JP2010008911A - Liquid crystal element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal element which is made much lower in voltage and superior in stability. <P>SOLUTION: The liquid crystal element includes a pair of substrates which are arranged substantially in parallel to each other and at least one of which is transparent, a pair of alignment films arranged inside the substrates, and a liquid crystal material filled between the pair of alignment films, wherein surfaces of the alignment films are subjected to alignment processing so that liquid crystal molecules may be directed to the same direction, and the angle of directions of the alignment processing is 70 to 110°. The liquid crystal material contains an optical active substance which has a spiral pitch giving the reverse twist direction of a twist direction of liquid crystal molecules when a uniform twist structure is formed with a combination of the directions of the alignment processing of the pair of alignment films, and the liquid crystal molecules form the uniform twist structure. Here, pretilt angles of the liquid crystal molecules to the alignment films are from not less than 10° to not larger than an angle θph at which a double twist structure is formed in the absence of an applied electric field, and the ratio of the thickness (d) of a liquid crystal layer to the spiral pitch (p) satisfies 2<p/d<12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a liquid crystal element, and particularly relates to a reduction in voltage, stabilization, and viewing angle dependency of a reverse TN liquid crystal element.
In this specification, the optically active substance having a helical pitch that gives a twist direction opposite to the twist direction of liquid crystal molecules when a uniform twist structure is formed by a combination of directions of alignment treatments of both alignment films is described above. A TN liquid crystal that is contained in a liquid crystal material and whose liquid crystal molecules form a uniform twist structure is called a reverse TN liquid crystal.

  The liquid crystal element is rapidly expanding its market as a display. The liquid crystal display is superior to other display systems in terms of resolution, and the problems of contrast and color reproducibility, which depended on the viewing angle and contrast, which have been problems in the past, have been solved. Response speed) and reduction of driving voltage remain as problems to be improved.

  It is strongly desired to improve the above two problems for the TN liquid crystal. Of course, when these points are improved, for example, as a problem peculiar to the transmission type TN liquid crystal element, as described later, when a secondary adverse effect such as a decrease in transmittance from the front occurs, It is necessary to take measures to avoid it.

  In Patent Document 1, a liquid crystal material having a chiral nematic liquid crystal material disposed between alignment films and a twist of less than 90 degrees induced between the two alignment films and a twist direction of the liquid crystal material are opposite to each other. An element is disclosed.

  Patent Document 2 discloses a liquid crystal element in which the angle formed by the alignment treatment directions applied to both alignment films is about 90 degrees, and a uniform twist structure is formed by a combination of alignment treatment direction directions of the alignment films. A liquid crystal element is disclosed in which a liquid crystal material contains an optically active substance having a helical pitch that gives a twist direction opposite to the twist direction of liquid crystal molecules, and the liquid crystal molecules form a uniform twist structure.

  Furthermore, there are Non-Patent Documents 1 to 3 that the inventors of the present application previously made a conference presentation.

JP 2000-199903 A JP 2007-293278 A K. Takatoh, T. Kaneko, T. Uesugi, S. Kobayashi, Proceeding of IDW2007, 421 (2007) Takagami, Kaneko, Uesugi, Kobayashi Japanese Liquid Crystal Society Annual Meeting Proceedings 3pA03 High-head, high-speed, high-quality, wide viewing angle technology for liquid crystal displays, 10 pages, Technical Information Association (2006)

In the method described in Patent Document 1, the degree of voltage reduction is extremely limited. Even at the value showing the greatest effect, the saturation voltage is about 2.5V with respect to 3V.
It has been discovered that the liquid crystal element of Patent Document 2 is unstable and returns to a spray twist structure in a few minutes when no voltage is applied. When the use is started after the use is stopped once, it is necessary to reapply an electric field to make the whole TN structure. That is, the liquid crystal element of Patent Document 2 shows the possibility of large low voltage driving, but the stability is low.
Accordingly, a first object of the present invention is to propose a liquid crystal element having a large degree of voltage reduction and excellent stability.

