross-Correlation is a mathematical process of sliding the reference template across the search ROI and creating a 2D array of correlation results. The individual correlation results give an indication of the degree of match of the reference pattern with that particular location in the search ROI.
Normalization is a modification to the correlation algorithm to reduce the affects of changes in illumination on the correlation results.
Correlation is susceptible to minor rotational changes of the object and will fail if the inspection image is rotated more than approximately ±5 degrees from the reference template. Therefore the vision algorithm handles rotational variations of the inspection image by performing correlation with rotated versions of the reference template.
One form of the NGC formula is:r=Numerator/Denominator whereNumerator=(N*Σ(I*R))−(ΣI*ΣR)Denominator={(N*ΣI2−(ΣI)2)*(N*ΣR2−(ΣR)2)}1/2N=number of pixels in reference templateI=inspection imageR=reference template
From the above formula it is easily seen that calculating a single correlation value requires numerous multiplications, additions, subtractions, divides, and square-roots. This needs to be repeated as the template is slid around the entire search ROI. The number of correlation results is (m2−m1+1)*(n2−n1+1) where the search ROI is m2×n2 and the object ROI is m1×n1. As an example assume that the m2=250, n2=200 (250×200), m1=100, and n1=100 (100×100) then the total number of correlation values is 15251. This operation requires:                305106257 multiples        457550000 adds        45753 subtracts        15251 divides        15251 square-roots
Machine Vision applications require the vision algorithm to provide results in real time. This requirement places constraints on the implementation of the NGC algorithm. In order to reduce the computational time of correlation of the reference image with the inspection image different resolution images are created of both the reference image search ROI and inspection image search ROI. The creation of the lower resolution images shall be referred to as decimation.
One approach to creating the decimated image is by taking the average of a 2×2 array to form the next higher pixel value. This filters out the higher spatial frequency content leaving only the lower frequency characteristics of the image. This results in 2 pyramids, one of the reference image ROI, and the other of the inspection image search ROI. Each level of the pyramid reduces the size of the reference image ROI and inspection image search ROI by a factor of 2 in width and 2 in height. The spatial frequency bandwidth is reduced by a factor of 2 at each successive level. The highest resolution images are at the bottom of the pyramid. A course correlation search is then performed at the top of the pyramid. Table 1 shows the reduction in the number of arithmetic operations required at the top of the pyramid for 3 levels of decimation.
TABLE 1SquareLevelm1n1m2n2MultiplesAddsSubtractsDividesRoots1 × 11001002502003051062574575500004575315251152512 × 25050125100194018822907500011628387638764 × 4252562501240567185375029649889888 × 81212312582186121248840280280
Points of interest, large correlation values, are then identified from the results of the course correlation search. Once points of interest have been identified at the top level of the pyramid an approach is required to follow the point(s) of interest down the pyramid to the highest level of resolution without following the wrong path. This reduces the total number of correlation values required to find the object in the inspection image resulting in a faster inspection time.
A shortcoming of the decimation approach is that blurring (loss of spatial frequency) of the image increases at each successive level of the pyramid. If decimation is carried far enough it would result in a uniformly smooth image with no features to be used for identification. Therefore, to increase performance it is desirable to have several levels to the pyramid, but to stop before being unable to find the object of interest due to a loss in the spatial frequency content. The amount of blurring introduced by decimation is also dependent upon the density of the spatial frequency content of the reference image ROI. Higher levels of decimation can be achieved, without significant loss of image content, with images containing lower spatial frequency. A means is therefore needed to determine the maximum number of decimation levels a reference image can tolerate without the loss of the required spatial frequency content necessary to identify the object of interest.
To accurately locate the object of interest the reference image must possess a minimum amount of both translational and rotational spatial frequency content. This requires that the reference image ROI have sufficient high spatial frequency content to produce a sharp correlation peak in the search ROI. Images with only low spatial frequency content have a flatter correlation peak causing minor pattern variations or noise to influence the location of the object of interest in the inspection image. A means is therefore required to determine the amount of both translational and rotational spatial frequency content of the reference image ROI.
Finally, the reference image ROI must not be distorted due to pixel saturation. Saturated pixels cause a loss of detail and may not move as the object of interest moves within the FOV. A means is therefore required to ensure that saturated pixels are minimized within the reference image ROI. The present invention disclosed herein overcomes the above limitations of the prior art machine-based vision systems.

