JPH08122784A - Liquid crystal display element - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display element in which dependence on the visual angle is decreased while characteristics of a TN mode liquid crystal are maintained so that good contrast can be obtd. at any visual angles. CONSTITUTION: This liquid crystal display element consists of a pair of substrates 21, 22 disposed at a specified distance, oriented films 28, 29 formed on the surfaces of the substrates facing to each other, and a liquid crystal material held between these substrates. In this liquid crystal display element, the liquid crystal material shows both of dextrorotatory and levorotatory and the pretilt angle of the oriented films 28, 29 is controlled to <2 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique of a liquid crystal display device having a wide viewing angle, and more particularly to a liquid crystal display device using an alignment film, a liquid crystal material and a spacer capable of exhibiting a wide viewing angle.

[0002]

2. Description of the Related Art A thin film transistor drive type liquid crystal element is
It is widely known as a thin display that can obtain high image quality such as high response speed and full-color display, but this type of liquid crystal element generally has a problem of a narrow viewing angle. Conventionally, as a technique for widening the viewing angle of this type of liquid crystal element, an alignment division technique for each pixel is known. The alignment division structure refers to a structure in which each of R, G, and B dots forming a pixel has a region in which liquid crystal molecules rise in different directions when a voltage is applied, and this type of structure is usually a dot. Is divided into two, and each has a different orientation treatment. With this alignment division technology, a sharp and asymmetrical change in contrast in the vertical direction, which has been a problem in a thin film transistor drive type liquid crystal element, is alleviated and made symmetrical, and grayscale inversion does not occur in the halftone. It is possible to obtain the effect of enlarging the liquid crystal display device, which has created the possibility of providing a liquid crystal device with a wide viewing angle.

Here, as an example of a conventional method of manufacturing a liquid crystal device having the above-mentioned alignment division structure, an alignment film preparation layer 2 is formed on the upper surface of a substrate 1 as shown in FIG. 2 is subjected to a first rubbing treatment as shown in FIG. 9B, and then a photoresist 3 is applied thereon as shown in FIG. 9C, and a resist pattern is formed as shown in FIG. 9D. 9B. Further, as shown in FIG. 9E, a second rubbing treatment is performed from the top of the resist 3 in the direction opposite to the first rubbing treatment, and then as shown in FIG. 9F. A method is known in which the substrate 1 with the alignment film 5 can be obtained by removing the resist 3. In addition,
The rubbing treatment is carried out by rubbing the roller 6 having a rubbing cloth attached to the outer peripheral portion onto the alignment film preparation layer 2 or the like.

Further, as a structural example of a liquid crystal element using the alignment film 5 of this structure, as shown in FIG. 9 (g), the substrate 1 on the color filter side and the alignment film 5 and the substrate on the thin film transistor side facing them are shown. 1'and the alignment film 5'have a structure in which liquid crystal molecules 7 ... Are enclosed, and by controlling the alignment of the alignment films 5 and 5 ', liquid crystal molecules on the alignment film 5 side on the color filter side. There is known a liquid crystal element in which a pretilt angle is set such that the liquid crystal molecules on the thin film transistor side and the alignment film 5 ′ side are parallel to each other.

However, in the conventional method as described above, the entire surface rubbing process is performed once, and then the second rubbing process through the resist 3 is used to perform rubbing in the opposite direction using the openings of half the fine dots. You have to do
Moreover, it is necessary to use a mask having a large area, but such a rubbing process has a problem that it is difficult to realize industrially. In addition, when the photoresist is applied to the rubbing surface and developed, the alignment film is dissolved by the alkaline component of the developer and a part of the surface is altered until it disappears, and a stable alignment state cannot be realized by the rubbing treatment. There's a problem. In addition, since it is necessary to remove the remaining photoresist after that, the alignment film is more likely to be damaged,
There is a problem that the initial rubbing state cannot be maintained, and stable alignment division over a wide area is difficult.

