JPH08278478A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display device which suppresses a bistable effect, has a high contrast even in a time-sharing driving system of higher order and has a high display response speed. CONSTITUTION: This liquid crystal display device is constituted to satisfy the following condition (a), (b), (c) and (d). (a) The twist angle α of liquid crystal molecules is in a range of 240 deg.<=α300 deg.. (b) The relation 0<(Pc-Ps)/Pc<0.3 holds between the spontaneous twist pitch Ps and regulating twist pitch Pc of the liquid crystal molecules. (c) The deviation angles β and γ respectively formed by the polarization axis direction of a pair of polarizing elements 9, 10 and the director direction of the liquid crystal molecules is contact with respective substrates 1, 2 satisfy either of ranges of 70 deg.<=β+γ<=110 deg., -110 deg.<=β+γ<=-70 deg., -20 deg.<=β+γ<=20 deg.. (d) The relation [(α360)-0.25]<d/Ps<[(α/360)+0.25] holds between the thickness (d) of the liquid crystal layer (c) and the spontaneous twist pitch Ps.

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, and more particularly to a twist nematic type (hereinafter referred to as "TN type") liquid crystal display device having excellent time division characteristics.

[0002]

2. Description of the Related Art Liquid crystal display devices are currently widely used mainly in TN type because they have advantages such as low power consumption, low manufacturing cost, and light weight and thinness. There is.

A TN type liquid crystal display device is constructed by enclosing a nematic liquid crystal having a positive dielectric anisotropy between two electrode substrates, and normally, a liquid crystal molecule is continuously twisted by 90 °. Has been done.

However, in a liquid crystal display device of this type having a twist angle of 90 ° (hereinafter referred to as "90 ° twist type"), the intensity change of transmitted light (or reflected light) with respect to the change of applied voltage is gentle. , The operating margin (the ratio of the lowest selection point voltage to the highest non-selection point voltage) becomes smaller,
Therefore, when the time-division order is increased during time-division driving, it is difficult to obtain a clear image with low contrast and the viewing angle is narrow. For example,
In the A4 size liquid crystal display device, it is said that the duty ratio of 1/200 or more is practically preferable, but in the practical liquid crystal display device, the duty ratio is about 1/100. The contrast ratio (brightness ratio between selection and non-selection) is as low as about 3.

As a technique for solving the problem of such a 90 ° twist type liquid crystal display device, Japanese Patent Laid-Open No. 60-107.
In the 020 publication, the twist angle of liquid crystal molecules is 180 to
A liquid crystal display device is disclosed in which the tilt angle of the optical axis of the liquid crystal molecules aligned at 360 ° and oriented to at least one of the electrode substrates is larger than 5 °. According to this liquid crystal display device, it is said that it is possible to realize a high contrast ratio of 19.6 when driven at a duty ratio of 1/100, for example.

However, in this liquid crystal display device, sufficient consideration is not given to the bistable effect, and there is a problem that the display response speed is low when the liquid crystal display device is driven at a high duty ratio. That is, in a liquid crystal cell, a so-called hysteresis phenomenon occurs in which the intensity of transmitted light changes when the applied voltage rises and when the applied voltage falls, and the bistable effect reduces the operating voltage range during time-division driving. Alternatively, there arises a problem that the response speed of on / off becomes slow. Further, as a result of these, display defects are likely to occur due to slight nonuniformity in cell thickness and temperature change. Therefore, it is necessary to suppress the bistable effect as much as possible.

[0007]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The present invention has the above-mentioned problems of (1) a 90 ° twist type liquid crystal display device, which has a small operation margin and a time division order in a time division driving device. If the value is increased, it is difficult to obtain clear images with low contrast.
(2) In the liquid crystal display device disclosed in Japanese Unexamined Patent Publication No. 60-107020, particularly, the display response speed is small, and the like is solved, the bistable effect is suppressed, and even in a high-order time-division drive system. An object of the present invention is to provide a liquid crystal display device having a high contrast and a high display response speed.

[0008]

Means for Solving the Problems The above-mentioned problems are met in a liquid crystal display device in which a liquid crystal composition containing a nematic liquid crystal to which an optical rotatory substance is added is disposed between a pair of substrates each having an alignment layer. a), (b), (c) and (d)
It is solved by a liquid crystal display device characterized by satisfying.