System and method for using normalized gray scale pattern find


A system obtains ratings associated with a first set of advertisements hosted by one or more servers, where the ratings indicate a quality of the first set of advertisements. The system observes multiple different first user actions associated with user selection of advertisements of the first set of advertisements and derives a statistical model using the observed first user actions and the obtained ratings. The system further observes second user actions associated with user selection of a second advertisement hosted by the one or more servers and uses the statistical model and the second user actions to estimate a quality of the second advertisement.

1. Field of the Invention
Implementations described herein relate generally to on-line advertisements and, more particularly, to estimating qualities of on-line advertisements using observed user behavior.
2. Description of Related Art
On-line advertising systems host advertisements that may advertise various services and/or products. Such advertisements may be presented to users accessing documents hosted by the advertising system. An advertisement may include a "creative," which includes text, graphics and/or images associated with the advertised service and/or product. The advertisement may further include a link to an ad "landing document" which contains further details about the advertised service(s) and/or product(s). When a particular creative appears to be of interest to a user, the user may select (or click) the creative, and the associated link causes a user's web browser to visit the "landing document" associated with the creative and link. This selection of an advertising creative and associated link by a user is referred to hereinafter as a "click."
On-line advertising systems often track ad clicks for billing and other purposes. One non-billing purpose for tracking ad clicks is to attempt to ascertain advertisement quality. The click through rate (CTR) is a measure used to determine advertisement quality. CTR represents the fraction of times a given ad gets "clicked" on when an advertisement creative is presented to users. The CTR of an advertisement, however, is an imperfect measure of advertisement quality since it focuses on the advertisement creative rather than the object of that advertisement, which is the landing document. A user needs to click on an advertisement in order to determine if an advertisement is good or bad and, therefore, the occurrence/non-occurrence of a click is insufficient to determine the quality of an advertisement. Some advertisements receive many clicks because they have a good creative, but the landing document is completely unsatisfying, or irrelevant, to the user. Other advertisements receive very few clicks (e.g., due to the advertisement creative being poor), but every click leads to a satisfied user. Existing determinations of CTR associated with on-line advertisements, thus, provide imperfect measures of advertisement quality.

Estimating ad quality from observed user behavior


The present invention provides a method for removing a coating layer of SOG or photoresist from a wafer flat side on a wafer by first injecting a flow of a cleaning solution at the bottom surface of the wafer at a location adjacent to the edge of the wafer, and then rotating the wafer at a rotational speed sufficiently high so as to cause the cleaning solution being pulled from the bottom side to the top side of the wafer by flowing around the edge to remove the coating layer covering the unintended area on the top surface of the wafer.

