JP2000298277A - Liquid crystal display element and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reflection-type liquid crystal display device which can be driven at a rather low voltage and which has superior fast responding property by controlling the twist angle and liquid crystal alignment angle of the liquid crystal layer to a specified angle and angle range, respectively. SOLUTION: This liquid crystal display device consists of a liquid crystal layer 102 held between a transparent electrode and a reflection electrode 101, a plurality of pixel circuits for driving the liquid crystal layer 102, and peripheral circuits for driving each pixel circuit. The liquid crystal layer 102 is formed to have the upper side liquid crystal alignment direction 108, a lower side liquid crystal alignment direction 109, a twisting angle between these directions, and a liquid crystal alignment angle 111 which is the angle, for example, between the upper side liquid crystal alignment direction and the vertical direction. The twisting angle of the liquid crystal layer 102 is controlled to 90 deg. and the liquid crystal alignment angle 111 is set in the range of 0 deg. to 30 deg. or of 90 deg. and 120 deg.. More preferably, the liquid crystal alignment angle is controlled to be in the range of 10 deg. to 20 deg. or of 100 deg. to 110 deg.. Thereby, the obtd. device has little voltage dependence on chromaticity and can be driven at a rather low voltage.

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 reflection type liquid crystal display device which forms an image by receiving light emitted from a light source.

[0002]

2. Description of the Related Art A liquid crystal display mode that has been put to practical use in a reflection type liquid crystal display device for a liquid crystal projector includes a VAN (Ver.
tically Alligned Nematic) mode and HFE (Hybrid Feil)
d Effect) mode.

The VAN mode is a system using a liquid crystal material having a negative dielectric anisotropy and having a tilted homeotropic alignment in which the liquid crystal alignment is slightly inclined from a direction perpendicular to the substrate surface.

A rubbing method is most frequently used as a liquid crystal alignment method for a liquid crystal display. However, when the rubbing method is used to realize tilt homeotropic alignment, in-plane unevenness of the tilt angle occurs, and the threshold voltage is increased. It is not practical because of unevenness. Therefore, as a method for stably realizing the inclined homeotropic alignment, an oblique evaporation method of silicon oxide is applied.

However, the oblique deposition method of silicon oxide can control the tilt angle relatively uniformly in the plane, but is unstable as a process. The superiority of the general liquid crystal display, to which the oblique deposition method of silicon oxide was originally applied, has been converted to the rubbing method.

Several reflective liquid crystal display modes using twisted nematic alignment that can be aligned by a rubbing method have been proposed. As the liquid crystal material, a material having a positive dielectric anisotropy (P-type liquid crystal material) is used. These can be roughly classified into two types: normally black type and normally white type.

The normally black type is a display system in which black display is performed on the low voltage side, and the reflectance increases as the voltage increases, and the reflectance becomes maximum at a certain voltage. On the contrary, the normally white type displays white on the low voltage side,
This is a display method in which the reflectance decreases with an increase in voltage and black display is performed on the high voltage side.

As a report example of a normally black liquid crystal display mode, there is an HFE (Hybrid Field Effect) mode, Opt. Eng. 14, p. 217 (1995) describes the details. The drawback of this display mode is that the chromaticity has a large voltage dependency. Specifically, when a white gray scale is displayed, it is colored and visually recognized as a different color for each gradation. Further, it is necessary to optimize the liquid crystal material or cell gap for each of the RGB colors. That is, a different liquid crystal display element is required for each RGB. This is a disadvantageous condition from the viewpoint of mass productivity.

Further, in the reflective display mode, the display mode is inevitably the birefringent display mode, so that the change in the absolute amount of the retardation of the cell greatly affects the luminance fluctuation. This effect is particularly large in dark display or halftone display, and adversely affects display characteristics as a decrease in contrast ratio or uneven brightness.

[0010] The retardation referred to here is:
The product of the thickness of the liquid crystal layer and the refractive index anisotropy of the liquid crystal material,
A physical quantity that causes a relative delay in the phase of polarized light.

When a P-type liquid crystal material is used, the retardation of the cell is maximum at a voltage of 0 Vrms, and the effective retardation is reduced by applying a voltage. That is, a change in retardation with respect to a certain temperature change or a change in the cell gap is large on the low voltage side, and thus the luminance change is also large on the low voltage side.

