JPH0990315A - Color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To embody a color display which is increased in transmittance, displays plural colors with one pixel, is high in contrast and has good color quality and high quality. SOLUTION: Two sheets of phase difference plates 22, 23 are arranged between a front side polarizing plate 20 and a liquid crystal cell 10. The retardation of the cell phase difference plate 23 of these plates is set at 2.5 to 3.5 times the retardation of the polarizing plate side phase difference plate 22. The twist angles and values of Δnd of the liquid crystal molecules of the liquid crystal cell 10, the values of the retardation the two phase difference plates 22, 23, the directions of the optical axes of the front and rear polarizing plates 20, 21 and the respective phase difference plates 22, 23 and the orientation directions of the liquid crystal molecules of the liquid crystal cell 10 near both substrates are so set that the linearly polarized light made incident by transmitting the one polarizing plate 20 is subjected to the double refraction effect while transmitting the phase difference plates 22, 23 and the liquid crystal layer of the liquid crystal cell 10 and that the light is transmitted through the other polarizing plate 21 and the ratios of the light intensity of the respective wavelength light rays attain desired ratios.

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

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 at a considerably high absorption rate. Therefore, the colored light that has passed through the color filter becomes light in which the light intensity is significantly reduced compared to the light in the wavelength band before entering the color filter, and the display becomes dark.

[0004] A liquid crystal display device is of a transmission type that displays by using light from a backlight, and an external light such as natural light or indoor illumination light is used to display the light on the back side of the liquid crystal display device. There is a reflection type in which light is reflected by a reflection plate arranged in a display, and a color liquid crystal display device that colors light using a color filter is a reflection type. The light reflected to the front side and emitted to the surface side passes through the color filter twice, and the light intensity is reduced twice, so that the display becomes extremely dark and can hardly be used as a display device.

Further, in a color liquid crystal display device that colors light using a color filter, the display color of each pixel is determined by the color of the color filter corresponding to that pixel. For example, a desired display color must be obtained by controlling the transmission of light of each pixel as a set of three pixels corresponding to three primary color filters of red, green, and blue, respectively. However, the number of pixels increases and the structure becomes complicated.

On the other hand, conventionally, as a color liquid crystal display device for obtaining a colored display without using a color filter, EC
A B-type (birefringence effect type) liquid crystal display device is known.
This ECB-type liquid crystal display device has a pair of polarizing plates disposed between a pair of substrates having electrodes formed on an inner surface thereof and a liquid crystal layer provided between the pair of substrates. The linearly polarized light transmitted through one polarizer is converted into elliptically polarized light having different polarization states due to the birefringence of the liquid crystal layer during the transmission through the liquid crystal cell. Light composed of light having a wavelength that is incident on the other polarizing plate and selectively transmitted through the other polarizing plate becomes colored light having a color corresponding to the light intensity ratio of each wavelength light that constitutes the light.

That is, the above ECB type liquid crystal display device
Without using a color filter, the 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 polarizers. Therefore, there is no light absorption by the color filter. Bright color display can be obtained by increasing the transmittance.

In addition, in the above-mentioned ECB type liquid crystal display device, the birefringence of the liquid crystal layer changes depending on the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes of both substrates of the liquid crystal cell. Since the polarization state of each wavelength light incident on the polarizing plate changes, the color of the colored light can be changed by controlling the voltage applied between the electrodes of the liquid crystal cell. Color can be displayed.

[0009]

However, the conventional ECB type liquid crystal display device has a problem that display contrast is low and color quality of display, that is, color quality such as color purity and brightness of each color is also inferior. I have.

According to the present invention, a bright color display can be obtained by increasing the light transmittance, and a plurality of colors can be displayed by one pixel. In addition, high contrast and good color quality can be obtained. It is an object of the present invention to provide a color liquid crystal display device capable of realizing color display.

