JPH0950034A - Liquid crystal display device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which is wide in a visual field angle and is free from display defects and a process for production capable of efficiently producing this liquid crystal display device. SOLUTION: This device includes first and second substrates 11, 11 respectively having oriented films on the main surfaces on one side and a liquid crystal material held between the first and second substrates 11 and 11 arranged in such a manner that these oriented films face each other. The oriented film of the first substrate 11 is segmented to a first region and the second regions inducing the pretilt angle smaller than the pretilt angle of the liquid crystal molecules induced in this first region. Further, the oriented film described above is laminated films composed of a first org. high-polymer film 12 which is thermally stable and a second org. high-polymer film 14 which is formed on this org. high-polymer film and is thermally or optically stable. The first and second substrates 11, 11 are so arranged that the liquid crystal material described above has spray deformation distortions. At this time, the pretilt angles are lowered by partially subjecting the surfaces of the oriented films to a heat treatment, such as irradiation with lasers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION Liquid crystal display devices are thin and can be driven at a low voltage, and are therefore widely used as display devices for wrist watches, calculators and the like. In particular, a TN type liquid crystal display device incorporating an active switching element such as a TFT (thin film transistor) exhibits a display characteristic comparable to that of a CRT,
Type liquid crystal display devices are capable of high-duplex multiplex driving, and are therefore being used for word processors, personal computer displays, televisions, and the like.

However, the TN type liquid crystal display device has drawbacks that the viewing angle is narrow and the light utilization efficiency is low. The viewing angle characteristics of the TN type liquid crystal display device are determined by the rising direction of liquid crystal molecules when a voltage is applied. That is, when the TN type liquid crystal display device is viewed obliquely, when the liquid crystal molecules rise, the voltage-transmission characteristics are observed differently when viewed from the long axis direction and the uniaxial direction. Therefore, the contrast of the TN type liquid crystal display device depends on the viewing direction of the screen, and the viewing angle is generally narrower than that of the CRT. For example, when the TN type liquid crystal display device is viewed obliquely from above, the entire screen looks whitish, and when viewed obliquely from below, the entire screen appears to be blackened. Thus, when the TN type liquid crystal display device is viewed obliquely, the contrast decreases.

Further, when halftone display is performed by a TN type liquid crystal display device, color inversion (gradation inversion) occurs when the TN type liquid crystal display device is viewed obliquely from below. For example, when a person is displayed and viewed from diagonally below, the phenomenon of black and white reversal occurs, in which the skin color looks black and the hair color looks white.

From these points, when evaluating the viewing angle of a liquid crystal display device, the viewing angle width is quantified at an angle at which a contrast of 5: 1 or more is obtained or at an angle at which gradation inversion does not occur. .

As a method of widening the viewing angle, an attempt has been made to mutually compensate for the difference in the viewing angle in the in-plane direction by changing the rising direction of liquid crystal molecules within the pixel. There are various methods for changing the rising direction of such liquid crystal molecules within a pixel. For example, the first rubbing alignment treatment is applied to the entire alignment film, and then a photoresist is applied onto the alignment film. Exposure and development are performed so that the resist remains only in a half area of each pixel.

At this time, the alignment film in the 1/2 area of each pixel is masked by the photoresist, and the alignment film in the remaining 1/2 area is exposed. A second rubbing alignment treatment is performed on the exposed alignment film from a direction different from the rubbing alignment treatment direction by 180 °. After that, the photoresist formed in the half area of each pixel is removed. As a result, two regions whose rubbing directions are different from each other by 180 ° are formed in one pixel.

In this way, two substrates in which two regions having different rubbing directions different by 180 ° are formed in one pixel are arranged opposite to each other to assemble a cell. Since the rising direction of the liquid crystal molecules when a voltage is applied is determined by the rubbing direction, the rising directions of the liquid crystal molecules in these two regions are different from each other by 180 ° in one pixel. Since the viewing angle characteristics (contrast, color reversal) of these two areas are mutually compensated, the viewing angle of the liquid crystal display device is widened.

However, in this method, the number of rubbing steps is doubled, and a resist coating step, a pre-baking step, an exposure / developing step, a rinsing step, a rubbing alignment treatment step, a cleaning step, a resist stripping step, and a rinsing step are newly added. Since it is necessary, there is a drawback that the process becomes complicated.
In addition, there is a problem that the alignment film subjected to the rubbing alignment treatment is deteriorated by being exposed to a developing solution and a stripping solution in the subsequent developing process and resist stripping process, respectively. There is a problem that the resist is peeled off when this is done.

As another method of changing the rising direction of the liquid crystal molecules in the pixel, by irradiating the area of the pixel of the alignment film with ultraviolet rays to partially change the polarity of the surface of the alignment film, the rising of the liquid crystal molecule is increased. It has also been attempted to change the direction within a pixel (Japanese Patent Laid-Open No. 5-21099). In this method, the molecular chain of polyimide, which is a material of the alignment film, is broken in the portion irradiated with ultraviolet rays, and oxygen atoms are added to the molecular chain to be oxidized. Thereby, the polarity of the surface of the alignment film becomes high and it becomes hydrophilic. Therefore, this portion has improved affinity with the liquid crystal material and the pretilt angle becomes smaller.

A pair of substrates having such an alignment film are
There is disclosed a liquid crystal display device in which a region irradiated with ultraviolet rays (a region having a small pretilt angle) and a region not irradiated with ultraviolet rays (a region having a high pretilt) are arranged so as to face each other, and a liquid crystal material is injected between them. Kaihei 6-281937). In this liquid crystal display device, when a voltage is applied,
The liquid crystal molecules are strongly influenced by a region with a large pretilt angle (a region not irradiated with ultraviolet rays), and the pretilt direction of a region with a small pretilt angle (a region irradiated with ultraviolet rays) is 1
80 degrees up in the opposite direction. That is, the liquid crystal molecules are
It is aligned in the pretilt direction in the region where the pretilt angle is large. As a result, two regions where the rising directions of the liquid crystal molecules are different from each other by 180 ° are formed in one pixel, and the viewing angle characteristics of these two regions are compensated for each other, so that the viewing angle of the liquid crystal display device is widened.