The present invention generally relates to a method for removing unwanted coating material from a semiconductor wafer and more particularly, relates to a method for removing a bead of a coating material of spin-on-glass or photoresist from a wafer flat side by a cleaning solution.
Spin-on-glass (SOG) is frequently used for gap fill and planarization of inter-level dielectrics (ILD) in multi-level metalization structures. It is a very suitable material for use in low-cost fabrication of IC circuits. The most commonly used SOG materials are of two basic types; an inorganic type of silicate based SOG and an organic type of siloxane based SOG. The most commonly used SOG materials are silicon oxide based polysiloxanes. These polysiloxanes are featured with radical groups replacing or attaching to oxygen atoms. Based on these two basic structures, the molecular weight the viscosity and the desirable film properties of SOG can be modified and adjusted to suit the requirement of each specific IC fabrication process.
SOG film is typically applied to a pre-deposited oxide surface as a liquid to fill gaps and steps on the substrate. Similar to the application method for photoresist films, a SOG material can be dispensed onto a wafer and spun with a rotational speed which determines the SOG thickness desired. After the film is evenly applied to the surface of the substrate, it is cured at a temperature of approximately 400xc2x0 C. and then etched back to obtain a smooth surface in preparation for a capping oxide layer on which a second interlevel metal may be patterned. The purpose of the etch-back step is to leave SOG between metal lines but not on top of the metal, while the capping oxide layer is used to seal and protect SOG during further fabrication processes. The siloxane based SOG material is capable of filling 0.15 micron gaps and therefore it can be used in 0.25 micron technology.
When fully cured, silicate SOG has similar properties like those of silicon dioxide. Silicate SOG does not absorb water in significant quantity and is thermally stable. However, one disadvantage of silicate SOG is the large volume shrinkage during curing. As a result, the silicate SOG retains high stress and cracks easily during curing and future handling. The cracking of the SOG layer can cause a serious contamination problem for the fabrication process. The problem can sometimes be avoided by the application of only a thin layer, i.e., 1000xcx9c2000 xc3x85 of the silicate SOG material. To build up thicker layers for filling gaps, multiple application and curing are required.
In the current SOG coating process, a solvent edge rinse and a solvent backside rinse process are utilized to remove SOG deposited on the wafer edge and on the backside of the wafer. This is shown in FIGS. 1xcx9c3. A semiconductor wafer 10 that has a flat side 12 is shown in FIG. 1. After a SOG coating process, a SOG layer 14 is blanket deposited on the top surface 16 of the wafer. The SOG layer is deposited as a dielectric layer for insulating between metal lines. In order to process the wafer in subsequent fabrication steps, the wafer must be positioned in various reaction chambers for various processes such as etching or deposition. In most of the process chambers, the wafer is positioned on a platform and held down on the edge by a wafer clamp. The function of the wafer clamp is to prevent the wafer from moving during the process where reactant gases or etching gases may be flowing through the reaction chamber. To enable the wafer clamp to function properly, the edge portion of the wafer of approximately 2xcx9c4 mm wide must be cleaned and any coating layer removed. The edge area 22 is shown in FIG. 1 on wafer 10.
In present wafer fabrication technology, the SOG layer deposited at unintended areas of the wafer can be removed in two different processes. The first process is a solvent edge rinse which is shown in FIG. 2. In this process, wafer 10 is placed on a platform (not shown) and spun at a predetermined rotational speed along a spin axis 26. The rotational speed of the wafer can be suitably adjusted for each specific application depending on the thickness of the layer to be removed and the type of chemical solution used. As shown in FIG. 2, a chemical solution injector 28 is used to inject chemical solution 32 onto the top edge 34 of the wafer. The chemical solution 38 reflected from the edge 34 of the wafer hits the chamber wall 42 and drain to the bottom of the process chamber. The solvent edge rinse process is effective in removing a limited area, i.e., a width of 2xcx9c4 mm, on the top edge of the wafer of unwanted coating materials such as SOG or photoresist. However, as shown in FIG. 1, when wafer 10 is spun around its center as a rotational axis, the flat side 12 of the wafer is not touched by the injected solvent 32 each time the wafer rotates. As a result, coating material 18 in the form of a bead remains on wafer 10.
