JP3466495B2 - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain fast response and an excellent displaying state by specifying the twist direction of liquid crystal molecules in the thickness direction of the liquid crystal layer and the initial twist angle. SOLUTION: A chiral nematic liquid crystal having a spontaneous twist pitch >=3/4 times liquid crystal layer thickness and positive dielectric anisotropy, is held between a pair of transparent electrode substrates and is constructed so as to have two metastable state comprising the first and the second alignment states, having &phiv;-180 deg. and &phiv;+180 deg. twist angles of liquid crystal molecules in the thickness direction respectively, as two relaxation states after Freedericksz transition is generated with application of voltages, expressing the initial twist angle of the liquid crystal molecules in the thickness direction as &phiv;. Then, polarizing plates are provided on both of the outside surface of the liquid crystal cell. Light transmission axes of the respective polarizing plates are located in direction with about (180 deg.-&phiv;)/2+40 deg. or about (180 deg.-&phiv;)/2-50 deg. angle with respect to the rubbing directions of the respective substrates in contact with them. Besides, 140 deg.<&phiv;<200 deg. is satisfied.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal display device having bistability.

[0002]

2. Description of the Related Art BTN (Bistable Tw) having bistability is used as an operation method of a liquid crystal having high-speed response.
Many proposals for the bistable twisted nematic (isted Nematic) method have been made so far.
(Japanese Patent Publication No. 1-5181, JP-A-6-230751, JP-A-8-101371, JP-A-8-313878, etc.). In these, the orientation states of the liquid crystal molecules are, by the drive voltage pulse, a first metastable state having a twist angle of (initial twist angle −180 °) and a second metastable state having a twist angle of (initial twist angle +180). Although it changes to either of the metastable states, in most cases, the case where the initial twist angle is 180 ° is described. In this case, the polarizing plates are arranged at an angle such that one of the polarizing plates is arranged so that its light transmission makes an angle of 45 ° with the rubbing direction of either substrate, and the other polarizing plate is arranged so that the light is transmitted therethrough. It is said that the transmission axis is arranged so as to be orthogonal to the light transmission axis of the polarizing plate, but the angular arrangement of the polarizing plate for obtaining a good display state when the initial twist angle is not 180 ° is clearly described. Nothing has been done, nor is there any mention of the initial twist angle dependence and the retardation dependence of the contrast ratio in that case.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device having a high speed response and a good display state.

[0004]

The optical states (transmittance in the case of a transmissive element) in two metastable alignment states are mainly retardation of the liquid crystal layer (birefringence (Δn) and liquid crystal layer thickness ( The product of d), Δnd), and the angular arrangement of the polarizers. In order to function as a display element, it is necessary to obtain a somewhat large contrast ratio due to the bi-stable orientation state. When the liquid crystal material and the cell gap are fixed and the retardation is fixed, the set initial twist angle (18
The optical states in the two quasi-Yasuhiko orientation states (not limited to 0 °) depend almost only on the angular arrangement of the polarizing plates, but still, the appropriate angular arrangement of the polarizing plates for obtaining a large contrast ratio is required. It's very difficult to know.

The present inventor uses the Jones matrix method in order to know the angular arrangement of polarizing plates which maximizes the contrast ratio obtained from the optical states in two metastable orientation states at an arbitrary set initial twist angle. Using the optical characteristics simulator used, calculate the optical state as a display element under the conditions of various combinations such as the retardation of the liquid crystal layer, the initial twist angle, the angle arrangement of the polarizing plate, and the contrast obtained at each initial twist angle. As a result of analyzing the angle arrangement of the polarizing plate that maximizes the ratio, it was found that the optimum angle arrangement of the polarizing plate can be represented mainly by the twist direction of the liquid crystal molecules in the thickness direction of the liquid crystal layer and the initial twist angle. It was confirmed by using a liquid crystal display element actually manufactured and proposed.

According to the above-mentioned proposal, the angular arrangement of the polarizing plates that maximizes the contrast ratio obtained at the initial twist angle φ is the twist of the liquid crystal from the back side to the front side when facing each polarizing plate. When the direction is positive and the light transmission axes of the respective polarizing plates are arranged so as to form an angle of approximately (180 ° −φ) / 2 + 40 ° with respect to the rubbing direction of the substrates that are respectively provided, Each of the light transmission axes of the polarizing plates is approximately (18) with respect to the rubbing direction of the substrate in contact therewith.
It was a case where it was arranged so as to form an angle of 0 ° -φ) / 2-50 °. After that, the inventors further studied, and confirmed that the contrast ratio obtained when the above-mentioned polarizing plate angular arrangement was changed depending on the initial twist angle and / or the liquid crystal retardation, We came up with appropriate conditions for improving the contrast ratio.

