JP2000019565A - Liquid crystal display device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which hardly gives rise to the image persistence and after-images of display images occurring in internal residual voltages and a process for producing the same and to effectively decrease the image persistence and after-images of the display images occurring in the internal residual voltages even with a plasma address liquid crystal display device. SOLUTION: This liquid crystal display device includes a liquid crystal panel having a pair of substrates facing each other, a pair of liquid crystal alignment layers disposed on the inner side of a pair of these substrates, structures disposed on the inner side of these liquid crystal alignment layers and a liquid crystal layer consisting of liquid crystal regions in contact with these structures. The time constant τ2AL defined by the value of the product of the sheet resistance value RAL of the liquid crystal alignment layers and film capacitance CAL, is <=4000 seconds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device and a method for manufacturing the same. In particular, the present invention relates to a liquid crystal display device having a wide viewing angle characteristic, which is suitably used for a flat display such as a personal computer, a word processor, an amusement device, and a television device, and a display plate, a window, a door, and a wall using a shutter effect.

[0002]

2. Description of the Related Art Heretofore, the present inventors have proposed an ASM (Axially Symme
Research on the (tric Aligned Microcell) mode has been conducted.

[0003] The technology for producing the ASM mode is disclosed in
No. 301015, as described in JP-A-7-20728, etc., a convex structure is provided inside a pair of opposed substrates,
Next, a mixture of at least a liquid crystal and a polymer material is injected as a liquid crystal material between the substrates, and the liquid crystal molecules are axially symmetrical between the polymer walls by utilizing the phase separation between the liquid crystal and the polymer material. This is a technique for orienting. In the liquid crystal display device 60 according to this technology, as shown in FIG. 8A, a display medium including a liquid crystal region 68 and a polymer (polymer) wall 67 is disposed between substrates 61 and 62, The liquid crystal molecules 69 contained in 68 have an axis of symmetry 66
Has a structure that is axially symmetric with respect to. At the time of halftone display and black display, the inclination of the liquid crystal molecules changes as shown in FIGS. 8B and 8C, and the same display can be obtained in two directions A and B. In contrast, the conventional TN
In the mode, as shown in FIGS. 9A to 9C, there is a difference in the appearance of the liquid crystal molecules in the two directions A and B, which causes a poor viewing angle characteristic.

In the conventional ASM mode, the dielectric anisotropy △
A liquid crystal material having a positive ε is used. This display mode has excellent display characteristics in all directions because the liquid crystal molecules are axially symmetrically aligned, but requires a phase separation process that requires complicated temperature control to obtain the axially symmetric alignment of the liquid crystal molecules. . Furthermore, the obtained axisymmetric orientation is unstable, and there is a problem that the reliability of display quality is poor especially at high temperatures.

As a means for solving these problems, the present inventors have disclosed in Japanese Patent Application No. 8-341590 a dielectric anisotropy Δ △ between a pair of substrates provided with a convex structure wall. Has proposed a method of disposing a negative liquid crystal material and providing an alignment film having vertical alignment on the surfaces of both substrates in contact with the liquid crystal layer.
In the manufacture of the vertically aligned ASM mode liquid crystal display device, a phase separation step is not required, and a stable and uniform axially symmetric alignment can be obtained. Further, since this liquid crystal display device is normally black, high contrast display is possible.

Further, recently, as a candidate for realizing a large-sized liquid crystal display device, a plasma addressed liquid crystal display device has been receiving attention.

[0007]

In a conventional liquid crystal display device, when a driving voltage waveform on which a DC voltage is superimposed is applied to a liquid crystal cell, the internal DC voltage remains in the liquid crystal layer even after the application of the voltage is stopped. Residual (such voltage is referred to as “residual DC voltage” or simply “residual voltage”), and as a result, image sticking afterimage occurs. The cause of the internal residual DC voltage is a DC voltage charged in the liquid crystal alignment film or the like when a voltage is applied, and the formation of an electric double layer in the liquid crystal cell due to adsorption of ionic charges to the alignment film. No. In a liquid crystal display system such as a thin film transistor (TFT) drive system, the coupling capacitance between the gate and the source, the auxiliary capacitance, and the capacitance of the liquid crystal layer are related to the reduction in the pixel electrode potential. The residual DC voltage can be reduced by reducing the coupling capacitance between the sources and increasing the auxiliary capacitance. However, in an actual TFT panel, control of these capacitance values alone cannot sufficiently prevent the afterimage phenomenon. The plasma addressed liquid crystal display also has a problem of image sticking after printing, and no effective solution has been found.

The evaluation of the physical properties of the alignment film material itself is described in the 23rd Liquid Crystal Symposium (Tokyo), pp. 138-139, published on September 24, 1997. Here, in order to define the characteristics of the alignment film material, a liquid crystal cell shown in FIG.
The time constant τ is described by applying a multilayer dielectric model using an equivalent circuit as indicated by 0. However, the above document only mentions the relationship between the time constant of the alignment film and the offset voltage, and does not disclose or suggest the composite evaluation of the afterimage of the liquid crystal panel and the conditions required for the physical properties of these materials. Not.

Further, in a homeotropically-aligned liquid crystal device using a liquid crystal material having a negative Δ △ and a vertical alignment film, a larger residual DC voltage is observed than in a homogeneously-aligned liquid crystal device. The problem grows. In fact, in a liquid crystal device using a homeotropic alignment liquid crystal mode, after displaying a pattern such as a lattice pattern at room temperature for several minutes to several tens of minutes, the pattern is conspicuous for several minutes or more after the pattern is erased. In some cases, there is a need for improvement.

[0010] Further, as a method for reducing the influence of burn-in afterimages caused by afterimage charges staying at the interface of a substrate provided with a liquid crystal alignment film made of a perfect electrically insulating material, etc.
A technique characterized by providing a semiconductive layer is disclosed in JP-A-6-2586.
No. 63 or Japanese Patent Laid-Open No. 5-232459. However, these documents do not disclose or suggest specific numerical limitations on the physical properties of a liquid crystal alignment film, which is an essential constituent material for a liquid crystal display device. With such a technique, it is impossible to effectively improve the afterimage charge of the liquid crystal display device composed of the multilayer dielectric. Furthermore, these documents do not disclose or suggest a burn-in afterimage of a plasma-addressed liquid crystal display device.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a liquid crystal display device in which afterimages of a displayed image due to an internal residual voltage are less likely to occur, and a method of manufacturing the same. More specifically, for example, an ASM mode, a vertical alignment type ASM mode using a liquid crystal material having a negative Δ △ and a vertical alignment film,
Another object of the present invention is to provide a plasma addressed liquid crystal display device in which the afterimage of a display image caused by an internal residual voltage is effectively reduced.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a liquid crystal display device in which an afterimage of a display image due to an internal residual voltage is hardly generated. A display device is provided.
The present inventors have paid attention to the relationship between the physical constants of the liquid crystal alignment film and the liquid crystal material formed between a pair of substrates, and as a result of diligent research, have found that a specific physical It has been confirmed that the above problems can be solved by defining the internal parameters to reduce the internal residual voltage, and the present invention has been completed.

A liquid crystal display device according to the present invention comprises a pair of opposing substrates each provided with a liquid crystal alignment film, a structure disposed between the pair of substrates, and a liquid crystal region in contact with the structure. A liquid crystal panel having a liquid crystal layer comprising
The time constant τ _AL defined by the product of the sheet resistance value R _AL and the film capacitance C _AL of the liquid crystal alignment film is 4000 seconds or less.

[0014] In a preferred embodiment, the membrane capacitance C _AL of the liquid crystal alignment film is 5NF～200nF.

[0015] In a preferred embodiment, the residual DC voltage value of the liquid crystal layer is 100 mV or less.

In a preferred embodiment, the measured ion density of the liquid crystal panel is 5 μC or less.

In a preferred embodiment, the liquid crystal composition of the liquid crystal layer has negative dielectric anisotropy, and the liquid crystal alignment film has vertical alignment.

In a preferred embodiment, a phase difference compensating element is further provided on at least one surface of the pair of substrates.

In a preferred embodiment, in the liquid crystal display device, a transparent electrode is provided on at least one of the pair of substrates, and a transparent electrode protective film is provided between the transparent electrode and the liquid crystal alignment film. Wherein the transparent electrode protective film has a volume resistivity of 10 ⁷ to 10 ¹⁴ Ω · cm.

In a preferred embodiment, the transparent electrode protective film contains conductive fine particles.

In a preferred embodiment, the structures are arranged axially symmetrically, and the liquid crystal molecules in the liquid crystal region are oriented axially symmetrically.

In a preferred embodiment, the liquid crystal layer is a polymer of a mixture of a liquid crystal composition, a polymerizable material in an amount of 0.1 to 10% by weight based on the liquid crystal composition, and a polymerization initiator.

