The present invention generally provides a method of forming a high efficiency solar cell device by preparing a surface and/or forming at least a part of a high quality passivation layer on a silicon containing substrate. Embodiments of the present invention may be especially useful for preparing a surface of a p-type doped region formed on a silicon substrate so that a high quality passivation layer can be formed thereon. In one embodiment, the methods include exposing a surface of the solar cell substrate to a plasma to clean and modify the physical, chemical and/or electrical characteristics of the surface.

1. Field of the Invention
Embodiments of the present invention generally relate to the fabrication of solar cells and particularly to a device structure and method of passivating a surface of a crystalline silicon solar cell.
2. Description of the Related Art
Solar cells are photovoltaic devices that convert sunlight directly into electrical power. The most common solar cell material is silicon (Si), which is in the form of single, polycrystalline or multi-crystalline substrates. Because the cost of electricity generated using silicon-based solar cells is higher than the cost of electricity generated by traditional methods, there has been an effort to reduce the cost of manufacturing solar cells that does not adversely affect the overall efficiency of the solar cell.
FIG. 1 schematically depicts a cross-sectional view of a standard silicon solar cell 100 fabricated from a crystalline silicon substrate 110. The substrate 110 includes a base region 101, an emitter region 102, a p-n junction region 103, a dielectric passivation layer 104, front electrical contact 107 and rear electrical contact 108. The p-n junction region 103 is disposed between base region 101 and emitter region 102 of the solar cell, and is the region in which electron-hole pairs are generated when solar cell 100 is illuminated by incident photons. Dielectric passivation layer 104 may act as an anti-reflective coating (ARC) layer for solar cell 100 as well as a passivation layer for the surface 105 of emitter region 102.
The efficiency of solar cell 100 may be enhanced by use of an ARC layer. When light passes from one medium to another, for example from air to glass, or from glass to silicon, some of the light may reflect off of the interface between the two media, even when the incident light is normal to the interface. The fraction of light reflected is a function of the difference in refractive index between the two media, wherein a greater difference in refractive index results in a higher fraction of light being reflected from the interface. An ARC layer disposed between the two media and having a refractive index whose value is between the refractive indices of the two media is known to reduce the fraction of light reflected. Hence, the presence of an ARC layer on a light-receiving surface of solar cell 100, such as dielectric passivation layer 104 on surface 105, reduces the fraction of incident radiation reflected off of solar cell 100 and which, therefore, cannot not be used to generate electrical energy.
When light falls on the solar cell, energy from the incident photons generates electron-hole pairs on both sides of p-n junction region 103. In a typical solar cell, which comprises an n-type emitter region and a p-type base region, electrons diffuse across the p-n junction to a lower energy level and holes diffuse in the opposite direction, creating a negative charge on the emitter and a corresponding positive charge build-up in the base. In an alternate configuration, which has a p-type emitter region 102 and n-type base region 101 (FIG. 1), electrons diffuse across the p-n junction to form a positive charge on the emitter and holes diffuse in the opposite direction to form a negative charge build-up in the base. In either case, when an electrical circuit is made between the emitter and the base, a current will flow and electricity is produced by solar cell 100. The efficiency at which solar cell 100 converts incident energy into electrical energy is affected by a number of factors, including the recombination rate of electrons and holes in solar cell 100 and the fraction of incident light that is reflected off of solar cell 100.
Recombination occurs when electrons and holes, which are moving in opposite directions in solar cell 100, combine with each other. Each time an electron-hole pair recombines in solar cell 100, charge carriers are eliminated, thereby reducing the efficiency of solar cell 100. Recombination may occur in the bulk silicon of substrate 110 or on either surface 105, 106 of substrate 110. In the bulk, recombination is a function of the number of defects in the bulk silicon. On the surfaces 105, 106 of substrate 110, recombination is a function of how many dangling bonds, i.e., unterminated chemical bonds, are present on surfaces 105, 106. Dangling bonds are found on surfaces 105, 106 because the silicon lattice of substrate 110 ends at these surfaces. These unterminated chemical bonds act as defect traps, which are in the energy band gap of silicon, and therefore are sites for recombination of electron-hole pairs.
As noted above, one function of the dielectric passivation layer 104 is to minimize the carrier recombination at the surface of the emitter region(s) 102 or the base region 101 over which the dielectric passivation layer 104 is formed. It has been found that forming a negative charge in a dielectric passivation layer 104 disposed over a p-type doped region formed in a solar cell device can help repel the carriers moving through the solar cell, and thus reduce the carrier recombination and improve the efficiency of the solar cell device. While it is relatively easy to form a passivation layer that has a net positive charge using traditional plasma processing techniques, it is difficult to form a stable negatively charged passivation layer on the surface of a silicon substrate.
Thorough passivation of the surface of a solar cell greatly improves the efficiency of the solar cell by reducing surface recombination. In order to passivate a surface of solar cell 100, such as surface 105, a dielectric passivation layer 104 is typically formed thereon, thereby reducing the number of dangling bonds present on surface 105 by 3 or 4 orders of magnitude. For solar cell applications, dielectric passivation layer 104 is generally a silicon nitride (SiXNY or abbreviated SiN) layer, and the majority of dangling bonds are terminated with silicon (Si), nitrogen (N), or hydrogen (H) atoms. But because silicon nitride (SiN) is an amorphous material, a perfect match-up between the silicon lattice of emitter region 102 and the amorphous structure of dielectric passivation layer 104 cannot occur. Hence, the number dangling bonds remaining on surface 105 after the formation of dielectric passivation layer 104 is still enough to significantly reduce the efficiency of solar cell 100, requiring additional passivation of surface 105, such as hydrogen passivation. In the case of multi-crystalline silicon solar cells, hydrogen also helps to passivate the defect centers on the grain boundary.
During normal processing of the solar cell device the p-type boron doped regions found in the solar cell may form an oxide layer, such as boron silicate glass (BSG) layer that is hard to remove prior to forming the dielectric passivation layer 104. The BSG oxide layer may be formed over the back side of a p-type substrate base region 101, or, alternately, the BSG layer may be formed over a p-type emitter structure. However, it is generally important to remove the formed oxide layer and clean the substrate surface to prevent contamination of the solar cell substrate during subsequent processing and improve the passivating effect of the dielectric passivation layer that is later formed over the substrate surface.
It is also desirable to assure that the solar cell efficiently converts as much of the optical energy received by the sun into electrical energy as possible. However, since sunlight may be scattered, refracted, diffracted, or reflected fairly easily, several different techniques have been developed to enhance light trapping in the solar cells to improve conversion efficiency. For example, a surface texture may be provided to increase the surface roughness, thereby assisting the light to be trapped and confined in the solar cell. Conventional surface texturing processes often utilize aqueous alcohol related compounds as a chemical source for substrate surface treatment. However, alcohol related compounds are flammable, which are fire hazard and be in environmental safety concern, thereby requiring special safety measures during processing. Also, alcohols evaporate at the temperatures needed to assure that the chemical activity of the etchants in the texturing solution is in an optimum range to effectively perform the texturing process. Evaporation of the alcohol components from the texturing bath thus leads to an unstable texturing bath composition when the processes are run at these elevated temperatures.
Therefore, there is a need for an improved method of cleaning a substrate prior to depositing a passivation layer, an improved method of forming a desirable charge at the surface of the solar cell device to minimize surface recombination of the charge carriers, and there is a need for a method to form a desirable surface texture on a surface of a solar cell to improve the formed cell's ability to trap incident light.

Method of cleaning and forming a negatively charged passivation layer over a doped region


A method and system are provided for managing memory to reassemble data packets received from different virtual channels in an ATM network. The method and system recognizes that both reliable and best effort traffic must be supported by a network interface. The system makes use of a virtual First-In-First-Out (FIFO) concept that partitions RAM memory space into multiple FIFO queues. The virtual FIFOs can have different sizes, and can be allocated to connections depending on quality of service requirements. A dedicated embedded controller 721 to provide flexibility is used in the system, as well as Content Addressable Memory (CAM) devices 723,724, and external logic. The method and system can also be applied at ATM transmitters in the implementation of congestion control algorithms.

