JP2000137229A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high image-quality liquid crystal display device in which the uniformity in cell gaps is satisfactory even in a large area and the reduction of contrast ratio due to the light leakages of surroundings of spacers at the time of displaying the dark is not generated in the liquid crystal display device of a traverse electric field system. SOLUTION: In a liquid crystal display device which is provided with one pair of substrates 1, 1' in which at least the substrate of one side is of transparent, a liquid crystal layer 32 which is held between one pair of the substrates 1, 1', electrode groups which are formed on the substrate of one side of the one pair of the substrates and impress electric fields roughly parallel with the substrates on the liquid crystal layer, orientation control films 8, 8' which are formed on surfaces which are in contact with the liquid crystal layer being on the one pair of the substrates, optical means 9, 9' changing optical characteristics in accordance with oriented states of molecules of the liquid crystal layer and spacers which control the thickness of the liquid crystal layer and are held between the substrates, the spacers are provided at only non- opening parts and one part of the spacer is constituted of a gloular spacer 30 and a resin pattern 33 embedding and fixing the spacer 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid display device, and more particularly to a liquid crystal layer formed by applying an electric field in a direction substantially parallel to a substrate by means of an electrode group formed on the same substrate. The present invention relates to a so-called in-plane switching type liquid crystal display device to be operated.

[0002]

2. Description of the Related Art In a liquid crystal display device, an electric field is applied to liquid crystal molecules of a liquid crystal layer sandwiched between a pair of substrates to change the alignment direction of the liquid crystal molecules, and the display is changed by the change in the optical characteristics of the liquid crystal layer. Is done.

In a conventional active matrix type liquid crystal display device, a direction of an electric field applied to the liquid crystal is set to a direction substantially perpendicular to a substrate surface, and a twisted nematic (TN) display in which display is performed by utilizing the optical rotation of the liquid crystal. System.

On the other hand, interdigital electrodes (Inter Digital Electron)
An in-plane switching method (In-Plane Switching: IPS), in which the direction of the electric field applied to the liquid crystal is made substantially parallel to the substrate surface using the birefringence of the liquid crystal, is used for the display.
No. 3-21907, US Pat. No. 4,345,249, WO91
/ 10936, JP-A-6-22397, JP-A-6-22397
No. 1,608,878. The horizontal electric field method has advantages such as a wide viewing angle and a low load capacity as compared with the TN method, and is an excellent technique as an active matrix liquid crystal display device.

In such a lateral electric field method, the electrode used is T
Since it is not necessary to be transparent as in the N type, an opaque metal electrode having high conductivity is usually used. Further, there are many light-shielding portions such as signal wiring electrodes, common electrodes in pixels, pixel electrodes, switching elements, and the like, and the aperture ratio of the pixel is generally lower than that of the TN method. Therefore, the influence on the display characteristics of a large number of spacer particles scattered between the substrates to secure the cell gap of the liquid crystal display device is larger than that of the TN method. In this case, the spacer particles are foreign matter inside the liquid crystal layer, and cause light leakage from the spacer itself and its surroundings.

In the conventional normally open TN method, a dark level can be obtained with a high voltage applied. In this case, most of the liquid crystal molecules are aligned in one direction of the electric field perpendicular to the substrate surface, so that a dark level can be obtained in relation to the arrangement of the liquid crystal molecules and the arrangement of the polarizing plate. Therefore, the display uniformity at the dark level does not depend much on the initial alignment state at the time of low voltage in principle.

[0007] Furthermore, human eyes recognize luminance unevenness as a relative ratio of luminance and respond to a logarithmic scale, so that they are sensitive to fluctuations in dark level. From this point of view, the normally open TN mode in which liquid crystal molecules are forcibly arranged in one direction at a high voltage is advantageous in terms of display because the initial alignment state is insensitive.

On the other hand, in the horizontal electric field method, since the display is of a normally closed type in which a dark level is displayed at a low voltage or at zero voltage, human eyes are sensitive to disturbances in the initial alignment state. Therefore, the presence of the spacer particles that greatly influences the initial alignment state is more affected by the normally closed lateral electric field method than by the normally open TN method even from the viewpoint of lowering the contrast ratio.

Under these circumstances, a lateral electric field type liquid crystal display device having a structure that does not use the dispersion of spacer particles has been proposed. For example, Japanese Patent Application Laid-Open No. Hei 6-214244 proposes a method in which both the common electrode and the pixel electrode are formed to be thick and also used as a spacer for securing a cell gap.