[0011]

However, in this method, the properties of the alignment film (for example, hydrophilicity, polarity, chargeability, dielectric constant, thickness) are different between the area irradiated with ultraviolet rays and the area not irradiated with ultraviolet rays. Therefore, when the liquid crystal display device is driven by an alternating current, electric charges, especially negative charges, are accumulated in the alignment film irradiated with ultraviolet rays, and the absolute value of the voltage is different between the positive electrode side and the negative electrode side. Therefore, the liquid crystal display device has a display defect such as flicker or burn-in.

The present invention has been made in view of the above points, and a liquid crystal display device having a wide viewing angle and free from display defects (flicker, burn-in) due to a change in the film quality of an alignment film, and the liquid crystal display device are provided. It is an object of the present invention to provide a manufacturing method that can be efficiently obtained.

[0013]

In order to achieve the above object, the present invention is designed so that the first and second substrates each having an alignment film on one main surface and the alignment film face each other. A liquid crystal display device comprising a liquid crystal material sandwiched between the arranged first and second substrates, wherein an alignment film of the first substrate is induced in a first region and the first region. The alignment film of the first substrate is divided into a second region that induces a pretilt angle smaller than the pretilt angle of the liquid crystal molecules, and the alignment film of the first substrate is a thermally stable first organic polymer film. It is a laminated film of a second organic polymer film which is formed on the film and is thermally or optically plastic, and the first and second substrates are arranged such that the liquid crystal material has a splay deformation strain. A liquid crystal display device is provided.

In the liquid crystal display device of the present invention, the alignment film of the second substrate induces a pretilt angle smaller than the pretilt angle of the liquid crystal molecules induced in the first region and the first region. And an alignment film of the second substrate is a thermally stable first organic polymer film, and a thermally or optically plastic second film formed on the organic polymer film. Of the organic polymer film, wherein the first region and the second region of the first substrate and the second region and the first region of the second substrate are respectively formed. It is preferable that the first and second substrates are arranged so as to face each other.

Further, the liquid crystal display device of the present invention comprises:
The pretilt angle of the liquid crystal molecules induced in the alignment film of the first substrate is smaller than the pretilt angle induced in the first region of the first substrate, and the second region of the first substrate is Is preferably larger than the pretilt angle.

Further, according to the present invention, the thermally stable first organic polymer film and the thermally or optically plastic second film are formed on the main surface of the substrate.
A step of forming an alignment film by stacking the organic polymer film, and treating the surface of the second organic polymer film by applying heat or light to a selected region on the alignment film. A step, arranging liquid crystal molecules on the alignment film,
A method for manufacturing a liquid crystal display device, wherein the pretilt angle of the liquid crystal molecules in the selected region is made lower than the pretilt angle of the liquid crystal molecules in the non-selected region.

In the method of manufacturing a liquid crystal display device of the present invention, it is preferable that the surface of the second polymer film is subjected to alignment treatment before or after the step of treating the surface of the second organic polymer film.

Further, in the method for manufacturing a liquid crystal display device according to the present invention, in the alignment treatment, a third film is formed on the surface of the second polymer film, and the third film is peeled off from the second film. Preferably.

Further, in the liquid crystal display device of the present invention, in order to determine the tilt-up direction of the liquid crystal molecules for controlling the viewing angle, it is preferable to impart a clockwise or counterclockwise twist property to the liquid crystal material.

In the present invention, the thermally plastic material means
A polymer having a relatively low glass transition point and a thermally stable material means a material having a relatively high polymer glass transition point. As the thermally plastic material and the thermally stable material used in the present invention, materials having a difference in glass transition temperature of 50 to 60 ° C. or more are basically used.

As the materials actually used, the thermally stable materials are polyimide, polyaniline, polypyrrole, etc., and as the thermally plastic materials, polyvinyl alcohol, polyvinyl acetate, polystyrene, polyethylene,
And derivatives in which these side chain groups are substituted are used. As a thermally plastic material, polyvinyl acetal or the like having an especially enhanced adhesive force is effective as a material for increasing the pretilt angle or as a material for improving the alignment uniformity.

In the present invention, the term "optically plastic" is intended to substantially heat-treat the surface of the polymer by an infrared laser or the like, and has the same meaning as a thermally plastic material. At this time, in particular, light (laser) is used as the heating means, and when the unit that constitutes the polymer molecular chain has a site that shows significant thermal motion due to the wavelength component of the laser light, it is possible to efficiently perform heat treatment only on the surface. . That is, since only the thermally plastic film on the surface is selectively heated and does not affect the thermally stable film as the base so much, no electric charge is accumulated in the film and display defects such as flicker and burn-in occur. Does not occur.

Here, a glass substrate, a plastic substrate or the like can be used as the substrate. As the alignment film material, polyimide, benzocyclobutene polymer or the like can be used. As the liquid crystal material, a nematic liquid crystal material such as ZLI-3946 (trade name, manufactured by Merck & Co., Inc.) can be used. In the present invention, the region having a high pretilt angle and the region having a low pretilt angle may be formed within one pixel, or may be formed every one to several pixels.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below.
In the liquid crystal display device of the present invention, the surface of the substrate in contact with the liquid crystal is provided with an alignment film and an alignment treatment for controlling the pretilt angle of the liquid crystal molecules. This alignment film has a laminated structure of a thermally stable organic polymer film and a thermally or optically plastic organic polymer film. When a stimulus is externally applied to the surface of the thermally or optically plastic organic polymer film by heat or light energy, the pretilt angle becomes lower than that when no stimulus is applied.

