JPH09160039A - Liquid crystal display element and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent display quality and to reduce the dependency of display quality on a visual angle direction by allowing axially symmetric orientation domain to have specified aspect ratio. SOLUTION: This liquid crystal display element 30 is provided with a liquid crystal layer 32 consisting of a liquid crystal area 23 surrounded by high molecular area 24 between a pair of base plates 31a and 31b. The pair of base plates 31a and 31b is provided with an electrode for impressing voltage on the liquid crystal layer 32 on the liquid crystal layer 32 side thereof. The liquid crystal area 23 is the axial symmetric orientation domain and the aspect ratio of the domain is set larger than 1:1 and equal to or under 1:6. By impressing the voltage on liquid crystal molecules LC oriented to be axially symmetric, the liquid crystal molecules LC are oriented to be parallel with the direction of electric field while keeping the axial symmetricity. Thus, apparent transmissivity is averaged in all the visual angle directions (for instance, in the visual angle directions A and B), so that the dependence ability of the display quality on the visual angle direction is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having wide viewing angle characteristics and a method for manufacturing the same. INDUSTRIAL APPLICABILITY The liquid crystal display device of the present invention is used for a flat display such as a personal digital assistant, a personal computer, a word processor, an amusement device, and a television device viewed by a large number of people, a display plate utilizing a shutter effect, a window, a door, a wall, etc. .

[0002]

2. Description of the Related Art Conventionally, a TN type LCD using a nematic liquid crystal or an STN type LCD has been put into practical use as a liquid crystal display element (LCD) utilizing the electro-optical effect. These use a polarizing plate and require an alignment treatment for aligning liquid crystal molecules in a predetermined twist. For example, TN type LC
As shown in FIGS. 20A to 20C, in D, the liquid crystal molecules LC have a pretilt angle in one direction when no voltage is applied. Therefore, when a voltage is applied, the liquid crystal molecules LC rise in the same direction. . At this time, when the observer observes the cell from different viewing angle directions A or B as shown in FIG.
The apparent transmittance is different and the contrast is also different.
Therefore, the display quality changes depending on the viewing angle. Further, in the state where the halftone is displayed, the display quality is remarkably deteriorated, for example, the phenomenon that the contrast is inverted depending on the viewing angle occurs in a certain viewing angle direction.

For the purpose of improving the viewing angle direction dependence of display quality, the present inventors have proposed a liquid crystal display device in which liquid crystal molecules are arranged in axial symmetry in a region surrounded by polymer walls.
It is disclosed in Japanese Patent Publication No. 1015. In addition, a method of aligning liquid crystals by rubbing in a concentric or radial pattern (Japanese Patent Laid-Open No. 6-
265902) or a method of forming concentric circular or radial fine grooves on a substrate to orient liquid crystal molecules (Japanese Patent Laid-Open No. H06-242242).
-324337).

[0004]

However, in the above-mentioned prior art, since the symmetry of the alignment state of the liquid crystal molecules within the picture element is high, it is effective in the square picture element, but it is currently commercially available. In a OA device such as a personal computer and a car navigation system, a display device having a picture element having a shape not having rotational symmetry such as a long picture element is used. For example, when a liquid crystal display element having long picture elements is manufactured using the above technique, the symmetry of the alignment state of the liquid crystal molecules is low. Therefore, as shown schematically in FIG. 21, the alignment axis is near the center of the picture element. May be largely deviated from, or a plurality of alignment axes may be formed. In such a case, the display screen is grainy, resulting in poor display quality.

In order to avoid the deterioration of the display quality, there is also a method of dividing a long picture element into pseudo square picture elements and forming an axially symmetrical orientation in each pseudo square picture element. However, since the boundary between the pseudo-square picture elements does not contribute to the display, the light shielding layer (black mask etc.) should cover the boundary.
However, there is a problem in that the aperture ratio is reduced by the amount of the divided boundary.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a liquid crystal display element having excellent display quality and having little viewing angle direction dependence of the display quality, and a manufacturing method thereof. To provide.

[0007]

The liquid crystal display element of the present invention is a liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of substrates, at least one of which is disposed so as to face each other and which is transparent. The liquid crystal molecule has a plurality of axially symmetric alignment domains aligned in an axially symmetric manner, and the aspect ratio of the axially symmetric alignment domains is greater than 1: 1 and less than 1: 6, whereby the above object is achieved. It

Each of the plurality of axially symmetric orientation domains may be surrounded by a polymer region.

Each of the plurality of axially symmetric alignment domains may be formed corresponding to a pixel of the liquid crystal display device.

A wall made of an insulator is provided around the plurality of axially symmetric orientation domains, and the minimum height Z of the wall is in the range of 0.5 × D <Z <0.8 × D, where D is the cell gap. Good.