Asynchronous Transfer Mode (ATM) networks provide integrated services having a wide range of bandwidths and holding times. ATM traffic can be subdivided into Constant Bit Rate (CBR) and Variable Bit Rate (VBR) traffic types. Each traffic type is supported by one or more ATM Adaptation Layers (AAL). AAL type 3, 4 or 5 protocols are employed for data packets or VBR traffic while AAL type 1 is used for CBR traffic.
The transport of packets across the network is accomplished by segmenting the data unit into cells, which are then transmitted to a destination. At the destination, reassembly of the packet is required before passing it to a receiving application. To accomplish the reassembly procedure, a memory addressing and management scheme is needed. For example, in a point-to-point transmission scenario, if consecutive cells belong to the same packet, reassembly can be achieved by storing cell payloads belonging to a packet in a memory space in a First In First Out (FIFO) manner. However, if packets are received from different virtual channels, having been multiplexed and switched through the network, cell interleaving occurs, and each virtual channel will require its own FIFO.
FIG. 1 illustrates cell interleaving in an ATM network. Stations A and B transmit information packets, which are carried in the network in the form of ATM cells marked A1, A2, A3 and B1, B2, B3, respectively. When these cells are transmitted through the network, they may be interleaved as shown. At the receive end, the packets must be reconstructed before being passed to applications running on Station C. As a result, reassembly typically requires two FIFOs (FIFO1 and FIFO2) each dedicated to a given virtual channel.
Different approaches have been attempted to solve the reassembly problem of interleaved cells. One solution is to realize that packets are generated and received by host computers, and therefore it is possible to share the host's physical memory space. Thus, one can use the host's operating system to manage the incoming packet information. This solution requires that the applications running on a given platform share the host's physical memory space with the network. As a result, depending on the network load, applications running on a given platform may experience performance degradation or if applications have priority over the network interface, the incoming data packets could be lost.
Another solution is to implement the reassembly function with dedicated hardware. This means reassembling packets in an external memory unit, which transfers packets to a host computer whenever a packet is successfully reconstructed. In the application noted above entitled "Method and Adaptor for Converting Data Packets Between First And Second Formats In A Data Transmission System", a hardware architecture uses linked lists to reconstruct incoming packets. A virtual channel queue holds partial data packets in a shared memory device. In one embodiment, the partial data packets destined for a common virtual channel are associated with a linked list data structure. In an alternate embodiment, a plurality of FIFO devices are used to store the addresses of successive partial packets.
Others have presented another technique by using the host's CPU cycles to control the linked list.
The above solutions are based on the assumption that best effort traffic transmission is required. This is an acceptable assumption since most of today's computer networks work under this constraint. In other words, these techniques might cause cell loss at the reassembly unit due to the nonavailability of memory space at high network throughputs. However, as new applications emerge with strict performance requirements (such as, for example, applications requiring distributed software processing, where the network transmission delay must be kept to a minimum for best performance results), a reliable transport mode must be supported. Furthermore, if multimedia stations are connected to the network, a need to handle AAL type 1 could arise, and a memory management architecture should be able to accommodate this traffic class.

Method for partitioning memory in a high speed network based on the type of service


A relay reset assembly for use with a relay including first and second support members and a bi-stable armature forming an armature bearing surface and carried by the first support member for pivotal movement between first and second stable positions when force is applied to the armature bearing surface, the assembly for resetting the armature in the first position after the armature is tripped into the second position, the assembly comprising an operator forming an operator bearing surface and carried by one of the first and second support members for movement between an activated position and a deactivated position and a push arm forming first and second arm bearing surfaces, the push arm carried by the second support member and juxtaposed such that each of the first and second arm bearing surfaces is proximate one or the other of the operator and armature bearing surfaces wherein, one of the first and second arm bearing surfaces engages one of the operator and armature bearing surfaces and the other of the first and second arm bearing surfaces engages the other of the operator and armature bearing surfaces when the armature is in the second position and the operator is moved from the deactivated position toward the activated position thereby applying force to the armature bearing surface, the one of the first and second arm bearing surfaces disengaging the proximate one of the operator and armature bearing surfaces when the armature has moved to the first position.

The present invention relates to electrical relays and more specifically to a bi-stable trip free relay resetting mechanism.
Overload relays are electrical switches typically employed in industry to protect equipment from excessive current conditions that in turn cause overheating, performance degradation and eventually equipment malfunction or destruction. For instance, a three phase induction motor is often linked to a power source through a relay commonly referred to as a contactor. A typical contactor includes a separate power path for each of the three motor phases. Contactor motion is typically provided magnetically as the result of power flow through a coil where the current though the coil is controlled by a control switch.
In many cases an overload relay is connected in series with the control switch for the contactor coil. When overload conditions occur, the overload relay opens thereby cutting off power to the contactor coil. When power to the coil is discontinued, the coil opens and power to the equipment is cut off.
Many overload relays have been designed such that, once tripped, the relay remains open to prevent current flow to the contactor until the relay is manually reset by a system operator. A common resetting device is a reset push button selectable by an operator to reset the relay thereby allowing current to flow to and to close the contactor coil which in turn provides current to the linked equipment.
For some applications industry standards require that re-settable relays be openable when overload conditions occur even if the reset button is continually inadvertently or manually held down. These overload relays that are openable even while the reset button is pressed are generally referred to as "trip free" relays and that term will be used hereinafter to refer to such configurations.
An exemplary trip free relay configuration includes a bi-stable armature that is operably linked to contacts to open a first set of contacts and close a second set of contacts when in a set position and to close and open the first and second sets when in a tripped position. Here, to reset the armature and hence the contacts after the relay trips, a button and a rigid linking member are provided where the rigid linking member is spring mounted to the armature and extends toward and contacts the button when the armature is in the tripped position. When the button is pressed, button force is transferred through the linking member to the armature thereby causing the armature to rotate toward the set position. The linking member is designed so that, as the armature approaches the set position, the linking member decouples from the button. If an over current condition occurs after the linking member decouples from the button and while the button is pressed, the relay can assume the tripped position again.
There are other advantageous features that may be included in a relay. For example, for test purposes, it is advantageous to provide a relay configuration where the relay can be manually tripped (i.e., a "manual trip" feature). As another example, it is sometimes advantageous to provide a relay where at least one of the normally closed relay contacts can be opened for a short period to momentarily interrupt power to linked equipment (i.e., an "open circuit" feature). As one other example, sometimes it is advantageous to provide a relay that can be automatically reset when overload conditions cease to exist (i.e., an "automatic reset" feature). A relay configuration including all of the features described (i.e., manual reset, manual trip, open circuit and automatic reset) above will be referred to hereinafter as a "fully featured" relay.
In addition to the mechanical components described above, a fully featured relay assembly also typically includes a printed circuit board (PCB) including control circuitry for tripping and automatically resetting the relay, current sensors and various types of terminals for linking to power lines, the contactor and perhaps indicating lights.
Past known mechanical trip free relay configurations have been designed to include a housing generally forming a single housing compartment or cavity including features for mounting all of the required trip free relay components. For instance, an exemplary known trip free housing assembly includes structure for mounting a trip free sub-assembly, a manual reset sub-assembly, an open circuit sub-assembly, the PCB, the current sensors and the connection terminals. Here it has generally been believed that a reduced parts count when a single housing was employed would result in reduced manufacturing costs.
While many of the features described above have been provided in relay configurations, unfortunately each known previous configuration has suffered from one or more shortcomings including excessive cost to configure and/or assemble, excessive space requirements and/or poor operating characteristics.


A ceramic pin heating element having exterior heating conductors and integrated electrical connection surfaces, and method for making same. A first body is injection molded from a first injection-moldable ceramic composite compound having a first electrical resistance, and a second body is injection-molded from a second injection-moldable ceramic composite compound having a second electrical resistance about the first body so as to form a compound body. The compound body is then sintered. The resulting ceramic pin heating element is directly formed without additional steps for protecting (insulating) the element so as to prevent the exterior, complementary heating conductors from contacting the housing and/or terminal bolts. The danger of breakage of the pins at the mounting location and/or at the seal seat through variations in the thickness of contact and/or insulation coatings is minimized.

The present invention relates to ceramic pin heating elements, and in particular, to a ceramic pin heating element for an internal combustion engine, the pin heating element having integrated connector contacts.
Connection of ceramic pin heating elements having exterior heating element shafts in a metal housing with simultaneous sealing from the combustion chamber is complex. The installation position causes contact between the heating element shafts having different polarity and the grounded housing. Therefore, to avoid short circuits, one of the two heating element shafts must be electrically insulated from the housing in the area of the seal seat. Also, the other heating element shaft, having opposite polarity, must be electrically insulated from the connector bolt. The application of electrical insulation layers is currently implemented through separate vitrification steps or through application, for example by printing, and burning-in of electrically insulating layers. To avoid one-sided mechanical stresses of the installed pin heating element due to the applied insulation layers, the corresponding open connector shaft is also provided with a layer of the same thickness but with electrical conductive properties, since there might otherwise be a danger of breakage of the ceramic pin heating element in the area of the seal seat. Another possibility is for the ceramic pin heating element to be fully insulated from the housing through application of a coating. As with a potential-free A-probe, contact is made through a divided terminal bolt.
The present invention provides a method for making a ceramic pin heating element having exterior conductors and integrated electrical connection surfaces. The method comprises injection molding a first body from a first injection-moldable ceramic composite compound having a first electrical resistance; injection molding a second injection-moldable ceramic composite compound having a second electrical resistance about the first body so as to form a compound body; and sintering the compound body.
The present invention also provides a ceramic pin heating element comprising a first body injection molded from a first injection-moldable ceramic composite compound, the first body having a first electrical resistance, and a second body injection molded from a second injection-moldable ceramic composite compound, the second body having a second electrical resistance. The first body and second body form a compound body, the compound body being sintered after injection molding of the first body and the second body.
A ceramic pin heating element according to an embodiment of the present invention has exterior heating conductors based on Si3N4/MSi2, where M is at least one of Mo, Nb, Ti and W, and has integrated electrical connection surfaces using multiple-component injection-molding technology.
An advantage of the method and heating element of the present invention is direct shaping of the pin heating element without additional steps for protecting (insulating) the element so as to prevent the exterior, complementary heating conductors from contacting the housing and/or terminal bolts. Another advantage according to the present invention is minimization of the danger of breakage of the pins at the mounting location and/or at the seal seat through variations in the thickness of contact and/or insulation coatings.