Therefore, in recent years, there has been provided a method which can be industrially realized by eliminating the drawbacks of the conventional method.
In that method, as shown in FIG. 10A, a low pretilt alignment film 11 made of an inorganic material is formed on a substrate 10, and a high pretilt alignment film 12 is laminated thereon as shown in FIG. 10B. Then, a photoresist 13 is further laminated as shown in FIG. 10C, and then developed as shown in FIG. 10D to etch the high pretilt alignment film 12, and subsequently, as shown in FIG.
As shown in 0 (e), a rubbing process is performed using the roller 16 to manufacture the alignment film 15. According to this method, the rubbing treatment is performed only once, and since the rubbing treatment of the high pretilt angle alignment film 16 is performed after the resist is peeled off, the alignment state can be stabilized, and the first low pretilt angle alignment film can be used as the inorganic alignment film. With the above, it is possible to obtain a stable alignment film by eliminating the influence of the photoresist on the developing solution.

Further, as a structural example of a liquid crystal element using the alignment film 15 of this structure, as shown in FIG. 10F, the substrate 10 on the color filter side, the low pretilt angle alignment film 11, and the high pretilt angle alignment film. 12, and a structure in which liquid crystal molecules 17 ... Are enclosed between the thin film transistor side substrate 10 ′, the low pretilt angle alignment film 11 ′, and the high pretilt angle alignment film 12 ′ that are provided so as to face them. Therefore, the low pretilt angle alignment films 11 and 11 'and the high pretilt angle alignment film 1
A liquid crystal element is known in which the pretilt angle of the liquid crystal molecule on the alignment film side of the color filter side and the pretilt angle of the liquid crystal molecule on the alignment film side of the thin film transistor side are set to be different by controlling the alignment of 2 and 12 ′. There is.

[0008]

However, even in the method of manufacturing a liquid crystal element having this structure, a photolithography step is still required, and the steps tend to be complicated, the productivity tends to be poor, and the cost tends to increase. is there. Also,
Residues in the photolithography process are likely to be generated, and residues may be generated on the alignment film, which may reduce the product yield.
Further, the rubbing step is a kind of dusting step because it is a step of rubbing the alignment film preparation layer with a rubbing cloth, and a clean room step such as photolithographic masking is mixed on the rubbing step. However, there is a problem that the management becomes complicated and it becomes difficult to maintain high quality.

Further, as shown in FIG. 9, a resist 3 is formed after the first rubbing, a window is formed in the resist 3 by patterning, and a part of the rubbing alignment film 2 is protected. In the conventional method in which the second rubbing is performed from above the window and the rubbing in another alignment direction is partially performed, the area in the window opened in the resist 3 is
Since it is to be rubbed once, it is impossible to rub the window of the resist 3 with high precision.
The size of pixels that can be handled by this method is limited to about 100 μm square.

Further, in a liquid crystal element in which the combination of the rubbing direction of the alignment film on the color filter side and the rubbing direction of the alignment film on the thin film transistor side is set to be different for each pixel of each thin film transistor, one alignment film is provided. The substrate with the other alignment film and the other substrate with the alignment film are positioned accurately without causing an error in the size of the pixel unit and then bonded, and the liquid crystal is sealed between them. However, if it decreases, there is a problem that the desired liquid crystal alignment cannot be obtained.

On the other hand, as one structural example of the liquid crystal device in which the rubbing direction of the alignment film on the color filter side and the rubbing direction of the alignment film on the thin film transistor side are set differently, the rubbing direction of the alignment film is as shown in FIG. There is known a liquid crystal element having a structure in which, when viewed two-dimensionally, the directions are orthogonal to each other as shown by the arrow A and arrow B directions. However, the liquid crystal element having this structure has a viewing angle characteristic as shown in FIG. 12, and there is a problem that the viewing angle is significantly narrowed in a specific direction. The viewing angle characteristic shown in FIG. 12 has CR ≧ 10.
Shows the area. Here, CR means contrast and is defined by the following equation in a normally white (white display when no voltage is applied, black display when voltage is applied) type liquid crystal element. CR = (Transmittance when voltage is not applied) / (Transmittance when voltage is applied) Note that the reverse is true for normally black (black display when no voltage is applied, white display when voltage is applied) type liquid crystal element. It is defined by the following formula. CR = (transmittance when voltage is applied) / (transmittance when voltage is not applied)