Japanese Patent Application Laid-Open No. 10-48636 discloses a method in which a columnar or hemispherical spacer formed of a color filter forming material or a resin constituting a light shielding layer (black matrix) is disposed near a switching element. Proposed. Further, an elliptic columnar spacer having a rubbing direction as a long axis has been proposed for the purpose of reducing the rubbing alignment processing failure due to such spacer projections.

Further, in Japanese Patent Application Laid-Open No. Hei 7-270807, a part of spherical particles of spacer particles is buried and fixed on a black matrix made of a resin formed in a region other than a region of a pixel electrode. Eliminating spacer particles to prevent light leakage during display by the particles
N-type liquid crystal display devices have been proposed.

[0012]

However, since display is performed using birefringence in the in-plane switching method, in order to obtain the same display characteristics as in the TN method, the gap between the substrates must be reduced.
It is necessary to set the so-called cell gap (the thickness of the liquid crystal layer) to about 4 μm, which is considerably smaller than the TN mode (about 10 μm).

In general, when the thickness of the liquid crystal layer is reduced, display unevenness due to a retardation effect or the like due to non-uniform cell gap becomes remarkable. Therefore, the uniformity of the cell gap is required in the in-plane switching method compared to the TN mode. ing. Therefore, it is required that the spacers have a uniform thickness equal to or greater than that of the conventional spacer particles having a uniform particle size distribution having a particle size variation of 0.05 μm or less. This is about 2 in the TN system.
That is, the uniformity is required to be twice or more.

In the method using no spacer particles, the thickness of a metal electrode or the thickness of a spacer formed using a material for forming a color filter or a resin for forming a light-shielding layer is spread over the entire surface of the substrate, and It is very difficult to control with a thickness below the variation in particle size. In particular, there is a problem that as the screen size increases, it becomes more difficult to make the heights of the spacers uniform, and it becomes more difficult to secure the thickness accuracy and uniformity of the cell gap.

Further, when the liquid crystal display device is exposed to a low temperature, there is a problem that bubbles are generated in the cell. It is said that this is caused by volume shrinkage of the liquid crystal at low temperatures, which cannot be followed by deformation of the cell gap.
A factor that hinders the deformation of the cell gap is a spacer. Therefore, when a very hard metal electrode is used as the spacer instead of the spacer particles as described above, the above problem cannot be solved.

Further, when a material for forming a color filter or a resin for forming a light shielding layer is used for the spacer, the above problem cannot be dealt with unless the thermal expansion coefficient and the compressive deformation rate of the resin are taken into consideration. There is.

An object of the present invention is to solve the above-mentioned problems of the prior art in the lateral electric field method, to provide a uniform cell gap even in a display cell having a large area, and to provide a contrast ratio due to light leakage around the spacer during dark display. It is an object of the present invention to provide a horizontal electric field type liquid crystal display device which has high quality image quality with no deterioration and is excellent in productivity.

[0018]

The gist of the present invention to achieve the above object is as follows.

[1] A pair of substrates, at least one of which is transparent, a liquid crystal layer sandwiched between the pair of substrates, and an electric field formed on one of the pair of substrates and substantially parallel to the substrate surface. An electrode group applied to the liquid crystal layer, an alignment control film formed on a surface of the pair of substrates in contact with the liquid crystal layer, an optical unit that changes optical characteristics according to a molecular alignment state of the liquid crystal layer, In a liquid crystal display device including a plurality of spacers sandwiched between the substrates for controlling the thickness of a liquid crystal layer, the spacers are provided only in the non-opening portions,
A liquid crystal display device, wherein a part of the spacer is formed of a spherical spacer and a resin pattern formed in a pattern for embedding and fixing the spherical spacer.

[2] The liquid crystal display device, wherein the spacer is formed only on the electrode group and / or its wiring electrode group.

[3] The liquid crystal display device according to the above, wherein the spacer is formed on a light-shielding layer (black matrix) or a protective film on the other substrate facing the substrate having the electrode group.

[4] The liquid crystal display device as described above, wherein the spacer forms a regular pattern with a photo-curable or thermosetting resin.

[5] The liquid crystal display device as described above, wherein the photo-curable or thermo-curable resin constituting the spacer is formed of the same resin as the resin constituting the color filter or the light shielding layer (black matrix).

[6] The liquid crystal display device as described above, wherein the end of the spacer has a forward tapered inclined surface having an inclination angle of 45 degrees or less or an aspect ratio (length / width) of 1 or less.

