JPH09152608A - Liquid crystal display device, and its manufacture and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the liquid crystal display device which is superior in visual angle characteristics and contrast, and to provide its manufacturing method and driving method. SOLUTION: This device has plural pixels having liquid crystal layers of nematic liquid crystal sandwiched between two substrates. Then this device features the coexistence of four fine areas A, B, C, and D which are fine areas differing in the twist direction of liquid crystal and fine areas differing in the rising direction of liquid crystal molecules. Specially, two areas where liquid crystal twists in the same direction and rise in different directions are not in line contact on a virtual plane. Further, the liquid crystal layers contains macromolecules to stabilize the four areas. The liquid crystal display device which is superior in visual angle dependency and has high contrast can be manufactured through a simple process similar to a conventional process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for displaying characters, figures, etc., a manufacturing method thereof and a driving method thereof, and is used as a liquid crystal display device having excellent visual characteristics and high contrast. .

[0002]

2. Description of the Related Art A conventional liquid crystal display device has an inherent problem that a viewing angle is narrow due to a characteristic behavior of liquid crystal molecules when a voltage is applied. The reason why a liquid crystal display device has a narrow viewing angle is that thin film transistors (thin film transistors) are used.
Torsed nematic (twisted nematic) that is often used in liquid crystal display devices driven by
c; TN) mode will be described as an example. 25 is a sectional view of the liquid crystal display device when no voltage is applied, and FIG. 26 is a sectional view of the liquid crystal display device when a voltage is applied.

[0003] Liquid crystal molecules are considered to be rod-like molecules.
In the N mode, liquid crystal molecules are sandwiched between two glass substrates as shown in FIG. That is, the liquid crystal molecules 11 in both the upper substrate 33 and the lower substrate 23 are aligned substantially parallel to the glass substrate. (However, they are aligned with a small pretilt angle 13 with the glass substrate interface.) Actually, the azimuth direction in the upper substrate plane of the liquid crystal molecules and the azimuth direction in the lower substrate plane are substantially 90 °. However, in order to make it easier to see in FIGS. 25 and 26, this 90 °
No twist of liquid crystal molecules is shown. No noticeable visual dependence occurs in this state in which no voltage is applied.

When a voltage is applied to this TN array, FIG.
As shown in, the liquid crystal molecules are arranged so as to be parallel to the electric field. At this time, the liquid crystal molecules tend to rise from the pretilt angle direction. The birefringence of liquid crystal molecules is determined by the angle between the long axis of the liquid crystal molecules and the light beam. Focusing on the liquid crystal molecules in the center of the cell in FIG. 26, the light ray 42 makes a large angle with the long axis of the liquid crystal molecule in the cell center, while the light ray 41 makes a small angle. Therefore, different optical characteristics are shown for the visual change to the left and the visual change to the right in FIG. In a normal liquid crystal display device, the horizontal direction in FIG. 26 is set to the vertical direction of the screen. Therefore, when the visual change in the upward direction is recognized as "whitening" in which the image becomes whitish and the contrast decreases, the image becomes darker when the visual change in the downward direction becomes dark and the negative / positive is reversed. Blackout "
Will be recognized as

A technique for solving this problem is disclosed in Japanese Unexamined Patent Publication No.
It is disclosed in JP-A-3-106624 (FIG. 27).
In this conventional technique, one pixel of the liquid crystal display device is divided into a plurality of regions (region I, region II), and the rubbing direction in adjacent regions is changed. The rubbing causes liquid crystal molecules on the surface of the alignment film to have a pretilt, but since the directions are different in the adjacent regions, the rising directions of the liquid crystal molecules when a voltage is applied are opposite. As a result, the visual dependency is canceled in the adjacent regions, and an element with little visual dependency can be obtained. That is, one pixel is divided into a region in which liquid crystal molecules rise from the left and a region in which liquid crystal molecules rise from the right, and when a light beam tilts, the angle formed by the liquid crystal molecules in one region and the light beam increases, and The angle formed by the liquid crystal molecules becomes smaller. As a result, the optical characteristics of the entire pixel become bilaterally symmetrical with respect to the inclination of the light beam, and the image reversal and whitening associated with the above-mentioned vision are suppressed.

Further, a technique of dividing one pixel into four regions by shifting the rubbing positions of the upper and lower substrates is disclosed in Japanese Patent Laid-Open No. 173135/1993.
8).

Another technique for solving the above problems is disclosed in Japanese Patent Laid-Open No. 6-194655 (FIG. 2).
9). In this conventional technique, the substrate surface is not rubbed, and liquid crystal molecules in the liquid crystal are 90 ° between the substrates.
A chiral agent is added to twist. When the liquid crystal is injected in the isotropic phase and cooled to room temperature, an element in which the orientation vector of the liquid crystal differs depending on the location and a continuously changing element is obtained. In this element, the contribution of each alignment state when light rays are tilted is averaged in all directions, so that a liquid crystal display device having a small visual dependency in any direction can be obtained.

Another technique for improving visual characteristics is disclosed in Japanese Patent Laid-Open No. 7-924466 (FIG. 30).
In this technique, by using a liquid crystal material containing a chiral material and an alignment film having a pretilt angle of 0 °, there is no need to perform rubbing a plurality of times.
A liquid crystal display device having a small visual dependency similar to that of Japanese Patent No. 24 is obtained.

[0009]

However, the above conventional liquid crystal display device has the following problems.

First, JP-A-63-106624 (FIG. 27) and JP-A-5-173135 (FIG. 2).
In the technique disclosed in 8), since different rubbing is performed on a minute area, a resist process and a plurality of rubbing processes are required as compared with a normal TN type liquid crystal display device manufacturing process. It is said that In addition, in order to accurately superimpose these small areas on the upper and lower substrates,
Two substrates must be bonded with high precision. As a result, the liquid crystal display device in these disclosed techniques has higher cost and lower productivity as compared with the conventional liquid crystal display device.

On the other hand, in the prior art disclosed in Japanese Patent Application Laid-Open No. 6-194655 (FIG. 29), the alignment film is not subjected to rubbing treatment, so that the alignment force of the liquid crystal molecules by the alignment film is weak and the liquid crystal becomes liquid crystal. When injected between the substrates in the phase state, the flow pattern at the time of injection remains and a good orientation state cannot be obtained. Therefore, in this conventional technique, the entire substrate is heated,
There is a problem that the liquid crystal must be injected in the isotropic phase state.

Further, JP-A-63-106624 (FIG. 27) and JP-A-6-194655 (FIG. 29).
Also, as a problem common to the technique disclosed in Japanese Patent Laid-Open No. 7-924466 (FIG. 30), there is a problem that the contrast is lowered due to light leakage from the boundary between the minute regions. That is, in the liquid crystal display devices according to these technologies, the twisting direction of the liquid crystal alignment vector (hereinafter referred to as “liquid crystal twisting direction”) is the same, but the rising direction of liquid crystal molecules (hereinafter referred to as “liquid crystal rising direction”) is different. Two areas coexist in a state where they are in contact with each other by a "line"("line" here)
Means that the boundary part looks like a "line" when viewed from the direction perpendicular to the substrate, and is in contact with the substrate as a "plane" that is almost perpendicular to the substrate when viewed three-dimensionally). As will be discussed later (FIG. 10), the liquid crystal molecules at the boundary between these two regions remain in the aligned state when no voltage is applied even when a voltage is applied. Therefore, even when black display is performed by voltage application (normally white mode), light leakage occurs from the boundary portion, the transmittance during black display is not sufficiently small, and a liquid crystal display device with high contrast is obtained. I can't.

As a method for solving this decrease in contrast, it is conceivable to provide a light-shielding mask at the boundary between the two regions. However, in this method, the aperture ratio of each pixel is lowered by the light-shielding mask, resulting in a liquid crystal display device. This causes a problem that the screen brightness decreases.

Further, Japanese Laid-Open Patent Publication No. 7-924466 (see FIG.
In the technique disclosed in 0), the non-uniform electric field is mainly generated at the end portion of the electrode when a voltage is applied, and the non-uniform electric field does not occur at the central portion of the electrode. Therefore, the rising direction of the liquid crystal at the center of the electrode may not coincide with the rising direction at the end of the electrode. This tendency is remarkable especially immediately after the voltage application. Further, when such rising occurs, two regions having different rising directions of the liquid crystal change with time, the visual characteristics in the oblique direction change with time, and the boundary portion is covered. There is a problem that the provided light-shielding mask does not function effectively.

The detailed situation of the movement of the boundary area is described in Japanese Patent Application No. 7-98336 (FIG. 3).
1). FIG. 31 shows a state after voltage application of a liquid crystal display device using electrodes having openings 35 in the diagonal direction. In the state H and the state L, the twist direction of the liquid crystal is the same,
2 shows two regions having different rising directions. Immediately after the electric field is applied and after a sufficient time has passed, the region is divided into two regions according to the opening 35, but immediately after the voltage is applied, a boundary portion is generated at a position different from the opening, and two types are formed at unintended positions. Area occurs.

Therefore, it is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a liquid crystal display device having excellent visual characteristics and contrast, a manufacturing method thereof, and a driving method thereof.

[0017]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and 1) a liquid crystal having a different rising direction without rubbing a minute region is provided.
Region, and further, a new technique for generating four regions in the liquid crystal layer in which the liquid crystal twist direction and rise direction are different, 2) the boundary between two regions in which the liquid crystal twist direction is different and two regions in which the liquid crystal rise direction is different The new finding that the parts behave optically differently (light leakage does not occur between two regions having different twist directions), 3) The boundary between the two regions having different twist directions of the liquid crystal has two different rising directions of the liquid crystal. A new technology to generate preferentially compared to the boundary of the area, 4)
It was made by discovering a new technology for stably coexisting and immobilizing such four minute regions.

Specifically, the liquid crystal display device according to the present invention is a liquid crystal display device in which a liquid crystal layer made of nematic liquid crystal is sandwiched between two substrates, and the rising directions of liquid crystal molecules in the liquid crystal layer are different from each other. It is characterized by the coexistence of irregular minute regions of species.

Further, another liquid crystal display device of the present invention is a liquid crystal display device in which a liquid crystal layer made of twisted nematic liquid crystal is sandwiched between two substrates, and in the liquid crystal layer, fine regions having different twist directions of liquid crystal are formed. It is characterized by coexistence of minute regions having different rising directions of liquid crystal molecules, and in particular, minute regions having the same twist direction of liquid crystal and different rising directions of liquid crystal molecules are in contact with each other on a virtual plane crossing the liquid crystal layer with a line. Characterized by not being.

