JPH0815691A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a bright color display without using color filters, to widen visual field angles and to lessen color changes of display colors by temp. CONSTITUTION:Polarizing plates 21, 22 are arranged across a liquid crystal cell 10 where liquid crystal molecules are twist oriented. A biaxial phase difference plate 23 having a refractive index nx in an x-axis direction which is a delay axis phase, a refractive index ny in a y-axis direction and a refractive index nz in a z-axis direction in a relation nx>nz>ny is arranged between the front side polarizing plate 21 and the liquid crystal cell 10. The directions of the transmission axes of the polarizing plates 21, 22 and the delay axis of the phase difference plate 23 and the orienting direction of liquid crystal moleculates near the substrate of the liquid crystal cell 10 are so set that the respective wavelength light rays of the incident light after transmitting the front side polarizing plate 21 are made into elliptically polarized light rays of the respectively different polarization states by the double refractive effect of the phase difference plate 23 and the double refractive effect of the liquid crystal layer 18 of the liquid crystal cell 10 and that the light quantity ratios of the respective wavelength light rays of the light transmitted through the rear side polarizing plate 22 among these light rays attains the ratios corresponding to the desired colored light rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal display device for obtaining bright color display without using a color filter.

[0002]

2. Description of the Related Art As a color liquid crystal display device capable of providing a colored display, one that colors light using a color filter is generally used.

However, this color liquid crystal display device has a problem that the light transmittance is low and therefore the display is dark because it uses a color filter to color light.

This is due to the absorption of light by the color filter, and the color filter absorbs not only the wavelength light outside the wavelength band corresponding to the color but also the light in the wavelength band with a considerably high absorption rate. Therefore, the colored light that has passed through the color filter has a significantly reduced amount of light as compared with the light in the wavelength band before entering the color filter, and the display becomes dark.

There are two types of liquid crystal display devices, a transmissive type that uses light from a backlight arranged on the back surface side of the liquid crystal display device, and a light that passes through the liquid crystal display device using external light on the back surface side. There is a reflective type that reflects and displays with a reflective plate disposed in, but when the color liquid crystal display device is a reflective type, light that enters from the front surface side and is reflected by the reflective plate and emitted to the front surface side is displayed. Since the light amount is doubled by passing through the color filter twice, the display becomes extremely dark, and it becomes almost unusable as a display device.

Moreover, in the above-mentioned color liquid crystal display device, the display color at each location where the electrodes of both substrates of the liquid crystal cell face each other is determined by the color of the color filter provided at this location, so that 1 is provided at the same location. I could only display colors.

There are two types of liquid crystal display devices, a segment display type and a dot matrix display type. In a conventional color liquid crystal display device of the segment display type, the display color of each display pattern is the same. In the conventional color liquid crystal display device using the dot display type liquid crystal cell, which is determined by the color of the color filter corresponding to the segment electrode for displaying the pattern, the color of each pixel is the color of the color filter corresponding to that pixel. Depends on

On the other hand, an EC that does not require a color filter
A B (birefringence effect) type color liquid crystal display device is conventionally known.

In this ECB type liquid crystal display device, a pair of polarizing plates are sandwiched by a liquid crystal cell having a liquid crystal layer provided between a pair of transparent substrates having a transparent electrode formed on the inner surface (a surface facing the liquid crystal layer). As the liquid crystal cells, those in which liquid crystal molecules are aligned in any one of twist alignment, homogeneous alignment, homeotropic alignment, and hybrid alignment are generally used as the liquid crystal cells.

In this ECB type liquid crystal display device, the linearly polarized light that has entered through one of the polarizing plates and is incident on the liquid crystal cell is an ellipse having different polarization states due to the birefringence effect of the liquid crystal layer. The light becomes polarized light, the light enters the other polarizing plate, and the light transmitted through the other polarizing plate becomes colored light having a color corresponding to the light amount ratio of each wavelength light forming the light.

That is, the ECB type liquid crystal display device is
Light is colored by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell and the polarization effect of the pair of polarizing plates without using a color filter, and therefore, there is no absorption of light by the color filter. It is possible to obtain a bright color display by increasing the transmittance.

In addition, in the ECB type liquid crystal display device, the birefringence of the liquid crystal layer changes depending on the alignment state of the liquid crystal molecules due to the voltage applied between the electrodes of both substrates of the liquid crystal cell, and the other polarizing plate is correspondingly changed. Since the polarization state of each wavelength light incident on is changed, it is possible to change the color of the colored light by controlling the voltage applied to the liquid crystal cell, and thus it is possible to display a plurality of colors at the same location. it can.

[0013]

However, in the above-mentioned ECB type liquid crystal display device, the birefringence of the liquid crystal layer of the liquid crystal cell largely changes depending on the incident angle of light, so that the display color changes depending on the viewing angle (observation angle of display). There is also a problem that the viewing angle is narrow because of a large change.

Moreover, the ECB type liquid crystal display device has a problem that the color change of the display color is large depending on the temperature. This is because the birefringence of the liquid crystal layer of the liquid crystal cell has temperature dependence, and the birefringence of the liquid crystal layer of the liquid crystal cell is Δn · d (refractive index anisotropy Δn of liquid crystal and liquid crystal Although it depends on the value of (the product of the layer thickness d), the refractive index anisotropy Δn of the liquid crystal largely changes with temperature, so that the birefringence of the liquid crystal layer greatly changes with temperature and the display color changes.

According to the present invention, a bright color display can be obtained without using a color filter, a plurality of colors can be displayed at the same location, and the viewing angle is wide, and the color change of the display color due to temperature is small. An object of the present invention is to provide a color liquid crystal display device.

[0016]

A color liquid crystal display device of the present invention is a liquid crystal cell comprising a nematic liquid crystal layer in which liquid crystal molecules are twist-aligned between a pair of substrates having electrodes formed on the inner surfaces thereof, and the liquid crystal cell. A pair of polarizing plates arranged on the front surface side and the back surface side of the polarizing plate, and a retardation plate disposed between the pair of polarizing plates, and the retardation plate has a slow axis the refractive indices n _x a certain x-axis direction, a refractive index n _z in the refractive index n _y and z-axis direction of the y-axis direction, n _x
A biaxial retardation plate having a relation of> n _z > n _y , wherein the transmission axes of the pair of polarizing plates and the directions of the slow axes of the retardation plates and the liquid crystal molecules in the vicinity of the substrate of the liquid crystal cell Alignment direction, the light incident through the one polarizing plate is elliptically polarized light having different polarization states due to the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer of the liquid crystal cell. The light quantity ratio of each wavelength light of the light transmitted through the other polarizing plate of the light is set to be a ratio corresponding to a desired colored light.

The present invention can be applied to both a transmissive liquid crystal display device and a reflective liquid crystal display device in which a reflecting plate is arranged behind a back side polarizing plate arranged on the back side of a liquid crystal cell. The number of the biaxial retardation plate may be one or two, and the twist angle of the liquid crystal molecules of the liquid crystal cell is 8
0 ° -110 °, 110 ° -130 °, 180 ° -27
It may be 0 °.

Further, in the case of using one biaxial retardation plate in the reflection type liquid crystal display device, the retardation plate is composed of the front side polarizing plate arranged on the surface side of the liquid crystal cell and the liquid crystal cell. It is desirable to dispose them between them. In that case, at least the transmission axis of the front-side polarizing plate and the slow axis of the retardation plate may be slanted by a predetermined angle.

Further, in the reflection type liquid crystal display device, 2
When using a sheet of biaxial retardation plate, between the front side polarizing plate and the liquid crystal cell, and between the back side polarizing plate and the liquid crystal cell,
One retardation plate may be provided, and in that case, at least the transmission axis of the front-side polarizing plate and the slow axis of the retardation plate adjacent to this polarizing plate are slanted by a predetermined angle. Good.

Furthermore, in the case of using two biaxial retardation plates in the reflection type liquid crystal display device, two retardation plates are placed to overlap each other between the front side polarizing plate and the liquid crystal cell. In that case, at least the transmission axis of the front-side polarizing plate and the slow axis of the retardation plate adjacent to the front-side polarizing plate of the two retardation plates are offset by a predetermined angle. Good.

As an example of applying the present invention to a reflection type liquid crystal display device in which one biaxial retardation plate is arranged between a front side polarizing plate and a liquid crystal cell, a twist of liquid crystal molecules of a liquid crystal cell is given as an example. Angle of 80 ° to 110 °, Δn · d of the liquid crystal cell
The value of (product of refractive index anisotropy Δn of liquid crystal and liquid crystal layer thickness d) is 520 nm to 580 nm, retardation of retardation plate (refractive index anisotropy Δn of retardation plate and thickness d of retardation plate) Value) of 400 nm to 460 nm.

The twist angle of the liquid crystal molecules of the liquid crystal cell is set to 110.
° ~ 130 °, the liquid crystal value of the liquid crystal cell is 880 nm ~
970 nm, the retardation value of the retardation plate is 1270
nm to 1530 nm.

The twist angle of the liquid crystal molecules of the liquid crystal cell is set to 180.
° to 270 °, the value of Δn · d of the liquid crystal cell is set to 850n
m to 910 nm, retardation value of retardation plate is 40
It is set to 0 nm to 460 nm.

There are examples such as

Further, according to the present invention, 1 is provided between the front side polarizing plate and the liquid crystal cell and between the back side polarizing plate and the liquid crystal cell.
As an example of application to a reflective liquid crystal display device in which biaxial retardation plates are arranged one by one, the twist angle of liquid crystal molecules of the liquid crystal cell is 180 ° to 270 °, and the value of Δn · d of the liquid crystal cell is 1250 nm to 1450 nm, the retardation value of the retardation plate adjacent to the front polarizing plate is set to 1570 nm to 1630.
nm, there is an example in which the retardation value of the retardation plate adjacent to the back side polarizing plate is set to 1570 nm to 1630 nm.

Further, as an example in which the present invention is applied to a reflection type liquid crystal display device in which two biaxial retardation plates are arranged to overlap each other between a front side polarizing plate and a liquid crystal cell, The twist angle of the liquid crystal molecule is 180 ° to 270 °, the value of Δn · d of the liquid crystal cell is 1250 nm to 1450 nm, and the retardation value of the retardation plate adjacent to the front polarizing plate is 1.
570 nm to 1630 nm, the retardation value of the retardation plate adjacent to the liquid crystal cell is 1520 nm to 1580 nm
There is an example.

Further, 2 is provided between the front side polarizing plate and the liquid crystal cell.
In a reflection type liquid crystal display device in which two biaxial retardation plates are arranged to overlap each other, when the twist angle of liquid crystal molecules of the liquid crystal cell is 180 ° to 270 °, the value of Δn · d of the liquid crystal cell May be as large as 1490 nm or more.

As an example, the value of Δn · d of the liquid crystal cell is 1490 nm to 1590 nm, and the value of retardation of the retardation plate adjacent to the front polarizing plate is 1570 nm to 163.
The retardation value of the retardation film adjacent to the liquid crystal cell is set to 0 nm and 1420 nm to 1480 nm.

The value of Δn · d of the liquid crystal cell is from 1530 nm to
1730 nm, the retardation value of the retardation plate adjacent to the front-side polarizing plate is 1570 nm to 1630 nm, and the retardation value of the retardation plate adjacent to the liquid crystal cell is 1520 n.
m to 1580 nm.

There are examples such as

Further, another color liquid crystal display device of the present invention is used as a reflection type display device and has a nematic liquid crystal layer in which liquid crystal molecules are twist-aligned between a pair of substrates having electrodes formed on the inner surfaces thereof. A liquid crystal cell provided,
A single polarizing plate arranged only on the front surface side of the liquid crystal cell, a reflecting plate arranged on the rear surface side of the liquid crystal cell, and a retardation plate arranged between the polarizing plate and the reflecting plate. Prepare,
Further, in the retardation plate, the refractive index n _x in the x-axis direction, which is the slow axis, and the refractive index n _{y in the y-} axis direction and the refractive index n _{z in the} z-axis direction are n _x > n _z >. In the biaxial retardation plate having a relationship of n _y, the directions of the transmission axis of the polarizing plate and the slow axis of the retardation plate and the alignment direction of liquid crystal molecules near the substrate of the liquid crystal cell are The light that passes through the polarizing plate and is reflected by the reflecting plate and then enters the polarizing plate is polarized by the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer of the liquid crystal cell. It is characterized in that elliptically polarized light in different states is obtained, and the light amount ratio of each wavelength light of the light transmitted through the polarizing plate of the light is set to a ratio corresponding to a desired colored light. It is a thing.

[0032]

In the color liquid crystal display device of the present invention, while the linearly polarized light that has been transmitted through one of the polarizing plates and is incident thereon is transmitted through the retardation plate and the liquid crystal cell, the birefringence effect of the retardation plate and the liquid crystal Due to the birefringence effect of the liquid crystal layer of the cell, each wavelength light becomes elliptically polarized light having a different polarization state, the light enters the other polarizing plate, and the light transmitted through the other polarizing plate constitutes the light. The colored light has a color corresponding to the light amount ratio of each wavelength light.

In a reflection type liquid crystal display device in which a reflection plate is arranged behind a back side polarizing plate arranged on the back side of the liquid crystal cell, incident light from the front side is the front side polarizing plate, the retardation plate and the liquid crystal. The light that has passed through the cell and is incident on the back-side polarizing plate, and the light that has passed through the back-side polarizing plate and has become colored light is reflected by the reflection plate, and the back-side polarizing plate and the liquid crystal cell, and the retardation plate and the front-side polarizing plate. The light is transmitted and emitted to the surface side.

The color of this colored light is the direction of the transmission axis of the pair of polarizing plates, the direction of the slow axis of the retardation plate, and the alignment direction of the liquid crystal molecules in the vicinity of both substrates of the liquid crystal cell. It can be arbitrarily selected by setting the light amount ratio of each wavelength light of the light transmitted through the plate to be a ratio corresponding to a desired colored light.

That is, this color liquid crystal display device utilizes the birefringence effect of the retardation film, the birefringence effect of the liquid crystal layer of the liquid crystal cell, and the polarization effect of the pair of polarizing plates without using a color filter. Since it does not absorb light by the color filter, it is possible to obtain a bright color display by increasing the light transmittance regardless of whether it is a transmission type or a reflection type.

Further, in this color liquid crystal display device, the birefringence of the retardation plate is determined by the retardation value of the retardation plate, but the birefringence of the liquid crystal layer of the liquid crystal cell is determined by the difference between the electrodes of both substrates. The voltage applied to the liquid crystal molecules changes depending on the alignment state of the liquid crystal molecules, and the polarization state of each wavelength light incident on the other polarizing plate changes accordingly. It is possible to change the color of the colored light, and thus it is possible to display a plurality of colors at the same place.

Moreover, in this color liquid crystal display device, the birefringence of the liquid crystal layer of the liquid crystal cell changes depending on the incident angle of light, but the birefringence of the retardation plate hardly changes even when the incident angle of light changes. In the retardation plate, the refractive index n _x in the x-axis direction, which is the slow axis, and the refractive index n _{y in the y-} axis direction and the refractive index n _{z in the} z-axis direction are n _x > n. _z > n
_Since it is a biaxial retardation plate having a relation of _y, the biaxial retardation plate compensates for the phase difference between when the light is transmitted vertically through the liquid crystal layer of the liquid crystal cell and when it is transmitted obliquely. Therefore, the viewing angle becomes wider.

Further, in this color liquid crystal display device, the birefringence of the liquid crystal layer of the liquid crystal cell changes depending on the temperature, but the birefringence change of the retardation plate due to the temperature is very small, so that the liquid crystal of the liquid crystal cell is changed. The birefringence of the entire layer and the retardation film has a characteristic that the temperature dependence is small, and therefore the color change of the display color due to the temperature is also small.

Further, in the case of using one biaxial retardation plate in the reflection type liquid crystal display device, this retardation plate is arranged between the front side polarizing plate and the liquid crystal cell, and at least the front side polarizing plate is used. If the transmission axis of and the slow axis of the retardation plate are slanted by a predetermined angle, linearly polarized light that has passed through the front side polarizing plate and enters will be polarized by the birefringence effect in the process of passing through the retardation plate. Since the light is changed in state and the light is further changed in polarization state by the birefringence effect of the liquid crystal layer in the process of passing through the liquid crystal cell and is incident on the back side polarizing plate, the above-mentioned colored light can be obtained.

When two biaxial retardation plates are used in the reflection type liquid crystal display device, 1 is provided between the front side polarizing plate and the liquid crystal cell and between the back side polarizing plate and the liquid crystal cell. By arranging retardation plates one by one, and at least shifting the transmission axis of the front side polarizing plate and the slow axis of the retardation plate adjacent to this polarizing plate by a predetermined angle, the light is transmitted through the front side polarizing plate and incident. The linearly polarized light is changed in polarization state by the birefringence effect in the process of passing through the retardation plate adjacent to the front side polarizing plate, and further polarized by the birefringence effect in the liquid crystal layer in the process in which the light passes through the liquid crystal cell. It is possible to obtain the above-mentioned colored light because the polarization state is changed by the birefringence effect and is incident on the back side polarizing plate in the process of changing the state and further transmitting the light through the retardation plate adjacent to the back side polarizing plate. it can.

When two biaxial retardation plates are used in the reflection type liquid crystal display device, the two biaxial retardation plates are arranged to overlap each other between the front side polarizing plate and the liquid crystal cell. ,
If at least the transmission axis of the front-side polarizing plate and the slow axis of the retardation plate of the two retardation plates adjacent to the front-side polarizing plate are offset by a predetermined angle, the front-side polarizing plate is transmitted. The incident linearly polarized light is changed in polarization state by the birefringence effect in the process of passing through the retardation plate adjacent to the front side polarizing plate, and the polarized light is changed in the process of passing through the retardation plate adjacent to the liquid crystal cell. The polarization state can be further changed by the refraction effect, and the polarization state can be changed by the birefringence effect of the liquid crystal layer in the process of transmitting the light through the liquid crystal cell to be incident on the back side polarizing plate. it can.

In the liquid crystal display device using the above-mentioned two biaxial retardation plates, the phase difference between when light vertically passes through the liquid crystal layer of the liquid crystal cell and when it obliquely passes is two biaxial. Since it is more effectively compensated by the retardation film, the viewing angle is further widened, and the birefringence of the liquid crystal layer of the liquid crystal cell and the two retardation plates is further dependent on the temperature. Since the characteristic becomes small, the color change of the display color due to the temperature becomes smaller.

Further, 2 is provided between the front side polarizing plate and the liquid crystal cell.
In a reflection-type liquid crystal display device in which two biaxial retardation plates are arranged on top of each other, when the twist angle of the liquid crystal molecules of the liquid crystal cell is 180 ° to 270 °, Δn.
If the value of d is increased to 1490 nm or more, the change in birefringence with respect to the applied voltage of the liquid crystal layer becomes large.
The number of display colors can be increased.