Further, in the liquid crystal device having the above-described structure in which the directions are orthogonal to each other as shown by the arrow A direction and the arrow B direction, it is known that the liquid crystal molecules rotate 90 ° between the upper and lower substrates. Although TN liquid crystal (twisted nematic liquid crystal) is used, the viewing angle dependency as shown in FIG. 12 is caused by the twist angle of the TN liquid crystal being 90 °. Therefore, the twist angle of this liquid crystal is 9
If the angle is changed to 0 ° or more, for example 180 °, the problem of viewing angle as shown in FIG. 12 can be avoided, but the twist angle is set to 1
If it is set to 80 °, the liquid crystal becomes the STN mode (super twisted nematic mode) instead of the TN mode, which causes another problem, for example, the display is colored or the response is slow. It is desired to improve the viewing angle dependency while still utilizing the above.

The present invention has been made in view of the above circumstances, and while maintaining the characteristics of the TN mode liquid crystal, the viewing angle dependency is reduced so that good contrast can be obtained from any angle. An object is to provide a liquid crystal display device.

[0014]

According to a first aspect of the present invention, in order to solve the above-mentioned problems, an alignment film is formed on the facing surfaces of a pair of substrates arranged facing each other with a certain distance. A liquid crystal display element in which a liquid crystal material is held in the space, and the liquid crystal material is a liquid crystal material capable of exhibiting both right-handedness and left-handedness, and the pretilt angle of the alignment film is smaller than 2 °. It has been done.

In order to solve the above-mentioned problems, in the invention according to claim 2, the right-handedness and left-handedness of the liquid crystal material are not added with a chiral agent, or a right-handed chiral agent and a left-handed chiral agent are added to the liquid crystal material. This is realized by adding an equal amount of the agent, and the liquid crystal material is a twisted nematic liquid crystal.

In order to solve the above problems, the invention according to claim 3 has a pretilt angle of 0.5 according to claim 1 or 2.
It is made smaller than °.

According to a fourth aspect of the present invention, in order to solve the above problems, the surface of the alignment film according to the first, second or third aspect is provided with a convex portion having a height which is at least half the distance between the substrates. At least one of the recesses having a depth equal to or more than half the distance between the substrates,
A plurality is formed. Furthermore, in order to solve the above-mentioned problems, the invention according to claim 5 has 100 to 900 protrusions or recesses according to claim 4 on the surface of the alignment film / mm ^2.
It is formed at a ratio of.

According to a sixth aspect of the present invention, in order to solve the above-mentioned problems, the convex portions according to the fourth or fifth aspect are formed by spacers inserted between the substrates in order to keep the distance between the substrates constant. is there.

[0019]

According to the first aspect of the invention, the pretilt angle of the alignment film in contact with the liquid crystal material having both right-handedness and left-handedness is set to 2 ° or less, so that the right-handedness and left-handedness of the liquid crystal molecules are increased. As a result, the innumerable liquid crystal molecules present in the liquid crystal material can randomly exhibit right-handedness and left-handedness. Since the left-handed ones are randomly present, the twist angle of the liquid crystal molecules is apparently enlarged to 180 °. However, since the liquid crystal material itself is twisted nematic liquid crystal (TN liquid crystal), it has the advantages of TN liquid crystal. Therefore, the viewing angle dependency is improved while maintaining the TN mode.