Another liquid crystal display device of the present invention is a liquid crystal display device in which a liquid crystal layer made of a nematic liquid crystal is sandwiched between two substrates, and four minute regions having different twisting directions and rising directions of liquid crystal molecules are provided. Are co-existing within one pixel.

Another liquid crystal display device of the present invention is characterized in that a small amount of polymer is present in the liquid crystal layer in order to stabilize these minute regions and obtain a liquid crystal display device which does not change with time. And

Further, the present invention provides a method for manufacturing such a liquid crystal display device by injecting a liquid crystal between two substrates, and then applying a voltage to a liquid crystal phase-isotropic phase at a temperature not lower than a phase transition temperature. A method for cooling a liquid crystal layer to a temperature below a phase transition temperature is provided.

Further, the present invention is a technique for stably existing the structure manufactured by such a method, wherein the structure in which the liquid crystal layer contains a small amount of polymer and the liquid crystal layer is a monomer or an oligomer (hereinafter referred to as “monomer etc.”). And a method for producing a liquid crystal display device in which the monomer or the like is a polymer at a temperature of a liquid crystal phase-isotropic phase transition temperature of liquid crystal or higher.

Further, the present invention provides a driving method of such a liquid crystal display device, in which a voltage higher than a threshold voltage is applied even when a low level voltage is applied.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The structure and operation of the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged perspective view of a liquid crystal layer for one pixel when an intermediate voltage is applied to the liquid crystal display device of the present invention. In FIG. 1, as in FIG.
The 0 ° twist is omitted.

The liquid crystal display device according to the present invention is a liquid crystal display device in which a twisted nematic liquid crystal layer is sandwiched between two substrates, and liquid crystal molecules 11 are applied when a voltage is applied.
It is characterized in that two kinds of irregular minute areas A and B having different rising directions of coexist.

The expression "irregular minute area" used to specify the configuration of the present invention is a conventional technique in which one pixel is intentionally divided into two or more minute areas using a resist or the like. It is intended to exclude the "regular" minute area produced by, and the minute area having the regularity generated spontaneously by such an intentional method is also included in the "irregular minute area". .

The liquid crystal layer having such a structure for each pixel cancels the visual dependence of the two kinds of regions,
It is possible to obtain a liquid crystal display device having a wide viewing angle with little visual dependency in the vertical direction even in the halftone. A cross-sectional view of the liquid crystal layer in the halftone is shown in FIG. In FIG. 2, the regions A and B have the opposite relationship with respect to the oblique rays 41 and 42,
Visually dependent surnames offset.

Another example of the liquid crystal display device of the present invention will be described with reference to FIG. FIG. 3 is an enlarged view of one pixel of the liquid crystal display device of the present invention when an intermediate voltage is applied, as seen from the substrate vertical direction, showing the central portion of the cell thickness of each minute region (A, B, C, D). The rising state of liquid crystal molecules is shown. The arrow in FIG. 3 indicates the twist direction of liquid crystal molecules. In the present invention, regions A having different rising directions of liquid crystal molecules shown in FIG.
In addition to B, the twist direction is different from A and B,
There are a total of four types of minute regions, that is, regions C and D having different rising directions of liquid crystal molecules.

The rising directions of the liquid crystal molecules 11 in these four kinds of minute regions A, B, C and D are as shown in FIG.
They differ by 90 °. As described with reference to FIG. 24, the viewing angle in the rising direction of liquid crystal molecules (downward direction of a normal TN element) is narrow, but in the liquid crystal display device of the present invention, four kinds of liquid crystal rising directions and twisting directions different from each other are used. Since the minute regions coexist with each other and the resulting rising directions of the liquid crystal molecules are composed of four types of minute regions, a liquid crystal display device having a wide viewing angle without gradation inversion in all directions can be obtained.

From the viewpoint of improving visual characteristics, it is not desirable that the sizes of the four types of micro regions are too large, and it is desirable that the four types of micro regions coexist in each pixel. However, in some cases, a plurality of pixels may display one color, and it is not an essential requirement that four types of minute regions exist in one pixel.

FIG. 1 is composed of two types of minute regions, and FIG.
It is also possible to manufacture a liquid crystal display device which is composed of three kinds of minute areas, but in which three kinds of areas which are in the meanwhile coexist. As a specific method, a very small amount of a chiral agent is added, cooling is performed under voltage application, or the like.

An example of another liquid crystal display device having four kinds of minute regions according to the present invention will be described with reference to FIGS. FIG. 4 is an enlarged view of one pixel of the liquid crystal display device when an intermediate voltage is applied to the liquid crystal optical element of the present invention when viewed from the vertical direction of the substrate. In FIG. 4, the rising behavior of the liquid crystal molecules in the center of the liquid crystal layer is shown, and the direction of twist of the liquid crystal is shown by the arrow. 5 is a sectional view of the liquid crystal display device of the present invention taken along the line cc 'in FIG.

In the liquid crystal display device of the present invention, four minute regions are present in one pixel and the shape thereof is also controlled.

In the liquid crystal display device of the present invention shown in FIG. 4, not only the four minute regions A, B, C and D having different twisting and rising directions of the liquid crystal coexist, but also the liquid crystal in each pixel is Two regions whose rising directions are opposite to each other exist in symmetrical positions, and their sizes are also substantially equal. Therefore, "whitening" and "blackout" are exactly canceled, and excellent visual characteristics can be obtained in all directions.

In the liquid crystal display device of the present invention, "four minute regions" means that there are almost four minute regions having different twisting and rising directions of the liquid crystal, and strictly "4.
It does not need to consist of only one area. For example, it may be a case where any one of the regions is divided into two, or one pixel is divided into two or three and each of which is composed of four minute regions. Also,
As shown in FIG. 4, it is not necessary that the four minute regions are exactly divided into four equal parts, and the ratio may be intentionally changed.

On the other hand, the control of the four minute regions in the liquid crystal display device of the present invention includes a factor that occurs spontaneously as described later, so that the boundary portion is not limited to a straight line and may be a curved line.

Further, an important point in the liquid crystal display device of the present invention is that among four kinds of coexisting minute regions, regions in which liquid crystal molecules have the same twisting direction but different rising directions of liquid crystal molecules (see A in FIG. 3 or FIG. 4). B, C and D) are not touched by a line on the virtual plane.

As a result, the liquid crystal display device of the present invention is not only excellent in visual characteristics in the normally white mode, but also in Japanese Patent Laid-Open Nos. 63-106624 and 6-1.
Higher contrast can be obtained as compared with the conventional technique described in Japanese Patent Publication No. 94655.

The liquid crystal display device of the present invention is realized, for example, by using the following alignment means and liquid crystal material.

First, as the aligning means of the present invention, it is necessary to use an aligning means which produces two rising directions of liquid crystal molecules with almost the same probability. This is because, if the rising direction is only one direction, two or four types of minute regions do not occur. Therefore, when a rubbing alignment film is used as the alignment means, an alignment film that two rising directions are generated with almost the same probability is used.

As the alignment film in which two kinds of rising directions can coexist by such a single rubbing, the following two alignment films can be exemplified.

One is an alignment film having a small pretilt angle generated by rubbing.

In the conventionally known alignment film, the rising direction of liquid crystal molecules is determined by the rubbing direction.
This is because the rubbing operation causes the alignment film to have a pretilt angle parallel to the rubbing direction. Therefore, in the conventional alignment film, it is impossible to generate two types of regions having different rising directions of liquid crystal molecules by one rubbing, or it is extremely unstable even if two types of regions are generated. It was not practical.

The present invention has been made by solving this problem, and by using an alignment film in which two kinds of rising directions can coexist stably by one rubbing,
A liquid crystal display device having a wide viewing angle and high contrast can be obtained by the same simple steps as those for manufacturing a conventional TN type liquid crystal display device. That is, similar to the conventional process, one rubbing produces two types of regions having different rising directions of liquid crystal molecules, or regions having different twisting directions of liquid crystal and four types of regions having different rising directions of liquid crystal molecules. The liquid crystal display device of the present invention having a wide viewing angle can be obtained. Therefore,
Since rubbing is not required for each minute area,
The rubbing process and the resist process which are performed a plurality of times as in the technique disclosed in Japanese Patent Laid-Open No. 3-106624 and Japanese Patent Laid-Open No. 5-173135 are unnecessary. Further, since each substrate is rubbed once, the alignment force on the liquid crystal molecules is strong, and the flow alignment at the time of injection does not matter. Therefore, room temperature implantation is possible and there is no need to heat the substrate during implantation.

As the alignment film having such a low pretilt angle, specific polyimide, polystyrene, etc. can be mentioned. By using an alignment film having a small pretilt angle, the energy difference when the rising directions of the liquid crystal molecules are different is small, and the liquid crystal molecules of the present invention are stable in both directions when the voltage is applied and the liquid crystal molecules rise from both directions. A display device can be obtained. Specific examples include an alignment film having a pretilt angle of 0.5 ° or less as such a low-pretilt alignment film. Further, when a certain kind of polymer (for example, polystyrene) is used as the alignment film, the polymer chains are aligned perpendicular to the rubbing direction, and the liquid crystal molecules are also aligned perpendicular to the rubbing direction. In such an alignment film, the rubbing direction and the pretilt generation direction are perpendicular to each other, and the pretilt angle is almost zero.

The pretilt angle can be measured by the crystal rotation method or the like.

On the other hand, in the liquid crystal device of the present invention having two kinds of minute regions having different rising directions, an alignment film having a small pretilt angle is not used, and a chiral agent is added to increase
The rising directions of seeds can also be generated with almost equal probability.

As the aligning means used in the liquid crystal display device of the present invention, one that aligns liquid crystal molecules on the surface of the substrate in one direction by using polarized light or one that aligns by minute uneven grooves such as groups is used. However, even in this case, the rising edges in the two directions need to be generated with almost equal probability. This corresponds to the fact that the orientation plane and minute grooves due to polarized light need not be inclined with respect to the substrate, and can be easily produced by a usual method. Examples of the alignment treatment method using linearly polarized light include, for example, Japan Journal of Applied Physics (Jap. J. App.
l. Phys. ), Vol. 31 (1992) PP. 2
155-2164 or Nature
e), Vol. 351 (1991) PP. 49-50. In addition to using these alignment films alone, after applying these alignment films and performing alignment treatment with linearly polarized light, for example, Liquid Crystals (Li
(quidCrystals), Vol. 18, (199
5) By applying a liquid crystalline monomer having a photopolymerizable group as described in PP319-326, orienting the liquid crystalline monomer in the direction perpendicular to the polarization direction, and then photopolymerizing it to use as an alignment film, A more stable alignment state can be obtained.