Therefore, in order to obtain stable display characteristics with respect to changes in temperature or cell gap when a P-type liquid crystal material is used, it is not advisable to use normally black in which black display is performed on the low voltage side. It is considered that it is desirable to use normally white in which black display is performed on the side.

Alternatively, the required retardation of the liquid crystal layer is as large as about 0.54 μm. This is because when the cell gap is reduced to 3 μm or less in order to speed up the liquid crystal response, an extremely large refractive index anisotropy (Δ
The liquid crystal material of (n) (Δn> 0.18) is required, which is not practical. That is, it can be said that it is not suitable for high-speed response.

Here, the importance of high-speed response will be described. High-speed response in a display is an important factor as described below. For example, an image signal in a personal computer is usually composed of an image signal of at least 60 frames per second.

Therefore, when a moving image is displayed on a display of a personal computer, it is necessary to ensure that the display follows the image signal in order to reduce the time corresponding to one frame or less, that is, 1/60 seconds = 16.7 milliseconds or less. The liquid crystal needs to respond to the image signal. If the response time of the liquid crystal exceeds the time corresponding to one frame, there is a possibility that an image different from the image signal is displayed.

Such an image different from the actual image signal is recognized as an afterimage, which should not be seen originally in the moving direction of the image, especially in a moving image. Such afterimages significantly degrade image quality. Therefore, in order to realize a liquid crystal display with good image quality, it is necessary to select a liquid crystal display mode capable of high-speed liquid crystal response.

On the other hand, as a normally white reflective twisted nematic liquid crystal display mode, TN-ECB (Twis
ted Nematic-Electrically Controlled Birefringenc
e) mode, MTN (Mixed Twisted Nematic) mode, SCT
An N (Self-Compensated Twisted Nematic) mode has been proposed. JP-A-10-090731 describes the SCTN mode. TN-EC in Japan Display '89, p.192 (1989)
There is description of B mode. Appl. Phys. Lett. 68, p. 1455
(1996) describes the MTN mode.

[0018]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reflection type liquid crystal display device which has a small voltage dependency of chromaticity, can be driven at a relatively low voltage, and is excellent in high-speed response. To provide a liquid crystal display device.

[0019]

In order to achieve the above object, a feature of the liquid crystal display device according to the present invention is that a twist angle of a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode is 90 °. , And the liquid crystal alignment angle is from 0 ° to 30 °
Or in the range of 90 ° to 120 °.

Specifically, the present invention provides the following elements and devices. The present invention provides a liquid crystal display device comprising: a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode; a plurality of pixel circuits for driving the liquid crystal layer; and a peripheral circuit for driving each of the pixel circuits. Has a twist angle of 90 ° and a liquid crystal alignment angle of 0 ° to 30 ° to 90 ° to 120 °.
° is provided within the range.

Preferably, the liquid crystal orientation angle is from 10 °.
It is in the range of 20 ° to 100 ° to 110 °.

The present invention also provides a liquid crystal display device having a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode, a plurality of pixel circuits for driving the liquid crystal layer, and a peripheral circuit for driving each of the pixel circuits. In the above, the twist angle of the liquid crystal layer is 90 °, and the liquid crystal alignment angle is in the range of 10 ° to 20 ° to 100 ° to 110 °, and the wavelength-normalized retardation of the liquid crystal layer is 0.45 to 0.55. A liquid crystal display element characterized by the following is provided.

According to the present invention, there is provided a liquid crystal display device having a liquid crystal display element for phase-modulating incident light and reflecting the same to output an image, wherein the liquid crystal display element comprises a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode. And a plurality of pixel circuits for driving the liquid crystal layer, and a peripheral circuit for driving each of the pixel circuits, wherein a twist angle of the liquid crystal layer is 73 ° or more and 100 ° or less, and a wavelength standard of the liquid crystal layer. 0 retardation
Set to 44 or more and 0.6 or less, and further set the thickness of the liquid crystal layer to 2.4
Provided is a liquid crystal display device characterized in that the response time of liquid crystal is 16.7 ms or less by setting the refractive index anisotropy of the liquid crystal material to 0.1 μm or less and 0.1 or more.