Ceramic pin heating element with integrated connector contacts and method for making same


A system for controlling a brake of a unit hauled by a work vehicle may generally include a valve assembly. When a speed of the work vehicle exceeds a predetermined speed threshold, the valve assembly may be configured to allow the brake to be actuated when first and second brake pedals of the work vehicle are depressed, either individually or simultaneously. However, when the speed of the work vehicle is less than the predetermined speed threshold, the valve assembly may only be configured to allow the brake to be actuated when both of the first and second brake pedals are depressed simultaneously.

A work vehicle, such as a tractor, typically includes two brake pedals, each of which is coupled to a corresponding brake cylinder or service brake for braking an associated wheel of the vehicle. For instance, the work vehicle may include a left brake pedal hydraulically connected to a left service brake for braking the left rear wheel of the vehicle and a right brake pedal hydraulically connected to a right service brake for braking the right rear wheel of the vehicle. In addition to the service brakes, the work vehicle may also include or be associated with additional brakes, such as one or more trailer brakes of a trailer or other unit being hauled by the vehicle.
In most conventional braking systems, the trailer brake(s) is coupled to the same hydraulic circuit as the service brake(s) to allow the trailer brake(s) to be actuated via depression of the brake pedal(s). As such, in instances when an operator depresses one of the brake pedals (e.g., the left brake pedal), the associated service brake (e.g., the left service brake) is actuated in combination with the trailer brake(s). Such simultaneous actuation of the trailer brake(s) with the service brake(s) may be advantageous when the work vehicle is travelling at relatively high speeds (e.g., when traveling along a road). However, when the work vehicle is traveling at relatively low speeds (e.g., when working in a field), it is often desirable to be able to steer the work vehicle by actuating one of the service brakes without actuating the trailer brake(s). Unfortunately, conventional braking systems do not provide for this functionality.
To address this lack of functionality, recent attempts have been made to allow for speed-based control of the trailer brake(s). For instance, international publication WO 2014/096156, entitled "A Brake System for Controlling a Brake of a Unit Hauled by a Vehicle" and assigned to CNH Industrial Italia SPA, discloses a braking system that utilizes an inverse shuttle valve in combination with a solenoid valve to provide speed-dependent control of one or more trailer brake(s). While this braking system represents a significant improvement over conventional systems, a need continues to exist for further refinements and improvements of existing braking systems to provide a cost-effective and efficient solution for providing speed-dependent control of the trailer brake(s) associated with a work vehicle.
Accordingly, an improved system and a related valve assembly for providing speed-dependent control of one or more trailer brakes of a hauled unit of a work vehicle would be welcomed in the technology.

System for providing speed-dependent control of a brake of a hauled unit of a work vehicle and related valve assembly


A method and apparatus for verifying stack size are disclosed wherein measured length and width dimensions of a stack of paperboard sheets are compared with length and width values of a label associated with the stack. The dimensions are typically measured as the stack travels along a conveyor. A no-match indicator is produced if there is not a match between the dimensions and values, and may include an alarm or a display on a video screen. The stack may be diverted to allow application of a correct label whereby the stack will be shipped to the correct customer.

1. Technical Field
The present invention relates generally to a method and apparatus for handling cardboard or paperboard materials. More particularly, the present invention relates to a method and apparatus for handling stacks of paperboard sheets. Specifically, the present invention relates to a method and apparatus for verifying the size of the paperboard sheets.
2. Background Information
Corrugators and other machines for producing and handling corrugated cardboard materials are well known in the art. Corrugators are used to form corrugated paperboard, which minimally includes a wavy or fluted paper known as a corrugated medium which is glued to a flat sheet typically called a liner. Corrugated paperboard can include one or more layers of the corrugated medium and one or more liners. Many boxes are formed of a single wall corrugated board, which is a corrugated medium glued between two flat liners. Corrugated paperboard also includes, for example, double wall corrugated boards and triple wall corrugated boards. The double wall corrugated board includes two layers of corrugated medium with three flat liners, and the triple wall corrugated board includes three layers of corrugated medium and four flat liners. Boxes may also be formed of the double wall and triple wall corrugated boards.
Once the given type of corrugated paperboard is formed by the corrugator, the corrugator or another machine typically cuts the corrugated paperboard into flat rectangular sheets, which are formed into a stack with multiple sheets atop one another. Due to the large variety in sizes of boxes, the length and width dimensions of these paperboard sheets varies correspondingly. A stacking device or stacker is configured to handle multiple different sizes of sheets in a relatively rapid fashion. Thus, the stacker may produce a batch of sheets each having the same dimensions whereby each of the stacks has the same dimensions, then produce a subsequent batch immediately thereafter in which the sheets and stacks have dimensions which are different than the earlier batch. Normally, a stacker operator applies a run sheet or label to each stack which is supposed to correspond to the stack with regard to its dimensions and other relevant information. However, because the formation of the stacks is relatively rapid, and the change from a batch of stacks having a first size to a second batch of stacks having a second size likewise occurs relatively rapidly, it is easy for the stacker operator to inadvertently place the wrong run sheet or label on the stack. If this mistake is not caught and corrected, the incorrectly labeled stack may be shipped to the wrong customer. Thus, there is a need in the art for a method and apparatus for verifying the stack size and ensuring that the proper label is applied so that the stack is shipped to the correct customer. The present invention achieves this goal.

Method and apparatus for verifying stack size


Provided is a method of forming optical waveguide. The method includes forming a trench on a semiconductor substrate to define an active portion, and partially oxidizing the active portion. An non-oxidized portion of the active portion is included in a core through which an optical signal passes, and an oxidized portion of the active portion is included in a cladding.

The present invention disclosed herein relates to a method of forming semiconductor integrated circuit, and more particularly, to a method of forming optical waveguide, which can transfer an optical signal.
Recently, due to the highly-developed semiconductor industry, requirements are gradually increasing for the lightening, high-integrating and/or speeding up of a semiconductor integrated circuit. However, owing to various factors, it gradually becomes difficult to satisfy requirements for the semiconductor integrated circuit. For example, the signal transfer speed between the internal devices of the semiconductor integrated circuit or between the semiconductor integrated circuits may be reaching the limit because of a communication speed limit by an electric wire and/or heating.
As one method for solving this, a research is being actively made on optical communication and/or optical interconnection. That is, many researches are being made on a technology that replaces a signal between the semiconductor integrated circuits, a signal between the semiconductor integrated circuit and other electronic medium, and/or a signal between the internal devices of the semiconductor integrated circuit with an optical signal.
In such an optical communication and/or optical interconnection field, the optical signals may be transferred through an optical waveguide. In the optical waveguide transferring the optical signal, it may be required to decrease the loss of the optical signal. At present, many researches are being made on the optical waveguide that is suitable for the semiconductor integrated circuit and can decrease the loss of the optical signal.

Electronics and Telecommunications Research Institute


The present invention provides a magnetic recording medium, which comprises at least one magnetic layer where ferromagnetic powder and a binder are dispersed, and said magnetic layer is placed on a non-magnetic support, whereby said binder comprises a polyurethane resin obtained through reaction of polytetramethylene glycol and short-chain diol having cyclic structure or short-chain diol having a branched side chain containing two or more carbon atoms, said polytetramethylene glycol is contained in said polyurethane resin in an amount of 35 to 60 weight %, said short-chain diol is contained in said polyurethane resin in an amount of 10 to 40 weight %, and glass transition temperature of said polyurethane resin is within the range of 30xc2x0 C. to 120xc2x0 C.