(A) The twist angle α of the liquid crystal molecules in the liquid crystal composition arranged between the pair of substrates is in the following range: 240 ° ≦ α ≦ 300 ° (b) The spontaneous twist pitch Ps of the liquid crystal molecules And the regulated twist pitch Pc of the liquid crystal molecules when the alignment layers are forcibly regulated by the alignment layer, the following relational expression holds: 0 <(Pc-Ps) / Pc <0. 3 (c) Deviation angles β and γ formed by the polarization axis directions of the polarizing elements arranged outside each of the pair of substrates and the director directions of the liquid crystal molecules in contact with each substrate satisfy either of the following ranges: 70 ° ≦ β + γ ≦ 110 ° −110 ° ≦ β + γ ≦ −70 ° −20 ° ≦ β + γ ≦ 20 ° (d) The following relational expression is provided between the thickness d of the liquid crystal layer and the spontaneous twist pitch Ps. Applicable [(α / 360) -0.25] < / Ps <[(α / 3
60) +0.25] Hereinafter, the present invention will be described in detail.

First, the outline of the present invention will be described with reference to FIG. FIG. 1 is an explanatory view showing an exploded main part of the liquid crystal display device. In FIG. 1, 1 and 2 are substrates having an alignment layer (not shown), 9 and 10 are polarizing elements, and C is a liquid crystal layer.

In the present invention, the twist angle α of the liquid crystal molecules is
Is 240 ° or more and 300 ° or less. This twist angle α
If is too small, the intensity change of the transmitted light with respect to the applied voltage is gradual, and sufficient contrast cannot be obtained during high-order time-division driving. On the other hand, if the twist angle α is too large, the orientation of the liquid crystal molecules tends to be disturbed when switching between on and off, and the display quality is degraded, and the large bistable effect slows the on / off response speed. .

The twist angle α is the direction of the alignment treatment for defining the alignment direction of the liquid crystal molecules on the substrates 1 and 2, the type and amount of the nematic liquid crystal constituting the liquid crystal layer C or the optical rotatory substance added thereto. It can be specified by

In FIG. 1, β is the direction of the polarization axis of the polarizing element 9 and the direction of the director of liquid crystal molecules in contact with the surface of the substrate 1, that is, the direction in which the molecular long axis of the liquid crystal molecules is preferentially oriented (however, , If the liquid crystal molecule has a non-zero pre-tilt angle with the substrate surface, it is the angle (hereinafter referred to as “deviation angle”) formed by the director direction of the director direction onto the substrate surface, and γ is the polarization It is the angle of deviation between the polarization axis direction of the element 10 and the director direction of liquid crystal molecules in contact with the surface of the substrate 2.

In the present invention, the spontaneous twist pitch P _S of the liquid crystal molecules and the regulated twist pitch P _S of the liquid crystal molecules when the alignment layer forcibly regulates the alignment of the liquid crystal molecules.
_The following relational expression (a) 0 <(P _C −P _S ) / P _C <0.3 (a) holds with _C.

Here, the spontaneous twist pitch P _S means a pitch in a natural twist of liquid crystal molecules generated in the liquid crystal by adding an optical rotatory substance or the like to a normal nematic liquid crystal. Specifically, as shown in FIG.
Substrates 1 and 2 having alignment layers 6 and 7 respectively formed on opposing surfaces of supporting plates 11 and 21 are arranged in a wedge shape to form a liquid crystal cell, and the liquid crystal composition is enclosed in the cells. The distance r between stripe patterns (discrimination lines at every 1/2 pitch) generated on the cell surface, the cell thickness (thickness of the liquid crystal layer C) d, and the cell length 1 are measured to obtain the following equation. it can.

Spontaneous twist pitch P _S = 2 dr / l In FIG. 2, 8 is a spacer, 9 and 10 are polarizing elements, and the alignment layers 6 and 7 are respectively subjected to alignment treatment in parallel directions. .

Further, the restricted twist pitch P _C is defined by the thickness d of the liquid crystal layer C and the twist angle α defined by the alignment treatment directions of the substrates 1 and 2 and the alignment layer in FIG.
It is defined by the following formula.

Restriction Twisting Pitch P _C = (360 ° / α) × d In the liquid crystal display device having the above configuration, the bistable effect of the liquid crystal display device can be suppressed for the reason described in detail below. As a result, the operation margin can be increased, and excellent characteristics in terms of contrast and display response speed can be obtained even in the case of high-order time-division driving.