[0011]

A color liquid crystal display device of the present invention comprises a liquid crystal cell having a 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 liquid crystal cell. A pair of polarizing plates arranged in a sandwiched manner, and two retardation plates arranged to overlap each other between any one of the polarizing plates and the liquid crystal cell are provided. The retardation of the retardation plate on the liquid crystal cell side is 2.5 times that of the retardation plate on the polarizing plate side.
˜3.5 times, the twist angle of the liquid crystal molecules of the liquid crystal cell, the refractive index anisotropy Δn of the liquid crystal, and the liquid crystal layer thickness d.
And the retardation value of each of the two retardation plates, the direction of the optical axis of each of the pair of polarizing plates and the two retardation plates, and both of the liquid crystal cells. Regarding the alignment direction of liquid crystal molecules in the vicinity of the substrate, while the linearly polarized light that has been incident through one of the polarizing plates is transmitted through the two retardation plates and the liquid crystal cell, the birefringence action of each retardation plate And the birefringent action of the liquid crystal layer, the light is transmitted through the other polarizing plate, and the ratio of the light intensity of each wavelength light is set to a desired ratio. .

The present invention also relates to a transmissive liquid crystal display device,
The present invention can be applied to a reflection-type liquid crystal display device, and when applied to a reflection-type liquid crystal display device, a reflection plate may be arranged on the outer surface of any of the polarizing plates.

In the color liquid crystal display device of the present invention, the incident light to the liquid crystal display device is transmitted through one polarizing plate to become linearly polarized light, and the light is transmitted through the two retardation plates and the liquid crystal cell. In the process, the polarization state is changed by the birefringence effect of each retardation plate and the liquid crystal layer, the light enters the other polarizing plate, and the light transmitted through this polarizing plate is the ratio of the light intensity of the light of each wavelength constituting the light. It becomes the light of the color according to.

The liquid crystal molecules of the liquid crystal layer of the liquid crystal cell are
In accordance with the voltage applied between the electrodes of the liquid crystal cell, the liquid crystal cell performs the rising alignment while maintaining the twist alignment state.When the voltage applied between the electrodes of the liquid crystal cell is changed, the voltage changes the alignment state of the liquid crystal molecules. The birefringence of the liquid crystal layer changes, the polarization state of the light incident on the other polarizing plate changes accordingly, and the light intensity ratio of each wavelength light of the light transmitted through the polarizing plate changes. The color of the light changes.

In a transmissive liquid crystal display device,
The light that has passed through the other polarizing plate becomes outgoing light, and in a reflective liquid crystal display device, the light that has passed through the other polarizing plate is reflected by a reflecting plate, and the other polarizing plate, the retardation plate, and the liquid crystal. The light is transmitted through the cell and the one polarizing plate and emitted.

As described above, this color liquid crystal display device
By utilizing the birefringence effect of the two retardation plates and the liquid crystal layer of the liquid crystal cell and the polarizing effect of the polarizing plate, a colored display is obtained without using a color filter. It is possible to display a plurality of colors by one pixel by controlling the voltage applied to the liquid crystal cell while obtaining a bright color display by increasing the height.

Moreover, this color liquid crystal display device is provided with two retardation plates, and the retardation of the retardation plate on the liquid crystal cell side is 2.5 to 3 of the retardation of the retardation plate on the polarizing plate side. Since it is set to 0.5 times, the polarization state of light can be largely changed by the birefringence action of the two retardation plates, and thus high-quality color display with high contrast and good color quality is realized. be able to.