The present invention utilizes the above-mentioned phenomenon, and a region where the pretilt angle of liquid crystal molecules becomes high and a region where the pretilt angle of the liquid crystal molecule becomes low are selectively applied to the alignment film by heat or light. Form finely. Two substrates are prepared, combined so that a region having a high pretilt angle and a region having a low pretilt face each other, and a liquid crystal material is filled between the substrates. Since the liquid crystal molecules are affected by the side with a high pretilt angle on each substrate and the rising direction is determined,
Since the rising direction is different on the substrate surface, the viewing angle can be widened.

Here, in the method of changing the pretilt angle of liquid crystal molecules by directly and selectively irradiating ultraviolet rays directly onto a thermally stable polyimide film as disclosed in JP-A-6-281937, Since the molecular chains in the film are cut by high energy to change the film quality, problems of display defects such as flicker and image sticking occur.

On the other hand, in the present invention, since the organic polymer film that is thermally or optically plastic is used on the surface of the alignment film,
Since the surface of the thermally or optically plastic organic polymer film can be slightly altered with lower energy, the disorder of the thermally stable film of the underlying layer can be reduced, and the problem of display defects such as flicker and burn-in can be reduced. Does not occur. Further, since there is a thermally stable organic polymer film in the lower layer, the induced pretilt angle is affected by this thermally stable induced polymer film and becomes stable in each state.

In the present invention, as a method of thermally or optically stimulating the alignment film, a treatment of irradiating the alignment film with an infrared laser or IR lamp light (infrared light) can be mentioned. The infrared laser includes a gas laser and a semiconductor laser. In a gas laser, a CO ₂ laser, a CO laser, and an N ₂ O laser having an oscillation wavelength at a wavelength at which an alignment film absorbs infrared light well (oscillation wavelengths are 9 to 11 μm, 5 to 6.5 μm, and 10 to 11 μm, respectively). Is preferred. It is desirable that these gas lasers are transversely pumped atmospheric pressure lasers (TEA lasers) that have a high output.

The semiconductor laser has the advantages of small size, high efficiency, low power consumption, and low price. Al, In, As, Sb, P, G whose oscillation wavelength matches the absorption wavelength of the alignment film
a laser using a compound composed of several elements selected from a, Pb, Se, Te, Sn, Ge and S, such as AlInAsSb laser, InGaAsSb laser, PbSnTe laser, PbSnSe laser,
PbSSe laser, PbSeTe laser, PbGe
Te laser, PbGeSe laser, PbSnSeT
An e laser, a PbSnSSe laser and the like are preferable.

In the present invention, by combining with the clockwise or counterclockwise twist of the liquid crystal material, the liquid crystal molecule alignment becomes more stable. In addition, the liquid crystal display device of the present invention includes a twisted nematic (TN) display device, a super twisted nematic (STN, SBE) display device, a birefringence control (ECB) display device, and the like. It can be used for all display devices in which the viewing angle is affected by the difference in the rising direction. Further, by incorporating an active switching element such as a TFT in each pixel of the liquid crystal display device of the present invention, a better display can be achieved.

In the liquid crystal display device of the present invention, the alignment film of each of the substrates facing each other is divided into a first region and a second region for inducing a pretilt angle smaller than the pretilt angle of the first region. The pair of substrates are arranged so that the region (1) and the second region face each other, and the liquid crystal material is characterized by having a splay deformation strain.

With this structure, the alignment film 1
There are two regions in which a rising direction of liquid crystal molecules is different in each pixel or every one to several pixels. The two regions mutually compensate the viewing angle characteristics. As a result, the liquid crystal display device has a wide viewing angle.

Next, in the liquid crystal display device of the present invention, how the rising direction of liquid crystal molecules changes when a voltage is applied will be described with reference to FIG. 1A and 1B are plan and schematic views of a TN cell in which the liquid crystal molecules 43 are twisted by 90 °. Also, this TN
In the cell, the liquid crystal molecules 13 are stabilized by the twist direction of the chiral agent mixed in the liquid crystal material and the pretilt angle.
The direction of the rubbing alignment treatment applied to the alignment film 12 on the substrate 41 is selected so that the directions twisted by 90 ° are opposite. That is, the orientation treatment direction of the substrate, the arrangement of the substrate, and the twisting direction of the chiral agent were selected so that the liquid crystal molecules 13 had splay deformation strain.

In FIG. 1, the alignment film is a thermally stable organic polymer film 12 and a thermally or optically plastic organic polymer film 1
It has a laminated structure of four. At this time, the shaded area 14-2 of the thermally or optically plastic organic polymer film 14 is an area (second area) in which the surface is treated with heat or light to reduce the pretilt angle of liquid crystal molecules. is there. Therefore, the pretilt angle of the liquid crystal molecules on this region (hatched region) 14-2 is lowered. (Low pretilt angle A).

A region where the pretilt angle is reduced (second region 14-2) and a region where the pretilt angle is not reduced (first region 14-1) are adjacent to each other on the same substrate, and the first substrate and the second substrate are opposed to each other. First area 14-1 and second area 14
-2 are arranged so as to face each other. At this time, both substrates 11 are arranged so that the liquid crystal molecules 13 have splay deformation strain as shown in FIG. When voltage is applied to the TN cell in such a state (halftone display state), the rising direction of the liquid crystal molecules follows the pretilt angle direction of the alignment film (region 14-1) having a higher pretilt angle.