[7] At least the spacer is embedded,
The above-mentioned liquid crystal display device, wherein the fixed alignment control film on the substrate surface side is formed of a film formed of a photoreactive resin material and whose alignment direction is controlled by irradiation of linearly polarized light.

[8] The liquid crystal display device as described above, wherein the photoreactive resin material is an organic polymer material containing a polymer and / or an oligomer containing a diazobenzene group, a stilbene group or a derivative thereof.

[0027]

[9] The liquid crystal display as described above, wherein the polymer or oligomer contains an ethylene group, an acetylene group, a diacetylene group or a maleimide group.

[0028]

According to the present invention, the spacer is formed into a regular pattern by a photolithography process or the like, and a resin which is cured by light or heat only in a non-opening portion and spacer particles having a uniform particle size are mixed. It becomes possible to form it.

Further, the resin which forms the pattern and is cured by light or heat may be at least a resin constituting a color filter or the light shielding layer (black matrix). Examples of such resins include known photopolymerizable acrylic resins and polyimides.

According to the present invention, the uniformity of the cell gap is borne by the conventional spacer particles having a uniform particle size distribution, and the fixed pattern of the selectively disposed spacer particles in the non-opening portion is borne by the patterned resin. . The synergistic effect of the two can prevent the uniformity of the cell gap and the generation of bubbles and the like.

As a procedure for producing the spacer, a coating or printing film of a resin solution in which spacer particles having a uniform particle size distribution are mixed at a fixed ratio is produced, and the columnar spacer is formed by patterning by photolithography. . Alternatively, first, a coating film or a printed film of a resin solution is prepared, and spacer particles having a uniform particle size distribution are dispersed on the coating solution more than usual. After that, the columnar spacer is formed only in the non-opening portion by patterning by photolithography. Resin and spacer particles other than the spacer portion selectively patterned in the non-opening portion are removed from the substrate by a cleaning process.

Here, a spin coating method, a printing method, or the like is employed as a method for producing a thin film using a resin solution, but a thin film may be formed by bonding a film of a photocurable resin. In this case, it is necessary to select a material having good adhesion to the substrate.

Furthermore, according to the present invention, the end of the spacer has an inclination angle of 45 degrees or less or an aspect ratio (vertical / vertical).
A (horizontal) ratio of a forward taper of 1 or less is formed. In particular, those having an inclination angle of 45 to 10 degrees are preferable from the viewpoint of forming a photo-alignment film described later.

Usually, an alignment film is formed on a substrate provided with such spacers, and an alignment process is performed by rubbing. At this time, the spacer acts as a projection that gives a large frictional resistance, and may hinder the rubbing process. However, rubbing failure can be reduced by forming the above-described inclined surface at the end of the spacer.

Further, in the rubbing treatment, since a stress is applied from one direction by a fiber bundle or the like as a rubbing means, the resin strength is extremely thin, and mechanical strength such as insufficient embedding of spacer particles is low. In a sufficient portion, such rubbing treatment may cause separation or detachment of spacer particles. Therefore, it is desirable that the spacers arranged on the substrate in a regular pattern have a particle size of 1/3 or more to less than the particle size of the embedded spacer particles.

As the alignment treatment, a photo-alignment method other than the rubbing method is known. However, when the alignment film is formed after the spacer is provided, the light alignment is disturbed by light reflection or interference from the surface of the spacer serving as a protrusion. Therefore, by providing a forward tapered inclined surface of 45 degrees or less at the end of the protrusion of each spacer as in the present invention, reflected light from the spacer protrusion does not become irregular reflection on the surface of the alignment film in the display region. It is possible to irradiate uniform light in a certain direction up to
It is much more preferable than the alignment treatment method by the rubbing method.

In such a photo-alignment method, an azobenzene group, a stilbene group or the like is introduced as a photo-alignment film and a photoisomerization reaction is used. However, in this case, adhesion and coloring between the alignment film material and the substrate pose a problem. This can be solved by interposing a transparent organic polymer layer thicker than the alignment control film between the alignment control film and the substrate. Since this organic polymer layer has a certain thickness, it has an effect of reducing distortion caused by a temperature change or the like.

It is desirable that the transparent organic polymer layer and the orientation control film are made of polyimide, since the adhesion is further enhanced.

Alternatively, the thickness of the orientation control film is set to 0.04 to 0.0.
The thickness of 3 μm is preferable because the forward tapered inclined surface formed at the end of the spacer projection functions more effectively.
The orientation control film is coated with a soluble polyimide having a concentration of 1 to 15% by weight, and is heated to a temperature at which the solvent evaporates. When a polyamic acid is used, the temperature is raised to a temperature at which imidization is possible to obtain a polyimide. next,
The present invention will be specifically described with reference to examples.