In this color liquid crystal display device, for example, the twist angle of the liquid crystal molecules of the liquid crystal cell is 250 ° ± 20.
And the retardation value of the retardation plate on the liquid crystal cell side is 155.
0 nm to 1650 nm, the retardation value of the retardation plate on the polarizing plate side is set to 500 nm to 600 nm, and
When the alignment direction of liquid crystal molecules in the vicinity of the substrate on the side opposite to the side where the retardation plate of this liquid crystal cell is arranged is 0 °,
The transmission axis of the polarizing plate on which the retardation plate is arranged is 10 ° ± 10 ° in the same direction as the twist direction of the liquid crystal molecules, and the transmission axis of the polarizing plate on the opposite side is 25 ° ± 1 in the opposite direction to the twist direction.
0 ° direction, the slow axis of the retardation plate on the liquid crystal cell side is 25 ° ± 10 ° in the opposite direction to the twist direction, and the slow axis of the retardation plate on the polarizing plate side is 55 in the opposite direction to the twist direction. ± 1
If it is set to 0 ° direction, the incident light is white light,
By controlling the voltage applied to the liquid crystal cell, one pixel can display white, pink, blue, and green.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which the present invention is applied to a reflection type color liquid crystal display device will be described below with reference to FIGS. FIG. 1 is a cross-sectional view of a color liquid crystal display device of this embodiment. This color liquid crystal display device has a liquid crystal cell 1
0, and a front side polarizing plate 20 and a back side polarizing plate 21 which are arranged on the front surface side and the back surface side of the liquid crystal cell 10 with the liquid crystal cell 10 interposed therebetween.
And two retardation plates 22 and 23 which are arranged between the front side polarizing plate 20 and the liquid crystal cell 10 so as to overlap each other, and a reflecting plate 24 which is arranged on the back side of the back side polarizing plate 21. ing. The reflection plate 24 is a non-directional reflection plate in which a metal film such as silver or aluminum is deposited on the surface of a base sheet made of a resin film or the like.

The liquid crystal cell 10 has transparent electrodes 13 and 14 formed of an ITO film or the like, on which alignment films 15 and 16 are formed.
, A pair of transparent substrates (eg, glass substrates) 11,
A nematic liquid crystal 18 is sandwiched between the substrates 12, and the molecules thereof are twist-aligned between the substrates 11 and 12. The substrates 11 and 12 are joined via a frame-shaped sealing material 17, and the liquid crystal 18 Is sealed in a region surrounded by the sealing material 17 between the substrates 11 and 12.

The liquid crystal cell 10 is of a simple matrix type and has an electrode 13 provided on a substrate 11 on the front side.
Are a plurality of scanning electrodes formed in parallel with each other, and the electrodes 14 provided on the back substrate 12 are a plurality of signal electrodes formed substantially perpendicular to the scanning electrodes 13 and in parallel with each other.

The alignment films 15 and 16 provided on both the substrates 11 and 12 are horizontal alignment films made of polyimide or the like. These alignment films 15 and 16 are each subjected to an alignment process (rubbing process) in a predetermined direction, and the molecules of the liquid crystal 18 are aligned in the alignment direction on both substrates 11 and 12 (on the alignment films 15 and 16). , 16 and are tilted with respect to the surfaces of the alignment films 15 and 16 with a slight pretilt angle, and twist-aligned at a predetermined twist angle between the substrates 11 and 12.

In this color liquid crystal display device, the liquid crystal cell 10 has a twist angle of liquid crystal molecules of 250 ° ± 20.
And the product Δnd of the refractive index anisotropy Δn of the liquid crystal 18 and the liquid crystal layer thickness d is set in the range of 1500 nm to 1600 nm.

The liquid crystal cell 10 used in this embodiment has a liquid crystal 18 having a refractive index anisotropy Δn of 0.229 and a liquid crystal layer thickness d of 6.8 μm. Is 1557 nm.

The two phase difference plates 22 and 23 are
A film made of polycarbonate or the like is mechanically stretched so as to have an optical phase difference. In this color liquid crystal display device, a liquid crystal cell 10 side retardation plate (hereinafter, referred to as cell side retardation plate) 23 The retardation is set to 2.5 to 3.5 times the retardation of the retardation plate 22 on the polarizing plate 20 side (hereinafter referred to as the polarizing plate side retardation plate) 22.

In this embodiment, the retardation film 23 on the cell side has a retardation value of 1550 nm to 1650 nm.
Of the retardation film 22 on the polarizing plate side
As a retardation value of 500 nm to 600 nm
Therefore, the retardation of the cell-side retardation plate 23 is 2.75 to 3.1 times the retardation of the polarizing plate-side retardation plate 22.