In a preferred embodiment, the liquid crystal region is arranged in a plurality of regions regularly divided by a structure corresponding to a pixel region which is a minimum unit for performing display.

The plasma addressed liquid crystal display device of the present invention is defined in a space surrounded by a plurality of partition walls and a dielectric sheet provided substantially in parallel, has a discharge electrode therein, and has a gas generating plasma. A plasma substrate having a plurality of discharge spaces filled with, a counter substrate having a plurality of data electrodes provided in a direction perpendicular to the discharge space, and a counter electrode disposed between the plasma substrate and the counter substrate. A liquid crystal layer comprising a structure and a liquid crystal region in contact with the structure; and a liquid crystal alignment film provided on the liquid crystal layer side of the plasma substrate and the counter substrate, and a sheet resistance value R of the liquid crystal alignment film. _The time constant τ _AL defined by the value of the product of _AL and the film capacity C _AL is 4000 seconds or less.

[0025] In a preferred embodiment, the membrane capacitance C _AL of the liquid crystal alignment film is a 5NF～200nF.

In a preferred embodiment, the liquid crystal layer has a residual DC voltage value of 100 mV or less.

In a preferred embodiment, the dielectric sheet has a volume resistivity of 10 ⁷ to 10 ¹⁴ Ω · cm.

In a preferred embodiment, the plasma addressed liquid crystal display device further comprises a dielectric sheet protective film on the dielectric sheet in contact with the liquid crystal layer, wherein the dielectric sheet protective film has a volume resistance of 10%. ^{It is 7} to 10 ¹⁴ Ω · cm.

[0029] In a preferred embodiment, the thickness of the dielectric sheet protective film is in the range of 30 to 300 nm.

In a preferred embodiment, the dielectric sheet protective film has a function of suppressing transmission of ultraviolet light having a wavelength of 320 nm or less.

In a preferred embodiment, the liquid crystal composition of the liquid crystal layer has negative dielectric anisotropy, and the liquid crystal alignment film has vertical alignment.

In a preferred embodiment, the structures are arranged in an axially symmetric manner, and the liquid crystal molecules in the liquid crystal region are oriented in an axially symmetric manner.

In a preferred embodiment, the liquid crystal region is arranged in a plurality of regions regularly divided by a structure corresponding to a pixel region which is a minimum unit for performing display.

In the method for manufacturing a liquid crystal display device according to the present invention, a structure is formed on one substrate; and a sheet resistance R _AL and a film capacitance C _AL are formed on the substrate on which the structure is formed and the other substrate. Forming each of the liquid crystal alignment films with a predetermined thickness using a material having a time constant τ _AL defined by the value of the product of not more than 4000 seconds; and injecting a liquid crystal material between the bonded substrates. Forming a liquid crystal comprising the structure and a liquid crystal region in contact with the structure.

In a preferred embodiment, the liquid crystal material is a mixture of a liquid crystal composition, a polymerizable resin material, and 0.5 to 10% by weight of a polymerization initiator based on the polymerizable resin material. The method further includes a step of polymerizing the polymerizable resin material to orient the liquid crystal molecules in the liquid crystal region in an axially symmetric manner.

The plasma addressed liquid crystal display of the present invention
The manufacturing method includes forming a plurality of partition walls and a plurality of discharge electrodes on a substrate.
Provided substantially parallel to each other, by the partition and the dielectric sheet
Defining a discharge space having the discharge electrode therein;
The discharge space is filled with a gas that generates plasma,
Forming a zuma substrate; forming a structure on a counter substrate
A sheet on the plasma substrate and the counter substrate.
Resistance value R_ALAnd membrane capacity C _ALTime constant τ defined by the product of
_ALHowever, using a material that is 4000 seconds or less, the liquid crystal alignment film
Forming each with a predetermined thickness; the plasma substrate
A liquid crystal material is injected between the substrate and the counter substrate to
And forming a liquid crystal layer comprising a liquid crystal region in contact with the structure.
And the step of carrying out.

In a preferred embodiment, the method comprises:
The method further includes a step of applying and forming a dielectric sheet protective film having a volume resistivity of 10 ⁷ to 10 ¹⁴ Ω · cm on the dielectric sheet.

In a preferred embodiment, the liquid crystal material is a mixture of a liquid crystal composition, a polymerizable resin material, and 0.5 to 10% by weight of a polymerization initiator based on the polymerizable resin material. The method further includes a step of polymerizing the polymerizable resin material to orient the liquid crystal molecules in the liquid crystal region in an axially symmetric manner.

In a preferred embodiment, the step of polymerizing the polymerizable resin material further includes a step of irradiating the liquid crystal layer with ultraviolet rays in a direction perpendicular and / or oblique to the substrate surface of the plasma substrate. Include.

[0040] In a preferred embodiment, the step of polymerizing the polymerizable resin material further includes a step of irradiating the liquid crystal layer with diffuse ultraviolet rays.

Hereinafter, the operation of the present invention will be described.

In the liquid crystal cell, the afterimage phenomenon of a display image is a phenomenon in which the previous display remains faint even when the next display signal is selected due to the influence of residual charges. It is considered that the mechanism of the occurrence of these afterimages is that the adsorbed charges remain at the interface of the alignment film even after the voltage application is released, and an internal DC residual voltage is generated according to the pseudo electric field formed by the charges.
In order to suppress the occurrence of such an afterimage, it is extremely important to use a material that does not easily generate an internal residual voltage for the liquid crystal material and the alignment film material forming the liquid crystal layer. Usually, since the material of the alignment film has a larger specific resistance value than the material of the liquid crystal, the time constant τ at the time of charging and discharging becomes large, and an internal residual voltage is easily generated. Therefore, it is necessary to optimize the relationship between the time constants τ _LC and τ _AL of the liquid crystal material and the alignment film material. Specifically, τ _LC and τ _LC
In order to approach _AL , it is effective to set the time constant τ _AL of the alignment film material small. In the liquid crystal display device of the present invention, the time constant τ _AL defined by the product of the sheet resistance value R _AL and the film capacitance C _AL of the liquid crystal alignment film is 4000 seconds or less.
As described above, by optimizing the time constant of the liquid crystal alignment film to a specific range, a liquid crystal alignment film in which an internal residual voltage is unlikely to be generated is provided, and as a result, a good display quality in which the occurrence of an afterimage is reduced. Can be obtained.

In addition, physical values such as a film capacity, a residual DC voltage value, and an ion density of a liquid crystal panel are defined, and by optimizing these physical values, the afterimage of a display image due to an internal residual voltage is reduced. Further prevention can be achieved. In a preferred embodiment of the present invention, membrane capacitance C _AL of the liquid crystal alignment film, because it is 5NF～200nF, it is possible to match the dielectric constant of the liquid crystal layer and the alignment film layer, thereby a film surface The effect of generated charges can be reduced. In a preferred embodiment of the present invention, since the residual voltage value of the liquid crystal panel is 100 mV or less, the effect on the display afterimage of the liquid crystal panel can be ignored at a practical level. In a preferred embodiment of the present invention, since the measured ion density is 5 μC or less, the incorporation of impurities into the liquid crystal panel and the polarization of electric charges are reduced, thereby further preventing the occurrence of an afterimage. By combining these preferred embodiments, the occurrence of an afterimage can be more remarkably prevented.

In a preferred embodiment of the present invention, a transparent electrode is provided on at least one of the pair of substrates, and a transparent electrode protective film is further provided between the transparent electrode and the liquid crystal alignment film. The volume resistance value of the transparent electrode protective film is 10 ⁷
1010 ¹⁴ Ω · cm. By providing such a specific transparent electrode protective film, the liquid crystal panel has an insulating property that does not conduct between the upper and lower electrodes even if the liquid crystal alignment film is damaged by minute foreign matters mixed in the liquid crystal layer. In addition, it is possible to effectively remove charges generated and accumulated between layers or the like during manufacturing or driving without stagnation. In a further preferred embodiment, the transparent electrode protective film contains conductive fine particles. Since the transparent electrode protective film containing conductive fine particles and the like has a smaller surface resistivity than that of the liquid crystal alignment film, the charges accumulated and accumulated on the alignment film can be effectively reduced.

The present invention is similarly applied to a plasma addressed liquid crystal display. That is, by optimizing the time constant τ _AL defined by the product of the sheet resistance value R _AL and the film capacitance C _AL of the liquid crystal alignment film to 4000 seconds or less, the liquid crystal alignment film in which an internal residual voltage is unlikely to be generated. As a result, even in a plasma addressed liquid crystal display device, it is possible to obtain good display quality with reduced occurrence of burn-in afterimages.