Further, there is a problem peculiar to the transmission type TN liquid crystal element that the transmittance as viewed from the front is lowered only by designing according to the normal liquid crystal element design guidelines (for example, described in Non-Patent Document 3). May occur.
Therefore, a second object of the present invention is to propose a measure for solving such a problem.

The first problem has been solved by the invention of claim 1.
That is, a set of substrates arranged substantially in parallel and at least one of which is transparent, a set of alignment films disposed inside each substrate, and a liquid crystal material filled between the set of alignment films And an alignment treatment is performed on the surface of the alignment film so that the liquid crystal molecules in the liquid crystal material are oriented in the same direction, and the angle formed by the alignment treatment directions applied to both alignment films is 70 to 110 degrees. An optically active substance having a helical pitch that provides a twist direction opposite to a twist direction of liquid crystal molecules when forming a uniform twist structure by a combination of orientation directions of the one alignment film. In the liquid crystal element in which the liquid crystal material contains and the liquid crystal molecules form a uniform twist structure, the pretilt angle of the liquid crystal molecules with respect to the alignment film is 10 degrees or more and doubles when no electric field is applied. And not more than the angle θph forming the ist structure was solved by the liquid crystal element, wherein a ratio of the thickness d of the spiral pitch p and the liquid crystal layer is 2 <p / d <12.

The second problem has been solved by the invention of claim 2.
That is, in the liquid crystal element according to the first aspect of the invention, when the refractive index anisotropy of the liquid crystal material is Δn, the product Δn × d with the thickness d of the liquid crystal layer has a value larger than 0.5 μm and 3 μm. The present invention has been solved by a liquid crystal element having the following values, preferably 0.75 μm to 1.5 μm, more preferably 0.8 μm to 1.2 μm.

  An angle with respect to a plane perpendicular to a direction perpendicular to the alignment film (this direction is referred to as an axial direction in this specification) is referred to as a polar angle (azimuth angle) in this specification. When parallel to the alignment film, the polar angle is zero, and when parallel to the axial direction, the polar angle is 90 degrees or -90 degrees.

  FIG. 1 shows the arrangement of liquid crystal molecules 1 in a reverse TN liquid crystal. The alignment directions of the alignment films 2 and 3 on both sides are 90 degrees (the lower alignment film 2 is at 4 o'clock and the upper alignment film 3 is at 1 o'clock), and the liquid crystal molecules are in contact with both alignment films. In the plane including the alignment direction of the alignment film and the axial direction 4, the film rises at a certain pretilt angle with respect to the alignment film. In the middle region, the polar angle of the liquid crystal molecules is not changed much (to be precise, in the middle region, the polar angle of the liquid crystal molecules is slightly closer to the axial direction 4), and the alignment direction is rotated by 90 degrees. .

  FIG. 2 shows an array of spray structures. The direction of the pretilt angle in the region in contact with both alignment films 2 and 3 is equal, and in the intermediate region, the polar angle of the liquid crystal molecules 1 changes so as to be zero. That is, the direction is once perpendicular to the axial direction. As a result, a splay structure is formed in which the alignment directions of the liquid crystal molecules are distributed in a fan shape.

  FIG. 3 shows an array of spray twist structures. The spray twist structure is a structure in which a spray structure and a twist structure twisted 90 degrees between upper and lower substrates are combined.

The inventors of the present application seek a pretilt angle at which a stable reverse TN liquid crystal can be obtained, and perform mixing by changing the mixing ratio of the alignment film material realizing a low pretilt angle and the alignment film material realizing a high pretilt angle. Thus, alignment films having various pretilt angles were produced, and the stability of the liquid crystal having a reverse TN structure was examined.
As a result, it was confirmed that when an alignment film having a pretilt angle of 10 degrees is used, the reverse TN liquid crystal can be stably maintained for at least 1 minute.

