JPH095702A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE: To obtain a sufficiently bright color display by coloring light without using color filters, to display plural colors with the same pixels, to display the desired colors with sufficient color purity, to widen a visual field angle and to lessen the change in the displayed colors by temp. CONSTITUTION: This color liquid crystal display device has a liquid crystal cell 10, front and rear polarizing plates 20, 21 and a phase difference plate 22. The twist angle of the liquid crystal molecules of the liquid crystal cell 10 is specified to 250 deg. ±20 deg., Δnd to 1300 to 1750nm and the retardation of the phase difference plate to 1450 to 1850nm. The directions of the optical axes of the polarizing plates 20, 21 and the phase difference plate 22 and the liquid crystal molecule orientation direction near both substrates of the liquid crystal cell 10 are so set that the incident linearly polarized light transmitted through the front side polarizing plate 20 is made into the light of the respective wavelength light rays made into the elliptically polarized light varying respectively in the polarization state by the double refractive effect of the liquid crystal layer of the liquid crystal cell 10 and the phase difference plate 20 and that the ratio of the light intensity of the respective wavelength light rays transmitted through the rear side polarizing plate 21 of the light attains a desired ratio.

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] The liquid crystal display device has a transmissive type that displays by using light from the backlight, and a liquid crystal display device that uses external light (natural light, indoor illumination light, or the like) and arranges the light on the back side. There is a reflection type in which light is reflected by a reflection plate for display. When the color liquid crystal display device is a reflection type, light that enters from the front surface side, is reflected by the reflection plate on the back surface side, and exits to the front surface side is emitted. Since the light intensity is reduced twice by passing through the color filter twice, the display becomes extremely dark and can hardly be used as a display device.

Moreover, in the above color liquid crystal display device, the display color of each pixel is determined by the color of the color filter corresponding to the 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 each corresponding to a color filter of three primary colors of red, green, and blue. 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 liquid crystal cell sandwiching liquid crystal between a pair of substrates, and a polarizing plate is disposed on each of the front side and the back side. In this ECB type liquid crystal display device, In the process of passing through the liquid crystal cell, the linearly polarized light transmitted through one of the polarizing plates becomes elliptically polarized light in which each wavelength light has a different polarization state due to the birefringence action of the liquid crystal layer, and the light is converted into the other light. The light that has entered the polarizing plate and transmitted through the other polarizing plate becomes colored light having a color corresponding to the ratio of the light intensities of the respective wavelength lights constituting the light.

That is, the ECB type liquid crystal display device obtains a colored display without using a color filter by utilizing the birefringent action of the liquid crystal layer of the liquid crystal cell and the polarizing action of the polarizing plate. Since there is no light absorption by the filter, the light transmittance can be increased.

For this reason, the ECB type liquid crystal display device can be used as a reflection type display device by arranging a reflection plate on the back surface side. Even in this case, a sufficiently bright color display can be obtained. .

Moreover, 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 in accordance with the voltage applied between the electrodes of the two 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 to the liquid crystal cell, and therefore, the same pixel displays a plurality of colors. be able to.

[0010]

However, in the conventional ECB type liquid crystal display device, the color purity of the display color is low, the viewing angle is narrow, and the display color changes depending on the viewing direction. However, since the birefringence of the liquid crystal layer of the liquid crystal cell changes due to the change in temperature, the display color also changes depending on the temperature.

The present invention provides a sufficiently bright color display by coloring light without using a color filter.
A color liquid crystal display device capable of displaying a plurality of colors with the same pixel, further increasing the color purity of the display color sufficiently, further increasing the viewing angle and reducing the change in display color due to temperature. The purpose is to provide.

[0012]

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. The liquid crystal cell includes a pair of polarizing plates arranged in a sandwiched manner and one retardation plate arranged between the one polarizing plate and the liquid crystal cell, and the twist angle of liquid crystal molecules of the liquid crystal cell is 250 °. ± 20 °, liquid crystal refractive index anisotropy Δ
The value of the product Δnd of n and the liquid crystal layer thickness d is 1300 nm to 17
50 nm, the retardation value of the retardation plate is 145
0 nm to 1850 nm, and the direction of the optical axis of each of the pair of polarizing plates and the retardation plate and the alignment direction of liquid crystal molecules in the vicinity of both substrates of the liquid crystal cell,
While the linearly polarized light transmitted through the polarizing plate is transmitted through the retardation plate and the liquid crystal cell, each wavelength light is generated by the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer of the liquid crystal cell. It becomes elliptically polarized light having a different polarization state, and the elliptically polarized light further passes through the polarizing plate, and the ratio of the light intensity of each wavelength light is set to be a desired ratio. It is a feature.