Another method in which the rising directions of the two kinds of liquid crystals are allowed to coexist in a stable manner is to twist the liquid crystal layer in the liquid crystal display device having two kinds of irregular regions shown in FIG. This is due to the inclusion of a chiral material having

The splay array is the orientation state shown in FIG. 6 (90 ° twist is omitted in FIG. 6 for the sake of clarity), and is in opposition to the normal tilt array shown in FIG.

When an alignment film having a small pretilt is used, the difference between the splay alignment and the normal tilt alignment is small, but they are not completely the same, and there is a difference in the stability of two types of regions having different rising directions of liquid crystal molecules. Is recognized. That is, by using the splay array, it is possible to obtain a stable minute region in which the ratio of the two rising regions is substantially equal and does not change with time.

FIG. 7 shows the relationship between the rubbing direction and the alignment of liquid crystal molecules. Reference numerals 24 and 34 denote rubbing directions of the upper substrate and the lower substrate, respectively. In FIG. 7, C is a splay array and D is a normal tilt array.

When an alignment film in which liquid crystal molecules are aligned perpendicular to the rubbing direction is used, the pretilt angle does not occur in a specific direction in principle. However, actually, there are cases where two types of regions having different rising directions with respect to both twisting directions are not equally stable due to delicate conditions during rubbing. Therefore, the direction in which the two kinds of regions are stabilized is experimentally determined, and a chiral agent having an appropriate rotation direction is added.

Next, from the point of view of the liquid crystal material, its twisting property is important in the liquid crystal display device of the present invention.

In the liquid crystal display device of the present invention, the twist direction of liquid crystal molecules can be freely controlled by adding a chiral agent.

When the splay alignment is controlled as described above by adding the chiral material, or when the alignment film having a low pretilt angle is used and the twist direction is controlled in one direction, the rising directions of the liquid crystal molecules are different. The liquid crystal display device of the present invention as shown in FIG. 1 in which only two types of regions coexist can be obtained.

On the other hand, when the chiral material is not added at all or the addition amount is small, a total of four types of micro regions, that is, micro regions having different twist directions of liquid crystal and micro regions having different rising directions of liquid crystal molecules coexist. The liquid crystal display device shown in FIG. 3 or 4 is obtained. That is, since two regions having different twist directions are generated with almost equal probability, the liquid crystal display device of the present invention in which four types of regions are generated with almost equal probability can be obtained. The liquid crystal display device of the present invention also has an advantage that the driving voltage does not increase because the liquid crystal layer does not contain a chiral material.

Further, by controlling the amount of the chiral material to be extremely small, it is possible to obtain a liquid crystal display device in which four types of regions exist but the abundance ratios thereof are different. As a result, it is possible to intentionally make the sizes of regions of liquid crystal different in twist direction as shown in FIG. this is,
It is not always best for the liquid crystal display device to have a viewing angle characteristic of four-fold symmetry as shown in FIG. 4, and the liquid crystal display device should have a wide field of view in the vertical direction and a wide field of view in the horizontal direction. Is sometimes required. Therefore, in the liquid crystal display device of the present invention, by adding a small amount of a chiral agent, a liquid crystal display device having a wider viewing angle in the vertical direction and a liquid crystal display element having a wider viewing angle in the lateral direction can be freely produced. .

Also in a liquid crystal display device having an intermediate viewing angle characteristic, it is possible to obtain a structure in which regions in which the liquid crystal molecules have the same twisting direction and the rising directions of the liquid crystal molecules are not in direct contact with each other are obtained. be able to.

As described above, by using the aligning means in which the rising directions of the four liquid crystal molecules are generated and the liquid crystal material which does not have the property of twisting in one direction, the regions having different twisting directions of the liquid crystal molecules and the rising directions of the liquid crystal molecules are A liquid crystal display device in which different regions coexist can be obtained. However, with this condition alone, a liquid crystal display device in which "four minute regions" as shown in FIGS. 4 and 8 coexist cannot be obtained, and a liquid crystal display device in which four types of regions are randomly generated is obtained.

By eliminating the randomness of the four types of regions and intentionally controlling the shapes of the four minute regions, a liquid crystal display device with more excellent viewing angle characteristics can be obtained. As such a method, use of a non-uniform electric field can be considered. For example, as shown in FIG. 5, the electrode 32 on the upper substrate 33 may be made larger than the electrode 22 on the lower substrate 23 so that the electrodes on the two substrates have different shapes, or at least one of them as shown in FIG. The opening 35 can be provided in the electrode 32 on the substrate. As such an opening, in addition to the shapes such as “+”, “x”, and “/”,
A straight line, a circle, a polygon, etc. can be used as appropriate. In addition, in a normal substrate with TFT, the common electrode side and the T
The electrodes on the FT substrate side generally have different shapes, and the liquid crystal display device of the present invention can be obtained by directly utilizing the nonuniform electric field due to the difference in shape. In this case, what kind of voltage is applied during cooling is particularly important.

The voltage applied to generate the four minute regions may be a constant voltage or a high frequency AC wave voltage that the liquid crystal molecules cannot respond to, but in particular, a low frequency to which the liquid crystal molecules respond. By using the triangular wave, sine wave, rectangular wave, etc., it is easier to obtain a liquid crystal display device having good characteristics in which regions having the same twist direction but different rising directions are not in contact with each other by a line.

An important point in the liquid crystal display device of the present invention in which there are four kinds of regions is that among the four coexisting minute regions, the regions in which the liquid crystal has the same twist direction but different liquid crystal rising directions (FIG. 3 or 4). A and B, C and D) do not contact with each other on a virtual plane by a line.

The reason for defining "on a virtual plane" is as follows. In FIG. 4, it can be said that two regions having different twist directions of the liquid crystal, for example, B and C, are in contact with each other by a “line” (this boundary portion does not cause light leakage). However, considering that the liquid crystal layer has a finite thickness and is three-dimensional, strictly speaking, B and C are in contact with each other on a “plane”. Similarly, regions in which the liquid crystal has the same twisting direction and different liquid crystal rising directions, for example, A and B, are in contact with each other at "points" in FIG.
In contact.

“On a virtual plane” is defined so that such misunderstanding does not occur. For example, a plane parallel to the upper and lower substrates 23 and 33 can be considered as a virtual plane, and the boundary line on this plane is equal to that in FIG. 4, for example. Therefore, the "virtual plane" defining the content of the present invention does not include a plane perpendicular to the substrate.
However, as is apparent from the fact that the liquid crystal display device may be viewed from an oblique direction, it does not need to be strictly parallel to the substrate, and may be a virtual plane inclined with respect to the substrate surface.

Since the regions having the same twisting direction of the liquid crystal but different rising directions of the liquid crystal among the four minute regions have a structure in which they are not in contact with each other on a virtual plane,
The liquid crystal display of the present invention has the following advantages.

First, the liquid crystal display device of the present invention not only has excellent viewing angle characteristics due to such a structure,
In comparison with the liquid crystal display devices disclosed in Japanese Patent Laid-Open No. 106624/1995 and Japanese Patent Laid-Open No. 7-924466, it is possible to obtain a high contrast liquid crystal display device in a normally white mode without using a light shielding mask or the like.

In particular, in the liquid crystal display device in which the four types of regions shown in FIG. 3 have irregular shapes and therefore a large number of boundaries exist, and the control thereof is difficult, light leakage does not occur from the boundaries. The effect is remarkable.

The reason why the liquid crystal display device of the present invention having such an effect has a high contrast will be described in more detail with reference to FIGS. FIG. 10 shows a boundary between regions where the liquid crystal has the same twisting direction and different rising directions, and FIG. 11 shows a boundary between regions where the liquid crystal has different twisting directions. Further, (a) shows a voltage non-application state, and (b) shows a voltage application state. The liquid crystal molecules at the boundary between two regions having the same liquid crystal twist direction and different liquid crystal rise directions shown in FIG. 10 remain horizontal to the substrate even when a voltage is applied, and twist 90 ° when a voltage is not applied. The initial state is kept as it is (FIG. 10B). Therefore, in the normally white mode, the boundary portion remains in the “white” state when no voltage is applied even when the voltage is supposed to be “black” display, and “black” is caused by light leakage at the boundary portion. The display transmittance increases, and as a result, the contrast of the liquid crystal display device decreases. On the other hand, at the boundary portion (FIG. 11) of the two regions having different twist directions of the liquid crystal, the liquid crystal molecule at the boundary portion changes its alignment direction to the electric field direction when a voltage is applied, and becomes different from the liquid crystal molecule in the normal TN cell. Similarly, under sufficient voltage application,
It is perpendicular to the substrate (FIG. 11A). Therefore, the display when the voltage is applied is "black" even at the boundary between the two regions having different twist directions, and a liquid crystal display device with high contrast can be obtained.

Other advantages of the liquid crystal display device of the present invention having a structure in which regions in which the liquid crystal has the same twisting direction but different rising directions do not contact with each other on a virtual plane are the following points.

In the method of intentionally rubbing in every minute area as disclosed in Japanese Patent Laid-Open No. 5-173135, the rising direction of the liquid crystal is determined by the regulating force from the surface by rubbing, and thus the pixel center Even in the area, a region in which the rising directions of the liquid crystal are opposite is unlikely to occur. However, when a voltage is not applied like the liquid crystal display device disclosed in Japanese Patent Laid-Open No. 4-92466, a uniform region is formed,
In a liquid crystal display device in which regions having different rising directions of liquid crystal are generated by the action of a non-uniform electric field only when a voltage is applied,
A region in which the rising directions of the liquid crystal are opposite is likely to occur in the central portion of the pixel where the nonuniform electric field is weak. On the other hand, in the liquid crystal display device of the present invention, since there are regions of different twist directions of the liquid crystal even when no voltage is applied, each region when no voltage is applied becomes a small region,
Since the regions with different twisting directions of the liquid crystal are present alternately (this is equivalent to the regions with different twisting directions of the liquid crystal being not in contact with the lines with different rising directions), the rising directions of one region are opposite Even in the case of, the problem of light leakage at the boundary with the adjacent region does not occur, and stable optical characteristics can be obtained.

The reason why a structure in which the liquid crystal display device of the present invention has the same liquid crystal twist direction and two types of regions having different rising directions are not in contact with each other by a line is explained as follows.