That is, the present invention is based on this finding based on the fact that the parameter (P _C -P _S ) / P _C in the equation (a) has a specific correlation with the parameter B showing the bistable effect. It has been completed. Hereinafter, an example of an experiment conducted to clarify this point will be described.

FIG. 3 shows the parameter (P _C −
Is a graph showing the correlation between P _S ) / P _C and the parameter B indicating the bistable effect, and the horizontal axis is the parameter (P _C −P _S ) /
P _C , the vertical axis represents the parameter B indicating the bistable effect. Here, as shown in FIG. 4, in the liquid crystal cell of the type shown in FIG. 1, the parameter B indicating the bistability effect is such that when the applied voltage is increased, the amount of transmitted light of the cell is relatively 5.
When the applied voltage at the time of 0% is V _UP and the applied voltage at the time when the applied voltage is decreased to 50% of the transmitted light amount of the cell is V _DOWN , it is represented by the following formula.

In the parameter B = (V _UP −V _DOWN ) / V _UP = ΔV / V _UP experiment, three factors were individually changed (Experimental Example 1 to Experimental Example 3), and under each condition,
The values of the parameter (P _C −P _S ) / P _C and the parameter B were obtained.

Experimental Example 1 The spontaneous twist pitch of liquid crystal molecules was changed by changing the amount of the optically active substance "S-811" (manufactured by Merck) to be added to the liquid crystal composition in the range of 0.6 to 1.3% by weight. The experiment was conducted by changing P _S. At this time, other conditions are as follows.

Liquid crystal: “ZLI-2293” (manufactured by Merck) Twist angle α of liquid crystal molecules: 270 ° Thickness d of liquid crystal layer C: 7 μm Alignment layer: Alignment-treated by oblique vapor deposition using SiO (vapor deposition) Angle 7 °) The result of the above experiment is indicated by a symbol ◯ in FIG.

Experimental Example 2 An experiment was conducted by changing the relative angle of the alignment treatment direction of the alignment layer and changing the twist angle α of the liquid crystal molecules within the range of 180 to 360 °. At this time, other conditions are as follows.

Liquid crystal: “ZLI-2293” (manufactured by Merck Ltd.) Optical rotatory substance: “S-811” (0.974 wt%, manufactured by Merck Ltd.) Thickness d of liquid crystal layer C: 7 μm Alignment layer: oblique with SiO Alignment-treated by vapor deposition method (vapor deposition angle 7 °) The result of the above experiment is shown by a symbol x in FIG.

Experimental Example 3 An experiment was conducted by changing the thickness d of the liquid crystal layer C in the range of 5 to 9 μm. At this time, other conditions are as follows.

Liquid crystal: “ZLI-2293” (manufactured by Merck) Optical rotatory substance: “S-811” (0.974 wt%, manufactured by Merck) Twist angle α of liquid crystal molecules: 270 ° Alignment layer: oblique with SiO Alignment-treated by vapor deposition method (vapor deposition angle 7 °) The result of the above experiment is indicated by the symbol Δ in FIG.

As is clear from the result of FIG. 3, there is a substantially proportional relationship between the parameter (P _C -P _S ) / P _C and the parameter B (ΔV / V _UP ), and the parameter (P _C -P S _S ) / P _C
The value of parameter B tends to decrease linearly as the value of increases. This phenomenon is the same when various conditions in the liquid crystal cell are changed.

In the TN type liquid crystal display device, the parameter B indicating the bistable effect is practically -0.03.
It is preferably in the range of 0.03 to 0.03. From the results of FIG. 3, it was found that the value of the parameter (P _C −P _S ) / P _C is preferably in the range of −0.1 to 0.3 in order to obtain a preferable value as the parameter B. .

Experimental Example 4 The display response characteristics of some liquid crystal cells similar to those used in Experimental Examples 1 to 3 were obtained. The result is shown in FIG.

In FIG. 5, the horizontal axis is the parameter (P _C -P
_S ) / P _C , the vertical axis is the parameter C representing the display response characteristic, and the display response time during ON / OFF during time division driving at 1/100 duty ratio is t _ON and t respectively.
_{When turned OFF} , it is expressed by the following equation.