That is, the first feature of the present invention is that between a pair of transparent electrode substrates that have been subjected to alignment treatment so that the angles formed by the liquid crystal molecules and the substrate at the interface with the substrate are substantially equal on both substrates. , Sandwiching a chiral nematic liquid crystal having a certain natural twist pitch and having a positive dielectric anisotropy, which is 3/4 times or more the thickness of the liquid crystal layer, and the liquid crystal molecules in the thickness direction in the initial state (the state where no voltage is applied) When the twist angle is φ, the first alignment state in which the twist angle of the liquid crystal molecules in the thickness direction is φ-180 ° and the liquid crystal is a relaxation state after applying a voltage to cause the Freedericksz transition. A liquid crystal cell configured to have two metastable states in a second alignment state in which the twist angle of the molecule is φ + 180 °, and polarizing plates arranged on both outer sides of the liquid crystal cell,
And, when facing each polarizing plate, the direction of the twist of the liquid crystal from the back side to the front side is positive, and the light transmission axis of each polarizing plate is
Both the respective rubbing direction of the substrate to contact set
(180 ° -φ) / 2 + 40 ° there have the (180 ° -
φ) / 2-50 °, and φ
Is to provide 170 ° ± 3 ° , thereby solving the above-mentioned problems of the prior art. The above-mentioned "being substantially equal" means that the difference is about 3 ° or less even if the angles are different.

The twist angle φ is preferably about 170 ± 3 °.

A second feature of the present invention is that, in the liquid crystal display device as described above, the retardation (product of birefringence (Δn) and thickness (d), Δnd) of the liquid crystal layer is preferably 0.
235 μm to 0.270 μm, more preferably 0.2
A liquid crystal display device having a thickness of 50 μm to 0.255 μm is provided.

The present invention will be described in detail below with reference to the drawings. General Configuration Example of BTN (Bistable Twisted Nematic) Liquid Crystal Display Element FIG. 1 shows a general configuration example of a BTN (bistable twisted nematic) liquid crystal display element. A liquid crystal layer 30 is sandwiched between the lower substrate 11 and the upper substrate 12. Reference numerals 21 and 22 are transparent electrodes for applying a voltage to the liquid crystal layer, and 31 and 32 are alignment films for aligning the liquid crystal. Reference numerals 41 and 42 are polarizing plates.

The liquid crystal layer used here is 3/4 of the liquid crystal layer thickness.
It is a chiral nematic liquid crystal having a certain natural twist pitch, which is more than double, and positive dielectric anisotropy. The alignment film subjected to the alignment treatment aligns the liquid crystal in a direction slightly tilted from the substrate surface. This inclination angle is preferably about 2 ° to 30 °. When the inclination angle is small, the bistable operation becomes unstable and good switching cannot be performed. Further, if the tilt angle is too large, the viewing angle dependency of the display characteristics becomes large. The retardation (the product of birefringence (Δn) and thickness (d), Δnd) of the liquid crystal layer is generally said to be about 1/2 of the wavelength of the observation light. 1/2, or 0.2
It is said that about 75 μm is preferable. Further, the two polarizing plates are arranged at respective predetermined angular arrangements.

BTN Switching Operation Next, the BTN switching operation will be described. As the drive waveform, a voltage pulse for causing the Freedericksz transition (hereinafter referred to as a reset pulse) and a voltage pulse for selecting one of the following two metastable states (hereinafter referred to as a 2nd pulse). ) Is applied. The reset pulse is a voltage pulse equal to or higher than a threshold value (Vth) between the initial state and the two metastable states, and is 2n.
The d-pulse is a voltage pulse selected on the basis of a critical value (Vc) between two metastable states.