[0040]

[Embodiment 1] FIG. 1 is a schematic sectional view of a liquid crystal display device according to an embodiment of the present invention. A liquid crystal layer 32 is sandwiched between a pair of transparent substrates 1 and 1 ', and the orientation direction of liquid crystal molecules 6 in the liquid crystal layer 32 is schematically shown. Polarizing plates 9, 9 'are arranged on both outer sides of the substrates 1, 1'. A common electrode 2 and a pixel electrode 3 formed in a stripe shape on a surface of the substrate 1 inside the cell, and an insulating layer 4 is formed thereon. An orientation control film 8 is formed on the insulating layer 4.

The common electrode 2 is an electrode for applying a voltage having a fixed waveform independent of an image signal, and the pixel electrode 3 is an electrode for applying a voltage whose waveform changes according to an image signal.
The video signal electrode 10 is arranged at the same height as the pixel electrode 3.

Each of the pixel electrode 3 and the video signal electrode 10 has a thickness of 0.2 μm. Although the insulating layer 4 is formed in two layers in this embodiment, both are formed of a silicon nitride film, and each has a thickness of 0.4 μm.

A color filter 5 for performing color display was formed on the other substrate 1 'opposite to the substrate.

As the color filter 5, red, green, and blue organic pigments are processed in the order of red, green, and blue according to the procedure of resist coating, exposure, and development and normal photolithography using an acrylic resin resist. , And a film thickness of about 2 μm.

On the substrate 1 'on which the color filter 5 is formed, a boundary of red (R), green (G) and blue (B), which are the three primary colors, is coated with a mixture of a resin and a black pigment. A black matrix 28 serving as a configured light shielding layer is formed,
The black matrix 28 was formed thicker than any of the three primary color filter portions. Further, a protective film 7 made of a transparent organic polymer layer was formed on the surface of the black matrix 28 and the color filters 5 of the three primary colors.

An acrylic (epoxy) resin is applied as the protective film 7 and has a thickness of about 2 μm so that the surface is flat.

As the black matrix, a black photosensitive resist mainly composed of an acrylic resin in which carbon and an organic pigment were mixed was applied, and formed into a lattice pattern having a thickness of about 1.2 μm by photolithography.

As the non-opening portion, there are light-shielding portions such as signal wiring electrodes, common electrodes in pixels, pixel electrodes, and switching elements. Here, a black matrix which is a light-shielding portion on a color filter substrate is selected. A spacer was formed.

A uniform spherical spacer 30 having a spherical diameter of 3.8 μm is embedded and fixed on the protective film 7 on the black matrix 28. The resin is made of an ultraviolet curable resin of about 10 μm square and about 1.5 μm thick. Patterns 33 (see FIG. 3 for the pattern shape) were formed at a rate of four per pixel with regularity.

The spherical spacer 3 is provided in the resin pattern 33.
The number of patterns containing 0 particles is about two per pixel on average, and these are almost uniformly distributed over the entire panel.
In rare cases, two spherical spacers 3
0 may be buried.

In a negative photosensitive resin solution having a resin concentration of about 20% by weight, a resin-made spherical spacer is uniformly blended at a rate of about 30% by weight, and the resultant is coated on a substrate and prebaked to form a spherical shape. Approximately 1.9μm with spacers mixed
Was formed.

Next, exposure, development and cleaning were performed using a mask of the resin pattern 33, and a resin pattern 33 having a thickness of about 1.5 μm in which spherical spacers were embedded was formed by post-baking.

As another method, a resin concentration of about 20
A weight-% negative photosensitive resin solution is applied on the entire surface of the substrate, prebaked, and then a resin-made spherical spacer is scattered from above and pressed to form a thin film having a thickness of about 1.9 μm in which the spherical spacers are mixed. did.

Next, exposure, development and cleaning treatment are performed using a mask of the resin pattern 33, and a resin pattern 3 having a thickness of about 1.5 μm in which the spherical spacers are embedded in the same manner as described above.
3 was formed.

The thickness of the resin pattern 33 is determined by cutting a sample for measurement from the substrate and using a stylus-type film thickness measuring device (a stylus-type surface step meter) and a scanning atomic force microscope. The irregularities on the surface of No. 33 were measured, and the film thickness was calculated from the results.