As shown in FIG. 1B, the liquid crystal molecules 43 in the region I are affected by the first region facing the second region.
And the rising direction of the liquid crystal molecules 43 in the region II are opposite. Since the regions I and II are adjacent to each other, the rising directions of the liquid crystal molecules 13 in the adjacent regions in the pixel are opposite (180 ° different) on the same substrate. Therefore, the two regions compensate each other's viewing angle characteristics, and as a result, the viewing angle of the liquid crystal display device is widened.

In order to stably obtain such alignment of the liquid crystal molecules, the low pretilt angle A is 1.5 to 4 ° and the high pretilt angle B is 3.5 to 7 °. The difference in pretilt angle B is preferably 2 to 6 ° (preferably 3 to 4 °).

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. It should be noted that these examples are described for the purpose of facilitating the understanding of the present invention, and can be variously modified and used without departing from the spirit of the present invention. (Embodiment 1) FIG. 2 is an explanatory view showing an embodiment of the liquid crystal display device of the present invention. As shown in FIG. 2, a TFT element 23 was provided as a switching element on a transparent substrate which was a first substrate, and a 200 μm square pixel electrode made of a transparent electrode material such as ITO was provided. The pixel electrode is divided into a matrix by the signal line 21 and the gate line 22. Further, the auxiliary capacitance line 24 is provided in the center of the pixel so as to divide the pixel into two regions. On the other hand, on the transparent substrate which is the second substrate, a transparent electrode was formed on the entire surface, and a color filter and a black matrix were further formed thereon.

On a first and a second substrate, a solution optomer AL (trade name, manufactured by Japan Synthetic Rubber Co., Ltd.) of a soluble polyimide having a structure represented by (Chemical Formula 1) of the following Chemical Formula 1 in the molecule is formed to a thickness of 600. Printing was performed with angstrom, and this was placed in an oven and heated at 180 ° C. for 30 minutes to volatilize the solvent in the solution to form a polyimide film as a thermally stable organic polymer film.

[0040]

Embedded image

A polyvinyl alcohol aqueous solution is applied to the surface of the polyimide film 12 so as to have a thickness of 200 to 300 nm to form a polyvinyl alcohol film, and the water-soluble vinylon film (Kuraray (Kuraray ( Co., Ltd.). After drying at 60 ° C. for 2 hours, the water-soluble vinylon film was peeled off in a certain direction to perform orientation treatment. At this time, a polyvinyl alcohol film 14 is formed on the surface of the polyimide film 12 as an organic polymer film which is thermally or optically plastic. The thickness of the thermally or optically plastic organic polymer film is because the orientation of the molecular layer adsorbed on the thermally stable polyimide film surface needs to be retained up to the surface in contact with the liquid crystal molecules. 10,
About 0 to 200 nm is preferable.

The direction in which the water-soluble vinylon film, which is a film for controlling the alignment, is peeled off (the liquid crystal molecules rise in the direction in which the alignment treatment direction is peeled) is shown in FIG. 2 for the first substrate. The broken line direction was used, and the solid line direction in FIG. 2 was used for the second substrate.

The pretilt angle is reduced to only one-half the area of the pixel on the first substrate, that is, one of the areas surrounded by the signal line 21, the gate line 22 and the auxiliary capacitance line 24 in one pixel. For that purpose, laser annealing was performed as shown in FIG. 3 using a mask provided with a light-transmittable window. That is, heat treatment was performed from above with a laser using a mask 36 for thermal (laser) writing on the alignment film 35 portion of the half region 34 of the pixel electrode 32 made of ITO formed on the glass substrate 31. At this time, the film surface temperature of the mask opening was raised to 80 ° C. or higher. Thus, an alignment film that induces a low pretilt angle can be obtained. The opposing second substrate was similarly subjected to the alignment treatment to form a region inducing a high pretilt angle and a region inducing a low pretilt angle.

After the spacers are scattered on the first substrate that has been subjected to the above treatment and the sealant is applied, a region 14-1 for inducing a high pretilt angle and a region 14-2 for inducing a low pretilt angle are formed. The first substrate and the second substrate were assembled to face each other to form a TN cell with a twist angle of 90 °. A liquid crystal material of Np (left twist), that is, a liquid crystal material in which liquid crystal molecules are twisted 90 ° counterclockwise when the first substrate direction is viewed from the second substrate direction, is injected into this TN cell to form a gap between the electrodes. A liquid crystal display device having a distance of 6 μm was prepared. When observing this liquid crystal display device with a microscope,
It was confirmed that the liquid crystal molecules had splay deformation strain.

At this time, a region 1 that induces a high pretilt angle
The pretilt angle of the liquid crystal molecules of 4-2 was 2 °, and the pretilt angle of the liquid crystal molecules of the region 14-1 inducing the low pretilt angle was 5.5 °.

This liquid crystal display device has two regions I and II in which the rising direction of liquid crystal molecules when a voltage is applied differs by 180 ° in one pixel, and the two regions having different rising directions form a viewing angle with each other. To compensate. Thereby, a liquid crystal display device having a wide viewing angle can be obtained. Actually, the area of contrast 5: 1 was 60 ° in the vertical direction, and a very wide viewing angle was obtained.

Tilt disclination occurs at the boundary between these two areas, but since it exists below the auxiliary capacitance line 54, this tilt disclination line is not visible in the display and is displayed. There were no problems.

Here, as an advantage of the thermal writing, the region subjected to the heat treatment gradually spreads by heat conduction, but its contour becomes ambiguous. That is, the gradient from the region where the heat treatment is sufficient to the region where the heat treatment is not performed is changed. In this ambiguous region, the heat treatment is slightly higher than the pretilt angle indicated by the completely treated region, and the liquid crystal interface between the heat treated region and the non-heat treated region is different from the pretilt angle difference and the arrangement state. The arrangement state is voluntarily determined so that the determined energy is minimized.