There may be a maximum gap between the substrates near the center of the picture element.

At least one of the pair of substrates may have a recess near the center of the picture element. The area of the recess may be 25% or more and 50% or less of the area of the picture element.

The shape of the recess may be elliptical or rectangular.

The ratio of the major axis to the minor axis of the ellipse of the recess or the aspect ratio of the rectangle may be larger than 1: 1 and smaller than the aspect ratio of the axisymmetric orientation domain.

The cross-sectional shape of the recess may be a mortar shape.

A transparent electrode may be provided on the recess.

The recess may be formed in a substrate having a color filter.

The method for producing a liquid crystal display device of the present invention includes the steps of injecting a mixture of a liquid crystal material and a polymerizable material between a pair of substrates and a step of phase-separating the mixture. In the method, a step of applying a voltage to the mixture in a state where the diameter of the liquid crystal droplet formed by phase separation is the same size as the short side of the picture element is included, whereby the above object is achieved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

(Aspect Ratio of Axisymmetric Alignment Domain) According to the present invention, liquid crystal molecules in a region having an aspect ratio of more than 1: 1 can be axially symmetric aligned having an alignment axis near the center of the liquid crystal region. it can. In this specification, a liquid crystal region having an axially symmetric orientation is called an axially symmetric orientation domain. The axially symmetric orientation means a radial (radial), concentric (tangential) or spiral orientation. Further, the aspect ratio of the axially symmetric orientation domain or picture element in the present specification refers to the aspect ratio in the display surface of the liquid crystal display element. The shape is not limited to a rectangle, and may be any shape having two characteristic directions with different lengths represented by the long axis or the short axis. For example, the shape of a picture element of a liquid crystal display element having a switching element for each picture element has a shape in which a part of a rectangle (switching element portion) is lacking, but the shape is characterized by two axes of long and short. be able to.

In order to align the position of the orientation axis near the center of each axially symmetric region, the aspect ratio of the axially symmetric orientation domain is preferably 1: 6 or less. When the axially symmetric alignment domain is formed by utilizing the phase separation of the mixture of the polymerizable resin material and the liquid crystal material, the aspect ratio of the axially symmetric region is 1 :.
If it exceeds 6, good axially symmetric orientation may not be obtained. By the time the liquid crystal phase (liquid crystal droplets) that has begun to undergo phase separation (precipitation) grows from the edge of the region that will become the axially symmetric alignment domain, and it fuses with the liquid crystal phase (liquid crystal droplets) that precipitates and grows in the center of the region Since the size of the liquid crystal droplets that have started to form from the end portion is approximately the same as the size of the liquid crystal droplets that have the axially symmetric orientation that has started to form at the central portion, they merge to form one liquid crystal region. At this time, the alignment of the liquid crystal molecules in the liquid crystal region is disturbed from the axially symmetric alignment.

(View Angle Direction Dependence) When the aspect ratio of the axially symmetric alignment domain is large, it is expected that the display quality of the liquid crystal display device will depend on the view angle direction. However,
In the liquid crystal display device having the axially symmetric alignment domain according to the present invention, the viewing angle direction dependence of display quality is small. FIG. 1 is a schematic diagram showing a change in transmittance when a pixel 10 (aspect ratio S: L = 1: 2) composed of an axially symmetric orientation domain according to the present invention is tilted. FIG. 1A shows the picture element 10 with the short axis S.
1B shows the case where the picture element 10 is tilted in the major axis L direction. No matter which direction the light is tilted, the area of the portion 11 where the transmittance decreases in the picture element is substantially equal, and therefore, the change in the transmittance when the liquid crystal display element (or the viewing angle) is tilted does not change depending on the viewing angle direction. , Hardly observed.

(Alignment State of Liquid Crystal Molecules in Axisymmetric Alignment Domain) The result of observing the axially symmetric alignment domain 23 of the liquid crystal display device according to the present invention with a polarization microscope is schematically shown in FIG. As shown, a cross-shaped extinction pattern 26 is observed in the polarization axis direction of the polarizing plates arranged in the crossed Nicols state when no voltage is applied, which is surrounded by the polymer region 24 formed by the polymerizable material. Liquid crystal area 23
It is shown that the liquid crystal molecules inside are oriented axially symmetrically around the disclination point 27 in the center. When a voltage is applied to the axially symmetric orientation domain, the disclination line 25 becomes the domain 2 as shown in FIG.
It is formed around 3 and is not formed inside the domain. In FIG. 2B, the domain region 23 is shown in white for the sake of clarity, but when observed under crossed Nicols, the axisymmetric domain 23 looks black, and the disclination line 25 is observed as a bright line in the periphery thereof. To be done.
Therefore, in the normally white mode (white is displayed when no voltage is applied and black is displayed when voltage is applied), in general, the occurrence of disclination lines causes a reduction in contrast. However, according to the present invention, the axisymmetric alignment domain can be formed so that the disclination line is formed outside the pixel. Therefore, by forming the light shielding layer so as to cover the disclination line 25, The black level of the liquid crystal display device is improved, and the contrast can be improved. Furthermore, by adding the liquid crystalline polymer material to the mixture of the polymerizable material and the liquid crystal material, it becomes possible to form the axisymmetric alignment domain without generating any disclination line.