In order to make the liquid crystal molecule exhibit both right-handedness and left-handedness, it is necessary to add no chiral agent to the liquid crystal material,
Even when added, it is exhibited when the right chiral agent and the left chiral agent are added in equal amounts so as to have the same effect. If the pretilt angle of the alignment film is 0.5 ° or less, the right-handedness and left-handedness of the liquid crystal molecules can be realized very smoothly.

The right-handedness and the left-handedness of the innumerable liquid crystal molecules in the liquid crystal material are randomly generated, but the right-handedness and the left-handedness cannot be completely controlled as they are, and therefore a large number of convex portions or concave portions are formed on the surface of the alignment film. Then, with these as the core, both dextrorotatory and levorotatory are surely generated. When 100 to 900 pieces / mm ^{2 of the} convex portions or concave portions are present on the alignment film, it means that right-handedness or left-handedness corresponding to these numbers occurs in the entire display element, and multi-domain is formed, A uniform display is possible. As a specific example of the above-mentioned convex portion or concave portion, a spacer can be used for defining the space between a pair of substrates arranged to face each other. As a result, it is possible to introduce dextrorotatory and levorotatory nuclei by using spacers that are indispensable for liquid crystal display devices, without the need to separately provide convex portions or concave portions on the alignment film, and to realize multi-domain formation. Will be realized.

Hereinafter, the present invention will be described in more detail. FIG.
Shows an embodiment of a liquid crystal display device to which the present invention is applied. A liquid crystal display device 20 of this example includes a pair of substrates 21 and 22 vertically opposed to each other with a certain space, and an upper part. A polarizing plate 23 provided on the upper surface side of the substrate 21, a polarizing plate 24 provided on the lower surface side of the lower substrate 22,
22 is mainly composed of electrodes (not shown) for driving the liquid crystal formed on the inner surface sides of the 22 facing each other. A sealing material 26 is attached to the peripheral portions of the upper and lower substrates 21 and 22 to seal the gap between the upper and lower substrates 21 and 22, and a TN (twisted nematic) type liquid crystal material is sealed in this gap. At the same time, a large number of spacers 27 are dispersed between the upper and lower substrates 21 and 22, and the gap between the upper and lower substrates 21 and 22 is held at a predetermined width by the spacer 27.
Furthermore, an alignment film 28 is formed on the lower electrode of the upper substrate 21, and an alignment film 29 is formed on the upper electrode of the lower substrate 22. The electrodes formed on the inner surface of the substrate 21 or 22 may be matrix electrode wiring, or may be pixel electrodes or common electrodes provided in a TFT circuit using thin film transistors, but in FIG. Therefore, the electrodes and the alignment film are omitted.

Further, the surfaces of the alignment films 28 and 29 are subjected to a rubbing treatment, and the substrates 21 and 22 of these films are processed.
The rubbing direction is the same as the rubbing direction described with reference to FIG. 11, that is, the rubbing direction of the alignment film 28 of the upper substrate 21 is diagonally right upward when the substrate 21 is viewed in plan, and the lower substrate is The rubbing directions of the alignment films 29 of 22 are respectively directed obliquely downward right when the substrate 22 is viewed in a plan view, and the rubbing directions of the upper and lower alignment films 28 and 29 are 9
It has a twisted relationship of 0 °. The pretilt angle θ _p defined when the liquid crystal molecules are in contact with the surface of the alignment film is 2 ° or less, preferably 0.5 ° or less in at least one of the alignment films. In this embodiment, the most preferable pretilt angle θ _p is 0 because the liquid crystal molecules need to exhibit both right-handedness and left-handedness.

Next, the liquid crystal material filled in the gap between the substrates 21 and 22 is a liquid crystal material which does not contain a chiral agent which causes liquid crystal molecules to exhibit dextrorotatory or levorotatory properties. In addition, in a normal TN type liquid crystal material,
Although the chiral agent is always added, the TN type liquid crystal material used in this example is one to which the chiral agent is not added. In this example, a liquid crystal material to which a chiral agent is not added is used, but a right chiral agent that exhibits dextrorotatory property and a left chiral agent that exhibits levorotatory property are added with the same effect, for example, in equal amounts. A liquid crystal material may be used. According to the above, the liquid crystal molecules E of the liquid crystal material used in this embodiment have the property of easily turning to the right or left.