When the 2nd pulse voltage is below the critical value, the reset state (the alignment of liquid crystal molecules is in the homeotropic state)
Due to the backflow generated by the rapid relaxation from the liquid crystal molecules, the liquid crystal molecules are in a metastable alignment state in which the liquid crystal molecules are further twisted by 180 ° from the twist angle in the initial state (state where no voltage is applied). On the other hand, when the peak value of the 2nd pulse is equal to or more than the threshold value, the backflow is suppressed, and the liquid crystal molecules are in a metastable alignment state in which the twist is 180 ° smaller than that in the initial state. For example, when the initial twist angle is 180 °, the light transmission axis of one of the polarizing plates is arranged so as to form an angle of 45 ° with the rubbing direction of any substrate, and the light transmission axis of the other polarizing plate is further arranged. Is arranged so as to be orthogonal to the light transmission axis of the polarizing plate, the transmittance becomes relatively small (dark state) in the metastable orientation state in which the initial twist angle is 180 ° more twisted (360 ° twist in this case). On the other hand, in the metastable orientation state in which the twist angle is 180 ° less than the initial twist angle (0 ° twist in this case, that is, no twist), the transmittance is relatively large (bright state). In this case,
An example of the applied waveform and the optical response thereto is shown in FIG.
(Fig. 2a is a unipolar pulse waveform and the 2nd pulse voltage is below the critical value. Fig. 2b is an AC pulse waveform and the 2nd pulse voltage is below the critical value. Fig. 2c is a unipolar pulse waveform and the 2nd pulse voltage is below the critical value. In the above case. Fig. 2d shows an AC pulse waveform in which the 2nd pulse voltage is above the critical value.)

The reset pulse and the second pulse may be alternating current pulses or unipolar pulses. However, in the case of a unipolar pulse, it is necessary to periodically change the polarity so as to prevent charges from accumulating in the liquid crystal layer, or to change the polarity for each scanning electrode or textbook constituting the display panel. is there.

FIG. 3 shows the angular arrangement of the polarizing plates. Figure 3
, Θpol. Is the angle formed by the light transmission axis of the lower polarizing plate with respect to the rubbing direction of the lower substrate, and θana. Is the angle formed by the light transmission axis of the upper polarizing plate with respect to the rubbing direction of the upper substrate. θpol. And θana. The direction of the arrow indicating
These are the respective positive directions defined by the twisting direction of the liquid crystal from the back side to the front side when facing each polarizing plate. The maximum contrast ratio is found in θpol. And θana. Are both (180 ° -φ)
This is the case of / 2 + 40 °.

The maximum contrast ratio at each initial twist angle was calculated in the polarizing plate angular arrangement in the case of (180 ° -φ) / 2 + 40 ° and is shown in FIG. According to this, a certain degree of contrast ratio required for actual display is obtained when the initial twist angle φ is 140 ° <φ <20.
This is the case of 0 °. This is confirmed by the actual BTN cell, which will be described in detail in the embodiment.

Further, in FIG. 4, the initial twist angle φ is approximately 17
The maximum contrast ratio is obtained at 0 °, which is also confirmed by the actual BTN cell. Further BTN
In the method, the d / p range (d: cell gap, in which switching between two metastable orientation states is normally performed,
p: Natural twist pitch of liquid crystal. This d / p range is called an operation margin. ) Is also an important characteristic, but it has been confirmed by an actual BTN cell that this operating margin also depends on the initial twist angle φ and becomes maximum when φ is approximately 170 °.

Further, the change in the contrast ratio due to the retardation of the liquid crystal layer was calculated when the initial twist angle φ was about 170 ° with the same polarizing plate angle arrangement, and is shown in FIG. According to this, the contrast ratio is relatively large in the retardation range of 0.235 μm to 0.270 μm, which is smaller than 0.275 μm, which has been conventionally considered to be preferable, and the maximum value is 0.250 μm to 0.255.
This is the case of μm. This is also confirmed by the actual BTN cell.

Further, in the angular arrangement shown in FIG. 3, the maximum contrast ratio is found in θpol. And θan
a. Is approximately (180 ° -φ) / 2-50 °. In such a polarizing plate angle arrangement, the maximum contrast ratio at each initial twist angle was calculated and shown in FIG. According to this, it is when the initial twist angle φ is about 170 ° that the contrast ratio required for actual display can be obtained. This has been confirmed by the actual BTN.

Further, in FIG. 6, the initial twist angle φ is about 17
The maximum contrast ratio is obtained at 0 °, which is also confirmed by the actual BTN cell. Further BTN
In the method, the d / p range (d: cell gap, in which switching between two metastable orientation states is normally performed,
p: Natural twist pitch of liquid crystal. This d / p range is called an operation margin. ) Is also an important characteristic, but it has been confirmed by an actual BTN cell that this operating margin also depends on the initial twist angle φ and becomes maximum when φ is approximately 170 °.

