JPH10170920A - Liquid crystal display element and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element that has good orientability and a wide visual field angle, and a process for producing the same. SOLUTION: Liquid crystal is held between a pair of substrates 8a and 8b and active elements 4 are arranged for every pixel on one of these substrates. A pair or more of wire-shaped pixel electrodes 7 and common electrodes 6 are formed on the substrates 8a, 8b within the pixels in such a manner that at least the pixel electrodes 7 are arranged on the substrate 8a having these active elements 4. The substrate surfaces are provided with such voltage impressing means that generate electric fields in the horizontal direction to the substrate surface when voltage is applied between the electrodes 6, 7. The surface of the one substrate 8b has controlled liquid crystal orientability. The surface of the other substrate 8a having the large difference in level by the electrodes has the nature to annihilate the liquid crystal orienting power at the temp. lower than the nematic-isotropic transition point of the liquid crystals. The orientation state of the liquid crystal molecules spreads from the one substrate 8b side having the orientability by an annealing treatment. The orientation homogeneous even near to the stepped parts is obtd. at the other substrate 8a as well having the differences in level of wirings.

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 crystal display device having a wide viewing angle and a method for manufacturing the same.

[0002]

2. Description of the Related Art Liquid crystal display devices are thin, lightweight, and low power consumption display devices, and are widely used in image display devices such as televisions and videos and OA equipment such as word processors and personal computers. Among the liquid crystal display elements, most of the active matrix type liquid crystal display elements in which a number of switching elements are arranged on an array substrate use a twisted nematic (TN) mode in which the orientation direction of the liquid crystal is twisted almost 90. It is being developed as a display capable of high-speed response and high definition.

[0003] However, the TN mode liquid crystal display element has a major drawback that the color tone and contrast differ depending on the angle at which the panel is viewed, since the display is performed using the optical rotation of the liquid crystal. In order to solve these drawbacks, a compensation method using a retardation film, a pixel division method having a plurality of different orientation regions in a pixel, an orientation division method, and the like are used. However, in the TN mode, the viewing angle range in which good display is still obtained is narrower than that of a cathode ray tube (CRT), and display performance equal to or higher than that of a CRT has not been realized.

In order to achieve a viewing angle characteristic closer to that of a CRT, there is a display system in which liquid crystal molecules are moved in a direction substantially horizontal to the substrate surface, and light transmittance is controlled by an electric field control birefringence effect. For example, a method of forming a comb electrode on a substrate has been proposed by RASoref (J. Appl. Phys. 45,
5446 (1974)). According to this method, the liquid crystal molecules are always viewed almost from the side (shorter axis direction), and there is almost no difference in the refractive index even when the viewing direction is different, so that the viewing angle dependency of the contrast can be extremely reduced. Becomes

[0005]

However, according to the above-described method of moving the liquid crystal molecules substantially horizontally on the substrate surface, the pixel electrode and the common electrode, which were transparent electrodes in the conventional TN mode, exist in a linear shape. The parts are increased, and those electrodes are present in the pixel. Therefore, in the conventional rubbing method using a cloth, there is a problem that rubbing is difficult to be performed in a portion shadowed by the step portion, and alignment failure is likely to occur.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid crystal display device having good orientation and a wide viewing angle, and a method of manufacturing the same, in view of such conventional problems.

[0007]

According to a first aspect of the present invention, there is provided a liquid crystal display device wherein a liquid crystal is sandwiched between a pair of substrates, an active element is arranged for each pixel on one of the substrates, and the active element is provided on the substrate. A pair of or more linear pixel electrodes and a common electrode are formed on a substrate in a pixel so that at least the pixel electrode is disposed thereon, and when a voltage is applied between the electrodes, the pixel electrode extends in a horizontal direction with respect to the substrate surface. A liquid crystal display element provided with voltage applying means for generating an electric field, wherein the surface of one substrate has a controlled liquid crystal orientation, and the surface of the other substrate having a large step due to the electrode has a nematic liquid crystal. It is characterized in that it has the property that the liquid crystal alignment force disappears at a temperature lower than the isotropic transition point.