At the boundary between the regions where the rising direction of the liquid crystal molecules or the twisting direction of the liquid crystal is different, the liquid crystal is in a distorted orientation as compared with the region other than the boundary, and this distortion causes a high energy state. However, the strain of the liquid crystal is different at the boundary between the regions having different rising directions and the boundary between the regions having different twisting directions, and the strain energy is naturally different. If the strain energy at the boundary of different regions in the rising direction is higher than the strain energy at the boundary of different regions in the twisting direction, the boundary of the regions in different twisting directions takes precedence over the boundary in the region of different rising directions. Expected to be generated.

Based on such knowledge, the present invention discloses a liquid crystal display device in which two kinds of regions having the same liquid crystal twist direction and different rising directions are not in contact with each other by a line, and a manufacturing method thereof. Is also disclosed. Less than,
A method for manufacturing the liquid crystal display device of the present invention will be described.

In the liquid crystal display device provided with the above-mentioned orientation means and liquid crystal material, in order to obtain four kinds of regions having different twisting directions and rising directions of liquid crystal as substantially equal proportions and minute regions, the liquid crystal layer is once or the like. It is desirable that the liquid crystal phase-isotropic phase is cooled to a temperature not higher than the phase transition temperature after heating to the isotropic phase. In this process, a large number of liquid crystal droplets are generated from the isotropic phase, and four types of regions having different twisting directions and rising directions of the liquid crystal are generated. At this time, what is important is that this cooling operation is performed under voltage application, as specified in the method of manufacturing the liquid crystal display device of the present invention. As a result, it is possible to obtain the liquid crystal display device of the present invention in which the twisting directions of the liquid crystal are the same and the two types of regions having different rising directions are not in line contact with each other on the virtual plane.

The reason why the liquid crystal display device of the present invention can be obtained under such conditions is explained as follows. In the state where no voltage is applied, the regions in which the twisting directions are the same and the rising directions are different are substantially the same (FIG. 10A). Therefore, no strain energy is generated at the boundary of this region. On the other hand, the boundary between the regions having different twist directions exists even when no voltage is applied, and the strain energy is high.
As a result, when a cooling operation is performed without applying a voltage, a structure in which two types of regions having the same twist direction but different rising directions are in contact with each other with a line is easily generated, and a liquid crystal display device with high contrast cannot be obtained. On the other hand, under voltage application, as expected in FIGS. 10 (b) and 11 (b),
At the boundary between the regions with the same twist direction but different rising directions, it is considered that the strain energy increases rapidly as the applied voltage increases because the liquid crystal at the boundary remains in the state of no voltage applied. Since the liquid crystal molecules in the regions having different twist directions are turned to the electric field direction like the surrounding liquid crystal molecules, the strain energy does not increase so much. Therefore, when the cooling operation is performed under voltage application,
It is possible to obtain a liquid crystal display device having a wide viewing angle and high contrast in which regions having the same twisting direction but different rising directions are not in contact with each other by lines.

Considering the manufacturing process of the liquid crystal display device of the present invention, the advantages of the structure of the present invention in which regions in which the liquid crystal has the same twisting direction but different rising directions are not in line contact with each other on a virtual plane are further considered. Can be revealed. In the method of intentionally performing rubbing for each minute region, the rising direction of the liquid crystal is determined by the rubbing direction, so that the regulating force is generated from the surface and the rising region as controlled is obtained even in the central portion of the pixel. On the contrary,
Each minute region in the liquid crystal display device of the present invention is generated from liquid crystal droplets generated at the time of cooling from the isotropic phase, and in a region where a sufficient nonuniform electric field is not applied, control of the shape of each region tends to be insufficient. . However, even in this case, since the liquid crystal display element of the present invention has a structure in which the regions in which the liquid crystal has the same twisting direction and different rising directions are not in contact with each other with a line, there is no light leakage from the boundary portion and high contrast is obtained. Can be maintained.

Although the above-mentioned liquid crystal display device of the present invention basically has excellent characteristics of wide viewing angle and high contrast, it is not without problems.

For one, there is a case where the minute region is not sufficiently stable, and in particular, during the repetition of voltage ON-OFF,
The boundary may move and any of the minute areas may disappear. Another problem is that the rising direction of the liquid crystal molecules immediately after the voltage application may be different from the stable rising direction after a sufficient time has passed. As a result, immediately after the voltage is applied, two regions having the same twisting direction of the liquid crystal and different rising directions are in contact with each other by a line, and light leakage occurs from the boundary portion, and the boundary portion is in an equilibrium state at a slow speed of the second order. Since it moves toward the front, the response speed becomes slower, and the characteristics in the diagonal direction may change as the boundary moves. Further, there is a problem that the minute region of the liquid crystal display device of the present invention disappears when the liquid crystal layer is heated to an isotropic phase, and when the liquid crystal layer is heated to the isotropic phase, again,
There is a problem that it is necessary to generate a minute area under a non-uniform electric field.

In order to solve these problems, as another invention, a liquid crystal display device in which a polymer is present in a liquid crystal layer and a manufacturing method thereof will be disclosed.

As such a liquid crystal display device, there may be mentioned one in which a small amount of polymer 12 is dispersed in a liquid crystal as shown in FIG. 12, for example, in a network form. The presence of this polymer stabilizes the four microregions,
It is possible to obtain a liquid crystal display device in which the boundary portion does not move even when the voltage is turned on and off repeatedly and the four minute regions do not disappear. In this case, since fixing of the four minute regions is a problem, even if the amount of the polymer is considerably small, a sufficient effect can be obtained. In addition, the presence of the polymer 12 fixes the rising direction of the liquid crystal molecules immediately after the voltage is applied to the same position as the stable rising direction after a sufficient time has passed, and there is no light leakage from the boundary, and the response It doesn't slow down. Furthermore, when the amount of the polymer is large, it is possible to obtain a liquid crystal display device which recovers to the initial state even when the liquid crystal layer is heated to an isotropic phase and then cooled.

The polymer, which is present in a small amount in the liquid crystal layer of the present invention, is for stabilizing the regions in which the twisting direction of the liquid crystal and the rising direction of the liquid crystal molecule are different. The shape and the like are not limited.
Therefore, a polymer may be present on the substrate in the form of a protrusion,
It is also possible to disperse fine beads or the like in the alignment film to make unevenness.

Further, since fixing of a minute area on the surface of the alignment film is a problem, a considerably small amount of polymer is sufficient. On the other hand, when the amount of the polymer is too large, the alignment of the liquid crystal molecules is disturbed by the polymer and the 90 ° twist is not generated, or the polymer causes scattering to cause a reduction in contrast. Therefore, the amount of the polymer is preferably 0.02 wt% or more and 4 wt% or less in the liquid crystal layer, although it depends on the type of the polymer and the interaction with the liquid crystal molecules.

In the liquid crystal display device of the present invention shown in FIGS. 1 and 3, the rising direction of the liquid crystal molecules can be either of two directions, which is optional, but when the polymer is dispersed. Since a small amount of the coexisting polymer remembers the rising direction when the voltage is first applied, the liquid crystal molecules rise in the first rising direction and the boundary of the minute region does not move. That is, the position of the boundary portion of the minute region is fixed by the coexistence of the polymer dispersed in the liquid crystal in a small amount, and the response speed and the contrast ratio of the liquid crystal display device are not lowered. However, in order to limit the rising direction of the liquid crystal molecules, more polymers are needed than to stabilize the minute regions.

As the polymer 12 to be dispersed in the liquid crystal layer in the present invention, it is possible to introduce a polymer dispersed in liquid crystal between the substrates, or to introduce a monomer or the like between the substrates, It is also possible to react them with each other to form a polymer. However, it is desirable to react a monomer or the like in the liquid crystal phase from the viewpoint of ease of injection and stabilization of initial alignment. Further, in this method, there is also an advantage that by reacting a monomer or the like under application of a voltage, a pretilt is given to the initial alignment of liquid crystal molecules, and the driving voltage and the response speed can be improved. Therefore, the present invention also provides a method for manufacturing such a liquid crystal display device.

That is, a liquid crystal solution containing a small amount of a monomer or an oligomer is injected between two substrates combined so as to form irregular regions in which the rising directions of the liquid crystal molecules are different when a voltage is applied, and then the monomer is injected. Alternatively, a method for manufacturing a liquid crystal display device in which an oligomer is reacted is provided.

Further, when a monomer or the like is reacted in the liquid crystal by irradiation of ultraviolet rays or the like, a polymer is formed in a state where the orientation of the liquid crystal is memorized.

On the other hand, in the case of a liquid crystal display device including minute regions having different twist directions, by irradiating ultraviolet rays at a temperature at which the liquid crystal becomes an isotropic phase, a polymer having no relation to the orientation of the liquid crystal is formed, or Alternatively, a method of irradiating with ultraviolet rays in a form in which a minute region is prepared in advance and the orientation state thereof is fixed is desirable. In this case, it is also useful to carry out the curing of the monomer in two stages. That is, a minute region is formed after the weak reaction in the first step, and the reaction in the second step is allowed to proceed in a state where this is present in a stable manner to fix the rising direction of the liquid crystal molecules immediately after the voltage application. is there.

Also in the manufacture of a liquid crystal display device containing a monomer or the like, the liquid crystal layer can be cooled from a phase transition temperature of the liquid crystal phase-isotropic phase to a phase transition temperature or lower under application of a voltage, and a wide viewing angle and a wide viewing angle can be obtained. Although it is useful for manufacturing high-contrast liquid crystal display devices, in the method of reacting monomers etc. in liquid crystal to form a polymer, the conditions under which the monomers etc. are reacted depend on the characteristics of the liquid crystal display device. Affect. That is, when a monomer or the like is reacted in a state where a liquid crystal material such as room temperature forms a liquid crystal phase, the polymer formed by the reaction stores the orientation of the liquid crystal phase. Therefore, when the monomer is reacted under such conditions, it is difficult to uniformly obtain the four minute regions by the heating-cooling process thereafter.

Therefore, as another invention, in a method for manufacturing a liquid crystal display device in which a liquid crystal layer contains a small amount of a monomer and the monomer or the like is reacted to form a polymer, a liquid crystal phase of liquid crystal
Disclosed is a method for producing a liquid crystal display device in which a monomer or the like is reacted at a temperature equal to or higher than a phase transition temperature of an isotropic phase to form a polymer. As a result, the orientation of the generated polymer is random, and good four fine regions can be obtained according to the cooling conditions of the liquid crystal layer after the reaction of the monomers and the like.