The present invention relates to a magnetic recording medium, which has high electromagnetic transfer characteristics and high durability and comprises a magnetic layer having ferromagnetic powder and a binder dispersed in it, and the magnetic layer is placed on a non-magnetic support.
The magnetic recording medium is widely used in such applications as recording tape, video tape, floppy disk, etc. The magnetic recording medium comprises a magnetic layer having ferromagnetic powder and a binder dispersed in it, and the magnetic layer is laminated on a non-magnetic support.
The magnetic recording medium must be at high level in such characteristics as electromagnetic transfer characteristics, running durability, and running performance. Specifically, an audio tape for reproducing musical sound must have an ability to reproduce original sound with higher quality. A video tape must have high electromagnetic transfer characteristics such as high ability to reproduce original image or picture. The magnetic recording medium used in storage device of a computer must be able to perform high density recording with high reliability.
In addition to high electromagnetic transfer characteristics as described above, the magnetic recording medium must have good running durability. To ensure good running durability, abrasive material and lubricant are generally added in the magnetic layer.
Because of sliding and contact between the medium and a magnetic head in the device where the magnetic recording medium is used, low molecular components in the binder of the magnetic recording medium tend to migrate toward surface of the magnetic layer, and this often causes problem of magnetic head contamination when these components are attached on the magnetic head.
Contamination of the magnetic head causes deterioration of electromagnetic transfer characteristics. In particular, in the device for high density recording, number of revolutions of the magnetic head is high. In a digital video tape recorder, number of revolutions of the magnetic head is as high as 9,600 rpm, and this is much higher compared with 1,800 rpm of an analog video tape recorder for household use, and 5,000 rpm of a video tape recorder for business use. Sliding speed between the magnetic recording medium and the magnetic head is getting increasingly higher, and the magnetic head and the thin film head are designed in more and more compact size, and there are strong demands to minimize and to improve the problems of magnetic head contamination caused by components of the magnetic recording medium. Also, the magnetic recording medium used for high density recording to replace floppy disk must have high strength and high reliability.
To solve the above problems and to improve property, hard binder is used to increase hardness of the magnetic layer.
For example, according to JP-A-01263927, there are provided a first and a second magnetic layers, and a polyurethane resin comprising polyether polyol, which is selected from polyethylene glycol, polypropylene glycol or polytetramethylene glycol, is used in the first magnetic layer. However, the polyurethane resin is deposited on the surface of the second magnetic layer, and this leads to higher friction coefficient during running operation and to poor durability. Further, the polytetramethylene glycol given in the example is contained in an amount of 75 weight % or more and has low strength, and there is no description on simultaneous use with a short-chain diol.
JP-B-8260531 describes a polyurethane resin comprising polyol, which contains polytetramethylene glycol and polycaprolactone. The content of the short-chain diol is about 15 weight % when calculated from the example, and glass transition temperature (Tg) of the polyurethane resin is in the range of xe2x88x9210xc2x0 C. to +20xc2x0 C. This is lower than that of the product according to the present invention. The strength of the coating film is low, and this leads to poor durability.
Similarly, JP-A-61190717 describes a polyurethane resin, which comprises polyol containing polytetramethylene glycol and polycaprolactone and a low molecular diol of glycol ester of monohydrocarboxylic acid. This aims to obtain a product with high calender workability, and coating film is often fluidized and has low durability. There is no description on glass transition temperature (Tg). Tg of the polyurethane resin given in the example is determined as about xe2x88x9230xc2x0 C. Accordingly, the strength of the coating film is low, and durability is not satisfactory.
JP-A-08147670 describes a polyurethane resin, which comprises polyol and short-chain diol of 5 mol % or less or diamine and diisocyanate. The content of the polyol is 0 to 5 mol %, and the content of ether is low even when polytetramethylene glycol is used. Thus, it has low adsorbing property to the magnetic support, and dispersion property is not sufficient.
JP-A-08293115 (U.S. Pat. No. 5,702,821) describes the use of a polyurethane resin, which comprises a short-chain diol having cyclic structure in an amount of 17 to 40 weight % and a polyol having ether content of 1 to 5 mmol/g in the polyurethane resin in an amount of 10 to 50 weight %, but both dispersion property and smoothness are not sufficient.
As described above, the conventional type polyurethane resin used as a binder for the magnetic recording medium lacks flexibility and does not meet the requirements such as high dispersion property, smoothness and high glass transition temperature even when it is manufactured using polytetramethylene glycol and short-chain diol.
The present invention provides magnetic recording medium, which comprises at least one magnetic layer where ferromagnetic powder and a binder are dispersed, and the magnetic layer is placed on a non-magnetic support, whereby the binder comprises a polyurethane resin obtained through reaction of polytetramethylene glycol and short-chain diol having cyclic structure or short-chain diol having a branched side chain containing two or more carbon atoms, the polytetramethylene glycol is contained in the polyurethane resin in an amount of 35 to 60 weight %, the short-chain diol is contained in the polyurethane resin in an amount of 10 to 40 weight %, and glass transition temperature of the polyurethane resin is within the range of 30xc2x0 C. to 120xc2x0 C.
Also, the invention provides the magnetic recording medium as described above, wherein the short-chain diol having the cyclic structure is at least one of a group of bisphenol A, alkylene oxide addition product of bisphenol A, hydrogenated bisphenol A, alkylene oxide addition product of hydrogenated bisphenol A, cyclohexanedimethanol, or cyclohexane diol.
Further, the invention provides the magnetic recording medium as described above, wherein the short-chain diol having a branched side chain containing two or more carbon atoms is at least one selected from a group of 2-ethyl-1,3-hexanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-propyl-1,3-propanediol, 2,2-dipropyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, and 2,2-dibutyl-1,3-propanediol.
Also, the present invention provides a magnetic recording medium, which comprises a lower layer having ferromagnetic powder or inorganic powder and a binder dispersed in it and being placed on a non-magnetic support, and at least one layer of magnetic layers where ferromagnetic powder and a binder are dispersed, whereby at least one of the binder in the lower layer or in the magnetic layer contains the polyurethane resin described in claim 1.
Also, the invention provides the magnetic recording medium as described above, wherein the ferromagnetic powder comprises iron as main component, and the iron contains yttrium with Y/Fe ratio of 0.5 to 10 atomic %.
In the magnetic recording medium of the present invention, polyurethane resin having polytetramethylene glycol as a long-chain diol component is used as a binder in the magnetic layer or in the lower layer, and the content of the polytetramethylene glycol is decreased. By adequately combining the short-chain diol having cyclic structure, the short-chain diol having a branched side chain containing two or more carbon atoms, and an organic diisocyanate, polytetramethylene glycol having high breaking extension property and high glass transition temperature can be produced. As a result, a magnetic recording medium having strong and tough coating film capable to resist high-speed sliding can be prepared.
At the same time, by improving dispersion property of the ferromagnetic powder and the non-magnetic powder, it is possible to have the coating film with smooth surface and to produce the magnetic recording medium having high electromagnetic transfer characteristics.
Further, when it is applied in the lower layer of the multi-layer tape, the polyurethane is scarcely deposited on the surface of the upper layer, and durability can be improved.
As the short-chain diol having cyclic structure used as raw material for the polyurethane resin contained in the binder of the magnetic recording medium of the present invention, the following substances may be used: diol such as bisphenol A, hydrogenated bisphenol A, bisphenol S, bisphenol P, and ethylene oxide or propylene oxide of the above compound, or mixed addition product of ethylene oxide propylene oxide, diol such as cyclohexane dimethanol, cyclohexane diol, etc. or diol obtained by adding ethylene oxide, propylene oxide, or butylene oxide to dibasic acid such as phthalic acid, sulfo-isophthalic acid, etc.
More preferably, hydrogenated bisphenol A or ethylene oxide, or propylene oxide addition product of the hydrogenated bisphenol A may be used.
It is preferable that the short-chain diol having cyclic structure is contained in the polyurethane resin in an amount of 10 to 40 weight %. If it is contained in an amount of lower than 10 weight %, dynamic strength is decreased, leading to poor durability. If it is contained in an amount of more than 40 weight %, solubility to solvent is decreased, resulting in lower dispersion property. Also, the coating film becomes fragile, and durability is decreased.
It is preferable that the short-chain diol having a branched side chain containing two or more carbon atoms is contained in the polyurethane resin in the present invention in an amount of 10 to 40 weight %. If it is contained in an amount of lower than 10 weight %, dynamic strength is decreased, leading to poor durability. If it is contained in an amount of more than 40 weight %, solubility in solvent decreases, and dispersion property is also decreased.
As the short chain diol having a branched side chain containing two or more carbon atoms, the following substances may be used: 2-ethyl-1,3-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-butyl-1,3-hexanediol, 2-normalbutyl-2-ethyl-1,3-propanediol, 3-ethyl-1,5-pentanediol, 3-butyl-1,5-pentanediol, 3-propyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 3-octyl-1,5-pentanediol, 3-myristyl-1,5-pentanediol, 3-stearyl-1,5-pentanediol, 2-ethyl-1,3-propanediol, 2-ethyl-1,5-pentanediol, 2-ethyl-1,6-hexanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-propyl-1,3-propanediol, 2,2-dipropyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, or 2,2-dibutyl-1,3-propanediol.
Among these substances, it is more preferable to use 2-ethyl-1,3-hexanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-propyl-1,3-propanediol, 2,2-dipropyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, or 2,2-dibutyl-1,3-propanediol. These substances can be expressed by the following formulae:
Among these substances, it is more preferable to use 2-ethyl-2-butyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, or 2,2-dibutyl-1,3-propanediol.
The number of the carbon atoms in the branched carbon chain is preferably 2 to 10, or more preferably 2 to 6. If it is lower than 2, solubility in solvent is lowered, and dispersion property is decreased. If it is more than 10, solubility in solvent is also decreased, and the dispersion property is lowered.
The polytetramethylene glycol used as the long-chain polyol is contained in the polyurethane resin preferably in an amount of 35 to 60 weight %, or more preferably in 40 to 50 weight %. If its content is lower than 35 weight %, solubility in solvent is decreased and dispersion property is also decreased. If its content is more than 60 weight %, the strength of the coating film is decreased, leading to poor durability. Weight average molecular weight of the polytetramethylene glycol is preferably 500 to 5,000, or more preferably 1,000 to 3,000.
As the organic diisocyanate used together with the polytetramethylene glycol, the short-chain diol having cyclic structure, or the short-chain diol having the branched side chain, the following compounds may be used: aromatic diisocyanate such as 2,4-tolylene-diisocyanate, 2,6-tolylene-diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, 4-4xe2x80x2-diphenylmethane-diisocyanate, 4,4-diphenylether-diisocyanate, 2-nitrodiphenyl-4,4xe2x80x2-diisocyanate, 2,2xe2x80x2-diphenylpropane-4,4xe2x80x2-diisocyanate, 4,4xe2x80x2-diphenylpropane-diisocyanate, m-phenylene-diisocyanate, p-phenylene-diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3xe2x80x2-dimethoxydiphenyl-4,4xe2x80x2-diisocyanate, etc., aliphatic diisocyanate such as tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, etc. or cycloaliphatic diisocyanate such as isophorone-diisocyanate, hydrogenated tolylene-diisocyanate, hydrogenated diphenylmethane diisocyanate, etc.
It is preferable to use aromatic diisocyanate, or more preferably 4,4-diphenylmethane diisocyanate, 2,2-tolylene diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate.
Weight average molecular weight (Mw) of the polyurethane resin used in the magnetic recording medium of the present invention is preferably 30,000 to 70,000, or more preferably 40,000 to 60,000. If it is less than 30,000, strength of the coating film is decreased, leading to poor durability. If it is more than 70,000, solubility in solvent is lowered, leading to poor dispersion property.