As described above, when a voltage is applied between the electrodes, an electric field is generated in the horizontal direction with respect to the substrate surface, and the liquid crystal molecules are moved in the horizontal direction with respect to the substrate. Even when there is a step, one of the substrates has a controlled liquid crystal alignment property, and the other substrate has a property of losing the liquid crystal alignment force below the NI point (nematic-isotropic transition point). Due to the annealing treatment, the alignment state of the liquid crystal molecules spreads from one of the substrates having alignment properties, and even on the other substrate having a wiring step, uniform homogeneous alignment can be obtained up to the vicinity of the step, high contrast,
The viewing angle becomes wider.

The liquid crystal display device according to the second aspect is the first aspect.
In the above, a film of a thermoplastic polymer having a glass transition temperature equal to or lower than the nematic-isotropic transition point of the liquid crystal was formed on the other substrate surface. As described above, since a film of a thermoplastic polymer having a Tg (glass transition temperature) equal to or lower than the nematic-isotropic transition point of the liquid crystal is formed on the surface of the other substrate, as a material that loses the liquid crystal alignment force below the NI point. Especially effective. That is, the thermoplastic polymer is Tg
At the above temperature, the liquid crystal alignment force disappears due to the rubber elastic state due to the micro-Brownian motion of the molecular chain. Therefore, by setting the Tg to be equal to or lower than the NI point at which the liquid crystal molecules start to be aligned, the alignment force of the thermoplastic polymer is reduced. Orient in the state where it disappeared.

The liquid crystal display device according to the third aspect is the second aspect.
, The glass transition temperature of the thermoplastic polymer is 50 ° C.
That's it. As described above, since the glass transition temperature of the thermoplastic polymer is 50 ° C. or higher, the panel temperature is higher than 40 ° C. in an environment where the liquid crystal display element is normally used, and the alignment stability is good. According to a fourth aspect of the present invention, in the liquid crystal display element according to the second aspect, the thermoplastic polymer is a polyurethane film having a shape memory effect. As described above, since the thermoplastic polymer is a polyurethane film having a shape memory effect, it is maintained in a very good state at a temperature of Tg or less. That is, polyurethane having a shape memory effect is
Because it is composed of a soft segment and a hard segment, it is partially crystallized, so when it is used as an alignment film,
Since the liquid crystal does not dissolve or swell, and the voltage holding ratio does not decrease, the reliability is high.

The liquid crystal display device according to the fifth aspect is the first aspect.
, Polyimide was formed on the surface of the substrate having a controlled liquid crystal orientation. As described above, since polyimide is formed on the surface of the substrate having controlled liquid crystal orientation, the alignment regulating force on the substrate surface is increased, and the orientation is spread to the opposite substrate. The liquid crystal display device according to the sixth aspect is the first aspect.
In the above, the other substrate is not subjected to the alignment treatment. As described above, since the other substrate has not been subjected to the orientation treatment, the homogeneous orientation state is spread from the interface of the opposite substrate that has been subjected to the orientation treatment by the annealing treatment, and uniform orientation can be obtained. In addition, since it is only necessary to perform the alignment treatment on one of the substrates, the number of steps can be reduced, leading to a cost reduction.

According to a seventh aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, wherein one substrate has a surface having a controlled liquid crystal orientation, and the other substrate has a surface having a liquid crystal nematic-isotropic transition point. After forming to have the property of losing the liquid crystal alignment force at a low temperature, in the process of cooling the liquid crystal panel in which the liquid crystal is sealed between a pair of substrates after raising the temperature above the nematic-isotropic transition point of the liquid crystal, It is characterized in that cooling is performed while controlling the temperature of one substrate having a controlled liquid crystal orientation to be equal to or lower than the temperature of the other substrate.