The present invention can be applied to a transmissive liquid crystal display device for displaying by utilizing light from a backlight and a reflective liquid crystal display device for displaying by utilizing external light. When it is applied to a reflection type liquid crystal display device, a reflection plate may be arranged on the outer surface of one of the polarizing plates.

In the retardation plate, the refractive index n _x in the stretching direction on the plane and the refractive index n _{y in the} direction orthogonal to the stretching direction on the plane have a relationship of n _x > n _y. Even with a uniaxial retardation plate, the refractive indices n _x and n _y on the plane and the refractive index n _{z in the} thickness direction are n _x > n.
_It may be a biaxial retardation plate having a relationship of _z > _ny , but when the retardation plate is a biaxial retardation plate, as this biaxial retardation plate, (n _x −n those n _z value represented by _{z) / (n x -n y} ) is 0.3 to 0.7, more preferably, to use those n _z value of 0.45 ± 0.1 Is desirable.

[0015]

In the color liquid crystal display device of the present invention, the light incident on the liquid crystal display device is transmitted through one polarizing plate to become linearly polarized light, and the light is transmitted through the retardation plate and the liquid crystal cell and is polarized in the other polarized light. Incident on the plate.

On the other hand, the liquid crystal molecules of the liquid crystal layer of the liquid crystal cell are vertically aligned while maintaining the twist alignment state according to the voltage applied between the electrodes of the liquid crystal cell, but the alignment state of the liquid crystal molecules becomes the twist alignment state. In some cases, linearly polarized light that has passed through one of the polarizing plates and is incident can be changed in polarization state by the birefringence action of the liquid crystal layer of the retardation plate and the liquid crystal cell in the process of passing through the retardation plate and the liquid crystal cell. Each wavelength light becomes elliptically polarized light with different polarization state, enters the other polarizing plate, and the light transmitted through this polarizing plate becomes the ratio of the light intensity of each wavelength light that constitutes the light. It becomes the light of the corresponding color.

When the voltage applied between the electrodes of the liquid crystal cell is changed, the birefringence action of the liquid crystal layer is changed due to the change in the alignment state of the liquid crystal molecules due to the voltage, and the incident light is incident on the other polarizing plate. Since the polarization state of the reflected light changes, the light intensity ratio of each wavelength light of the light transmitted through this polarizing plate changes, and 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.

Thus, this color liquid crystal display device is
By utilizing the birefringence effect of the retardation plate and the liquid crystal layer of the liquid crystal cell and the polarizing action of the polarizing plate, a colored display is obtained without using a color filter. By obtaining a bright color display and controlling the voltage applied to the liquid crystal cell, a plurality of colors can be displayed in the same pixel.

In this color liquid crystal display device, the twist angle of the liquid crystal molecules of the liquid crystal cell is 250 ° ±.
And the value of Δnd of this liquid crystal cell is 1300.
nm to 1750 nm and the retardation value of the retardation plate is set to a large value of 1450 nm to 1850 nm, so that the other polarized light receives the birefringence action of the retardation plate and the birefringence action of the liquid crystal layer of the liquid crystal cell. Since the polarization state of the light incident on the plate largely changes according to the voltage applied to the liquid crystal cell, it is possible to display a desired color with sufficiently high color purity.

Further, in the color liquid crystal display device of the present invention, the phase difference between when light is transmitted vertically through the liquid crystal layer of the liquid crystal cell and when it is transmitted obliquely is compensated by the retardation plate, so that the viewing angle is increased. Becomes wider.

Moreover, in the retardation plate, the change in birefringence due to temperature change is much smaller than the change in birefringence of the liquid crystal layer of the liquid crystal cell. The temperature dependence of the total birefringence is reduced, and therefore the change in display color due to temperature is also reduced.

According to this color liquid crystal display device, the value of Δnd of the liquid crystal cell is 1300 nm to 1750 n.
and a retardation value of 1450 as a retardation plate.
By using as large as nm to 1850 nm,
Since the desired color can be displayed with sufficient color purity and the viewing angle can be widened and the change in the display color due to temperature can be reduced by providing only one retardation plate, the provision of the retardation plate The decrease in light transmittance is slight, and high quality color display can be obtained with sufficient brightness.

Further, the retardation plate may be a normal uniaxial retardation plate or a biaxial retardation plate. If a biaxial retardation plate is used as the retardation plate, , The viewing angle becomes wider.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first 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 includes a liquid crystal cell 10 and
A front-side polarizing plate 20 and a back-side polarizing plate 21 arranged on the front surface side and the back surface side of the liquid crystal cell 10, and one unit disposed between the front-side polarizing plate 20 and the liquid crystal cell 10. It comprises a phase difference plate 22 and a reflection plate 23 arranged on the back side of the back side polarizing plate 21. The reflection plate 23 is an omnidirectional 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 14 provided on a substrate 12 on the front side.
Is a plurality of scanning electrodes formed in parallel with each other, and the electrodes 13 provided on the substrate 11 on the back side are signal electrodes formed in parallel with each other and substantially perpendicular to the scanning electrodes 14.