The second cleaning process is a solvent backside rinse such as that shown in FIG. 3. The backside 48 of wafer 10 is cleaned in this process. A cleaning solution 52 is injected from a spray nozzle 54 onto the backside 48 of the wafer. The process is also known as a centrifugal spray cleaning process wherein a chemical solution, i.e., normally of a good solvent for the coating layer to be removed, is pressure-fed and injected directly onto a spinning wafer. The process can be effectively used to reduce the volume of fresh chemical consumed and is normally faster than an immersion process. After the injected chemical solution 52 hits the bottom surface 48 of the wafer, the chemical solution 56 reflects from the backside 48 of the wafer and drains into the bottom of the process tank (not shown). During a normal backside rinse process, the sprayed chemical solution 52 is only capable of rinsing on the backside 48 of the wafer and, none of the chemical solution 52 can reach the top surface 16. The bead 18 at the flat side 12 of the wafer is therefore not affected or cleaned in the backside rinse process.
Consequently, the SOG bead remains on the flat side of the wafer and eventually leads to SOG cracking during subsequent processes when a wafer clamp is pressed down on the SOG bead for mounting the wafer. The particles generated by the cracking of the SOG layer greatly contaminate the surface of the wafer and is detrimental to the yield and the quality of the IC produced.
It is therefore an object of the present invention to provide a method for removing a coating layer from an unintended area on a wafer that does not have the drawbacks or shortcomings of the conventional cleaning methods.
It is another object of the present invention to provide a method for removing a coating layer from wafer flat side to prevent the formation of a bead of the coating material.
It is a further object of the present invention to provide a method for removing a coating layer from an unintended area on the wafer flat side such that the wafer can be processed in subsequent processes without producing particle contaminants.
It is another further object of the present invention to provide a method for removing a spin-on-glass material from a wafer flat side such that a SOG build up at the flat side can be avoided.
It is still another object of the present invention to provide a method for removing a SOG layer from wafer flat side by utilizing existing backside rinse equipment.
It is yet another object of the present invention to provide a method for removing a SOG coating layer from wafer flat side by utilizing a predetermined rotational speed of the wafer such that a cleaning solution can be drawn from the underside of the wafer to the top side of the wafer.
It is still another further object of the present invention to provide a method for removing a coating material from wafer flat side by utilizing a combination of a desirable rotational speed and a desirable solvent mixture such that the solvent can be drawn from the bottom to the top of the wafer around the edge of the wafer.
The present invention provides a method for effectively removing a coating material such as SOG or photoresist layer from the wafer flat side such that a build up of the coating material and possible cracking in subsequent processing steps can be prevented.
In a preferred embodiment, the method for removing a coating material from an unintended area on a wafer can be carried out by the steps of first providing a wafer that has a top surface and a bottom surface, the top surface has a coating layer covering an unintended area along the edge of the wafer, spinning the wafer at a predetermined rotational speed, and injecting a flow of a cleaning solution at the bottom surface of the wafer adjacent to the edge of the wafer, whereby the predetermined rotational speed of the wafer pulls the cleaning solution from the bottom surface of the wafer to the top surface of the wafer to clean away the coating layer deposited at the unintended area. The flow of cleaning solution can be injected at the bottom surface of the wafer in an area immediately adjacent to the edge while the wafer is spun at a rotational speed of not less than 150 rpm. The cleaning solution utilized can be a mixture of one or more solvents selected from the group consisting of C5H10O3 and C3H8O at a suitable mixing ratio.