As described above, by cooling while controlling the temperature of one substrate having a liquid crystal alignment property whose surface is controlled to be equal to or lower than the temperature of the other substrate, the surface of one substrate can be cooled from the interface of one substrate. Since the nematic phase begins to appear and its orientation spreads toward the interface of the opposite substrate, uniform orientation can be obtained even if the opposite substrate does not have orientation.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device according to a first embodiment of the present invention will be described with reference to FIGS. FIG.
FIG. 1 is a plan view of a liquid crystal display device according to a first embodiment of the present invention, and FIG. 2 is a sectional view thereof. A pair of glass substrates 8a,
A liquid crystal (not shown) is sandwiched between 8b, and a gate 1, a source electrode 2, and a drain electrode 3 are formed on a substrate 8a, and a thin film transistor element (active element) 4 is arranged for each pixel. Also, at least a pair of linear pixel electrodes 7 and a common electrode 6 short-circuited by the extraction electrode 5 are formed on the substrate 8a in the pixel, and when a voltage is applied between the electrodes 6 and 7, Voltage applying means for generating an electric field in the horizontal direction with respect to the surface of the substrate 8a is provided. The pixel electrode 7
Drain electrode 3 parallel to common electrode 6 and separated by 15 μm
Is connected to Further, a polystyrene alignment film 9a is formed on the substrate 8a, and a polyimide alignment film 9b is formed on the substrate 8b.

That is, a polystyrene solution having a solid content of 4% by weight was offset-printed on the glass substrate 8a on which the electrodes were formed as described above, and heated at 170 ° C. for 1 hour to form a polystyrene alignment film 9a. At this time, the thickness of the oriented polystyrene film 9a was about 800 °. The Tg (glass transition temperature) of this polystyrene alignment film 9a is 98
° C. Using a rayon cloth, the substrate 8a was subjected to a rubbing process in a direction 10 at an angle of about 5 ° with a direction parallel to the electrode wiring.

On the other transparent glass substrate 8b, a polyimide varnish having a solid content of 6% by weight (for example, Optmer AL-1054: manufactured by Nippon Synthetic Rubber Co., Ltd.) is offset-printed and heated at 170 ° C. for 1 hour. A polyimide alignment film 9b was formed. At this time, the thickness of the polyimide alignment film 9b was about 800 °. The rubbing treatment was performed in such a direction that a homogeneous orientation was obtained when the substrate 8b was bonded to the substrate 8a having electrodes.

The substrates 8a and 8b are opposed to each other so that the polystyrene alignment film 9a and the polyimide alignment film 9b face each other, and glass beads 11 having a diameter of 4 μm are used as spacers.
And pasted together. A nematic liquid crystal having a refractive index anisotropy Δn of 0.075 and an NI point (nematic-isotropic transition point) of 105 ° C. was sealed in the panel by a vacuum injection method. This panel is heated to a temperature higher than the NI point.
Annealing was performed at 1 ° C. for 1 hour. As a result, uniform homogeneous alignment was obtained over the entire surface of the liquid crystal panel. As a result of observing the orientation state of this panel under a polarizing microscope, the vicinity of the wiring was almost uniformly oriented, and almost no light leakage in a normally black state was observed.

A polarizing plate is attached to both sides of the liquid crystal panel manufactured as described above so as to be in a crossed Nicols state, and a normally black mode liquid crystal display device is obtained. At this time, the polarizing plate was attached such that the rubbing direction 10 on the glass substrate 8a side was parallel to the absorption axis of the polarizing plate. As a result of measuring the voltage-transmittance characteristics of this liquid crystal display element, a good result was obtained with a maximum contrast ratio of 200.

For comparison, the same polyimide alignment film as that of 8b was formed on the glass substrate 8a, and a rubbing treatment was performed.
Otherwise, a liquid crystal panel having the same configuration as above was manufactured. As a result of observing the alignment state of the liquid crystal panel under a polarizing microscope, there was a non-alignment region near the wiring, and light leakage was observed in a normally black state. A polarizing plate was attached to both sides of the liquid crystal panel in the same manner as described above so as to be in a crossed Nicols state, thereby obtaining a normally black mode liquid crystal display element. The maximum contrast of this liquid crystal display device was 150.