Not adding the chiral agent is equivalent to making the twist pitch of the liquid crystal molecules infinite. That is, when a chiral agent is added to nematic liquid crystal,
Depending on the type of chiral agent, the liquid crystal molecules will be twisted to the right or left. At this time, the distance required to make one twist is called a pitch. Therefore, infinite pitch means
It means that the distance twisted by one rotation is infinite, that is, it is not twisted. Therefore, in the present invention, the pitch is preferably infinite, but in an ordinary liquid crystal device, if the pitch is 20 times or more the cell gap, it can be regarded as a pitch close to infinity.

Although the size of the spacer 27 is exaggerated in the drawing, it is actually several μm, and it is 100 to 900 pieces / mm ² , preferably 800 pieces / mm ^2. It is uniformly dispersed between the substrates 21 and 22 at a ratio of about mm ² . In the conventional liquid crystal display element, the spacers are provided at about 100 to 150 pieces / mm ^2, but in the present invention, the number of spacers 27 is more preferably about 800 pieces / mm ² . The spacers 27 are arranged in the above-mentioned number so that the spacers 27 are provided on the liquid crystal molecules E around the spacers 27.
This is because it is easy to create the two states of dextrorotatory and levorotatory with the nucleus as the core. By arranging such a number of spacers 27, a large number of domains can be formed in the liquid crystal molecules existing between the substrates 21 and 22, and a multi-domain can be realized. Therefore, the spacer 27, which is an essential component of the liquid crystal display element, does not need to be provided with a convex portion or a concave portion separately on the alignment film.
・ By effectively utilizing, the dextrorotatory and levorotatory nuclei can be introduced to realize multidomain.

In the liquid crystal element 20 configured as described above, the alignment film 29 of the lower substrate 21 is formed when no electric field is applied.
The liquid crystal molecules E are aligned in the rubbing direction formed in the above, and the liquid crystal molecules E on the upper side are gradually twisted and aligned in the rubbing direction of the alignment film 28 of the upper substrate 22. As shown in FIG. 2, the substrates 21 and 22 are twisted by 90 ° and oriented. Next, when an electric field is applied to the electrodes and an electric field is applied, the liquid crystal molecules E are oriented along the direction of the electric field due to their dielectric properties, and the array state shown in FIG. Here, when the polarization axes of the upper and lower polarizing plates 23 and 24 are deviated from each other by 90 °, light is transmitted in the state shown in FIG. 2 and normally white display in which light is not transmitted in the state shown in FIG. Become. On the other hand, if the polarization axes of the upper and lower polarizing plates 23 and 24 are set to be parallel, a normally black display, which is the opposite display, is obtained.

In the liquid crystal display element 20 having the above structure,
At least one of the substrates has a small pretilt angle of 2 ° or less in the alignment film and does not contain a chiral agent.
Since the liquid crystal material itself is capable of exhibiting both right-handedness and left-handedness, each liquid crystal molecule E of the liquid-crystal material is randomly or individually provided with right-handedness and left-handedness in a certain region or domain. It will come to exert. From this, the viewing angle dependence shown in FIG. 12 caused by the 90 ° twist of all the liquid crystal molecules E in the same direction is eliminated, and a wider viewing angle dependence can be obtained.