In this manner, on the insulating layer 4 covering the pixel electrode 3 and the video signal electrode 10, the protective film 7 on the black matrix 28, and the resin pattern 33 in which the spherical spacer 30 is embedded, and the pixel region The orientation control films 8, 8 'are formed by coating. The thickness of the alignment control films 8, 8 'was 0.12 [mu] m. However, the thickness of the orientation control film on the electrode and on the resin pattern 33 in which the spherical spacers 30 are embedded is slightly thinner due to the fluidity of the varnish at the time of coating the varnish for forming the film, and the former is about 0.08 μm and the latter is about 0.08 μm. Was about 0.06 μm.

The alignment control films 8, 8 'are coated with an 8% solution of a polyamic acid as a polyimide precursor,
Baking at 30 ° C. for 30 minutes for imidization. The polyamic acid was synthesized using 4,4′-diaminodiphenylmethane, pyromellitic dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride.

Rubbing treatment is performed on the alignment control film 8 using a buff cloth made of rayon fiber so that the major axis direction of the liquid crystal molecules to be aligned is at an angle Φ _LC = 75 degrees defined in FIG. did.

Thereafter, the upper and lower substrates were overlapped, and the peripheral portion was sealed with a sealant of an epoxy-based material to assemble an empty cell. The liquid crystal composition is sealed therein at room temperature, and then annealed at 100 ° C. for 10 minutes.
Good liquid crystal alignment was obtained.

As described above, when the thickness d of the liquid crystal layer is 4.
A liquid crystal display of 0 μm was obtained. A nematic liquid crystal having a positive dielectric anisotropy was used as the liquid crystal composition. The value of the dielectric anisotropy Δε of the nematic liquid crystal is 10.2, and the refractive index anisotropy Δn
Is 0.073.

FIG. 5 is a schematic sectional view for explaining the switching principle of the liquid crystal molecules in the panel thus obtained.

In this embodiment, as shown in FIGS. 5A and 5C, when no electric field is applied, the liquid crystal molecules 6 are Φ _LC = 75 with respect to the vertical direction of the stripe-shaped electrodes 2 and 3 in the longitudinal direction. was such that the degree, if the dielectric anisotropy is positive liquid crystal, 45 ° ≦ | Φ _LC | <should be such that 90 degrees. Further, the liquid crystal composition in FIG. 5 may have a negative dielectric anisotropy. In this case, the initial alignment state is set at 0 ° ≦ from the direction perpendicular to the stripe electrode.
| Φ _LC | <45 degrees. In FIG. 5, the orientation direction 11 is indicated by an arrow.

Next, FIGS. 5B and 5D show electrodes 2 and 3 respectively.
The case where the electric field 13 is applied during the period is shown. The direction of the liquid crystal molecules 6 is changed in the direction of the electric field 13 so that the long axes of the molecules become parallel, thereby changing the light transmittance.

In this embodiment, the liquid crystal cell is interposed between the orthogonal polarizing plates 9 and 9 because the display system of the birefringence mode is adopted. Further, in order to obtain a normally closed characteristic in which dark display is performed at a low voltage, the polarization transmission axis of one of the polarizing plates is orthogonal to the initial alignment direction of the liquid crystal.

FIG. 6 shows a circuit configuration in the liquid crystal display device of this embodiment. Vertical scanning signal circuit 17, video signal circuit 1
8, a common electrode driving circuit 19, a power supply circuit, and a controller 20; however, the present invention is not limited to this configuration.

FIG. 7 shows the configuration of an optical system in the liquid crystal display device of this embodiment. On the back of the liquid crystal panel 27,
A backlight unit 26 including a light source 21, a light cover 22, a light guide 23, and a light diffusion sheet 24 is provided.

Here, a condensing sheet 25 made of a prism sheet for increasing the front luminance is provided. The condensing sheet 25 does not have to be provided. Rather, it is preferable not to reduce the viewing angle dependency of luminance.

This embodiment is characterized in that, as shown in FIG. 1, in order to control the thickness of the liquid crystal layer 32 uniformly, a regular resin pattern That is, a spacer composed of a resin pattern 33 in which spacer particles having a uniform particle size are embedded in the pattern is formed. As a result, the gap accuracy of the liquid crystal cell of the present example was 3.8 ± 0.1 μm, and the variation in the cell gap was almost the same as that in the case where the ordinary spherical spacer particles were dispersed.

From the above, it can be seen that almost all of the spherical spacers existing on the substrate contribute to the cell gap control, and the cell gap control functions more effectively than in the case of the ordinary dispersion method. In addition, by disposing the spacer only in the non-opening portion, it is possible to prevent the liquid crystal alignment disorder due to the spacer existing in the conventional display area and the accompanying light leakage, and the liquid crystal display with a good dark level and a high contrast ratio. The device was obtained.