The reason why the above measurement results are obtained will be described. When rubbing a substrate having a large step with an electrode or the like, fibers of the rubbing cloth do not touch near the step depending on the rubbing direction, and there is a portion where the rubbing treatment is not performed. As a result, the vicinity of the step becomes a non-aligned region, and light leakage easily occurs. On the other hand, on a substrate having almost no step, a uniform rubbing treatment is performed on almost the entire surface. In the case of a combination of a substrate that has undergone uniform rubbing on the entire surface and a substrate that has a portion that has not been subjected to rubbing, when the orientation spreads from the substrate interface by annealing after liquid crystal sealing, uniform alignment is performed on the entire surface. Unidirectionally spreading from the side of the substrate where the separation is performed leads to uniform orientation.

In the TN mode, the liquid crystal molecules are oriented by being twisted by 90 ° between the upper and lower substrates. Therefore, it is necessary that both the substrate surfaces have controlled orientation in each direction. In a display mode in which liquid crystal molecules are moved in a direction substantially horizontal to the substrate surface and light transmittance is controlled by an electric field control birefringence effect, homogeneous alignment is used. In the case of homogeneous alignment, if one substrate surface has a controlled liquid crystal alignment in a certain direction and the other substrate has lost the alignment force at a temperature equal to or lower than the NI point, after the annealing treatment, The alignment spreads from the side of the substrate having liquid crystal alignment, and uniform alignment is obtained.

Therefore, when a rubbing process is performed on a substrate as a method for imparting orientation to the substrate surface, it is preferable that the substrate side having a large step loses the alignment force below the NI point. As a material that loses the alignment force at a temperature equal to or lower than the NI point, a thermoplastic polymer having a Tg equal to or lower than the NI point is particularly effective. In this embodiment, an oriented polystyrene film 9a having a Tg of 98 ° C. and a nematic liquid crystal having an NI point of 105 ° C. are used as the thermoplastic polymer.

That is, at a temperature higher than Tg, the thermoplastic polymer is in a rubber elastic state due to the micro Brownian motion of the molecular chain, but at a temperature lower than Tg, it is in a plastic state with the frozen Micro Brownian motion. Therefore, the orientation force on the surface of the polystyrene orientation film 9a obtained by the rubbing treatment disappears when the temperature becomes equal to or higher than Tg and enters a rubber elastic state, and does not return even when the temperature falls below Tg. When the NI point of the liquid crystal is higher than the Tg of the thermoplastic polymer, the liquid crystal is in a rubber elastic state during the annealing treatment for making the alignment uniform. The polymer surface is in a state where the alignment force has disappeared. As a result, the orientation spreads from the side of the substrate 8b having the orientation force, and uniform homogeneous orientation is obtained over the entire panel.

In this embodiment, a polystyrene oriented film is used as the thermoplastic polymer, but polyester such as polymethyl methacrylate or polyvinyl chloride may be used, and the thermoplastic polymer having a Tg lower than the NI point of the liquid crystal. Then, the same effect can be obtained. Further, the Tg of the thermoplastic polymer used for the liquid crystal display element is, considering that the panel temperature in an environment where the liquid crystal display element is usually used is about 40 ° C. due to the influence of the backlight and the like and the alignment stability and the like. A minimum of 50 ° C is required. In consideration of reliability, 80 ° C. or higher is preferable.

Further, in this embodiment, the polyimide alignment film 9b obtained by rubbing the substrate 8b having liquid crystal alignment is used. And so on. However, at the time of cooling after the annealing process, one side of the substrate 8b
Considering that the orientation spreads from
Since the stronger the alignment regulating force on the surface of b, the better, the polyimide alignment film 9b is preferably used in this regard.

The common electrode 6 and the pixel electrode 7 are both formed on the substrate 8a.
An electric field may be generated in the horizontal direction with respect to the substrate surface by forming it in b. In this case, the surface of the substrate having the active element having more step portions loses the liquid crystal alignment force at a temperature lower than the NI point of the liquid crystal as described above.