Further, with respect to the plasma addressed liquid crystal display device, physical properties such as film capacity, residual DC voltage value, and ion density of the liquid crystal panel are defined, and these physical properties are optimized, and / or By optimizing the physical properties of the liquid crystal material and the alignment film material, and the physical properties of the dielectric sheet layer and the protective film, the image sticking phenomenon mainly caused by the charge remaining at the multilayer dielectric interface can be effectively prevented. It is possible to reduce to. In a preferred embodiment of the present invention, the dielectric sheet has a volume resistivity of 10 ⁷ to 10 ¹⁴ Ω · cm. By using a dielectric sheet having a volume resistance value optimized in this way, the liquid crystal panel is formed on the liquid crystal alignment film by fine foreign substances mixed in the liquid crystal layer, as in the case of the transparent electrode protective film. It has an insulating property to the extent that it does not conduct between the upper and lower electrodes even if it is scratched, and it is possible to effectively remove charges generated and accumulated between layers during manufacturing or driving without stagnation. In another preferred embodiment of the present invention, a dielectric sheet protective film is further provided on the dielectric sheet in contact with the liquid crystal layer, and the dielectric sheet protective film has a volume resistivity of 10 ⁷ to 1.
Since it is ¹⁴ Ω · cm, the same operation as in the case of the dielectric sheet can be obtained. In a further preferred embodiment of the present invention, by optimizing the thickness of the dielectric sheet protective film in the range of 30 to 300 nm, it is possible to prevent conduction between the electrodes causing display failure, and the above Can be sufficiently removed. In a preferred embodiment of the present invention, since the dielectric sheet protective film suppresses the transmission of ultraviolet light having a wavelength of 320 nm or less, the effect of shielding a small amount of ultraviolet light radiated from the discharge portion when plasma is generated can be sufficiently obtained. obtain. Further, by using the dielectric sheet protective film, a remarkable effect can be obtained in preventing damage to the panel due to fine dust and the like in the liquid crystal panel.

In another aspect of the present invention, a method for manufacturing a liquid crystal display device is provided. This method uses the sheet resistance R
Constant tau _AL time defined by the product of the values of _AL and the membrane capacitance C _AL is 40
Since the liquid crystal alignment film is formed using a material having a duration of 00 seconds or less, a liquid crystal alignment film in which an internal residual voltage hardly occurs is provided. Moreover, this method does not require complicated operations and special devices. Therefore, it is possible to provide a simple and low-cost liquid crystal display device having good display quality with reduced occurrence of burn-in afterimages. The manufacturing method of the present invention is similarly applied to a plasma-addressed liquid crystal display device, and can provide a plasma-addressed liquid crystal display device having good display quality with reduced occurrence of burn-in afterimages, simply and at low cost. . Further, in a preferred embodiment of the method for manufacturing a plasma addressed liquid crystal display device of the present invention, the dielectric sheet having a volume resistivity of 10 ⁷ to 10 ¹⁴ Ωcm is provided on the dielectric sheet in contact with the liquid crystal layer. Since the method further includes a step of coating and forming a sheet protective film, the resulting liquid crystal panel has an insulating property that does not conduct between the upper and lower electrodes even if the liquid crystal alignment film is damaged by fine foreign substances mixed in the liquid crystal layer. And it is possible to effectively remove charges generated and accumulated between layers or the like during manufacturing or driving without stagnation.

[0048]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

Embodiment 1 FIG. 1 schematically shows a liquid crystal display device according to an embodiment of the present invention. The liquid crystal display device 100 includes a liquid crystal panel 10, and retardation plates 11, 12 and polarizing plates 13, 14 outside the liquid crystal panel 10 as necessary. The liquid crystal panel 10 has a liquid crystal alignment film 4,
5, a pair of substrates 1 and 2 facing each other, and a liquid crystal layer disposed between the pair of substrates and including a structure 3 and a plurality of liquid crystal regions 8 in contact with the structure 3. are doing. Further, transparent electrodes (not shown) having a desired pattern are formed on the surfaces of the substrates 1 and 2 on the liquid crystal layer side, respectively. In this embodiment, the transmissive liquid crystal display device 100 has been described. However, when a reflective liquid crystal display device is configured, an opaque substrate such as a semiconductor substrate can be used as one of the substrates. Such a liquid crystal display device may have one liquid crystal region for each pixel region, and may have a plurality of liquid crystal regions for one pixel region when pixels have different vertical and horizontal pitches. good.

In one embodiment, the liquid crystal molecules in the liquid crystal region are twisted.

In another embodiment, the liquid crystal region may be composed of a liquid crystal composition having negative dielectric anisotropy, and may have a liquid crystal alignment film having vertical alignment. Conventionally, the liquid crystal composition of such a liquid crystal layer has a negative dielectric anisotropy,
And the liquid crystal display device in which the liquid crystal alignment film has a vertical alignment property,
There is a problem that the influence of the burn-in afterimage is greater than in the normal horizontal afterimage mode. However, when the present invention is applied to the liquid crystal display device of the present invention, it is possible to remarkably improve the problem of the afterimage.

In another embodiment, a polymer wall (polymer wall) may be provided near the structure 3, and the liquid crystal region 8 may be substantially surrounded by the polymer wall. Alternatively, the polymer wall may be formed so as to fill between the structure 3 (substantially the alignment film 4) and the substrate 1 (substantially the alignment film 5). Further, the liquid crystal molecules in the liquid crystal region may be oriented in an axially symmetric manner. Details of the axisymmetric orientation will be described later in section D of this specification.

A. Optimization of Physical Property Values of Liquid Crystal Material and Alignment Film Material The time constant τ is derived by the following equation. Here, the term “material” includes a liquid crystal material and an alignment film material.

[0054]

(Equation 1)

The time constant τ is a physical property value serving as an index when considering the magnitude of the internal residual voltage. Time constant τ of the above material
Can be estimated for the liquid crystal material and the liquid crystal alignment film material, respectively, and the time constant τ _LC of the liquid crystal material (ie, the liquid crystal layer) defined by the product of C _LC and R _LC , respectively,
By calculating the time constant τ _AL of the liquid crystal alignment film material (that is, the liquid crystal alignment film) defined by the product of C _AL and R _AL , it can be used as an index for material selection. As τ _LC approaches τ _AL , the internal residual voltage can be reduced. Specifically, to define small tau _AL, it is effective to further define which is one C _AL of the two factors that determine the time constant. The time constant τ _AL of the liquid crystal alignment film material is, for example,
Specific permittivity εr of alignment film material = 4, specific resistance value of alignment film material
(Volume resistance) When ρ = 1 × 10 ¹⁶ (Ω · cm), 3
It is calculated as 542 seconds.

B. Alignment film material As the alignment film material used for the alignment film of the liquid crystal display device of the present invention, any suitable organic material may be mentioned, for example, polyimide, polyamic acid derivative and the like. These alignment film materials may be used alone, but by appropriately combining them, the time constant τ _AL can be adjusted. Time constant τ _AL obtained by applying Equation 3
Is preferably 4000 seconds or less, and more preferably 500 seconds or less. By defining the time constant τ _AL in this manner, a material configuration in which an internal residual voltage is unlikely to be provided is provided, and the occurrence of an afterimage is reduced. Further, as the membrane capacitance C _AL obtained by applying the formula 1, 25 ° C., under measurement conditions of 0.01 Hz, are preferably 5NF～200nF, more preferably a 10NF～120nF. In principle, a smaller value of such a film capacitance is advantageous in designing the time constant obtained by the above equation, but the average dielectric constant of the liquid crystal material is generally smaller than that of the alignment film material. Therefore, it is necessary to match the dielectric constant of the liquid crystal layer and the alignment film layer in order to reduce the influence of charges generated at the film interface. For these reasons, the above-mentioned optimum range of the film capacity can be defined.

C. Liquid Crystal Panel Regarding the range of the residual DC voltage value of the liquid crystal panel, it is preferable that the residual voltage value is smaller as described above. That is,
After applying a voltage stress of 10V DC for 30 minutes at 25 ° C, 25 ° C
The residual DC voltage value evaluated in the above is preferably 100 mV or less, more preferably 80 mV or less. Residual DC
If the voltage value is larger than this value, the effect on the display afterimage of the liquid crystal panel cannot be ignored in practical use.

The measured value of the ion density of the liquid crystal panel is preferably 5 μC or less, more preferably 0.01 μC or less at 25 ° C. and 0.01 Hz. When the ion density is increased, the above-mentioned set value range is desirable, since it leads to generation of a burning afterimage due to incorporation of impurities into the liquid crystal panel and progress of polarization of charges.

In these liquid crystal cells, one frame (30H
(z; 16.67 milliseconds) The time constant τ is 1.658 seconds, assuming that 99% of the charge is held during the display, and the charge is 99.9%.
The time constant τ when it is assumed to be held is 16.58 seconds. It is important to optimize the physical properties of the constituent materials in order to reduce the influence of the electric charge generated by baking. On the other hand, the voltage holding ratio of the liquid crystal cell is preferably set to 95% or more in room temperature measurement in consideration of the influence of reliability and the like. FIG. 2 shows the relationship between the voltage holding ratio of the liquid crystal cell calculated based on the above assumption and the reciprocal of the time constant of the liquid crystal cell. As shown in FIG. 2, in order to obtain a high voltage holding ratio, a smaller time constant is better. FIG. 3 shows the relationship between the residual DC voltage (measuring temperature 70 ° C.) and the reciprocal of the time constant of the liquid crystal cell. From FIG. 3, it is necessary to set the time constant of the material small in order to reduce the residual DC voltage. In the liquid crystal cell, it is necessary to comprehensively optimize the above physical properties in order to reduce and improve the occurrence of burn-in afterimages and improve the display characteristics of the panel.