The present invention also provides a liquid crystal display device having a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode, a plurality of pixel circuits for driving the liquid crystal layer, and a peripheral circuit for driving each of the pixel circuits. In which the twist angle of the liquid crystal layer is set to 73 ° or more and 100 ° or less, and an image is displayed at a driving voltage of 3 to 6 Vrms.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal display device according to an embodiment of the present invention and a liquid crystal display device using the same will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a diagram showing a relative relationship between optical axes of respective optical elements in a liquid crystal display element according to an embodiment of the present invention. In the figure, for simplicity, only the reflection plate 101 and the liquid crystal layer 102 of the liquid crystal display device are illustrated. Further, a polarizing beam splitter 103 is used as a polarizer and analyzer.

In the liquid crystal layer 102, a side closer to the reflector 101 is referred to as a lower side, and a side farther from the reflector 101 is referred to as an upper side. The configuration of the liquid crystal layer 102 includes an upper liquid crystal alignment direction 108, a lower liquid crystal alignment direction 109, a twist angle between them (twist angle 110), and an angle formed between the upper liquid crystal alignment direction 108 and, for example, a vertical direction. It is represented by a certain liquid crystal orientation angle 111.

Although not shown, retardation, which is a product of the thickness of the liquid crystal layer 102 and the refractive index anisotropy of the material of the liquid crystal layer 102, is also an important factor.

The polarizing beam splitter 103 has a structure in which two prisms are bonded, and the bonding interface
At 112, it has a characteristic of being transmitted or reflected by a polarized light component. Only the horizontal polarization component 107 of the incident light 104 passes through the polarization beam splitter and reaches the liquid crystal display device.

This light undergoes phase modulation when passing through the liquid crystal layer 102, is reflected by the reflection plate 101, passes through the liquid crystal layer 102 again, and returns to the polarization beam splitter 103. The polarization component parallel to the horizontal polarization component 107 is the polarization beam splitter 1
03 passes through and becomes return light 105 to the lamp.

On the other hand, the polarization component orthogonal to the horizontal polarization component 107 is applied to the bonding interface 112 of the polarization beam splitter 103.
And reflected by a screen (not shown).
It becomes 6.

The intensity ratio of the return light 105 to the lamp and the light 106 projected on the screen varies depending on the voltage applied to the liquid crystal layer 102. When the intensity of the light 106 projected on the screen becomes maximum, the white display state occurs. On the contrary, when the intensity of the returning light 105 to the lamp becomes maximum, the black display state is established.

Here, the result of obtaining the desired parameters of the liquid crystal cell will be described. As parameters of the liquid crystal cell,
Retardation, which is the product of the cell gap, which is the thickness of the liquid crystal cell, and the refractive index anisotropy of the liquid crystal material, and the twist angle
110 and the liquid crystal orientation angle 111. However, in the following calculation, a wavelength-normalized retardation in which retardation is normalized by wavelength is used.

In the method described below, first, the above 3
One parameter condition is narrowed down, and then each parameter is optimized in more detail with respect to the contrast ratio and the chromaticity change.

The light propagation matrix in the liquid crystal layer when no voltage is applied can be analytically given. Therefore,
First, the optical characteristics are optimized when no voltage is applied, and the parameter conditions are roughly narrowed down.

It is known that the twisted nematic liquid crystal layer is well described by a model in which n layers of birefringent media are laminated while shifting the optical axis by φ / n. Especially n →
The propagation matrix at the time of _∞ is called a Jones matrix J _{与 え} and is given by the following equation (Equation 1).

[0037]

(Equation 1)

However,

[0039]

(Equation 2)

[0040]

(Equation 3)

[0041]

(Equation 4)

[0042]

(Equation 5)

Here, φ is the twist angle, d is the cell gap, Δn is the refractive index anisotropy, and λ is the wavelength.

In the case of the reflection type element, since the optical path passes through the liquid crystal layer twice, the propagation matrix J _R∞ can be described as the following equation (Equation 6).

When these variables are used, the retardation can be described as d △ n, and the wavelength-normalized retardation can be described as d △ n / λ.

[0046]

(Equation 6)

Here, R (φ) is a rotation matrix, and _Re is an inversion matrix. When this is used to calculate the reflectance R when the polarization arrangement is orthogonal Nicols, the following equation (Equation 7) is obtained.

[0048]

(Equation 7)

Here, θ is the liquid crystal alignment angle. Reflectivity
In order to make R the maximum (R = 1),
It may be set to 0.

FIG. 2 shows a solution that satisfies R = 1 when the twist angle φ and d △ n / λ are parameters (solid line in FIG. 2). That is, it is understood that the condition that the efficiency becomes 100% exists only when the twist angle is 73 ° or less. Also,
At a twist angle φ <73 °, it can be seen that the optimum condition of d に n / λ branches into two branches as shown by B1 and B2 in FIG.

On the other hand, the optimum condition for the maximum efficiency at a twist angle φ> 73 ° is:

[0052]

(Equation 8)

[0053]

(Equation 9)

Is obtained by solving (Equation 8),
The solution satisfying (Equation 9) is shown by a dotted line (B3) in FIG.

FIG. 3 shows the dependence of the liquid crystal alignment angle on the twist angle φ under the conditions shown in FIG. B1, B2 and B3 in FIG. 3 respectively correspond to B1, B2 and B3 in FIG. The same applies to the following drawings.

In the case where a liquid crystal display is used, generally, chromaticity changes to a considerable degree with respect to the drive voltage. Although it depends on the wavelength dispersion of the light source and the characteristics of the spectral optical system, it is necessary to suppress the voltage dependency of the chromaticity to some extent in order to make the specifications of the RGB panels the same.

FIG. 4 shows a calculation result of the chromaticity change amount △ (u′v ′) under the respective conditions shown in FIGS. The chromaticity change amount 色 (u′v ′) is, as shown in FIG. 11, the applied voltage V ₁ of the locus of the chromaticity of the emitted light at each drive voltage on the u′-v ′ chromaticity diagram. It was defined as the amount of chromaticity change from (voltage corresponding to reflectance 1%) to V ₉₉ (voltage corresponding to reflectance 99%).

The wavelength range of the incident light is 400 nm to 700 nm.
The maximum allowable value of Δ (u'v ') largely depends on the design of the projection optical system and cannot be unconditionally determined. However, the maximum allowable value of the transmission type twisted nematic (TN) is approximately 0.07 to 0.07. 0.
It is considered to be around 08.

Under the condition on B1, △ (u'v ') is 0.075 or more, and the voltage dependence of chromaticity is large. Moreover, it increases rapidly as the twist angle decreases. On the other hand, under the condition on B2, △ (u'v ') is constant at about 0.075 regardless of the twist angle. Further, under the condition on B3, △ (u'v ') decreases as the twist angle increases.

FIG. 5 shows a calculation result of the twist angle dependence of the driving voltage. Here, the drive voltage is a voltage when the reflectance is a reflectance corresponding to 1% (contrast ratio 100: 1) and 0.33% (contrast ratio 300: 1) of the maximum reflectance. A drive voltage of about 3 to 4 Vrms can be aimed under the conditions on B1 and B3, but a contrast ratio of 10
It was found that the driving voltage of 0: 1 was 4 Vrms or more, and the driving voltage of 300: 1 contrast ratio was 6.5 Vrms or more.

FIG. 6 shows a calculation result of the twist angle dependence of the light use efficiency. Here, the light utilization efficiency is a reflectance in which the wavelength range of the incident light is 400 nm to 700 nm and the visibility is taken into consideration. The parallel transmittance of the polarizer and analyzer is normalized to 100%. Therefore, the ideal light utilization efficiency is 100%
It is.

Under the conditions on B2, a light use efficiency comparable to that of the transmission type TN can be obtained. The reason why the light use efficiency under the condition on B1 is lower than that of B2 is that the wavelength dependence of the reflectance is large. B3
Under the above conditions, the light use efficiency decreases as the twist angle increases. The light use efficiency is 95% when the twist angle is 80 °, and 86% when the twist angle is 90 °.

Based on the above calculation results, preferable conditions are selected. Transmissive type with chromaticity change of 0.08 or more for B1 condition
It is considered to be inappropriate because the driving voltage is higher than the TN mode and the driving voltage is as high as 6.5 Vrms or more at a contrast ratio of 300: 1 at 6.5 Vrms. It can be seen that the best balance of the characteristics is at B3 where the twist angle is greater than 73 °.

Looking at the condition B3 in detail, it can be seen that the larger the twist angle, the better the chromaticity change characteristics and drive voltage characteristics, but on the other hand, the light use efficiency is greatly reduced. If the twist angle exceeds 100 °, the light utilization efficiency will be less than 70%, which is almost the same as the aperture ratio of the transmission type liquid crystal display element, and the superiority of the reflection type will be lost. Therefore, the twist angle needs to be 100 ° or less.

The conditions for obtaining a chromaticity change and driving voltage comparable to those of the transmission type TN and obtaining a relatively high light use efficiency are as follows.
° to 90 °. The wavelength-normalized retardation at this time is 0.45 to 0.46. This is the wavelength 550
When converted to retardation at nm, 248 nm ~
253 nm.

In order to stabilize the orientation, the director, which is the direction of the molecular axis of the liquid crystal, is oriented at an angle of about 1 ° to 10 ° with respect to the substrate surface. The angle between the substrate surface and the director of the liquid crystal is called a tilt angle. Due to the tilt angle, the actual retardation is smaller than the product of the cell gap and the refractive index anisotropy of the liquid crystal material. Therefore, d △ n is designed to be slightly larger than 250 nm (250 n
It is necessary to set the wavelength-standardized retardation at m to 330 nm and wavelength 550 nm to 0.44 to 0.60).

The change in chromaticity and the drive voltage decrease as the twist angle increases, but the light use efficiency improves as the twist angle decreases. That is, the two have a trade-off relationship. A more desirable twist angle is a twist angle of 85 ° to 90 ° in which the three conditions of chromaticity change, drive voltage and light use efficiency are well balanced. In addition, the wavelength-normalized retardation at that time is 0.45 or more and 0.55 or less in consideration of the above pretilt angle.

It is to be noted that the liquid crystal orientation is set to 90 in any direction within the plane.
Even when it is rotated, its characteristics are basically the same as when it is not rotated.

(Embodiment 2) The drive voltage decreases as the twist angle increases, and the contrast ratio becomes higher when compared at the same drive voltage. Also,
The chromaticity change amount decreases as the twist angle increases. The condition of a twist angle of 90 ° is a condition where the contrast ratio is the highest and the amount of change in chromaticity is small even under the condition of the twist angle of 85 ° to 90 ° described in the first embodiment. Here, 90 °, which is a condition emphasizing a high contrast ratio and a low chromaticity change, is selected as the twist angle, and the most suitable condition in that case is proposed.

FIG. 7 shows the measurement results of the dependence of the reflectance on the liquid crystal alignment angle θ at each applied voltage. The cell gap of the liquid crystal cell used in the experiment is 2 μm, and the refractive index anisotropy Δn of the liquid crystal material is 0.149. Even if the same voltage is applied according to the liquid crystal alignment angle, the reflectance greatly varies.

At 0.0 Vrms, the range of the liquid crystal orientation angle having a high reflectivity is θ = 0 ° to 30 ° to 90 ° to 120 °. Above all, liquid crystal alignment angle θ = 10 ° to 20 ° to 100 °
It shows the highest reflectance at ~ 110 °. The liquid crystal alignment angle at which the maximum reflectance is obtained is θ = 15 ° to 105 °.

As the applied voltage increases, the reflectivity decreases. At around 3.9 Vrms, the dependence of the reflectance on the liquid crystal alignment angle becomes almost flat, but when the applied voltage is further increased, the liquid crystal alignment angle dependence appears again. The range of the liquid crystal alignment angle at which the reflectivity decreases is θ = −10 ° to 20 ° to 90 ° to 115 °.

Among them, the lowest reflectance is exhibited when the liquid crystal orientation angle θ = 0 ° to 10 ° to 95 ° to 110 °. The minimum reflectance is θ = 5 ° to 105 °.

FIG. 8 shows the dependence of the contrast ratio on the liquid crystal alignment angle. The contrast ratio is a ratio between 0.0 Vrms in FIG. 7 and another curve (3.1 Vrms to 7.0 Vrms). 3.1 Vr
In ms drive, the contrast ratio becomes maximum when the liquid crystal alignment angle is 30 ° to -60 °.

As the driving voltage is increased, the liquid crystal alignment angle at which the contrast ratio becomes maximum changes. When driving at 3.5 Vrms, the contrast ratio is maximized when the liquid crystal alignment angle is 20 ° to 110 °. In the case of 3.9 Vrms drive, the contrast ratio becomes maximum when the liquid crystal alignment angle is 15 ° to 105 °.
Also, the absolute value of the contrast ratio increases. When the driving voltage is further increased, the absolute value of the contrast ratio increases, and at the same time, the liquid crystal alignment angles that give the maximum contrast ratio are 10
° to 105 °.

As described above, when the drive voltages are determined, the liquid crystal alignment angle that maximizes the contrast ratio for each drive voltage may be selected within the range of 0 ° to 30 ° or 90 ° to 120 °.

(Embodiment of Liquid Crystal Display Element) An embodiment of a liquid crystal display element using the liquid crystal display mode of the present invention will be described with reference to FIG. FIG. 9 is a configuration sectional view of a liquid crystal display element according to the present embodiment. The polarization beam splitter shown in FIG. 1 is omitted in this figure.
In this embodiment, a single crystal silicon substrate is used as the active matrix substrate 122.

The active matrix substrate 122 is an n-type substrate
A p-type well 124 is formed on 123, and a MOS (Metal Oxid
e Semiconductor) forming a transistor 125 and a storage capacitor 126. Wiring between the transistors, an insulating film, and the like are further laminated, and a reflective electrode 127 and a protective film 130 are formed on the uppermost layer.

A liquid crystal layer 121 is sealed between a glass substrate 120 having a transparent electrode 128 and an active matrix substrate 122. A support 129 is provided to keep the thickness of the liquid crystal layer 121 constant. Since the liquid crystal display element for a projector is exposed to high-intensity light, a light-shielding layer 131 is provided so that light does not enter the region of the MOS transistor 125. 2μ thick liquid crystal layer
By setting m, a high-speed response of 12 ms or less including the rise time and fall time was realized.

FIG. 12 shows a range 401 in which the wavelength-normalized retardation at a wavelength of 550 nm is in the range of 0.44 to 0.60 in a coordinate plane of the layer thickness of the liquid crystal layer and the refractive anisotropy Δn of the liquid crystal material. FIG. 12 also shows the layer thickness dependence 402 of the liquid crystal response time of the liquid crystal.

It is known that the response time of the liquid crystal is proportional to the square of the thickness of the liquid crystal layer. This means, for example, E.Ja
keman and EPRaynes: Phys. Lett, 39A, p. 69 (1972). Therefore, based on the response time of 12 ms when the thickness of the liquid crystal layer is set to 2 μm as in the above results, the frame frequency that is generally used in personal computers is used.
It can be seen that the layer thickness required to realize a response of 16.7 ms or less, which is one frame period of 60 Hz, is 2.4 μm or less.
Here, a liquid crystal material having Δn of 0.149 was used. Also, at this time, in order to satisfy 0.44 to 0.60 as the wavelength-normalized retardation, it is understood that the refractive index anisotropy Δn of the liquid crystal material is 0.1 or more.

(Embodiment of Projection Type Liquid Crystal Display) An embodiment of a liquid crystal projector which is a projection type liquid crystal display using the liquid crystal display element of the present invention will be described with reference to FIG.

FIG. 10 shows the configuration of the liquid crystal projector of this embodiment. The LCD projector uses a white light source 301
, A polarizing beam splitter 302, dichroic mirrors 303 and 304, and liquid crystal light valves 305R and 305G of the present invention.
305B, a projection lens 306 and the like.

The light emitted from the white light source 301 is reflected by the polarizing beam splitter 302 only on the polarized light component perpendicular to the plane of the drawing, and the dichroic mirrors 303 and 304 emit red, blue and blue light.
The liquid crystal display element 305
R, 305G, and 305B are incident. The incident light undergoes phase modulation in the liquid crystal layer in each of the liquid crystal display elements 305R, 305G, 305B,
Dichroic mirror 303 reflected by the pixel electrode again,
Only the polarized light component parallel to the plane of the paper is transmitted by the polarizing beam splitter 302 and is projected through the projection lens 306 onto a screen (not shown in FIG. 7). Since the liquid crystal display element of the present invention is used for the liquid crystal display elements 305R, 305G, and 305B, the response time of the liquid crystal is fast, and a moving image can be displayed very smoothly.

[0085]

According to the present invention, since the voltage dependence of chromaticity is small, relatively low voltage driving is possible, and the high-speed response is excellent, the use of the liquid crystal display element of the present invention makes it possible to A moving image can be smoothly displayed on the projection type liquid crystal display device.

The liquid crystal display device of the present invention can be produced at a low cost because it can be produced using a stable liquid crystal alignment process.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a relative relationship between optical axes of respective optical elements in a liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a twist angle and a wavelength-normalized retardation.

FIG. 3 is a diagram showing a relationship between a twist angle and a liquid crystal alignment angle.