A liquid crystal display device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a sectional view of the liquid crystal display device according to the embodiment of the present invention. On a glass substrate on which an electrode is formed in the same configuration as in the first embodiment,
A polyurethane solution having a solid content of 6% by weight (for example, WF009 manufactured by Mitsubishi Heavy Industries, Ltd.) is offset-printed, and
By heating at 50 ° C. for 1 hour, a polyurethane alignment film 12 was formed. At this time, the thickness of the polyurethane alignment film 12 is about 8
It was 00 $. This polyurethane alignment film 12 has a shape memory effect, and its Tg is 93 ° C. This substrate 8a
Using a rayon cloth, a rubbing treatment was performed in a direction 10 at an angle of about 5 ° with a direction parallel to the electrode wiring.

On the other transparent glass substrate 8b, a polyimide varnish having a solid content of 6% by weight (for example, Optmer AL-5417: manufactured by Nippon Synthetic Rubber Co., Ltd.) is offset-printed and heated at 170 ° C. for 1 hour. A polyimide alignment film 9b was formed. At this time, the thickness of the polyimide alignment film 9b was about 800 °. The rubbing treatment is performed in such a direction that a homogeneous alignment is obtained when the substrate 8b is bonded to the substrate 8a having electrodes.
2 and polyimide alignment film 9b so that substrate 8a
And bonded together via a glass bead 11 having a diameter of 4 μm as a spacer. This panel has a refractive index anisotropy Δ
A nematic liquid crystal having an n of 0.075 and an NI point of 100 ° C. was sealed by a vacuum injection method. This panel was annealed at 120 ° C. higher than the NI point for 1 hour. As a result, uniform homogeneous alignment was obtained over the entire surface of the liquid crystal panel. As a result of observing the orientation state of this panel under a polarizing microscope, the vicinity of the wiring was almost uniformly oriented, and almost no light leakage in a normally black state was observed. Polarizing plates were attached to both sides of the liquid crystal panel manufactured as described above so as to be in a crossed Nicols state, and a normally black mode liquid crystal display element was obtained. At this time, the polarizing plate was attached such that the rubbing direction 10 on the glass substrate 8a side was parallel to the absorption axis of the polarizing plate. As a result of measuring the voltage-transmittance characteristics of this liquid crystal display element, a good result was obtained with a maximum contrast ratio of 220. Also, as a result of measuring the response speed of this liquid crystal display element, the response time at the rise was 6 times.
The response time at the falling edge was 0 msec and the falling response time was 55 msec, which was exactly the same as the measurement result of the liquid crystal display element of the comparative example. Therefore, the surface of the polyurethane alignment film 12 is maintained in a very good state at a temperature equal to or lower than Tg.

An example of a structural formula proposed in JP-A-2-116102 as a polyurethane having a shape memory effect is shown in the following formula (Formula 1).

[0030]

Embedded image Polyurethane having a shape memory effect is partially crystallized because it comprises a soft segment and a hard segment.
Therefore, when used as an alignment film, there is no dissolution or swelling in the liquid crystal, and there is no decrease in the voltage holding ratio.
It is a very good material in view of this reliability. Therefore, the reliability of the liquid crystal display device using the polyurethane alignment film having this shape memory effect is also improved.

A liquid crystal display device according to a third embodiment of the present invention will be described. A liquid crystal panel having the same configuration as that of the second embodiment was manufactured without subjecting the polyurethane alignment film 12 to rubbing treatment. When this panel was sandwiched between polarizing plates and the alignment state immediately after liquid crystal injection was observed, flow alignment was observed along the flow at the time of liquid crystal injection. This liquid crystal panel was annealed for 1 hour at 120 ° C. higher than the NI point. As a result, uniform homogeneous alignment was obtained over the entire surface of the liquid crystal panel. As a result of observing the orientation state of this panel under a polarizing microscope, the vicinity of the wiring was almost uniformly oriented, and almost no light leakage in a normally black state was observed. Polarizing plates were attached to both sides of the liquid crystal panel manufactured as described above so as to be in a crossed Nicols state, and a normally black mode liquid crystal display element was obtained. As a result of measuring the voltage-transmittance characteristics of this liquid crystal display element, a good result was obtained with a maximum contrast ratio of 200.