Further, in this embodiment, the retardation plate having the larger retardation value, that is, the cell-side retardation plate 23.
The x-axis direction which is the stretching direction (the slow axis direction), the y-axis direction (the direction along the retardation plate surface and the direction orthogonal to the stretching direction), and the z-axis direction (the normal direction of the retardation plate). each of the refractive indices n _x and), n _y, has a refractive index anisotropy according to the difference between n _z, and these x, y, z-axis direction of the refractive indices n _x, n
_A biaxial retardation plate in which _y and n _z have a relationship of n _x > n _z > n _y is used.

The retardation plate having a smaller retardation value, that is, the polarizing plate side retardation plate 22 has a refractive index corresponding to the difference between the refractive indices n _x and n _{y in} the x-axis direction and the y-axis direction. It has anisotropy and the refractive indices n _x and n _{y in the} x and y axis directions are
Is a uniaxial retardation plate having a relationship of n _x > n _y .

Then, the above-mentioned two retardation plates 22 and 23
Are arranged such that their optical axes (slow axis or fast axis) are obliquely shifted by a predetermined angle.
0 is arranged such that its optical axis is slanted at a predetermined angle with respect to the optical axis of the polarizing plate side retardation plate 22, and the back polarizing plate 21 has its optical axis oriented on the back substrate 12 of the liquid crystal cell 10. It is arranged so as to be slanted by a predetermined angle with respect to the alignment direction of liquid crystal molecules in the vicinity.

FIG. 2 shows both substrates 11 of the liquid crystal cell 10,
12 and the directions of the optical axes (here, transmission axes) of the polarizing plates 20, 21 on the front and back and the optical axes (here, slow axes) of the two retardation plates 22, 23. FIG. 4 is a diagram viewed from the front side of the liquid crystal display device.

As shown in FIG. 2, the liquid crystal molecules of the liquid crystal cell 10 extend from the rear substrate 12 to the front substrate 11 as shown by the broken line arrow in the twist direction, and rotate 250 ° clockwise when viewed from the front side. Twisted at a twist angle of ± 20 °. The alignment direction 11a of liquid crystal molecules near the front substrate 11 of the liquid crystal cell 10 (alignment treatment direction of the alignment film 15) is 35 ° ± 10 clockwise relative to the horizontal axis S of the liquid crystal cell 10 when viewed from the surface side. The orientation direction of liquid crystal molecules in the vicinity of the rear substrate 12 (orientation treatment direction of the orientation film 16) 12a is 35 ° ± 10 ° counterclockwise with respect to the horizontal axis S when viewed from the surface side. .

When the liquid crystal molecule orientation direction 12a in the vicinity of the back substrate 12 of the liquid crystal cell 10 is 0 °, the transmission axis 20a of the front side polarizing plate 20 has the transmission direction 20a of the liquid crystal molecules as viewed from the front side ( It is in the direction of 10 ° ± 10 ° in the same direction as the twist direction viewed from the surface side, and the transmission axis 21a of the back side polarizing plate 21 is 25 ° ± 10 ° in the direction opposite to the twist direction when viewed from the surface side. In the direction.

The slow axis 22 of the retardation film 22 on the polarizing plate side
a is 55 ° ± 10 ° in the direction opposite to the twist direction when viewed from the surface side with respect to the 0 ° direction, and the slow axis 23a of the cell-side retardation plate 23 is 0 ° above the 0 ° direction. 25 ° to the direction opposite to the twist direction when viewed from the front side
It is in the direction of ± 10 °.

This color liquid crystal display device uses external light such as natural light or indoor illumination light and reflects the light incident from the front surface side by the reflection plate 24 arranged on the rear surface side for display. The liquid crystal display device is driven for display by applying a voltage between the electrodes 13 and 14 of both substrates 11 and 12 of the liquid crystal cell 10.