FIG. 4 is a diagram showing a twist angle dependency of a chromaticity change amount.

FIG. 5 is a diagram illustrating a twist angle dependency of a driving voltage.

FIG. 6 is a diagram showing a twist angle dependency of light use efficiency.

FIG. 7 is a diagram showing the dependence of the reflectance on the liquid crystal alignment angle at each applied voltage.

FIG. 8 is a diagram showing the dependence of the contrast ratio on the liquid crystal alignment angle at each drive voltage.

FIG. 9 is a configuration sectional view of a liquid crystal display element according to the present embodiment.

FIG. 10 is a schematic diagram of a liquid crystal projector which is a projection type liquid crystal display device using the liquid crystal display element of the present invention.

FIG. 11 is an explanatory diagram of a definition of a chromaticity change amount.

FIG. 12 is a diagram illustrating the range of the wavelength-normalized retardation and the dependence of the response time of the liquid crystal on the thickness of the liquid crystal layer.

[Explanation of symbols]

101: reflective electrode, 102: liquid crystal layer, 103: polarized beam splitter, 104: incident light, 105: return light to the lamp, 106: light emitted to the screen, 107: horizontal polarization component, 108: upper liquid crystal alignment, 109: lower liquid crystal alignment, 110: twist angle, 11
1: liquid crystal alignment angle, 120: glass substrate, 121: liquid crystal layer, 122
... active matrix substrate, 123 ... n-type substrate, 124 ... p-
well, 125 MOS transistor, 126 storage capacitor, 127 reflective electrode, 128 transparent electrode, 129 support, 130 protective film, 131
... light-shielding electrode layer, 201,204,207,210,213 ... branch 1 (B
1), 202,205,208,211,214 ... branch 2 (B2), 203,20
6,209,212,215… Branch 3 (B3)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuya Takemoto 3300 Hayano Mobara-shi, Chiba F-term in the Electronic Devices Division, Hitachi, Ltd. (Reference) 2H090 KA05 LA04 LA09 LA20 MA06 MA10 2H091 FA05Z FA10Z FA14Z GA06 GA11 GA13 HA07 KA02 KA10 LA15 MA07 2H092 JA25 NA05 PA02 PA06 PA12 QA07 RA05

Claims (5)

[Claims] 1. A liquid crystal display device comprising: a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode; a plurality of pixel circuits for driving the liquid crystal layer; and a peripheral circuit for driving each of the pixel circuits. A liquid crystal display device characterized in that the twist angle of the layer is 90 ° and the liquid crystal alignment angle is in the range of 0 ° to 30 ° or 90 ° to 120 °. 2. The liquid crystal display according to claim 1, wherein the liquid crystal orientation angle is 10
A liquid crystal display device characterized by being in the range of from 20 ° to 100 ° to 110 °. 3. A liquid crystal display device comprising: a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode; a plurality of pixel circuits for driving the liquid crystal layer; and a peripheral circuit for driving each of the pixel circuits. The twist angle of the layer is 90 °, and the liquid crystal alignment angle is in the range of 10 ° to 20 ° to 100 ° to 110 °, and the wavelength-normalized retardation of the liquid crystal layer is further reduced.
A liquid crystal display element having a size of 0.45 or more and 0.55 or less. 4. A liquid crystal display device having a liquid crystal display element that phase-modulates incident light and reflects the reflected light to output an image, the liquid crystal display element comprising: a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode; A plurality of pixel circuits for driving the layers, and a peripheral circuit for driving each of the pixel circuits, wherein the twist angle of the liquid crystal layer is 73 ° or more and 100 ° or less, and the wavelength-standardized retardation of the liquid crystal layer is reduced. The response time of the liquid crystal is set to 16.7 ms or less by setting the thickness of the liquid crystal layer to 0.4 μm or less and the refractive index anisotropy of the liquid crystal material to 0.1 or more. Characteristic liquid crystal display device. 5. An image display method using a liquid crystal display element having a liquid crystal layer sandwiched between a transparent electrode and a reflective electrode, a plurality of pixel circuits for driving the liquid crystal layer, and a peripheral circuit for driving each of the pixel circuits. 5. The image display method according to claim 1, wherein a twist angle of the liquid crystal layer is set to 73 ° or more and 100 ° or less, and an image is displayed at a drive voltage of 3 to 6 Vrms.