When a film of a thermoplastic polymer having a Tg lower than the NI point of the liquid crystal is used as an alignment film, even if the surface of the film of the thermoplastic polymer is stretched by a rubbing treatment and has a liquid crystal aligning force, the Tg is obtained. Since the surface state up to that point disappears at that point, even if rubbing treatment is not performed, a homogeneous alignment state is obtained since the homogeneous alignment state is spread from the opposite substrate interface by annealing. Therefore, since only one of the substrates needs to be subjected to the alignment treatment, the number of steps can be reduced and the cost can be reduced. In addition, problems such as poor alignment related to the rubbing treatment can be reduced.

A method for manufacturing a liquid crystal display device according to a fourth embodiment of the present invention will be described. A liquid crystal panel having the same configuration as that of the second embodiment is manufactured, and the liquid crystal panel is placed in a bat with a stainless steel lid with the substrate 8a on which the polyurethane alignment film 12 is formed facing upward, and placed in a thermostat at 120 ° C. For 1 hour. Thereafter, at the time of cooling from 120 ° C. to room temperature, the liquid crystal panel was taken out while being kept in the bat with a stainless steel lid, and placed on a stainless block. At this time, the cooling rate of the upper substrate 8a was −8 ° C./min. At this time, the cooling rate of the substrate 8b on which the polyimide alignment film 9b was formed was faster than that of the substrate 8a on which the polyurethane alignment film 12 was formed. As a result, uniform homogeneous alignment was obtained over the entire liquid crystal panel. As a result of observing the orientation state of this panel under a polarizing microscope, the vicinity of the wiring was uniformly oriented, and no light leakage was observed in a normally black state. A polarizing plate is attached on both sides of the liquid crystal panel manufactured as described above so as to be in a cross Nicol state,
A normally black mode liquid crystal display device was obtained. As a result of measuring the voltage-transmittance characteristics of this liquid crystal display element, a good result was obtained with a maximum contrast ratio of 230.

By cooling from the oriented substrate 8b at the time of cooling from a temperature higher than the NI point, a nematic phase starts to appear at the substrate interface, and the nematic phase starts to move toward the opposite substrate interface. Since the orientation spreads, a uniform orientation can be obtained even if one substrate 8a does not have the orientation. In order to spread the orientation state from the substrate 8b on one side, the larger the temperature difference between the two substrates 8a and 8b, the better. For that purpose, it is effective to rapidly cool the substrate 8b on one side.

In this embodiment, the temperature of the oriented substrate 8b is controlled to be lower than the temperature of the opposite substrate 8a. However, even if both substrates 8a and 8b have the same cooling rate, Uniform orientation is obtained.

[0036]

According to the liquid crystal display device of the present invention, when a voltage is applied between the electrodes, an electric field is generated in the horizontal direction with respect to the substrate surface, so that the liquid crystal molecules are moved in the horizontal direction with respect to the substrate. In the moving mode, even if there is a wiring step in the pixel, one substrate has a controlled liquid crystal alignment, and the other substrate has a liquid crystal alignment force below the NI point (nematic-isotropic transition point). By having the property of disappearing,
Due to the annealing treatment, the alignment state of the liquid crystal molecules spreads from one of the substrates having alignment properties, and even on the other substrate having a wiring step, a uniform homogeneous alignment can be obtained up to the vicinity of the step, the liquid crystal having a high contrast and a wide viewing angle. A display element can be provided.

According to the second aspect, a film of a thermoplastic polymer having a Tg (glass transition temperature) lower than the nematic-isotropic transition point of the liquid crystal is formed on the other substrate surface.
It is particularly effective as a material that loses the liquid crystal alignment force below the NI point. That is, at a temperature higher than Tg, the thermoplastic polymer is in a rubber elastic state due to the micro-Brownian motion of the molecular chain, and the liquid crystal alignment force disappears. Therefore, by setting Tg to be equal to or lower than the NI point at which liquid crystal molecules start to be aligned. The thermoplastic polymer is oriented in a state where the orientation force has disappeared.