Therefore, the characteristics of the liquid crystal display device change depending on the conditions under which the ultraviolet irradiation or the like is performed. In the case of a liquid crystal display device in which the twisting direction is limited to only one direction and there are two kinds of minute regions having different rising directions, it is desirable to cure the monomer at room temperature because of the stability of the liquid crystal when no voltage is applied. .

Further, as a method for reacting a liquid crystal display device including minute regions having different twist directions at room temperature,
There is a method of curing a monomer or the like in a state where liquid crystal molecules are erected by applying a voltage. When the monomer concentration is low, the binding force of the polymer formed by the reaction is weak, so the liquid crystal molecules are aligned in a direction parallel to the substrate surface, except for the voltage after the reaction.
Further, by reacting a monomer or the like under application of a voltage, there is an advantage that a pretilt is given to the initial alignment of liquid crystal molecules and a driving voltage and a response speed can be improved.

When four minute regions are formed after the reaction of the monomer or the like, it is not desirable to react the monomer or the like at a temperature below the isotropic phase-liquid crystal phase transition temperature, but on the contrary, it is already formed. From the viewpoint of fixing the four minute regions, the structure can be fixed by reacting a monomer or the like at room temperature. The four minute regions of the liquid crystal display device of the present invention usually disappear when the liquid crystal layer is heated to the isotropic phase. However, after the formation of the four micro regions, the monomers and the like in the liquid crystal layer are reacted to form a polymer to fix or store this structure, and even when heated to a temperature higher than the phase transition, the liquid crystal phase is cooled. As a result, a liquid crystal display device can be obtained in which the four minute regions are recovered again.

Therefore, as another invention of a method of manufacturing a liquid crystal display device, in a method of manufacturing a liquid crystal display device in which a monomer or the like in a liquid crystal layer is reacted, the monomer or the like is reacted in two or more times. A method for manufacturing a display device is disclosed. In the present invention, a polymer that helps stabilize the four microregions is formed in the weak reaction in the first step, and four microregions are generated by subsequent cooling, and this structure is fixed by the reaction in the second step. It is a thing. Therefore, in the present invention, the first stage reaction is mainly carried out at a temperature below the phase transition temperature, and the second stage reaction is carried out at a temperature above the phase transition temperature.

As the monomers and oligomers used in the present invention, any of photocurable monomers, thermosetting monomers and oligomers thereof can be used, and if they contain these, other components are included. You can leave. The "photocurable monomer or oligomer" used in the present invention includes not only those which react with visible light but also ultraviolet curable monomers which react with ultraviolet light, and the latter is particularly desirable from the viewpoint of easy operation.

The polymer used in the present invention may have a structure similar to that of the liquid crystal molecule, but it is not necessarily used for the purpose of aligning the liquid crystal, and therefore it has flexibility such as having an alkylene chain. May be present. Further, it may be a monofunctional one, a difunctional one, a trifunctional or higher polyfunctional monomer, and the like.

Examples of the photo- or UV-curable monomer used in the present invention include 2-ethylhexyl acrylate, butyl ethyl acrylate, butoxyethyl acrylate, 2-cyanoethyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl acrylate, Ethoxyethyl acrylate, NUN-diethylaminoethyl acrylate,
NUN-dimethylaminoethyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, isobonyl acrylate, isodecyl acrylate, lauryl acrylate, morpholine acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, 2, 2,2-trifluoroethyl acrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2,2,3,3-
Tetrafluoropropyl acrylate, 2,2,3
Monofunctional acrylate compounds such as 4,4,4-hexafluorobutyl acrylate, 2-ethylhexyl methacrylate, butyl ethyl methacrylate, butoxyethyl methacrylate, 2-cyanoethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, 2-hydroxypropyl methacrylate, 2-ethoxy. Ethyl acrylate, NUN-diethylaminoethyl methacrylate, NUN-dimethylaminoethyl methacrylate, dicyclopentanyl methacrylate, dicyclopentenyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, isobonyl methacrylate, isodecyl methacrylate, lauryl methacrylate, morpholine methacrylate, phenoxy Ethylmethac Rate, phenoxydiethylene glycol methacrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, etc. Methacrylate compounds, 4,4'-biphenyldiacrylate,
Diethylstilbestrol diacrylate, 1,4-
Bisacryloyloxybenzene, 4,4′-bisacryloyloxydiphenyl ether, 4,4′-bisacryloyloxydiphenylmethane, 3.9-bis [1,1-dimethyl-2-acryloyloxyethyl]
-2,4,8,10-Tetraspiro [5,5] undecane, α, α'-bis [4-acryloyloxyphenyl] -1,4-diisopropylbenzene, 1,4-bisacryloyloxytetrafluorobenzene, 4 , 4 '
-Bisacryloyloxyoctafluorobiphenyl,
Diethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, dicyclopentanyl diacrylate,
Glycerol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol Hexaacrylate,
Dipentaerythritol monohydroxypentaacrylate, 4,4′-diacryloyloxystilbene,
4,4'-diacryloyloxydimethylstilbene,
4,4'-diacryloyloxydiethylstilbene,
4,4'-Diacryloyloxydipropylstilbene, 4,4'-Diacryloyloxydibutylstilbene, 4,4'-Diacryloyloxydipentylstilbene, 4,4'-Diacryloyloxydihexylstilbene, 4,4'- Diacryloyloxydifluorostilbene, 2,2,3,3,4,4-hexafluoropentanediol, 1,5-diacrylate, 1,1,
Polyfunctional acrylate compounds such as 2,2,3,3-hexafluoropropyl-1,3-diacrylate and urethane acrylate oligomer, diethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate,
1,3-butylene glycol dimethacrylate, dicyclopentanyl dimethacrylate glycerol dimethacrylate, 1,6-hexanediol dimethacrylate,
Neopentyl glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, pentaerythritol trimethacrylate, ditrimethylolpropane tetramethacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol monohydroxypentamethacrylate, 2, There are, but not limited to, polyfunctional methacrylate compounds such as 2,3,3,4,4-hexafluoropentanediol 1,5-dimethacrylate and urethane methacrylate oligomers, styrene, aminostyrene and vinyl acetate. .

Further, the driving voltage of the device of the present invention is influenced by the interfacial interaction between the polymer material and the liquid crystal material, and therefore may be a polymer containing elemental fluorine. Examples of such polymers include 2,2,3,3,4,4-hexafluoropentanediol, 1,5-diacrylate, 1,1,
2,2,3,3-hexafluoropropyl-1,3-diacrylate, 2,2,2-trifluoroethyl acrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2,2,3 , 3-tetrafluoropropyl acrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2 Examples of the polymer include, but are not limited to, polymers synthesized from compounds containing 2,3,4,4,4-hexafluorobutyl methacrylate, urethane acrylate oligomer, and the like.

When a photo- or UV-curable monomer is used as the polymer used in the present invention, a photo- or UV-ray initiator is generally used. Various initiators can be used, for example, 2,2-diethoxyacetophenone, 2-hydroxy-2-methyl-1
-Phenyl-1-one, 1- (4-isopropylphenyl-)-2-hydroxy-2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-
Acetophenones such as 2-methylpropan-1-one,
Benzoin compounds such as benzoin methyl ether, benzoin ethyl ether and benzyl dimethyl ketal, benzophenone compounds such as benzophenone, benzoyl benzoic acid, 4-phenylbenzophenone and 3,3-dimethyl-4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone , A thioxanthone such as 2-methylthioxanthone, a diazonium salt, a sulfonium salt,
Iodonium salts, selenium salts and the like can be used.

As another method for solving the problem caused by the rising direction of the liquid crystal molecules immediately after the voltage application, the present invention also provides a driving method of a liquid crystal display device which limits the rising direction of the liquid crystal molecules. is there.

According to the method of driving a liquid crystal display device of the present invention, in a liquid crystal display device in which regions having different rising directions of liquid crystal molecules exist between two substrates, the threshold value of the liquid crystal molecules is maintained even when a low level voltage is applied. The above voltage is applied. Here, the “low level voltage” refers to the voltage level when the applied voltage is the lowest in the gradation display.

FIG. 1 shows the driving method of the liquid crystal display device of the present invention.
3 and FIG. 14 will be described. FIG. 13A shows an example of a voltage waveform applied to a liquid crystal cell in the method for manufacturing a liquid crystal display device of the present invention, while FIG. 13B shows an applied voltage waveform used for driving a conventional liquid crystal display device. This is an example.
High-level and low-level voltages correspond to black display and white display in the normally white mode, respectively.

The relationship between the applied voltage shown in FIG. 13 and the transmittance of the liquid crystal cell will be described with reference to FIG.

The applied voltage in the conventional drive waveform was switched between the B state and the C state. The B state includes the case where the applied voltage is 0 V, and in this voltage applied state, the liquid crystal molecules are parallel to the substrate surface. Therefore,
When the applied voltage is changed from B to C, the rising directions of the liquid crystal molecules can be two directions, and light leakage occurs at the boundary of the regions having different rising directions and the second order is slow due to the movement of the boundary. The response and the viewing angle characteristics change.

On the other hand, the driving method of the liquid crystal display device of the present invention is characterized in that the voltage A higher than the threshold voltage of the liquid crystal molecules is applied even in the low level voltage application state. Since the applied voltage A is higher than the threshold voltage of the liquid crystal molecules, the liquid crystal molecules in the A state are already slightly raised in either direction. Therefore, even when a high level voltage C is applied, the liquid crystal molecules rise while maintaining the rising direction of the liquid crystal molecules in the A state, and the rising direction of the liquid crystal molecules when a large voltage is applied is defined as one direction. To be done. As a result, the rising direction of the liquid crystal molecules is regulated in one direction, and the boundary part with the "white" display does not occur, light leakage, slow response of the second order due to the movement of the boundary part, and change of the viewing angle characteristics Does not happen.

The device of the present invention is used for a TFT (thin film).
In order to drive as an active element such as an m transistor (thin film transistor), the liquid crystal is required to have a large electric resistance and a large charge retention rate. Therefore,
It is desirable that the liquid crystal material has a high resistance such as a fluorine-based or chlorine-based material, and that does not deteriorate the charge retention characteristics due to irradiation with visible light or ultraviolet light.