That is, looking at the viewing angle dependence of the upper and lower rows of liquid crystal molecules E as shown in FIG. 12, the viewing angle dependence is shown as shown in FIG. Or, the other upper and lower rows of liquid crystal molecules existing at distant places may show the gyration opposite to that of FIG. 2 (that is, the gyration of 90 ° twist is the same, but the twist direction is different). Therefore, the viewing angle dependence of the liquid crystal molecules having the opposite gyration has a shape close to the shape obtained by rotating the isocontrast curve of FIG. 12 by 90 ° around the central axis of the viewing field. That is, instead of the curved line having an upward concave as shown in FIG. 12, for example, the curved line having a concave left side. Since domains having such different viewing angle dependences are randomly present, the liquid crystal display element 20 as a whole has a viewing angle dependence as shown in FIG. 8, for example. Become. Therefore, the portion of the isocontrast curve where the viewing angle is significantly reduced is smaller than that in the conventional example shown in FIG.

Next, in the structure of this embodiment, the spacer 27
Since many are arranged at 100 pieces / mm ² or more,
It is possible to generate both right-handedness and left-handedness with respect to the liquid crystal molecule E by using these spacers 27 as cores, so that it is possible to surely form a large number of domains having different viewing angle dependences. , It is possible to surely realize multi-domain. That is, the spacer 27 ...
Since a state in which both right-handedness and left-handedness are likely to occur is created around it, multidomainization is automatically ensured.
On the other hand, in the entire display area of the substrate 21, there are several areas in which liquid crystals exhibiting dextrorotation are present and areas in which liquid crystals exhibit levorotation are present, which are large enough to be visually recognized. If it exists, part of it is shown in FIG.
Shows the iso-contrast curve and the other parts show the iso-contrast curve obtained by rotating the iso-contrast curve shown in FIG. 12 by 90 °, so that the area where unevenness appears when viewed from a certain angle is displayed. It is not preferable because it becomes noticeable in the area.

By the way, in the above-mentioned embodiment, the spacer 27 is used as the nucleus for expressing the dextrorotatory or levorotatory direction of the liquid crystal molecule E. However, these nuclei can be the substrate 21,
It may be a convex portion having a half of the interval between the two or a concave portion having a half depth. Therefore, it is possible to use the same number of spacers 27 as the conventional one and form a plurality of convex portions and concave portions on the alignment film to make these nuclei expressing dextrorotatory or nucleating levorotatory.

[0032]

【Example】

"Example 1" The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto. As the TN liquid crystal to which the chiral agent was not added, trade name AP-5019 manufactured by Chisso Corporation was used. The alignment film formed on the glass substrate has a silane coupling agent SH6020 (manufactured by Torre Silicone: product name) on one substrate.
A thin film of Optomer AL-1051 (manufactured by Japan Synthetic Rubber: trade name) was formed on the other substrate. Then, the substrate was held on a stage and a rubbing roll was rubbed on the substrate to perform a rubbing process.

The rubbing direction of the alignment film on the upper substrate is shown in FIG.
8 and the rubbing direction of the alignment film on the lower substrate was applied in the direction of the arrow indicated by the chain line in FIG. The rubbing process uses a rubbing roll in which a rayon cloth having a thickness of 1.6 mm is wrapped around a roll, and the pushing amount is 0.4 mm.
The rotation speed of the rubbing roll was set to 150 rpm, and the moving speed on the stage side holding the substrate was set to 10 mm / sec.

Next, as a spacer to be sandwiched between the glass substrates, Sekisui Fine Chemical's trade name Microbar having a particle size of 5.0 μm was used, and the dispersion density was 800 pieces / mm ² . The substrates were bonded together, and liquid crystal was sealed in the gap between the substrates to manufacture a liquid crystal display element. Regarding the obtained liquid crystal display element, the result of the twist angle check using a polarization microscope, the evaluation of the domain area by the image processing device, the pretilt angle (θ _p ) measurement by the Cryst. Rotat method, and the evaluation of the viewing angle dependence are shown. It is shown in FIGS.