Parameter C = [(t _ON + t _OFF ) / 2] ^{−1 The} larger the value of the parameter C, the shorter the on / off display response time and the better the display response characteristic.

As is clear from the results shown in FIG. 5, when the value of the parameter (P _C -P _S ) / P _C is larger than 0, the value of the parameter C becomes large, so that a good display response characteristic can be obtained. There was found.

From the results of the above Experimental Examples 1 to 4, in the present invention, the value of the parameter (P _C -P _S ) / P _C is
It is practically required to be larger than 0 and smaller than 0.3.

Furthermore, in the present invention, the thickness d of the liquid crystal layer C and the spontaneous twist pitch P are set in order to stabilize the twisted state of the liquid crystal molecules and prevent the arrangement of liquid crystal molecules having different twist angles from occurring. _The following relational expression holds with _S.

[(Α / 360) -0.25] <d / P _S
<[(Α / 360) +0.25] In the present invention, the product Δn · d of the refractive index anisotropy Δn of the liquid crystal layer C and the thickness d of the liquid crystal layer C is a point such as contrast and brightness. Therefore, it is preferably 0.4 or more and 1.5 or less, and particularly preferably 0.8 or more and 1.2 or less.

Further, in the present invention, it is preferable that the pretilt angle θ _O formed by the director direction of the liquid crystal molecules contacting the surface of the substrate and the substrate surface satisfies the following relational expression.

5 ° ≦ θ _O ≦ 40 ° By setting the pre-tilt angle θ _O to a large value in this way, it is possible to prevent the formation of a scattering composition that adversely affects the light transmission characteristics.

As the substrate orientation treatment, SiO, Mg
A method of oblique vapor deposition using O, MgF ₂ or the like, rubbing the surface of a coating of a polymeric substance such as an imide type, an amide type, a polyvinyl alcohol type, a phenoxy type with a cotton cloth, a vinylon cloth, a Tetoron cloth, absorbent cotton, etc. A method of rubbing to form grooves in a certain direction on the surface, or a method of coating a surface of a substrate with a carboxylic acid chromium complex, an organic silane compound, or the like by plasma polymerization or the like, and orienting liquid crystal molecules to the substrate by chemical adsorption. , Etc. can be used.

Further, in the present invention, the polarizing elements 9 and 1
The deviation angles β and γ formed by the polarization axis direction of 0 and the director direction of the liquid crystal molecules in contact with the surfaces of the substrates 1 and 2 are
Set so as to satisfy any of the following relational expressions.

Β + γ = + 90 ° ± 20 ° β + γ = −90 ° ± 20 ° β + γ = 0 ° ± 20 ° That is, the deviation angles β and γ are set to satisfy one of the following ranges.

70 ° ≦ β + γ ≦ 110 ° −110 ° ≦ β + γ ≦ −70 ° −20 ° ≦ β + γ ≦ 20 ° As the liquid crystal composition constituting the liquid crystal layer C in the present invention,

[0043]

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[0044]

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And the like or a mixture thereof. The liquid crystal composition may contain a smectic liquid crystal component, a cholesteric liquid crystal component, etc., if necessary.

The optically active substance is generally called a chiral nematic liquid crystal, for example, an ester system having an optically active group represented by the following general formula as an end group,
A nematic liquid crystal such as a biphenyl type, a phenylcyclohexane type, or an azo type can be used.

[0047]

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(R ₁ , R ₂ , R _{3 are} alkyl groups or hydrogen atoms, and R ₁ , R ₂ and R ₃ are different from each other.) Specific examples of the optically active substance include compounds having the following structures. Can be used.

[0049]

[Chemical 4]

[0050]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 6 is an explanatory sectional view showing an embodiment of the present invention. In the liquid crystal display device shown in FIG. 6, two substrates 1 and 2 are arranged so as to be opposed to each other, and the substrate 1 has an electrode layer 4 and an alignment layer 6 on an inner surface of a support plate 11.
The substrate 2 is formed by forming the electrode layer 5 and the orientation layer 7 on the inner surface of the support plate 21. Further, the space between the two substrates 1 and 2 is sealed by a sealing portion 3 to form a cell. Inside the cell, spacers 8 are arranged in a distributed state and filled with a liquid crystal composition to form a liquid crystal layer C. Further, a front polarizing element 9 and a rear polarizing element 10 are formed on the outer surfaces of the substrates 1 and 2, respectively. In the figure, reference numeral 13 is a reflecting plate formed on the outer surface of the rear polarizing element 10. It should be noted that the reflective plate 13 may not be used in the transmissive liquid crystal display device.