In the third aspect, the glass transition temperature of the thermoplastic polymer is 50 ° C. or higher, so that the panel temperature is higher than 40 ° C. in an environment where the liquid crystal display element is usually used, and the alignment stability is good. In claim 4, since the thermoplastic polymer is a polyurethane film having a shape memory effect,
It is kept in very good condition at temperatures below Tg. In other words, polyurethane having a shape memory effect is partially crystallized because it is composed of a soft segment and a hard segment, and therefore, when used as an alignment film, does not dissolve or swell in liquid crystal, and also decreases the voltage holding ratio. Not so, high reliability.

According to the fifth aspect, since polyimide is formed on the surface of the substrate having a controlled liquid crystal orientation, the alignment regulating force on the substrate surface becomes strong, and the orientation spreads to the opposite substrate. In the sixth aspect, since the other substrate is not subjected to the orientation treatment, the homogeneous orientation state is expanded from the interface of the opposite substrate subjected to the orientation treatment by the annealing treatment, and a uniform orientation is obtained. In addition, since it is only necessary to perform the alignment treatment on one of the substrates, the number of steps can be reduced, leading to a cost reduction.

According to the method of manufacturing a liquid crystal display device of the present invention, the temperature of one substrate having a liquid crystal orientation whose surface is controlled is lower than the temperature of the other substrate. In this way, the nematic phase begins to appear at the interface of one substrate, and its orientation spreads toward the interface of the opposite substrate. A good orientation is obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of FIG.

FIG. 3 is a sectional view of a liquid crystal display device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Source electrode 2 Gate electrode 3 Drain electrode 4 Thin film transistor element 5 Leader electrode 6 Common electrode 7 Pixel electrode 8a, 8b Glass substrate 9a Polystyrene alignment film 9b Polyimide alignment film 10 Rubbing direction 11 Glass beads 12 Polyurethane alignment film

Claims (7)

[Claims] 1. A liquid crystal is sandwiched between a pair of substrates, an active element is disposed for each pixel on one of the substrates, and at least one pixel electrode is disposed on a substrate having the active element. Forming a linear pixel electrode and a common electrode on a substrate in the pixel, and providing a voltage applying means for generating an electric field in a horizontal direction with respect to the substrate surface when a voltage is applied between the electrodes. A liquid crystal display device, wherein the surface of one substrate has a controlled liquid crystal orientation and the surface of the other substrate has a large step due to the electrode, and the surface of the other substrate has a liquid crystal alignment at a temperature lower than the nematic-isotropic transition point of the liquid crystal. A liquid crystal display element having a property of disappearing power. 2. The liquid crystal display device according to claim 1, wherein a film of a thermoplastic polymer having a glass transition temperature equal to or lower than the nematic-isotropic transition point of the liquid crystal is formed on the other substrate surface. 3. The thermoplastic polymer having a glass transition temperature of 5
3. The liquid crystal display device according to claim 2, wherein the temperature is 0 ° C. or higher. 4. The liquid crystal display device according to claim 2, wherein the thermoplastic polymer is a polyurethane film having a shape memory effect. 5. The liquid crystal display device according to claim 1, wherein polyimide is formed on the surface of the substrate having controlled liquid crystal orientation. 6. The liquid crystal display device according to claim 1, wherein the other substrate is not subjected to an alignment treatment. 7. A structure in which one substrate surface is formed so as to have a controlled liquid crystal alignment property, and the other substrate surface has a property that the liquid crystal alignment force disappears at a temperature lower than the nematic-isotropic transition point of the liquid crystal. After being formed so as to have a liquid crystal panel in which liquid crystal is sealed between a pair of substrates, the surface of the liquid crystal panel has a controlled liquid crystal orientation in a process of cooling after raising the temperature above the nematic-isotropic transition point of the liquid crystal. And cooling the substrate while controlling the temperature of one of the substrates to be equal to or lower than the temperature of the other substrate.