From the results shown in FIG. 4, it can be seen that the larger the pitch of the liquid crystal molecules, the larger the number of domains and the smaller the domain area. From the results shown in FIG. 5, it was found that the smaller the pretilt angle, the larger the number of domains and the smaller the domain area. In addition, the number of domains rapidly increases near a pretilt angle of 2 ° or less, and the domain area is sufficiently reduced from around 2 °, so the pretilt angle is preferably 2 ° or less, and particularly 0 ° or less.
Is more preferable. From the results shown in FIG. 6, the domain area is small when the spacer density is 600 pieces / mm ² . However, when the spacer density exceeds 900 pieces / mm ² , the gap unevenness and the light leakage frequently occur due to the spacer aggregation, which is not preferable. Therefore, it is most preferable to set the spray density to about 800 pieces / mm ² .

When the viewing angle dependence of the liquid crystal display device of this example was measured, the curve shown in FIG. 8 was obtained.
The results shown in FIG. 8 are clearly superior to the conventional viewing angle dependence shown in FIG. 12, and it is clear that a high contrast ratio is obtained in both the horizontal direction and the vertical direction.

[Embodiment 2] As Embodiment 2, a cell was formed by subjecting the upper and lower substrates to the SH6020 thin film forming treatment by rubbing treatment in the same manner as in Embodiment 1.
In this case, the same liquid crystal as in Example 1 was used. FIG. 7 shows the relationship between the spacer density and the domain area and the number of domains in this example. From this figure, the spacer density is 1
It was clarified that a good result was exhibited from about 00 pieces / mm ² . The viewing angle characteristics of this liquid crystal element are shown in Example 1.
It exhibited the same characteristics as those of No. 1 and was excellent. Incidentally, when it is determined by integrating the results of Figures 6 and 7, the spacer density is good in the range of 100 to 900 pieces / mm ^2, preferably 200 to 900 pieces / mm ^2, more preferably 60
It becomes 0-900 pieces / mm ² .

[0038]

As described above, according to the invention described in claim 1, the pretilt angle of the alignment film in contact with the liquid crystal material having both right-handedness and left-handedness is set to 2 ° or less,
The right-handedness and left-handedness of the liquid crystal molecules are easily exerted, which allows the innumerable liquid crystal molecules present in the liquid crystal material to randomly exhibit right-handedness and left-handedness. Since 90 ° clockwise and 90 ° counterclockwise can exist at random, the twist angle of liquid crystal molecules is apparently expanded to 180 °. However, it does not adversely affect the characteristics of the TN liquid crystal itself.
Therefore, the viewing angle dependence can be improved and the contrast ratio can be improved in the liquid crystal while maintaining the TN mode.

In order to make the liquid crystal molecule E exhibit both right-handedness and left-handedness, a right chiral agent and a left chiral agent have the same effect even if no chiral agent is added to the liquid crystal material. It is advisable to add, for example, an equal amount so as to exert only this. Further, if the pretilt angle of the alignment film in contact with the liquid crystal is 0.5 ° or less, the right-handedness and left-handedness of the liquid crystal molecule E are very easily exhibited.

The right-handedness and the left-handedness of the innumerable liquid crystal molecules E in the liquid crystal material are randomly generated, but the right-handedness and the left-handedness cannot be controlled as they are. Therefore, if a large number of projections or depressions are formed on the alignment film surface. With these as cores, both dextrorotatory and dextrorotatory can be reliably generated. When the convex portion or the concave portion is present 100 / mm ² or more on the alignment film, the entire display element will be the dextrorotatory or levorotatory corresponding to these numbers fine multidomain occurred is made , It is possible to display a wide viewing angle that is even with the naked eye. As a specific example of the above-mentioned convex portion or concave portion, a spacer can be used for defining the space between a pair of substrates arranged to face each other. This makes it possible to realize a multi-domain structure by introducing dextrorotatory and levorotatory nuclei by using spacers which are indispensable components for liquid crystal display elements, without separately providing convex portions or concave portions on the alignment film. .

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a liquid crystal display element according to the present invention.

FIG. 2 is a diagram for explaining a 90 ° twist of a TN liquid crystal when no electric field is applied.