In this color liquid crystal display device, incident light from the surface side thereof passes through the front side polarizing plate 20 to become linearly polarized light, and the light passes through the two retardation plates 22 and 23 and the liquid crystal cell 10. The light passes through and enters the back-side polarizing plate 21.

Further, in this color liquid crystal display device, the slow axis 22a of the polarizing plate side retardation plate 22 is slanted with respect to the transmission axis 20a of the front side polarizing plate 20, and the polarizing plate side retardation plate 22 is provided. Since the slow axis 22a of the cell side retardation plate 23a and the slow axis 23a of the cell side retardation plate 23 are obliquely displaced from each other, the linearly polarized light transmitted through the transmission axis 20a of the front side polarizing plate 20 and incident on the polarizing plate side In the process of passing through the phase difference plate 22, it is subjected to birefringence effect by the phase difference plate 22, each wavelength light becomes elliptically polarized light with different polarization state, and further in the process of passing through the cell side phase difference plate 23. Due to the birefringence effect of the phase difference plate 23, the polarization state of each wavelength light is further changed.

Further, this light is subjected to birefringence by the liquid crystal layer of the liquid crystal cell 10 in the process of passing through the liquid crystal cell 10 and becomes light in which the polarization state of each wavelength light is further changed, and is reflected by the back side polarizing plate 21. Only light having a component that is incident and that is parallel to the transmission axis 21a of the back-side polarizing plate 21 passes through the back-side polarizing plate 21, and becomes colored light of a color corresponding to the light quantity ratio of each wavelength light that constitutes this transmitted light. .

Further, the liquid crystal molecules of the liquid crystal layer of the liquid crystal cell 10 are vertically aligned while maintaining the twist alignment state according to the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10. The birefringence action of the liquid crystal layer changes according to the applied voltage.

Therefore, the polarization state of each wavelength light of the light which is transmitted through the two retardation plates 22 and 23 and the liquid crystal cell 10 in order and is incident on the back side polarizing plate 21 depends on the voltage applied to the liquid crystal cell 10. The light amount ratio of each wavelength light of the light transmitted through the back side polarizing plate 21 changes, and the color of the colored light changes.

The birefringence of the liquid crystal layer of the liquid crystal cell 10 decreases as the rising angle of the liquid crystal molecules increases, and when the liquid crystal molecules rise and rise almost vertically, the birefringence of the liquid crystal layer is almost eliminated. Lost 2
The light that has been subjected only to the birefringence action by the two retardation plates 22 and 23 enters the back-side polarizing plate 21.

The light transmitted through the back side polarizing plate 21, that is, the colored light is reflected by the reflecting plate 24, and the back side polarizing plate 2
1 and the liquid crystal cell 10 and the phase difference plates 23 and 22 and the front side polarizing plate 20 to be emitted to the front side.

The light reflected by the reflection plate 24, in the process of being emitted to the front surface side, has a birefringence action opposite to that at the time of incidence by the liquid crystal layer of the liquid crystal cell 10 and the two phase difference plates 23 and 22. Since the linearly polarized light is substantially the same as when it is received and is incident on the front-side polarizing plate 20, the light transmitted through the front-side polarizing plate 20 and emitted is almost the same as the light reflected by the reflector 24. Light.

As described above, the color liquid crystal display device has
By utilizing the birefringence action of the two retardation plates 22 and 23 and the liquid crystal layer of the liquid crystal cell 10 and the polarizing action of the polarizing plates 20 and 21, a colored display is obtained without using a color filter. Accordingly, a bright color display can be obtained by increasing the light transmittance, and a plurality of colors can be displayed by one pixel by controlling the voltage applied to the liquid crystal cell 10.