D. Liquid Crystal Material and Liquid Crystal Alignment State As the liquid crystal material used in the liquid crystal layer of the liquid crystal display device of the present invention, any appropriate organic mixture material exhibiting a liquid crystal state at around normal temperature can be mentioned, and a nematic liquid crystal is preferable. From the viewpoint that the contrast ratio of the display characteristics can be improved, an Nn liquid crystal material having a negative dielectric anisotropy Δε is preferable. The magnitude of the absolute value of Δε of the liquid crystal material can be appropriately set depending on the application. Generally, it is desirable to design a material having a large absolute value from the viewpoint of lowering the driving voltage, and preferably, the absolute value of Δε is about 1 to about 7
It is.

The d · Δn (retardation) of the liquid crystal layer when a voltage is applied is a factor that affects display characteristics such as transmittance and viewing angle characteristics of the liquid crystal panel. In the present invention, the range of the retardation design value is a product d · Δn of the refractive index anisotropy Δn of the liquid crystal molecules in the liquid crystal cell (the value at the maximum driving voltage) and the average cell thickness d of the liquid crystal layer. About 300-530 nm is preferred. For the purpose of panel design while maintaining the balance between viewing angle characteristics and LCD panel brightness, the first minimum condition (d フ ァ ー ス ト n is about 500n
It is effective to match with m). Further, the twist angle of the liquid crystal molecules in the liquid crystal layer is also a factor that affects the transmittance characteristics of the panel. In the present invention, the twist angle when the maximum driving voltage is applied is preferably 45 to 120 °, more preferably 90 °.
110110 °. When the twist angle deviates from this range, the brightness (transmittance) and viewing angle characteristics are often insufficient.

In the liquid crystal panel of the liquid crystal display device according to the present invention, the alignment state of the liquid crystal molecules in the liquid crystal region corresponding to the pixel is made axially symmetric (including radial alignment, concentric alignment, and multiple division alignment). The aim is to expand and improve the viewing angle characteristics in all directions by the internal compensation effect in the liquid crystal cell.

It is extremely effective to use a polymerizable resin material for the liquid crystal material in order to stabilize such a unique alignment state in the liquid crystal panel. Specifically, acrylate-based materials, methacrylate-based materials, styrene-based materials,
By regulating the alignment using a polymer obtained by polymerizing a material obtained by adding a photopolymerization initiator to a photopolymerizable resin material such as an α-methylstyrene-based material and a derivative thereof, the liquid crystal molecules can be axially symmetrically aligned. It is based on a method in which a pretilt is given to define a direction in which liquid crystal molecules fall when a voltage is applied. As the polymerizable material, a thermopolymerizable material can be used. In the case where a polymerizable resin material is used, the content of the polymerizable resin material contained in the liquid crystal material affects the degree of afterimage after printing. In order to reduce display afterimages and improve display performance, the polymerizable resin material should be contained in the liquid crystal material in a ratio of about 0.1 to about 10% by weight based on the liquid crystal composition in the liquid crystal material. Preferably, more preferably, about 2
~ 5% by weight. The content of the polymerizable resin material is about 0.
If the amount is less than 1% by weight, not only does polymerization not proceed sufficiently, but also the ability to regulate the direction in which the liquid crystal molecules respond depending on the magnitude of the voltage cannot be obtained. Therefore, when the application and non-application of the voltage are repeated, and / or at the time of halftone response, the response speed becomes extremely slow and a problem of display afterimage occurs. On the other hand, when the content of the polymerizable resin material is more than about 10% by weight, the crosslink density of the polymer increases, and the interaction between the liquid crystal molecules and the polymerization zone becomes very strong. Therefore, the orientation state of the liquid crystal molecules is restricted by the interaction, and the voltage response characteristics of the liquid crystal molecules are reduced.
The problem of afterimages occurs.

The effect of these polymerizable resin materials on image sticking after printing is that since the polymer is dispersed in the liquid crystal layer, the difference in the degree of interaction between the liquid crystal molecules and the polymer causes the image sticking phenomenon. Differences will be recognized.
In a device in which the alignment state of the liquid crystal region is fixed by using such a resin material, the lower the concentration of the polymerization initiator contained in the material, the lower the degree of burn-in afterimage. Here, when the concentration of the polymerization initiator is low, the progress of the polymerization reaction is slow, the degree of branching of the polymer is small, and the size of the network structure is large. On the other hand, when the reaction rate is high (the polymerization initiator concentration is high), the degree of branching of the polymer increases and the size of the mesh decreases. The smaller the size of the polymer network surrounding the liquid crystal molecules, the stronger the interaction between the liquid crystal molecules and the polymer. It is considered that the strength of the interaction is related to the degree of afterimage. That is, the stronger the interaction between the liquid crystal molecules and the polymer, the stronger the degree of afterimage. Therefore, the higher the polymerization initiator concentration, the stronger the afterimage. If the polymerization initiator concentration is extremely low, the polymerization reaction does not proceed sufficiently,
A certain level of concentration is required. The concentration of the polymerization initiator is preferably 1 to 5% by weight based on the polymerizable resin material mixed with the liquid crystal material.

E. Arrangement of Liquid Crystal Regions In a preferred embodiment of the present invention, a plurality of liquid crystal regions are arranged in a liquid crystal layer. In order to obtain uniform image display quality within the display surface, the liquid crystal region is regularly (for example,
(It is preferable that they are arranged in a matrix corresponding to the pixels.) Further, it is preferable that a plurality of regions are regularly separated by a structure from a pixel region which is a minimum unit for performing display. In this case, for example, it is more preferable that the residual DC voltage value of the liquid crystal panel is 100 mV or less and the measured ion density is 5 μC or less.

F. Retardation plate When a liquid crystal layer is formed on two orthogonal polarizing plates and observed by changing the applied voltage and the viewing angle, the following contrast reduction is confirmed. (i) Viewing angle characteristics due to the polarizing plate (ii) Light leakage due to viewing angle dependence of the retardation (d · Δn) of the liquid crystal layer These phenomena occur in the direction of 45 ° (azimuth;
(In the plane of the substrate).

When a normally black display mode is applied using an Nn liquid crystal material having a negative dielectric anisotropy (△ ε <0), high contrast with good black display in the front direction can be realized. Yes, but the above issues remain. In order to suppress this phenomenon, it is effective to design the retardation of a vertically aligned liquid crystal material to be small. Further, a retardation plate (a retardation compensator) composed of a refractive index ellipsoid having a refractive index nx>ny> nz (refractive index in a direction perpendicular to the display surface) in a display surface direction between the liquid crystal cell and the polarizing plate. Element) is preferably provided. More preferably, nx
The arrangement is such that the direction and the absorption axis of the adjacent polarizing plate are orthogonal to each other. The phase difference of the retardation plate is preferably smaller than the retardation value unique to the liquid crystal cell, which is obtained by the product of Δn unique to the liquid crystal material and the thickness d of the liquid crystal layer. A preferred range is approximately the retardation value specific to the liquid crystal cell.
The value is 30 to 80%, and more preferably 30 to 60%. If this value is smaller than 30%, the compensation effect of the retardation plate is small, and if it is larger than 80%, coloring becomes large in a wide viewing angle direction, which is not preferable for display. Further, the value of the in-plane retardation [(nx-ny) · df df; thickness of the retardation plate] of the retardation plate is preferably designed to be about 3.5 to 15%, more preferably 5 to 15%. It is.

G. Semiconductor protective film material If necessary, a semiconductive protective film (transparent electrode protective film) is provided between the substrate and the liquid crystal alignment film (more specifically, between the transparent electrode provided on the substrate and the liquid crystal alignment film). (Between). The volume resistance value of the semiconductive protective film is preferably 10 ⁷ to 10 ¹⁴ Ωcm,
More preferably, it is 10 ⁸ to 10 ¹³ Ω · cm. If the volume resistance of the protective film exceeds 10 ¹⁴ Ω · cm, it becomes difficult to remove charges generated and accumulated in the liquid crystal alignment film in a liquid crystal display device composed of various multilayer dielectric layers. On the other hand, when the volume resistance value of the protective film is less than 10 ⁷ Ωcm, the electrical insulation becomes insufficient, for example, conduction between adjacent electrodes and when the liquid crystal alignment film is damaged. Display defects are likely to occur due to short circuit between the upper and lower electrodes. According to the present invention, the volume resistance value of the protective film is 10
By defining the range of ^{7 ~10 14 Ω} · cm, the liquid crystal panel, an insulation resistance that even scratched the liquid crystal alignment film due minute foreign matters mixed in the liquid crystal layer does not conduct between upper and lower electrodes In addition, it is possible to effectively remove charges generated and accumulated between layers or the like during manufacturing or driving without stagnation. As a result, the semiconductive protective film layer improves display afterimage of the liquid crystal display device. Such a semiconductive protective film layer is suitably used as a dielectric sheet protective film in a plasma addressed liquid crystal display device described later.