Glass transition temperature (Tg) of the polyurethane resin used in the magnetic recording medium of the present invention is preferably 30xc2x0 C. to 120xc2x0 C., or more preferably 50xc2x0 C. to 90xc2x0 C. If it is lower than 30xc2x0 C., strength of the coating film is decreased at high temperature, thus resulting in lower durability and storage property. If it is higher than 120xc2x0 C., calender workability is decreased, leading to poor electromagnetic transfer characteristics.
It is preferable that the polyurethane resin contains a polar group. As the polar group of the polyurethane, xe2x80x94SO3M, xe2x80x94OSO3M, xe2x80x94PO3M2, or xe2x80x94COOM are preferably used, or more preferably, xe2x80x94SO3M or OSO3M. It is preferable that the content of the polar group is 1xc3x9710xe2x88x925 eq/g to 2xc3x9710xe2x88x924 eq/g. If it is less than 1xc3x9710xe2x88x925 eq/g, adsorption to magnetic substance becomes insufficient, and this leads to poor dispersion property. If it is more than 2xc3x9710xe2x88x924 eq/g, solubility in solvent is decreased, leading to poor dispersion property.
The content of OH groups in the polyurethane resin exerts influence on physical property of the binder to be obtained. Preferably, 2 to 20 OH groups are contained per molecule in the polyurethane resin, or more preferably 3 to 15 groups per molecule.
If it is less than 3 groups per molecule, reactivity with isocyanate curing agent is decreased, and this reduces the strength of the coating film and leads to poor durability. On the other hand, if it is 15 groups or more per molecule, solubility in solvent decreases, leading to poor dispersion property.
As the ferromagnetic powder, Fe, Fexe2x80x94Co, Fexe2x80x94Ni, or Coxe2x80x94Nixe2x80x94Fe containing yttrium may be used. The content of yttrium in the ferromagnetic powder is preferably such that the ratio of yttrium atoms to iron atoms (Y/Fe) is 0.5 to 20 atomic %, or more preferably 5 to 10 atomic %. If it is lower than 0.5 atomic %, it is not possible to have ferromagnetic powder with higher "sgr" s value. As a result, magnetic characteristics decrease, leading to poor electromagnetic transfer characteristics. If it is higher than 20 atomic %, the iron content is decreased. This leads to lower magnetic characteristics and poor electromagnetic transfer characteristics. Further, any of the following elements may be contained within the range of not more than 20 atomic % to 100 atomic % of iron: aluminum, silicon, sulfur, scandium, titanium, vanadium, chromium, manganese, copper, zinc, molybdenum, rhodium, palladium, gold, tin, antimony, boron, barium, tantalum, tungsten, rhenium, gold, lead, phosphorus, lanthanum, cerium, praseodymium, neodymium, tellurium, bismuth, etc. Also, the ferromagnetic metal powder may contain small quantity of water, hydroxide or oxide.
In the ferromagnetic powder of the present invention, in addition to yttrium, elements such as neodymium, samarium, praseodymium, lanthanum, etc. may be introduced. These can be introduced using chloride such as yttrium chloride, neodymium chloride, samarium chloride, praseodymium chloride, lanthanum chloride, etc. or nitrate such as neodymium nitrate, gadolinium nitrate, etc. Two or more types of these compounds may be simultaneously used.
There is no special restriction on the shape of the ferromagnetic powder. In general, the ferromagnetic powder in needle-like, particulate, cubic, grain-like or planar shape may be used. In particular, it is preferable to use needle-like ferromagnetic powder.
The resin components, the curing agent, and the ferromagnetic powder as given above are kneaded and dispersed together with methylethylketone, dioxane, cyclohexanone, ethyl acetate, etc. used in the preparation of magnetic coating material, and a magnetic coating material is prepared. The kneading and dispersing may be performed according to the procedure commonly known.
The magnetic coating material may contain, in addition to the components given above, abrasive material such as xcex1xe2x80x94Al2O3, Cr2O3, etc., anti-static agent such as carbon black, lubricant such as fatty acid, fatty acid ester, silicone oil, etc., or additive or filling agent normally used such as dispersing agent.
Next, description will be given on the lower non-magnetic layer or the lower magnetic layer in case the medium of the present invention is designed in multi-layer structure. Inorganic powder in the lower layer in the present invention may be magnetic powder or non-magnetic powder. For example, in case of non-magnetic powder, inorganic powder can be selected from inorganic compound such as metal oxide, metal carbonate, metal sulfate, metal nitride, metal carbide, metal sulfide, etc. As the inorganic compounds, the following substances are used in combination or alone: For example, xcex1-alumina with alpha ratio of 90%-100% or more, xcex2-alumina, xcex3-alumina, silicon carbide, chromium oxide, cerium oxide, xcex1-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, etc. In particular, it is preferable to use titanium dioxide, zinc oxide, iron oxide or barium sulfate, or more preferably titanium dioxide. Average particle size of the non-magnetic powder is preferably in the range of 0.005 to 2 xcexcm. When necessary, non-magnetic powder with different average particle sizes may be mixed together or similar effect can be provided with single type of non-magnetic powder by widening the particle size distribution. In particular, it is preferable that average particle size of the non-magnetic powder is 0.01 to 0.2 xcexcm. It is preferable that pH value of the non-magnetic powder is within the range of 6 to 9. Specific surface area of the non-magnetic powder is preferably 1 to 100 m2/g, or more preferably 5 to 50 m2/g, or most preferably 7 to 40 m2/g. Crystallite size of the non-magnetic powder is preferably 0.01 to 2 xcexcm. Oil absorption using DBP is preferably 5 to 100 ml/100 g, or more preferably 10 to 80 ml/100 g, or most preferably 20 to 60 ml/100 g. Specific gravity is preferably 1 to 12, or more preferably 3 to 6. The shape may be any of needle-like, spherical, polyhedron, or planar shape.
It is preferable that surface of the non-magnetic powder is processed by surface treatment using Al2O3, SiO2, TiO2, ZrO2, SnO2, Sb2O3, or ZnO. To ensure better dispersion property, it is preferable to use Al2O3, SiO2, TiO2 or ZrO2, or more preferably Al2O3, SiO2 or ZrO2. These substances may be used in combination or alone. According to each individual purpose, coprecipitated surface treatment layer may be used, or a method to treat the surface layer using silica after treating with alumina, or a method reversing this procedure may be adopted. The surface treatment layer may be porous according to the purpose. In general, it is preferably homogeneous and dense.
By mixing carbon black in the lower layer, it is possible to decrease the value of Rs as the effect already known and to attain micro Vickers hardness as desired. For this purpose, furnace black for rubber, thermal black for rubber, carbon black for color, acetylene black, etc. may be used.
Specific surface area of the carbon black is preferably 100 to 500 m2/g, or more preferably 150 to 400 m2/g. DBP oil absorption is preferably 20 to 500 ml/100 g, or more preferably 30 to 400 ml/100 g. Average particle size of the carbon black is preferably 5 to 80 xcexcm, or more preferably 10 to 50 xcexcm, or most preferably 10 to 40 xcexcm. In the carbon black, it is preferable that pH value is 2 to 10, moisture content is 0.1 to 10%, and tap density is 0.1 to 1 g/ml. Concrete examples of the carbon black to be used in the present invention are as follows: Blackpearls 2000, 1300, 1000, 900, 800, 880, 700, and Vulcan XC-72 (manufactured by Cabot), #3050B, #3150B, #3250B, #3750B, #3950B, #950, #650B, #970B, #850B, and MA-600 (manufactured by Mitsubishi Chemical Industry Co., Ltd.), Conductex SC, Raven 8800, 8000, 7000, 5750, 5250, 3500, 2100, 2000, 1800, 1500, 1255, and 1250 (manufactured by Columbia Carbon Co.), and Ketchenblack EC (manufactured by Akzo).
In the lower layer of the present invention, ferromagnetic powder may also be used. As the ferromagnetic powder, an alloy having xcex3-Fe2O3, Co-denatured xcex3-Fe2O3, or xcex1-Fe as principal component, or CrO2 may be used. In particular, it is preferable to use Co-denatured xcex3-Fe2O3. The ferromagnetic powder used in the lower layer of the present invention has preferably composition and performance characteristics similar to those of the ferromagnetic powder used in the upper magnetic layer. However, the performance characteristics may be varied in the upper and the lower layers as already known according to each individual purpose. For example, to improve long wavelength recording characteristics, it is desirable to set the value of Hc of the lower magnetic layer to a value lower than that of the upper magnetic layer. Also, it is more effective to set the value of Br in the lower magnetic layer to a value higher than that of the upper magnetic layer. Further, advantages can be provided by adopting a multi-layer structure as already known.
As binder, lubricant, dispersing agent, additive, solvent, dispersing method, etc. of the lower magnetic layer or the lower non-magnetic layer, those for the magnetic layer can be applied. In particular, for quantity and type of binder, and quantity and type of additive and dispersing agent, the technique already known for the magnetic layer may be applied.
The magnetic coating material prepared from the above materials is coated on the non-magnetic support, and a magnetic layer is formed.
As the non-magnetic support used in the present invention, polyethylene naphthalate, polyethylene terephthalate, polyamide, polyimide, polyamideimide, aromatic polyamide, polybenzoxydazole, etc. processed by biaxial stretching may be used. More preferably, polyethylene naphthalate or aromatic polyamide may be used. These non-magnetic supports may be processed in advance by corona discharge, plasma treatment, treatment to make more easily adhesive, heat treatment, etc. The non-magnetic support used in the present invention has preferably such surface smoothness that average surface roughness at central line is in the range of 0.1 to 20 nm under cut-off value of 0.25 mm, or more preferably in the range of 1 to 10 nm. It is also preferable that the non-magnetic support not only has lower average surface roughness at central line but also has no excessive projection of more than 1 xcexcm.
The magnetic recording medium of the present invention can be manufactured, for example, by the following method: On the surface of a non-magnetic support under running condition, a coating solution for the magnetic layer is coated so that thickness of the magnetic layer after drying will be within the range of 0.05 to 3.0 xcexcm, or more preferably 0.07 to 1.0 xcexcm. In this case, a plurality of magnetic coating materials may be coated in multiple layers sequentially or at the same time.
On the surface (where the coating material is not coated) of the non-magnetic support used in the present invention, a back-coating layer (backing layer) may be provided. The back-coating layer is a layer, which is produced by coating a coating material to form back-coating layer (i.e. a coating material where particulate components such as abrasive material, anti-static material, etc. and the binder are dispersed in an organic solvent) on the uncoated surface of the non-magnetic support.
An adhesive layer may be provided on the surface of the non-magnetic support coated with the magnetic coating material and also with the coating material to form back-coating layer.
The coating layer coated with the magnetic coating material is dried after magnetic field orientation processing is performed on the ferromagnetic powder contained in the coating layer of the magnetic coating material.
After it has been dried as described above, surface smoothening treatment is carried out on the coating layer. For the surface smoothening treatment, super calender roll is used, for example. By the surface smoothening treatment, the holes generated due to removal of the solvent during drying are eliminated, and filling ratio of the ferromagnetic powder in the magnetic layer is improved. This makes it possible to obtain a magnetic recording medium having high electromagnetic transfer characteristics.
As the calender processing roll, heat-resistant plastic roll made of epoxy, polyimide, polyamide, polyamideimide, etc. is used. Or, a metal roll may be used.
It is preferable that the magnetic recording medium according to the present invention has surface with such good smoothness that average roughness along the central line of the surface is preferably within the range of 0.1 to 4 nm under the cut-off value of 0.25 mm, or more preferably within the range of 1 to 3 nm. To attain such surface smoothness, calender treatment is performed on the magnetic layer, which is formed by selecting specific types of the ferromagnetic powder and the binder as described above. The conditions for the calender treatment are as follows: Temperature of calender roll is preferably within the range of 60 to 100xc2x0 C., or more preferably 70 to 100xc2x0 C., or most preferably 80 to 100xc2x0 C. Pressure is preferably within the range of 100 to 500 kg/cm2, or more preferably 200 to 450 kg/cm2, or most preferably 300 to 400 kg/cm2.
The laminated substance processed by curing treatment as described above is cut into the shape as desired.
In the magnetic recording medium obtained as described above, the content of the polytetramethylene glycol is lower than that of the conventional type polyurethane resin. Also, by combining the short-chain diol having cyclic structure or the short-chain diol having branched side chain, it is possible to provide the polyurethane resin containing the polytetramethylene glycol with high breaking extension property. Because the content of the short-chain diol is higher than in the conventional type polyurethane resin, urethane bonding concentration is increased substantially and high glass transition temperature can be attained. This makes it possible to obtain strong and tough coating film capable to endure high-speed sliding operation. When it is applied in the lower layer of a multi-layer type, the polyurethane resin is scarcely deposited on the surface of the upper layer when the coating film is dried, and durability is improved.
(Embodiments)