Method for removing coating bead at wafer flat edge

Taiwan SEmiconductor Manufacturing Co., Ltd.


Disclosed are novel high-sensitivity positive- and negative-working chemical-sensitization photoresist compositions capable of giving a highly heat-resistant patterned resist layer of high resolution having excellently orthogonal cross sectional profile without being influenced by standing waves. The composition contains, as an acid generating agent by irradiation with actinic rays, a specific cyano-substituted oximesulfonate compound such as .alpha.-(methylsulfonyloxyimino)-4-methoxybenzyl cyanide. The advantages obtained by the use of this specific acid-generating agent is remarkable when the film-forming resinous ingredient has such a molecular weight distribution that the ratio of the weight-average molecular weight to the number-average molecular weight does not exceed 3.5.

The present invention relates to a chemical-sensitization photoresist composition or, more particularly, to a photoresist composition, which may be of the positive-working type or negative-working type, containing a unique acid-generating agent capable of releasing an acid when exposed to actinic rays. The photoresist composition gives a patterned resist layer having high heat resistance and high resolution with a high photosensitivity of the photoresist composition without being affected by the influences of standing waves so that the patterned resist layer has an excellently orthogonal cross section.
It is a trend in recent years in the manufacturing technology of various electronic devices such as semi-conductor devices involving the process of photolithographic patterning works that so-called chemical-sensitization photoresist compositions are acquiring more and more prevalence by replacing those of the traditional types by virtue of the high sensitivity and high resolving power as compared with conventional photoresist compositions. The chemical-sensitization photoresist composition mentioned above contains a radiation-sensitive acid-generating agent which is a compound capable of releasing an acid when exposed to actinic rays so as to catalyze the solubilizing reaction and crosslinking reaction of the resinous ingredient in the positive- and negative-working photoresist compositions, respectively.
The chemical-sensitization photoresist compositions include two classes of positive-working and negative-working ones depending on the activity of the radiation-released acid either to increase or to decrease, respectively, the solubility of the film-forming resinous ingredient in the composition in an aqueous alkaline solution as a developer. In other words, the chemical-sensitization photoresist composition is positive-working when the film-forming resinous ingredient therein is imparted with an increase in the solubility in the alkaline developer solution and is negative-working when the film-forming resinous ingredient therein is imparted with a decrease in the solubility in the alkaline developer solution.
Accordingly, a positive-working chemical-sensitization photoresist composition usually contains a polyhydroxystyrene and the like of which a part of the hydroxy groups are substituted by solubility-suppressing acid-dissociable protective groups such as tert-butoxycarbonyl and tetrahydropyranyl groups while the film-forming resinous ingredient in the negative-working chemical-sensitization photoresist composition is usually a combination of an acid-crosslinkable melamine resin, urea resin and the like with an alkali-soluble resin such as novolac resins and polyhydroxystyrene resins optionally protected for a part of the hydroxy groups with the solubility-suppressing groups.
It is known that the resinous ingredient mentioned above in the photoresist composition should have a narrow molecular weight distribution expressed by the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn, i.e. Mw:Mn, in order to ensure high resolution of patterning and high heat resistance of the patterned resist layer.
The acid-generating agent heretofore proposed or currently used in chemical-sensitization photoresist compositions includes oximesulfonate compounds as disclosed in Japanese Patent Kokai 1-124848, 2-154266, 2-161444 and 6-67433, of which those oximesulfonate compounds having a cyano group in the molecule are preferred as exemplified by .alpha.-(p-toluenesulfonyloxyimino)benzyl cyanide, .alpha.-(4-chlorobenzenesulfonyloxyimino)benzyl cyanide, .alpha.-(4-nitrobenzenesulfonyloxyimino)benzyl cyanide, .alpha.-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)benzyl cyanide, .alpha.-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide, .alpha.-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide, .alpha.-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide, .alpha.-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide, .alpha.-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide, benzenesulfonyloxyimino-2-thienyl acetonitrile, .alpha.-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide, .alpha.-(p-toluenesulfonyloxyimino)-4-methoxybenzyl cyanide, .alpha.-(4-dodecylbenzenesulfonyloxyimino)-4-methoxybenzyl cyanide, p-toluenesulfonyloxyimino-3-thienyl acetonitrile and the like.
It is noted that each of the above named cyano group-containing oximesulfonate compounds has two aromatic groups in a molecule, one, substituting the .alpha.-carbon atom to which the cyano group --CN is bonded and, the other, forming the sulfonate ester. While the acid released from such a dually aromatic oximesulfonate compound by the irradiation with actinic rays is therefore an aromatic sulfonic acid such as benzenesulfonic acid and p-toluenesulfonic acid, a chemical-sensitization photoresist composition formulated with such an oximesulfonate compound and a resinous ingredient having a narrow molecular weight distribution mentioned above has a defect that the patterning of the resist layer is susceptible to the influences of standing waves so that the cross sectional profile of the patterned resist layer is not exactly orthogonal but has wavy or undulated side lines.