The above protective film is formed from a protective film forming coating solution. This coating liquid for forming a protective film includes a matrix,
It includes conductive fine particles and additive fine particles. As the matrix, any suitable matrix (for example, a matrix containing silica oligomer or the like as a main component)
Is used. The conductive fine particles are not limited as long as they are conductive fine particles.Specifically, zinc oxide,
Tin oxide, indium oxide, antimony oxide, and S
Examples include tin oxide doped with b, F, P, and the like, and indium oxide doped with Sn, F, and the like. They are,
They can be used alone or in combination. Further, the conductive fine particles may be composite oxide fine particles such as TiO ₂ -SnO ₂ . The particle size of the conductive fine particles is preferably 20 nm or less. As the additive fine particles, TiO ₂ , Si is used in order to match the surface resistance value and to improve the adhesion between the organic film such as the liquid crystal alignment film and the protective film.
Inorganic compound fine particles such as O ₂ , Al ₂ O ₃ , and ZrO ₂ can be mixed alone or in combination.
A coating solution in which these fine particles are dispersed in a matrix solution using water and / or an organic solvent as a solvent is preferable. For example, a semiconductive protective film layer is formed by applying this coating solution for forming a film.
Coating on the surface of the substrate by dipping, spin coating, flexo printing, etc., drying at room temperature to around 90 ° C, curing of the binder matrix by irradiation with ultraviolet light, and baking at 200 to 350 ° C Can be formed.

H. Driving Method The liquid crystal display device of the present invention can be driven by various driving methods. That is, simple matrix drive, plasma address drive, a-Si (amorphous silicon) TFT (thin film transistor), p-Si (polysilicon) TFT, and MIM (Metal-Insu
It is possible to apply a driving method such as active matrix driving such as a lator-metal) element.

I. Manufacturing Method Hereinafter, an example of a manufacturing method of the above-described liquid crystal display device will be described.

First, a structure is formed on one of a pair of glass substrates having a transparent electrode or the like. This structure forming step is preferably performed by forming a pattern with a photoresist material including a spacer to form a patterning wall so that the liquid crystal region can be regularly arranged corresponding to the pixel region. Is done. Next, using a material having a time constant τ _AL defined by the product of the sheet resistance value R _AL of the alignment film and the film capacitance _CAL of 4000 seconds or less, the liquid crystal alignment film is formed to a predetermined thickness (for example, 50 μm). (About 130 nm) on both substrates. This liquid crystal alignment film can be formed by applying an alignment film material by any appropriate technique, performing a baking process, and performing an alignment process by rubbing or the like. This liquid crystal alignment film is
It may be formed of a material capable of vertically aligning liquid crystal molecules.
Next, the two substrates are bonded together with an appropriate sealant to form a liquid crystal cell, and a liquid crystal material is injected into the liquid crystal cell by a vacuum injection method or the like to form a liquid crystal layer. When the liquid crystal alignment film is an alignment film capable of vertically aligning liquid crystal molecules, a liquid crystal material having negative dielectric anisotropy is preferable. The liquid crystal material may be a mixture of a liquid crystal composition, a polymerizable resin material, and a polymerization initiator. In this case, after injecting the liquid crystal material, the polymerizable resin material is polymerized, and the liquid crystal composition and the polymer are mixed. And the liquid crystal layer is oriented in an axially symmetrical manner to form a liquid crystal layer.

The present invention can be applied to a plasma addressed liquid crystal display. Hereinafter, the plasma addressed liquid crystal display device of the present invention will be described.

(Embodiment 2) The plasma addressed liquid crystal display of this embodiment will be described with reference to the schematic diagram of FIG.

The plasma addressed liquid crystal display device 200 has a plasma substrate 32, a counter substrate 38, and a liquid crystal layer 39 disposed therebetween. The plasma substrate 32 has a plurality of discharge spaces 35 defined in a space surrounded by a plurality of partition walls 37 and a dielectric sheet 33 provided substantially in parallel.
The inside of the discharge space 35 is filled with a gas for generating plasma, and an anode A and a cathode K are provided as discharge electrodes. By applying a voltage to these discharge electrodes A and K, the gas sealed in the discharge space is ionized and plasma discharge occurs. Counter substrate 38
Has a plurality of data electrodes 40, and the data electrodes 40
It extends so as to be orthogonal to the discharge space 35. A region where these are orthogonal defines a pixel region. The liquid crystal layer 39 has a structure
43 and a liquid crystal region 36 in contact with the structure 43. A liquid crystal layer 39 is provided on the plasma substrate 32 and the counter substrate 38, respectively.
A liquid crystal alignment film 41 is provided so as to be in contact with.

(Embodiment 3) A plasma addressed liquid crystal display device in which a liquid crystal display region is oriented symmetrically in another embodiment of the present invention will be described with reference to FIG. As a liquid crystal material, a material prepared by mixing a liquid crystal composition, a polymerizable resin material, and a polymerization initiator at a predetermined ratio is injected into a plasma addressed liquid crystal panel manufactured in the same manner as in the second embodiment. Next, for example, after performing a plasma discharge, a predetermined voltage is applied to the liquid crystal data electrode 40 to orient the liquid crystal molecules symmetrically. Thereafter, predetermined ultraviolet rays are irradiated from the plasma substrate 32 side. Thus, the above-described plasma addressed liquid crystal display device can be manufactured.

Here, in the step of exposing to ultraviolet light,
In particular, not only ultraviolet exposure from the front direction, but also ultraviolet exposure from an oblique direction, uniform ultraviolet exposure from multiple directions combining these, exposure using a diffusion-type ultraviolet light source, and the like are extremely effective. In the liquid crystal region in the vicinity of the plasma partition 37, which is a light-shielding region for ultraviolet rays, since the alignment is not sufficiently regulated by polymerization of the polymerizable resin, for example, the afterimage phenomenon when viewed from an oblique direction of the panel may be a problem. . Therefore, when regulating the alignment state of the liquid crystal region by the ultraviolet exposure as described above, the oblique direction (the angle from the normal direction of the liquid crystal panel surface to about 0 to ± 7
It is effective to perform UV exposure from multiple directions including 5 ゜). By using the liquid crystal alignment film and the electrode protection film described in the present invention in combination therewith, a high-quality display device with a wide viewing angle and no image sticking can be formed.

In particular, regarding this oblique ultraviolet exposure, FIG.
This will be described in detail with reference to FIG. Here, FIG. 4 and FIG. 5 are upside down. A cathode electrode K, an anode electrode A, and a plasma rib partition 37 formed on the plasma substrate 32
Although closely related to the formation pitch, height, and the like of the region serving as the ultraviolet light shielding portion, it can be roughly explained as follows. For example, when ultraviolet rays are incident from the plasma substrate 32 side at an angle θ with respect to the normal direction of the substrate, the ultraviolet rays reach the area a, and the liquid crystal layer below this area The ultraviolet rays are refracted and reach the area a ′ of the 39, and the alignment can be controlled by ultraviolet polymerization. By performing such oblique ultraviolet exposure at a predetermined intensity from an angle ± θ direction with respect to the normal direction of the surface of the plasma substrate, that is, the liquid crystal panel, alignment control by ultraviolet exposure cannot be sufficiently performed only from the front direction. The ultraviolet rays can also reach the region that has been exposed, that is, the region inside the substrate in the direction normal to the light-shielding portion. Therefore, it is possible to prevent a region that is not exposed to ultraviolet rays (an ultraviolet light shielding region b in FIG. 5) from remaining. If there is a region not exposed to ultraviolet light in the liquid crystal layer, not only will the reactive polymerizable material remain in the liquid crystal composition, but also the effect on the display characteristics of the liquid crystal panel will increase, making it difficult to control the alignment state. It is a sufficient cause of display burn-in afterimage due to a sufficient factor, and deteriorates the display reliability of the panel.

In the present invention, the oblique exposure method includes:
Either one or both of the liquid crystal panel and the ultraviolet light source may be set at a predetermined angle to perform the ultraviolet exposure. Also,
It is also very effective to promote ultraviolet polymerization using a diffusible ultraviolet light source device. FIG. 5 schematically illustrates the refractive index of the glass medium as 1.5 and the refractive index of the gas layer (air layer, plasma layer) as 1, but is not limited thereto. The incident angle in the oblique exposure method is an angle from the normal direction of the liquid crystal panel surface, and is preferably 0 to ± 75 °.