On the other hand, regarding the upper limit of the pretilt angle, the inventors of the present application investigated the stability of the pretilt angle and the reverse TN structure.
As a result, it was found that the reverse TN structure cannot be realized when the pretilt angle is equal to or larger than a certain angle θph. This was an unexpected result.

  In the splay structure or the spray twist structure, when the pretilt angle increases, the splay structure becomes a more compressed structure. That is, the Gibbs free energy increases and these structures become unstable. On the other hand, the reverse TN liquid crystal is unstable because the reverse TN liquid crystal is transferred to the spray twist liquid crystal. Therefore, it is expected that when the pretilt angle is increased, the reverse TN liquid crystal becomes relatively stable, that is, a stable reverse TN liquid crystal can be obtained.

  However, the reason why the experimental results were not as expected as described above is that when the pretilt angle is high, the structure is different from the spray twist structure, as shown in FIG. This is presumed to be due to the formation of a double twist structure.

  It has been found that the double twist structure shown in FIG. 4 is formed when an electric field close to the saturation voltage is applied even when the pretilt angle is about 10 degrees (Non-Patent Documents 1 and 2). In the case of adopting such a structure, the drive voltage is greatly increased, and the object of the present invention to achieve a low voltage cannot be achieved.

  FIG. 5 shows the polar angle of liquid crystal molecules as a function of the distance from the alignment film in the double twist structure of FIG. As can be seen from the figure, the polar angle is bent in the reverse direction in the vicinity of the alignment film, is inverted in the intermediate region, and is then excessively returned in the vicinity of the other alignment film. It can be explained that this is because stress energy is absorbed by energy with a complicated twist.

  When the pretilt angle is about 10 degrees, such a structure does not occur when no voltage is applied. However, since increasing the pretilt angle has the same effect as applying a large applied voltage, it is considered that a double twist structure as shown in FIG. 4 is formed even when no voltage is applied.

  Since such a structure may occur, it has been found that there is an upper limit on the pretilt angle in order to produce a stable reverse TN liquid crystal element. That is, the pretilt angle needs to be equal to or smaller than a predetermined angle θph. Here, the predetermined angle θph is the maximum angle at which the reverse TN liquid crystal structure is maintained even when a voltage is applied and no other structure is formed. This varies depending on the liquid crystal material, the elastic modulus of the liquid crystal element, and the value of p / d (described later).

  In the reverse TN liquid crystal, when the thickness of the liquid crystal layer is d and the helical pitch of the liquid crystal material is p, the value of p / d is an important index. For example, if p = 5 μm and d = 5 μm, p / d = 1 and a spiral structure of 360 degrees is obtained. When p = 15 μm and d = 5 μm, p / d = 3, and a 1/3 pitch is formed in the liquid crystal layer. That is, the structure is twisted 120 degrees. When p = 10 μm and d = 5 μm, p / d = 2, and the structure is twisted 180 degrees. When p / d = 10, the structure is twisted 36 degrees.

  In the reverse TN liquid crystal, the twist direction determined by the combination of the pre-tilt angles of the upper and lower alignment films and the twist direction of the liquid crystal material are reversed, and a uniform twist structure is used instead of a spray twist structure. That is, in the reverse TN structure, the liquid crystal material is twisted in the opposite direction to the original spiral structure of the liquid crystal material. As a result, stress is generated in the liquid crystal material. Therefore, in the reverse TN liquid crystal, the larger the value of p / d, the less the stress inside the liquid crystal material and the more stable. However, the degree of voltage reduction is reduced. If p / d = 1 is greater than 12, the effect of lowering the voltage does not appear, so the value of forming the reverse TN structure is almost lost.

  On the other hand, when p / d is small, the effect of lowering the voltage becomes remarkable, but the structure of the reverse TN becomes unstable. When the pretilt angle is 10 degrees to θph, the reverse TN liquid crystal returns to the spray twist structure within 1 minute when p / d is 2 or less. Thus, it becomes a very unstable structure. For this reason, p / d needs to be 2 or more.