A transparent overlay that can protect a document from tampering has a transparent cover sheet, a layer of hot-melt adhesive over one surface of the transparent cover sheet, and an image formed on the exposed face of said hot-melt adhesive layer. The transparent cover sheet can be a simple thermoplastic film but preferably is retroreflective sheeting which can bear a pattern or legend that is noticeable only when viewed retroreflectively.

1. Field of the Invention
The invention is concerned with transparent overlays to protect documents from tampering and is especially concerned with such overlays which contain patterns and legends that are difficult to counterfeit and thus also function to authenticate the documents.
2. Description of the Related Art
Documents often have adherent transparent overlays to provide protection against dirt, moisture, and general wear and tear. A typical transparent overlay has a plastic film bearing an aggressive adhesive layer by which it can be permanently adhered to the face of a document. When the plastic film incorporates a message such as a design that does not obscure the underlying information, a transparent overlay can afford an additional degree of protection, especially when the message-containing plastic film is difficult to remove without being destroyed and also is difficult to counterfeit. For example, many credit cards presently are made to exhibit holographic images which may be transparent but often are opaque and thus confined to an area not bearing information.
Even when the plastic film of an overlay is made to be too fragile to be removed as a single piece or, if removed, so contorted that it cannot be reapplied, a nagging concern remains that a clever, deft person might be able to remove it without undue damage (e.g., by the use either of hot or exceedingly cold temperatures) and to alter the face of the document (e.g., by replacing a portrait or photograph that identifies the bearer). Even when doing so would be discernible under expert examination, ordinary use of most documents usually precludes such an examination except under extraordinary circumstances. For example, when the document is a passport, a customs official rarely is allowed more than a minute or two to check both the document and its bearer unless there is some external evidence to suggest a more careful examination.
A transparent overlay which can contain a pattern or legend that does not obscure underlying information is disclosed in U.S. Pat. No. 3,801,183 (Sevelin et al.). That pattern or legend is invisible or only faintly visible to the naked eye under diffuse light and becomes readily legible only when viewed retroreflectively. Such overlays are currently manufactured and sold as CONFIRM brand security film by the Minnesota Mining and Manufacturing Company.
Because the CONFIRM brand security film is fragile and has a layer of an aggressive adhesive by which it can be bonded permanently to a document, it may be impossible to peel the sheeting from the document and reapply it without leaving readily noticeable evidence of tampering. Nevertheless, some issuers of documents request even greater assurance against tampering.
Subsequent to the aforementioned U.S. Pat. No. 3,801,183, a number of patents have issued disclosing other transparent overlays, each of which can be imaged with a pattern or legend that is noticeable only when viewed retroreflectively and can be adhesively bonded to a document without obscuring the face of the document. See, for example, U.S. Pat. No. 4,099,838 (Cook et al.), the overlay of which has the additional feature of causing the color of the reflection in the background areas to be different from the color of the reflection in the image areas. See also U.S. Pat. Nos. 4,688,894 (Hockert) and 4,691,993 (Porter et al.), each of which discloses a transparent overlay that functions in the same way as that of the Sevelin patent while having the added capability of permitting an authenticating message to be formed in the overlay after it has been adhesively bonded to a document. However, none of the transparent overlays of those three patents offers better assurance against unnoticeable tampering than does the overlay of the aforementioned U.S. Pat. No. 3,801,183 or the CONFIRM brand security film.

Transparent tamper-indicating document overlay


An impervious cable connected electrical component assembly is provided wh includes an electrical component which has a conductive wire extending therefrom. An impervious container is provided which has an open top and a closed bottom. The electrical component is located within the container with its conductive wire extending out of and beyond the container's top. A cable is provided which has a conductive wire within an impervious sheath. A lengthwise portion of this wire is exposed. The conductive wire extending from the top of the container and the exposed conductive wire portion of the cable are electrically joined at a junction outside the container. An impervious sleeve is bonded to the cable sheath so as to hermetically seal the wire junction along the cable. The open top of the container and the sleeve are bonded to hermetically seal the electrical component. With this arrangement the assembly can be easily constructed with minimal effect on the electrical component and, after construction, the assembly can be used with maximum protection of the electrical component.

The invention relates to an impervious cable connected electrical component assembly and the process of making such assembly.
Ocean data is frequently gathered by submerged sensors distributed along a cable. It is important that watertight integrity of each sensor be maintained so that signals from the sensor to the cable or vice versa are not shorted to the ocean water. A commonly used sensor is the hydrophone. Other sensors used are pressure transducers, accelerometers and/or thermistors. Recently the sensors have been combined with batteries, amplifiers and/or signal conditioning devices. Many of these sensors and devices are temperature and pressure sensitive. If the temperature or pressure gets too high during assembly these elements can be ruined or undergo calibration shifts.
By way of example, in an existing assembly, a cable that is hundreds of meters long has a multitude of distributed hydrophones attached to it. Each hydrophone is mounted as an appendage to the cable and is appropriately termed a "take out". Because these hydrophones are temperature and pressure sensitive great care must be taken in the process of attaching the hydrophones to the cable. Several construction methods are employed. After connecting the hydrophone to the cable, the connection and the hydrophone are encapsulated with a potting material, such as epoxy or polyurethane. These encapsulation materials are cured at room temperature and pressure. There are two serious problems with this process, namely: (1) long construction time and (2) insufficient watertight integrity of the hydrophone. The curing time of the encapsulation material can be as long as 24 hours for each hydrophone. It is not unusual to create an assembly in which dozens or more of hydrophones are attached to hundreds of meters or more of cable. The amount of labor and time to produce such an assembly can be readily appreciated. This can be aggravated when ventilation of the curing material is required for safety purposes. The other problem involving watertight integrity occurs because of a lack of sufficient bonding of the encapsulation material to the cable sheath. In the past the bonded materials were different, the cable sheath being Surlyn and the component encapsulation material being polyurethane. In the hydrophone application described above, once the bond breaks the hydrophone is rendered useless.