Further, the change in the contrast ratio due to the retardation of the liquid crystal layer was calculated when the initial twist angle φ was about 170 ° with the same polarizing plate angle arrangement, and is shown in FIG. 7. According to this, the contrast ratio is relatively large in the retardation range of 0.235 μm to 0.270 μm, which is smaller than 0.275 μm, which has been conventionally considered to be preferable, and the maximum value is 0.250 μm to 0.255.
This is the case of μm. This is also confirmed by the actual BTN cell.

[0022]

EXAMPLES Examples of the present invention will be shown below.

Examples 1 to 7 and Comparative Examples 1 to 6 An alignment film of polyimito (AL-3046 made by Japan Synthetic Rubber) was formed on a glass substrate having a transparent electrode and subjected to an alignment treatment by rubbing. The other substrate that has been treated in the same way and the previous substrate have their orientation surfaces facing each other through a silica bead spacer with a uniform particle diameter, and the orientation processing directions are different by the same initial twist angle φ as desired. After stacking, the liquid crystal was sealed in the space between the substrates to prepare a liquid crystal cell with an initial twist angle φ and a cell gap of 2.4 μm. As liquid crystal, nematic liquid crystal ZLI-15 made by Merck
The twist pitch (p) was adjusted to 3.7 μm by adding a chiral agent S-811 made by Merck, which induces a clockwise twist to 57 (Δn: = 0.1147). Two polarizing plates are placed so as to sandwich the liquid crystal cell in the angle arrangement view of FIG.
l. And θana. Are both (180-φ) / 2 + 4
It is arranged so as to be 0, and the optical state when a drive waveform is applied that selects a metastable orientation state that is twisted by 180 ° more than the initial twist angle (φ + 180 ° twist) and 180 ° less than the initial twist angle. Twisted (φ-180 °
The optical state in the case where a drive waveform that selects the (twisted) metastable orientation state was applied was measured, and the contrast ratio was obtained from both. Table 1 and FIG. 8 show the results of obtaining the contrast ratio for various φ. It was confirmed that when the initial twist angle: φ is approximately 140 ° to 200 °, a relatively large contrast ratio that can be used as a display element is obtained.

[0024]

[Table 1]

Example 8, Comparative Examples 7 to 18 From the above examples, the initial twist angle φ: was about 170 °.
In the case of (Example 7), it was confirmed that the contrast ratio was maximized. Furthermore, Examples 1-7 and Comparative Examples 1-
In order to have the same initial twist angle φ as that prepared in 6, the two polymer film spacers having different thicknesses installed at both ends of the substrate were superposed and then liquid crystal was sealed in the space between the substrates, A model liquid crystal cell with a cell gap that changes continuously was prepared. The liquid crystal is a nematic liquid crystal ZLI1557 (Δn = 0.114) manufactured by Merck.
7) Merck chiral agent S that induces a right-handed twist
The twist pitch (p) was adjusted to 3.7 μm by adding −811. Two polarizing plates were arranged at a predetermined angle so as to sandwich the liquid crystal cell.

A drive waveform set so as to select each of the two metastable alignment states is applied to this liquid crystal cell, and from the cell gap and the twist pitch (p) at the boundary position between the two states, the two The d / p range (d / p margin) that allows the selection of two metastable orientation states by the waveform of the seed was calculated. The results are shown in Table 2 and FIG. It was confirmed that the d / p margin was maximized when the initial twist angle φ: was about 170 °.

[0027]

[Table 2]

Examples 9-14, Comparative Examples 19-26 Produced as in Example 8: Wedge cell (initial twist angle 170 °).
Was used to measure the contrast ratio at various Δnd by selecting the position on the cell corresponding to the desired cell gap. The results are shown in Table 3 and Fig. 10. It was confirmed that a large contrast ratio can be obtained in a retardation region smaller than about 0.275 μm, which was considered to be preferable in the past.

[0029]

[Table 3]

Examples 15 to 21, Comparative Examples 27 to 32 An alignment film of polyimito (AL-3046 manufactured by Nippon Synthetic Com) was formed on a glass substrate having a transparent electrode, and an alignment treatment with Rabin was performed. The other substrate that has been treated in the same way and the previous substrate have their orientation surfaces facing each other through a silica bead spacer with a uniform particle diameter, and the orientation processing directions are different by the same initial twist angle φ as desired. After stacking, the liquid crystal was sealed in the space between the substrates to prepare a liquid crystal cell with an initial twist angle φ and a cell gap of 2.45 μm.
As the liquid crystal, nematic liquid crystal ZLI-2 made by Merck
A twist pitch (p) was adjusted to 3 μm by adding a chiral agent S-811 made by Merck that induces a clockwise twist to 222-000 (Δn0.1124).