Therefore, in the conventional method of modifying the film by the ultraviolet rays, the pretilt angle changes abruptly at the liquid crystal interface in each region, so that a very large disclination line is generated, but in the present invention, a defect is generated at the interface. hard.

Further, this liquid crystal display device showed a good alignment state, and even in the halftone display, a good display without bright / dark reversal depending on the viewing angle could be obtained. Furthermore, since the surface of the alignment film is formed of a polyvinyl alcohol film which is a thin thermally and optically plastic organic polymer film, the irradiation light has an extremely weak output and the surface temperature is about 80 ° C. Therefore, the film quality (polarity, chargeability, dielectric constant, thickness) of the underlying polyimide film (thermally stable) was almost unchanged, and defects such as flicker and image sticking did not occur. (Embodiment 2) FIG. 4 is an explanatory view showing another embodiment of the liquid crystal display device of the present invention. As shown in FIG. 4, the TFT element 2 as a switching element is formed on the transparent substrate which is the first substrate.
3 is provided and is 200 μm formed of a transparent electrode material such as ITO
An m-square pixel electrode was provided. This pixel electrode is divided into a matrix by signal lines 21 and gate lines 22. On the other hand, on the transparent substrate which is the second substrate, a transparent electrode was formed on the entire surface, and a color filter and a black matrix were further formed thereon.

On a first and a second substrate, a solution optomer AL (trade name, manufactured by Japan Synthetic Rubber Co., Ltd.) of a soluble polyimide having a structure represented by (Chemical Formula 1) of Chemical Formula 1 in the molecule is formed to a thickness of 600. Printing was performed with angstrom, the plate was placed in an oven and heated at 180 ° C. for 30 minutes to volatilize the solvent in the solution to form an alignment film made of polyimide as a thermally stable organic polymer film.

An aqueous polyvinyl acetal solution was applied to the surface of the polyimide film 12 to a thickness of 200 to 300 nm to form a polyvinyl acetal film, and a water-soluble vinylon film having a thickness of 30 μm was adhered to the film before the film surface was dried. . After drying at 60 ° C. for 2 hours, the water-soluble vinylon film was peeled off in a certain direction to perform orientation treatment. At this time, a polyvinyl acetal film 14 is formed on the surface of the polyimide film 12 as an organic polymer film that is thermally or optically plastic.

The direction of peeling the water-soluble vinylon film, which is a film for controlling the orientation, is the broken line direction in FIG. 4 for the first substrate, and for the orientation film of the second substrate. Is the direction of the solid line in FIG.

On the first and second substrates, as shown in FIG. 4, a mask provided with a window through which light can be transmitted is used to reduce the pretilt angle so that every other pixel has a checkered pattern. Laser annealing was performed as shown in FIG. That is, heat treatment was performed from above with a laser using a mask 36 for thermal (laser) writing on the alignment film 35 portion of the half region 34 of the pixel electrode 32 made of ITO formed on the glass substrate 31. At this time, the film surface temperature of the mask opening was raised to 80 ° C. or higher. Thus, a region that induces a low pretilt angle was formed. The opposing second substrate was similarly subjected to the alignment treatment, and heat treatment was performed so that the region where a high pretilt angle was induced and the region where a low pretilt angle was induced were formed. Then, orientation relaxation treatment was performed.

After the spacers are scattered on the first substrate which has been subjected to the above treatment and the sealant is applied, a region 14-1 which induces a high pretilt angle and a region 14-2 which induces a low pretilt angle are formed. The first substrate and the second substrate were assembled to face each other to form a TN cell with a twist angle of 90 °. A liquid crystal material of Np (left twist), that is, a liquid crystal material in which liquid crystal molecules are twisted 90 ° counterclockwise when the first substrate direction is viewed from the second substrate direction, is injected into this TN cell to form a gap between the electrodes. A liquid crystal display device having a distance of 6 μm was prepared. When observing this liquid crystal display device with a microscope,
It was confirmed that the liquid crystal molecules had splay deformation strain.

At this time, a region 1 inducing a high pretilt angle
The pretilt angle of the liquid crystal molecules of 4-2 was 2 °, and the pretilt angle of the liquid crystal molecules of the region 14-1 inducing the low pretilt angle was 5.5 °.

In this liquid crystal display device, the rising directions of the liquid crystal molecules when a voltage is applied are different by 180 ° between pixels that are adjacent to each other in the vertical direction and the horizontal direction, and the regions having different rising directions compensate each other for the viewing angle. As a result, a liquid crystal display device having a wide viewing angle is realized. In fact, the area of contrast 5: 1 was 65 ° in the vertical direction, and a liquid crystal display device having a very wide viewing angle was achieved.

Tilt disclination occurs at the boundary between these two areas, but since it exists below the signal line and the gate line, this tilt disclination line is not visible in the display and is not displayed. There was no problem. Further, this liquid crystal display device showed a good alignment state, and even in the halftone display, a good display without bright / dark reversal depending on the viewing angle could be performed.

Furthermore, since the surface of the alignment film is formed of a polyvinyl alcohol film which is a thin thermally and optically plastic organic polymer film, the irradiation light has an extremely weak output and a surface temperature of 80.
It is about ℃. Therefore, the film quality (polarity, chargeability, dielectric constant, thickness) of the underlying polyimide film (thermally stable) was almost unchanged, and defects such as flicker and image sticking did not occur. (Embodiment 3) FIG. 5 is an explanatory view showing another embodiment of the liquid crystal display device of the present invention. As shown in FIG. 5, the TFT element 2 as a switching element is formed on the transparent substrate which is the first substrate.
40 μm formed with a transparent electrode material such as ITO
A corner pixel electrode was provided. This pixel electrode is divided into a matrix by signal lines 21 and gate lines 22. On the other hand, on the transparent substrate which is the second substrate, a transparent electrode was formed on the entire surface, and a color filter and a black matrix were further formed thereon.