In the liquid crystal optical element of the present invention, the viewing angle characteristics can be further improved by using the compensator between the liquid crystal cell and the polarizing film. As a compensating plate for this purpose, a compensating plate having a negative refractive index anisotropy is desirable because it compensates a liquid crystal having a positive refractive index anisotropy. Particularly, in a liquid crystal display device in which four regions coexist, the problem of coloring in the oblique direction is canceled out due to its symmetry, and good viewing angle characteristics without coloring can be obtained. Also,
An alignment film having different characteristics for each micro region corresponding to the four micro regions of the liquid crystal layer is particularly desirable. Further, it is also desirable to use a compensator having an oblique optical axis. In particular, FIGS.
In the liquid crystal display device in which the four regions coexisting with each other, the problem of coloring in the oblique direction is suppressed due to the symmetry,
Especially desirable. It is also possible to use a compensator whose optical axis is tilted from the vertical direction so that the rising direction of the liquid crystal molecules is taken into consideration. As a method for producing such a compensating plate, a film produced by stretching between rolls having different rotation speeds of rolls as disclosed in JP-A-6-222213 can be used.

By using the present invention as described above,
It is possible to obtain a liquid crystal display device with a wide viewing angle and high contrast that can be manufactured by a simple method similar to that of the conventional twisted nematic liquid crystal element.

[0111]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

(Embodiment 1) The size of one pixel is 100 μm
A substrate having an amorphous silicon thin film transistor array having a size of 300 μm, a pixel number of 480 × 640 × 3, and a diagonal size of the display screen of 240 mm was used.

After washing the two substrates 23 and 33, polyimide aligning agents JALS-428 (Nippon Synthetic Rubber) 21, 3 were used.
1 was applied by spin coating and baked at 90 ° C. and 220 ° C.

After that, rubbing treatment was performed with a buff cloth made of rayon.

The rubbing direction of each substrate is a diagonal direction of the substrates so that the rubbing direction becomes 90 ° when the substrates are laminated. An adhesive was applied to the peripheral portion of the substrate, and latex spheres having a diameter of 6 μm were scattered as spacers. Then, the positions were adjusted so that the pixel structures on both substrates were aligned, and the substrates were bonded together under pressure.

The bonded substrates were placed in a vacuum tank, and after vacuum evacuation, nematic liquid crystal (ZLI4792 manufactured by Merck).
11 were injected. The nematic liquid crystal was mixed with a chiral agent (S811) so that the natural pitch length was 70 μm. After the injection, the device was heated to 90 ° C. and then cooled to room temperature.

The produced liquid crystal element was observed with an optical microscope (polarized light). It was observed that, in each pixel, the uniform orientation when no voltage was applied was separated into two types of regions A and B when a voltage was applied. From the observation with the stage tilted, it was confirmed that the rising directions of the liquid crystal molecules were opposite in the two types of regions. The two regions were stable with no change over time.

After the polarizing plate was attached to the manufactured liquid crystal display device in crossed Nicols, the liquid crystal display device was installed on a rotary stage, and a color luminance meter (BM-5A manufactured by Topcon Corp.) was installed in front of it to check the viewing angle dependence of the liquid crystal display device. Examined. Eight gradations were displayed on the liquid crystal display screen, and the viewing angle dependence at each gradation display was measured. The luminance level relationship between gradations was not reversed in the range of a viewing angle of 40 ° or less.

An alignment film was similarly prepared on a substrate (30 mm × 40 mm) having no thin film transistor array, and the thickness was 50 μm.
A cell was prepared using m spacers, and the pretilt angle was measured by the crystal rotation method and found to be 0.05 °.

Example 2 As a compensator having negative refractive index anisotropy, a retardation film (VAC manufactured by Sumitomo Chemical Co., Ltd.) in which the minor axis of the refractive index ellipsoid of the compensator is perpendicular to the film surface.
-100) was used to study the effect of the compensator. In the liquid crystal display device manufactured under the same conditions as in Example 1, a compensating plate was attached between the liquid crystal cell and the polarizing plate. When visual angle-dependent control was measured using a color luminance meter, inversion of the luminance order between gradations did not occur within a visual angle of 40 °. Further, the contrast from the oblique direction was better than that of Example 1.

(Comparative Example 1) An element was prepared in the same manner as in Example 1 except that a general-purpose polyimide alignment film (AL1051 made by Japan Synthetic Rubber) was used. When observed under a polarizing microscope, only a uniform region was observed even when a voltage was applied.

When the viewing angle was measured by the same method as in Example 1, inversion of the luminance order between gradations occurred within a viewing angle of 10 °. The pretilt angle of this alignment film was 1.0 °.

Example 3 An element was prepared in the same manner as in Example 1 except that a polystyrene xylene solution was used as the alignment film and the firing temperature was 120 ° C. When observed under a polarizing microscope, two types of regions having different rising directions were observed when a voltage was applied and were stable.

When the viewing angle was measured by the same method as in Example 1, the order relation of luminance between gradations was not reversed within the range of viewing angle of 40 ° or less. The pretilt angle is 0.0
7 °.

(Embodiment 4) As a liquid crystal to be injected, ZLI
A device was produced in the same manner as in Example 1 except that a mixed solution of 4792, 4,4′-diacryloyloxybiphenyl acrylate (1 wt% with respect to liquid crystal) and benzoin methyl ether (1 wt% with respect to monomer) was used. did.
Further, after the injection hole was sealed, it was irradiated with ultraviolet light at room temperature.
The device remained transparent even after the irradiation with ultraviolet rays. When observed under a polarization microscope, two types of regions having different rising directions of liquid crystal molecules were observed in each pixel when a voltage was applied, and the boundary portion was stable immediately after the voltage was applied and was stable.

When the viewing angle was measured by the same method as in Example 1, the order of luminance between gradations was not reversed in the range of viewing angle of 40 ° or less.

Example 5 As the liquid crystal to be injected, ZLI was used.
An element was produced in the same manner as in Example 1 except that a mixed solution of KAYARAD PET-30 (manufactured by Nippon Kayaku) 0.2 wt% and Irganox 907 (1 wt% with respect to the monomer) was used for 4792. The obtained panel is used as a liquid crystal phase.
The mixture was heated to 100 ° C., which is higher than the phase transition temperature of the isotropic phase, and irradiated with ultraviolet rays (0.1 mW / cm ² ) in that state. afterwards,
The panel was cooled at 10 ° C./min while applying a voltage of 5V. Multiple regions were observed in each pixel. Polarization micrographs of one pixel of the obtained device are shown in FIGS. 15 and 16.

FIG. 15 shows a photograph when no voltage is applied. FIG.
No. 6 is an image observed by slightly tilting the panel when 3 V is applied, and different color tones show different alignment states. From the observation in the tilted state, it is confirmed that there are four minute regions having different rising directions of liquid crystal molecules. Immediately after the voltage was applied, there was a part where the same twisting direction and different rising directions contacted each other, but after a while, the boundary disappeared and the structure changed to a structure in which the same twisting direction and different rising directions touched only at points. .

When the viewing angle was measured by the same method as in Example 1, there was no reversal of the order of luminance among the gradations within the viewing angle of 50 °.

Also, a liquid crystal evaluation device (LCD-5000)
FIG. 14 shows the transmittance-voltage curve in the vertical direction of the substrate, which was measured in step 1. Almost the same characteristics as those of the TN device are obtained, and the applied voltage is 5
The contrast at V was greater than 200: 1.

Further, the viewing angle characteristics at the time of gradation display were measured at azimuth angles of 45 ° (FIGS. 17 to 19). Almost the same viewing angle characteristics were obtained in all directions, and halftone inversion was not obtained within 50 °.

The contrast of the obtained device (1 V / 5
V) is shown in FIG. 20 as a conoscopic image. It can be seen that the isocontrast curves are almost circular and have almost the same viewing angle characteristics in any direction.

Example 6 The panel produced in Example 5 was examined by changing the cooling rate (1 ° C./min to 20 ° C./min). The larger the cooling rate, the smaller the size of the micro area.

(Embodiment 7) The panel prepared in Embodiment 5 was changed to 2V, 3V, 5V, 10 while changing the applied voltage.
V) When cooled, the larger the voltage, the smaller the size of the minute region, and the structure of FIG. 3 was more likely to occur.

Example 8 A panel was produced in the same manner as in Example 5 except that the monomer content was changed from 0.1% to 1.0% (cooling rate 10 ° C./min). The larger the monomer content, the smaller the size of the micro area. Further, when the monomer content was 0.5 wt% or more, the rising direction of the liquid crystal molecules was regulated to one direction immediately after the voltage was applied, and the boundary portion of the regions having the same twist but different rising directions was not observed. Below 0.3 wt%, a boundary portion was observed which moved with time immediately after the voltage application.

(Embodiment 9) When the device obtained in Embodiment 5 is driven at a low level voltage of 1.6 V which is a voltage higher than the threshold voltage of liquid crystal molecules, the liquid crystal is driven immediately after the high level voltage is applied. The rising direction of the molecule was defined as one direction, and there was no decrease in contrast and no change in viewing angle characteristics over time. FIG. 21 shows the difference in response curve depending on the presence or absence of voltage application. In the case where the low level voltage is not applied, the transmittance changes slowly in the order of seconds, whereas in the case where the voltage of 1.6V is applied even at the low level, such a slow response is recognized. I can't.

(Comparative Example 2) A panel was prepared in the same manner as in Example 5 except that ultraviolet rays were applied at room temperature. Since the orientation of the liquid crystal at the time of ultraviolet irradiation is stored, it is difficult to control the size of the minute area.

(Embodiment 10) Room temperature, voltage application (10 V)
A panel was produced in the same manner as in Example 5 except that the ultraviolet ray was irradiated below. By varying the cooling rate and the applied voltage during cooling, panels with different sizes of minute regions were obtained.

(Example 11) A panel was prepared in the same manner as in Example 5 except that the conditions of UV irradiation and the content of the monomer were 0.5 wt%. UV irradiation (0.1mW / cm
² ) was irradiated for 3 minutes as the first step. As a result, the micro regions became stable, but the rising position of the liquid crystal molecules immediately after the voltage application was arbitrary, and it was confirmed that the boundary part of the "white" state was generated and moved. . As the second step, ultraviolet rays were irradiated for 60 minutes at room temperature. The resulting device had a fixed rise immediately after voltage application, and the viewing angle characteristics were almost the same in all directions.

A panel was prepared in exactly the same manner as in Example 2 using the TFT substrate and the color filter substrate on which the above alignment film was prepared. After cooling, it was confirmed that the same structure as in FIG. 24 was formed. When viewing angle characteristics are measured, viewing angle is 60 °
Within this range, the order of luminance was not reversed, and the contrast was 150: 1. The pretilt angle measured by the same method as in Example 1 was about 0 °.