Two polarizing plates are placed so as to sandwich the liquid crystal cell, and θpol. And θana. So that both are (180-φ) / 2-50,
Twisted 180 ° more than the initial twist angle (φ + 180 °
180 ° from the initial twist angle and the optical state when a drive waveform that selects a metastable orientation state (of twist) is applied.
The optical state was measured when a drive waveform that selects a metastable orientation state with little twist (φ-180 ° twist) was applied, and the contrast ratio was obtained from both. Table 4 and FIG. 11 show the results of obtaining the contrast ratio for various φ. It was confirmed that when the initial twist angle φ is approximately 140 ° to 200 °, a relatively large contrast ratio that is usable as a display element can be obtained.

[0032]

[Table 4]

Example 22, Comparative Examples 33 to 44 From the above examples, the initial twist angle: φ was about 170 °.
In the case of (Example 7), it was confirmed that the contrast ratio was maximized. Further, two sheets of polymer film spacers having different thicknesses placed at both ends of the substrate were superposed on each other so as to have the same initial twist angle φ as those produced in Examples 15 to 21 and Comparative Examples 27 to 32. After that, liquid crystal was filled in the space between the substrates to prepare a model liquid crystal cell in which the cell gap continuously changed. As the liquid crystal, a nematic liquid crystal ZLI2222-000 (Δn
= 0.1124), a chiral agent S-811 made by Merck that induces a clockwise twist was added to adjust the twist pitch (p) to 37 μm.

Two polarizing plates were arranged at a predetermined angle so as to sandwich the liquid crystal cell. A drive waveform set so as to select each of the two metastable alignment states is applied to this liquid crystal cell, and the two types of waveforms are obtained from the cell gap and the twist pitch (p) at the boundary position between the two states. Allows the selection of two metastable orientation states d / p range (d / p
p margin) was calculated. The results are shown in Table 5 and FIG. D / p when the initial twist angle φ: is about 170 °
It was confirmed that the margin would also be maximized.

[0035]

[Table 5]

Examples 23 to 28, Comparative Examples 45 to 52 Wedge cells prepared in Example 22 (initial twist angle: 170)
) Was used to select the position on the cell corresponding to the desired cell gap to measure the contrast ratio at various Δnd. The results are shown in Table 6 and FIG. It was confirmed that a large contrast ratio can be obtained in a retardation region smaller than about 0.275 μm, which was considered to be preferable in the past.

[0037]

[Table 6]

[0038]

【The invention's effect】

1. Employing the polarizing plate angle disposed to obtain a maximum contrast ratio in claim 1-2 each initial twist angle, by setting a value that defines the initial twist angle, sufficient contrast is used as a display element from two metastable alignment state It is possible to obtain a ratio and to secure a sufficient operation margin for normally performing switching between two metastable orientation states, and to obtain a liquid crystal display element with an expanded cell gap margin. 2. ( 3 ) A liquid crystal display device further improved in the contrast ratio obtained from the two metastable alignment states obtained by the invention of claims 1 and 2 .

[Brief description of drawings]

FIG. 1 is a diagram illustrating a general configuration of a liquid crystal display element.

FIG. 2 is a diagram illustrating an applied waveform and an optical response to the applied waveform. 2a: When the 2nd pulse voltage is a critical value or less with a unipolar pulse waveform. 2b: In the case of an AC pulse waveform, when the 2nd pulse voltage is below a critical value. 2c: In the case of a unipolar pulse waveform, the 2nd pulse voltage is equal to or higher than the critical value. 2d: In the case of an AC pulse waveform, when the 2nd pulse voltage is equal to or higher than the critical value.

FIG. 3 (a) is a diagram illustrating an angular arrangement of polarizing plates,
(B) is a figure which shows the twist direction of the liquid crystal from the back side to this side.

FIG. 4 θpol. And θana. Together (180
It is a figure which calculated the maximum contrast ratio in each initial twist angle in the polarizing plate angle arrangement | positioning in the case of (degree- (phi)) / 2 + 40 degrees.

FIG. 5: θpol. And θana. Together (180
FIG. 6 is a diagram showing a change in contrast ratio due to retardation of the liquid crystal layer when the initial twist angle φ is about 170 ° in the polarizing plate angular arrangement of (° −φ) / 2 + 40 °.

FIG. 6: θpol. And θana. Together (180
It is a figure which calculated the maximum contrast ratio in each initial twist angle in the polarizing plate angle arrangement | positioning in the case of (degree- (phi)) / 2-50 degree.