Moreover, the color liquid crystal display device is provided with two retardation plates 22 and 23, and retardation of the retardation plate 23 on the liquid crystal cell 10 side of the retardation plate 22 on the polarizing plate 20 side of the retardation plate 22. Retardation of 2.5 ~
Since it is set to 3.5 times (2.75 to 3.1 times in this embodiment), the polarization state of light can be largely changed by the birefringence action of the two retardation plates 22 and 23. It is possible to realize high-quality color display with high contrast and good color quality.

The colors that can be displayed by one pixel of the color liquid crystal display device are the twist angle of the liquid crystal molecules of the liquid crystal cell 10 and the value of Δnd, and the retardation values of the two retardation plates 22 and 23, respectively. It is determined by the directions of the optical axes of the front and back polarizing plates 20 and 21 and the two retardation plates 22 and 23, and the alignment direction of liquid crystal molecules in the vicinity of both substrates 11 and 12 of the liquid crystal cell 10.

That is, as in this embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 °, and the value of Δnd of the liquid crystal cell 10 is 1500 nm to 1600 n.
m, the retardation value of the polarizing plate side retardation plate 22 is 500 nm to 600 nm, the retardation value of the cell retardation plate 23 is 1550 nm to 1650 nm, and the opposite side of the liquid crystal cell 10 from the retardation plate arrangement side. Of the retardation plates 22 and 2 with the orientation direction 12a of the liquid crystal molecules in the vicinity of the substrate (back side substrate) 12 of FIG.
Transmission axis 2 of polarizing plate (front side polarizing plate) 20 on which 3 is arranged
0a in the same direction as the twist direction of the liquid crystal molecules by 10 ° ±
In the 10 ° direction, the transmission axis 21a of the polarizing plate (back side polarizing plate) 21 on the opposite side is set to 25 ° ± 10 ° in the direction opposite to the twist direction.
Direction, the slow axis 23a of the retardation film 23 on the liquid crystal cell side is in the direction opposite to the twist direction by 25 ° ± 10 °, and the polarizing plate 2
The color that can be displayed by one pixel when the slow axis 22a of the phase difference plate 22 on the 0 side is set to 55 ° ± 10 ° in the direction opposite to the twist direction is when the incident light is white light. , Achromatic bright white, and pink, blue, and green.

FIG. 3 is a CIE chromaticity diagram showing changes in the display color of the color liquid crystal display device. The display color of the color liquid crystal display device is such that the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is high. As I went, white → pink →
Change from blue to green.

That is, in the above color liquid crystal display device,
The liquid crystal molecules of the liquid crystal cell 10 are in the initial alignment state (substrate 11,
When the liquid crystal is slightly oriented from the twisted state in which it is most inclined with respect to the 12 planes, the two retardation plates 22 and
23, the birefringence of the liquid crystal layer and the birefringence of the liquid crystal layer cancel each other, and the light transmitted through the retardation plates 22, 23 and the liquid crystal cell 10 becomes almost linearly polarized light, The light that has entered and transmitted through the back-side polarizing plate 21 becomes achromatic white light. Further, when the voltage applied to the liquid crystal cell 10 is increased, the liquid crystal molecules further rise and align, and accordingly, the retardation plate 2
2, 23 and the liquid crystal cell 10, the polarization state of each wavelength light of the light is changed, the color of the light transmitted through the back side polarizing plate 21 is
It changes to pink, blue and green.

Therefore, according to this color liquid crystal display element, the color of each pixel is changed to each color of white, pink, blue and green to realize a multicolor display with rich colors called multicolor. You can

The brightness of each display of white, pink, blue, and green (value when the brightness of incident light is 100%) is 77% for white, 50% for pink, and 34% for blue. It is 59% in green, and the display color of pink is a clear color close to red.

Further, in the above color liquid crystal display device, the phase difference between when the light is transmitted vertically through the liquid crystal layer of the liquid crystal cell 10 and when the light is transmitted obliquely is compensated by the phase difference plates 22 and 23. The viewing angle dependency in which the display color changes depending on the viewing direction of the display can be reduced, and the viewing angle can be widened.