The materials for the support plates 11 and 21 are soda glass, borosilicate glass, glass such as quartz, uniaxially stretched polyethylene terephthalate, plastics such as polyether sulfone and polyvinyl alcohol, aluminum, stainless steel and the like. Can be used.

The electrode layers 4 and 5 have a thickness of 1.1, for example.
The transparent electrodes E and E'made of, for example, 1000 Å ITO (tin and indium oxide) and having a thickness of 1000 Å are arranged in parallel with each other on the surfaces of the support plates 11 and 21 of mm, and one of the electrode layers 4 is formed. The transparent electrode E constituting the transparent electrode E and the transparent electrode E ′ constituting the other electrode layer 5 are configured so that they are at right angles to each other, whereby, for example, 0.3 mm ×
A matrix display electrode structure composed of 0.3 mm pixels is constructed.

The alignment layers 6 and 7 are vapor-deposited films having a thickness of, for example, 500 Å formed by the oblique vapor deposition method using SiO (deposition angle: 7 for the support plates 11 and 21, respectively).
°). In this case, the pre-tilt angle θ _O
Is around 30 °.

The liquid crystal composition constituting the liquid crystal layer C is a nematic liquid crystal "ZLI-2293" (manufactured by Merck).
The optical rotatory substance (chiral nematic liquid crystal) "S-8
11 "(manufactured by Merck) was added at 1.10% by weight.

If necessary, the substrates 1 and 2 may be further provided with a dielectric layer, an alkali ion migration preventing layer, an antireflection layer, a polarizing layer, a reflecting layer and the like.

The front polarizing element 9 is "F-1205D
U ”(manufactured by Nitto Denko Corporation), and is arranged such that the polarization axis direction has a deviation angle β of 40 ° with respect to the director direction of the liquid crystal molecules in contact with the surface of the alignment layer 6. Similarly, the rear polarizing element 10 and the reflector 13 are
The polarization axis direction of the rear polarizing element 10 is “F-3205M” (manufactured by Nitto Denko Corporation) and has a deviation angle γ of 50 ° with respect to the director direction of the liquid crystal molecules in contact with the surface of the alignment layer 7. Are arranged as follows. Therefore, β +
γ = 90 °.

As the spacer 8, glass fiber "PF-70S" (manufactured by Nippon Electric Glass Co., Ltd.) was used as the seal material constituting the seal portion 3. Structbond "XN-5A-C" (Mitsui East) Pressure Chemical Co., Ltd. was used.

In the liquid crystal display device having the above structure, the cell thickness (the thickness d of the liquid crystal layer C) is 7.0 μm, the twist angle α of the liquid crystal molecules is 260 ° counterclockwise from the front, and the twist angle α is 260 °.
The spontaneous twist pitch P _S is 8.5 μm, the regulated twist pitch P _C is 9.7 μm, and the parameter (P _C −P _S ) / P _C is 0.
It was 12.

Further, in this liquid crystal display device, the value of the parameter B showing the bistable effect is as small as almost 0, which is 1/5.
High-order time-divisional driving with a duty ratio of 00 or more was possible. The liquid crystal display device was operated at a duty ratio of 1/100 by a time-division driving method, and the contrast ratio and on / off display response time were obtained.

As a result, the contrast ratio in the visible light region having a wavelength of 400 to 700 nm, that is, the ratio of the reflected light luminance in the selected state (dark) and the reflected light luminance in the non-selected state (bright) is 1:13 or more. It was good, and a clear image with excellent contrast was obtained. Further, the on / off response time was as short as 300 msec or less, and it was confirmed that the display response characteristics were excellent.

Comparative Example 1 For comparison, a nematic liquid crystal “ZLI-2293” (manufactured by Merck) was added to a nematic liquid crystal “chiral nematic liquid crystal” “S-811” (manufactured by Merck) as a liquid crystal composition. A liquid crystal display device was constructed in the same manner as in the above-mentioned example except that the liquid crystal display device containing 0.880% by weight was used.