(Example 12) "X" -type width 5 was applied to the entire surface electrode.
The alignment substrate 33 (FIG. 22) on which a number of μm openings are arranged.
(A): A part of the substrate is shown enlarged) and an oriented substrate 23 (FIG. 22 (b)) in which a large number of electrodes each having a size of 100 μm × 100 μm are arranged at intervals of 10 μm was used as the substrate. After washing these substrates, polyimide alignment agents JALS-428 (Japan Synthetic Rubber) 21, 31 were applied by spin coating and baked at 90 ° C and 220 ° C. Thereafter, a rubbing treatment was performed using a buff cloth made of rayon. The rubbing direction is a diagonal direction of the substrate, and the rubbing directions of the upper substrate and the lower substrate form an angle of 90 °. An adhesive was applied to the peripheral portion of the substrate, and latex spheres having a diameter of 6 μm were applied as spacers. Subsequently, the two substrates were bonded together while being pressed so that the electrode opening was located at the center of the electrode of 100 μm × 100 μm.

The bonded substrates were placed in a vacuum chamber, and after evacuation, a nematic liquid crystal (ZLI4792 manufactured by Merck,
Phase transition temperature: 92 ° C) UV curable monomer (KAYAR
ADPET-30 (Nippon Kayaku) 0.2 wt%), an initiator (Irganox 907, 5 wt with respect to the monomer)
%) Was injected. 1 panel obtained
Heat to 10 ° C, and at that temperature, UV (0.1 mW / cm
² ) was irradiated for 30 minutes. Then, the substrate was cooled at 20 ° C./min while applying a sinusoidal voltage of 8 V and 10 Hz. The polarization micrograph of the obtained cell is shown in FIG. FIG. 23 was taken with the cell tilted slightly and an intermediate voltage applied. 10
It can be seen that each section of 0 μm × 100 μm is divided into four minute regions according to the opening of the “x” shape. From the change in brightness when the cell was tilted, it was confirmed that the four minute regions were in the rising direction shown in FIG.
Further, a region having a different twist direction has entered the boundary region between the 100 μm × 100 μm section and the adjacent section, and no light leakage was observed at the boundary between the pixels when a sufficient voltage was applied. This is because the region A or the region B is thinly inserted between the region C of FIG. 4 (a) and the region D of the adjacent partition, so that the regions in which the liquid crystal has the same twisting direction and different rising directions are represented by lines. This is because the characteristic structure of the liquid crystal display device of the present invention, which is not in contact, is developed. Further, the rising direction of the liquid crystal immediately after the voltage application was the same as the rising direction of the liquid crystal after a sufficient time had passed, and no light leakage occurred. Furthermore, even if the voltage was turned on and off for a long time, the four minute regions did not disappear.

After the polarizing plate was attached to the prepared cell by crossed nicols, it was placed on a rotary stage and a color luminance meter (BM-5A made by Topcon Corp.) was placed in front of it to examine the viewing angle dependence of the liquid crystal display device. . Eight gradations were displayed on the liquid crystal display screen, and the viewing angle dependency at each gradation display was measured at intervals of an azimuth angle of 45 °. In all directions, the order relation of the luminance between the gradations was not reversed within the range of the viewing angle of 60 ° or less. Further, the contrast measured with a liquid crystal evaluation device (LCD-5000) at a voltage of 5 V applied in the substrate vertical direction is 2
00: 1 or more.

Embodiment 13 One pixel has a size of 100 μm.
A substrate having an amorphous silicon thin film transistor array (TFT) with m × 300 μm, the number of pixels of 480 × 640 × 3, and a diagonal size of the display screen of 240 mm was used. There is an RGB color filter on the upper substrate, the entire surface is an electrode (counter electrode), and there is no opening. On the other hand, there is a TFT on the lower substrate, and there are a gate line and a drain line in addition to the pixel electrode. After washing these substrates, a polyimide alignment agent JALS-428 (Japan Synthetic Rubber) was applied by spin coating and baked at 90 ° C and 220 ° C. afterwards,
Each substrate was rubbed with a buff cloth made of rayon. The rubbing direction of each substrate is a diagonal direction of the substrates such that the rubbing direction is 90 ° when the substrates are laminated. Adhesive is applied to the peripheral part of the substrate, and the spacer has a diameter of 6 μm.
Latex balls were sprayed. Then, the positions were adjusted so that the pixel structures on both substrates were aligned, and the substrates were bonded together under pressure.

A liquid crystal solution was injected in the same manner as in Example 1 except that the concentration of the UV monomer was 0.3 wt% with respect to the liquid crystal. The obtained panel was heated to 100 ° C. and irradiated with ultraviolet rays (0.2 mW / cm ² ) at that temperature for 60 minutes. Thereafter, while applying a pulse wave of 33 Hz, 15 V for 32 μs to the gate line and a rectangular wave of 33 Hz, 8 V for the drain line, the heater was removed and the mixture was allowed to cool to room temperature. FIG. 24 shows a state in which one pixel of the obtained liquid crystal display device is observed with a polarization microscope. Although each pixel is somewhat irregular, it is divided into four minute regions due to the non-uniform electric field between the counter electrode and the pixel electrode. From the same observation as in Example 1, the four minute regions are regions in which rising directions of liquid crystal molecules are different, regions having different twist directions are alternately present, and the same twist direction is obtained.
The two areas having the opposite rising directions were in contact only at points. Further, the rising direction of the liquid crystal immediately after the voltage application was the same as the rising direction of the liquid crystal after a sufficient time had passed, and no light leakage occurred. Furthermore, long-time voltage ON-OFF
Even if the above procedure was repeated, the four minute regions did not disappear.

When viewing angle characteristics and front contrast were measured in the same manner as in Example 12, the viewing angle was 60 ° in all directions.
There is no gradation inversion within 5% and the contrast at 5 V is 15
0: 1.

(Comparative Example 3) A liquid crystal display device was produced in the same manner as in Example 13 except that no voltage was applied during cooling. After cooling, four types of regions having different rising directions coexisted, but the four types of regions had a random shape regardless of the pixel shape. When a voltage was applied, there was a portion that rose in the expected direction at the end of the pixel, but no regularity was observed in the rising direction of the liquid crystal inside the pixel. Moreover, even after a sufficient time had passed after the voltage was applied, many boundary portions where light leakage occurred were observed. From the observation from the oblique viewing angle direction, it was confirmed that this boundary portion is a boundary portion between regions in which the liquid crystal has the same twist direction and different rising directions. Furthermore, it was observed that such a boundary portion moved immediately after the voltage was applied and slowly moved toward a stable place.

When the front contrast was measured in the same manner as in Example 12, it was 50: 1 even when a sufficient time had elapsed after the voltage application.

(Comparative Example 4) A liquid crystal display device was produced in the same manner as in Example 12 except that ultraviolet rays were irradiated at room temperature. Even after heating-cooling under voltage application, regions having different twist directions of the liquid crystal are scattered in some places, and as shown in FIG.
No microregions were found. The structure in which the regions of the liquid crystal having different twist directions are scattered is expected to be because the state at room temperature such as ultraviolet irradiation is stored. When the viewing angle characteristics were measured by the same method as in Example 12, a viewing angle of 10
There was a direction in which gradation inversion occurred at °.

(Example 14) Two kinds of alignment films (TAL10 manufactured by Hoechst Co., Ltd.) were used as a low-pretilt polyimide alignment film.
07 and K104 manufactured by Toray Industries, Inc. treated with ethyl lactate) were used, and an element was manufactured in the same manner as in Example 12 except that the monomer concentration was 0.5 wt%. Similar to the twelfth embodiment, four minute regions were developed, and the viewing angle characteristics similar to those of the twelfth embodiment were obtained. When the pretilt angle is measured, TAL1007 and K104 are 0.35 respectively.
° and 0.5 °.

(Comparative Example 5) An element was prepared in the same manner as in Example 12 except that a general-purpose polyimide alignment film (AL1051 manufactured by Japan Synthetic Rubber) was used. When observed under a polarizing microscope, a plurality of regions were generated immediately after the voltage was applied, but then disappeared and only a uniform region was observed.

When the viewing angle was measured by the same method as in Example 12, there was a direction in which the luminance order was reversed between gradations within the viewing angle of 10 °. The pretilt angle of this alignment film is 1.
0 °.

Example 15 A liquid crystal panel manufactured in the same manner as in Example 13 has an ultraviolet monomer concentration of 1.0 wt%.
A liquid crystal solution similar to that in Example 12 was injected except that the above-mentioned conditions were satisfied.
The obtained panel was heated to 100 ° C. and irradiated with ultraviolet rays (0.2 mW / cm ² ) at that temperature for 5 minutes. After that, the heater was removed and the mixture was allowed to cool to room temperature while applying a pulse wave of 33 Hz, 15 V of 32 μs to the gate line and the drain line of 33 Hz, 10 V to Example 1 and the drain line. In this state, the structure shown in FIG. 24 was recognized in each pixel. Then, it was irradiated with ultraviolet rays (0.1 mW / cm ² ) at room temperature for 120 minutes. The obtained liquid crystal display device had the same viewing angle characteristics as in Example 13. Further, this liquid crystal display device is
After heating to 0 ° C. and holding for 10 minutes, it was cooled with no voltage applied. After cooling, observation with a polarization microscope revealed the structure shown in FIG. 24 as before heating.

(Example 16) A device was prepared in the same manner as in Example 12 except that a polystyrene xylene solution was used as the orientation film and the firing temperature was 120 ° C. When observed under a polarizing microscope, four seed regions having different rising directions were observed when a voltage was applied and were stable.

When the viewing angle was measured by the same method as in Example 12, the order of luminance among the gradations was not reversed in the range of the viewing angle of 60 ° or less. Further, the pretilt angle is set to 0.1.
07 °.

(Embodiment 17) As a liquid crystal to be injected, ZL
A device similar to Example 12 except that a mixed solution of I4792, 4,4′-diacryloyloxybiphenyl acrylate (0.3 wt% with respect to liquid crystal) and benzoin methyl ether (1 wt% with respect to monomer) was used. Was produced.

When the viewing angle was measured by the same method as in Example 12, the order of luminance intensities between gradations was not reversed within the viewing angle range of 60 °.