A brake system for a vehicle includes an electrically operated parking brake drive device which generates an operating force for operating the wheel brakes or dedicated parking brakes in response to energization, and which operates even upon cancellation of the energization while in the operated state. A braking force related amount detector detects a physical quantity related to a braking force exhibited by each of the hydraulic pressure operated wheel brakes. When a detected physical quantity exceeds a reference value in a stopped state of the vehicle, a controller energizes the electrically operated parking brake drive device. Thus, the frequency of operation of the electrically operated parking brake drive device is decreased while eliminating inconvenient operations required to operate the electrically operated parking brake drive device, thereby reducing noise and improving durability.

1. Field of the Invention
The present invention relates to a brake system for a vehicle, comprising a hydraulic pressure generating device for outputting a hydraulic pressure corresponding to a braking operation by a vehicle driver and hydraulic pressure operated wheel brakes mounted on wheels so as to be operated based on the hydraulic pressure output from the hydraulic pressure generating device. The brake system includes an electrically operated parking brake drive device which generates an operating force for operating the wheel brakes, or dedicated parking brakes mounted on wheels separately from the wheel brakes, in response to energization thereof, and which can be maintained in an operated state even upon cancellation of the energization while in the operated state. The brake system also includes a controller for controlling the energization of the electrically operated parking brake drive device.
2. Description of the Background Art
Japanese Patent No. 3595249 discloses a brake system for a vehicle in which when the shift position of the vehicle has been set at a parking position, when the vehicle is stopped on a slope, or when a driver manually operates an operating switch, the state of the vehicle is changed to a parking brake state by the operation of electrically operated parking brake drive device.
When the electrically operated parking brake drive device is operated, noise is generated and electric power is consumed by this operation. In the case where the electrically operated parking brake drive device is operated when the vehicle is stopped on a slope as referred to above, the frequency of the operation is increased depending on a preset threshold value for determining whether or not the vehicle is on a slope, resulting in an increase in frequency of generation of the noise and an increase in amount of the consumed electric power, and leading to degradation in durability of the electrically operated parking brake drive device. As a result, the driver needs to change the shift position to the parking position and operate the operating switch, which are inconvenient operations for the driver.


A feeding device includes a fixing base. A motor is fixed to the fixing base. The motor has an output axle. A transmission axle is fixedly connected to the output axle. The feeding device further includes a feeding block having a side fixedly connected to the transmission axle. The feeding block has a feeding notch. The feeding notch is formed around the transmission axle circumferentially. Hence, once a slender material enters the rotational space of the feeding block, the motor drives the feeding block to rotate, whereas the slender material is pressed by the feeding notch of the feeding block and sent out as a result of the continuous rotation of the feeding block. Hence, the feeding device not only enables continuous material conveyance but also allows the slender material to be conveyed smoothly even when the slender material is slightly bent or deformed.

1. Technical Field
The present invention relates to devices for transporting materials, and more particularly, to a feeding device for moving slender materials.
2. Description of Related Art
The feeding process performed by a conventional slender material feeding device usually involves lowering one end of the slender material and convey the material to an intended position. Both Taiwan Patent M336251 (hereinafter referred to as "citation 1") and Taiwan Patent M273402 (hereinafter referred to as "citation 2") disclose a conventional feeding device. Citation 1 discloses a rod-less cylinder linked to a sliding base of a linear rail through an adjustable connection plate so as to lower the slender material to an intended position. However, the feeding device of citation 1 is not only slender but also overly bulky in order to contain the slender material. Furthermore, it is likely that the feeding device of citation 1 cannot convey a material smoothly, if the material is slightly bent or deformed. Citation 2 discloses pushing a slender material by windingly conveying a flexible steel rod with a rotary device so as to reduce the required volume thereof and save space. However, the flexible steel rod is likely to entangle itself when it is windingly retracted; hence, not only is there a limitation of the length of the steel rod, but there is also a limitation of the length of the material being conveyed. In addition, like citation 1, citation 2 has another disadvantage, that is, it is likely that the feeding device of citation 2 cannot convey a material smoothly, if the material is slightly bent or deformed.
In view of this, to meet the needs of the R&D of feeding devices, it is imperative to design a feeding device not only capable of conveying a slender material continuously but also unsusceptible to a slight bend or deformation of the slender material.