Although the plasma addressed liquid crystal display device of the present invention has been described in the second and third embodiments as described above, the present invention is not limited to these embodiments.

In one embodiment, the color filter
A portion including the counter substrate, the color filter, the data electrode (liquid crystal signal electrode) 40, and the liquid crystal layer 39 constitutes the display cell 31. Counter substrate 3 of liquid crystal display device 200
A polarizing plate (not shown) may be provided outside the substrate 8, and a polarizing plate and a backlight (both not shown) may be provided outside the plasma substrate 32.

In a plasma addressed liquid crystal display device as well, it is preferable that a plurality of regions are regularly divided by a structure with respect to a pixel region which is a minimum unit for performing display. In this case, for example, the residual DC of the liquid crystal panel
More preferably, the voltage value is 100 mV or less and the measured ion density is 5 μC or less. In one embodiment, a structural body (for example, a columnar spacer) 43 may be provided at a corner of the liquid crystal region 36 for each pixel of the liquid crystal layer 39. In this case, the pixel region 36 that is axially symmetrically aligned by the columnar spacer 43
And the column spacer 43 can keep the cell thickness of the liquid crystal cell constant.
Further, the columnar spacer 43 is a pixel area 36 for each pixel.
Are arranged at the corners, so that there is no hindrance at the time of injecting the liquid crystal, and the injection speed of the liquid crystal material or the like does not decrease.

In one embodiment, an axially symmetric orientation fixed layer (not shown) may be provided on at least one of the opposite substrate 38 and the thin glass (dielectric sheet) 33.
In this case, it is possible to form the axial position of the pixel region that is in the axially symmetric orientation in the axially symmetric orientation fixed layer at a predetermined position, thereby realizing a stable axially symmetric orientation without displacement of the axial position. it can.

Further, a polarizing plate with a retardation film may be arranged above and below the substrate.

Since the physical property values described in the items A to I in the first embodiment can be similarly applied to the plasma addressed liquid crystal display device of the present invention, detailed description is omitted here. The features unique to the plasma addressed liquid crystal device will be described below.

In the plasma addressed liquid crystal device, it is preferable that the semiconductive protective film (dielectric sheet protective film) 44 of the above-described item G is provided between the dielectric sheet 33 and the liquid crystal alignment film 41. In this case, a drive signal between the data electrode 40 and the anode A is applied to the liquid crystal layer through the dielectric sheet 33 and the dielectric sheet protective film 44. For this reason, the dielectric sheet 33 (which may include the dielectric sheet protective film 44) has a volume resistance of 10 ⁷ in order to suppress two-dimensional diffusion of charges and efficiently remove accumulated charges. it is preferably in the range of ~10 ^{1 4} Ω · cm. When using the dielectric sheet protective film 44, it is particularly effective to form a thinner film than the dielectric sheet 33, and the thickness of this thin film is 30 to
Preferably it is in the range of 300 nm. The film thickness to be formed is 300
If the thickness is larger than 30 nm, it may cause display defects such as conduction between the electrodes.On the other hand, if the thickness is smaller than 30 nm, it will not only be difficult to remove the electric charge sufficiently, but also the plasma discharge portion will be difficult. A small amount of ultraviolet light shielding effect radiated from the surface cannot be obtained sufficiently. Further, when these dielectric sheet protective films 44 are applied to a plasma addressed liquid crystal display device, fine particles such as TiO ₂ are contained in the material, and ultraviolet light having a wavelength of 320 nm or less radiated from the plasma substrate 32 is emitted. It is also effective to have a function of suppressing transmission.
Also, a dielectric sheet protective film containing these inorganic fine particles and the like.
In the dielectric sheet 33 on which the 44 is formed, the apparent strength increases. As a result, a significant improvement can be obtained with respect to the destruction of the panel during the bonding of the plasma addressed liquid crystal cells, the injection of the material, and other manufacturing steps.

The plasma addressed liquid crystal display device of the present invention can be manufactured by any appropriate method using the above-mentioned alignment film material. For example, it is manufactured in the same manner as the liquid crystal display device of the first embodiment except that a plasma substrate 32 is used instead of a driving substrate such as a TFT substrate. Plasma substrate 32 is also made using any suitable method. An example is shown below. A plurality of electrode groups each having a pair of an anode A and a cathode K are formed on a substrate 34, and partition walls 37 are formed using a glass paste or the like so as to separate each electrode.
To form Next, a substrate 33 made of glass or the like is stuck on the partition wall 37 with any appropriate sealing agent to form a discharge space.
Define 35. After that, the discharge space 35 is filled with a gas for generating any appropriate plasma to form a plasma substrate. The plasma addressed liquid crystal display device of the present invention can be manufactured using the plasma substrate 32 manufactured as described above.

[0088]

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.

The conditions for evaluating the characteristics of the liquid crystal display devices manufactured in Examples and Comparative Examples are shown below.

Film capacity of alignment film material C _AL ; Measured at 25 ° C. and 0.01 Hz using an LCR meter.

Time constant τ _AL : Calculated from equation 3 based on the volume resistivity ρ obtained by measurement (25 ° C.) using an electrometer.

Evaluation of electro-optical characteristics (transmittance): Using a liquid crystal characteristic evaluation system LCD-5000 (manufactured by Otsuka Electronics Co., Ltd.), a voltage was determined by using a cell in which polarizing plates were arranged in parallel Nicols on both sides of two glass substrates as a reference. -The transmission characteristics were measured.

Evaluation of residual DC voltage: RDC-1 (manufactured by Toyo Technica Co., Ltd.) was used.
After applying for 30 minutes at 5 ° C., the circuit was short-circuited for 1 second, and a voltage value after 10 minutes was measured (measuring temperature; 25 ° C.).

Evaluation of ion density: MTR-1 (manufactured by Toyo Technica), applied voltage 10 V at 25 ° C., triangular wave frequency 0.01 Hz
The total electric quantity of ions was obtained from the area of the current peak approximated by a triangular wave.

Evaluation of voltage holding ratio characteristics: Using VHR-1 (manufactured by Toyo Technica), applying a voltage of ± 5 V rectangular wave for 60 μsec selection pulse, and holding voltage for one frame (30 Hz; 16.67 msec) The rate was measured at 25 ° C.

Afterimage evaluation A: After applying a fixed pattern on the display area at 60 ° C. for a predetermined time, application of the pattern was stopped, and a display afterimage (burn-in image) was observed and evaluated.
However, the evaluation criteria are as follows. Afterimage level 1; Slight afterimage level at which burn-in afterimage disappears within a few minutes Afterimage level 2; Afterimage level at which burn-in afterimage disappears in about 10 minutes Afterimage level 3; Afterimage at which burn-in afterimage does not disappear even after 30 minutes or more level.

Afterimage evaluation B: The plasma-addressed liquid crystal display was driven at room temperature, and the afterimage of the fixed pattern was evaluated. However, the evaluation criteria are as follows. Afterimage level a: An afterimage level at which burn-in afterimages do not disappear even after more than one hour. Afterimage level b; An afterimage level at which burn-in afterimages disappear within one hour. Afterimage level c: An afterimage level at which burn-in afterimages disappear within 30 minutes.

Example 1 Two 1.1 mm-thick glass substrates 1 and 2 each having a transparent electrode made of ITO (a mixture of indium oxide and tin oxide; 50 nm) are used, and one of the glass substrates is shown in FIG. Wall 22 including 5μm spacer 21 (pattern formation with negative photoresist material)
Was formed to have a height of 2.7 μm. Next, a liquid crystal alignment film material having physical properties as shown in Table 1 below was applied to both substrates, and then both substrates were bonded together via a sealing resin to form a liquid crystal cell.

[0099]

[Table 1]

In the thus prepared liquid crystal cell, as a liquid crystal material, 0.92 g of ZLI-4792 (manufactured by Merck; the chiral pitch was adjusted to 90 ° between cells with a chiral agent S-811), and isobornyl acrylate 0.02 g g, 0.01 g of R-684 (manufactured by Nippon Kayaku Co., Ltd.) and 0.001 g of photopolymerization initiator Irgacure651 are uniformly mixed into a liquid crystal cell by a vacuum injection method, and a horizontal mode liquid crystal is injected. Layer obtained.

After the material injection, exposure to ultraviolet light was performed while applying a rectangular wave of 3 Vrms and 60 Hz to stabilize the alignment state of liquid crystal molecules in the liquid crystal region. When the thus obtained liquid crystal panel was observed under a polarizing microscope, a liquid crystal region 8 surrounded by the polymer wall 7 was observed as shown in FIG. 7, and a radial quenching pattern 23 was observed in the liquid crystal region 8. Thus, it was confirmed that the liquid crystal region 8 was in an axially symmetric alignment state around the symmetry axis near the center. In the axially symmetric alignment, liquid crystal molecules whose molecular axes are parallel to the polarization axis of the polarizing plate and liquid crystal molecules whose molecular axes are inclined with respect to the polarizing plate exist continuously. As a result, a radial quenching pattern was observed.