(Embodiment 18) The concentrations of the UV monomer are 0 wt%, 0.01 wt%, 0.02 wt%,
Example 1 except that 0.05 wt% and 0.1 wt% were used.
A liquid crystal cell was prepared in the same manner as in No. 2. The structure similar to that shown in FIG. 23 was generated in all cells. However, when the voltage is turned on and off repeatedly, the UV monomer concentration becomes 0w.
In the t% and 0.01 wt% liquid crystal cells, a part where four minute regions disappear was observed.

Example 19 A liquid crystal cell was produced in the same manner as in Example 12 except that the concentration of the UV monomer was 2 wt%, 4 wt%, and 10 wt%, and the UV irradiation time was 5 minutes. In a cell having a monomer concentration of 2 wt% and 4 wt%, a structure similar to that shown in FIG. 23 was generated.
In the cell having a monomer concentration of 10 wt%, the liquid crystal orientation was disturbed, and many regions where the liquid crystal was not twisted by 90 ° were observed, and the white state was not obtained even when no voltage was applied.

(Example 20) In the same manner as in Example 12,
Only the alignment film was changed to a 1/1 mixed solution (2 wt%) of chlorobenzene / methylene chloride of polyvinyl cinnamate manufactured by Aldrich, the baking temperature was set to 90 ° C., and linearly polarized ultraviolet light was irradiated instead of rubbing. The direction of linearly polarized light was the same as that of rubbing. A liquid crystal panel was produced in the same manner as in Example 1. A structure similar to that shown in FIG. 23 was observed, the order was not reversed within the range of a viewing angle of 60 °, and the contrast was 200: 1.

When the pretilt angle in the direction perpendicular to the polarization direction of the linearly polarized light was measured by the crystal rotation method, it was about 0 °.

(Example 21) In the same manner as in Example 20,
After coating polyvinyl cinnamate and exposing it to linearly polarized light, 1 wt% of a photopolymerization initiator (Irgacure65
1,4-di- (4- (6-acryl)
oyloxyhexyloxy) benzoloxy)
Benzene was applied, and while being heated to 50 ° C., it was irradiated with ultraviolet light and returned to room temperature. As a result, in the nematic liquid crystal phase, the state of the alignment was fixed on the substrate surface. This can be confirmed by observing with a polarizing microscope in which exactly the same treatment was performed using a test glass substrate.

[0163]

As described above, the present invention provides a liquid crystal display device having a wide viewing angle and high contrast which can be manufactured by the same simple method as the conventional twisted nematic liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is an enlarged perspective view of a liquid crystal layer of a liquid crystal display device of the present invention.

FIG. 2 is a sectional view showing a liquid crystal display device of the present invention.

FIG. 3 is an enlarged view of a liquid crystal layer of the liquid crystal display device of the present invention when viewed from a direction perpendicular to a substrate.

FIG. 4 is an enlarged top view of a liquid crystal layer of the liquid crystal display device of the present invention.

FIG. 5 is a cross-sectional view showing a liquid crystal display device of the present invention.

FIG. 6 is a sectional view of the liquid crystal display device showing a splay arrangement.

FIG. 7 is a diagram showing a relationship between a rubbing direction and a spray arrangement.

FIG. 8 is an enlarged top view of a liquid crystal layer of the liquid crystal display device of the present invention.

FIG. 9 is a cross-sectional view showing a liquid crystal display device of the present invention.

FIG. 10 is a diagram showing the behavior of liquid crystal molecules at the boundary between regions where the liquid crystal twist direction is the same and the rising directions of the liquid crystal molecules are different. (A) When voltage is not applied (b) When voltage is applied

FIG. 11 is a diagram showing a behavior of liquid crystal molecules at a boundary portion of regions where liquid crystal molecules have opposite twist directions and liquid crystal molecules have different rising directions. (A) When voltage is not applied (b) When voltage is applied

FIG. 12 is a cross-sectional view showing a liquid crystal display device of the present invention including a polymer.

FIG. 13 is a diagram of waveforms used in a method for driving a liquid crystal display device of the present invention. (A) Present invention (b) Prior art

FIG. 14 is a transmittance-voltage curve of the liquid crystal display device of the present invention.

FIG. 15 is a polarization microscope photograph of one pixel of the liquid crystal display device of the present invention.

FIG. 16 is a polarization microscope photograph of one pixel of the liquid crystal display device of the present invention (tilted).

FIG. 17 is a diagram showing viewing angle characteristics of the liquid crystal display device of the present invention.

FIG. 18 is a diagram showing viewing angle characteristics of the liquid crystal display device of the present invention.

FIG. 19 is a diagram showing viewing angle characteristics of the liquid crystal display device of the present invention.

FIG. 20 is a diagram showing the contrast of the liquid crystal display device of the present invention.

FIG. 21 is a diagram of a response curve when a voltage higher than a threshold voltage is applied at a low level.

FIG. 22 is a diagram showing an electrode shape of a substrate used in Example 1.

FIG. 23 is a polarization microscope photograph of the liquid crystal display device of the present invention.

FIG. 24 is an enlarged view of one pixel of the liquid crystal display device of the present invention obtained in Example 2.

FIG. 25 is a sectional view of a conventional liquid crystal display device (with no voltage applied).

FIG. 26 is a cross-sectional view for explaining a problem of a conventional liquid crystal display device (voltage application).

FIG. 27 is a perspective view of a conventional liquid crystal display device.

FIG. 28 is a top view of a conventional liquid crystal display device.

FIG. 29 is a cross-sectional view of a conventional liquid crystal display device.

FIG. 30 is a diagram showing a conventional liquid crystal display device.

FIG. 31 is a diagram showing a problem of a conventional liquid crystal display device.

[Explanation of symbols]

 11 Liquid crystal molecule 12 Polymer 13 Pretilt angle 21, 31 Alignment film 22, 32 Transparent electrode 23, 3 Glass substrate 34 Rubbing direction 35 Electrode opening 41, 42 Light rays A, B, C, D Minute regions with different alignment aa ', Bb' Substrate rubbing direction

Claims (20)

[Claims] 1. In a liquid crystal display device in which a liquid crystal layer made of a nematic liquid crystal is sandwiched between two substrates, two kinds of irregular minute regions having different rising directions of liquid crystal molecules coexist in the liquid crystal layer. Liquid crystal display device characterized by. 2. A liquid crystal display device in which a liquid crystal layer made of a nematic liquid crystal is sandwiched between two substrates, and in the liquid crystal layer, minute regions having different twist directions of liquid crystal alignment vectors and different rising directions of liquid crystal molecules are provided. A liquid crystal display device characterized by coexistence with a minute region. 3. The liquid crystal layer has a total of four types of micro regions, that is, micro regions having different twisting directions of liquid crystal alignment vectors and micro regions having different rising directions of liquid crystal molecules. Liquid crystal display device. 4. A micro-region having a different orientation vector twisting direction of a liquid crystal and a micro-region having different rising directions of liquid crystal molecules.
4. The liquid crystal display device according to claim 2, wherein the two minute regions coexist in one pixel of the liquid crystal layer. 5. The liquid crystal display device according to claim 2, wherein said minute area has an irregular shape. 6. The liquid crystal display device according to claim 1, wherein the surfaces of the two substrates are each subjected to an alignment treatment in one direction. 7. The liquid crystal device according to claim 1, wherein the liquid crystal molecules have the same torsion direction of the alignment vector, and each of the regions having different rising directions of the liquid crystal molecules is not in contact with a line on a virtual plane crossing the liquid crystal layer. The liquid crystal display device according to claim 1. 8. An alignment film for aligning liquid crystal molecules on at least one of the two substrates, wherein a pretilt angle of the alignment film is 0.5 ° or less. The liquid crystal display device according to claim 1. 9. An alignment film for aligning liquid crystal molecules on at least one of the two substrates, wherein the alignment film has a property of aligning the liquid crystal molecules in a direction perpendicular to the rubbing direction. The liquid crystal display device according to any one of claims 1 to 8, wherein: 10. The liquid crystal display device according to claim 1, wherein the liquid crystal layer contains a chiral agent having a twist direction in which the liquid crystal has a splay arrangement. 11. A region in which the electrodes on the two substrates have different shapes or at least one of the electrodes on the substrate has an opening and an uneven electric field is generated between the two substrates. 2. The method according to claim 1, wherein:
0. The liquid crystal display device according to any one of 0. 12. The liquid crystal display device according to claim 1, wherein a small amount of a polymer is present in the liquid crystal layer. 13. The liquid crystal display device according to claim 12, wherein the amount of the polymer present in the liquid crystal layer is 0.02% by weight or more and 4% by weight or less. 14. A liquid crystal according to claim 1, wherein a compensator having a negative refractive index anisotropy is disposed on one or both sides of said two substrates. Display device. 15. A combination in which two kinds of minute regions having different rising directions of liquid crystal molecules or a minute region having different twisting directions of liquid crystal orientation vectors and four kinds of minute regions having different rising directions of liquid crystal molecules are formed. A liquid crystal or a liquid crystal solution containing a small amount of a monomer or an oligomer is injected between the two substrates, and then, under a voltage application, a temperature from a temperature equal to or higher than the liquid crystal phase-isotropic phase transition temperature to a temperature lower than the phase transition temperature. Liquid crystal characterized by cooling the liquid crystal layer to generate two types of micro regions having different rising directions of liquid crystal molecules or four types of regions having different twist directions of liquid crystal alignment vectors and different rising directions of liquid crystal molecules. A method for manufacturing a display device. 16. A combination of two types of minute regions having different rising directions of liquid crystal molecules, or a plurality of minute regions having different twisting directions of liquid crystal orientation vectors and four types of minute regions in the rising direction of liquid crystal molecules. A method of injecting a liquid crystal solution containing a small amount of a monomer or an oligomer between the two substrates, and thereafter reacting the monomer or the oligomer to form a polymer. 17. The liquid crystal display device according to claim 15, wherein said monomer or oligomer is reacted at a temperature not lower than the liquid crystal phase-isotropic phase transition temperature of liquid crystal to produce a polymer. Production method. 18. The method according to claim 15, wherein said monomer or oligomer is reacted under voltage application to form a polymer.
18. The method for manufacturing a liquid crystal display device according to claim 17. 19. The method for manufacturing a liquid crystal display device according to claim 15, wherein said monomer or oligomer is reacted at least twice. 20. A method of driving a liquid crystal display device in which minute regions having different rising directions of liquid crystal molecules coexist when a voltage is applied, wherein a voltage equal to or higher than a threshold voltage of the liquid crystal molecules is applied even when a low level voltage is applied. A method for driving a liquid crystal display device, comprising: