JPH06138435A - Liquid crystal display device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a high-density large-screen liquid crystal display device having a high response speed and an excellent contrast ratio. [Structure] A phase plate 4, between the liquid crystal cell 1 and the polarizing plates 2, 3.
5 is arranged, and the applied voltage when not selected is 1.
A super-twisted nematic liquid crystal display device having a product of the optical anisotropy Δn of the liquid crystal and the cell gap d of 1 μm or more. [Effect] Since a high speed response is obtained, a word processor or personal computer using a display mouse can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super twisted nematic liquid crystal display device.

[0002]

2. Description of the Related Art A super twisted nematic liquid crystal device having a liquid crystal layer having a twist angle of 180 degrees or more from 90 degrees of a conventional twisted nematic liquid crystal has a steep threshold characteristic. Therefore, high time division driving using XY electrodes is possible, and it is widely used as a screen display device for laptop type word processors, personal computers and the like.

[0003] The ratio of the effective voltage V _ON at selection and the effective voltage V _OFF during the non-selection is determined uniquely by the number of scanning lines N of the XY electrode when performing time division driving (matrix electrodes). The relationship is shown in the following formula [3].

The liquid crystal layer sandwiched between the two substrates of the nematic liquid crystal display device is composed of liquid crystal molecules having a birefringence and has a property of changing the polarization state of incident light. When no voltage is applied, the molecular axes of liquid crystal molecules are aligned substantially parallel to the substrate surface. When the applied voltage exceeds a certain value, the orientation of the liquid crystal molecules changes, and the liquid crystal molecules rise. The voltage at this time is the threshold voltage (V _th = (C ₀
-C _a + αV _a ) / α).

When the orientation of liquid crystal molecules changes, the polarization state of transmitted light also changes. The super twisted nematic liquid crystal display device performs display by utilizing the difference between the polarization state of transmitted light when not selected and the polarization state of transmitted light when selected. The amount of change in the polarization state of the transmitted light due to the change in the orientation of the liquid crystal molecules is determined by the product of the optical anisotropy Δn of the liquid crystal molecules and the cell gap d, and increases as Δnd increases.

The response speed and the display quality are important factors in evaluating the performance of the liquid crystal display device. The response speed and contrast ratio of the super twisted nematic liquid crystal display device depend on V _OFF . The amount of alignment change of the liquid crystal molecules due to the change of applied voltage depends on the applied voltage, and if the ratio of V _ON and V _OFF is kept constant, the change in alignment between the selected time and the non-selected time is V _OFF = V _th . It becomes maximum and becomes smaller as V _OFF becomes higher than V _th . Therefore, the response time becomes the longest (slow) at V _OFF = V _th , and
It becomes shorter (faster) as _OFF becomes higher than V _th .

On the other hand, the display quality becomes better as the difference in transmitted polarization between the selected state and the non-selected state becomes larger. The display quality includes contrast ratio and brightness, but V _OFF = V _th
In, both brightness and contrast ratio are compatible. V _OFF
Is set to a voltage higher than V _th , the contrast ratio must be sacrificed in order to obtain brightness. On the contrary, if an attempt is made to increase the contrast ratio, the brightness will decrease, and good display quality cannot be obtained in any case. Thus, the response time and the display quality have a trade-off relationship with the applied voltage value. .

In the conventional super twisted nematic liquid crystal display device, an attempt is made to shorten the response time by using compensating liquid crystal cells having different Δnd values (Japanese Patent Laid-Open No. 64-49021).
Issue). However, this method had to sacrifice display quality.

In the conventional super twisted nematic liquid crystal display device, the contrast ratio is prioritized.
_OFF is set near V _th . For example, although a compensating liquid crystal is added to the super twisted nematic liquid crystal to improve the contrast ratio (Japanese Patent Laid-Open No. 2-130532), V _OFF is set near V _th as in the conventional case.

Further, phase plates are arranged above and below the twisted nematic type liquid crystal to make the threshold steep to improve the contrast ratio (Japanese Patent Laid-Open No. 61-89521).

As described above, the amount of change in the polarization state of the transmitted light due to the change in the orientation of the liquid crystal molecules increases as Δnd increases. Therefore, if Δnd is increased, a high contrast ratio should be obtained even in a high voltage region in which the orientation change of liquid crystal molecules is small. In JP-A-2-118516, Δnd is set to be 1.1 μm or more. However, the applied voltage value and Δn of the optical compensator and the driving liquid crystal
The relationship between d values is not specified.

[0012]

The response speed of the conventional super twisted nematic liquid crystal display device is 400 m.
At about s, the response speed is slow for displaying moving images on a television or the like, and scrolling is not possible even when used as a display device of a word processor or personal computer. There is also a problem that the display mouse disappears from the screen when the mouse is moved quickly.

An object of the present invention is to provide a liquid crystal display device capable of high time division driving by a matrix electrode, capable of obtaining a high contrast ratio and bright display, and having the above-mentioned mouse display and a high response speed. Especially.

[0014]

The gist of the present invention for achieving the above object is as follows.

(1) It has a liquid crystal cell sandwiching a nematic liquid crystal layer by a pair of substrates arranged opposite to each other, and a pair of polarizing plates arranged so as to sandwich the liquid crystal cell, and the substrate is provided with electrodes, and the nematic liquid crystal is provided. In a liquid crystal display device having a layer twist angle of 180 degrees or more, an optical anisotropy is provided between at least one of the liquid crystal cell and the incident light side polarization plate and between the liquid crystal cell and the emission light side polarization plate. The nematic liquid crystal is arranged such that the product Δnd of the optical anisotropy Δn of the nematic liquid crystal and the cell gap d is 1 μm or more, and the difference between the Δnd and the Δnd value of the optical anisotropic body is 0.2 μm or more. A liquid crystal display device, wherein the optical anisotropy Δn of the liquid crystal is 0.2 or more. (2) A substrate having a pair of electrodes arranged to face each other, a liquid crystal cell in which a nematic liquid crystal is held by the substrate, a twist angle of the nematic liquid crystal in the liquid crystal cell is 180 degrees or more,
A liquid crystal display device comprising a pair of polarizing plates arranged with the liquid crystal cell sandwiched between at least one of the liquid crystal cell and an incident light side polarizing plate and between the liquid crystal cell and an outgoing light side polarizing plate. And an optical anisotropy is arranged in the cell, and the product Δnd of the optical anisotropy Δn of the nematic liquid crystal and the cell gap d is 1
.mu.m or more, and the .DELTA.nd and .DELTA.n of the optical anisotropic body
A liquid crystal display device characterized in that the difference in d value is 0.2 μm or more and the optical anisotropy Δn of the nematic liquid crystal is 0.2 or more, the liquid crystal display device having a display function by a display mouse, The display of the display mouse is such that when the liquid crystal cell is normally open, the display mouse is displayed in a dark state,
A liquid crystal display device characterized in that a normally-closed display mouse is displayed in a bright state.

In the above, the twist angle of the nematic liquid crystal layer is preferably 180 to 300 degrees.

It is desirable that Δnd is large in order to obtain contrast and brightness in a high voltage region where the response is fast. In order to increase Δnd, it is sufficient to increase Δn or d, but an increase in d causes a decrease in the electric field in the liquid crystal cell and a decrease in response speed. Therefore, it is preferable to increase Δn.

In particular, in the liquid crystal display device having a time division function in which the substrate holding the liquid crystal layer has a matrix electrode, a liquid crystal display device having a high response, a high contrast ratio and a high transmittance can be obtained. To be

Further, in order to further increase the contrast of the liquid crystal display device having the matrix electrode, it is preferable that the substrate is provided with a light shielding layer at least in a portion where no electrode exists. The material of the light shielding layer is Cr, Cu, M
Metals such as n, Mo and Al are suitable. Further, an insulating layer should be provided between the light shielding layer and the electrode, and SiO ₂ and SiO are suitable as the material of the insulating layer.

[0020] Incidentally, as the nematic liquid crystal, which includes liquid crystal molecules having a tolan skeleton _{(R-C 6 H 4 -C≡C-} C 6 H 4 -R ') is particularly preferred.

Further, in the present invention, when the mouse is displayed, the mouse display is displayed in the dark state in the normally open state and in the normally closed state in the normally closed state so that the mouse can be moved at a high speed. It does not mean that the display mouse on the display screen disappears.

The display mouse is a kind of display on the display screen, and moves on the display screen in accordance with the movement of the mouse device. Usually, it is a symbol such as an arrow.

The above is due to the fact that if the time required to turn on the mouse display is shorter than the time required to extinguish it, it is difficult for the mouse to disappear even if the moving speed of the display mouse on the display screen is increased. In this case, if the time required for disappearance is long, the display mouse moves while leaving an afterimage.

Note that normally open means that when two voltages V _ON and V _OFF (V _ON > V _OFF ) are applied to the liquid crystal display to display a bright state and a dark state, V _ON
Is the dark state, and V _OFF is the bright state. In addition, the normally closed, the bright state in the V _ON, refer to the time of dark state in the V _OFF.

The S currently used in word processors and laptop computers currently in practical use.
In the TN type liquid crystal display device, the gap d of the liquid crystal cell
Is set to about 6 μm, and a liquid crystal material having an optical anisotropy Δn of about 0.13 is used. Therefore, Δnd of the liquid crystal cell
Is about 0.8 μm.

The transmittance and the contrast ratio in the bright state correlate with the phase difference change amount of the transmitted polarized light between the bright state and the dark state, and depend in a substantially proportional manner. The liquid crystal cell has both birefringence and optical rotation, and in this case, the amount of phase difference change is quantified by the Stokes parameters (S ₁ , S ₂ , S ₃ ). The Stokes parameter represents the polarization state of the polarized light, and the X-axis component E _X , Y-axis component E _Y of the electric field vector of the polarized light,
And the phase difference δ of both, [3], [4],
It is defined as in the formula [5].

[0027]

[Number 3] ^{_{S 1 = (E X 2 -E}} Y 2) / (E X 2 + E Y 2) ... [3]

[0028]

[Equation 4] S ₂ = 2E _X E _Y cos δ / (E _X ² + E _Y ² ) ... [4]

[0029]

[Equation 5] S ₃ = 2E _X E _Y sin δ / (E _X ² + E _Y ² ) ... [5] Transmitted light immediately before entering (S ₁ , S ₂ , S ₃ ) into the outgoing-side polarizing plate in a bright state. Polarization state of (S ₁ ′, S ₂ ′, S ₃ ′)
Letting A be the polarization state of the transmitted light in the dark state immediately before entering the exit side polarization plate, the phase difference change amount Δ is expressed by the equation [6].

[0030]

[Equation 6] Δ = 0.5 (1-S ₁ S ₁ ′ -S ₂ S ₂ ′ -S ₃ S ₃ ′) π [7] In addition, the transmission in the dark state using an optically anisotropic medium or the like. The polarized light is converted into linearly polarized light, and the output side polarizing plate is set to an angle that completely blocks this. At this time, the transmittance Δ% of the transmitted light in the bright state at the emission side polarizing plate is expressed by the formula [7].

[0031]

## EQU7 ## Δ% = 0.5 (1-S ₁ S ₁ ′ -S ₂ S ₂ ′ -S ₃ S ₃ ′) ... [8] In the conventional STN-LCD, the value of Δnd is 0.5. Since it is about 8 μm, the above Δ has a maximum value of about 0.5π at V _th where the amount of orientation change of the molecule is maximum. In the high voltage region of V _th, the amount of change in the alignment of the liquid crystal molecules decreases, so that Δ also decreases rapidly. Therefore, in the high voltage region where t _R and t _F decrease, a sufficient contrast ratio and bright state brightness cannot be obtained.

In the present invention, the Δnd of the liquid crystal cell is set to 1.0 μm or more to increase the amount of change in retardation due to the change in alignment of liquid crystal molecules. Therefore, a sufficient amount of phase difference change can be obtained even in the high voltage region of V _th .
In order to obtain the transmittance and the contrast ratio in the bright state which are comparable to or higher than those of the conventional STN-LCD, the value of Δ% may be set to 0.5.

The liquid crystal display device used in the word processor or the laptop computer is provided with a shift mechanism of the applied voltage which can be arbitrarily set by the user in accordance with the change of the threshold value due to the temperature change. The annual change of indoor temperature in Japan is 0-40 ° C. On the other hand, the half-value width of the contrast ratio-applied voltage curve of the liquid crystal display device of the present invention is sufficiently wide, and it is possible to cover the variation of the threshold value due to the temperature change.

In the present invention, an optical anisotropic body is disposed as an optical compensation layer at least between the liquid crystal cell and the incident light side polarizing plate and between the liquid crystal cell and the outgoing light side polarizing plate. However, the difference Δnd of the optical anisotropy used is such that the difference from the difference Δnd of the nematic liquid crystal layer is 0.2 μm or more. It performs a dark display in the high voltage region of the V _th, is to obtain a high contrast ratio in the high voltage region of the V _th.

The above is for the following reasons. The dark display is a state in which the transmitted light immediately before entering the exit side polarization plate is linearly polarized. In order to realize it, it is necessary that the apparent Δnd of the liquid crystal cell and the Δnd of the optical anisotropy match each other and cancel each other. In the conventional STN-LCD, Δnd of the liquid crystal cell and Δnd of the optically anisotropic substance are set to be equal. Therefore, in the low voltage region of V _th , the apparent Δnd of the liquid crystal cell is equal to the Δnd of the optically anisotropic body. Dark display is obtained in the low voltage region of V _th . Therefore, a high contrast ratio can be obtained only in the vicinity of V _th , and V _th
The contrast ratio rapidly decreases in the high voltage region of.

In the present invention, Δnd of the optical anisotropic body is set to a value different from Δnd of the liquid crystal cell. The apparent Δnd of the liquid crystal cell decreases as the driving voltage exceeds V _th and the liquid crystal molecules rise. In this case, however, the apparent Δnd and the optical anisotropy of the liquid crystal cell are increased when the driving voltage exceeds V _th. The Δnd of the body becomes equal. Therefore, dark display is obtained in the high voltage region of V _th , and a high contrast ratio is obtained.

As such an optically anisotropic material, for example, a uniaxially stretched polycarbonate film, polyvinyl alcohol film, polystyrene film, polyester film or the like can be used.

[0038]

In the above liquid crystal display device, V _OFF is set to a higher voltage side than the threshold value V _th (preferably 1.05 times or more of V _th ) in the applied voltage region where the orientation change of liquid crystal molecules is small. By driving, the response speed becomes faster. Further, since Δnd of the liquid crystal cell is set to 1 μm or more and the optical characteristics of the optical compensation layer and the absorption axis direction of the polarizing plate are optimized, sufficient contrast is obtained even when high time division driving is performed under the above conditions. The ratio can be obtained.

The rise time t _R of the time the response time was increased to V _OFF the applied voltage from V _ON, it is a fall time t _F when lowered to V _OFF from V _ON, in particular, V _OFF Is set to the high voltage side, t _R can be significantly shortened.

[0040]

【Example】

[Example 1] LQ1 manufactured by Hitachi Chemical Co., Ltd. was mounted on a glass substrate provided with a striped electrode having an electrode width of 0.8 mm and an electrode gap of 0.2 mm.
800 is applied by spin coating method at 250 ° C for 1
It was cured over time to form an alignment film having a film thickness of 700Å.
The film was subjected to an alignment treatment at 400 rpm, a feed rate of 10 cm / min, and a notch of 0.4 mm to obtain a substrate with an electrode having a pretilt angle of 4 degrees. Microbeads (manufactured by Sekisui Fine Chemical Co., Ltd.) are used by making two substrates face each other at a twist angle of 240 degrees.
Bonded using a sealant compounded with, substrate gap 6.
A 5 μm liquid crystal cell was prepared. The striped electrodes were formed so as to face each other to form an XY (matrix) electrode.

In the liquid crystal cell, a chiral agent S was added to a liquid crystal material DOP-00844 (manufactured by Rodick) having Δn = 0.23.
-811 (manufactured by Merck & Co.) in an amount of about 0.9% by weight was injected. A uniform super twisted nematic liquid crystal cell without domains was obtained. An AC voltage of 1 kHz was applied to the liquid crystal cell to measure the drive voltage dependence of the electric capacity of the liquid crystal cell. V _a = 2.42 V, C _a
= 92.4 μF, C ₀ = 77.6 μF, α = 220 μF /
It was V. From this, when the threshold voltage (V _th ) was obtained using the equation [1], it was V _th = 2.35 V.

Next, as shown in FIG. 2, a birefringence of 0.0041, a thickness of 110 μm, and a retardation (Δn) are provided as an optical compensation layer between the liquid crystal cell 1 and the incident light side polarizing plate 2.
d) A phase plate (optically anisotropic body) 4 having a value of 450 nm is inserted, and a birefringence of 0.0 is similarly provided between the phase plate 4 and the polarizing plate 3 on the outgoing light side.
048, thickness 115 μm, retardation value 550 n
A liquid crystal display device in which a m phase plate (optically anisotropic body) 5 was inserted was prepared. A polycarbonate film (manufactured by Nitto Denko Corporation) was used for the phase plates 4 and 5.

Using the liquid crystal display device, the alignment direction of liquid crystal molecules in the vicinity of the incident light side substrate 6 of the liquid crystal cell 1 is set to LQ.
1. The alignment direction LQ2 of the liquid crystal molecules 9 in the vicinity of the outgoing light side substrate 7 was observed from the opposite side 8 ′ of the light source 8. Each direction is shown in the schematic diagram of FIG. In FIG. 3, the absorption axis of the polarizing plate 2 is P2, the absorption axis of the polarizing plate 3 is P3, the optical axis of the phase plate 4 (stretching direction) F4, and the optical axis of the phase plate 5 (stretching direction) F5.

FIG. 4 shows the contrast ratio when the liquid crystal display device is driven at a duty of 1/200 using an AC electric field of 1 kHz. At 2.61 V (V _th × 1.11), the peak value of the contrast ratio is 15 and the transmittance is 2
It is 0%. Further, when V _OFF is set to V _th × 1.11 and the response time at 22 ° C. is measured, the rise time t _R = 70 ms and the fall time t _F = 200 ms.

At this time, t _R and t _F are defined as follows. When the capacitance of the liquid crystal cell at V _ON and V _OFF is C _ON and C _OFF (V _ON > V _OFF ), the drive voltage is V
When switching from _OFF to V _ON , the time required for the amount of change in the capacitance of the liquid crystal cell to reach 0.9 (C _ON -C _OFF ) is t _R , and similarly, the drive voltage is changed from V _ON to V _OFF. When switched to, the amount of change in the capacitance of the liquid crystal cell is 0.9 (C _ON-
The time required to reach C _OFF ) was defined as t _F.

At V _OFF (V _th × 1.11), the Stokes parameters (S ₁ , S ₂ , S ₃ ) of the transmitted light having a wavelength of 550 nm were measured immediately before the incidence on the exit side polarizing plate.
_{S 1 = -0.55, S 2 =} 0.88, was S ₃ = 0.44. V _ON when driven at 1/200 duty (V _th ×
1.19), the Stokes parameter
When (S ₁ ′, S ₂ ′, S ₃ ′) was measured, S ₁ ′ =
0.28 was _{S 2 '= 068, S 3} ' = -0.73.
At this time, 0.5 × (1-S ₁ S ₁ ′ -S ₂ S ₂ ′ -S ₃ S ₃ ′)
= 0.901.

Comparative Example 1 In the liquid crystal display device of Example 1, when V _OFF was set to V _th × 1.00 and the response time at 22 ° C. was measured, the rise time t _R = 300.
ms, the fall time t _F = 230 ms.

[Comparative Example 2] In the liquid crystal display device of Example 1, the phase plate on the light source side was changed to one having a Δnd of 0.70 μm, and the difference between Δnd of the nematic liquid crystal layer and Δnd of the optically anisotropic substance was changed. It was set to 0.07 μm.

As a result, the minimum value of the brightness transmittance is 2.33.
It was obtained at V and was 2.1%. Also, the maximum contrast ratio was obtained at 2.33 V and was 7: 1. This liquid crystal display device was driven at 2.33 V at which the maximum contrast ratio was obtained, that is, 1.00 times the threshold voltage, and the response time at 22 ° C. was measured. Rise time t _R = 350 ms, fall time t _F = 180 ms
Met. The response time was significantly longer than that of Example 1. Even if the above 81a, 82a, 81b, and 82b were set to values other than the above, the maximum contrast ratio was obtained at or around 1.00 times the threshold voltage. In any case, the response time when driven at the voltage at which the maximum contrast ratio is obtained is 1.9 to 2.0 times that of the first embodiment.
It was double.

[Comparative Example 3] In the liquid crystal display device of Example 1, the nematic liquid crystal material was used and the birefringence was 0.107.
It was replaced with RDP-91206-1 manufactured by Roddick. V _th of this liquid crystal display device was measured and found to be 1.2
It was 4V. The phase plate on the light source side of the phase plate is Δn
The d was changed to 0.40 μm, and the phase plate on the emission side was removed. Δnd of the nematic liquid crystal layer was 0.64 μm, and the difference between Δnd of the nematic liquid crystal layer and Δnd of the optically anisotropic substance was 0.25 μm.

The maximum value of luminance transmittance was obtained at 1.35 V and was 3.6%. The minimum value of brightness transmittance is 1.4
Obtained at 5V, 0.8%. Also, the maximum contrast ratio was obtained at 1.35 V and was 4: 1. This liquid crystal display device was driven at 1.35 V at which the maximum contrast ratio was obtained, that is, 1.09 times the threshold voltage, and the response time at 22 ° C. was measured. The rise time t _R = 70 ms and the fall time were measured. t _F = 190 ms
Met. Thus, although the response time was almost the same as that of Example 1, the brightness transmittance and the maximum contrast ratio of bright display were significantly lowered. When V _OFF (V _th × 1.09) was applied, the Stokes parameters (S ₁ , S ₂ , S ₃ ) of the transmitted light immediately before entering the outgoing-side polarizing plate were measured and found to be S ₁ =-
0.30, S ₂ = -0.88, was S ₃ = 0.15. 1 /
V _ON when driven at 200 duty (V _th × 1.17)
In the same manner, the Stokes parameters (S ₁ ′, S
₂ ′, S ₃ ′) was measured, S ₁ ′ = −0.61,
S ₂ ′ = −0.65 and S ₃ ′ = −0.46. At this _{time, 0.5 × (1-S 1} S 1 '-S 2 S 2' -S 3 S 3 ') =
It was 0.157.

[Comparative Example 4] In the liquid crystal display device of Example 1, the nematic liquid crystal material was used and the birefringence was 0.107.
In place of RDP-91206-1 manufactured by Roddick,
The layer thickness of the nematic liquid crystal layer was 12 μm. The V _th of this liquid crystal display device was measured and found to be 1.25 V. Δnd of the nematic liquid crystal layer was 1.28 μm, and the difference between Δnd of the nematic liquid crystal layer and Δnd of the optically anisotropic substance was 0.27 μm.

The maximum value of luminance transmittance was obtained at 1.36 V and was 16.4%. The minimum value of luminance transmittance is 1.
Obtained at 45V, 0.8%. Also, the maximum contrast ratio was obtained at 1.35V and was 16: 1.
Met. This liquid crystal display device was driven at 1.35 V at which the maximum contrast ratio was obtained, that is, 1.09 times the threshold voltage, and the response time at 22 ° C. was measured. Rise time t _R = 360 ms, fall time t _F = 76
It was 0 ms. As described above, although the brightness transmittance and the maximum contrast ratio of the bright display are almost the same as those in Example 1, the response time is almost doubled.

[Embodiment 2] The twist angle between the liquid crystal cell substrates 6 and 220 is 220 degrees, and the concentration of the chiral agent in the liquid crystal material is 0.8.
A liquid crystal display device of the present invention was produced in the same manner as in Example 1 except that the amount was set to 5% by weight. V _th was 2.37V.

As the phase plate 4 of FIG.
0 nm and retardation 550 as the phase plate 5
The thing of nm was used. These directions are shown in FIG. 1k
FIG. 6 shows the dependency of the applied voltage value on the transmittance when the device is driven at 1/200 duty using an AC electric field of Hz.

The peak value of the contrast ratio is 2.68V (V
_th × 1.13) is 9 and the transmittance is 16%. Also, V
_OFF = V _th × 1.13 Response time measured by setting t _R =
90 ms, t _F = 130 ms.

Comparative Example 5 The liquid crystal display device of Example 2 is
When the response time (22 ° C.) was measured with V _OFF = V _th , it was t _R = 250 ms and t _F = 200 ms.

Example 3 A liquid crystal display device of the present invention was prepared in the same manner as in Example 1 except that the twist angle was 260 ° and the concentration of the chiral agent in the liquid crystal material was set to about 1% by weight. V _th was 2.38V.

Retardation of 660 nm as the phase plate 4
Further, as the phase plate 5, one having a retardation of 550 nm was used. These directions are shown in FIG. FIG. 8 shows the dependence of the transmittance on the applied voltage value when driven at a duty of 1/200 using an AC electric field of 1 kHz.

The peak value of the contrast ratio is 2.59 V (V
_th * 1.09) is 13, and the transmittance is 16%. Also, V
_The response time measured with _OFF = V _th × 1.09 is t
_R = 60 ms and t _F = 200 ms.

Comparative Example 6 The liquid crystal display device of Example 3 is
When the response time (22 ° C.) was measured with V _OFF = V _th , t _R = 500 ms and t _F = 210 ms.

[Example 4] A liquid crystal display device of the present invention was prepared in the same manner as in Example 1 except that the twist angle was 200 degrees and the concentration of the chiral agent in the liquid crystal material was set to about 0.8% by weight. . V _th was 2.35V.

Retardation of 580 nm as the phase plate 4
The phase plate 5 having a retardation of 410 nm was used. These directions are shown in FIG. FIG. 10 shows the dependency of the applied voltage value on the transmittance when driven at a duty of 1/200 using an AC electric field of 1 kHz.

The peak value of the contrast ratio is 2.66V (V
_th × 1.13) 6, and the transmittance is 15%. Also, V
_The response time measured by setting _OFF = V _th × 1.13 is t
_R = 90 ms and t _F = 100 ms.

[Comparative Example 7] The liquid crystal display device of Example 4 is
When the response time (22 ° C.) was measured with V _OFF = V _th , t _R = 200 ms and t _F = 190 ms.

[Embodiment 5] A mixture having a twist angle of 240 degrees and RDP-00844 and RDP-91206-1 (both manufactured by Rodic Corporation) as a liquid crystal material in a weight ratio of 4: 1 (Δ
A liquid crystal display device of the present invention was prepared in the same manner as in Example 1 except that n = 0.21) was used. V _th is 2.13V
Met.

Retardation 350 nm as the phase plate 4
Was used as the phase plate 5 having a retardation of 550 nm. These directions are shown in FIG. FIG. 12 shows the dependence of the transmittance on the applied voltage value when driven at a duty of 1/200 using an AC electric field of 1 kHz.

The contrast ratio is 2.34 V (V _th × 1.1
0), the peak value is 10 and the transmittance is 19%. Also,
The response time measured by setting V _OFF = V _th × 1.10.
t _R = 100 ms and t _F = 180 ms.

Comparative Example 8 In the liquid crystal display device of Example 5, the response time (22 ° C.) was measured with V _OFF = V _th , and it was t _R = 330 ms and t _F = 190 ms.

[Embodiment 6] Twist angle 240 °, same cell gap 7.2 μm, RDP-0084 as liquid crystal material
A liquid crystal display device of the present invention was prepared in the same manner as in Example 1 except that a mixture of 4 and RDP-91206-1 in a weight ratio of 3: 2 (Δn = 0.18) was used.

V _th was 2.01 V.

Retardation 500 as the phase plates 4 and 5
The thing of nm was used. These directions are shown in FIG. 1
FIG. 14 shows the dependency of the applied voltage value on the transmittance when driven at 1/200 duty using an AC electric field of kHz.

The contrast ratio is 2.19 V (V _th × 1.0
In 9), the peak value is 12 and the transmittance is 21%. Also,
The response time measured by setting V _OFF = V _th × 1.09 is
t _R = 90 ms and t _F = 190 ms.

Comparative Example 9 In the liquid crystal display device of Example 6, the response time (22 ° C.) was measured with V _OFF = V _th , and it was t _R = 400 ms and t _F = 210 ms.

Example 7 A liquid crystal display device of the present invention was prepared in the same manner as in Example 1 except that a liquid crystal cell provided with a black matrix was used. V _th was 2.35V.

The same phase plates as in Example 1 were used as the phase plates 4 and 5. These directions are shown in FIG. FIG. 15 shows the dependence of the transmittance on the applied voltage value when driven at a duty of 1/200 using an AC electric field of 1 kHz.

The contrast ratio is 2.61 V (V _th × 1.1
In 1), the peak value is 18 and the transmittance is 17%. Also, V
_The response time measured by setting _OFF = V _th × 1.11 is t
_R = 70 ms and t _F = 210 ms.

[Example 8] A liquid crystal display device of the present invention was prepared in the same manner as in Example 2 except that a liquid crystal cell provided with a black matrix was used. V _th was 2.36V.

The same phase plates 4 and 5 as in Example 2 were used. FIG. 16 shows the dependence of the transmittance on the applied voltage value when driven at a duty of 1/200 using an AC electric field of 1 kHz.

The contrast ratio is 2.67 V (V _th × 1.1
In 3), the peak value is 12 and the transmittance is 13%. Also,
The response time measured by setting V _OFF = V _th × 1.13 is
t _R = 90 ms and t _F = 130 ms.

Example 9 A liquid crystal display device of the present invention was prepared in the same manner as in Example 3 except that a liquid crystal cell provided with a black matrix was used. V _th was 2.38V.

The same phase plates 4 and 5 as in Example 2 were used. FIG. 17 shows the dependency of the applied voltage value on the transmittance when driven at a duty of 1/200 using an AC electric field of 1 kHz.

The contrast ratio is 2.59 V (V _th × 1.0
In 9), the peak value is 16 and the transmittance is 13%. Also,
The response time measured by setting V _OFF = V _th × 1.09 is
t _R = 60 ms and t _F = 200 ms.

The driving voltage of the liquid crystal display device of the above-mentioned embodiment is 1. The driving voltage of the conventional super twisted liquid crystal display device.
Since it is about 05 to 1.3 times, the conventionally used drive circuit can be used as it is.

[Embodiment 10] The cell gap is 6.5 μm.
In a liquid crystal cell of a liquid crystal display device for a notebook type personal computer, a chiral agent S is added to a liquid crystal RDP-00844 (made by Rodick Co.) having an optical anisotropy Δn of 0.23.
-811 (manufactured by Merck & Co.) in an amount of about 0.9% by weight was injected. The V _th of the cell was 2.35V.

A phase plate 4 having a retardation of 580 nm and a phase plate 5 having a retardation of 500 nm were prepared. The azimuth angles of the liquid crystal cell 1, the polarizing plates 2, 3 and the phase plates 4 and 5 are arranged as shown in FIG. This liquid crystal display device uses an alternating electric field of 1 kHz,
FIG. 21 shows the applied voltage dependency of the transmittance when driven at 1/200 duty.

The peak value of the contrast ratio is 2.65 V (V
_th × 1.12), and the value is 15. V
_{When OFF} , the peak value of contrast is obtained V _th × 1.1
The response time measured by setting to 2 is t _R = 80 ms,
t _F = 140 ms. The liquid crystal display device was connected to the notebook personal computer to drive a mouse device. On-screen display Mouse movement speed is 3 cm /
In the case of s, the displayed mouse image was the same as that at rest. When the moving speed was 6 cm / s, a tail having a length of about 1 cm was drawn on the displayed mouse image, but the mouse image itself was not blurred. Furthermore, when the moving speed was set to 10 cm / s, the tail of the displayed mouse image extended further, but no particular abnormality was observed in the mouse image itself.

When scrolling at a speed of 3 lines / s, the display screen seemed to be the same as when it was stationary. When scrolling at 7 lines / sec, the display of the non-selected portion between the lines did not return to a completely bright state, and became a dim display.
However, the display could be read. Further, when scrolling at 10 lines / s, the non-selected portion between the lines became darker, but the display itself could be read.

[Comparative Example 10] A liquid crystal material RDX-70 having an optical anisotropy Δn of 0.13 was added to the liquid crystal cell of the liquid crystal display device for a notebook personal computer of Example 10.
11 (manufactured by Rodic) was mixed with about 8% by weight of a chiral agent S-811 (manufactured by Merck) and injected. V _th
Was 2.25V.

Polarizing plates 2 and 3 were arranged before and after this liquid crystal cell. The absorption axis P2 of the polarizing plate 2 and the absorption axis P3 of the polarizing plate 3 are aligned with the alignment direction LQ1 of the liquid crystal molecules near the incident light side substrate 6 of the liquid crystal cell 1, and the alignment direction LQ2 of the liquid crystal molecules near the emission light side substrate 7. The angles are shown in FIG.

FIG. 1 shows the dependency of the transmittance on the applied voltage when driven at a duty of 1/200 using an AC electric field of 1 kHz.
9 shows. The peak value of the contrast ratio is 2.29 V (V _th
X 1.02) and the value is 7. V _OFF
Was set to a voltage value at which the peak value of the contrast ratio was obtained, and the response time was measured. As a result, t _R = 280 ms, t
_F = 130 ms.

This liquid crystal element was connected to a notebook personal computer to drive a mouse device. The moving speed of the display mouse on the screen was changed to move it horizontally and vertically, and the state of the image of the mouse on the display screen was investigated.

Display speed on the screen The moving speed of the mouse is about 3
At cm / s, the displayed mouse did not differ from the static image. Next, when the moving speed is set to about 6 cm / s,
The display mouse became unclear and was not displayed at 10 cm / s.

Even when scrolling at 3 lines / s, the display screen did not change from a still image, but at 7 lines / s, the display screen became unclear, and at 10 lines / s, the display screen could not be identified at all. It was

[0095]

According to the present invention, the response time of the liquid crystal display device can be shortened by setting the drive voltage on the higher voltage side than the threshold voltage (V _th ). In addition, a display with a high contrast ratio can be obtained. In particular, it is possible to provide a word processor or personal computer that can be used as a mouse for the display device.

[Brief description of drawings]

FIG. 1 is a graph showing the definition of response time according to the present invention.

FIG. 2 shows a liquid crystal cell, a phase plate, a polarizing plate,
It is a schematic diagram which shows arrangement | positioning of a light source etc.

FIG. 3 is a schematic diagram showing a relationship of light absorption axes of each component viewed from the outgoing light side of FIG.

FIG. 4 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 1.

FIG. 5 is a schematic diagram showing the relationship of the light absorption axes of each component viewed from the outgoing light side of the liquid crystal cell in the second embodiment.

FIG. 6 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 2.

FIG. 7 is a schematic diagram showing a relationship of light absorption axes of respective components viewed from an outgoing light side of a liquid crystal cell in Example 3.

FIG. 8 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 3.

FIG. 9 is a schematic diagram showing the relationship of the light absorption axes of each component as seen from the outgoing light side of the liquid crystal cell in Example 4.

FIG. 10 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 4.

FIG. 11 is a schematic diagram showing the relationship of the light absorption axes of the respective components as seen from the outgoing light side of the liquid crystal cell in Example 5.

FIG. 12 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 5.

FIG. 13 is a schematic diagram showing a relationship of light absorption axes of each component viewed from the outgoing light side of the liquid crystal cell in Example 6.

FIG. 14 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 6.

15 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 7. FIG.

16 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 8. FIG.

FIG. 17 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 9.

FIG. 18 is a schematic diagram showing the relationship of the light absorption axes of the respective components as seen from the outgoing light side of the liquid crystal cell in Example 10.

19 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 10. FIG.

FIG. 20 is a schematic diagram showing the relationship of the light absorption axis of each component viewed from the outgoing light side of the liquid crystal cell in Example 11.

FIG. 21 is a graph showing the relationship between the transmittance and the contrast ratio with respect to the applied voltage of the liquid crystal display device of Example 11.

[Explanation of symbols]

1 ... Liquid crystal cell, 2, 3 ... Polarizing plate, 4, 5 ... Phase plate, 6,
7 ... Substrate, 8 ... Light source, 9 ... Liquid crystal molecule, 10 ... Power supply, LQ
1 ... Alignment direction of liquid crystal molecules near the substrate 6, LQ2 ... substrate 7
Orientation direction of liquid crystal molecules in the vicinity, P2 ... Absorption axis of polarizing plate 2,
P3 ... Absorption axis of polarizing plate 2, F4 ... Optical axis of phase plate 4 (stretching direction), F5 ... Optical axis of phase plate 5 (stretching direction).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Kikuchi 3300 Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Devices Division

Claims (8)

[Claims] 1. A liquid crystal cell sandwiching a nematic liquid crystal layer between a pair of substrates arranged opposite to each other, and a pair of polarizing plates arranged so as to sandwich the liquid crystal cell, the substrate comprising electrodes.
The twist angle of the nematic liquid crystal in the liquid crystal cell is 18
In the liquid crystal display device having an angle of 0 degree or more, an optically anisotropic body is disposed between at least one of the liquid crystal cell and the incident light side polarization plate and between the liquid crystal cell and the emission light side polarization plate, and the nematic The product Δnd of the optical anisotropy Δn of the liquid crystal and the cell gap d is 1 μm or more, and the difference between the Δnd and the Δnd value of the optical anisotropic body is 0.2 μm.
As described above, the optical anisotropy Δn of the nematic liquid crystal is 0.2.
A liquid crystal display device characterized by the above. 2. The nematic liquid crystal layer has a twist angle of 18
The liquid crystal display device according to claim 1, wherein the liquid crystal display device has an angle of 0 to 300 degrees. 3. The liquid crystal display device according to claim 1, wherein the electrodes arranged to face each other are matrix electrodes. 4. The nematic liquid crystal in the liquid crystal cell has a twist angle of 180 to 300 degrees, the opposed electrodes are matrix electrodes, and a light shielding layer is provided on at least a portion of the substrate surface where no electrode exists. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device. 5. The liquid crystal display device according to claim 1, wherein the nematic liquid crystal layer contains liquid crystal molecules having a tolan skeleton. 6. The display device has an electric capacity C ₀ when V = 0 in an AC electric field having a frequency of 1 kHz, a voltage V _{a at} which _a change of the electric capacity with a rise in voltage becomes maximum, C is the electric capacity when the change with the voltage rise of the electric capacity becomes maximum
_a , where the rate of change of the electric capacity when the change of the electric capacity with the increase in voltage is maximum is α, the drive voltage of the display device is lower than the threshold voltage V _th defined by the formula [1]. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set to a high voltage side. ## EQU1 ## V _th = (C ₀ −C _a + αV _a ) / α ... [1] 7. The liquid crystal display device has a display function of a display mouse, and the display of the display mouse is displayed in a dark state when the liquid crystal cell is normally open.
The liquid crystal display device according to claim 1, wherein the display mouse is configured to be displayed in a bright state in a normally closed state. 8. The polarization state of the transmitted light immediately before entering the exit side polarizing plate is represented by Stokes parameters, and the values in the bright state (S ₁ , S ₂ , S ₃ ) and the values in the dark state are set.
_2. The liquid crystal display device according to claim 1, wherein (S ₁ ′, S ₂ ′, S ₃ ′) have the relationship of the formula [2]. [Number 2] _{0.5 <0.5 (1-S 1} S 1 '-S 2 S 2' -S 3 S 3 ') ... [2]