The retardation plates 22 and 23 of the liquid crystal cell 1 have a relatively small change in birefringence due to a change in temperature as compared with the change in birefringence of the liquid crystal layer of the liquid crystal cell 10.
The temperature dependence of the total birefringence between the liquid crystal layer of 0 and the retardation plates 22 and 23 is reduced, and therefore the change in display color due to temperature can also be reduced.

The color liquid crystal display device of the above embodiment displays white, which is a bright display of achromatic color, and each color of pink, blue, and green, with one pixel. The colors that can be displayed are the twist angle of the liquid crystal molecules of the liquid crystal cell 10 and the value of Δnd, and the two retardation plates 22 and 23.
Value of each retardation and polarizing plate 2 on the front and back
It is possible to arbitrarily select the directions of the optical axes of 0 and 21 and the two retardation films 22 and 23 and the alignment direction of liquid crystal molecules in the vicinity of both substrates 11 and 12 of the liquid crystal cell 10. it can.

The two retardation plates 22 and 23 may both be biaxial retardation plates or both may be uniaxial retardation plates. Further, the retardation plates on the liquid crystal cell 10 side may be used. Two
3 as a uniaxial retardation plate, and the retardation plate 22 on the polarizing plate 20 side
May be a biaxial retardation plate.

Further, the color liquid crystal display device of the above-mentioned embodiment is a reflection type in which the reflection plate 24 is arranged on the back surface side, but the present invention is a transmission type in which light from the backlight is used for display. The present invention can also be applied to the color liquid crystal display device, and also to the color liquid crystal display device in which a semi-transmissive reflection plate is arranged on the back surface side to have both reflective and transmissive functions.

Also in this case, two retardation plates are placed so as to overlap each other between one of the pair of polarizing plates and the liquid crystal cell,
The retardation of the liquid crystal cell side retarder,
The retardation of the retardation plate on the polarizing plate side is 2.5 to 3.5.
And the product of the liquid crystal layer thickness d and the twist angle of the liquid crystal molecules of the liquid crystal cell and the refractive index anisotropy Δn of the liquid crystal.
The value of nd, the retardation value of each of the two retardation plates, the direction of the optical axis of each of the pair of polarizing plates and the two retardation plates, and the vicinity of both substrates of the liquid crystal cell. In the alignment direction of liquid crystal molecules in the above, while the linearly polarized light which is incident through one of the polarizing plates is transmitted through the two retardation plates and the liquid crystal cell, the birefringence action of each retardation plate and the liquid crystal layer When the light is transmitted through the other polarizing plate and the light intensity ratio of each wavelength light is set to a desired ratio, the voltage applied to the liquid crystal cell is controlled. As a result, one pixel can display a plurality of colors.

[0057]

According to the color liquid crystal display device of the present invention, it is possible to obtain a bright color display by increasing the light transmittance, display a plurality of colors with one pixel, and have a high contrast. Further, it is possible to realize high-quality color display with good color quality.

In the color liquid crystal display device of the present invention, the twist angle of the liquid crystal molecules of the liquid crystal cell is 250 ° ± 2.
The value of 0 ° and Δnd is 1500 nm to 1600 nm,
The retardation value of the retardation plate on the liquid crystal cell side is set to 15
The retardation value of the retardation plate on the polarizing plate side is set to 50 nm to 1650 nm, the retardation value of the liquid crystal cell is set to 500 nm to 600 nm, and the orientation direction of the liquid crystal molecules in the vicinity of the substrate on the side opposite to the side where the retardation plate of this liquid crystal cell is arranged is 0 °. In this case, the transmission axis of the polarizing plate on the side where the retardation plate is arranged is in the same direction as the twist direction of the liquid crystal molecules by 10 ° ± 10 °, and the transmission axis of the polarizing plate on the opposite side is in the opposite direction from the twist direction. At 25 °
± 10 ° direction, the slow axis of the retardation plate on the liquid crystal cell side is in the opposite direction to the twist direction, 25 ° ± 10 ° direction, and the slow axis of the retardation plate on the polarizing plate side is in the opposite direction to the twist direction. 55 °
If the incident light is white light, by setting the direction to ± 10 °, white, pink, blue, and green can be displayed by one pixel by controlling the voltage applied to the liquid crystal cell.