The viewing angle characteristics of the liquid crystal display device 30 according to the present invention will be described with reference to FIGS. The liquid crystal display element 30 includes a liquid crystal layer 3 including a liquid crystal region 23 surrounded by a polymer region 24 between a pair of substrates 31a and 31b.
2 The liquid crystal layer 32 of the pair of substrates 31a and 31b
On the side, there is an electrode (not shown) for applying a voltage to the liquid crystal layer 32. The liquid crystal region 23 is an axially symmetrical alignment domain. When a voltage is applied to the liquid crystal molecules LC that are oriented in axial symmetry, the liquid crystal molecules LC are oriented so as to be parallel to the direction of the electric field while maintaining the axial symmetry. Therefore, since the apparent transmittances are averaged (homogenized) in all viewing angle directions (for example, viewing angle directions A and B in the figure), the viewing angle direction dependence of display quality is reduced.

(Method of Controlling Position of Alignment Axis) As described above, in order to provide a wide-viewing-angle liquid crystal display device capable of high-quality display, the position of the symmetry axis of the axis-symmetric alignment domain is set to the pixel position. It is important to form it uniformly near the center. In the method for forming a liquid crystal layer having an axially symmetric alignment domain from a mixture of a liquid crystal material and a polymerizable material by a polymerization phase separation method, a method for controlling the position of the alignment axis will be described below.

In the polymerization phase separation method, a uniform mixture of a liquid crystal material and a polymerizable material is phase-separated into a liquid crystal phase (liquid crystal region) and a polymer phase (polymer region), and a liquid crystal surrounded by the polymer region. It is a method of forming a liquid crystal layer having a region. A photocurable resin or a thermosetting resin can be used as the polymerizable material. A mixture of a liquid crystal material and a polymerizable material can be phase-separated by polymerizing the polymerizable material, or by controlling the temperature (typically, lowering the temperature from the compatibilization temperature). Can be made. In order to stabilize the structure after phase separation, the polymerizable material is finally polymerized and immobilized.

When the liquid crystal material and the polymerizable material (or the polymer produced by the polymerization reaction) are phase-combined with each other due to the polymerization reaction or the temperature drop, the liquid crystal phase (liquid crystal droplets) is precipitated from the uniform mixture. At this time, when a substrate having a concave portion is used, liquid crystal droplets are aggregated in a portion corresponding to the concave portion (a portion having a large cell gap (a distance between a pair of substrates)). It is considered that the liquid crystal droplets tend to be spherical so that the surface tension thereof is minimized, so that they are stabilized in the concave portions. Therefore,
The axisymmetric orientation domain is formed around the recess.

The depth of the recess is not particularly limited, but is 0.05.
The range of μm to 0.5 μm is preferable. If the depth is less than 0.05 μm, the effect of determining the position of the axis of symmetry may not be obtained sufficiently, and if it is deeper than 0.5 μm, the display color may be incorrect due to deviation from the optimum cell gap. There is. The size of the recess is 25% of the pixel area
50% is preferred. If it is less than 25%, the liquid crystal droplets generated and grown in the portion other than the concave portion become too large.
The axisymmetric orientation may be disturbed when it grows in a recess and merges with a liquid crystal droplet having an axisymmetric orientation. On the other hand, if it is larger than 50%, it becomes difficult to specify the position of the alignment axis, and thus it becomes difficult to form an axially symmetric alignment domain in which the positions of the alignment axes are aligned. The shape of the recess is long in the long axis direction of the pixel (for example, elliptical, rectangular, etc.) in order to prevent the liquid crystal domain deposited from the pixel edge from growing excessively until it merges with the central domain. Is preferred. Further, the ratio of the major axis to the minor axis of the ellipse or the aspect ratio of the rectangle is preferably larger than 1: 1 and smaller than the aspect ratio of the axisymmetric orientation domain. If it is larger than the aspect ratio of the axially symmetric orientation domain, a problem that an axially symmetric orientation cannot be formed may occur.