Impervious cable connected electrical component assembly

The United States of America as represented by the Secretary of the Navy


A vehicle sun visor includes an L-shaped rod fixed to the vehicle and a screen rotatably mounted on and slidable on the rod along a sliding direction parallel to a longitudinal axle thereof. The sun visor includes a detent clip coupled to the rod to establish controlled and stable predefined rotational positions of the screen defining at least a first screening position and an inoperative position. The visor further includes a carrier rotatably attached to the rod and housed in a guiding profile of the screen such that the screen is movable between two end positions of the sliding movement of the screen along the rod, defining two end positions. The carrier includes a rotary slider, a floating slider, and a metal spring elastically coupling the floating and rotary sliders. The carrier includes a first retention component engageable with a second retention component in the screen at one of the end positions.

Sun visors for vehicles sometimes incorporate a so called slide on rod (SOR) function which allows the sliding of the screen along the rod to provide an additional covering area when the sun-visor is placed at a lateral position, by the side window of the vehicle.
SOR sun visors comprise a carrier or slider that holds a detent clip that allows rotational movements to the screen around the rod, predefining at least a preferred angle position. The carrier is housed in an inner guiding channel of the screen that blocks the relative rotational movement between the carrier and the screen, but allows guided longitudinal movement such that the screen can slide over the carrier from a non-extended position to an extended position. The guiding channel can be provided by the inner structure of the screen in twinshell sun visors or by an additional guiding tube incorporated inside the screen.
The guided movement of the screen requires a free-play compensation between the carrier and the inner channel to assure a regular and steady effort for sliding the screen over the carrier.
It is also important to have a run-end retention of the guiding movement of the screen to provide some extra effort at the time of detaching from or clipping to one run-end position, to have a notice that the sun visor is at such run-end position.
It is known in the art the use of flexible plastic retention clips fitting in corresponding retention housings, placed in the slider and the screen respectively to provide a run-end retention of the sliding movement. The retention is obtained by the flexibility of the plastic retention means.
JP-2014-121919-A is an example of this kind of flexible retention. It describes a protuberance 220 comprising a hooking portion that engages and disengages with the engagement parts 16 and 17 of the slider. The protuberance 220 flexes and deforms, such that the restoring force in the engagement direction is imparted by the elasticity of the side face 103 of the screen, being noticed by the user.
WO-2014132569-A1 is another example of flexible retention. In this case the patent describes an engaging claw 36 which can be flexed in a direction orthogonal to the axial direction. The engaging claw 36 is engaged with the axial end portion 17f of the accommodating space 17 when the main body 22 abuts on the axial end of the accommodating space 17 by sliding the shield 16.
In U.S. Pat. No. 7,798,551-B2 the locked position is define by the sizes of the protrusions and engagement holes, defining with these dimensions the suitable insertion resistance, and fixing in this manner the sun visor body at both ends.
A first problem of these plastic clips working at flexion is that they suffer from permanent deformation, material ageing, and they are sensible to temperature, what means that it is not possible to guarantee its functional durability in all kind of conditions and through the time.
Furthermore, as the retention clips are arranged in the carrier and the housing are in the screen, any possible misalignment between the screen and carrier (due to free-play and manufacturing tolerances) provokes misalignments between the retention clips and their corresponding housings in the screen. This implies a variable retention force and the possibility of unexpected detachment or even a retention attachment not being possible, or even permanent damages.
To solve the problem of misalignment between the sun visor screen and the carrier, and the absorption of any free-play inside the guiding profile, in some sun visors the carrier comprises floating sliders which, in addition, improve the sliding efforts and noises.
One example of this is described in U.S. Pat. No. 8,905,457-B1 that describes a floating slider with means for limiting the stroke of the sliding movement, but no retention is used for maintaining the run-end position.
Another example of sun visor with a floating slider is described in U.S. Pat. No. 7,926,864-B2. In this case the sun visor also shows flexible retention means comprising flexible tongues 8 disposed in two plugs 7 at the ends of the guiding profile 4 for fitting in the corresponding engagements in the slider 2. This flexible retention means have the same problem described previously for the plastic clips working at flexion.

Vehicle sun visor with slide on rod function


The present disclosure relates to a method and system for recognition of data in one or more images. The method receives and segments the one or more images to identify segmented objects. Further, the method generates an object relationship data for each of the segmented objects and determines a knowledge base representation of the object relationship data based on defined features. Furthermore, a Recurrent Neural Network (RNN) is trained based on the knowledge base representation to determine an appropriate Neural Network (NN) having optimum confidence score. Based on the appropriate NN selected, the objects in the input image is predicted and transmitted to external systems for decision making. Thus, enabling accurate text/object identification for the images having different background variations using the dynamic selection of NN, thereby facilitating more effective decision making.

In current scenario, there are various techniques used for recognizing data such as text, objects in the images desired for a specific application. For example, in the case of automated bill processing systems, data such as bill details shall be recognized and extracted from the images of the bill. The images of the bill will have varying background such as white or color depending on the type of bill and the vendor. Conventional image processing techniques employ one type of approach for extracting the data from images. However, there may be multiple background variations in an image such that a single approach may not be sufficient for reading these varying background format images as each approach may be suitable for a particular background variation. For example, one approach using Open Computer Vision (OpenCV) is suitable for recognizing objects in white background images and another approach using Convolutional Neural Network (CNN) is suitable for images with colored background. Conventional techniques, fail to utilize multiple approaches for images to produce an overall accurate result under a given scenario. Further, conventional techniques fail to accurately determine data in images where there may be multiple background variations in a single image.

Method and a system for recognition of data in one or more images


A platen unit of a printer configured to perform printing while nipping and feeding a linerless label using a thermal head and a platen roller, the platen unit includes the platen roller, a downstream-side wraparound prevention member disposed on a downstream side of a feeding direction of the linerless label with respect to the platen roller, the downstream-side wraparound prevention member being configured to prevent the linerless label from rolling up to the platen roller, and an upstream-side wraparound prevention member disposed on an upstream side of the feeding direction of the linerless label with respect to the platen roller, the upstream-side wraparound prevention member being configured to prevent the linerless label from rolling up to the platen roller, wherein the upstream-side wraparound prevention member and the downstream-side wraparound prevention member are rotatably assembled to a roller shaft of the platen roller independently from each other.

In the prior art, a linerless label adapted to save resources has been employed as a band-shaped continuous label sheet. The linerless label does not have a liner sheet (release sheet) on which an adhesive layer on a back surface of a label substrate is temporarily attached.
A thermal printer 1 for such a linerless label has a feeder unit 3 of a linerless label 2, a detection unit 4, and a print unit 5 as illustrated in FIG. 10.
The linerless label 2 is wound in a roll shape and is loaded on the feeder unit 3. As illustrated in the partially enlarged view of FIG. 10, the linerless label 2 has a band-shaped label substrate 7, an adhesive layer 8 formed on a back surface of the label substrate 7, an underlying heat-sensitive color developing layer 9 formed on a front surface of the label substrate 7, and an overlying release layer 10.
In this manner, since the release layer 10 is formed on top of the linerless label 2, the adhesive layer 8 comes into contact with the release layer 10 by winding the linerless label 2 in a roll shape. Therefore, even when a roll of the linerless label 2 is loaded on the feeder unit 3, it is possible to continuously feed the linerless label 2 without sticking between inner and outer layers.
The linerless label 2 continuously discharged from the feeder unit 3 is fed to the print unit 5 from the feeder unit 3. The detection unit 4 and a guide roller 11 that guides the linerless label 2 are provided in the middle of a feeding path of the linerless label 2 from the feeder unit 3 to the print unit 5.
The detection unit 4 has a mark sensor 12 such as a transparent optical sensor to detect a relative position of the linerless label 2 with respect to the print unit 5 by sensing a position detection mark (not shown) printed on the linerless label 2 in advance at a predetermined pitch.
The print unit 5 has a thermal head 13 and a platen roller 14. The linerless label 2 continuously discharged from the feeder unit 3 is fed to a gap between the thermal head 13 and the platen roller 14.
In the print unit 5, the linerless label 2 is nipped and fed by rotating the platen roller 14, and printing of predetermined contents is performed on a surface of the label substrate 7 by supplying data to a heating element 15 of the thermal head 13 and developing a heat-sensitive color developing layer 9 formed on the surface of the label substrate 7.
The linerless label 2 is cut out along a line of perforations (not shown) formed on the linerless label 2 at a predetermined pitch and is issued as a single tag of the linerless label 2A. Alternatively, the printed linerless label 2 may be cut out at a predetermined pitch using a cutter such as a movable blade or a fixed blade to issue a single tag of the linerless label 2A.
In the thermal printer 1 having such a configuration, a releasable material such as silicone rubber is used on the platen roller 14 coming into contact with the adhesive layer 8 of the back surface of the linerless label 2 to guarantee non-adhesiveness. In addition, a downstream-side wraparound prevention member 16 having non-adhesiveness similar to that of the platen roller 14 is provided in a downstream side of the feeding direction from the platen roller 14.
It is desirable to design a gap between the downstream-side wraparound prevention member 16 and the platen roller 14 as small as possible. Meanwhile, if the platen roller 14 is detachably installed considering maintainability, and the gap between the downstream-side wraparound prevention member 16 and the platen roller 14 is excessively small, the downstream-side wraparound prevention member 16 may interfere in installation or removal of the platen roller 14.
In this regard, a technique has been proposed, in which the downstream-side wraparound prevention member 16 is assembled with a platen bearing that rotatably supports the roller shaft 140 of the platen roller 14, and the platen bearing is detachably installed in the support member provided in a device housing as a fixing portion, so that the platen roller 14 and the downstream-side wraparound prevention member 16 are unitized into a single assembly, and the single assembly is detachably installed in the device housing (see JP 09-314948 A).
In the technique of JP 09-314948 A, a pair of notches are formed on an outer circumference of the platen bearing, and the downstream-side wraparound prevention member 16 is assembled with a pair of notches. In addition, the platen bearing is inserted into a concave portion of the support member and is fixed by rotating a pair of notches of the platen bearing in synchronization with the downstream-side wraparound prevention member 16.