FIG. 6 is a graph plotting changes in saturation voltage (applied voltage at which transmittance is saturated) when only the pitch p is changed under the same conditions. As can be seen from the figure, in a region where the pitch p is large, the saturation voltage decreases linearly as p decreases. However, when the pitch p becomes smaller than a certain limit value, the graph bends and the saturation voltage rapidly decreases. The present invention recommends that a reverse TN liquid crystal be produced with a pitch p smaller than this limit value.
Note that the liquid crystal of Patent Document 1 relates to a liquid crystal in a region where the pitch p in the right part is large in this graph.

  In general, a TN device is designed such that Δn × d = 0.5 μm when the refractive index anisotropy of the liquid crystal material is Δn and the thickness of the liquid crystal is d in order to maximize the transmittance when no voltage is applied (for example, Non-Patent Document 3). As an industrial product, there is no departure from this condition. However, it has been found that when the liquid crystal element of the present invention is manufactured under these conditions, the front transmittance decreases.

  As will be described later, in the liquid crystal element of the present invention, the front transmittance is 30% of the maximum transmittance, and it is observed that it is dark when viewed from the front. This is because, in the case of the present invention, since no liquid crystal is applied to the substrate when no voltage is applied, Δn as viewed from the front is reduced.

  As a method for solving this problem, it was found that Δn × d should be made larger than 0.5 μm instead of the conventional condition of Δn × d = 0.5 μm (3 μm or less in practical use). Although depending on the liquid crystal material and the pretilt angle, Δn × d is not less than 0.75 μm and not more than 1.5 μm, preferably not less than 0.8 μm and not more than 1.2 μm, in order to obtain a sufficiently low voltage effect.

  When the value of Δn × d is smaller than 0.75 μm, there arises a problem that the front transmittance is low. On the other hand, if the value of Δn × d is too large, the liquid crystal material needs to be applied with a high voltage in order to exhibit a change in transmittance even if it rises in the absence of voltage application due to the effect of the present invention. Therefore, the effect of lowering the voltage cannot be obtained sufficiently.

As is clear from the above description, according to the present invention of claim 1 described above, a liquid crystal element having a TN structure that can be driven at a low voltage can be realized.
Further, according to the second aspect of the present invention, it is possible to improve the transmittance in the front of the liquid crystal element having a reverse TN structure that can be driven at a low voltage.

  Hereinafter, the present invention will be described in more detail while comparing Examples and Comparative Examples of the liquid crystal element according to the present invention.

<Example 1>
To form an ITO transparent electrode with an area of 1 × 1 cm ² which on a glass substrate having an electrical resistance of 30Ω / cm ^2. The condition of 3000 RPM by a spin coater using a polyimide solution in which 40% by weight of polyimide PIA-X768-01X for liquid crystal alignment film and 60% by weight of PIA-X359 made by Chisso Petroleum Co., Ltd. were mixed on this glass substrate. A polyimide film was formed.
The polyimide film was rubbed at a roller diameter of 2.5 cm, an indentation amount of 0.5 mm, and a roller rotation speed of 1000 RPM. The alignment films thus prepared were combined so that the rubbing direction was as shown in FIG. 7, and both ends of the substrate were fixed with an adhesive to prepare a liquid crystal cell.
RDP94808E062 (pitch 15 μm: counterclockwise) manufactured by Dainippon Ink Industries, Ltd. was injected into this liquid crystal cell. Immediately after the injection, a spray twist structure was formed. A reverse TN structure was obtained by applying a voltage of 10 V of 60 Hz rectangular wave to this cell for 10 minutes. The dependence of the transmittance of the obtained reverse TN liquid crystal on the applied voltage is shown as Example 1 in FIG.

<Comparative Example 1>
A liquid crystal element having the same configuration as that of the liquid crystal element described in Example 1 was prepared except that the liquid crystal material to be injected was a liquid crystal material (RDP94808) having no spiral structure (no chiral agent added to the liquid crystal material). The dependency of the transmittance of the liquid crystal element on the applied voltage was measured. The results are shown as Comparative Example 1 in FIG.