On each of the first and second substrates, a solution of thermosetting polyimide, SAN EVER 4140 (polyamic acid type, manufactured by Nissan Kagaku Co., Ltd., trade name) was printed at a thickness of 600 angstroms and placed in an oven. Put 18
It was imidized by heating at 0 ° C. for 30 minutes to form an alignment film made of a polyimide film as a thermally stable organic polymer film having a structure of (Chemical Formula 2) of the following Chemical Formula 2 in the molecule.

[0061]

Embedded image

An aqueous polyvinyl acetal solution was applied to the surface of the polyimide film 12 so as to have a thickness of 200 to 300 nm to form a polyvinyl acetal film, and a water-soluble vinylon film having a thickness of 30 nm was adhered to the film before the film surface was dried. . After drying at 60 ° C. for 2 hours, the water-soluble vinylon film was peeled off in a certain direction to perform orientation treatment. At this time, a polyvinyl acetal film 14 is formed on the surface of the polyimide film 12 as an organic polymer film that is thermally or optically plastic.

The direction of peeling off the water-soluble vinylon film, which is a film for controlling the orientation, is the direction of the broken line in FIG. 5 for the first substrate, and for the orientation film of the second substrate. Is the direction of the solid line in FIG.

On the first and second substrates, a mask provided with a window through which light can be transmitted is used in order to reduce the pretilt angle so that a checkered pattern is formed every two pixels as shown in FIG. Laser annealing was performed as shown in FIG.
That is, heat treatment was performed from above with a laser using a mask 36 for thermal (laser) writing on the alignment film 35 portion of the half region 34 of the pixel electrode 32 made of ITO formed on the glass substrate 31. At this time, the film surface temperature of the mask opening was raised to 80 ° C. or higher. Thus, a region that induces a low pretilt angle was formed. The opposing second substrate was similarly subjected to the alignment treatment, and heat treatment was performed so that the region where a high pretilt angle was induced and the region where a low pretilt angle was induced were formed.

After the spacers are scattered on the first substrate which has been subjected to the above treatment and the sealant is applied, a region 14-1 for inducing a high pretilt angle and a region 14-2 for inducing a low pretilt angle are formed. The first substrate and the second substrate were assembled to face each other to form a TN cell with a twist angle of 90 °. A liquid crystal material of Np (left twist), that is, a liquid crystal material in which liquid crystal molecules are twisted 90 ° counterclockwise when the first substrate direction is viewed from the second substrate direction, is injected into this TN cell to form a gap between the electrodes. A liquid crystal display device having a distance of 6 μm was prepared. When observing this liquid crystal display device with a microscope,
It was confirmed that the liquid crystal molecules had splay deformation strain.

At this time, a region 1 inducing a high pretilt angle
The pretilt angle of the liquid crystal molecules of 4-2 was 3 °, and the pretilt angle of the liquid crystal molecules of the region 14-1 which induces a low pretilt angle was 6 °.

In this liquid crystal display device, the rising directions of the liquid crystal molecules when a voltage is applied are different by 180 ° between the adjacent pixels in the vertical direction and the horizontal direction, and the regions having the different rising directions compensate for the viewing angles. As a result, a liquid crystal display device having a wide viewing angle is realized. In fact, the area of 5: 1 contrast was 55 ° in the vertical direction, and a liquid crystal display device having a very wide viewing angle was achieved.

Tilt disclination occurs at the boundary between these two areas, but since it exists below the signal line and the gate line, this tilt disclination line is not visible in the display and is not displayed. There was no problem. Further, this liquid crystal display device showed a good alignment state, and even in a halftone display, a good display without inversion of brightness and darkness depending on the viewing angle could be performed.

Further, since the surface of the alignment film is formed of a polyvinyl alcohol film which is a thin thermally and optically plastic organic polymer film, the irradiation light has an extremely weak output and a surface temperature of 80.
It is about ℃. Therefore, the film quality (polarity, chargeability, dielectric constant, thickness) of the underlying polyimide film (thermally stable) was almost unchanged, and defects such as flicker and image sticking did not occur. (Embodiment 4) This embodiment will be described with reference to FIGS. In this embodiment, only the first substrate is heat-treated by laser.

First, how the rising direction of the liquid crystal molecules when a voltage is applied is changed by using the method of controlling the pretilt angle of the liquid crystal molecules of the liquid crystal display device of this embodiment will be described with reference to FIG. 6A and 6B are plan and schematic views of a TN cell in which the liquid crystal molecules 13 are twisted by 90 °. Also, this TN
In the cell, the liquid crystal molecules 43 are stably stabilized by the twist direction of the chiral agent mixed in the liquid crystal material and the pretilt angle.
The direction of the rubbing alignment treatment applied to the alignment film 12 on the substrate 11 is selected so that the direction of twisting by 90 ° is opposite. That is, the orientation treatment direction of the substrate, the arrangement of the substrate, and the twisting direction of the chiral agent were selected so that the liquid crystal molecules 13 had splay deformation strain.

In FIG. 7, the shaded region of the alignment film 22 is a region (second region) in which the pretilt angle has been reduced by heat treatment. Therefore, the pretilt angle of the liquid crystal molecules in this area (hatched area) is reduced. (Low pretilt angle A).

The tilt-up direction of the low pretilt angle A of the region (second region) in which the degree of orientation is lowered on the same substrate is adjacent to the region in which the degree of orientation is not lowered (first region, hatched region). The high pre-tilt angle B of the area) coincides with the tilt-up direction.