Table 2 shows the results of evaluating the characteristics of the obtained liquid crystal display device by attaching polarizing plates to both sides of the liquid crystal panel thus manufactured so that their polarizing axes are orthogonal to each other.

[0103]

[Table 2]

(Examples 2 to 4 and Comparative Examples 1 to 4) Example 1 was repeated except that the alignment film materials shown in Table 1 were used, and that the liquid crystal material was changed in accordance with the horizontal mode or the vertical mode. A liquid crystal display device was obtained in the same manner as described above. Here, in Example 2 and Comparative Examples 1 and 2 in the horizontal mode, as in Example 1, ZLI-4792 (manufactured by Merck; Chiral agent S-811; chiral pitch 90 ° between cells) was used as a liquid crystal material. Adjusted to 0.92
g, isobornyl acrylate 0.02 g, R-684 (manufactured by Nippon Kayaku Co., Ltd.) 0.01 g, and a photopolymerization initiator Irgacure 651 0.001 g, and a precursor mixture obtained by uniformly mixing the mixture into a liquid crystal cell by a vacuum injection method. Injected. On the other hand, in Examples 3 and 4 and Comparative Examples 3 and 4 in the vertical mode, an Nn-type liquid crystal material was used as a liquid crystal material.
(Δε = -3.2, Δn = 0.08, twist angle specific to liquid crystal material is set so that 90 ° twist occurs between cells), Photopolymerization 2
A precursor mixture composed of a functional resin and a photopolymerization initiator was similarly injected into the liquid crystal cell. The photopolymerizable bifunctional resin was added at 0.4% by weight based on the entire liquid crystal material, and the photopolymerization initiator was added at 5% by weight based on the photopolymerizable resin. Table 2 shows the results of evaluating the characteristics of these liquid crystal panels.

As described above, it has been confirmed that the optimization of the physical property values of the constituent materials specified in the present invention is important for suppressing the afterimage after printing. The physical properties of the constituent materials specified in the present invention are indicated by values measured at 25 ° C., but generally, ion density, residual DC voltage, and the like take larger values at high temperatures. It is considered that the voltage holding ratio and the like tend to decrease as the temperature increases and the afterimage level tends to decrease.

Example 5 A cell spacer (columnar pattern) was formed on a bus line of a TFT substrate through a photosensitive material patterning process in consideration of a wiring step, and had physical properties shown in Table 3 below. The alignment film material was applied and bonded to a counter substrate with a color filter (the same alignment film material as the TFT substrate side was applied) to obtain a TFT liquid crystal panel. The liquid crystal cell thickness of this panel was designed to be 5.0 μm.

[0107]

[Table 3]

In the TFT liquid crystal panel thus manufactured, only the Nn-type liquid crystal material (Δε = −3.2, Δn = 0.08, a twist angle specific to the liquid crystal material is set so as to have a 90 ° twist between cells) in the fifth embodiment. Was injected by a vacuum injection method, and a liquid crystal panel was manufactured through the same processing steps as in Example 1.

Next, an optical compensation film having a retardation value of (nx-ny) .df = 40 nm and (nx-nz) .df = 200 nm on both sides of the TFT liquid crystal panel and a polarizing plate outside the retardation plate in a crossed Nicols state. Placed. These films were disposed such that the direction of the delay axis of the retardation compensation film was orthogonal to the absorption axis of each polarizing plate.

A drawing circuit is connected to these TFT liquid crystal panels, and a pattern generator is connected as an image signal source.
After displaying the TFT pattern afterimage (lattice pattern (white grid pattern on black background)) and removing the pattern after 24 hours at 60 ° C, the afterimage is displayed from white to black on the entire screen while gradually reducing the gradation. Was observed. No afterimage was observed. In addition,
In this panel, a wide viewing angle display in all directions was obtained due to the compensation effect of the retardation film.

(Example 6 and Comparative Example 5) In Example 6 and Comparative Example 5, the alignment film materials shown in Table 3 were used, and the same materials as in Example 3 were injected by vacuum injection, respectively. A liquid crystal display device was obtained in the same manner as in Example 5 except for the above.

In Example 6, no afterimage was observed. On the other hand, in Comparative Example 5, the afterimage of the afterimage level 3 was observed.

In these panels, a wide viewing angle display in all directions was obtained due to the compensation effect of the retardation film.

Example 7 A plasma addressed liquid crystal display as shown in FIG. 4 was actually manufactured. The specific procedure is as follows.

First, a plasma substrate 32 was manufactured. Specifically, a plurality of electrode groups each having a pair of an anode A and a cathode K were formed on a substrate 34, and partition walls 37 were formed in a line so as to separate each electrode. Next, a thin glass substrate 33 is attached as a dielectric sheet on the partition wall 37 with a sealant,
A linear channel 35 was defined as a discharge space. Thereafter, the discharge space 35 was filled with a gas for generating plasma to obtain a plasma substrate 32. Further, a dielectric sheet protective film 44 shown in Table 4 below was formed on the opposite side of the channel 35 of the thin glass substrate 33, and a vertical alignment film 41 shown in Table 4 below was formed thereon as a liquid crystal alignment film. .

Next, as a counter substrate, a transparent glass substrate 38 is used.
A color filter 42 is formed thereon, a stripe-shaped data electrode (liquid crystal signal electrode) 40 is further formed, and a vertical alignment film 41 shown in Table 4 below is formed thereon as a liquid crystal alignment film.
A columnar spacer 43 was formed as a structure. The plasma substrate 32 and the counter substrate 38 thus obtained are bonded together such that the stripe-shaped liquid crystal signal electrodes 40 cross the line-shaped channels 35 and are wired in the vertical direction. A panel was prepared. Substrate 38 and thin glass substrate
The cell thickness between them is maintained constant by the column spacer 43. Note that the columnar spacer 43 may be formed, and then the alignment film 41 may be formed.

After injecting the same liquid crystal material as in Example 6 into the prepared panel, a voltage was applied to the liquid crystal layer, and the liquid crystal layer was exposed to ultraviolet light to fix the axially symmetric alignment.

A polarizing plate (not shown) was provided outside the opposing substrate of the liquid crystal display device thus configured, and a polarizing plate and a backlight (both not shown) were provided outside the plasma substrate.

Table 4 also shows the results of the evaluation of the afterimage of the manufactured panel.

[0120]

[Table 4]

Example 8 and Comparative Examples 6 to 8 Table 4
A plasma-addressed liquid crystal display device was obtained in the same manner as in Example 7, except that the alignment film material and the dielectric sheet protective film material shown in (1) were used. Table 4 also shows the evaluation results of the afterimages of these manufactured panels.

As shown in Table 4, Examples 7 and 8 show good display characteristics in which afterimages do not occur even after a fixed pattern is displayed for a long period of time, and can effectively reduce the afterimage phenomenon as compared with Comparative Examples 6 and 8. It was possible to reduce to.

It was confirmed that the plasma addressed liquid crystal display device of this embodiment, in which the polarizing plates with a retardation film were disposed above and below the substrate, had better wide viewing angle characteristics than the conventional liquid crystal panel.

Further, in the plasma addressed liquid crystal panel provided with the protective film layer used in Example 7 and the like, it was confirmed that the intensity of ultraviolet light having a wavelength of 320 nm radiated through the dielectric sheet could be significantly reduced, and the display reliability of the panel was confirmed. It was confirmed that there was an effect also from the viewpoint of.

[0125]

According to the present invention, the time constant τ of the liquid crystal alignment film is
By optimizing and specifying the combination of _AL , the residual voltage value of the liquid crystal panel, and the physical properties such as ion density,
Even after the voltage application is canceled or when the next display signal is selected,
There is provided a liquid crystal display device in which a previous display does not remain (that is, there is no afterimage of a displayed image). Furthermore, with regard to the plasma addressed liquid crystal display device, charge remaining at the interface of the multilayer dielectric is mainly caused by optimizing the physical property values of the liquid crystal material and the alignment film material constituting the panel and optimizing the selection of the dielectric sheet layer. It is possible to effectively reduce the image sticking phenomenon.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a voltage holding ratio of a liquid crystal cell and a reciprocal of a material time constant.

FIG. 3 is a diagram showing a relationship between a residual DC voltage and a reciprocal of a material time constant.

FIG. 4 is a schematic view of a plasma addressed liquid crystal display device according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a plasma addressed liquid crystal display device according to an embodiment of the present invention.

FIG. 6 is a schematic view of a substrate having a patterning wall manufactured in Examples 1 to 4 and Comparative Examples 1 to 4.

FIG. 7 is a schematic diagram showing a state where the liquid crystal display devices of Examples 1 to 4 and Comparative Examples 1 to 4 are observed with a polarizing microscope.

FIG. 8 is a schematic diagram for explaining a change in contrast depending on a viewing angle, and is a cross-sectional view of an ASM mode liquid crystal display device. (a) shows a white display, (b) shows a halftone display, and (c) shows a black display.

FIG. 9 is a schematic diagram for explaining a change in contrast depending on a viewing angle, and is a cross-sectional view of a conventional TN mode liquid crystal display device.

FIG. 10 is a schematic diagram of an equivalent circuit of a liquid crystal cell.

[Description of Signs] 1, 2 substrate 3 structure 4, 5 alignment film 8 liquid crystal region 10 liquid crystal panel 21 spacer 22 patterning wall 23 extinction pattern 32 plasma substrate 33 dielectric sheet (thin glass) 34 substrate 35 discharge space (channel) 37 Partition wall 38 Substrate 39 Liquid crystal layer 41 Liquid crystal alignment film 43 Structure (columnar spacer) 44 Dielectric sheet protective film 100 Liquid crystal display device 200 Plasma addressed liquid crystal display device a, a 'UV transmission region b UV shielding region

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 EA34 GA06 HA02 HA03 HA08 HA16 JA04 KA27 LA09 MA20 2H089 HA02 HA36 KA02 QA16 RA04 TA02 TA04 TA09 TA14 2H090 HB08Y HB13Y HD11 KA04 KA12 LA06

Claims (28)

[Claims] 1. A pair of opposing substrates each provided with a liquid crystal alignment film, and disposed between the pair of substrates.
A liquid crystal panel having a structure and a liquid crystal layer comprising a liquid crystal region in contact with the structure, and a time constant τ defined by a product of a sheet resistance value R _AL and a film capacitance C _AL of the liquid crystal alignment film.
_A liquid crystal display device having an _AL of 4000 seconds or less. Wherein said membrane capacitance C _AL of the liquid crystal alignment film, 5n
The liquid crystal display device according to claim 1, wherein the liquid crystal display device has an F of 200 to 200 nF. 3. The liquid crystal display device according to claim 1, wherein a residual DC voltage value of the liquid crystal layer is 100 mV or less. 4. The measured value of the ion density of the liquid crystal panel is:
4. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has a temperature of 5 μC or less. 5. The liquid crystal display device according to claim 1, wherein the liquid crystal composition of the liquid crystal layer has negative dielectric anisotropy, and the liquid crystal alignment film has vertical alignment. 6. The liquid crystal display device according to claim 5, further comprising a phase difference compensating element on at least one surface of the pair of substrates. 7. A transparent electrode is provided on at least one of the pair of substrates, further comprising a transparent electrode protective film between the transparent electrode and the liquid crystal alignment film, wherein the volume of the transparent electrode protective film is The liquid crystal display device according to any one of claims 1 to 6, wherein the resistance value is 10 < ⁷ > to 10 < ¹⁴ > [Omega] .cm. 8. The liquid crystal display device according to claim 7, wherein the transparent electrode protective film contains conductive fine particles. 9. The liquid crystal display device according to claim 1, wherein the structures are axially symmetrically arranged, and liquid crystal molecules in the liquid crystal region are axially symmetrically aligned. 10. The liquid crystal layer according to claim 9, wherein the liquid crystal layer is a polymer of a mixture of a liquid crystal composition, a polymerizable material in an amount of 0.1 to 10% by weight based on the liquid crystal composition, and a polymerization initiator. Liquid crystal display device. 11. The liquid crystal area according to claim 9, wherein the liquid crystal area is arranged in a plurality of areas regularly divided by a structure corresponding to a pixel area which is a minimum unit for performing display. Liquid crystal display device. 12. A plurality of discharge spaces defined by a space surrounded by a plurality of partition walls and a dielectric sheet provided substantially in parallel, having a discharge electrode therein, and being filled with a gas for generating plasma. And a counter substrate having a plurality of data electrodes provided in a direction orthogonal to the discharge space, a structure disposed between the plasma substrate and the counter substrate, a structure and a structure A liquid crystal layer comprising a liquid crystal region in contact with the liquid crystal layer, a liquid crystal alignment film provided on the liquid crystal layer side of the plasma substrate and the counter substrate, and a sheet resistance R _AL and a film capacitance C _AL of the liquid crystal alignment film. A plasma addressed liquid crystal display device wherein a time constant τ _AL defined by a product value is 4000 seconds or less. 13. The film capacitance _CAL of the liquid crystal alignment film,
13. The plasma addressed liquid crystal display device according to claim 12, wherein the value is 5 nF to 200 nF. 14. The liquid crystal layer has a residual DC voltage value of 100 mV.
14. The plasma addressed liquid crystal display device according to claim 12, wherein: 15. The volume resistivity of the dielectric sheet is 10 ^7.
Is ~10 ¹⁴ Ω · cm, the plasma addressed liquid crystal display device according to any one of claims 12 to 14. 16. The method according to claim 1, further comprising a dielectric sheet protective film on the dielectric sheet in contact with the liquid crystal layer, wherein the dielectric sheet protective film has a volume resistance of 10 ⁷ to 10 ¹⁴ Ω · cm.
15. The plasma addressed liquid crystal display device according to any one of 2 to 14. 17. The film thickness of the dielectric sheet protective film is 30 to
17. The plasma addressed liquid crystal display according to claim 16, wherein the range is 300 nm. 18. The dielectric sheet protective film has a wavelength of 320 nm.
2. A function for suppressing transmission of the following ultraviolet light.
18. The plasma addressed liquid crystal display device according to 6 or 17. 19. The plasma addressed liquid crystal display according to claim 12, wherein the liquid crystal composition of the liquid crystal layer has a negative dielectric anisotropy and the liquid crystal alignment film has a vertical alignment property. . 20. The liquid crystal display device according to claim 20, wherein the structure is axially symmetrically arranged, and liquid crystal molecules in the liquid crystal region are axially symmetrically aligned.
A plasma addressed liquid crystal display device according to any one of claims 12 to 19. 21. The plasma according to claim 20, wherein the liquid crystal region is arranged in a plurality of regions regularly separated by a structure corresponding to a pixel region which is a minimum unit for performing display. Address liquid crystal display device. 22. A step of forming a structure on one substrate
And a substrate on which the structure is formed and the other substrate.
Resistance R_ALAnd membrane capacity C _ALTime defined by the value of the product of
Number τ_ALHowever, using a material that is less than 4000 seconds, the liquid crystal alignment film
Forming each with a predetermined thickness;
Injecting a liquid crystal material between the substrates to form the structure and the structure
Forming a liquid crystal layer comprising a liquid crystal region in contact with the body.
Includes a method for manufacturing a liquid crystal display device. 23. The liquid crystal material is a mixture of a liquid crystal composition, a polymerizable resin material, and 0.5 to 10% by weight of a polymerization initiator based on the polymerizable resin material. 23. The method of manufacturing a liquid crystal display device according to claim 22, further comprising a step of polymerizing and orienting the liquid crystal molecules in the liquid crystal region in an axially symmetric manner. 24. A step of providing a plurality of partition walls and a plurality of discharge electrodes on a substrate substantially in parallel with each other, and defining a discharge space having the discharge electrodes therein by the partition walls and the dielectric sheet; Is filled with a gas that generates plasma,
A step of forming a plasma substrate; a step of forming a structure on a counter substrate; and a time constant τ _AL defined by a product of a sheet resistance value R _AL and a film capacitance C _{AL on} the plasma substrate and the counter substrate. Forming a liquid crystal alignment film with a predetermined thickness by using a material having a length of 4000 seconds or less; injecting a liquid crystal material between the plasma substrate and the counter substrate to form the structure and the liquid crystal material; Forming a liquid crystal layer comprising a liquid crystal region in contact with the structure. 25. A volume resistance value on the dielectric sheet
10 ⁷ further comprising ~10 ¹⁴ Ω · cm at a dielectric sheet protective film a step of applying and forming method of the plasma addressed liquid crystal display device according to claim 24. 26. The liquid crystal material is a mixture of a liquid crystal composition, a polymerizable resin material, and 0.5 to 10% by weight of a polymerization initiator based on the polymerizable resin material. 26. The method of manufacturing a plasma addressed liquid crystal display device according to claim 24, further comprising a step of polymerizing and orienting liquid crystal molecules in the liquid crystal region in an axially symmetric manner. 27. The step of polymerizing the polymerizable resin material further includes a step of irradiating the liquid crystal layer with ultraviolet rays in a direction perpendicular to and / or at an oblique direction to the substrate surface of the plasma substrate. 27. The method for manufacturing a plasma addressed liquid crystal display device according to item 26. 28. The method according to claim 26, wherein the step of polymerizing the polymerizable resin material further includes a step of irradiating the liquid crystal layer with diffuse ultraviolet rays.