Further, another color liquid crystal display device of the present invention is used as a reflection type display device, and in this color liquid crystal display device, the light is transmitted through a polarizing plate arranged on the surface side of the liquid crystal cell. The linearly polarized light that has been incident as an incident light passes through the retardation plate and the liquid crystal cell, and is further reflected by the reflection plate,
While passing through the liquid crystal cell and the retardation plate again, each wavelength light becomes elliptically polarized light having different polarization states due to the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer of the liquid crystal cell, and the light The light incident on the polarizing plate and transmitted through the polarizing plate becomes colored light of a color corresponding to the light quantity ratio of the wavelength lights constituting the light.

The color of the colored light is transmitted through the polarizing plate in the directions of the transmission axis of the polarizing plate, the slow axis of the retardation plate, and the alignment direction of liquid crystal molecules in the vicinity of both substrates of the liquid crystal cell. It can be arbitrarily selected by setting the light quantity ratio of each wavelength light of the above-mentioned light to be a ratio corresponding to a desired colored light.

That is, this color liquid crystal display device utilizes the birefringence effect of the retardation plate, the birefringence effect of the liquid crystal layer of the liquid crystal cell, and the polarization effect of the polarizing plate without using a color filter. Therefore, since the color filter does not absorb light, it is possible to obtain a bright color display by increasing the light transmittance even in the reflective type.

Also in this color liquid crystal display device, the birefringence of the liquid crystal layer of the liquid crystal cell is changed by the change of the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes of the both substrates. The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell, and therefore, a plurality of colors can be displayed at the same place.

Also in this color liquid crystal display device, the birefringence of the liquid crystal layer of the liquid crystal cell changes depending on the incident angle of light, but the birefringence of the retardation plate hardly changes even when the incident angle of light changes. In the retardation plate, the refractive index n _x in the x-axis direction, which is the slow axis, and the refractive index n _{y in the y-} axis direction and the refractive index n _{z in the} z-axis direction are n _x > n. _z > n
_Since it is a biaxial retardation plate having a relation of _y, the biaxial retardation plate compensates for the phase difference between when the light is transmitted vertically through the liquid crystal layer of the liquid crystal cell and when it is transmitted obliquely. Therefore, the viewing angle becomes wider.

Further, also in this color liquid crystal display device, the birefringence of the liquid crystal layer of the liquid crystal cell changes depending on the temperature, but the birefringence change of the retardation plate due to the temperature is extremely small, and therefore the liquid crystal of the liquid crystal cell is The birefringence of the entire layer and the retardation film has a characteristic that the temperature dependence is small, and therefore the color change of the display color due to the temperature is also small.

[0050]

【Example】

[First Embodiment] Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. The color liquid crystal display device of this embodiment uses a liquid crystal cell in which the twist angle of liquid crystal molecules is 80 ° to 110 ° and one biaxial retardation plate.

FIG. 1 is a cross-sectional view of a color liquid crystal display device. This liquid crystal display device includes a liquid crystal cell 10 and a front surface side (upper surface side in the drawing) and a back surface side (in the drawing) of the liquid crystal cell 10. A pair of polarizing plates 2 arranged on the lower surface side)
1, 22 and one front side polarizing plate 21 arranged on the front surface side of the liquid crystal cell 10 and one retardation plate 23 arranged between the liquid crystal cell 10 and the rear surface side of the liquid crystal cell 10. It is composed of a reflecting plate 25 arranged behind the back side polarizing plate 22.

The liquid crystal cell 10 has a transparent electrode 1 on its inner surface.
3, a pair of transparent substrates 11 and 12 on which alignment films 15 and 16 are formed are bonded via a frame-shaped sealing material 17, and the sealing material 17 between the substrates 11 and 12 is joined. A nematic liquid crystal layer 18 in which liquid crystal molecules are twist-aligned is provided in a region surrounded by.

The liquid crystal cell 10 is of a simple matrix type and has electrodes 1 formed on the inner surface of the front substrate 11.
Reference numeral 3 denotes a scanning electrode, and an electrode 1 formed on the inner surface of the back substrate 12
4 is a signal electrode.

The alignment films 15 and 16 provided on the inner surfaces of both substrates 11 and 12 are horizontal alignment films made of, for example, polyimide, and these alignment films 15 and 16 are
Alignment treatment is performed by rubbing the film surface in a predetermined direction.

The molecules of the liquid crystal of the liquid crystal layer 18 are
The orientation directions on the substrates 11 and 12 side are regulated by the orientation films 15 and 16, and the substrates 11 and 12 are twist-oriented at a twist angle of 80 ° to 110 ° (approximately 90 ° in this embodiment). There is. The liquid crystal layer 1
In 8, a chiral liquid crystal that imparts twist alignment to liquid crystal molecules is added.

Of the pair of polarizing plates 21 and 22, the front polarizing plate 21 has its transmission axis set to the liquid crystal cell 1 described above.
0 is disposed substantially parallel to or substantially orthogonal to the alignment direction of liquid crystal molecules in the vicinity of one substrate, and the rear side polarizing plate 22 has its transmission axis substantially parallel to the transmission axis of the front side polarizing plate 21. The retardation plate 23 is provided so as to be inclined or substantially orthogonal to each other, and the slow axis thereof is slanted by a predetermined angle with respect to the transmission axis of the front side polarizing plate 21.

FIG. 2 shows the alignment directions of liquid crystal molecules of the liquid crystal cell 10, the transmission axes of the polarizing plates 21 and 22, and the retardation plate 23.
FIG. 11 is a view showing the direction of the slow axis of the liquid crystal cell when viewed from the front side, in which 11a is the alignment direction of liquid crystal molecules in the vicinity of the front substrate 11 of the liquid crystal cell 10, and 12a is the vicinity of the back substrate 12 of the liquid crystal cell 10. 3 shows the orientation direction of liquid crystal molecules.

As shown in FIG. 2, the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is about 45 ° clockwise with respect to the horizontal axis S of the liquid crystal cell 10 when viewed from the front side. Direction, the alignment direction 11a of the liquid crystal molecules near the front substrate 11 is approximately 90 ° counterclockwise when viewed from the front side with respect to the alignment direction 12a of the liquid crystal molecules near the back substrate 12. Is the backside substrate 1
From the 2nd side to the front side substrate 11 side, as viewed from the front side, the twist orientation is clockwise with a twist angle of about 90 °.

Further, in FIG. 2, 21a indicates a transmission axis of the front side polarizing plate 21, and 22a indicates a transmission axis of the back side polarizing plate 22. In this embodiment, the transmission axis 21 of the front side polarizing plate 21 is shown.
a is substantially orthogonal to the alignment direction 11a of the liquid crystal molecules near the front substrate 11 of the liquid crystal cell 10, and the transmission axis 22a of the back polarizing plate 22 is the transmission axis 21a of the front polarizing plate 21.
It is almost parallel to.

Further, in FIG. 2, reference numeral 23a denotes a slow axis of the retardation plate 23, and the slow axis 23a of the retardation plate 23 is at a predetermined angle with respect to the transmission axis 21a of the front side polarizing plate 21. It is slanted. In this embodiment,
The slow axis 23a of the retardation plate 23 is shifted from the transmission axis 21a of the front-side polarizing plate 21 by approximately 45 ° in the opposite direction (counterclockwise) to the liquid crystal molecule twist direction of the liquid crystal cell 10 when viewed from the surface side. .

FIG. 3 is a perspective view of the retardation plate 23.
The retardation plate 23 has a refractive index n _x in the x-axis direction, which is the slow axis (stretching axis) 23 a, a refractive index n _{y in the y-} axis direction, and a refractive index n _{z in the} z-axis direction, n _x >. It is a biaxial phase plate having a relationship of n _z > n _y .

Further, in this embodiment, the liquid crystal cell 10 described above is used.
Is the product Δ of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d.
The value of n · d is 552 nm. The birefringence Δn of the liquid crystal of the liquid crystal cell 10 and the liquid crystal layer thickness d
Is Δn = 0.092 d = 6 μm.

Further, in this embodiment, as the biaxial retardation plate 23, the refractive index n _x in the x-, y-, and z-axis directions,
n _y and n _z and their plate thicknesses (thicknesses of the portion having the refractive index anisotropy) are n _x = 1.4 n _y = 1.2 n _z = 1.3 d = 2.15 μm I am using.

The biaxial retardation plate 23 has a refractive index anisotropy Δn (Δn = n _x −n _y) corresponding to the difference between the refractive index n _{x in the x-} axis direction and the refractive index n _{y in the} y-axis direction. ), And the value of its retardation (the product of the refractive index anisotropy Δn of the retardation plate and the plate thickness d of the retardation plate) is 430 nm.

The above-mentioned color liquid crystal display device displays external light (natural light, indoor illumination light, etc.) incident from the front surface side by reflecting it on the rear surface side reflection plate 25, and displays it on both substrates 11 of the liquid crystal cell 10. , 12 are applied to drive a display by applying a voltage between the electrodes 13 and 14.

In this color liquid crystal display device, while the linearly polarized light which has passed through the front-side polarizing plate 21 and is incident from the surface side thereof sequentially passes through the retardation plate 23 and the liquid crystal cell 10, the retardation plate is formed. The polarization state is changed by the birefringence effect of 23 and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, and enters the back-side polarizing plate 22.
The light transmitted through becomes the colored light.

Explaining the coloring of this light, external light entering the liquid crystal display device first enters the retardation film 23 after passing through the front side polarizing plate 21 to become linearly polarized light.
The retardation plate 23 has a slow axis 23a at a predetermined angle with respect to the transmission axis 21a of the front-side polarizing plate 21 (in this embodiment, approximately 4 degrees).
5 °) Since it is deviated obliquely, the linearly polarized light that has passed through the front-side polarizing plate 21 undergoes a birefringence action according to the value of its retardation while passing through the retardation plate 23, and each wavelength light has its respective polarization state. Different elliptically polarized light.

The light transmitted through the phase difference plate 23 is
While entering the liquid crystal cell 10 and passing through the liquid crystal layer 18, the liquid crystal cell 10 is subjected to a birefringence action according to the value of Δn · d of the liquid crystal cell 10 and the alignment state of the liquid crystal molecules, and the elliptically polarized light of each wavelength light The light becomes a state that has changed further.

Thus, the elliptically polarized light of which the respective wavelengths have different polarization states due to the birefringence effect of the retardation film 23 and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 is backside polarized light. Of the light that has entered the plate 22, only the component light along the transmission axis 22a of the back-side polarizing plate 22 passes through this back-side polarizing plate 22, and this transmitted light (linearly polarized light)
However, the colored light becomes a colored light having a color corresponding to the light amount ratio of each wavelength light that constitutes the transmitted light.

The color of this colored light depends on the pair of polarizing plates 21 and 2.
2, the transmission axes 21a and 22a and the slow axis 23a of the retardation plate 23, the orientation directions 11a and 12a of liquid crystal molecules near the substrates 11 and 12 of the liquid crystal cell 10, and Δn · d of the liquid crystal cell 10. And the retardation value of the retardation film 23 are set so that the light quantity ratio of each wavelength light constituting the light transmitted through the back side polarizing plate 22 becomes a ratio corresponding to a desired colored light. You can choose.

Further, the colored light transmitted through the back side polarizing plate 22 is reflected by the reflection plate 25 and is emitted to the upper surface side of the liquid crystal display device through a route opposite to the above-mentioned optical route, and the colored light displays a color image. To be done.

In this case, the colored light reflected by the reflection plate 25 is the phase difference plate 23 and the liquid crystal layer 1 of the liquid crystal cell 10.
Of the light that has become elliptically polarized light having different polarization states due to the birefringence effect of 8, the light is only the component of the component along the transmission axis 22a of the back-side polarizing plate 22, Light of a very small wavelength component is birefringent in the process of passing through the liquid crystal cell 10 and the retardation film 23 again and is absorbed by the front side polarizing plate 21, so that the colored light that passes through the front side polarizing plate 21 and is emitted. Is light whose color purity is better than that of the colored light reflected by the reflector 25.

That is, in the color liquid crystal display device, the birefringence effect of the retardation plate 23, the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, and the pair of polarizing plates 21 and 22 are used without using the color filter. Since the light is colored by utilizing the polarization effect, and the light is not absorbed by the color filter, the light transmittance can be increased. Therefore, even if the color liquid crystal display device is of a reflective type, a very bright color display can be obtained.

Further, in this color liquid crystal display device, the birefringence of the retardation plate 23 is determined by the retardation value of the retardation plate 23, but the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 is It changes depending on the change of the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes 13 and 14 of both substrates 11 and 12, and the polarization state of each wavelength light incident on the back side polarizing plate 22 changes accordingly. For,
The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell 10, and therefore, a plurality of colors can be displayed at the same location, that is, the same pixel.

That is, the liquid crystal molecules of the liquid crystal cell 10 are in the initial twist alignment state in which they are most collapsed with respect to the surfaces of the substrates 11 and 12 when no voltage is applied between the electrodes 13 and 14. When a voltage is applied between 14, as the applied voltage is increased, the rise alignment is performed while maintaining the twist alignment state, and finally, the substrate 11,
It will be in a state of rising almost vertically to the 12th surface.

The value of the refractive index anisotropy Δn of the liquid crystal is
Apparently, the liquid crystal molecules become smaller as they rise and align, and become “0” when the liquid crystal molecules vertically rise and align. Therefore, the apparent value of Δn · d of the liquid crystal cell 10 is The maximum value is obtained when the liquid crystal molecules are in the initial twist alignment state, and is “0” when the liquid crystal molecules are vertically oriented and aligned.

For this reason, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 is the largest when no voltage is applied, that is, when the liquid crystal molecules are in the initial twist alignment state.
Due to the birefringence effect of the retardation plate 23, the elliptically polarized light of which the wavelengths are different from each other in the polarization state is largely birefringent by the liquid crystal layer 18, enters the back side polarizing plate 22, and is transmitted through this polarizing plate 22. The light becomes a colored light of a certain color.

When a voltage is applied to the liquid crystal cell 10,
The birefringence of the liquid crystal layer 18 changes according to the voltage, and light having a polarization state different from that in the state in which no voltage is applied is incident on the back side polarizing plate 22 and the light transmitted through this polarizing plate 22 is other. To the color of.

Furthermore, when a voltage is applied to the liquid crystal cell 10 so that the liquid crystal molecules rise and align substantially vertically, the birefringence of the liquid crystal layer 18 is almost lost, and the birefringence effect of the retardation plate 23 causes the light of each wavelength to be polarized. Since the different elliptically polarized lights having different polarizations pass through the liquid crystal cell 10 in that polarization state and enter the back side polarizing plate 22, at this time, the light passing through the back side polarizing plate 22 changes the phase difference plate 23. It becomes colored light only by the birefringence effect of.

The display colors of this color liquid crystal display device are the directions of the transmission axes 21a and 22a of the pair of polarizing plates 21 and 22 and the slow axis 23a of the retardation plate 23, and the orientations of both substrates 11 and 12 of the liquid crystal cell 10. Orientation direction of liquid crystal molecules in the vicinity 11
a, 12a, the value of Δn · d of the liquid crystal cell 10, the value of the retardation of the retardation film 23, and the value of the voltage applied to the liquid crystal cell 10.

The display color of this color liquid crystal display device will be described. As shown in FIG. 2, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is approximately 90 °, the transmission axis 21a of the front polarizing plate 21 and the retardation plate 23. The deviation angle from the slow axis 23a of the liquid crystal cell 1 is about 45 °, and the transmission axis 21a of the front-side polarizing plate 21 is the liquid crystal cell 1.
Orientation direction 1 of liquid crystal molecules near the front substrate 11 of 0
1a, the transmission axis 22a of the back polarizing plate 22 is substantially parallel to the transmission axis 21a of the front polarizing plate 21, the value of Δn · d of the liquid crystal cell 10 is 552 nm, and the retardation value of the retardation plate 23. Is 430 nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value, and the display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied Voltage) (Display Color) 1.7v or Less Orange 2.9 to 3.5v Black 4.5v or More Blue As described above, the display color of the color liquid crystal display device is the voltage applied to the liquid crystal cell 10. As you increase, the value changes in the order of orange → black → blue.

Here, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is about 90 °, the value Δn · d of the liquid crystal cell 10 is 552 nm, and the retardation value of the retardation plate 23 is 430 nm. When the twist angle of the liquid crystal molecule 10 is in the range of 80 ° to 110 °, the transmission axis 21a of the front-side polarizing plate 21 is substantially parallel or almost parallel to the alignment direction 11a or 12a of the liquid crystal molecule near one substrate of the liquid crystal cell 10. The transmission axis 22a of the back side polarizing plate 22 is substantially parallel or substantially orthogonal to the transmission axis 21a of the front side polarizing plate 21, and the transmission axis 2 of the front side polarizing plate 21 is orthogonal to each other.
The deviation angle of the slow axis 23a of the phase difference plate 23 with respect to 1a is 4
If it is 5 ° ± 5 °, and the value of Δn · d of the liquid crystal cell 10 is in the range of 520 nm to 580 nm and the retardation value of the retardation plate 23 is in the range of 400 nm to 460 nm, the above-mentioned orange, black, and blue display is performed. The color is obtained.

Moreover, in the color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the incident angle of light, but the birefringence of the retardation plate 23 changes the incident angle of light. However, the retardation plate 23 has a refractive index n in the x-axis direction which is the slow axis 23a.
_x , the refractive index n _y in the y-axis direction and the refractive index n in the z-axis direction
_{Since z} is a biaxial retardation plate having a relationship of n _x > n _z > _ny , the position between when light is transmitted vertically through the liquid crystal layer 18 of the liquid crystal cell 10 and when it is transmitted obliquely. Since the phase difference is compensated by the biaxial retardation plate 23, the viewing angle becomes wide.

This is because the biaxial retardation plate 23 has a retardation also in its thickness direction, and changes in the retardation with respect to the incident angle of light as compared with the normally used uniaxial retardation plate. Is small.

That is, the phase difference R _{xy in} the x and y axis directions with respect to the light incident angle of the retardation plate is the direction along the normal line of the retardation plate (the line perpendicular to the plane passing through the x axis and the y axis). When light is incident on the optical disc, that is, when the incident angle of light with respect to the normal line of the retardation plate is 0 °, the phase difference R _xy (0) is R _xy (0) = (n _x −n _y ) d ...... ( 1) (d is the thickness of the retardation plate) The phase difference R _xy (θ) when light is obliquely incident from the direction inclined by θ ° with respect to the normal line of the retardation plate is

[Equation 1] Becomes

In the ordinary uniaxial retardation plate, the refractive indices n _x , n _y and n _{z in} the x, y and z axis directions shown in FIG.
Since a _{n x> n y = n z} , a phase difference R _xy where light incident angle of the uniaxial retardation plate is 0 ° (0), when the light incident angle of theta ° phase difference R _xy Ratio with (θ) R _xy (θ) / R _xy
(0) greatly changes depending on the incident angle of light.

On the other hand, the biaxial retardation plate has x,
Refractive indices n _x , n _y , and n _{z in the} y and z axis directions are n _x > n _z
Since> _ny , R _xy (θ) / R _{depending on the} incident angle of light
The change of _xy (0) is small, and therefore the change of the phase difference due to the light incident angle is small.