Further, the liquid crystal cell of this embodiment was set to -3 in a cold room.
After storage at 0 ° C. for 4 hours, no noticeable air bubbles were generated.

Further, by giving a 43-45 degree inclination angle to the end of the resin pattern 33 in which the spherical spacers are embedded, friction during rubbing alignment processing is reduced, and alignment disturbance of liquid crystal which is considered to be caused by rubbing defects is almost eliminated. I was not able to admit.

The thickness of the resin pattern 33 of this embodiment is about 1.5 μm, and the spherical spacer particles having a diameter of 3.8 μm are firmly held and buried, and no desorption during rubbing is observed. Was.

As described above, a liquid crystal display device of a horizontal electric field type having a diagonal of 13.3 inches and the number of pixels of 1,024 × RGB × 768 was produced.
Thus, a liquid crystal display device which exceeded 00 and had good display uniformity was obtained.

The contrast ratio was determined by measuring the luminance at a liquid crystal driving voltage of 0 V or 6 V using a luminance meter after manufacturing the liquid crystal display device, and calculating the contrast ratio from the average of the luminance ratios.

[Embodiment 2] FIG. 2 is a schematic sectional view of a liquid crystal display device of this embodiment. The side of the substrate 9 having an electrode group for applying a parallel electric field to the liquid crystal layer 32 (on the electrode wiring portion)
In the second embodiment, a resin pattern 33 in which a spherical spacer 30 is embedded is formed.

Using this, a lateral electric field type liquid crystal display device having a diagonal of 13.3 inches and the number of pixels of 1,024 × RGB × 768 was produced. A high contrast ratio exceeding 250 over the entire surface was obtained. In addition, a liquid crystal display device having good display uniformity was obtained.

[Comparative Example 1] In Examples 1 and 2, the resin pattern 33 in which a spherical spacer was embedded was used as a spacer. In this comparative example, as shown in FIG. The columnar spacer 31 was formed with regularity. It is the same as the first embodiment except that the columnar spacer 31 is used.

A liquid crystal display device of a lateral electric field type having a liquid crystal layer thickness of 3.7 μm, a diagonal of 13.3 inches, and a number of pixels of 1,024 × RGB × 768 was produced. Brightness unevenness considered to be caused by cell gap variation was observed over the entire panel. In particular, the uneven brightness was remarkable in the halftone display.

When the height of the columnar spacer 31 was measured, it was found that it had a height distribution of 3.9 ± 0.25 μm, which was relatively high near the center of the substrate and decreased toward the periphery. . Further, when stored in a cold storage at -30 ° C for 4 hours, generation of bubbles having a diameter of several μm was confirmed.

The height of the columnar spacer 31 was measured in the same manner as the thickness measurement of the resin pattern.

The generation of air bubbles after storage in the cold storage at -30 ° C. for 4 hours was confirmed by visual observation when the entire surface was turned on. When air bubbles are generated, small air bubbles generally gather and grow into large air bubbles, depending on the size of the air bubbles. In addition, since the bubble portion which has exceeded the height is observed as a black point through which light does not pass during lighting because there is no liquid crystal, it can be easily confirmed visually.

Comparative Example 2 A spherical spacer 30 having a particle diameter of 4.2 μm is buried on the scanning electrode 14 and the common electrode 2 by photolithography in the same manner as in Example 2 except for the shape and arrangement of the used spacer. A resin pattern 33 having a thickness of about 0.6 μm was formed with regularity, and was configured as shown in the schematic diagram of FIG.

FIG. 3A is a plan view seen from a direction perpendicular to the panel surface, and FIGS. 3B and 3C are side sectional views. One pixel is divided into four by a video signal electrode 10 and a common electrode 2 and a pixel electrode 3 parallel to the video signal electrode 10.

When a liquid crystal display device of a lateral electric field type having a diagonal of 13.3 inches and a number of pixels of 1,024 × RGB × 768 was manufactured with the thickness of the liquid crystal layer being 4.0 μm, it was thought that the difference was caused by cell gap variation. Possible uneven brightness was observed on the entire panel. In particular, the uneven brightness was remarkable in the halftone display.

Observation of the region where the luminance unevenness has occurred by microscopy reveals that the area frequently occurs around the resin pattern 33 formed with regularity in order to bury the spacers, and the buried spherical spacers are found. There were many traces of peeling. From this, it is considered that the uneven brightness generated in this comparative example was due to the lack of the thickness of the resin pattern, in which the particles of the spherical spacer 30 supposed to be embedded and fixed were peeled off by the rubbing treatment.