<Comparative example 2>
Except that the rubbing direction of the vertical alignment film was changed to the direction of FIG. 9, the dependency of the transmittance of the liquid crystal element produced in the same manner as in the method described in Example 1 on the applied voltage was measured. The results are shown as Comparative Example 2 in FIG.

  As can be seen from FIG. 8, in the case of Example 1, the threshold voltage is almost 0 V compared to RDP94808 (Comparative Example 1) having no spiral structure and RDP94808R062 (Comparative Example 2) having the same clockwise clockwise spiral pitch. The saturation voltage (voltage indicating the minimum luminance) was 1.2 V, which was extremely low as compared with the liquid crystal cells of Comparative Examples 1 and 2. This reverse TN liquid crystal existed stably for 5 minutes in a state where no voltage was applied, and then changed to a spray twist structure.

  In the case of Comparative Example 1, the threshold voltage was 0.9 V and the saturation voltage was 2.7 V, which were higher than the results of Example 1. In the case of Comparative Example 2, the threshold voltage was 2.0V and the saturation voltage was 5.0V, which was higher than that of Example 1.

<Comparative Example 3>
A liquid crystal device was prepared in the same manner as in Example 1 except that the alignment film used was polyimide PIA-X768-01X, 50%, PIA-X359-01X, 50%, and the transmittance depends on the applied voltage. Was measured. The results are shown as Comparative Example 3 in FIG. For comparison, the results of Example 1 are shown in FIG.

  Separately, an anti-parallel cell (parallel and opposite directions) was prepared using the same polyimide PIA-X768-01X, 50%, PIA-X359-01X, and 50% alignment film as in Comparative Example 3, and a pretilt was made. The pretilt angle was measured with an angle measuring device (Pretilt angle measuring system PAS-301, manufactured by Elsicon, USA). The pretilt angle of this alignment film was 17 degrees.

  According to FIG. 10, when the pretilt angle is 17 degrees, the dependency of the transmittance on the applied voltage is completely different from the case of the pretilt angle of 13 degrees described in Example 1, and the threshold voltage is 2.0 V (not shown). The saturation voltage was 9.0 V, which was an extremely high value as compared with the case where the chiral agent described in Comparative Example 1 was not added. This behavior cannot be explained by ordinary TN liquid crystal / spray twist liquid crystal. This liquid crystal structure is the same as the state that appears when the transmittance equal to or higher than the saturation voltage is increased in the first embodiment, in which a clockwise and counterclockwise twisted structure coexists in one cell (see the double line in FIG. 4). It is thought that (twist structure) appeared.

<Comparative example 4>
A liquid crystal device was prepared in the same manner as in Example 1 except that the alignment film used was polyimide PIA-X768-0X, 65%, PIA-X359-01X, 35%, and the transmittance depends on the applied voltage. Was measured. An electric field treatment was performed on a liquid crystal cell produced in the same manner as in Example 1. However, this cell showed no transition to reverse TN liquid crystal.

<Example 2>
The liquid crystal material used is ZLI-4792 (UR019) manufactured by Merck and the spiral pitch is 50 μm, and the alignment film material used is polyimide PIA-X768-01X, 45% PIA-X359-01X, 55 manufactured by Chisso Petrochemical Co., Ltd. A liquid crystal device was produced in the same manner as in Example 1 except that polyimide mixed with% (pretilt angle 21 degrees) was used. Next, an electric field treatment was performed in the same manner as in Example 1 to produce a reverse TN liquid crystal. This liquid crystal having a pretilt angle of 21 degrees existed stably for 3 hours. The dependence of the transmittance of the reverse TN liquid crystal on the applied voltage is shown in FIG. For comparison, FIG. 11 shows the applied voltage dependence of the transmittance of a normal TN liquid crystal. Also in this embodiment, a low voltage is realized.