That is, FIG. 4 shows the change of R _xy (θ) / R _xy (0) in the biaxial retardation plate depending on the incident angle of light, as compared with the uniaxial retardation plate. Since the R _xy (θ) / R _xy (0) of the uniaxial retardation plate largely changes depending on the incident angle of light as shown by the broken line in the figure, the phase difference increases as the incident angle of light increases. Although it changes, the biaxial retardation plate changes R _xy (θ) / R depending on the incident angle of light.
The change in _xy (0) is small as shown by the solid line in the figure, and therefore the change in the phase difference due to the light incident angle is small.

Note that R _{xy of} the uniaxial retardation plate shown in FIG.
The values of (θ) / R _xy (0) are n _x = 1.4 and n _y = n _z
= 1.2, the value of the retarder, R of the biaxial retarder
The values of _xy (θ) / R _xy (0) are n _x = 1.4 and n _y =
It is the value of the retardation plate with 1.2 and _nz = 1.3.

As described above, since the phase difference of the ordinary uniaxial retardation plate largely changes depending on the incident angle of light, when the uniaxial retardation plate is used in the color liquid crystal display device, the display color varies depending on the viewing angle. Although it changes to some extent, the change in phase difference with respect to the incident angle of light is small in the biaxial retardation plate.Therefore, if this biaxial retardation plate is used, the display color changes depending on the viewing angle, that is, the viewing angle of the display color. Dependencies are much smaller.

[0092] Figure 5 is a phase difference plate 23, x, y, the refractive indices n _x a z-axis direction, n _y, n _z is biaxial retardation in relation n _x> n _z> n _y The viewing angle and display color difference between the color liquid crystal display device of the above embodiment using a plate and a comparison device in which the retardation plate 23 is replaced with a normal uniaxial retardation plate of n _x > n _y = n _z ( ΔE ^* ab), where the solid line shows the change in color difference depending on the viewing angle of the embodiment apparatus, and the broken line shows the change in color difference depending on the viewing angle of the comparison apparatus.

In each of the device of the embodiment and the device of comparison, the liquid crystal molecule twist angle of the liquid crystal cell is approximately 90 °, the birefringence index Δn of the liquid crystal is 0.092, the liquid crystal layer thickness is 6 μm, and the transmission of the front side polarizing plate. The angle of deviation of the slow axis of the retardation plate with respect to the axis is approximately 45 °, the transmission axis of the front side polarizing plate is substantially orthogonal to the alignment direction of the liquid crystal molecules near the front side substrate of the liquid crystal cell, and the transmission axis of the back side polarizing plate is The transmission axis of the front-side polarizing plate is approximately parallel to the transmission axis, and the biaxial retardation plate used in the device of the embodiment has n _x = 1.4, n _y = 1.2, and n _z = 1.3. The retardation plate, the uniaxial retardation plate used in the comparison device has n _x = 1.4,
It is a retardation plate with n _y = n _z = 1.2. However, the plate thickness of each of these retardation films is 2.15 μm.

The color difference (ΔE ^* ab) of the display colors is
The viewing angle is 0 °, that is, a value based on the chromaticity when the display is viewed from directly in front of the display device, which is the difference between the reference chromaticity and the chromaticity of the display color at each viewing angle.

As shown in FIG. 5, a comparison is made using an ordinary uniaxial retardation plate in which the refractive indices n _x , n _y and n _z in the x, y and z axis directions are n _x > n _y = n _z. apparatus, large changes in the color difference depending on the viewing angle is, therefore is large viewing angle dependence of display colors, examples device using a biaxial retardation film of n _x> n _z> n _y, compared to the comparison device Since the change in color difference depending on the viewing angle is quite small, and the viewing angle dependency of the display color is small, the viewing angle is sufficiently wide.

Further, in the color liquid crystal display device of the above embodiment, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes with temperature, but the birefringence of the phase difference plate 23 with temperature is very small. Therefore, the liquid crystal layer 1 of the liquid crystal cell 10
The total birefringence of 8 and the retardation film 23 is a characteristic that temperature dependence is small, and therefore the color change of the display color due to temperature is also small.

Although the retardation plate 23 is provided between the front polarizing plate 21 and the liquid crystal cell 10 in the above embodiment, the retardation plate 23 is provided between the back polarizing plate 22 and the liquid crystal cell 10. It may be provided, and the slow axis 23a of the retardation plate 23 and the polarizing plate 21 (or 22) adjacent to this retardation plate 23
The deviation angle from the transmission axis 21a (or 22a) may be arbitrary. However, in order to sufficiently obtain the coloring effect of the polarization effect of the retardation plate 23, the shift angle is preferably 45 ± 5 °.

Further, the color liquid crystal display device of the above-mentioned embodiment is of a reflection type in which the reflection plate 25 is provided on the back surface thereof, but this liquid crystal display device is used as a transmission type device without the reflection plate 25. It is also possible to do so.

[Second Embodiment] In the first embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 80 ° to 80 °.
Although it is set to 110 °, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 may be set to 180 ° to 270 °.

FIG. 6 shows a second embodiment of the present invention, in which the liquid crystal molecule orientation direction of the liquid crystal cell 10, the transmission axis directions of the polarizing plates 21 and 22, and the slow axis direction of the retardation film 23. FIG. 3 is a view showing the above from the front side, and in this embodiment, the liquid crystal cell 1
The twist angle of the liquid crystal molecules of 0 is set to about 250 °.

In the color liquid crystal display device of this embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell is set to approximately 250 °. The basic structure of the entire display device is shown in FIG.
The description is omitted because it is the same as that shown in FIG.

In this embodiment, as shown in FIG. 7, the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is clockwise with respect to the horizontal axis S of the liquid crystal cell 10 when viewed from the front side. The orientation 11a of liquid crystal molecules in the vicinity of the front substrate 11 is approximately 100 °, and
With respect to the orientation direction 12a of the liquid crystal molecules in the vicinity of, the liquid crystal molecules are turned clockwise by about 70 ° when viewed from the surface side, and the liquid crystal molecules are turned clockwise when viewed from the front side substrate 11 side from the back side substrate 12 side. Twist orientation is performed at a twist angle of approximately 250 °.

Further, in this embodiment, the transmission axis 21a of the front side polarizing plate 21 and the transmission axis 22a of the back side polarizing plate 22 are oriented as follows, and the slow axis 2 of the retardation plate 23 is set.
3a is slanted by a predetermined angle with respect to the transmission axis 21a of the front polarizing plate 21.

That is, the alignment direction 12a of liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is set to the reference direction (0
Direction), the transmission axis 21a of the front polarizing plate 21
Is the liquid crystal cell 1 when viewed from the front side with respect to the reference direction.
Almost 5 in the opposite direction (counterclockwise) to the twist direction of 0 liquid crystal molecules
The transmission axis 22a of the back side polarizing plate 22 is in the direction of 5 °,
With respect to the reference direction, the direction is approximately 45 ° opposite to the twist direction of the liquid crystal molecules as viewed from the surface side.

The slow axis 23a of the retardation plate 23 is approximately 80 ° in the same direction (clockwise direction) as the liquid crystal molecule twist direction as viewed from the surface side with respect to the reference direction. The slow axis 23a of the retardation plate 23 is the front side polarizing plate 2
With respect to the transmission axis 21a of No. 1, as viewed from the front surface side, the liquid crystal molecule is displaced by 45 ° in a direction opposite to the twist direction.

Further, in this embodiment, the liquid crystal cell 10 described above is used.
Is the product Δ of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d.
The value of n · d used is 880 nm. The birefringence Δn of the liquid crystal of the liquid crystal cell 10 and the liquid crystal layer thickness d
Is Δn = 0.13 d = 6.8 μm.

The biaxial retardation plate 23 is the same as that used in the first embodiment, and its retardation value is 430 nm (n _x = 1.4, n _y = 1.2). ，
n _z = 1.3, d = 2.15 μm).

In the color liquid crystal display device of this embodiment, external light incident from the front surface side is reflected by the reflection plate 25 on the rear surface side for display, and both substrates 11, 12 of the liquid crystal cell 10 are displayed.
A display is driven by applying a voltage between the electrodes 13 and 14 of the.

In this color liquid crystal display device, while the linearly polarized light which has passed through the front-side polarizing plate 21 and is incident from the surface side thereof sequentially passes through the retardation plate 23 and the liquid crystal cell 10, the retardation plate is introduced. The polarization state is changed by the birefringence effect of 23 and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, and enters the back-side polarizing plate 22.
The light transmitted through becomes the colored light.

Explaining this coloring of light, external light entering the liquid crystal display device first enters the retardation film 23 after being transmitted through the front side polarizing plate 21 to become linearly polarized light.
The retardation plate 23 has a slow axis 23a at a predetermined angle with respect to the transmission axis 21a of the front-side polarizing plate 21 (in this embodiment, approximately 4 degrees).
5 °) Since it is obliquely displaced, the linearly polarized light that has passed through the front-side polarizing plate 21 undergoes a birefringence action according to the value of its retardation while passing through the retardation plate 23, and each wavelength light has its respective polarization state. Different elliptically polarized light.

The light transmitted through the phase difference plate 23 is
While entering the liquid crystal cell 10 and passing through the liquid crystal layer 18, the liquid crystal cell 10 is subjected to a birefringence action according to the value of Δn · d of the liquid crystal cell 10 and the alignment state of the liquid crystal molecules, and the elliptically polarized light of each wavelength light The light becomes a state that has changed further.

In this case, in this embodiment, the liquid crystal cell 10
Since the twist angle of the liquid crystal molecules is as large as approximately 250 °, the birefringence action of the liquid crystal layer 18 of the liquid crystal cell 10 is larger than that in the first embodiment described above.

Thus, the elliptically polarized light of which the respective wavelengths have different polarization states due to the birefringence effect of the retardation film 23 and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 is backside polarized light. Of the light that has entered the plate 22, only the component light along the transmission axis 22a of the back-side polarizing plate 22 passes through this back-side polarizing plate 22, and this transmitted light (linearly polarized light)
However, the colored light becomes a colored light having a color corresponding to the light amount ratio of each wavelength light that constitutes the transmitted light.

The color of this colored light corresponds to a pair of polarizing plates 21 and 2.
2, the transmission axes 21a and 22a and the slow axis 23a of the retardation plate 23, the orientation directions 11a and 12a of liquid crystal molecules near the substrates 11 and 12 of the liquid crystal cell 10, and Δn · d of the liquid crystal cell 10. And the retardation value of the retardation plate 23 are set so that the light quantity ratio of each wavelength light forming the light transmitted through the back side polarizing plate 22 becomes a ratio corresponding to a desired colored light. You can choose.

Further, the colored light transmitted through the back side polarizing plate 22 is reflected by the reflection plate 25 and is emitted to the upper surface side of the liquid crystal display device in the route opposite to the above-mentioned optical path, and the colored light displays a color image. To be done.

The colored light reflected by the reflection plate 25 is elliptically polarized light of which the respective wavelengths are different due to the birefringence effect of the retardation plate 23 and the liquid crystal layer 18 of the liquid crystal cell 10. , Light having a component along the transmission axis 22a of the back-side polarizing plate 22 and light having a very small wavelength component at the end of the wavelength range is the liquid crystal cell 10 and the retardation plate 23.
Is again birefringent and is absorbed by the front-side polarizing plate 21, the colored light that passes through the front-side polarizing plate 21 and is emitted has a better color purity than the colored light reflected by the reflecting plate 25. It becomes the light that became.

That is, in this color liquid crystal display device, the birefringence effect of the retardation plate 23, the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 and the pair of polarizing plates 21 and 22 are used without using a color filter. Since the light is colored by utilizing the polarization effect, and the light is not absorbed by the color filter, the light transmittance can be increased. Therefore, even if the color liquid crystal display device is of a reflective type, a very bright color display can be obtained.

In the color liquid crystal display device, the birefringence of the retardation plate 23 is determined by the retardation value of the retardation plate 23, but the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 is It changes depending on the change of the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes 13 and 14 of both substrates 11 and 12, and the polarization state of each wavelength light incident on the back side polarizing plate 22 changes accordingly. For,
The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell 10, and therefore, a plurality of colors can be displayed at the same location, that is, the same pixel.

The display colors of this color liquid crystal display device are the orientations of the transmission axes 21a and 22a of the pair of polarizing plates 21 and 22 and the slow axis 23a of the retardation plate 23, and the orientations of both substrates 11 and 12 of the liquid crystal cell 10. Orientation direction of liquid crystal molecules in the vicinity 11
a, 12a, the value of Δn · d of the liquid crystal cell 10, the value of the retardation of the retardation film 23, and the value of the voltage applied to the liquid crystal cell 10.

The display color of this color liquid crystal display device will be described. As shown in FIG. 6, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is approximately 250 °, the transmission axis 21a of the front side polarizing plate 21 and the retardation plate 23. Is about 45 ° with respect to the slow axis 23a, and when the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is used as a reference direction, the transmission axis 21a of the front polarizing plate 21 is When viewed from the front side with respect to the reference direction, the liquid crystal molecule twist direction of the liquid crystal cell 10 is approximately 55 ° in the opposite direction, and the transmission axis 22a of the back polarizing plate 22 is the liquid crystal molecule twist viewed from the front side with respect to the reference direction. And the slow axis 23a of the retardation plate 23 is in the direction of about 80 ° in the same direction as the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction. 1 The value of Δn · d of 0 is 880 nm,
When the retardation value of the retardation film 23 is 430 nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value, and the display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied Voltage) (Display Color) 2.04v or Less Red 2.18 to 2.22v Green 2.44v or More Blue As described above, the display color of the color liquid crystal display device is the voltage applied to the liquid crystal cell 10. As the value increases, the color changes in the order of red → green → blue, so that one pixel can display the three primary colors of light, red, green, and blue.

Here, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is approximately 250 °, and Δn · d of the liquid crystal cell 10 is
Was set to 880 nm and the retardation value of the retardation plate 23 was set to 430 nm, but the twist angle of the liquid crystal molecules of the liquid crystal cell 10 was in the range of 180 ° to 270 ° (desirably 250).
Angle ± 10 °), the shift angle of the slow axis 23a of the retardation plate 23 with respect to the transmission axis 21a of the front polarizing plate 21 is 45 ° ± 5 °.
When the alignment direction of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is the reference direction, the front polarizing plate 2
The transmission axis 21a of No. 1 is 55 ° in the direction opposite to the liquid crystal molecule twist direction of the liquid crystal cell 10 when viewed from the front side with respect to the reference direction.
± 10 ° direction, the transmission axis 22a of the back side polarizing plate 22 is 45 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction when viewed from the front side with respect to the reference direction, and the slow axis of the retardation plate 23. 23a is in a direction of 80 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction with respect to the reference direction from the surface side, and the value of Δn · d of the liquid crystal cell 10 is 850 nm to
910 nm, the retardation value of the retardation plate 23 is 40
In the range of 0 nm to 460 nm, the red, green, and blue display colors can be obtained.

Moreover, in the color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the incident angle of light, but the birefringence of the retardation plate 23 changes the incident angle of light. However, the retardation plate 23 has a refractive index n in the x-axis direction which is the slow axis 23a.
_x , the refractive index n _y in the y-axis direction and the refractive index n in the z-axis direction
_{Since z} is a biaxial retardation plate having a relationship of n _x > n _z > _ny , the position between when light is transmitted vertically through the liquid crystal layer 18 of the liquid crystal cell 10 and when it is transmitted obliquely. Since the phase difference is compensated by the biaxial retardation plate 23, the viewing angle becomes wide.

The width of this viewing angle is as described in the first embodiment. When a normal uniaxial retardation plate is used as the retardation plate 23, the display color changes to some extent depending on the viewing angle. However, since the biaxial retardation plate has a small change in the phase difference with respect to the incident angle of light, if this biaxial retardation plate is used, the change in the display color depending on the viewing angle, that is, the viewing angle dependence of the display color. Since it is considerably small, the viewing angle can be widened sufficiently.

Further, in this color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes with temperature, but the birefringence of the phase difference plate 23 with temperature changes very little, so that the liquid crystal The birefringence of the entire liquid crystal layer 18 of the cell 10 and the retardation film 23 has a characteristic that temperature dependence is small, and therefore the color change of the display color due to temperature is also small.

In the above embodiment, the retardation plate 23 is provided between the front polarizing plate 21 and the liquid crystal cell 10. However, the retardation plate 23 is provided between the back polarizing plate 22 and the liquid crystal cell 10. It may be provided, and the slow axis 23a of the retardation plate 23 and the polarizing plate 21 (or 22) adjacent to this retardation plate 23
The deviation angle from the transmission axis 21a (or 22a) may be arbitrary. However, in order to sufficiently obtain the coloring effect of the polarization effect of the retardation plate 23, the shift angle is preferably 45 ± 5 °.

Further, the color liquid crystal display device of the above-mentioned embodiment is a reflection type in which the reflection plate 25 is provided on the back surface thereof, but this liquid crystal display device is used as a transmission type device without the reflection plate 25. It is also possible to do so.

[Third Embodiment] In the second embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 180 °.
However, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 may be 110 ° to 130 °, which is slightly larger than that in the first embodiment and smaller than that in the second embodiment.

FIG. 7 shows the third embodiment of the present invention, in which the liquid crystal molecule orientation direction of the liquid crystal cell 10, the transmission axis directions of the polarizing plates 21 and 22, and the slow axis direction of the retardation film 23 are shown. FIG. 3 is a view from the front side showing the liquid crystal cell 10 in this embodiment.
The twist angle of the liquid crystal molecule is 110 ° to 130 °.

In the color liquid crystal display device of this embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell is approximately 250 °, but the basic structure of the entire display device is shown in FIG.
The description is omitted because it is the same as that shown in FIG.

In this embodiment, as shown in FIG. 7, the alignment direction 12a of liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is turned clockwise with respect to the horizontal axis S of the liquid crystal cell 10 when viewed from the front side. The direction of 30 ° ± 5 °, the alignment direction 11a of the liquid crystal molecules in the vicinity of the front side substrate 11,
With respect to the alignment direction 12a of the liquid crystal molecules in the vicinity of the direction of 60 ° ± 5 ° counterclockwise when viewed from the surface side, and the liquid crystal molecules are viewed from the front side substrate 11 side to the right side when viewed from the front side substrate 11 side. Around 120 ° ± 10 ° (110 ° ~ 130
The twist angle is (°).

Further, in this embodiment, the transmission axis 21a of the front side polarizing plate 21 and the transmission axis 22a of the back side polarizing plate 22 are oriented as follows, and the slow axis 2 of the retardation plate 23 is
3a is slanted by a predetermined angle with respect to the transmission axis 21a of the front polarizing plate 21.

That is, the transmission axis 21a of the front polarizing plate 21
When the alignment direction 12a of the liquid crystal molecules near the back substrate 12 of the liquid crystal cell 10 is the reference direction (direction of 0 °), the liquid crystal cell 1 is viewed from the front side with respect to the reference direction.
90 ° in the opposite direction (counterclockwise) to the twist direction of 0 liquid crystal molecules
The transmission axis 22a of the back side polarizing plate 22 is in the direction of ± 10 °.
Is in the direction of 50 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction.

The slow axis 23a of the retardation plate 23 is in the direction of 100 ° ± 10 ° in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side with respect to the reference direction, and this phase difference The slow axis 23a of the plate 23 is deviated from the transmission axis 21a of the front side polarizing plate 21 by 10 ° ± 5 ° in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side.

In this embodiment, the liquid crystal cell 1 described above is used.
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d is 880 nm to 970 nm (Δn = 0.1).
05 ± 0.05, d = 8.8 μm ± 0.2 μm), and the biaxial retardation plate 23 has a retardation value of 1470 nm to 1530 nm.

In the color liquid crystal display device of this embodiment, the external light incident from the front surface side is reflected by the reflection plate 25 on the rear surface side for display, and both substrates 11, 12 of the liquid crystal cell 10 are displayed.
A display is driven by applying a voltage between the electrodes 13 and 14 of the.

In this color liquid crystal display device, while the linearly polarized light which has passed through the front-side polarizing plate 21 from the front side and is incident on the retardation plate 23 and the liquid crystal cell 10 sequentially, the retardation plate is formed. The polarization state is changed by the birefringence effect of 23 and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, and enters the back-side polarizing plate 22.
The light transmitted through becomes the colored light.

Explaining the coloring of this light, the external light entering the liquid crystal display device first enters the retardation film 23 after being transmitted through the front polarizing plate 21 to become linearly polarized light.
The retardation plate 23 slow axis 23a forms a predetermined angle (10 ° in this embodiment) with respect to the transmission axis 21a of the front side polarizing plate 21.
Since the linearly polarized light transmitted through the front-side polarizing plate 21 is birefringent according to the retardation value thereof while being transmitted through the retardation plate 23, each wavelength light is polarized. It becomes elliptically polarized light in different states.

The light transmitted through the retardation plate 23 is
While entering the liquid crystal cell 10 and passing through the liquid crystal layer 18, the liquid crystal cell 10 is subjected to a birefringence action according to the value of Δn · d of the liquid crystal cell 10 and the alignment state of the liquid crystal molecules, and the elliptically polarized light of each wavelength light The light becomes a state that has changed further.

In this case, in this embodiment, the liquid crystal cell 10
Since the twist angle of the liquid crystal molecules is 120 ° ± 10 °, the birefringence action of the liquid crystal layer 18 of the liquid crystal cell 10 is larger than that in the first embodiment described above.

As described above, the elliptically polarized light of which the wavelengths are different from each other due to the birefringence effect of the retardation film 23 and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 is the backside polarized light. Of the light that has entered the plate 22, only the component light along the transmission axis 22a of the back-side polarizing plate 22 passes through this back-side polarizing plate 22, and this transmitted light (linearly polarized light)
However, the colored light becomes a colored light having a color corresponding to the light amount ratio of each wavelength light that constitutes the transmitted light.

The color of this colored light corresponds to a pair of polarizing plates 21 and 2.
2, the transmission axes 21a and 22a and the slow axis 23a of the retardation plate 23, the orientation directions 11a and 12a of liquid crystal molecules near the substrates 11 and 12 of the liquid crystal cell 10, and Δn · d of the liquid crystal cell 10. And the retardation value of the retardation plate 23 are set so that the light quantity ratio of each wavelength light forming the light transmitted through the back side polarizing plate 22 becomes a ratio corresponding to a desired colored light. You can choose.

Further, the colored light transmitted through the back side polarizing plate 22 is reflected by the reflection plate 25 and is emitted to the upper surface side of the liquid crystal display device through a route opposite to the above-mentioned optical route, and a color image is displayed by this colored light. To be done.

The colored light reflected by the reflection plate 25 is elliptically polarized light of which the respective wavelengths are different due to the birefringence effect of the retardation plate 23 and the liquid crystal layer 18 of the liquid crystal cell 10. , Light having a component along the transmission axis 22a of the back-side polarizing plate 22 and light having a very small wavelength component at the end of the wavelength range is the liquid crystal cell 10 and the retardation plate 23.
Is again birefringent and is absorbed by the front-side polarizing plate 21, the colored light that passes through the front-side polarizing plate 21 and is emitted has a better color purity than the colored light reflected by the reflecting plate 25. It becomes the light that became.

That is, in this color liquid crystal display device, the birefringence effect of the retardation plate 23, the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 and the pair of polarizing plates 21 and 22 are used without using a color filter. Since the light is colored by utilizing the polarization effect, and the light is not absorbed by the color filter, the light transmittance can be increased. Therefore, even if the color liquid crystal display device is of a reflective type, a very bright color display can be obtained.

In this color liquid crystal display device, the birefringence of the retardation plate 23 is determined by the retardation value of the retardation plate 23, but the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 is It changes depending on the change of the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes 13 and 14 of both substrates 11 and 12, and the polarization state of each wavelength light incident on the back side polarizing plate 22 changes accordingly. For,
The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell 10, and therefore, a plurality of colors can be displayed at the same location, that is, the same pixel.

The display colors of this color liquid crystal display device are the orientations of the transmission axes 21a and 22a of the pair of polarizing plates 21 and 22 and the slow axis 23a of the retardation plate 23, and the orientations of both substrates 11 and 12 of the liquid crystal cell 10. Orientation direction of liquid crystal molecules in the vicinity 11
a, 12a, the value of Δn · d of the liquid crystal cell 10, the value of the retardation of the retardation film 23, and the value of the voltage applied to the liquid crystal cell 10.

The display color of this color liquid crystal display device will be described. As shown in FIG. 7, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 120 ° ± 10 °, and the front side polarizing plate 21.
The deviation angle between the transmission axis 21a of the liquid crystal display panel 21a and the slow axis 23a of the retardation plate 23 is 10 ° ± 5 °, and the back substrate 1 of the liquid crystal cell 10 is
When the alignment direction 12a of the liquid crystal molecules near 2 is the reference direction, the transmission axis 21a of the front side polarizing plate 21 is 90 ° in the direction opposite to the twist direction of the liquid crystal molecules of the liquid crystal cell 10 when viewed from the front side with respect to the reference direction. ± 10 ° direction, back polarizing plate 2
The transmission axis 22a of 2 is 50 ° ± 10 ° in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side with respect to the reference direction, and the slow axis 23a of the retardation plate 23 is the surface side with respect to the reference direction. Seen from above, the liquid crystal molecules are in the direction of 100 ° ± 10 ° opposite to the twist direction, and Δn ·
When the value of d is 880 nm to 970 nm and the retardation value of the retardation plate 23 is 1470 nm to 1530 nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value,
The display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied voltage) (Display color) 1.20v or less Green 1.21 to 1.60v Blue 1.70 to 2.10v Red 2.11v or more White As described above, the display color of the color liquid crystal display device is , As the voltage applied to the liquid crystal cell 10 is increased, the order of change is green → blue → red → white. Therefore, in one pixel, the three primary colors of light are red, green, blue, and white. Can be displayed.

Moreover, in the color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the incident angle of light, but the birefringence of the retardation plate 23 changes the incident angle of light. However, the retardation plate 23 has a refractive index n in the x-axis direction which is the slow axis 23a.
_x , the refractive index n _y in the y-axis direction and the refractive index n in the z-axis direction
_{Since z} is a biaxial retardation plate having a relationship of n _x > n _z > _ny , the position between when light is transmitted vertically through the liquid crystal layer 18 of the liquid crystal cell 10 and when it is transmitted obliquely. Since the phase difference is compensated by the biaxial retardation plate 23, the viewing angle becomes wide.

The width of this viewing angle is as described in the first embodiment. If a normal uniaxial retardation plate is used as the retardation plate 23, the display color changes to some extent depending on the viewing angle. However, since the biaxial retardation plate has a small change in the phase difference with respect to the incident angle of light, if this biaxial retardation plate is used, the change in the display color depending on the viewing angle, that is, the viewing angle dependence of the display color. Since it is considerably small, the viewing angle can be widened sufficiently.

Further, in this color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the temperature, but the birefringence change of the retardation plate 23 due to the temperature is very small. The birefringence of the entire liquid crystal layer 18 of the cell 10 and the retardation film 23 has a characteristic that the temperature dependence is small, and therefore the color change of the display color due to the temperature is also small.

In the above embodiment, the pair of polarizing plates 2
Although the transmission axes 21a and 22a of 1 and 22 and the slow axis 23a of the retardation plate 23 are set as shown in FIG. 7, these axial directions may be set as follows, for example.

FIG. 8 shows the transmission axes 21a, 2 of the polarizing plates 21, 22 in the color liquid crystal display device of the third embodiment.
It is the figure seen from the surface side which shows the other setting example of 2a and the direction of the slow axis 23a of the phase plate 23.

In this example, the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is 30 clockwise with respect to the horizontal axis S of the liquid crystal cell 10 when viewed from the front side.
The alignment direction 11a of the liquid crystal molecules in the vicinity of the front substrate 11 is 60 ° ± 5 ° counterclockwise when viewed from the front side with respect to the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12. The liquid crystal molecules are twisted in a direction of 120 ° ± 10 ° (110 ° to 130 °) in a clockwise direction when viewed from the front side from the back substrate 12 side to the front substrate 11 side.

Then, the transmission axis 21a of the front polarizing plate 21
When the alignment direction 12a of the liquid crystal molecules near the back substrate 12 of the liquid crystal cell 10 is the reference direction (direction of 0 °), the liquid crystal cell 1 is viewed from the front side with respect to the reference direction.
30 ° in the opposite direction (counterclockwise) to the twist direction of 0 liquid crystal molecules
The transmission axis 22a of the back side polarizing plate 22 is in the direction of ± 10 °.
Is 150 ° ± 10 ° in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side with respect to the reference direction.

The slow axis 23a of the retardation plate 23 is in the direction of 100 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction as viewed from the surface side with respect to the reference direction. The slow axis 23a of the plate 23 is deviated from the transmission axis 21a of the front polarizing plate 21 by 70 ° ± 10 ° in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side.

Furthermore, in this example, as the liquid crystal cell 10, the product Δn of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d.
The value of d is 880 nm to 970 nm (Δn = 0.105
± 0.05, d = 8.8 μm ± 0.2 μm), and the biaxial retardation plate 23 having a retardation value of 1270 nm to 1330 nm is used.

As described above, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 120 ° ± 10 °, and the shift angle between the transmission axis 21a of the front polarizing plate 21 and the slow axis 23a of the retardation plate 23 is 70.
When the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is used as a reference direction, the transmission axis 21a of the front polarizing plate 21 is viewed from the front side with respect to the reference direction. A direction of 30 ° ± 10 ° in a direction opposite to the liquid crystal molecule twist direction of the liquid crystal cell 10, and a transmission axis 22a of the back polarizing plate 22 is 150 ° in a direction opposite to the liquid crystal molecule twist direction with respect to the reference direction when viewed from the surface side. In the direction of ± 10 °, the slow axis 23a of the retardation film 23 is 1 in the direction opposite to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction.
In the direction of 00 ° ± 10 °, Δn · d of the liquid crystal cell 10
When the value of is 880 nm to 970 nm and the retardation value of the retardation film 23 is 1270 nm to 1330 nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value,
The display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied voltage) (Display color) 1.30v or less White 1.31 to 1.60v Blue 1.61v or more Red That is, in this example, the display color is set by increasing the voltage applied to the liquid crystal cell 10. As it goes, it changes from white to blue to red.

Although the retardation plate 23 is provided between the front side polarizing plate 21 and the liquid crystal cell 10 in the above embodiment, the retardation plate 23 is provided between the back side polarizing plate 22 and the liquid crystal cell 10. It may be provided, and the slow axis 23a of the retardation plate 23 and the polarizing plate 21 (or 22) adjacent to this retardation plate 23
The deviation angle from the transmission axis 21a (or 22a) may be arbitrary.

Further, the color liquid crystal display device of the above-mentioned embodiment is of a reflection type in which the reflection plate 25 is provided on the back surface thereof, but this liquid crystal display device is used as a transmission type device without the reflection plate 25. It is also possible to do so.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described with reference to FIGS. 9 and 10. In the color liquid crystal display device of this embodiment, the twist angle of liquid crystal molecules is 1
A liquid crystal cell of 80 ° to 270 ° and two biaxial retardation plates are used.

FIG. 9 is a cross-sectional view of a color liquid crystal display device. This liquid crystal display device includes a liquid crystal cell 10, and a front surface side (upper surface side in the drawing) and a back surface side (in the drawing) of the liquid crystal cell 10 sandwiched therebetween. A pair of polarizing plates 2 arranged on the lower surface side)
1, 22 and the first retardation plate 23 arranged between the liquid crystal cell 10 and the front polarizing plate 21 arranged on the front surface side of the liquid crystal cell 10, and arranged on the rear surface side of the liquid crystal cell 10. It comprises a second retardation plate 24 arranged between the back side polarizing plate 22 and the liquid crystal cell 10, and a reflecting plate 25 arranged behind the back side polarizing plate 22.

The liquid crystal cell 10 has a liquid crystal molecule twist angle of 180 ° to 270 °. In this embodiment, the liquid crystal molecule twist angle is 250 ° ± 20 ° (230 ° C.).
The angle is set to ° to 270 °. Since the basic configuration of the liquid crystal cell 10 is the same as that of the liquid crystal cell in the first embodiment described above, the duplicated description will be omitted by giving the same reference numerals to the drawings.

Also, the first and second retardation plates 2
3 and 24 have a refractive index n _x in the x-axis direction, which is the slow axis, a refractive index n _{y in the y-} axis direction, and a refractive index n _{z in the} z-axis direction, n _x > n _z >. It is a biaxial phase plate having a relationship of n _y .

FIG. 10 shows the alignment directions of the liquid crystal molecules of the liquid crystal cell 10, the transmission axes of the polarizing plates 21 and 22, and the first and second retardation plates 23, 23 in the color liquid crystal display device of this embodiment. It is the figure seen from the surface side which shows the direction of the slow axis of 24.

As shown in FIG. 10, the alignment direction 12a of liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is
With respect to the horizontal axis S of the liquid crystal cell 10, a direction of 35 ° ± 10 ° counterclockwise when viewed from the front side, and an alignment direction 11a of liquid crystal molecules in the vicinity of the front substrate 11, the liquid crystal molecules in the vicinity of the back substrate 12 are With respect to the alignment direction 12a, the direction is 70 ° ± 10 ° clockwise when viewed from the surface side, and the liquid crystal molecules are
250 ° ± 20 ° (desirably 250 ° ± 20 °) clockwise when viewed from the front side from the back substrate 12 side toward the front substrate 11 side.
The twist orientation is 10 °).

Further, in this embodiment, the transmission axis 21a of the front side polarizing plate 21 and the transmission axis 22a of the back side polarizing plate 22 are oriented as follows, and between the front side polarizing plate 21 and the liquid crystal cell 10. Slow axis 2 of the first retardation plate 23 arranged in
3a is slanted at a predetermined angle with respect to the transmission axis 21a of the front-side polarizing plate 21, and further, the slow axis 2 of the second retardation plate 24 arranged between the back-side polarizing plate 22 and the liquid crystal cell 10.
4a is oriented as follows.

That is, the transmission axis 21a of the front polarizing plate 21
When the alignment direction 12a of the liquid crystal molecules near the back substrate 12 of the liquid crystal cell 10 is the reference direction (direction of 0 °), the liquid crystal cell 1 is viewed from the front side with respect to the reference direction.
80 ° in the same direction (clockwise) as the liquid crystal molecule twist direction of 0
The transmission axis 22a of the back side polarizing plate 22 is in the direction of ± 10 °.
Is 45 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction.

Further, the slow axis 2 of the first retardation plate 23 is
3a is in the direction of 35 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction, and the slow axis 23a of the retardation plate 23 is the front side polarizing plate 21. With respect to the transmission axis 21a of the above, when viewed from the surface side, it is deviated by 45 ° ± 20 ° in a direction (counterclockwise) opposite to the twist direction of the liquid crystal molecules.

Further, the slow axis 24a of the second retardation plate 24 is in the direction of 10 ° ± 10 ° in the opposite direction to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction. .

In this embodiment, the liquid crystal cell 1 described above is used.
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d is 1350 nm ± 100 nm (1250 n
m-1450 nm) is used.

In this embodiment, the first biaxial retardation plate 23 has a retardation value of 1600n.
m ± 30 nm (1570 nm to 1630 nm), Nz value [Nz = (n _x −n _z ) / (n _x −n _y )] is 0.3 to
Use 0.7 (preferably 0.45 ± 0.1),
The second biaxial retardation plate 24 has a retardation value of 1600 nm ± 30 nm (1570 nm to 1630 n).
m), Nz value is 0.3 to 0.7 (preferably 0.45 ±
0.1) is used.

In the color liquid crystal display device of this embodiment, external light incident from the front side is reflected by the reflection plate 25 on the back side for display, and both substrates 11, 12 of the liquid crystal cell 10 are displayed.
A display is driven by applying a voltage between the electrodes 13 and 14 of the.

In this color liquid crystal display device, the linearly polarized light which has passed through the front side polarizing plate 21 from the front side thereof and is incident thereon has the first retardation plate 23, the liquid crystal cell 10 and the second retardation plate 23.
Of the phase difference plate 2 while sequentially passing through the phase difference plate 24 of
3, 24 birefringence effect and liquid crystal layer 18 of liquid crystal cell 10
Polarizing state can be changed by the birefringence effect of
The light that has entered 2 and transmitted through this back-side polarizing plate 22 becomes colored light.

Explaining the coloring of this light, the external light entering the liquid crystal display device first enters the first retardation plate 23 after passing through the front side polarizing plate 21 to become linearly polarized light. Since the slow axis 23a of the retardation film 23 is slanted at a predetermined angle (45 ° ± 20 ° in this embodiment) with respect to the transmission axis 21a of the front polarizing plate 21, the front polarizing plate 2
The linearly polarized light having passed through 1 is subjected to a birefringence action according to the value of its retardation while passing through the first retardation plate 23, and each wavelength light becomes elliptically polarized light having a different polarization state.

The light transmitted through the first retardation plate 23 is incident on the liquid crystal cell 10 and while passing through the liquid crystal layer 18, the value of Δn · d and the liquid crystal molecules of the liquid crystal cell 10 are changed. By the birefringence action depending on the orientation state, the light having the elliptically polarized state of each wavelength light is further changed.

In this case, in this embodiment, the liquid crystal cell 10
Since the twist angle of the liquid crystal molecules is 250 ° ± 20 °, the birefringence action of the liquid crystal layer 18 of the liquid crystal cell 10 is larger than that of the first embodiment described above.

Further, the light transmitted through the liquid crystal cell is incident on the second retardation plate 24 and is subjected to the birefringence action according to the retardation value thereof, and the elliptically polarized state of each wavelength light is further changed. It becomes the light.

As described above, the first retardation film 23
Due to the birefringence effect of 1), the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 and the birefringence effect of the second retardation plate 24, light of each wavelength becomes elliptically polarized light having different polarization states. The light enters the backside polarizing plate 22 of
Of the component along the transmission axis 22a of the light is transmitted through the back side polarizing plate 22, and the transmitted light (linearly polarized light) is a colored light of a color corresponding to the light quantity ratio of each wavelength light constituting the transmitted light. become.

The color of this colored light depends on the pair of polarizing plates 21 and 2.
Two transmission axes 21a, 22a and two retardation plates 23,
The orientations of the slow axes 23a and 24a of 24 and the alignment direction 1 of the liquid crystal molecules in the vicinity of both substrates 11 and 12 of the liquid crystal cell 10.
1a and 12a, the value of Δn · d of the liquid crystal cell 10, and the first
The retardation value of the retardation plate 23 and the retardation value of the second retardation plate 24 are set so that the light amount ratio of each wavelength light component of the light transmitted through the back side polarizing plate 22 corresponds to the desired colored light. It can be arbitrarily selected by setting the ratio.

Further, the colored light transmitted through the back side polarizing plate 22 is reflected by the reflection plate 25 and emitted to the upper surface side of the liquid crystal display device through a route opposite to the above-mentioned optical route, and the colored light displays a color image. To be done.

The colored light reflected by the reflector 25 is elliptically polarized light whose wavelengths are different from each other due to the birefringence effect of the phase difference plates 23 and 24 and the liquid crystal layer 18 of the liquid crystal cell 10. The transmission axis 2 of the back side polarizing plate 22
The light having only the component along 2a, and the light having a very small wavelength component at the end of the wavelength range is transmitted through the second retardation plate 24, the liquid crystal cell 10 and the first retardation plate 23 again. Since the birefringent light is absorbed by the front-side polarizing plate 21 in the process of being processed, the colored light that passes through the front-side polarizing plate 21 and is emitted has a higher color purity than the colored light reflected by the reflecting plate 25. Becomes

That is, in this color liquid crystal display device, the birefringence effect of the two retardation films 23 and 24, the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 and the pair of polarized lights are used without using a color filter. The light is colored by utilizing the polarization effect of the plates 21 and 22, and therefore the light is not absorbed by the color filter, so that the light transmittance can be increased. Therefore, even if the color liquid crystal display device is of a reflective type, a very bright color display can be obtained.

In this color liquid crystal display device, the birefringence of the retardation plates 23 and 24 is determined by the retardation value of the retardation plates 23 and 24.
The birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 depends on the substrate 1
1, 12 changes depending on the change in the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes 13 and 14, and accordingly the polarization state of each wavelength light incident on the back side polarizing plate 22 changes. The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell 10, and therefore, a plurality of colors can be displayed at the same location, that is, the same pixel.

The display colors of this color liquid crystal display device are the orientations of the transmission axes 21a and 22a of the pair of polarizing plates 21 and 22 and the slow axes 23a and 24a of the two retardation plates 23 and 24, and the liquid crystal cell 10. The alignment directions 11a and 12a of the liquid crystal molecules in the vicinity of both substrates 11 and 12, and Δ of the liquid crystal cell 10.
It is determined by the value of n · d, the retardation value of the retardation films 23 and 24, and the voltage value applied to the liquid crystal cell 10.

The display color of this color liquid crystal display device will be described. As shown in FIG. 10, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 °, and the front side polarizing plate 2
No. 1 adjacent to the transmission axis 21a and the front side polarizing plate 21
Of the phase difference plate 23 with respect to the slow axis 23a is 45 ° ± 2
When the angle is 0 ° and the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is the reference direction,
The transmission axis 21a of the front polarizing plate 21 is 80 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction of the liquid crystal cell 10 when viewed from the front side with respect to the reference direction, and the transmission axis 2 of the back polarizing plate 22.
2a is a direction of 45 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction when viewed from the front side with respect to the reference direction, and the slow axis 23a of the first retardation plate 23 is the front side with respect to the reference direction. Seen from above, 3 in the same direction as the liquid crystal molecule twist direction
Second direction adjacent to the back polarizing plate 22 in the direction of 5 ° ± 10 °
The retardation axis 24a of the retardation plate 24 is 10 in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side with respect to the reference direction.
The liquid crystal cell 10 has a Δn · d value of 1300 nm ± 100 nm, a retardation value of the first retardation plate 23 of 1500 nm ± 30 nm, and a retardation value of the second retardation plate 24. Is 1500 nm ± 30
In the case of nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value, and the display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied Voltage) (Display Color) 2.32v or Less Red Purple 2.42 to 2.60v White 2.98 to 3.02v Blue Purple 3.5v or More Black Thus, the display color of the color liquid crystal display device Changes in the order of reddish purple → white → blue purple → black as the voltage applied to the liquid crystal cell 10 is increased.

In addition, in the above color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the incident angle of light, but the birefringence of the phase difference plates 23 and 24 depends on the incident angle of light. Even if it changes, it hardly changes, and
The retardation plates 23 and 24 are both the slow axis 23
a, the refractive indices n _x in the x axis direction is 24a, and the refractive index n _z in the refractive index n _y and z-axis direction of the y-axis direction, n _x> n
_{Since the} biaxial retardation plate has a relationship of _z > _ny, the phase difference between when the light vertically passes through the liquid crystal layer 18 of the liquid crystal cell 10 and when the light obliquely passes through the biaxial retardation plate. Plate 23,
Since it is compensated by 24, the viewing angle becomes wide.

The width of this viewing angle is as described in the first embodiment. When a normal uniaxial retardation plate is used as the retardation plate 23, the display color changes to some extent depending on the viewing angle. However, since the biaxial retardation plate has a small change in the phase difference with respect to the incident angle of light, if this biaxial retardation plate is used, the change in the display color depending on the viewing angle, that is, the viewing angle dependence of the display color. It gets quite small.

Further, in this color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes with temperature, but the birefringence of the phase difference plates 23 and 24 changes very little because of the temperature. The liquid crystal layer 18 of the liquid crystal cell 10
The total birefringence of the phase difference plates 23 and 24 is a characteristic that temperature dependence is small.

In this embodiment, since the two biaxial retardation plates 23 and 24 are used, the above-mentioned first to third embodiments in which one biaxial retardation plate is used. Than the example
The phase difference between when light vertically passes through the liquid crystal layer 18 of the liquid crystal cell 10 and when it obliquely passes is more effectively compensated by the two biaxial retardation plates 23 and 24. Is further widened, and since the birefringence of the liquid crystal layer of the liquid crystal cell and the two retardation plates has a characteristic that the temperature dependence is smaller, the color change of the display color due to the temperature is also smaller. can do.

In the above embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 ° (desirably 2).
50 ° ± 10 °), but this twist angle is 180
It may be in the range of ° to 270 °.

Further, the color liquid crystal display device of the above-mentioned embodiment is a reflection type in which the reflection plate 25 is provided on the back surface thereof, but this liquid crystal display device is used as a transmission type device without the reflection plate 25. It is also possible to do so.

[Fifth Embodiment] Next, a fifth embodiment of the present invention will be described with reference to FIGS. 11 and 12. The color liquid crystal display device of this embodiment uses a liquid crystal cell in which liquid crystal molecules have a twist angle of 180 ° to 270 ° and two biaxial retardation plates.

FIG. 11 is a cross-sectional view of a color liquid crystal display device. This liquid crystal display device includes a liquid crystal cell 10 and a front surface side (upper surface side in the drawing) and a back surface side (in the drawing) of the liquid crystal cell 10 sandwiched therebetween. A pair of polarizing plates 2 arranged on the lower surface side)
1, 22 and two front-side polarizing plates 21 arranged on the front surface side of the liquid crystal cell 10 and two retardation plates 23 and 24 arranged to overlap each other between the liquid crystal cell 10 and the back-side polarizing plate 2
2 and a reflecting plate 25 arranged behind it.

The liquid crystal cell 10 has a liquid crystal molecule twist angle of 180 ° to 270 °. In this embodiment, the liquid crystal molecule twist angle is 250 ° ± 20 °. Since the basic configuration of the liquid crystal cell 10 is the same as that of the liquid crystal cell in the first embodiment described above, the duplicated description will be omitted by giving the same reference numerals to the drawings.

The two phase difference plates 23 and 24 are
In each case, the refractive index n _x in the x-axis direction, which is the slow axis,
and refractive index n _z in the refractive index n _y and z-axis direction of the y-axis direction, a biaxial phase plate having a relationship of _{n x> n z> n y} .

FIG. 12 shows the alignment directions of the liquid crystal molecules of the liquid crystal cell 10, the transmission axes of the polarizing plates 21 and 22, and the slow axes of the retardation films 23 and 24 in the color liquid crystal display device of this embodiment. It is the figure seen from the surface side which shows the direction.

As shown in FIG. 12, the alignment direction 12a of liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is
With respect to the horizontal axis S of the liquid crystal cell 10, a direction of 35 ° ± 10 ° counterclockwise when viewed from the front side, and an alignment direction 11a of liquid crystal molecules in the vicinity of the front substrate 11, the liquid crystal molecules in the vicinity of the back substrate 12 are With respect to the alignment direction 12a, the direction is 70 ° ± 10 ° clockwise when viewed from the surface side, and the liquid crystal molecules are
250 ° ± 20 ° (desirably 250 ° ± 20 °) clockwise when viewed from the front side from the back substrate 12 side toward the front substrate 11 side.
The twist orientation is 10 °).

Further, in this embodiment, the transmission axis 21a of the front side polarizing plate 21 and the transmission axis 22a of the back side polarizing plate 22 are oriented as follows, and the two phase difference plates 23 are arranged.
Of the first retardation film 23 adjacent to the front polarizing plate 21
Of the slow axis 23a of the front side polarizing plate 21 of the transmission axis 21a
And the slow axis 24a of the second retardation plate 24 adjacent to the liquid crystal cell 10 is oriented obliquely by a predetermined angle with respect to the following.

That is, the transmission axis 21a of the front polarizing plate 21
When the alignment direction 12a of the liquid crystal molecules near the back substrate 12 of the liquid crystal cell 10 is the reference direction (direction of 0 °), the liquid crystal cell 1 is viewed from the front side with respect to the reference direction.
50 ° in the opposite direction (counterclockwise) to the twist direction of 0 liquid crystal molecules
The transmission axis 22a of the back side polarizing plate 22 is in the direction of ± 10 °.
Is 45 ° ± 10 ° in the same direction (clockwise) as the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction.

The slow axis 23a of the first retardation plate 23
Is in the direction of 25 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction as viewed from the surface side with respect to the reference direction, and the slow axis 23a of the retardation plate 23 is the front side polarizing plate 2
The transmission axis 21a of No. 1 is displaced by 75 ° ± 20 ° in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side.

Furthermore, the slow axis 24 of the second retardation plate 24
a is in the direction of 15 ° ± 10 ° in the opposite direction to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction. The deviation angle between the slow axis 24a of the second retardation plate 24 and the slow axis 23a of the first retardation plate 23 is 40 ° ±.
It is 20 °.

In this embodiment, the liquid crystal cell 1 described above is used.
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d is 1350 nm ± 100 nm (1250 n
m-1450 nm) is used.

In this embodiment, the first biaxial retardation plate 23 has a retardation value of 1600n.
m ± 30 nm (1570 nm to 1630 nm), Nz value [Nz = (n _x −n _z ) / (n _x −n _y )] is 0.3 to
Use 0.7 (preferably 0.45 ± 0.1),
The second biaxial retardation plate 24 has a retardation value of 1550 nm ± 30 nm (1520 nm to 1580 n).
m), Nz value is 0.3 to 0.7 (preferably 0.45 ±
0.1) is used.

In the color liquid crystal display device of this embodiment, external light incident from the front surface side is reflected by the reflection plate 25 on the rear surface side for display, and both substrates 11, 12 of the liquid crystal cell 10 are displayed.
A display is driven by applying a voltage between the electrodes 13 and 14 of the.

In this color liquid crystal display device, the linearly polarized light which has passed through the front side polarizing plate 21 from the front side thereof and is incident thereon has the first retardation plate 23 and the second retardation plate 24.
And the liquid crystal cell 10 are sequentially transmitted, the phase difference plate 2
3, 24 birefringence effect and liquid crystal layer 18 of liquid crystal cell 10
Polarizing state can be changed by the birefringence effect of
The light that has entered 2 and transmitted through this back-side polarizing plate 22 becomes colored light.

Explaining the coloring of this light, the external light entering the liquid crystal display device first enters the first retardation plate 23 after passing through the front side polarizing plate 21 to become linearly polarized light. Since the slow axis 23a of the retardation plate 23 is obliquely displaced from the transmission axis 21a of the front side polarizing plate 21 by a predetermined angle (50 ° ± 20 ° in this embodiment), the front side polarizing plate 2
The linearly polarized light having passed through 1 is subjected to a birefringence action according to the value of its retardation while passing through the first retardation plate 23, and each wavelength light becomes elliptically polarized light having a different polarization state.

The light transmitted through the first retardation plate 23 is incident on the second retardation plate 24 and is subjected to the birefringence action according to the retardation value thereof, so that the elliptically polarized light of each wavelength light is obtained. The state of becomes a light that has changed further.

Further, the light transmitted through the second retardation plate 24 enters the liquid crystal cell 10 and while passing through the liquid crystal layer 18, the value of Δn · d of the liquid crystal cell 10 and the liquid crystal molecule By the birefringence action depending on the orientation state, the light having the elliptically polarized state of each wavelength light is further changed.

In this case, in this embodiment, the liquid crystal cell 10
Since the twist angle of the liquid crystal molecules is 250 ° ± 20 °, the birefringence action of the liquid crystal layer 18 of the liquid crystal cell 10 is larger than that of the first embodiment described above.

Then, as described above, the first retardation film 23
Due to the birefringence effect of the above, the birefringence effect of the second retardation plate 24, and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, the light whose wavelengths have become elliptically polarized lights having different polarization states is the back side polarization plate. The light enters the backside polarizing plate 22 of
Of the component along the transmission axis 22a of the light is transmitted through the back side polarizing plate 22, and the transmitted light (linearly polarized light) is a colored light of a color corresponding to the light quantity ratio of each wavelength light constituting the transmitted light. become.

The color of this colored light is the same as that of the pair of polarizing plates 21 and 2.
Two transmission axes 21a, 22a and two retardation plates 23,
The orientations of the slow axes 23a and 24a of 24 and the alignment direction 1 of the liquid crystal molecules in the vicinity of both substrates 11 and 12 of the liquid crystal cell 10.
1a and 12a, the value of Δn · d of the liquid crystal cell 10, and the first
The retardation value of the retardation plate 23 and the retardation value of the second retardation plate 24 are set so that the light amount ratio of each wavelength light component of the light transmitted through the back side polarizing plate 22 corresponds to the desired colored light. It can be arbitrarily selected by setting the ratio.

Further, the colored light transmitted through the back side polarizing plate 22 is reflected by the reflection plate 25 and emitted to the upper surface side of the liquid crystal display device through a route opposite to the above-mentioned optical route, and the colored light displays a color image. To be done.

The colored light reflected by the reflecting plate 25 is elliptically polarized light of which wavelengths are different from each other due to the birefringence effect of the phase difference plates 23 and 24 and the liquid crystal layer 18 of the liquid crystal cell 10. The transmission axis 2 of the back side polarizing plate 22
The light having only the component along 2a and the light having a very small wavelength component at the end of the wavelength range is transmitted through the liquid crystal cell 10, the second retardation plate 24, and the first retardation plate 23 again. Since the birefringent light is absorbed by the front-side polarizing plate 21 in the process of being processed, the colored light that passes through the front-side polarizing plate 21 and is emitted has a higher color purity than the colored light reflected by the reflecting plate 25. Becomes

That is, this color liquid crystal display device uses the birefringence effect of the two retardation plates 23 and 24, the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, and the pair of polarized lights without using the color filter. The light is colored by utilizing the polarization effect of the plates 21 and 22, and therefore the light is not absorbed by the color filter, so that the light transmittance can be increased. Therefore, even if the color liquid crystal display device is of a reflective type, a very bright color display can be obtained.

Further, in this color liquid crystal display device, the birefringence of the retardation plates 23 and 24 is determined by the retardation value of the retardation plates 23 and 24.
The birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 depends on the substrate 1
1, 12 changes depending on the change in the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes 13 and 14, and accordingly the polarization state of each wavelength light incident on the back side polarizing plate 22 changes. The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell 10, and therefore, a plurality of colors can be displayed at the same location, that is, the same pixel.

The display colors of this color liquid crystal display device are the orientations of the transmission axes 21a and 22a of the pair of polarizing plates 21 and 22 and the slow axes 23a and 24a of the two retardation plates 23 and 24, and the liquid crystal cell 10. The alignment directions 11a and 12a of the liquid crystal molecules in the vicinity of both substrates 11 and 12, and Δ of the liquid crystal cell 10.
It is determined by the value of n · d, the retardation value of the retardation films 23 and 24, and the voltage value applied to the liquid crystal cell 10.

The display color of this color liquid crystal display device will be described. As shown in FIG. 12, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 °, and the front side polarizing plate 2
No. 1 adjacent to the transmission axis 21a and the front side polarizing plate 21
Of the phase difference plate 23 with respect to the slow axis 23a is 75 ° ± 2
When the angle is 0 ° and the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is the reference direction,
The transmission axis 21a of the front polarizing plate 21 is 50 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction of the liquid crystal cell 10 when viewed from the front side with respect to the reference direction, and the transmission axis 2 of the back polarizing plate 22.
2a is a direction of 45 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction when viewed from the front side with respect to the reference direction, and the slow axis 23a of the first retardation plate 23 is the front side with respect to the reference direction. When viewed from the above, the liquid crystal molecule is twisted in the same direction as the 2
Second direction adjacent to the liquid crystal cell 10 in the direction of 5 ° ± 10 °
The retardation axis 24a of the retardation plate 24 is 15 in the direction opposite to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction.
The liquid crystal cell 10 has a Δn · d value of approximately 1390 nm, a retardation value of the first retardation plate 23 of 1600 nm ± 30 nm, and a second retardation plate 2
When the retardation value of 4 is 1550 nm ± 30 nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value, and the display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied voltage) (Display color) 2.04v or less White 2.15 to 2.17v Red 2.18 to 2.22v Blue 2.26v or more Green As described above, the display color of the color liquid crystal display device is As the voltage applied to the liquid crystal cell 10 is increased, it changes in the order of white → red → blue → green.

Here, Δn · d of the liquid crystal cell 10 is
Although the value of Δn · d is set to approximately 1390 nm, the value of Δn · d is 1250 nm to 1450 nm (1350 nm ± 100 n
Within the range of m), the display colors of white, red, blue and green can be obtained.

In addition, in the above color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the incident angle of light, but the birefringence of the phase difference plates 23 and 24 depends on the incident angle of light. Even if it changes, it hardly changes, and
The retardation plates 23 and 24 are both the slow axis 23
a, the refractive indices n _x in the x axis direction is 24a, and the refractive index n _z in the refractive index n _y and z-axis direction of the y-axis direction, n _x> n
_{Since the} biaxial retardation plate has a relationship of _z > _ny, the phase difference between when the light vertically passes through the liquid crystal layer 18 of the liquid crystal cell 10 and when the light obliquely passes through the biaxial retardation plate. Plate 23,
Since it is compensated by 24, the viewing angle becomes wide.