Next, the high pretilt angle B of the first region and the second
A facing substrate that has been rubbed so as to have a pretilt angle C intermediate to the low pretilt angle A of the region
Assemble the cell. At this time, the liquid crystal molecules 13 on both substrates are shown in FIG.
As shown in FIG. 3, the splay deformation is arranged.

When a voltage is applied to the TN cell in this state (halftone display state), the liquid crystal molecules 13 in the region I are affected by the high pretilt angle B, as shown in FIG. 6B.
The liquid crystal molecules 13 in the region II are affected by the intermediate pretilt angle C, and their rising directions are opposite to each other. Region I
And the region II are adjacent to each other, the rising directions of the liquid crystal molecules 13 in the adjacent regions in the pixel are opposite (180 ° different) on the same substrate. Therefore, the two regions compensate each other's viewing angle characteristics, and as a result, the viewing angle of the liquid crystal display device is widened.

Next, a method of manufacturing the liquid crystal display device of this embodiment will be described. First, a TFT element 23 was provided as a switching element on a transparent substrate which was a first substrate, and a 100 μm square pixel electrode formed of a transparent electrode material such as ITO was provided.
This pixel electrode is divided into a matrix by signal lines 21 and gate lines 22. Further, the auxiliary capacitance line 24 is provided in the center of the pixel so as to divide the pixel into two regions.
On the other hand, on the transparent substrate which is the second substrate, a transparent electrode was formed on the entire surface, and a color filter and a black matrix were further formed thereon.

The above chemical formula 1 is formed on the first substrate (TFT element side).
A solution of a soluble polyimide having a structure represented by (Chemical formula 1) in the molecule, Optomer AL (trade name, manufactured by Japan Synthetic Rubber Co., Ltd.) is printed at a thickness of 600 angstrom, and is placed in an oven at 180 ° C. The solvent in the solution was volatilized by heating for 30 minutes to form an alignment film made of a polyimide film as a thermally stable organic polymer film.

An aqueous polyvinyl acetal solution was applied to the surface of the polyimide film 12 so as to have a thickness of 200 to 300 nm to form a polyvinyl acetal film, and a water-soluble vinylon film having a thickness of 30 nm was adhered to the film before the film surface was dried. . After drying at 60 ° C. for 2 hours, the water-soluble vinylon film was peeled off in a certain direction to perform orientation treatment. At this time, a polyvinyl acetal film 14 is formed on the surface of the polyimide film 12 as an organic polymer film that is thermally or optically plastic.

The water-soluble vinylon film, which is a film for controlling the orientation, was peeled off in the direction of the broken line in FIG. 7 with respect to the first substrate. Next, a solution optomer A of a soluble polyimide having the structure represented by (Chemical Formula 1) of Chemical Formula 1 in the molecule on the second substrate (color filter side)
L (manufactured by Japan Synthetic Rubber Co., Ltd., trade name) is printed with a thickness of 600 angstrom, and this is placed in an oven for 180
The solvent in the solution was volatilized by heating at 30 ° C. for 30 minutes to form an alignment film made of polyimide as a thermally stable organic polymer film.

An aqueous polyvinyl acetal solution was applied to the surface of this polyimide film 12 so as to have a thickness of 200 to 300 nm to form a polyvinyl acetal film, and a water-soluble vinylon film having a thickness of 30 nm was adhered to the film before the film surface was dried. . After drying at 60 ° C. for 2 hours, the water-soluble vinylon film was peeled off in a certain direction to perform orientation treatment. At this time, a polyvinyl acetal film 14 is formed on the surface of the polyimide film 12 as an organic polymer film that is thermally or optically plastic.

The direction of peeling off the water-soluble vinylon film, which is a film for controlling the orientation, was set to the solid line direction in FIG. 5 with respect to the orientation film of the second substrate. At this time, the alignment treatment conditions were selected so that the pretilt angle of the second substrate was smaller than the pretilt angle of the first substrate.

Next, as shown in FIG. 7, on the alignment film of the first substrate, a half region of the pixel, that is, a region surrounded by the signal line, the gate line and the auxiliary capacitance line in one pixel is formed. In order to reduce the pretilt angle on only one side, a mask provided with a window through which light can be transmitted was used, and laser annealing was performed as shown in FIG. That is, a half region 34 of the pixel electrode 32 made of ITO formed on the glass substrate 31.
Mask 3 for writing heat (laser) on the alignment film 35 portion of
6 was used to perform heat treatment from above with a laser. At this time, the film surface temperature of the mask opening was raised to 80 ° C. or higher.
Thus, a region that induces a low pretilt angle was formed. At this time, the low pretilt angle was set to be sufficiently smaller than the pretilt angle of the second substrate facing the second pretilt angle.

At this time, the pretilt angle of the heat-treated region was 1.5 °. In addition, the pretilt angle of the unheated region was 6 °. The pretilt angle of the liquid crystal molecules on the second substrate was 3.5.

Spacers were scattered on the first substrate which had been subjected to the above-mentioned treatment, and after applying a sealant, the first substrate and the second substrate were opposed to each other to form a TN cell having a twist angle of 90 °. . A liquid crystal material of Np (left twist) was injected into this TN cell to prepare a liquid crystal display device having a distance between electrodes of 6 μm.

This liquid crystal display device has two regions in which the rising direction of liquid crystal molecules when a voltage is applied differs by 180 ° in one pixel, and these two regions having different rising directions compensate each other for the viewing angle. As a result, a liquid crystal display device having a wide viewing angle is realized. In fact, the area of 5: 1 contrast was 60 ° in the vertical direction, and a liquid crystal display device having a very wide viewing angle was achieved.