[Brief description of drawings]

FIG. 1 is a sectional view of a color liquid crystal display device according to an embodiment of the present invention.

FIG. 2 shows an alignment direction of liquid crystal molecules in the vicinity of both substrates of a liquid crystal cell in the same color liquid crystal display device, an optical axis of front and back polarizing plates, and an optical axis of two retardation plates on the surface of the liquid crystal display device. View from the side.

FIG. 3 is a C showing a change in display color of the color liquid crystal display device.
IE chromaticity diagram.

[Explanation of symbols]

 10 ... Liquid crystal cell 11a ... Alignment direction of liquid crystal molecules near the front substrate 12a ... Alignment direction of liquid crystal molecules near the back substrate 20, 21 ... Polarizing plates 20a, 21a ... Transmission axis 22, 23 ... Phase difference plates 22a, 23a … Slow axis 24… Reflector

Claims (5)

[Claims] 1. A liquid crystal cell comprising a 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 pair of polarizing plates arranged with the liquid crystal cell sandwiched therebetween. Two retardation plates arranged to overlap each other between any one of the polarizing plates and the liquid crystal cell, the retardation of the retardation plate on the liquid crystal cell side of the two retardation plates, The retardation of the retardation plate on the polarizing plate side is set to 2.5 to 3.5 times, and the twist angle of the liquid crystal molecules of the liquid crystal cell and the product Δnd of the refractive index anisotropy Δn of the liquid crystal and the liquid crystal layer thickness d are Value and the above 2
Retardation values of the respective retardation plates, optical axis directions of the pair of polarizing plates and the two retardation plates, and alignment directions of liquid crystal molecules in the vicinity of both substrates of the liquid crystal cell. While the linearly polarized light that has been transmitted through one of the polarizing plates and is incident thereon is subjected to the birefringent action of each retardation plate and the birefringent action of the liquid crystal layer while passing through the two retardation plates and the liquid crystal cell. A color liquid crystal display device, characterized in that the light is transmitted through the other polarizing plate and the ratio of the light intensities of the respective wavelength lights is set to a desired ratio. 2. The twist angle of the liquid crystal molecules of the liquid crystal cell is 250.
Is ± 20 °, and the value of Δnd is 1500 nm to 160
It is 0 nm, The color liquid crystal display device of Claim 1 characterized by the above-mentioned. 3. The retardation value of the retardation plate on the liquid crystal cell side is 1550 nm to 1650 nm, and the retardation value of the retardation plate on the polarizing plate side is 500 nm to 600 nm.
The color liquid crystal display device according to claim 1, wherein 4. The liquid crystal molecules of the liquid crystal cell are twisted at a twist angle of 250 ° ± 20 ° in a predetermined direction from the substrate on the side opposite to the side on which the retardation plate is arranged toward the substrate on the side where the retardation plate is arranged. When the alignment direction of the liquid crystal molecules near the substrate opposite to the side where the retardation plate is arranged is 0 °, the transmission axis of the polarizing plate on the side where the retardation plate is arranged is 10 ° ± 10 ° in the same direction as the twist direction of the liquid crystal molecules, and the transmission axis of the polarizing plate on the opposite side is 25 ° in the opposite direction to the twist direction.
± 10 ° direction, the slow axis of the retardation plate on the liquid crystal cell side is in the opposite direction to the twist direction, 25 ° ± 10 ° direction, and the slow axis of the retardation plate on the polarizing plate side is in the opposite direction to the twist direction. 55 °
The color liquid crystal display device according to claim 1, wherein the color liquid crystal display device is in a direction of ± 10 °. 5. The color liquid crystal display device according to claim 1, wherein a reflection plate is disposed on the outer surface of one of the polarizing plates.