The width of this viewing angle is as described in the first embodiment. If a normal uniaxial retardation plate is used as the retardation plate 23, the display color changes to some extent depending on the viewing angle. However, since the biaxial retardation plate has a small change in the phase difference with respect to the incident angle of light, if this biaxial retardation plate is used, the change in the display color depending on the viewing angle, that is, the viewing angle dependence of the display color. It gets quite small.

Further, in this color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes with temperature, but the birefringence of the phase difference plates 23 and 24 changes very little. The liquid crystal layer 18 of the liquid crystal cell 10
The total birefringence of the phase difference plates 23 and 24 is a characteristic that temperature dependence is small.

In this embodiment, since the two biaxial retardation plates 23 and 24 are used, the above-mentioned first to third embodiments using one biaxial retardation plate. Than the example
The phase difference between when light vertically passes through the liquid crystal layer 18 of the liquid crystal cell 10 and when it obliquely passes is more effectively compensated by the two biaxial retardation plates 23 and 24. Is further widened, and since the birefringence of the liquid crystal layer of the liquid crystal cell and the two retardation plates has a characteristic that the temperature dependence is smaller, the color change of the display color due to the temperature is also smaller. can do.

In the above embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 ° (desirably 2).
50 ° ± 10 °), but this twist angle is 180
It may be in the range of ° to 270 °.

Further, the color liquid crystal display device of the above-mentioned embodiment is a reflection type in which the reflection plate 25 is provided on the back surface thereof, but this liquid crystal display device is used as a transmission type device without the reflection plate 25. It is also possible to do so.

[Sixth Embodiment] In the fifth embodiment, the value of Δn · d of the liquid crystal cell 10 is 1250 nm to 1 nm.
The value of Δn · d of this liquid crystal molecule is 450 nm.
You may make it large as 1490 nm or more.

FIG. 13 shows the sixth embodiment of the present invention.
Liquid crystal molecule orientation direction of the liquid crystal cell 10 and the polarizing plates 21 and 22
FIG. 6 is a view showing the direction of the transmission axis of and the direction of the slow axis of the phase difference plates 23 and 24 as viewed from the surface side.

In the color liquid crystal display device of this embodiment, the value of Δn · d of the liquid crystal cell 10 is increased to 1490 nm or more, but the basic structure of the entire display device is shown in FIG. Since it is the same as the above, its explanation is omitted.

In this embodiment, as shown in FIG. 13, the alignment direction 12a of liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is counterclockwise when viewed from the front side with respect to the horizontal axis S of the liquid crystal cell 10. The direction of 30 ° ± 10 °, the alignment direction 11a of liquid crystal molecules in the vicinity of the front substrate 11, and the alignment direction 12a of liquid crystal molecules in the vicinity of the back substrate 12,
The direction of rotation is 60 ° ± 10 ° clockwise when viewed from the front surface side, and the liquid crystal molecules are rotated from the back substrate 12 side toward the front substrate 11 side in a clockwise direction when viewed from the surface side 240 ° ± 20 ° (desirably 240 °). Twist orientation is performed at a twist angle of ± 10 °.

Further, in this embodiment, the transmission axis 21a of the front side polarizing plate 21 and the transmission axis 22a of the back side polarizing plate 22 are oriented as follows, and the two retardation plates 23 are
Of the first retardation film 23 adjacent to the front polarizing plate 21
Of the slow axis 23a of the front side polarizing plate 21 of the transmission axis 21a
And the slow axis 24a of the second retardation plate 24 adjacent to the liquid crystal cell 10 is oriented obliquely by a predetermined angle with respect to the following.

That is, the transmission axis 21a of the front polarizing plate 21.
When the alignment direction 12a of the liquid crystal molecules near the back substrate 12 of the liquid crystal cell 10 is the reference direction (direction of 0 °), the liquid crystal cell 1 is viewed from the front side with respect to the reference direction.
50 ° in the opposite direction (counterclockwise) to the twist direction of 0 liquid crystal molecules
The transmission axis 22a of the back side polarizing plate 22 is in the direction of ± 10 °.
Is 45 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction as viewed from the surface side with respect to the reference direction.

Also, the slow axis 23a of the first retardation plate 23
Is 30 ° ± 10 ° in the same direction (clockwise) as the liquid crystal molecule twist direction with respect to the reference direction, and the slow axis 23a of the retardation plate 23 is the front side. The transmission axis 21a of the polarizing plate 21 is offset by 80 ° ± 20 ° in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side.

Further, the slow axis 24 of the second retardation plate 24
The angle a is 20 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction. A deviation angle between the slow axis 24a of the second retardation plate 24 and the slow axis 23a of the first retardation plate 23 is 50 ° ±.
It is 20 °.

In this embodiment, the liquid crystal cell 1 described above is used.
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d is 1490 nm or more, for example, 1490n.
m-1590 nm) is used.

In this embodiment, the first biaxial retardation plate 23 has a retardation value of 1600n.
m ± 30 nm (1570 nm to 1630 nm), and the second biaxial retardation plate 24 has a retardation value of 1450 nm ± 30 nm (1420 nm to 1520 nm).
30 nm) is used.

The color liquid crystal display device of this embodiment displays external light incident from the front surface side by reflecting the light on the rear surface side reflection plate 25, and displays both substrates 11 and 12 of the liquid crystal cell 10.
A display is driven by applying a voltage between the electrodes 13 and 14 of the.

In this color liquid crystal display device, the linearly polarized light which has passed through the front side polarizing plate 21 from the front side thereof and is incident thereon has the first retardation plate 23 and the second retardation plate 24.
And the liquid crystal cell 10 are sequentially transmitted, the phase difference plate 2
3, 24 birefringence effect and liquid crystal layer 18 of liquid crystal cell 10
Polarizing state can be changed by the birefringence effect of
The light that has entered 2 and transmitted through this back-side polarizing plate 22 becomes colored light.

Explaining the coloring of this light, external light entering the liquid crystal display device first enters the first retardation plate 23 after being transmitted through the front polarizing plate 21 to become linearly polarized light. Since the slow axis 23a of the retardation plate 23 is obliquely displaced from the transmission axis 21a of the front side polarizing plate 21 by a predetermined angle (80 ° ± 20 ° in this embodiment), the front side polarizing plate 2
The linearly polarized light having passed through 1 is subjected to a birefringence action according to the value of its retardation while passing through the first retardation plate 23, and each wavelength light becomes elliptically polarized light having a different polarization state.

The light transmitted through the first retardation plate 23 is incident on the second retardation plate 24, and is subjected to the birefringence action according to the retardation value thereof, so that the elliptically polarized light of each wavelength light is obtained. The state of becomes a light that has changed further.

Further, the light transmitted through the second retardation plate 24 is incident on the liquid crystal cell 10 and while passing through the liquid crystal layer 18, the value of Δn · d and the liquid crystal molecules of the liquid crystal cell 10 are changed. By the birefringence action depending on the orientation state, the light having the elliptically polarized state of each wavelength light is further changed.

In this case, in this embodiment, the liquid crystal cell 10
Since the twist angle of the liquid crystal molecules is 240 ° ± 20 °, the birefringence action of the liquid crystal layer 18 of the liquid crystal cell 10 is larger than that of the first embodiment described above.

Then, in this way, the first retardation film 23
Due to the birefringence effect of the above, the birefringence effect of the second retardation plate 24, and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, the light whose wavelengths have become elliptically polarized lights having different polarization states is the back side polarization plate. The light enters the backside polarizing plate 22 of
Of the component along the transmission axis 22a of the light is transmitted through the back side polarizing plate 22, and the transmitted light (linearly polarized light) is a colored light of a color corresponding to the light quantity ratio of each wavelength light constituting the transmitted light. become.

The color of this colored light depends on the pair of polarizing plates 21 and 2.
Two transmission axes 21a, 22a and two retardation plates 23,
The orientations of the slow axes 23a and 24a of 24 and the alignment direction 1 of the liquid crystal molecules in the vicinity of both substrates 11 and 12 of the liquid crystal cell 10.
1a and 12a, the value of Δn · d of the liquid crystal cell 10, and the first
The retardation value of the retardation plate 23 and the retardation value of the second retardation plate 24 are set so that the light amount ratio of each wavelength light component of the light transmitted through the back side polarizing plate 22 corresponds to the desired colored light. It can be arbitrarily selected by setting the ratio.

Further, the colored light transmitted through the back side polarizing plate 22 is reflected by the reflection plate 25 and emitted to the upper surface side of the liquid crystal display device through a route opposite to the above-mentioned optical route, and a color image is displayed by this colored light. To be done.

The colored light reflected by the reflecting plate 25 is an elliptically polarized light whose wavelengths are different due to the birefringence effect of the phase difference plates 23 and 24 and the liquid crystal layer 18 of the liquid crystal cell 10. The transmission axis 2 of the back side polarizing plate 22
The light having only the component along 2a and the light having a very small wavelength component at the end of the wavelength range is transmitted through the liquid crystal cell 10, the second retardation plate 24, and the first retardation plate 23 again. Since the birefringent light is absorbed by the front-side polarizing plate 21 in the process of being processed, the colored light that passes through the front-side polarizing plate 21 and is emitted has a higher color purity than the colored light reflected by the reflecting plate 25. Becomes

That is, in this color liquid crystal display device, the birefringence effect of the two retardation plates 23 and 24, the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 and the pair of polarized lights are used without using a color filter. The light is colored by utilizing the polarization effect of the plates 21 and 22, and therefore the light is not absorbed by the color filter, so that the light transmittance can be increased. Therefore, even if the color liquid crystal display device is of a reflective type, a very bright color display can be obtained.

In this color liquid crystal display device, the birefringence of the retardation plates 23 and 24 is determined by the retardation value of the retardation plates 23 and 24.
The birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 depends on the substrate 1
1, 12 changes depending on the change in the alignment state of the liquid crystal molecules depending on the voltage applied between the electrodes 13 and 14, and accordingly the polarization state of each wavelength light incident on the back side polarizing plate 22 changes. The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell 10, and therefore, a plurality of colors can be displayed at the same location, that is, the same pixel.

The display colors of the color liquid crystal display device are as follows: the transmission axes 21a and 22a of the pair of polarizing plates 21 and 22 and the directions of the slow axes 23a and 24a of the two retardation plates 23 and 24, and the liquid crystal cell 10. The alignment directions 11a and 12a of the liquid crystal molecules in the vicinity of both substrates 11 and 12, and Δ of the liquid crystal cell 10.
It depends on the value of n · d and the retardation values of the retardation films 23 and 24 and the value of the voltage applied to the liquid crystal cell 10. In the color liquid crystal display device of this embodiment, the value of Δn · d of the liquid crystal cell is Since it is as large as 1490 nm to 1590 nm, the change in birefringence with respect to the applied voltage of the liquid crystal layer 18 is large, so that the number of display colors can be increased.

The display color of this color liquid crystal display device will be described. As shown in FIG. 13, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 240 ° ± 20 °, and the front side polarizing plate 2
No. 1 adjacent to the transmission axis 21a and the front side polarizing plate 21
Of the phase difference plate 23 with respect to the slow axis 23a is 80 ° ± 2
When the angle is 0 ° and the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is the reference direction,
The transmission axis 21a of the front polarizing plate 21 is 50 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction of the liquid crystal cell 10 when viewed from the front side with respect to the reference direction, and the transmission axis 2 of the back polarizing plate 22.
2a is a direction of 45 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction with respect to the reference direction, and the slow axis 23a of the first retardation plate 23 is the surface side with respect to the reference direction. Seen from above, 3 in the same direction as the liquid crystal molecule twist direction
Second direction adjacent to the liquid crystal cell 10 in the direction of 0 ° ± 10 °
The slow axis 24a of the retardation plate 24 is 20 in the direction opposite to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction.
The value of Δn · d of the liquid crystal cell 10 is 1490 nm to 1590 nm, the retardation value of the first retardation plate 23 is 1600 nm ± 30 nm, and the retardation value of the second retardation plate 24 is in the direction of ± 10 °. Is 1450nm ± 3
When the thickness is 0 nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value, and the display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied voltage) (Display color) 1.30v or less White 1.81 to 2.10v Black 2.11 to 2.20v Blue 2.21 to 2.60v Yellow green 2.61v or more Pink FIG. FIG. 6 is a CIE chromaticity diagram showing a change in display color of a color liquid crystal display device. The display color of this color liquid crystal display device is white → black → blue as the voltage applied to the liquid crystal cell 10 is increased. → It changes in the order of yellow-green → pink.

FIG. 15 shows the relationship between the applied voltage to the liquid crystal cell 10 in the color liquid crystal display device, the emission rate of light in the wavelength regions of red R, green G, and blue B, and the display color. Shows.

As shown in FIG. 15, in the color liquid crystal display device, when the voltage for displaying "white" is applied, the emission rates of light in the respective wavelength regions of red R, green G and blue B are almost the same, In addition, the value is sufficiently high, and therefore, it is possible to display almost completely achromatic bright "white", and the wavelength ranges of red R, green G, and blue B when a voltage for displaying "black" is applied. Since the light emission rate of is almost the same and its value is low enough,
Highly pure "black" can be displayed.

Moreover, in the color liquid crystal display device described above, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the incident angle of light, but the birefringence of the phase difference plates 23 and 24 varies depending on the incident angle of light. Even if it changes, it hardly changes, and
The retardation plates 23 and 24 are both the slow axis 23
a, the refractive indices n _x in the x axis direction is 24a, and the refractive index n _z in the refractive index n _y and z-axis direction of the y-axis direction, n _x> n
_{Since the} biaxial retardation plate has a relationship of _z > _ny, the phase difference between when the light vertically passes through the liquid crystal layer 18 of the liquid crystal cell 10 and when the light obliquely passes through the biaxial retardation plate. Plate 23,
Since it is compensated by 24, the viewing angle becomes wide.

The width of this viewing angle is as described in the first embodiment. If a normal uniaxial retardation plate is used as the retardation plate 23, the display color changes to some extent depending on the viewing angle. However, since the biaxial retardation plate has a small change in the phase difference with respect to the incident angle of light, if this biaxial retardation plate is used, the change in the display color depending on the viewing angle, that is, the viewing angle dependence of the display color. It gets quite small.

Further, in this color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes with temperature, but the birefringence of the phase difference plates 23 and 24 with temperature is extremely small. The liquid crystal layer 18 of the liquid crystal cell 10
The total birefringence of the phase difference plates 23 and 24 is a characteristic that temperature dependence is small.

In this embodiment, since the two biaxial retardation plates 23 and 24 are used, the above-mentioned first to third embodiments in which one biaxial retardation plate is used. Than the example
The phase difference between when light vertically passes through the liquid crystal layer 18 of the liquid crystal cell 10 and when it obliquely passes is more effectively compensated by the two biaxial retardation plates 23 and 24. Is further widened, and since the birefringence of the liquid crystal layer of the liquid crystal cell and the two retardation plates has a characteristic that the temperature dependence is smaller, the color change of the display color due to the temperature is also smaller. can do.

In the above embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 240 ° ± 20 ° (preferably 2).
40 ° ± 10 °), but this twist angle is 180
It may be in the range of ° to 270 °.

Further, the color liquid crystal display device of the above-mentioned embodiment is of a reflection type in which the reflection plate 25 is provided on the back surface, but this liquid crystal display device is used as a transmission type device without the reflection plate 25. It is also possible to do so.

[Seventh Embodiment] In the sixth embodiment, the value of Δn · d of the liquid crystal cell 10 is set to 1490 nm-1.
The value of Δn · d of this liquid crystal molecule is 590 nm.
It may be further increased to 1520 nm or more.

FIG. 16 shows the seventh embodiment of the present invention.
Liquid crystal molecule orientation direction of the liquid crystal cell 10 and the polarizing plates 21 and 22
FIG. 6 is a view showing the direction of the transmission axis of and the direction of the slow axis of the phase difference plates 23 and 24 as viewed from the surface side.

In the color liquid crystal display device of this embodiment, the value of Δn · d of the liquid crystal cell 10 is increased to 1520 nm or more, but the basic structure of the entire display device is shown in FIG. Since it is the same as the above, its explanation is omitted.

In this embodiment, as shown in FIG. 16, the alignment direction 12a of liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is counterclockwise when viewed from the front side with respect to the horizontal axis S of the liquid crystal cell 10. The direction of 35 ° ± 10 °, the alignment direction 11a of the liquid crystal molecules near the front substrate 11, and the alignment direction 12a of the liquid crystal molecules near the back substrate 12,
The direction of rotation is 70 ° ± 10 ° clockwise when viewed from the front side, and the liquid crystal molecules are rotated from the back substrate 12 side toward the front substrate 11 side in a clockwise direction when viewed from the front side 250 ° ± 20 ° (desirably 250 °). Twist orientation is performed at a twist angle of ± 10 °.

Further, in this embodiment, the transmission axis 21a of the front side polarizing plate 21 and the transmission axis 22a of the back side polarizing plate 22 are oriented as follows, and the two retardation plates 23
Of the first retardation film 23 adjacent to the front polarizing plate 21
Of the slow axis 23a of the front side polarizing plate 21 of the transmission axis 21a
And the slow axis 24a of the second retardation plate 24 adjacent to the liquid crystal cell 10 is oriented obliquely by a predetermined angle with respect to the following.

That is, the transmission axis 21a of the front polarizing plate 21.
When the alignment direction 12a of the liquid crystal molecules near the back substrate 12 of the liquid crystal cell 10 is the reference direction (direction of 0 °), the liquid crystal cell 1 is viewed from the front side with respect to the reference direction.
50 ° in the opposite direction (counterclockwise) to the twist direction of 0 liquid crystal molecules
The transmission axis 22a of the back side polarizing plate 22 is in the direction of ± 10 °.
Is 45 ° ± 10 ° in the same direction (clockwise) as the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction.

Also, the slow axis 23a of the first retardation plate 23
Is in the direction of 25 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction as viewed from the surface side with respect to the reference direction, and the slow axis 23a of the retardation plate 23 is the front side polarizing plate 2
The transmission axis 21a of No. 1 is displaced by 75 ° ± 20 ° in the direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side.

Further, the slow axis 24 of the second retardation plate 24
a is in the direction of 15 ° ± 10 ° in the opposite direction to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction. The deviation angle between the slow axis 24a of the second retardation plate 24 and the slow axis 23a of the first retardation plate 23 is 40 ° ±.
It is 20 °.

In this embodiment, the liquid crystal cell 1 described above is used.
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d is 1530 nm or more, for example, 1530n.
m-1730 nm) is used.

In this embodiment, the first biaxial retardation plate 23 has a retardation value of 1600n.
m ± 30 nm (1570 nm to 1630 nm) is used, and the second biaxial retardation plate 24 has a retardation value of 1550 nm ± 30 nm (1520 nm to 1520 nm).
80 nm) is used.

The color liquid crystal display device of this embodiment displays external light incident from the front surface side by reflecting it on the rear surface side reflection plate 25, and displays both substrates 11 and 12 of the liquid crystal cell 10.
A display is driven by applying a voltage between the electrodes 13 and 14 of the.