A piston for an internal combustion engine may include a shaft. A dual-layer coating with an inner layer and an outer layer may be applied to the shaft. The inner layer may include organic binders and solid lubricants. The inner layer may also include hard material particles of at least one of tungsten disulphide (WS2), tungsten carbide (WC), silicon carbide (SiC), and aluminum oxide (Al2O3). The outer layer may include inorganic binders, may be air-hardening, and may have a lower wear resistance than the inner layer.

Coatings for ensuring run-in and emergency operation properties having a functional/gradual structure have been known for some time, and the composition of such coatings must strike a balance between friction-minimizing and wear-resistance properties. For this reason, highly wear-resistant components such as connecting rods in particular have carbon fibre-reinforced coatings, for example with a high roughness value, but this can be disadvantageous with respect to process monitoring. In addition, such hard carbon fibers have an abrasive effect on aluminium counterfaces, which can lead to undesirable polishing effects or the formation of grooves.
WO 2012/041769 A2 discloses a generic piston for an internal combustion engine having a shaft coating with a wear-resistant inner layer composed of a polymer matrix with ceramic particles dispersed therein, aramid fibers and/or carbon fibers and an outer layer composed of a polymer matrix with solid lubricants dispersed therein. The purpose is to provide a functional inner layer that is applied directly to the surface of the piston, as well as a wear-resistant outer layer (substrate layer) by means of which run-in behaviour and in particular scuff resistance are to be improved. The friction-minimizing coating is also intended to allow reduction of fuel consumption and CO2 emissions during operation of the internal combustion engine.
A further generic piston with a dual-layer shaft coating is known from EP 1 894 987 A1.
However, a drawback of the pistons known from the prior art is that production of the coatings is relatively energy-intensive.

Piston for an internal combustion engine with a shaft


A direct conversion radiation detector includes a detector body made from a direct conversion material, a plurality of segmented electrode members operatively coupled to a radiation-receiving side of the detector body and at least one electrode operatively coupled to a second side of the detector body. The radiation detector is configured such that received radiation is incident on the segmented electrode members. The radiation detector provides reduced polarization effects for a variety of high flux radiation detection applications.

Radiation detectors, e.g., detectors capable of detecting X-rays and/or gamma rays, have been developed over the years for a variety of applications, e.g., medical imaging and detection, non-destructive testing and security inspection. Some early detectors included a collimator, a scintillation crystal and a plurality of photomultiplier tubes (PMTs). To overcome some shortcomings associated with PMT detectors, direct conversion detectors have been developed. Direct conversion detectors are capable of operating in photon counting mode or current mode.
Direct conversion radiation detectors, e.g., radiation detectors using Cadmium Zinc Telluride (CZT) or some other direct conversion material, have been developed over the years for a variety of applications. Nearly all of the research on CZT has been devoted to photon counting applications. Typically, these photon counting applications use gamma sources with flux rates that range from 1 photon per second up to 105 photons per second. Some new photon counting applications are pushing the count rates over 106 counts per second. These high flux rate applications may use Bremstrahlung sources, such as conventional X-ray tubes. These sources typically supply much higher fluence than gamma sources, even at their lowest range of operation, which is in the range of 106 photons per second to up to 109 photons per second. What's more is that X-ray tubes are polychromatic sources that output a wide spectrum of energies which has a significant effect on how these photons interact with the detection material.
Direct conversion radiation detectors traditionally have been plagued by polarization effects for high count rates in photon counting mode and non-linear response in current mode. The cause of the polarization may be the result of one of the carriers, either electron or hole, having a significantly lower mobility(μ)-lifetime(τ) product (μτe—mu-tau electrons; μτh—mu-tau holes) than the other carrier. In a conventional direct conversion detector, the hole μτh can be one to two orders of magnitude less that the electron μτe.
For most conventional photon counting applications with moderate count rates, e.g., count rates of less than about 105 photons per second, polarization effects have been reduced to insignificant levels due to the extensive research that has been put into improving device fabrication techniques and carrier transport properties in the materials. Electron mobility-lifetime products of CZT, for example, have improved over two orders of magnitude over the last ten years (μτe≈7×10−3 cm2/volt). The hole mobility-lifetime product has improved over the years but still remains one to two orders of magnitude lower than μτe (μτh≈2×10−5 cm2/volt).
Hole trapping was still an issue for all photon counting applications until the recent advent of detector designs which are relatively immune to the hole motion. A detailed discussion of the "Small Pixel Effect" can be found in H. Barrett, J. D. Eskin, and H. B. Barber, Charge Transport in Arrays of Semiconductor Gamma-Ray Detectors, Physical Review Letters, vol. 75(1), p. 156, 1995.
With reference to FIG. 1, initial direct conversion radiation detectors 10 were configured as single elements having metallic "planar" contacts 12, 14 coated on both sides of the detector body 16 as shown in FIG. 1. A potential 18 is applied across these two contacts 12, 14 to establish an electric field in the bulk of the detector. This field is employed to cause the carriers to drift to their respective electrode. The carrier motion in the insulating bulk material induces a charge that is sensed in one of the electrodes connected to a charge amplifier.
Investigators noticed that for photons that deposit energy throughout the detector thickness, there was a very significant low energy tail in the measured pulse height spectra. Theory and knowledge was developed that showed that hole trapping was the cause of the tail. A Typical value for mean drift length of electrons at 1000V/cm field strength is about 2 cm, whereas, the mean drift length for holes at the same field strength is about 0.02 cm. This means that as gamma or photons interact within the detector bulk and electron-hole pairs are generated, electrons are easily swept across the full bulk of moderately thick detectors. Holes, however, have little chance of making it to their respective contacts and are usually trapped in various trap centers. With the holes trapped, the signal strength becomes dependent on the distance the electrons travel to the positive contact. This results in a depth of penetration dependent signal strength rather than just an energy dependent signal strength, which compromises the energy resolution.
As crystal growth and fabrication techniques improved, large single crystal detectors became available. For applications requiring spatial information (e.g. imaging) it became necessary to "pixelate" the detector, which meant that one large crystal could be partitioned into many sensing elements by applying an array of metallic contacts on one side of the detector. Investigator quickly noticed that pixilated devices had much better energy resolution than non-pixelated device. This phenomenon was analyzed and a theory was developed by Barrett, et al. based on the "weighting potential" concept that explained the phenomenon. The theory describes how when a detector is pixelated, and the pixel dimension is significantly smaller than the detector thickness, most of the signal induction occurs when the electrons drift in the vicinity of the pixel where the weighting field is relatively strong. The summary result is that photons or gammas can interact over a large range of depth in the detector and produce signals that have a reduced dependence on depth compared with a planar device. When the electron-hole pairs are generated, the holes are quickly trapped, but the electrons do not induce much charge at the positive contact until they get within the high weighting field region near the pixel contact where they induce most of their charge on the electrode.
With this knowledge, radiation detectors were designed with optimized ratios of pixel dimension to detector thickness to achieve improved energy resolution operating in this mode. These conventional direct conversion detectors were configured with a continuous planar cathode through which incoming photons or gammas enter the detector with the charge sensing done on the pixelated contact side. All of these architectures are irradiated from the planar side of the detector with the charge or current sensing electronics connected to the pixelated backside of the devices.
This standard small pixel mode of operation works quite well as long as the transit time is relatively short with respect to the number of events occurring per unit time. At low to medium count rates, it is typically observed in present day CZT material, that consistent pulse heights are observed over long periods of time. If trapped charge were not de-trapping at least an equilibrium rate at which new carriers were being trapped, internal fields would build up due to the accumulated charge of the trapped carriers that would polarize the bulk material. In the past, this was indeed the case for poor quality materials.
At high count rates, it is often observed in conventional detectors that the pulse height decreases with time. This is a strong indicator that traps are filling faster that they are emptying and reverse polarization is occurring. The polarization effectively reduces the field strength across the device that decreases the charge collection efficiency. This changes the signal output from the expected value and causes a non-linear response of the detector.
At very high count rates or rather high fluence, as is typical of X-ray applications with X-ray tube sources, significant decreases in signal strength occur in short time frames indicating severe polarization.

Radiation detector and detection method having reduced polarization