Example 3 Equimolar mixture of 4,4'-diaminoazobenzene and 4,4'-diaminodiphenylmethane, and pyromellitic dianhydride and 1,2,3,4-cyclobutane as acid anhydrides A polyamic acid was synthesized using tetracarboxylic dianhydride, applied to the surface of the substrate, baked at 200 ° C. for 30 minutes, and imidized to form an alignment control film. Other than that is the same as the first embodiment.

The resin pattern 33 formed on the protective film 7 on the black matrix 28 with the spherical spacers buried and formed regularly has an angle of about 40 degrees at the end of the tapered inclined surface and an aspect ratio of about 40 degrees. A forward taper having a ratio of about 0.84 was formed.

A resin pattern 3 is applied to a coating film made of a photosensitive resin.
By adjusting the focus at the time of exposure using the mask 3, a tapered inclined surface can be formed at the end of the resin pattern 33 after exposure, development, and baking.

When the exposure is defocused, light leaks from the end of the mask and apparently the resolution is reduced. As a result, the inclination angle is small and the aspect ratio (length / width) is small. .

In this example, after the defocus exposure of the photosensitive resin pattern, a heat treatment at 230 ° C. for 30 minutes was performed to obtain an inclination angle of 40 ° and an aspect ratio of about 0.84. The same inclination angle and aspect ratio as described above can also be obtained by performing a two-stage heat treatment at 120 ° C./30 minutes and 230 ° C./30 minutes as a post-baking process after exposure processing under normal exposure conditions. It is possible.

This angle was obtained by calculating the inclination angle of the end of the section from a scanning electron microscope having a sectional shape.

Using a high-pressure mercury lamp having a wavelength of 436 nm as a light source, a linearly polarized light was irradiated through a polarizing plate to perform a photo-alignment treatment. The irradiation light amount is about ² J / cm ² . Then
The upper and lower substrates were overlapped, and the periphery was sealed with an epoxy-based sealant to assemble an empty cell.

A nematic liquid crystal having a positive dielectric anisotropy was sealed in this cell in the same manner as in Example 1, and then annealed at 100 ° C. for 10 minutes so that the liquid crystal molecules were substantially perpendicular to the above-mentioned irradiation polarization direction. A liquid crystal display device with uniformly aligned optical alignment was obtained. The thickness of the liquid crystal layer 32 of the liquid crystal display device is 4.0 μm.

As a result, a horizontal electric field type liquid crystal display device having a diagonal of 13.3 inches and the number of pixels of 1,024 × RGB × 768 was manufactured. As a result, there was no luminance unevenness and the contrast ratio exceeded 300 over the entire surface. A liquid crystal display device having good display uniformity was obtained.

Comparative Example 3 In this comparative example, a resin pattern 33 was formed on the protective film 7 on the black matrix 28 with regularity by burying the spherical spacer 30. At the end of the resin pattern 33, the taper inclination angle is about 60 degrees,
A forward taper having an aspect ratio of about 1.73 was formed in the same manner as in Example 3.

Other than the above, the diagonal is 1 as in the third embodiment.
An in-plane switching mode liquid crystal display device having a size of 3.3 inches and a pixel count of 1,024 × RGB × 768 was manufactured.

Observation of the liquid crystal display device revealed that the display region had a disordered orientation in the display region with a certain regularity over the entire surface. Observation of this poorly-aligned portion with a microscope revealed that it was just generated around the resin pattern formed with regularity.

As described above, the poor alignment that occurred in this comparative example is caused by the fact that the linearly polarized light irradiated for optical alignment is reflected on the tapered inclined surface (tilt angle: about 60 degrees) at the end of the resin pattern 33, and It was found that the alignment disorder was caused by irradiation of the photo-alignment film in the region.

[0099]

According to the present invention, it has a wide viewing angle characteristic,
In the active matrix type liquid crystal display device of the in-plane switching method suitable for large-screen display, the uniformity of the cell gap is good even in a large area, and the high-quality display does not cause a decrease in the contrast ratio due to light leakage around the spacer during dark display. A liquid crystal display device having image quality and excellent productivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an embodiment of a liquid crystal display device of a horizontal electric field type according to the present invention.

FIG. 2 is a schematic sectional view of one embodiment of a liquid crystal display device of a horizontal electric field type according to the present invention.