In this color liquid crystal display device, the linearly polarized light that has passed through the front-side polarizing plate 21 from the front side thereof and is incident thereon has the first retardation plate 23 and the second retardation plate 24.
And the liquid crystal cell 10 are sequentially transmitted, the phase difference plate 2
3, 24 birefringence effect and liquid crystal layer 18 of liquid crystal cell 10
Polarizing state can be changed by the birefringence effect of
The light that has entered 2 and transmitted through this back-side polarizing plate 22 becomes colored light.

Explaining the coloring of this light, the external light entering the liquid crystal display device first enters the first retardation plate 23 after passing through the front polarizing plate 21 to become linearly polarized light. Since the retardation plate 23 and the slow axis 23a are obliquely displaced from the transmission axis 21a of the front side polarizing plate 21 by a predetermined angle (75 ° ± 20 ° in this embodiment), the front side polarizing plate 2
The linearly polarized light having passed through 1 is subjected to a birefringence action according to the value of its retardation while passing through the first retardation plate 23, and each wavelength light becomes elliptically polarized light having a different polarization state.

The light transmitted through the first retardation plate 23 is incident on the second retardation plate 24 and is subjected to the birefringence action according to the retardation value thereof, so that the elliptically polarized light of each wavelength light is obtained. The state of becomes a light that has changed further.

Further, the light transmitted through the second retardation plate 24 enters the liquid crystal cell 10 and while passing through the liquid crystal layer 18, the value of Δn · d and the liquid crystal molecules of the liquid crystal cell 10 are changed. By the birefringence action depending on the orientation state, the light having the elliptically polarized state of each wavelength light is further changed.

In this case, in this embodiment, the liquid crystal cell 10
Since the twist angle of the liquid crystal molecules is 250 ° ± 20 °, the birefringence action of the liquid crystal layer 18 of the liquid crystal cell 10 is larger than that of the first embodiment described above.

As described above, the first retardation film 23
Due to the birefringence effect of the above, the birefringence effect of the second retardation plate 24, and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, the light whose wavelengths have become elliptically polarized lights having different polarization states is the back side polarization plate. The light enters the backside polarizing plate 22 of
Of the component along the transmission axis 22a of the light is transmitted through the back side polarizing plate 22, and the transmitted light (linearly polarized light) is a colored light of a color corresponding to the light quantity ratio of each wavelength light constituting the transmitted light. become.

The color of this colored light depends on the pair of polarizing plates 21 and 2.
Two transmission axes 21a, 22a and two retardation plates 23,
The orientations of the slow axes 23a and 24a of 24 and the alignment direction 1 of the liquid crystal molecules in the vicinity of both substrates 11 and 12 of the liquid crystal cell 10.
1a and 12a, the value of Δn · d of the liquid crystal cell 10, and the first
The retardation value of the retardation plate 23 and the retardation value of the second retardation plate 24 are set so that the light amount ratio of each wavelength light component of the light transmitted through the back side polarizing plate 22 corresponds to the desired colored light. It can be arbitrarily selected by setting the ratio.

Further, the colored light transmitted through the back side polarizing plate 22 is reflected by the reflection plate 25 and is emitted to the upper surface side of the liquid crystal display device through a route opposite to the above-mentioned optical path, and a colored image is displayed by this colored light. To be done.

The colored light reflected by the reflecting plate 25 is elliptically polarized light whose wavelengths are different due to the birefringence effect of the phase difference plates 23 and 24 and the liquid crystal layer 18 of the liquid crystal cell 10. The transmission axis 2 of the back side polarizing plate 22
The light having only the component along 2a and the light having a very small wavelength component at the end of the wavelength range is transmitted through the liquid crystal cell 10, the second retardation plate 24, and the first retardation plate 23 again. Since the birefringent light is absorbed by the front-side polarizing plate 21 in the process of being processed, the colored light that passes through the front-side polarizing plate 21 and is emitted has a higher color purity than the colored light reflected by the reflecting plate 25. Becomes

That is, in this color liquid crystal display device, the birefringence effect of the two retardation plates 23 and 24, the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10 and the pair of polarized lights are used without using a color filter. The light is colored by utilizing the polarization effect of the plates 21 and 22, and therefore the light is not absorbed by the color filter, so that the light transmittance can be increased. Therefore, even if the color liquid crystal display device is of a reflective type, a very bright color display can be obtained.

In this color liquid crystal display device, the birefringence of the retardation plates 23 and 24 is determined by the retardation value of the retardation plates 23 and 24.
The birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 depends on the substrate 1
1, 12 changes depending on the change in the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes 13 and 14, and accordingly the polarization state of each wavelength light incident on the back side polarizing plate 22 changes. The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell 10, and therefore, a plurality of colors can be displayed at the same location, that is, the same pixel.

The display colors of the color liquid crystal display device are as follows: the transmission axes 21a and 22a of the pair of polarizing plates 21 and 22 and the directions of the slow axes 23a and 24a of the two retardation plates 23 and 24, and the liquid crystal cell 10. The alignment directions 11a and 12a of the liquid crystal molecules in the vicinity of both substrates 11 and 12, and Δ of the liquid crystal cell 10.
It depends on the value of n · d and the retardation values of the retardation films 23 and 24 and the value of the voltage applied to the liquid crystal cell 10. In the color liquid crystal display device of this embodiment, the value of Δn · d of the liquid crystal cell is Since it is as large as 1530 nm to 1730 nm, the change in birefringence with respect to the applied voltage of the liquid crystal layer 18 is large, so that the number of display colors can be increased.

The display color of this color liquid crystal display device will be described. As shown in FIG. 16, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 °, and the front side polarizing plate 2
No. 1 adjacent to the transmission axis 21a and the front side polarizing plate 21
Of the phase difference plate 23 with respect to the slow axis 23a is 75 ° ± 2
When the angle is 0 ° and the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is the reference direction,
The transmission axis 21a of the front polarizing plate 21 is 50 ° ± 10 ° in the direction opposite to the liquid crystal molecule twist direction of the liquid crystal cell 10 when viewed from the front side with respect to the reference direction, and the transmission axis 2 of the back polarizing plate 22.
2a is a direction of 45 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction when viewed from the front side with respect to the reference direction, and the slow axis 23a of the first retardation plate 23 is the front side with respect to the reference direction. When viewed from the above, the liquid crystal molecule is twisted in the same direction as the 2
Second direction adjacent to the liquid crystal cell 10 in the direction of 5 ° ± 10 °
The retardation axis 24a of the retardation plate 24 is 15 in the direction opposite to the liquid crystal molecule twist direction when viewed from the surface side with respect to the reference direction.
The value of Δn · d of the liquid crystal cell 10 is 1530 nm to 1730 nm, the retardation value of the first retardation plate 23 is 1600 nm ± 30 nm, and the retardation value of the second retardation plate 24 is in the direction of ± 10 °. Is 1550 nm ± 3
When the thickness is 0 nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value, and the display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied voltage) (Display color) 1.80 v or less Black 1.81 to 2.10 v White 2.11 to 2.20 v Red 2.21 to 2.40 v Blue 2.41 v or more Green As described above, The display color of the color liquid crystal display device changes in the order of black → white → red → green → blue as the voltage applied to the liquid crystal cell 10 is increased. Therefore, one pixel has three primary colors of light. It is possible to display certain reds, greens and blues and whites and blacks, thus allowing the display of full color images.

Moreover, in the above color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the incident angle of light, but the birefringence of the phase difference plates 23 and 24 depends on the incident angle of light. Even if it changes, it hardly changes, and
The retardation plates 23 and 24 are both the slow axis 23
a, the refractive indices n _x in the x axis direction is 24a, and the refractive index n _z in the refractive index n _y and z-axis direction of the y-axis direction, n _x> n
_{Since the} biaxial retardation plate has a relationship of _z > _ny, the phase difference between when the light vertically passes through the liquid crystal layer 18 of the liquid crystal cell 10 and when the light obliquely passes through the biaxial retardation plate. Plate 23,
Since it is compensated by 24, the viewing angle becomes wide.

The width of this viewing angle is as described in the first embodiment. When a normal uniaxial retardation plate is used as the retardation plate 23, the display color changes to some extent depending on the viewing angle. However, since the biaxial retardation plate has a small change in the phase difference with respect to the incident angle of light, if this biaxial retardation plate is used, the change in the display color depending on the viewing angle, that is, the viewing angle dependence of the display color. It gets quite small.

Further, in this color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the temperature, but the birefringence of the phase difference plates 23 and 24 changes little with temperature. The liquid crystal layer 18 of the liquid crystal cell 10
The total birefringence of the phase difference plates 23 and 24 is a characteristic that temperature dependence is small.

In this embodiment, since the two biaxial retardation plates 23 and 24 are used, the above-mentioned first to third embodiments in which one biaxial retardation plate is used. Than the example
The phase difference between when light vertically passes through the liquid crystal layer 18 of the liquid crystal cell 10 and when it obliquely passes is more effectively compensated by the two biaxial retardation plates 23 and 24. Is further widened, and since the birefringence of the liquid crystal layer of the liquid crystal cell and the two retardation plates has a characteristic that the temperature dependence is smaller, the color change of the display color due to the temperature is also smaller. can do.

In the above embodiment, the pair of polarizing plates 2
Although the transmission axes 21a and 22a of 1 and 22 and the slow axis 23a of the phase plate 23 are set as shown in FIG. 16, these axial directions may be set as follows, for example.

FIG. 17 shows the transmission axes 21a of the polarizing plates 21 and 22 in the color liquid crystal display device of the seventh embodiment.
22a is a diagram showing another setting example of the orientations of the slow axis 23a of the phase difference plate 23a and 22a as viewed from the front surface side.

In this example, both substrates 11 of the liquid crystal cell 10,
Alignment directions 11a and 12a of liquid crystal molecules near 12
And the twist angle and the twist direction of the liquid crystal molecules, the direction of the transmission axis 21a of the front side polarizing plate 21, and the first retardation plate 23.
Slow axis 23a and the slow axis 24 of the second retardation plate 24
The orientation of a is the same as that of the embodiment shown in FIG. 16, and the orientation of the transmission axis 21a of the back side polarizing plate 22 is set to the reference direction (the liquid crystal cell 1).
Alignment direction 1 of liquid crystal molecules near the back substrate 12
With respect to 2a), the direction is 45 ° ± 10 ° in the opposite direction (counterclockwise) to the twist direction of the liquid crystal molecules of the liquid crystal cell 10.

The value of Δn · d of the liquid crystal cell 10 is 1530 nm to 1730 nm, and the first biaxial retardation plate 2 is used.
3 has a retardation value of 1600 nm ± 30 nm, and the second biaxial retardation plate 24 has a retardation value of 155.
It is 0 nm ± 30 nm.

In this way, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 °, and the shift angle between the transmission axis 21a of the front polarizing plate 21 and the slow axis 23a of the retardation plate 23 is 75.
When the alignment direction 12a of the liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is used as a reference direction, the transmission axis 21a of the front polarizing plate 21 is viewed from the front side with respect to the reference direction. A direction of 50 ° ± 10 ° in a direction opposite to the liquid crystal molecule twist direction of the liquid crystal cell 10, and a transmission axis 22a of the back polarizing plate 22 is 45 ° in a direction opposite to the liquid crystal molecule twist direction when viewed from the front side with respect to the reference direction. ± 10 ° direction,
The slow axis 23a of the first retardation plate 23 adjacent to the front-side polarizing plate 21 is 25 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction when viewed from the front side with respect to the reference direction, and the back-side polarizing plate The slow axis 24 of the second retardation plate 24 adjacent to 22
a is 15 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction with respect to the reference direction from the surface side, and the value of Δn · d of the liquid crystal cell 10 is 1530 nm to 1730 n.
m, the retardation value of the first retardation plate 23 is 160
When the retardation value of the second biaxial retardation film 24 is 0 nm ± 30 nm and the retardation value is 1550 nm ± 30 nm, the relationship between the applied voltage to the liquid crystal cell 10 and the display color is as follows. Here, the applied voltage value is an effective value, and the display color is a color when the display of the liquid crystal display device is viewed from the front.

(Applied voltage) (Display color) 1.90v or less White 1.91 to 2.10v Black 2.11 to 2.20v Blue 2.21 to 2.30v Green 2.31v or more Red That is, in this example , The display color increases as the voltage applied to the liquid crystal cell 10 increases, white → black → blue →
Since it changes from green to red, one pixel can display the three primary colors of light, red, green, and blue, and white and black.
Therefore, a full-color image can be displayed.

In the above embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 ° (desirably 2).
50 ° ± 10 °), but this twist angle is 180
It may be in the range of ° to 270 °.

Further, the color liquid crystal display device of the above-mentioned embodiment is of a reflection type in which the reflection plate 25 is provided on the back surface thereof, but this liquid crystal display device is used as a transmission type device without the reflection plate 25. It is also possible to do so.

[Eighth Embodiment] Next, an eighth embodiment of the present invention will be described with reference to FIGS. 18 and 19. The color liquid crystal display device of this embodiment is used as a reflection type display device and is provided with a liquid crystal cell, a polarizing plate, a biaxial retardation plate and a reflecting plate, and the number of the polarizing plates is one. It is the one.

FIG. 18 is a cross-sectional view of a color liquid crystal display device. This liquid crystal display device includes a liquid crystal cell 10 and one polarizing plate 21 arranged on the surface side (upper surface side in the figure) of the liquid crystal cell 10. And a single retardation plate 23 arranged between the polarizing plate 21 and the liquid crystal cell 10, and a reflection plate 25 arranged on the back side of the liquid crystal cell 10.

The liquid crystal cell 10 has, for example, a twist angle of liquid crystal molecules of 80 ° to 110 °, and in this embodiment, the twist angle of the liquid crystal molecules is approximately 90 °. Since the basic configuration of the liquid crystal cell 10 is the same as that of the liquid crystal cell in the first embodiment described above, the duplicated description will be omitted by giving the same reference numerals to the drawings.

In the retardation plate 23, the refractive index n _x in the x-axis direction, which is the slow axis, the refractive index n _{y in the y-} axis direction, and the refractive index n _{z in the} z-axis direction are n _x. It is a biaxial phase plate having a relationship of> n _z > n _y .

FIG. 19 is a view showing the alignment direction of liquid crystal molecules of the liquid crystal cell 10, the direction of the transmission axis of the polarizing plate 21, and the direction of the slow axis of the retardation plate 23 as viewed from the front side.

As shown in FIG. 19, the alignment direction 12a of liquid crystal molecules in the vicinity of the back substrate 12 of the liquid crystal cell 10 is
With respect to the horizontal axis S of the liquid crystal cell 10, a direction of about 45 ° clockwise when viewed from the front side, and an alignment direction 11a of liquid crystal molecules near the front substrate 11 is an alignment direction of liquid crystal molecules near the back substrate 12. 12a is in a direction of approximately 90 ° counterclockwise when viewed from the surface side, and the liquid crystal molecules are directed from the back substrate 12 side to the front substrate 11 side, and the twist angle is approximately 90 ° clockwise when viewed from the surface side. It has a twist orientation.

The transmission axis 21a of the polarizing plate 21 is
The liquid crystal cell 10 is substantially orthogonal to the alignment direction 11a of liquid crystal molecules in the vicinity of the front substrate 11, and the retardation plate 2
The slow axis 23a of No. 3 is slanted by a predetermined angle with respect to the transmission axis 21a of the polarizing plate 21. In this embodiment, the slow axis 23a of the retardation plate 23 is opposite to the liquid crystal molecule twist direction of the liquid crystal cell 10 (counterclockwise) with respect to the transmission axis 21a of the front polarizing plate 21 when viewed from the surface side. Almost 45 °
They are staggering.

In the color liquid crystal display device of this embodiment, the external light incident from the front surface side is reflected by the reflection plate 25 on the rear surface side for display, and both substrates 11, 12 of the liquid crystal cell 10 are displayed.
A display is driven by applying a voltage between the electrodes 13 and 14 of the.

In this color liquid crystal display device, the linearly polarized light which is transmitted through the front side polarizing plate 21 from the front side thereof and is incident thereon is sequentially transmitted through the retardation plate 23 and the liquid crystal cell 10, and is further reflected by the reflection plate 25. The liquid crystal cell 10 is reflected.
And the phase difference plate 23, the phase difference plate 2
The polarization state is changed by the birefringence effect of No. 3 and the birefringence effect of the liquid crystal layer 18 of the liquid crystal cell 10, enters the polarizing plate 21, and the light transmitted through the polarizing plate 21 becomes colored light.

Explaining the coloring of this light, the external light entering the liquid crystal display device enters the retardation film 23 after passing through the polarizing plate 21 to become linearly polarized light. The phase axis 23a is the transmission axis 21a of the polarizing plate 21.
With respect to the predetermined angle (in this embodiment, approximately 45 °), the linearly polarized light transmitted through the polarizing plate 21 is birefringent according to its retardation value while being transmitted through the retardation plate 23. Accordingly, the light of each wavelength becomes elliptically polarized light having a different polarization state, and while the light is transmitted through the liquid crystal layer 18 incident on the liquid crystal cell 10, Δn of the liquid crystal cell 10 is increased.
The light having the elliptically polarized light of each wavelength is further changed by being subjected to the birefringence action depending on the value of d and the alignment state of the liquid crystal molecules.

The light transmitted through the liquid crystal cell 10 is reflected by the reflection plate 25, and while passing through the liquid crystal layer 18 and the retardation film 23 of the liquid crystal cell 10 again, each wavelength is further increased by their birefringence action. The light whose elliptically polarized state has changed is incident on the polarizing plate 21, and only the component light along the transmission axis 22a of the rear polarizing plate 22 is transmitted through this polarizing plate 22. Then, the transmitted light (linearly polarized light) becomes colored light having a color corresponding to the light amount ratio of the wavelength light components of the transmitted light.

The color of this colored light depends on the transmission axis 2 of the polarizing plate 21.
1a and the direction of the slow axis 23a of the retardation plate 23, the alignment directions 11a and 12a of the liquid crystal molecules near the substrates 11 and 12 of the liquid crystal cell 10, the value of Δn · d of the liquid crystal cell 10, and the phase difference. The value of the retardation of the plate 23 can be arbitrarily selected by setting it so that the light amount ratio of each wavelength light constituting the light transmitted through the polarizing plate 21 becomes a ratio corresponding to a desired colored light.

That is, this color liquid crystal display device uses the birefringence effect of the retardation film, the birefringence effect of the liquid crystal layer of the liquid crystal cell, and the polarization effect of the polarizing plate without using a color filter. Therefore, since the color filter does not absorb light, it is possible to obtain a bright color display by increasing the light transmittance even in the reflective type.

Also in this color liquid crystal display device, the birefringence of the liquid crystal layer of the liquid crystal cell is changed by the change of the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes of both substrates. The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell, and therefore, a plurality of colors can be displayed at the same place.

Also in this color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes depending on the incident angle of light, but the birefringence of the retardation plate 23 changes the incident angle of light. However, the retardation plate 23 has a refractive index n _x in the x-axis direction, which is the slow axis,
the y-axis direction of the refractive index n _y and z refractive index of the axis n _z is, n _x> n _z> for a biaxial retardation film having a relationship of n _y, the liquid crystal layer of the light the liquid crystal cell 10 The biaxial retardation plate 23 compensates for the phase difference between when the light is transmitted vertically through 18 and when it is transmitted obliquely, so that the viewing angle is widened.