<Example 3>
In Example 2, the firing temperature of the polyimide of the alignment film was set to 200 ° C. However, except that this firing temperature was set to 220 ° C., a liquid crystal element was manufactured under the same conditions as in Example 2 above, and reverse by electric field treatment. A TN liquid crystal element was formed. The obtained reverse TN liquid crystal element existed stably for 3 months. The dependence of the transmittance of the reverse TN device on the applied voltage is shown in FIG. For comparison, FIG. 12 shows the applied voltage dependence of the transmittance of a normal TN liquid crystal. Also in this embodiment, a low voltage is realized.

<Comparative Example 5>
A liquid crystal element was formed in the same manner as in Example 2 except that no chiral agent was added as a liquid crystal material and no spiral structure was formed. In this case, p / d was too small, the reverse TN liquid crystal was not formed, and the threshold voltage was 1.8 V and the saturation voltage was 4.0 V, both of which were higher than the reverse TN liquid crystal.

<Comparative Example 6>
A liquid crystal device was produced in the same manner as in Example 2 except that ZLI-4792 (US093) manufactured by Merck & Co., Ltd. and a helical pitch of 10 μm were used as the liquid crystal material. In this case, the reverse TN liquid crystal could not be formed even by applying an electric field. That is, if p / d is too small, the reverse TN liquid crystal is not formed.

<Comparative Example 7>
A liquid crystal device was produced in the same manner as in Example 2 except that ZLI-4792 (UR012) manufactured by Merck and a spiral pitch of 75 μm were used as the liquid crystal material. The obtained liquid crystal element was subjected to an electric field treatment in which a voltage was applied in the same manner as in Example 2. When the helical pitch was 75 μm, the threshold voltage was hardly decreased.

<Example 4>
With respect to the liquid crystal element according to the present invention produced in Example 3, the viewing angle dependency of the transmittance was measured using a liquid crystal electro-optical characteristic measuring device LCD5200 manufactured by Otsuka Electronics Co., Ltd. The obtained result is shown as Example 4 in FIG. For comparison, FIG. 13 shows the viewing angle dependence of the transmittance of a TN liquid crystal having a high pretilt angle (20 degrees).

  In a normal TN liquid crystal, the pretilt angle is as low as 5 degrees or less, so there is no change in transmittance depending on the viewing angle (polar angle) when no voltage is applied, but in FIG. 13, the pretilt angle is as large as 20 degrees. The viewing angle dependency of the transmittance is seen. However, the decrease in transmittance at the front is not so great.

  On the other hand, in the liquid crystal element of the present invention (Example 4), the front transmittance is 30% of the maximum transmittance. In FIG. 13, since the transmittance when no voltage is applied on the front is 100, it is not clear from the figure, but actually, the transmittance is low and dark when viewed from the front. In fact, it is observed that it is dark when viewed from the front as described above. In the case of the present invention, this is probably because the liquid crystal molecules rise with respect to the substrate when no voltage is applied, and Δn as viewed from the front is reduced.

  FIG. 8 of the first embodiment shown above shows the liquid crystal material RDP9408E062 having a refractive index anisotropy Δn of 0.19, the thickness of the liquid crystal layer is 5 μm, and transmission when Δn × d = 0.95 μm. The dependence of the rate on the applied voltage is shown for the liquid crystal element of the present invention (Example 1) and the TN liquid crystal elements (Comparative Examples 1 and 2).

  Under this condition, in the TN liquid crystal element, the frontal transmittance does not become the maximum, and a phenomenon in which the transmittance once rises near the threshold and becomes like a bump is observed. On the other hand, in the case of the present invention, this bump portion corresponds to a state when no voltage is applied. That is, this corresponds to a state in which a bias voltage of about 1.1 V is applied to the TN liquid crystal. This corresponds to the fact that the liquid crystal element of the present invention applies a bias voltage of about 1 V to the TN liquid crystal (the curve of the present invention is moved to the left by 1 V with respect to the curve of the TN liquid crystal). . Therefore, as in the case shown in FIG. 13, the transmittance from the front is not lowered, and the phenomenon of darkness when viewed from the front is not observed.