FIG. 7: θpol. And θana. Together (180
FIG. 9 is a diagram showing a change in contrast ratio due to retardation of the liquid crystal layer when the initial twist angle φ is about 170 ° in the polarizing plate angular arrangement of (° −φ) / 2-50 °.

FIG. 8 is a diagram illustrating the relationship between the initial twist angle (deg) and the contrast ratio in Examples 1 to 7 and Comparative Examples 1 to 6.

FIG. 9 is a diagram illustrating a relationship between an initial twist angle (deg) and a d / p margin in Example 8 and Comparative Examples 7 to 18.

FIG. 10 is a diagram illustrating the relationship between the retardation value Δnd (μm) and the contrast ratio in Examples 9 to 14 and Comparative Examples 19 to 26. FIG.

FIG. 11 is a diagram illustrating the relationship between the initial twist angle (deg) and the contrast ratio in Examples 15 to 21 and Comparative Examples 27 to 32.

FIG. 12 is a diagram illustrating a relationship between an initial twist angle (deg) and a d / p margin in Example 22 and Comparative Examples 33 to 44.

FIG. 13 is a diagram illustrating the relationship between the retardation value Δnd (μm) and the contrast ratio in Examples 23 to 28 and Comparative Examples 45 to 52.

[Explanation of symbols]

11 lower substrate 12 upper substrate 21 transparent electrode 22 liquid crystal layer 31 alignment film 32 alignment film 41 polarizing plate 42 polarizing plate θpol. The angle θana. Formed by the light transmission axis of the lower polarizing plate with respect to the rubbing direction of the lower substrate. Angle formed by the light transmission axis of the upper polarizing plate with respect to the rubbing direction of the upper substrate φ Initial twist angle

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Claims (3)

(57) [Claims] 1. The thickness of a liquid crystal layer is 3/4 times the thickness of a liquid crystal layer between a pair of transparent electrode substrates that have been subjected to alignment treatment so that the angles formed by the liquid crystal molecules and the substrate at the interface with the substrate are substantially equal on both substrates. When sandwiching a chiral nematic liquid crystal having a positive dielectric anisotropy having a certain natural twist pitch as described above, and the twist angle of the liquid crystal molecules in the thickness direction in the initial state (state in which no voltage is applied) is φ, As a relaxation state after applying the voltage and causing the Freedericksz transition, the first alignment state in which the twist angle of the liquid crystal molecule is φ−180 ° in the thickness direction and the twist angle of the liquid crystal molecule is φ + 180 ° It has a liquid crystal cell formed to have two metastable states of a second alignment state, and polarizing plates arranged on both outer sides of the liquid crystal cell, and faces each polarizing plate. Case, from the back to the front The direction of the liquid crystal twist as positive, the light transmission axis of each polarizer, both with respect to the rubbing direction of the substrate to each contact set (180 ° -φ) / 2 + 4
It is arranged to form an angle of 0 °, and φ is 170
A liquid crystal display device characterized in that the angle is ± 3 ° . 2. The thickness of the liquid crystal layer is 3/4 times the thickness of the liquid crystal layer between a pair of transparent electrode substrates that have been subjected to alignment treatment so that the angles formed by the liquid crystal molecules and the substrate at the interface with the substrate are substantially the same on both substrates. When sandwiching a chiral nematic liquid crystal having a positive dielectric anisotropy having a certain natural twist pitch as described above, and the twist angle of the liquid crystal molecules in the thickness direction in the initial state (state in which no voltage is applied) is φ, As a relaxation state after applying the voltage and causing the Freedericksz transition, the first alignment state in which the twist angle of the liquid crystal molecule is φ−180 ° in the thickness direction and the twist angle of the liquid crystal molecule is φ + 180 ° It has a liquid crystal cell formed to have two metastable states of a second alignment state, and polarizing plates arranged on both outer sides of the liquid crystal cell, and faces each polarizing plate. Case, from the back to the front The direction of the liquid crystal twist as positive, the light transmission axis of the polarizing plates, both with respect to the rubbing direction of the substrate to contact set respectively (180 ° -φ) / 2-5
It is arranged to form an angle of 0 °, and φ is 170 ° ±
A liquid crystal display device characterized by being 3 ° . 3. The retardation of the liquid crystal layer [birefringence (Δ
n) and thickness (d) product, Δnd] is 0.235 μm
The liquid crystal display device according to any one of claims 1-2 is ～0.270Myuemu.