Further, also in this color liquid crystal display device, the birefringence of the liquid crystal layer 18 of the liquid crystal cell 10 changes with temperature, but the change of the birefringence with temperature of the retardation plate 23 is extremely small, and therefore, the liquid crystal. The birefringence of the entire liquid crystal layer 18 of the cell 10 and the retardation film 23 has a characteristic that temperature dependence is small, and therefore the color change of the display color due to temperature is also small.

Further, in the color liquid crystal display device of this embodiment, one polarizing plate 21 is arranged only on the front surface side of the liquid crystal cell 10, and this polarizing plate 21 linearly polarizes light incident on the liquid crystal display device. Since it also serves as a polarizer for obtaining a colored light by transmitting only a certain component of the elliptically polarized light transmitted through the phase difference plate 23 and the liquid crystal cell 10, The price of the liquid crystal display device can be reduced as compared with the case where the polarizing plates are respectively arranged on the front surface side and the rear surface side of the liquid crystal cell.

Although the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 80 ° to 110 ° (approximately 90 ° in FIG. 19) in the above embodiment, the twist angle of the liquid crystal molecules is 1 °.
It may be 80 ° to 270 ° or 110 ° to 130 °.

In the above embodiment, one biaxial retardation plate 23 is used, but the biaxial retardation plate may be two. In that case, the polarizing plate 21 and the liquid crystal cell are used. 10 and between the liquid crystal cell 10 and the reflection plate 25, one retardation plate is provided, and two retardation plates are provided between the polarizing plate 21 and the liquid crystal cell 10. You may arrange | position on top of each other.

In the above-mentioned first to eighth embodiments,
As the liquid crystal cell 10, a simple matrix type is used, but the liquid crystal cell 10 may be an active matrix type in which a two-terminal nonlinear resistance element such as a TFT (thin film transistor) or MIM is used as an active element. Alternatively, it may be of a segment display type which is driven in a time division manner.

[0320]

The color liquid crystal display device of the present invention includes a liquid crystal cell in which a nematic liquid crystal layer in which liquid crystal molecules are twist-aligned is provided between a pair of substrates having electrodes formed on the inner surface, and the liquid crystal cell is sandwiched therebetween. A pair of polarizing plates disposed on the front surface side and the back surface side of the polarizing plate, and a retardation plate disposed between the pair of polarizing plates, wherein the retardation plate is the slow axis in the x-axis direction. the refractive indices n _x a, the refractive index in the y-axis direction n _y
And a refractive index n _{z in the} z-axis direction are in a relationship of n _x > n _z > n _y , wherein the transmission axes of the pair of polarizing plates and the slow phase of the retardation plate are The direction of the axis and the alignment direction of the liquid crystal molecules in the vicinity of the substrate of the liquid crystal cell are such that the light incident through the one polarizing plate has a birefringence effect of the retardation plate and a birefringence effect of the liquid crystal layer of the liquid crystal cell. By so that each wavelength light becomes elliptically polarized light having a different polarization state, and the light amount ratio of each wavelength light of the light transmitted through the other polarizing plate of the light becomes a ratio corresponding to the desired colored light. Since it is characterized by being set, it is possible to obtain a bright color display without using a color filter, display multiple colors at the same location, and widen the viewing angle and further improve the temperature. The change in display color due to You.

When one biaxial retardation plate is used in the reflection type liquid crystal display device, this retardation plate is arranged between the front side polarizing plate and the liquid crystal cell, and at least the front side polarizing plate is used. If the transmission axis of and the slow axis of the retardation plate are slanted by a predetermined angle, linearly polarized light that has passed through the front side polarizing plate and enters will be polarized by the birefringence effect in the process of passing through the retardation plate. Since the light is changed in state and the light is further changed in polarization state by the birefringence effect of the liquid crystal layer in the process of passing through the liquid crystal cell and is incident on the back side polarizing plate, the above-mentioned colored light can be obtained.

In the case of using two biaxial retardation plates in the reflection type liquid crystal display device, 1 is provided between the front side polarizing plate and the liquid crystal cell and between the back side polarizing plate and the liquid crystal cell. By arranging retardation plates one by one, and at least shifting the transmission axis of the front side polarizing plate and the slow axis of the retardation plate adjacent to this polarizing plate by a predetermined angle, the light is transmitted through the front side polarizing plate and incident. The linearly polarized light is changed in polarization state by the birefringence effect in the process of passing through the retardation plate adjacent to the front side polarizing plate, and further polarized by the birefringence effect in the liquid crystal layer in the process in which the light passes through the liquid crystal cell. It is possible to obtain the above-mentioned colored light because the polarization state is changed by the birefringence effect and is incident on the back side polarizing plate in the process of changing the state and further transmitting the light through the retardation plate adjacent to the back side polarizing plate. it can.

When two biaxial retardation plates are used in the reflective liquid crystal display device, the two biaxial retardation plates are placed between the front side polarizing plate and the liquid crystal cell so as to overlap each other. ,
If at least the transmission axis of the front-side polarizing plate and the slow axis of the retardation plate of the two retardation plates adjacent to the front-side polarizing plate are offset by a predetermined angle, the front-side polarizing plate is transmitted. The incident linearly polarized light is changed in polarization state by the birefringence effect in the process of passing through the retardation plate adjacent to the front side polarizing plate, and the polarized light is changed in the process of passing through the retardation plate adjacent to the liquid crystal cell. The polarization state can be further changed by the refraction effect, and the polarization state can be changed by the birefringence effect of the liquid crystal layer in the process of transmitting the light through the liquid crystal cell to be incident on the back side polarizing plate. it can.

In the liquid crystal display device using the above-mentioned two biaxial retardation plates, the phase difference between when light is vertically transmitted through the liquid crystal layer of the liquid crystal cell and when it is obliquely transmitted is two biaxial retardation plates. Since it is more effectively compensated by the retardation film, the viewing angle is further widened, and the birefringence of the liquid crystal layer of the liquid crystal cell and the two retardation plates is further dependent on the temperature. Since the characteristic becomes small, the color change of the display color due to the temperature becomes smaller.

Furthermore, 2 is provided between the front side polarizing plate and the liquid crystal cell.
In a reflection-type liquid crystal display device in which two biaxial retardation plates are arranged on top of each other, when the twist angle of the liquid crystal molecules of the liquid crystal cell is 180 ° to 270 °, Δn.
If the value of d is increased to 1490 nm or more, the change in birefringence with respect to the applied voltage of the liquid crystal layer becomes large.
The number of display colors can be increased.

Another color liquid crystal display device of the present invention is a liquid crystal cell having a nematic liquid crystal layer in which liquid crystal molecules are twist-aligned between a pair of substrates having electrodes formed on the inner surface thereof, and the surface of the liquid crystal cell. One polarizing plate disposed only on the side, a reflection plate disposed on the back surface side of the liquid crystal cell, and a retardation plate disposed between the polarization plate and the reflection plate, and The retardation plate has a refractive index n _x in the x-axis direction, which is the slow axis, and a refractive index n _{y in the y-} axis direction and a refractive index n _{z in the} z-axis direction, where n _x > n _z > n _y In a biaxial retardation plate having a relationship, the transmission axis of the polarizing plate and the direction of the slow axis of the retardation plate, and the alignment direction of liquid crystal molecules in the vicinity of the substrate of the liquid crystal cell, the polarizing plate The light that passes through and enters the polarizing plate after being reflected by the reflecting plate is birefringent in the retardation plate. Due to the result and the birefringence effect of the liquid crystal layer of the liquid crystal cell, each wavelength light becomes an elliptically polarized light having a different polarization state, and the light amount ratio of each wavelength light of the light transmitted through the polarizing plate is desired. Since the ratio is set to correspond to the colored light of, it is possible to obtain a bright color display without using a color filter and display multiple colors at the same location. Moreover, it is possible to widen the viewing angle and reduce the color change of the display color due to the temperature.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a color liquid crystal display device showing a first embodiment of the present invention.

FIG. 2 is a diagram showing the alignment direction of liquid crystal molecules of the liquid crystal cell, the direction of the transmission axis of the polarizing plate, and the direction of the slow axis of the retardation plate as seen from the surface side in the first embodiment.

FIG. 3 is a perspective view of a biaxial retardation plate.

FIG. 4 is a phase difference R _xy (0) when the light incident angle is 0 ° and a phase difference R when the light incident angle is θ ° in the biaxial retardation plate.
_The figure which shows the change by the light incident angle of ratio _Rxy ((theta)) / _Rxy (0) with _xy ((theta)) compared with a normal uniaxial phase difference plate.

FIG. 5 is a view angle and display color difference between the color liquid crystal display device of the first embodiment and a comparison device in which the retardation plate is replaced with a normal uniaxial retardation plate of n _x > n _y = n _z ( The figure which shows the relationship with (DELTA) E ^* ab).

FIG. 6 shows a second embodiment of the present invention, which is viewed from the surface side showing the liquid crystal molecule alignment direction of the liquid crystal cell, the transmission axis direction of the polarizing plate, and the slow axis direction of the retardation plate. Fig.

FIG. 7 shows a third embodiment of the present invention, as viewed from the surface side showing the liquid crystal molecule alignment direction of the liquid crystal cell, the transmission axis direction of the polarizing plate, and the slow axis direction of the retardation plate. Fig.

FIG. 8 is a diagram showing another example of setting the directions of the transmission axis of the polarizing plate and the slow axis of the retardation plate as seen from the surface side in the third embodiment.

FIG. 9 is a sectional view of a color liquid crystal display device showing a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a liquid crystal molecule alignment direction of a liquid crystal cell, a transmission axis direction of a polarizing plate, and a slow axis direction of a retardation plate as seen from the front surface side in a fourth example.

FIG. 11 is a sectional view of a color liquid crystal display device showing a fifth embodiment of the present invention.

FIG. 12 is a diagram showing the alignment direction of liquid crystal molecules of a liquid crystal cell, the orientation of a transmission axis of a polarizing plate, and the orientation of a slow axis of a retardation plate as seen from the surface side in a fifth embodiment.

FIG. 13 shows a sixth embodiment of the present invention, which is viewed from the surface side showing the liquid crystal molecule alignment direction of the liquid crystal cell, the transmission axis direction of the polarizing plate, and the slow axis direction of the retardation plate. Fig.

FIG. 14 is a CIE chromaticity diagram showing a change in display color of the color liquid crystal display device of the sixth embodiment.

FIG. 15 is a diagram showing a relationship between a voltage applied to a liquid crystal cell in a color liquid crystal display device of a sixth embodiment, an emission rate of light in wavelength ranges of red, green, and blue, and a display color.

FIG. 16 shows a seventh embodiment of the present invention, as viewed from the surface side showing the liquid crystal molecule alignment direction of the liquid crystal cell, the transmission axis direction of the polarizing plate, and the slow axis direction of the retardation plate. Fig.

FIG. 17 is a diagram showing another example of setting the directions of the transmission axis of the polarizing plate and the slow axis of the retardation plate as seen from the front surface side in the seventh embodiment.

FIG. 18 is a sectional view of a color liquid crystal display device showing an eighth embodiment of the present invention.

FIG. 19 is a view showing the alignment direction of liquid crystal molecules of a liquid crystal cell, the direction of the transmission axis of a polarizing plate, and the direction of the slow axis of a retardation plate as seen from the surface side in the eighth example.

[Explanation of symbols]

 10 ... Liquid crystal cell 11, 12 ... Substrate 11a ... Liquid crystal molecule alignment direction in the vicinity of front side substrate 12a ... Liquid crystal molecule alignment direction in the vicinity of back side substrate 13, 14 ... Electrode 15, 16 ... Alignment film 18 ... Liquid crystal layers 21, 22 ... Polarizing plates 21a, 22a ... Transmission axis 23, 24 ... Biaxial retardation plate 23a, 24a ... Slow axis 25 ... Reflector

Claims (16)

[Claims] 1. A liquid crystal cell comprising a nematic liquid crystal layer in which liquid crystal molecules are twist-aligned between a pair of substrates having electrodes formed on the inner surface thereof, and arranged on the front surface side and the back surface side with the liquid crystal cell interposed therebetween. And a retardation plate disposed between the pair of polarizing plates, wherein the retardation plate has a refractive index n _x in the x-axis direction, which is the slow axis, and a y-axis. A biaxial retardation plate having a refractive index n _{y in the} direction and a refractive index n _{z in the} z-axis direction of n _x > n _z > n _y , wherein the transmission axis of the pair of polarizing plates and the The direction of the slow axis of the retardation plate and the alignment direction of the liquid crystal molecules in the vicinity of the substrate of the liquid crystal cell are such that the light incident through the one polarizing plate has the birefringence effect of the retardation plate and the liquid crystal cell Due to the birefringence effect of the liquid crystal layer, each wavelength light becomes elliptically polarized light with different polarization state, One, the color liquid crystal display device, characterized in that the other light amount ratio of each wavelength of light transmitted through the polarizing plate of the light is set to be the ratio corresponding to the desired colored light. 2. A reflection plate is arranged behind a back side polarizing plate arranged on the back side of the liquid crystal cell, and one sheet is provided between the front side polarizing plate arranged on the front side of the liquid crystal cell and the liquid crystal cell. 2. The biaxial retardation plate according to claim 1 is arranged, and at least the transmission axis of the front-side polarizing plate and the slow axis of the retardation plate are obliquely displaced by a predetermined angle. The color liquid crystal display device described in 1. 3. A reflection plate is arranged behind a back side polarizing plate arranged on the back side of the liquid crystal cell, between the front side polarizing plate arranged on the front side of the liquid crystal cell and the liquid crystal cell, and a liquid crystal. One biaxial retardation plate is disposed between each of the back side polarizing plate disposed on the back side of the cell and the liquid crystal cell, and at least the transmission axis of the front side polarizing plate and The color liquid crystal display device according to claim 1, wherein a retardation axis of a retardation plate adjacent to the plate is obliquely displaced by a predetermined angle. 4. A reflection plate is arranged behind a back side polarizing plate arranged on the back side of the liquid crystal cell, and a reflector is arranged between the front side polarizing plate arranged on the front side of the liquid crystal cell and the liquid crystal cell. The two biaxial retardation plates are arranged to overlap each other, and at least the transmission axis of the front side polarizing plate and the retardation of the retardation plate adjacent to the front side polarizing plate of the two retardation plates are delayed. The color liquid crystal display device according to claim 1, wherein the phase axis is obliquely displaced by a predetermined angle. 5. The twist angle of liquid crystal molecules of the liquid crystal cell is 80 °.
It is -110 degrees, It is characterized by the above-mentioned.
7. The color liquid crystal display device according to any one of 1. 6. The twist angle of the liquid crystal molecules of the liquid crystal cell is 110.
5. The color liquid crystal display device according to claim 1, wherein the color liquid crystal display device has an angle of .degree. 7. The twist angle of the liquid crystal molecules of the liquid crystal cell is 180.
5. The color liquid crystal display device according to claim 1, wherein the color liquid crystal display device is in the range of 0 ° to 270 °. 8. The twist angle of liquid crystal molecules of the liquid crystal cell is 80 °.
Is 110 °, and the value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the liquid crystal layer thickness d is 520 nm to 5
80 nm, retardation value of retardation plate is 400 nm
The color liquid crystal display device according to claim 2, wherein the color liquid crystal display device has a thickness of ˜460 nm. 9. The twist angle of the liquid crystal molecules of the liquid crystal cell is 110.
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the thickness d of the liquid crystal layer is 880 nm to 130 °.
970 nm, retardation value of retardation plate is 1270
The color liquid crystal display device according to claim 2, wherein the color liquid crystal display device has a wavelength of 15 nm to 1530 nm. 10. A twist angle of liquid crystal molecules of a liquid crystal cell is 18
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the liquid crystal layer thickness d is 850 nm.
~ 910 nm, retardation value of the retardation plate is 400
The color liquid crystal display device according to claim 2, wherein the color liquid crystal display device has a thickness of nm to 460 nm. 11. A twist angle of liquid crystal molecules of a liquid crystal cell is 18
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the liquid crystal layer thickness d is 1250n.
m to 1450 nm, the retardation value of the retardation plate adjacent to the front polarizing plate is 1570 nm to 1630 nm, and the retardation value of the retardation plate adjacent to the back polarizing plate is 15.
It is 70 nm-1630 nm, The color liquid crystal display device of Claim 3 characterized by the above-mentioned. 12. The twist angle of liquid crystal molecules of a liquid crystal cell is 18
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the liquid crystal layer thickness d is 1250n.
m to 1450 nm, the retardation value of the retardation plate adjacent to the front-side polarizing plate was 1570 nm to 1630 nm, and the retardation value of the retardation plate adjacent to the liquid crystal cell was 152.
It is 0 nm-1580 nm, It is characterized by the above-mentioned.
The color liquid crystal display device described in 1. 13. The twist angle of liquid crystal molecules of a liquid crystal cell is 18
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the liquid crystal layer thickness d is 1490n.
The color liquid crystal display device according to claim 4, wherein the color liquid crystal display device has a length of m or more. 14. A liquid crystal cell having a Δn · d value of 1490 nm.
˜1590 nm, the retardation value of the retardation plate adjacent to the front-side polarizing plate is 1570 nm to 1630 nm, and the retardation value of the retardation plate adjacent to the liquid crystal cell is 1420.
nm to 1480 nm.
The color liquid crystal display device described in 1. 15. The value of Δn · d of the liquid crystal cell is 1530.
nm to 1730 nm, the retardation value of the retardation plate adjacent to the front side polarizing plate is 1570 nm to 1630 nm, and the retardation value of the retardation plate adjacent to the liquid crystal cell is 15 nm.
20 nm-1580 nm, The color liquid crystal display device of Claim 13 characterized by the above-mentioned. 16. A liquid crystal cell comprising a nematic liquid crystal layer in which liquid crystal molecules are twist-aligned between a pair of substrates having electrodes formed on the inner surface thereof, and a single polarizing plate arranged only on the surface side of the liquid crystal cell. And a reflection plate arranged on the back surface side of the liquid crystal cell, and a retardation plate arranged between the polarizing plate and the reflection plate, and the retardation plate is its slow axis. the refractive indices n _x in the x-axis direction, and a refractive index n _z in the refractive index n _y and z-axis direction of the y-axis direction, there in the biaxial retardation film having a relationship of n _x> n _z> n _y The directions of the transmission axis of the polarizing plate and the slow axis of the retardation plate and the alignment direction of the liquid crystal molecules in the vicinity of the substrate of the liquid crystal cell are transmitted through the polarizing plate to enter and reflected by the reflecting plate. The light incident on the polarizing plate receives the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer of the liquid crystal cell. By setting, each wavelength light becomes elliptically polarized light with different polarization state, and the light quantity ratio of each wavelength light of the light transmitted through the polarizing plate is set to a ratio corresponding to the desired colored light. A color liquid crystal display device characterized by being provided.