FIG. 3 shows an electrode group of a unit pixel portion used in a comparative example of the present invention;
It is a schematic diagram of a plane and a cross section showing the arrangement of an insulating film and an orientation control film.

FIG. 4 is an explanatory diagram for explaining an angle between a liquid crystal molecule long axis direction and a polarizing plate transmission axis with respect to an electric field direction.

FIG. 5 is a schematic cross-sectional view illustrating the operation of liquid crystal molecules in a liquid crystal display device of a horizontal electric field type.

FIG. 6 is a circuit configuration diagram illustrating an example of a circuit configuration of the liquid crystal display device of the present invention.

FIG. 7 is a schematic sectional view showing an example of a configuration of an optical system of the liquid crystal display device of the present invention.

FIG. 8 is a schematic sectional view of a liquid crystal display device of a comparative example.

[Explanation of symbols]

1, 1 '... substrate, 2 ... common electrode, 3 ... pixel electrode, 4,
4 ': insulating layer, 5: color filter, 6: liquid crystal molecule, 7
... Protective film, 8,8 '... Orientation control film, 9,9' ... Polarizing plate,
Reference Signs List 10: video signal electrode, 11: rubbing direction, 12: polarizing plate transmission axis direction, 13: electric field direction, 14: scanning electrode (gate wiring electrode), 15: TFT element, 16: amorphous silicon (a-Si), 17 ... vertical scanning signal circuit, 18
... Video signal circuit, 19 ... Common electrode driving circuit, 20 ... Power supply circuit and controller, 21 ... Light source, 22 ... Light cover, 23 ... Light guide, 24 ... Light diffusion sheet, 25 ... Condensing sheet, 26 ... Back Light unit, 27 liquid crystal panel, 28 black matrix, 30 spherical spacer, 31 columnar spacer, 32 liquid crystal layer, 33 resin pattern.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hidetoshi Abe 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory, Ltd. (72) Inventor Katsumi Kondo 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 F term in Hitachi Research Laboratory, Hitachi, Ltd. (reference) 2H089 LA07 LA09 LA16 LA19 LA20 NA05 NA24 PA05 QA12 QA14 QA15 RA05 SA01 SA03 TA01 TA02 TA04 TA09 TA12 TA13 TA17 TA18 TA20

Claims (9)

[Claims] 1. A pair of substrates, at least one of which is transparent;
A liquid crystal layer sandwiched between the pair of substrates, an electrode group formed on one of the pair of substrates and applying an electric field substantially parallel to the substrate surface to the liquid crystal layer, and the electrode group on the pair of substrates; An alignment control film formed on a surface in contact with a liquid crystal layer, an optical unit that changes optical characteristics according to a molecular alignment state of the liquid crystal layer, and a plurality of substrates sandwiched between the substrates that control the thickness of the liquid crystal layer. In a liquid crystal display device provided with a spacer, the spacer is provided only in the non-opening portion, and a part of the spacer is formed of a spherical spacer and a resin pattern formed in a pattern for embedding and fixing the spherical spacer. A liquid crystal display device characterized by the above-mentioned. 2. The method according to claim 1, wherein the spacer is formed only on the electrode group and / or its wiring electrode group.
3. The liquid crystal display device according to 1. 3. The substrate according to claim 1, wherein the spacer is formed on a light-shielding layer (black matrix) or a protective film on the other substrate facing the substrate having the electrode group.
3. The liquid crystal display device according to 1. 4. The liquid crystal display device according to claim 1, wherein the spacer has a regular pattern made of a photocurable or thermosetting resin. 5. The liquid crystal display according to claim 4, wherein the photo-curing or thermosetting resin forming the spacer is formed of the same resin as the resin forming the color filter or the light shielding layer (black matrix). apparatus. 6. The spacer according to claim 1, wherein an end portion of the spacer has a forward tapered inclined surface having an inclination angle of 45 degrees or less or an aspect ratio (length / width) of 1 or less. Liquid crystal display. 7. An alignment control film at least on a substrate surface on which the spacers are embedded and fixed, the alignment control film being made of a photoreactive resin material and having an alignment direction controlled by irradiation with linearly polarized light. Item 7. A liquid crystal display device according to any one of Items 1 to 6. 8. The liquid crystal display device according to claim 7, wherein the photoreactive resin material is an organic polymer material containing a polymer and / or an oligomer containing a diazobenzene group, a stilbene group or a derivative thereof. 9. The liquid crystal display according to claim 8, wherein the polymer or oligomer contains an ethylene group, an acetylene group, a diacetylene group or a maleimide group.