The material for forming the recess is not particularly limited. The use of a photosensitive material has an advantage that the manufacturing process can be simplified by using a photolithography technique. A patterning material having a larger insulating property has a smaller voltage drop and is less likely to cause a decrease in contrast. Further, by forming the transparent electrode layer on the recess, it is possible to prevent a voltage drop due to the material forming the recess. As the concave portion, a structure having a mortar-shaped cross section with the central portion of the picture element as the deepest portion (for example, FIG. 4) can be used. The substrate 40 having the mortar-shaped recess 46 shown in FIG.
It can be manufactured as follows. A photoresist is applied on the substrate 41a, and a convex portion 42 is formed by using a photolithography technique so as not to cover the picture element 10.
Next, an overcoat material is applied so as to cover the convex portions 42, and an overcoat layer 44 having a mortar-like surface shape is formed. As the overcoat material, a liquid photocurable or thermosetting resin having an appropriate viscosity can be used. The transparent electrode layer 45 is formed on the overcoat layer 44 using ITO or the like. An alignment film may be formed on the transparent electrode layer 45, if necessary.

Further, by forming a wall made of an insulator around the picture element, the position where the axisymmetric orientation domain is formed can be defined. Therefore, the axisymmetric orientation domain should be formed for each picture element. Is possible. Assuming that the cell gap is D, the minimum height Z of this insulator wall is 0.5 × D <
It is preferable that Z <0.8 × D. Here, the minimum height of the insulator wall means the minimum height of the heights of the plurality of insulator walls formed on one substrate. Z <0.5 × D
In the case, adjacent axisymmetric orientation domains are connected, and the axisymmetric orientation in pixel units may be disturbed. Z> 0.8 x
In the case of D, a part of the insulator wall comes into contact with or comes too close to the counter substrate, which may cause defective injection of the liquid crystal material. When Z is in the range of 0.5 × D <Z <0.8 × D, it becomes possible to uniformly form the axially symmetric orientation domain for each pixel.

In the long picture element, the insulator wall in the long axis direction of the picture element may be higher than the height of the insulator wall in the short axis direction in order to further stabilize the axially symmetrical orientation. When the liquid crystal material is injected by a printing method or the like, the above minimum height Z
A higher wall (Z> 0.8 × D) may be formed and used as a cell gap maintaining means instead of the spacer.

For example, the above-mentioned insulator wall can be formed by using a resist material as shown in the following examples. It can also be formed by etching an insulating material having no photosensitivity using a resist material as a mask.

(Method for controlling alignment of liquid crystal material) A method for stabilizing the alignment of liquid crystal molecules in the axially symmetric domain and a method for aligning the alignment axis of the axially symmetric alignment in the direction perpendicular to the substrate will be described below.

(1) Addition of Liquid Crystalline Polymeric Material When a liquid crystal layer having a liquid crystal region surrounded by a polymer region is formed by polymerization phase separation, the state of the interface between the polymer region and the liquid crystal region (interaction) Affects the stability of the axisymmetric alignment of the liquid crystal molecules in the liquid crystal region. By introducing a functional group exhibiting liquid crystallinity or a functional group similar thereto into the polymer forming the polymer region, the interface with the liquid crystal region is generated when the liquid crystal molecule changes its alignment direction with the application of voltage. Polymers in the vicinity can also be given the property of aligning like liquid crystal molecules. As a result, it is possible not to generate a disclination line (25 in FIG. 2) in the axially symmetric orientation domain even when a voltage is applied.

As an example of a method of introducing a functional group exhibiting liquid crystallinity or a functional group similar thereto, a method of adding a photocurable resin having such a functional group to a mixture of a liquid crystal material and a photocurable resin. There is.

(2) Method of applying electric field and / or magnetic field during phase separation As described above, it is important to form the position of the symmetry axis of the axially symmetric orientation domain near the center of the pixel, and
It is important to align the axis of symmetry with the direction perpendicular to the substrate.
If the symmetry axis deviates from the direction perpendicular to the substrate, the viewing angle direction dependence of display quality may not be sufficiently suppressed.

While applying an electric field or / and a magnetic field,
It was found that the axis of the axially symmetrical alignment of the liquid crystal region can be aligned in the direction perpendicular to the substrate by phase-separating the mixture of the liquid crystal material and the polymerizable material. In a small liquid crystal droplet (droplet) when a liquid crystal phase starts to appear from a uniform phase (compatibility state), the effect of aligning the orientation axes by applying an electric field and / or a magnetic field is great, and the liquid crystal phase is in the entire pixel area. The electric or magnetic field may be weakened before reaching. The strength of the electric and magnetic fields is the threshold value (T
It is only necessary to be larger than the threshold value of the electro-optical characteristic evaluated by using the N cell, and it is possible to use one that changes periodically.

[0038]

Embodiments of the present invention will be described below.