  FIG. 14 shows the applied voltage dependence of the transmittance in front of the liquid crystal element of the present invention and the TN liquid crystal element when Δn × d = 0.5 μm. The liquid crystal material used is ZLI-4792 manufactured by Merck, Inc., a TN liquid crystal having a low pretilt angle (1 degree), a TN liquid crystal having a high pretilt angle (20 degrees), and a reverse of the present invention having a high pretilt angle (20 degrees). TN liquid crystal. The saturation voltage is about 2V in the case of the present invention with respect to 4V for the TN liquid crystal, and it can be seen that the saturation voltage is about halved.

  The liquid crystal element according to the present invention described in the claims has been described based on the described examples and comparative examples. However, the technical scope of the present invention is not limited to the examples described above. Absent.

It is the perspective view which showed notionally the arrangement | sequence of the liquid crystal molecule of a reverse TN liquid crystal. It is sectional drawing which showed notionally the arrangement | sequence of the liquid crystal molecule of a spray structure. It is the perspective view which showed notionally the arrangement | sequence of the liquid crystal molecule of a spray twist structure. It is the perspective view which showed notionally the arrangement | sequence of the liquid crystal molecule | numerator of the double twist structure in which clockwise and counterclockwise coexist. It is the graph which showed the polar angle of the liquid crystal molecule as a function of the distance from alignment film by making an applied voltage into a parameter. It is the graph which plotted the change of the saturation voltage (applied voltage which the transmittance | permeability saturates) when only a pitch is changed. It is the figure which showed the rubbing direction of Example 1. FIG. It is the graph which showed the applied voltage dependence of the transmittance | permeability of the liquid crystal of Example 1 and Comparative Examples 1 and 2. FIG. It is the figure which showed the rubbing direction of the comparative example 2. 6 is a graph showing the applied voltage dependence of the transmittance of the liquid crystals of Example 1 and Comparative Example 3. It is the graph which showed the applied voltage dependence of the transmittance | permeability of the reverse TN liquid crystal of Example 2, and a normal TN liquid crystal. It is the graph which showed the applied voltage dependence of the transmittance | permeability of the reverse TN liquid crystal of Example 3, and a normal TN liquid crystal. 10 is a graph showing the transmittance with respect to the viewing angle of a TN liquid crystal having a high pretilt angle and a reverse TN liquid crystal of Example 4. It is the graph which showed the applied voltage dependence of the transmittance | permeability of TN liquid crystal of a low pretilt angle, TN liquid crystal of a high pretilt angle, and the reverse TN liquid crystal of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal molecule 2 Alignment film 3 Lower alignment film 4 Axial direction

Claims (2)

  A set of substrates arranged substantially in parallel and at least one of which is transparent; a set of alignment films disposed inside each substrate; and a liquid crystal material filled between the set of alignment films, A liquid crystal element in which the alignment treatment is performed on the surface of the alignment film so that the liquid crystal molecules in the liquid crystal material are oriented in the same direction, and the angle formed by the alignment treatment directions applied to both alignment films is 70 degrees to 110 degrees. An optically active substance having a helical pitch that gives a twist direction opposite to a twist direction of liquid crystal molecules when forming a uniform twist structure by a combination of orientation directions of the one alignment film. In a liquid crystal element that includes a liquid crystal material and in which the liquid crystal molecules form a uniform twist structure, a double twist structure is used when the pretilt angle of the liquid crystal molecules with respect to the alignment film is 10 degrees or more and no electric field is applied. And not more than the angle θph forming a liquid crystal element, wherein a ratio of the thickness d of the spiral pitch p and the liquid crystal layer is 2 <p / d <12.   2. The product of the liquid crystal material having a thickness Δd of Δn × d having a refractive index anisotropy of Δn is greater than 0.5 μm and not greater than 3 μm. The liquid crystal element described in 1.

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