Tilt disclination occurs at the boundary between these two areas, but since it exists below the auxiliary capacitance line 24, this tilt disclination line is not visible in the display, and is displayed. There were no problems. Further, this liquid crystal display device showed a good alignment state, and even in the halftone display, a good display without bright / dark reversal depending on the viewing angle could be performed. Furthermore, since the surface of the alignment film is formed of a polyvinyl alcohol film, which is a thin thermally and optically plastic organic polymer, the irradiation light has an extremely weak output and the surface temperature is about 80 °. Therefore, the film quality (polarity, chargeability, dielectric constant, thickness) of the underlying polyimide film (thermally stable)
Since there was almost no change, defects such as flicker and burn-in did not occur.

As in this example, a low pretilt angle region (a region having a low degree of alignment) and a high pretilt angle region (a region having a high degree of alignment) are formed in the alignment film of one substrate, and the alignment film of the other substrate is formed. Is set to a pretilt angle (a region having an intermediate degree of orientation) intermediate between the low pretilt angle and the high pretilt angle, and the two substrates are opposed to each other to form a region in which the rising directions of the liquid crystal molecules are different. can do.

[0087]

As described above, in the liquid crystal display device of the present invention, the alignment film on the substrate has a pretilt angle smaller than the pretilt angle of the first region and the first region within one pixel or every one to several pixels. A pair of substrates are arranged so as to be divided into a second region having a corner, and the first region and the second region face each other. Since the liquid crystal material has a splay deformation strain, one pixel or Two regions having different rising directions of liquid crystal molecules on the alignment film are formed every few pixels.
The two regions can mutually compensate each other's viewing angle characteristics to widen the viewing angle.

At this time, since the present invention uses the laminated film of the thermally stable organic polymer film and the thermally or optically plastic organic polymer film formed on the surface as the alignment film, the pretilt It is possible to perform heat treatment that lowers the temperature at a low temperature, and the substantial film quality (polarity, chargeability, dielectric constant, thickness)
It is possible to prevent the change of. Therefore, it is possible to obtain a liquid crystal display device having a wide viewing angle without flicker or image sticking.

[Brief description of drawings]

FIG. 1A is an explanatory diagram showing a liquid crystal display device of the present invention in a state where no voltage is applied, and FIG. 1B is an explanatory diagram showing a liquid crystal display device of the present invention in a voltage application state (halftone display state).

FIG. 2 is an explanatory diagram showing an embodiment of a liquid crystal display device of the present invention.

FIG. 3 is a sectional view of a substrate for explaining heat treatment in the liquid crystal display device of the present invention.

FIG. 4 is an explanatory diagram showing an embodiment of a liquid crystal display device of the present invention.

FIG. 5 is an explanatory diagram showing an embodiment of a liquid crystal display device of the present invention.

FIG. 6A is an explanatory diagram showing the liquid crystal display device of the present invention in a state where no voltage is applied, and FIG. 6B is an explanatory diagram showing the liquid crystal display device of the present invention in a voltage application state (halftone display state).

FIG. 7 is an explanatory diagram showing an embodiment of a liquid crystal display device of the present invention.

[Explanation of symbols]

 11 ・ ・ ・ Substrate 12 ・ ・ ・ Thermally stable organic polymer film 13 ・ ・ ・ Liquid crystal molecule 14 ・ ・ ・ Thermally or optically plastic organic polymer film 15 ・ ・ ・ High tilt region 21 ・ ・・ Signal line 22 ・ ・ ・ Gate line 23 ・ ・ ・ Switching element 24 ・ ・ ・ Auxiliary capacitance line 31 ・ ・ ・ Glass substrate 32 ・ ・ ・ Pixel electrode 33 ・ ・ ・ Alignment film 34 ・ ・ ・ Heat treatment region 35 ・ ・ ・Mask 36 ・ ・ ・ Laser

Claims (6)

[Claims] 1. A first substrate and a second substrate each having an alignment film on one main surface, and the first and second substrates arranged so that the alignment films face each other. A liquid crystal display device comprising a liquid crystal material, wherein the alignment film of the first substrate induces a pretilt angle smaller than a pretilt angle of liquid crystal molecules induced in the first region and the first region. And an alignment film of the first substrate is a thermally stable first organic polymer film, and a thermally or optically plastic second film formed on the organic polymer film. 2. A liquid crystal display device, wherein the first and second substrates are arranged so that the liquid crystal material has a splay deformation strain. 2. The alignment film of the second substrate is divided into a first region and a second region that induces a pretilt angle smaller than a pretilt angle of liquid crystal molecules induced in the first region, Further, the alignment film of the second substrate is composed of a thermally stable first organic polymer film and a thermally or optically plastic second organic polymer film formed on the organic polymer film. A laminated film, wherein the first region and the second region of the first substrate and the second region and the first region of the second substrate face each other. The liquid crystal display device according to claim 1, wherein the first and second substrates are arranged. 3. The pretilt angle of liquid crystal molecules induced in the alignment film of the second substrate is the first tilt of the first substrate.
2. The liquid crystal display device according to claim 1, wherein the pretilt angle is smaller than the pretilt angle induced in the region of 1 and is larger than the pretilt angle of the second region of the first substrate. 4. An alignment film is formed by stacking a thermally stable first organic polymer film and a thermally or optically plastic second organic polymer film on the main surface of a substrate. A step of treating the surface of the second organic polymer film by applying heat or light to a selected region on the alignment film, arranging liquid crystal molecules on the alignment film, A method of manufacturing a liquid crystal display device, wherein a pretilt angle of liquid crystal molecules in a selected region is made lower than a pretilt angle of liquid crystal molecules in a non-selected region. 5. The manufacturing of a liquid crystal display device according to claim 4, wherein the surface of the second polymer film is subjected to alignment treatment before or after the step of treating the surface of the second organic polymer film. Method. 6. The alignment process according to claim 5, wherein a third film is formed on the surface of the second polymer film, and the third film is peeled off from the second film. Liquid crystal display device.