FIG. 3 is a diagram for explaining an alignment state of liquid crystals when an electric field is applied.

FIG. 4 is a diagram showing the relationship between the liquid crystal pitch, the number of domains, and the domain area of the liquid crystal display element of Example 1.

5 is a diagram showing the relationship between the pretilt angle of liquid crystal molecules of the liquid crystal display element of Example 1, the number of domains, and the domain area. FIG.

6 is a diagram showing a relationship between a spacer density and a domain area of the liquid crystal display element obtained in Example 1. FIG.

FIG. 7 is a diagram showing the relationship between the spacer density and the domain area of the liquid crystal display element obtained in Example 2.

FIG. 8 is a diagram showing the viewing angle dependence of the liquid crystal display element of the example.

9A and 9B are views for explaining an example of a conventional method for manufacturing an alignment film, wherein FIG. 9A is a side view showing an alignment film preparation layer formed on a substrate, and FIG. 9B is transferred to the alignment film preparation layer. A side view showing a state where an uneven pattern is formed by a mold, (c) a side view showing a state where a resist is formed, (d) a cross-sectional view showing a state where a part of the resist is removed, (e) A cross-sectional view showing a state in which a second transfer is being performed from above the partially removed resist by a transfer mold, (f) is a cross-sectional view showing the obtained alignment film,
(G) is a cross-sectional view of a main part of a liquid crystal element that has been subjected to region division alignment.

10A and 10B are views for explaining another example of a conventional method of manufacturing an alignment film, in which FIG. 10A is a side view showing an alignment film having a low pretilt angle formed on a substrate, and FIG. A side view showing an alignment film having a high pretilt angle formed on a corner alignment film, (c) a cross-sectional view showing a resist formed on a high pretilt angle alignment film, and (d) removing a part of the resist A cross-sectional view showing a state in which the transfer is performed by a transfer mold from above the partially removed resist,
(F) is a cross-sectional view of a main part of a liquid crystal element that has been subjected to region division alignment.

FIG. 11 is an explanatory diagram for explaining a conventional structure in which the upper and lower substrates are subjected to alignment treatment in two directions orthogonal to each other.

12 is a diagram showing viewing angle characteristics of a conventional liquid crystal display element subjected to the alignment treatment shown in FIG.

[Explanation of symbols]

 E liquid crystal molecule, 20 liquid crystal display element, 21, 22 substrate, 23, 24 polarizing plate, 27 spacer, 28, 29 alignment film,

Claims (6)

[Claims] 1. An alignment film is formed on the facing surfaces of a pair of substrates arranged to face each other with a constant spacing,
A liquid crystal display device in which a liquid crystal material is held in the space, wherein the liquid crystal material is a liquid crystal material capable of exhibiting both right-handedness and left-handedness, and at least one alignment film has a pretilt angle smaller than 2 °. A liquid crystal display device characterized by the following. 2. The right-handedness and left-handedness of the liquid crystal material are achieved by not adding a chiral agent or by adding an equal amount of a right-handed chiral agent and a left-handed chiral agent to the liquid crystal material, The liquid crystal display device according to claim 1, wherein the liquid crystal material is a twisted nematic liquid crystal. 3. A liquid crystal display device according to claim 1, wherein the pretilt angle is smaller than 0.5 °. 4. The surface of the alignment film according to claim 1, 2 or 3, wherein at least one of a convex portion having a height equal to or more than half the distance between the substrates and a concave portion having a depth equal to or more than half the distance between the substrates. The liquid crystal display element is characterized in that a plurality of are formed. 5. A liquid crystal display device, characterized in that the projections or recesses according to claim 4 are formed on the surface of the alignment film at a rate of 100 to 900 pieces / mm ² . 6. A liquid crystal display element, wherein the convex portion according to claim 4 or 5 is formed by a spacer inserted between the substrates in order to keep a constant gap between the substrates.