Example 1 On a glass substrate with an ITO (mixture of indium oxide and tin oxide) electrode, plastic beads (Micropearl S) having an average particle size of 4.0 μm were prepared.
P-2040: Sekisui Fine Chemical Co., Ltd.
A negative photoresist OMR83 (manufactured by Tokyo Ohka Kogyo Co., Ltd., 15 cp) was applied and baked thereon. After that, the light shielding portion 51 (aspect ratio (S: L) 1: 3.
5) and a photomask 50 having a light-transmitting portion 52 were used to perform exposure at 200 mJ / cm ² at a predetermined intensity and develop. As a result, as shown in FIG. 6, the spacer 67 is formed on the substrate 61a.
A substrate 60 having a resist layer 62 containing was obtained.

Then, apply OMR83 (60 cp),
After firing, a photomask 70 having a light shielding portion 71 (picture element aspect ratio 1: 4) and a light transmitting portion 72 as shown in FIG.
Was exposed and developed under the above conditions. as a result,
As shown in FIG. 8, a substrate 80 was obtained in which the second resist layer 82 was formed on the substrate 61a so as to cover the resist layer 62 including the spacer 67. The height of the resist layer is 2.
It was 4 to 2.6 μm. The range of height indicates that there is an in-plane distribution.

The other substrate was manufactured as follows. Coating photoresist V-259PA (Nippon Steel Chemical Co., Ltd., 12 cp) 102 on the substrate 101,
Patterning was performed using a mask 90 having a light-shielding portion 91 (ellipse having a ratio of the major axis L1 to the minor axis S1 of 3: 2 and an area ratio of 30% to the picture element) as shown in FIG. afterwards,
The same resist 104 is formed on the patterned substrate.
Was coated to obtain a substrate 100 having a recess 106 as shown in FIG. Furthermore, an ITO thin film was formed on the substrate 100 to form a counter electrode (not shown). A sealing material (Structbond XN-21S, manufactured by Mitsui Toatsu Chemicals, Inc.) was patterned by screen printing on the peripheral portion of this substrate, and two substrates were bonded together to produce a liquid crystal cell. The cell gap D of the obtained liquid crystal cell was 4.0 μm. Therefore, the minimum height Z of the insulator wall in this embodiment is
(2.4 / 4.0) .D = 0.6D.

Next, a photocurable resin (an example of a polymerizable material)
As perfluorooctylethyl acrylate 0.
15 g, lauryl acrylate 0.26 g and R-6
84 (manufactured by Nippon Kayaku Co., Ltd.) lg, p as a photopolymerization inhibitor
-0.19 g of phenylstyrene, 0.1 g of the liquid crystalline photocurable resin shown in Chemical formula 1, and ZLI-47 as the liquid crystal material.
92 (manufactured by Merck & Co., Inc .: chiral agent S-811 was added to adjust the chiral pitch so that the twist angle between the substrates was 90 °) 4.25 g, photopolymerization initiator Irgacure
A mixture was prepared by mixing 0.025 g of 651, and the mixture was injected into the produced liquid crystal cell using a vacuum injection method.

[0043]

Embedded image

The temperature of the obtained liquid crystal cell was kept at 75 ° C.,
By applying phase separation while applying an effective voltage of 2.5 V and 60 Hz between the pair of substrates, an axially symmetric alignment domain having an alignment axis near the center of the pixel was formed.
At this point, the liquid crystal cell was irradiated with ultraviolet rays to cure the photocurable resin, thereby fixing the axially symmetrical alignment of the liquid crystal molecules.

Observation of the obtained liquid crystal cell with a polarization microscope revealed that, as shown in FIG. 11, the liquid crystal region 23 surrounded by the polymer region 14 was in a monodomain state for each pixel 10.
In addition, it was confirmed that the orientation was relatively uniform and axially symmetrical with no observed disordered orientation. Further, in observation with a polarizing microscope, when two polarizing plates whose polarization axes are orthogonal to each other were fixed and the produced liquid crystal cell was rotated, the position of the extinction pattern 26 in the liquid crystal region 23 was constant and the surrounding polymer wall Two
Only 4 was observed to rotate. The polymer wall 24 is observed black. From this, it was found that a uniform axis-symmetrical alignment was obtained in most of the liquid crystal regions 23.

The rate of formation of the axially symmetric alignment domain of the obtained liquid crystal cell, that is, (number of pixels in which axially symmetric alignment domain was formed / total number of pixels) × 100%, and the injection state were visually evaluated. Is shown in Table 1. As shown in Table 1,
In the liquid crystal cell according to this example, an axially symmetric alignment domain was formed in 99% of the picture elements, and no injection failure was observed. Table 1 also shows the results of Example 2 and Comparative Examples 2 and 3 described below.

[0047]

[Table 1]

After that, two polarizing plates with their polarization axes orthogonal to each other were attached to both sides of the produced liquid crystal cell to produce a liquid crystal element.

Observation of the manufactured liquid crystal element with a polarizing head-penetrating mirror while applying a voltage confirmed that a disgranulation line did not occur even when a voltage was applied, and the entire liquid crystal became black. FIG. 12 shows the viewing angle characteristics of the manufactured liquid crystal element, and Table 2 shows the evaluation results of electro-optical characteristics and visual display roughness. The electro-optical characteristic is that the transmittance of two polarizing plates whose polarization axes are parallel to each other is 100%.
It was expressed as a relative transmittance.

[0050]

[Table 2]

In FIG. 12, θ represents the angle (tilt angle) formed by the normal to the display surface and the viewing angle, and Ψ represents the azimuth angle of the viewing angle. FIG.
The hatched area indicates the area where the contrast ratio is 10 or more. From this, it is understood that the liquid crystal display element of the present embodiment can provide a display with excellent display quality in almost all viewing angle directions.

(Comparative Example 1) Spacers 157 were dispersed on a glass substrate with a transparent electrode similar to that of Example 1, and resist was applied thereto. Then, a light-shielding portion 131 and a light-transmitting portion 1 as shown in FIG.
Exposure using a photomask 130 having
The stepped pattern 152 was fabricated on the substrate 151a. Further, a resist is applied, and exposure is performed using a photomask 140 having a light-shielding portion 141 (picture element aspect ratio 1: 9) and a light-transmitting portion 142 shown in FIG. 14 as in Example 1, and as shown in FIG. A different pattern was formed on the substrate 151a to obtain the substrate 150. The height of the resist layer as the insulator wall was 2.5 to 2.7 μm.

Similar to Example 1, the counter substrate was formed to have a rectangular recess having an aspect ratio of 1: 2: area ratio of 30% at the center of the pixel. A liquid crystal cell was produced by bonding these substrates together. The cell gap D of the obtained liquid crystal cell is
It was 4.0 μm. Therefore, the minimum height Z of the insulator wall in this comparative example was (2.5 / 4.0) D = 0.625D.

Then, a mixture containing the same liquid crystal material and polymerizable resin material as in Example 1 was injected into the cell prepared by the vacuum injection method. Then, the same operation as in Example 1 was performed to form an axially symmetric orientation domain. When the liquid crystal drop deposited from the edge of the picture element due to the temperature drop contacts the liquid crystal drop in the center,
The size of each liquid crystal droplet was almost the same, and they fused in a state where the axially symmetric orientation was disturbed. When the liquid crystal droplets were fused and the size of the liquid crystal region became the size corresponding to the picture element, the photocurable resin was cured by irradiation with ultraviolet light to fix the alignment of the liquid crystal molecules. A liquid crystal display device was prepared by bonding two polarizing plates with their polarization axes orthogonal to each other to this cell. When applying a voltage to the liquid crystal display device and observing it obliquely in a halftone display state, a slight roughness was observed. Was given. Table 2 shows the evaluation results of the electro-optical characteristics of the liquid crystal device of Comparative Example 1.

Example 2 In this example, an example of producing a TFT color liquid crystal display element will be described.

OMR83 (15 cp) mixed with 0.5% by weight of plastic beads (diameter 4.0 μm) was applied to a TFT substrate having an aspect ratio (S: L) of picture elements of 1: 3, and it is shown in FIG. Exposure and patterning were performed using a photomask 160 having a light shielding portion 161 and a light transmitting portion 162.
After that, OMR83 (60 cp) was applied, and exposure and patterning were performed using a photomask 170 having a light shielding part 171 (aspect ratio (S: L) of 1: 3) and a light transmitting part 172 shown in FIG. The height of the resist layer is 2.
It was 8 to 3.0 μm.

Color filter substrate 19 which is a counter substrate
1-a is coated with V-259PA, the light-shielding portion 18 shown in FIG.
After patterning with a photomask 180 having a ratio of the major axis to the minor axis (S1: L1 is 3: 2, the area ratio to the pixel is 40%) to form a resist layer 192, I is formed on the substrate.
A TO thin film (not shown) was formed, and an opposing substrate 190 having a recess 196 was produced as shown in FIG. TF above
The T substrate and the counter substrate were bonded together in the same manner as in Example 1 to obtain T
An FT cell was prepared. The cell gap D of the obtained liquid crystal cell was 4.0 μm. Therefore, the minimum height Z of the insulator wall in this embodiment is (2.8 / 4.0) D = 0.7D.
Met.

Next, as a polymerizable resin material, 0.2 g of perfluorooctyl acrylate, 0.3 g of isobornyl acrylate and R-684 (manufactured by Nippon Kayaku Co., Ltd.) were used. l
g, 0.1 g of p-fluorostyrene as a photopolymerization inhibitor,
The polymerizable liquid crystal material shown in Chemical formula 1 is lg, ZLI-4792 (manufactured by Merck & Co., Inc .: containing 0.434% by weight of S-811) 4.25 g as a liquid crystal material, Ir as a photopolymerization initiator
A mixture was prepared by mixing 0.025 g of guacure 651, and the mixture was injected into the produced TFT cell using a vacuum injection method. Then, an axially symmetric alignment domain was formed in the same manner as in Example 1, and the photopolymerizable resin was cured by irradiation with ultraviolet light to produce a liquid crystal display element.

When the obtained liquid crystal cell was observed under a polarization microscope, the polymer region 2 was observed in the same manner as in Example 1 (FIG. 11).
The liquid crystal region 23 surrounded by 4 was in a mono-domain state for each pixel 10 and was aligned in a relatively uniform axial symmetry in which no alignment disorder due to spacers was observed in the pixel 10. Further, in observation with a polarizing microscope, when two polarizing plates whose polarization axes are orthogonal to each other were fixed and the produced liquid crystal cell was rotated, the position of the extinction pattern 26 in the liquid crystal region 23 was constant and the surrounding polymer wall Only 24 were observed to rotate. From this, it was found that uniform axially symmetric alignment was obtained in almost all liquid crystal regions. As shown in Table 1, in the liquid crystal cell according to this example, an axially symmetric alignment domain was formed in 98% of the picture elements, and
No injection failure was observed.

Two polarizing plates were made to cross each other with the liquid crystal cell sandwiched therebetween and bonded to each other to prepare a liquid crystal display element, and electro-optical characteristics were measured. The results are shown in Table 2. In addition, when applying a voltage and observing by tilting the viewing angle in the halftone display state, there was no roughness.

Comparative Example 2 As in Example 2, OMR83 (15 cp) mixed with 0.5% by weight of plastic beads (diameter 4.0 μm) was applied, and the light-shielding portion 161 and the light-transmitting portion shown in FIG. 16 were applied. Exposure and patterning were performed using a photomask 160 having 162. After that, the same resist was applied, and exposure and patterning were performed using a photomask 170 having a light shielding portion 171 and a light transmitting portion 172 shown in FIG. The height of the obtained resist layer is 2.0 to 2.1 μm.
m. A counter substrate was prepared in the same manner as in Example 2, and a TFT cell was prepared by bonding the opposite substrate to the above substrate. The cell gap D of the obtained liquid crystal cell was 4.0 μm. Therefore, the minimum height Z of the insulator wall of this comparative example is (2.0 /
4.0) .D = 0.5D.

Next, in the same manner as in Example 2, a material was injected to form an axially symmetric alignment domain, and the photopolymerizable resin was cured by irradiating with ultraviolet rays to produce a liquid crystal display element.

When the obtained liquid crystal cell was observed under a polarizing microscope, many locations where liquid crystal orientation was continuous between the picture elements were observed, and an axially symmetric orientation domain was formed for each picture element. There were few places. As shown in Table 1, in the liquid crystal cell according to this comparative example, although no injection failure was observed, it was found that the axisymmetric alignment domain was formed only in 68% of the picture elements. Two polarizing plates were attached so as to be orthogonal to each other with the liquid crystal cell sandwiched therebetween to produce a liquid crystal display element, and the display quality was visually evaluated. As a result, it was found that in the halftone display state, the screen was very rough and the display quality was low.

(Comparative Example 3) In the same manner as in Example 1, the first
A step resist was formed. Then, a second resist layer thicker than that in Example 1 was formed. The thickness of the resist layer can be controlled, for example, by adjusting the rotation speed of the spinner. The height of the resist layer obtained in this comparative example was 3.2 to 3.5 μm.

Next, a counter substrate was formed in the same manner as in Example 1 and was bonded to the substrate on which the above resist layer was formed to prepare a liquid crystal cell. The cell gap D of the obtained liquid crystal cell was 4.0 μm. Therefore, the minimum height Z of the insulator wall in this comparative example is (3.2 / 4.0) D = 0.
It was 8D. An attempt was made to inject a material into this cell by a vacuum injection method, but a part of the resist layer was in contact with the counter substrate, and the material could not be completely injected (see Table 1).

[0066]

According to the present invention, according to the present invention, it is possible to obtain an OA device such as a personal computer or a liquid crystal element having a wide viewing angle and high brightness corresponding to a long picture element for car navigation. . In addition, it is possible to obtain a high-quality display with high contrast without roughness of the display, particularly in the halftone, by suppressing the occurrence of poor alignment of the liquid crystal in the picture element, defective alignment axis, or disclination. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a viewing angle characteristic of an axially symmetric orientation domain in a long picture element.

FIG. 2 is a schematic view of an observation example of a polarization cervix microscope of an axially symmetric alignment domain of a liquid crystal device according to the present invention. (A) is when the power is off,
(B) is when the power is on.

FIG. 3 is a schematic diagram for explaining viewing angle dependence of display quality of a liquid crystal display device according to the present invention.

FIG. 4 is a cross-sectional view of a substrate having a mortar-shaped cross-section concave portion used in the liquid crystal display element of the present invention.

FIG. 5 is a simplified diagram of a photomask 50 used in the first embodiment.

6 is a diagram showing a substrate having a resist layer patterned by the photomask 50 of FIG. (A) is a top view,
6B is a sectional view taken along line 6B-6B ′ of FIG.

FIG. 7 is a simplified diagram of a photomask 70 used in the first embodiment.

8 is a diagram showing a substrate having a resist layer patterned by the photomask 70 of FIG. (A) is a top view,
8B is a sectional view taken along line 8B-8B ′ of FIG.

FIG. 9 is a simplified diagram of a photomask 90 used in the first embodiment.

10 is a diagram showing a substrate having a resist layer patterned by the photomask 90 of FIG. (A) is a top view,
10B is a sectional view taken along the line 10B-10B ′ in FIG.

FIG. 11 is a diagram in which a picture element portion of the liquid crystal display element of Example 1 is observed with a polarization microscope.

FIG. 12 is a diagram showing the viewing angle dependence of the contrast of the liquid crystal display element of Example 1.

FIG. 13 is a simplified diagram of a photomask 130 used in Comparative Example 1.

FIG. 14 is a simplified diagram of a photomask 140 used in Comparative Example 1.

15 is a diagram showing a substrate having a resist layer patterned by the photomask 140 of FIG. (A) is a top view, (b) is a 15B-15B 'sectional view of (a).

FIG. 16 is a simplified diagram of a photomask 160 used in the second embodiment.

FIG. 17 is a simplified diagram of a photomask 170 used in Example 2.

FIG. 18 is a simplified diagram of a photomask 180 used in the second embodiment.

19 is a diagram showing a substrate having a resist layer patterned by the photomask 180 of FIG. (A) is a top view, (b) is a 19B-19B 'sectional view of (a).

FIG. 20 is a schematic diagram for explaining a change in contrast depending on the viewing angle of a conventional TN LCD.

FIG. 21 is an observation view with a polarizing head-penetrating mirror showing an axially symmetric alignment defect in a long picture element.

[Explanation of symbols]

 10 pixel 23 liquid crystal area 24 polymer area 25 disclination line 26 extinction pattern 31a, 31b substrate 32 liquid crystal layer

Claims (13)

[Claims] 1. A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of transparent substrates, at least one of which is opposed to each other, wherein the liquid crystal layer has a plurality of axes in which liquid crystal molecules are oriented in axial symmetry. A liquid crystal display device having a symmetrical alignment domain, wherein the axially symmetrical alignment domain has an aspect ratio of more than 1: 1 and not more than 1: 6. 2. The liquid crystal display device according to claim 1, wherein each of the plurality of axially symmetric alignment domains is surrounded by a polymer region. 3. The liquid crystal display device according to claim 1, wherein each of the plurality of axially symmetric alignment domains is formed corresponding to a pixel of the liquid crystal display device. 4. A wall made of an insulating material is provided around the plurality of axially symmetric orientation domains, and a minimum height Z of the wall is within a range of 0.5 × D <Z <0.8 × D with a cell gap D. The liquid crystal display element according to claim 1, wherein the liquid crystal display element is a liquid crystal display element. 5. The liquid crystal display device according to claim 1, wherein the gap between the substrates is maximum near the center of the picture element. 6. The liquid crystal display element according to claim 1, wherein at least one of the pair of substrates has a recess near the center in the picture element. 7. The liquid crystal display element according to claim 6, wherein the area of the recess is 25% or more and 50% or less of the area of the picture element. 8. The liquid crystal display device according to claim 6, wherein the shape of the recess is elliptical or rectangular. 9. The liquid crystal display device according to claim 8, wherein the ratio of the major axis to the minor axis of the ellipse of the recess or the aspect ratio of the rectangle is larger than 1: 1 and smaller than the aspect ratio of the axisymmetric alignment domain. 10. The liquid crystal display element according to claim 6, wherein the recess has a mortar shape in cross section. 11. The liquid crystal display element according to claim 6, further comprising a transparent electrode on the recess. 12. The liquid crystal display device according to claim 6, wherein the recess is formed in a substrate having a color filter. 13. The method of manufacturing a liquid crystal display device according to claim 10, wherein a step of injecting a mixture of a liquid crystal material and a polymerizable material between a pair of substrates and phase separation of the mixture. A liquid crystal display including a step of applying a voltage to the mixture in a state where the diameter of the liquid crystal droplet formed by the phase separation is the same size as the short side of the pixel in the phase separation step. Device manufacturing method.