In the liquid crystal display device having the above structure, the cell thickness (thickness d of the liquid crystal layer C) is 7.0 μm, and the twist angle α of the liquid crystal molecules is 270 from the front to the left (counterclockwise).
The spontaneous twist pitch P _S was 11.6 μm, the regulated twist pitch P _C was 9.3 μm, and the parameter (P _C −P _S ) / P _C was −0.25.

In this liquid crystal display device, the value of the parameter B indicating the bistable effect is as large as 0.04, which is 1 /
It was difficult to perform time-divisional driving with a high order of 200 duty ratio or more. Further, this liquid crystal display device was operated by a time division driving method at a duty ratio of 1/100 in the same manner as in the embodiment, and the contrast ratio and the on / off display response time were obtained. The contrast ratio was 1:11. Although large, the on / off response time was long, on the order of tens of seconds, and could not be put to practical use.

Comparative Example 2 For comparison, a nematic liquid crystal “ZLI-2293” (manufactured by Merck) was added to a nematic liquid crystal (chiral nematic liquid crystal) “S-811” (manufactured by Merck) as a liquid crystal composition for comparison. A liquid crystal display device was constructed in the same manner as in the above-mentioned example except that the material containing 0.98% by weight was used.

In the liquid crystal display device having the above structure, the cell thickness (thickness d of the liquid crystal layer C) is 7.0 μm, the twist angle α of the liquid crystal molecules is 260 ° counterclockwise from the front,
The spontaneous twist pitch P _S was 9.7 μm, the regulated twist pitch P _C was 9.7 μm, and the parameter (P _C −P _S ) / P _C was 0.

In this liquid crystal display device, the value of the parameter B showing the bistable effect is as small as 0.01, but it is operated by the time division drive system at the 1/100 duty ratio in the same manner as in the first embodiment. Contrast ratio and on
When the off display response time was obtained, it was confirmed that the contrast ratio was 1:12 and the on / off display response time was as long as about 600 msec, which was inferior to the case of the above-mentioned embodiment.

[0068]

According to the present invention, the bistable effect is suppressed,
It is possible to provide a liquid crystal display device having a high contrast and a high display response speed even in a high-order time-division drive system.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an outline of the present invention.

FIG. 2 is an explanatory diagram for identifying a spontaneous twist pitch P _s .

FIG. 3 is a graph showing the relationship between the parameter (P _c −P _s ) / P _c and the parameter B (ΔV / V _UP ) indicating the bistable effect.

FIG. 4 is an explanatory diagram for specifying a parameter B.

FIG. 5 is a graph showing a relationship between a parameter (P _c −P _s ) / P _c and a parameter C [(t _ON + t _OFF ) / 2] ⁻¹ indicating a display response characteristic.

FIG. 6 is a sectional view of one embodiment of the present invention.

[Explanation of reference numerals] 1, substrate 11, 21 support plate 3 seal portion 4,5 electrode layer 6,7 alignment layer 9 front polarizing element 10 rear polarizing element 13 reflector C liquid crystal layer

Claims (1)

[Claims] 1. A liquid crystal display device comprising a liquid crystal composition containing a nematic liquid crystal to which an optical rotatory substance is added between a pair of substrates each having an alignment layer, wherein the following condition (a):
A liquid crystal display device characterized by satisfying (b), (c) and (d). (A) The twist angle α of liquid crystal molecules in the liquid crystal composition arranged between the pair of substrates is in the following range. 240 ° ≦ α ≦ 300 ° (b) The following relationship between the spontaneous twist pitch Ps of the liquid crystal molecules and the regulated twist pitch Pc of the liquid crystal molecules when the alignment layer forcibly regulates the alignment of the liquid crystal molecules. The formula holds. 0 <(Pc-Ps) / Pc <0.3 (c) A deviation angle β formed by the polarization axis direction of the polarizing element arranged outside each of the pair of substrates and the director direction of the liquid crystal molecules in contact with each substrate. And γ satisfy one of the following ranges. 70 ° ≦ β + γ ≦ 110 ° −110 ° ≦ β + γ ≦ −70 ° −20 ° ≦ β + γ ≦ 20 ° (d) The following relational expression holds between the thickness d of the liquid crystal layer and the spontaneous twist pitch Ps. thing. [(Α / 360) -0.25] <d / Ps <[(α / 3
60) +0.25]