Further, the alignment films 15 and 16 provided on the both substrates 11 and 12 are horizontal alignment films made of polyimide or the like, and the alignment films 15 and 16 are each subjected to an alignment treatment (rubbing treatment) in a predetermined direction. The molecules of the liquid crystal 18 are regulated by the alignment films 15 and 16 in the alignment direction on both the substrates 11 and 12 (on the alignment films 15 and 16), and a slight pretilt with respect to the surfaces of the alignment films 15 and 16. In a state of being inclined at an angle, the two substrates 11 and 12 are twist-aligned at a predetermined twist angle.

In this color liquid crystal display device, the optical axes of the front-side polarizing plate 20 and the back-side polarizing plate 21 and the retardation plate 22 (transmission axis or absorption axis in the polarizing plate, slow axis in the retardation plate). Alternatively, the linearly polarized light that has entered the retardation plate 22 and the liquid crystal cell 10 in the direction of the fast axis) and the alignment direction of the liquid crystal molecules in the vicinity of the substrates 11 and 12 of the liquid crystal cell 10 is transmitted through the front polarizing plate 20 and is incident. While transmitting the light, each wavelength light becomes elliptically polarized light having a different polarization state due to the birefringence effect of the retardation plate 22 and the birefringence effect of the liquid crystal layer of the liquid crystal cell 10, and the back side of the light It is set so that the ratio of the light intensity of each wavelength light transmitted through the polarizing plate 21 becomes a desired ratio.

FIG. 2 shows both substrates 11 and 12 of the liquid crystal cell 10.
Orientation of liquid crystal molecules in the vicinity of
FIG. 3 is a diagram showing the direction of the optical axis of the retardation plate 22 viewed from the front side of the liquid crystal display device.
The twist angle of the liquid crystal molecules is set to 250 ° ± 20 °, and the transmission axes 20a, 21
a is arranged with the following orientation, and the retardation plate 22 is arranged with its slow axis 22a oriented as follows.

As shown in FIG. 2, the alignment direction of the liquid crystal molecules (alignment film 1 in the vicinity of the rear substrate 11 of the liquid crystal cell 10).
The orientation treatment direction 5a) 11a is 35 ° ± 1 counterclockwise (counterclockwise in the figure) when viewed from the surface side with respect to the horizontal axis S of the liquid crystal cell 10.
The orientation of liquid crystal molecules in the direction of 0 ° and in the vicinity of the front substrate 12 (the orientation processing direction of the alignment film 16) 12a is the same as the liquid crystal molecule orientation direction 11a in the vicinity of the back substrate 11.
On the other hand, the liquid crystal molecules are in the direction of 70 ° ± 10 ° clockwise when viewed from the front surface side, and the liquid crystal molecules are directed from the rear surface side substrate 11 to the front surface side substrate 12 as shown by the broken line arrow in FIG. The twist orientation is clockwise with a twist angle of 250 ° ± 20 °. The twist angle of the liquid crystal molecules is preferably 250 ° ± 10 °, more preferably 250 °.

When the liquid crystal molecule alignment direction 11a in the vicinity of the back surface side substrate 11 of the liquid crystal cell 10 is 0 °, the transmission axis 20a of the front side polarizing plate 20 is the liquid crystal of the liquid crystal cell 10 when viewed from the front side. The direction of 65 ° ± 10 ° (preferably 65 ° ± 5 °, more preferably 65 °) in the direction opposite to the molecular twist direction (twist direction viewed from the surface side), the transmission axis 21a of the back side polarizing plate 21 is 45 ° ± 10 ° in the same direction as the liquid crystal molecule twist direction when viewed from the surface side
(Preferably 45 ° ± 5 °, more preferably 45 °), and the slow axis 22a of the phase difference plate 22 is 0 ° above.
15 ° ± 10 ° (desirably 15 ° ± 5) in the direction opposite to the liquid crystal molecule twist direction when viewed from the surface side with respect to
°, and more preferably 15 °).

Further, in this embodiment, the liquid crystal cell 10 is used.
As the liquid crystal 18, a liquid crystal 18 having a refractive index anisotropy Δn of 0.207, a liquid crystal layer thickness d of 6.8 μm, and a product Δnd of the refractive index anisotropy Δn and the liquid crystal layer thickness d of 1408 nm is used. At the same time, the retardation plate 22 having a retardation value of 1557 nm is used.

The retardation plate 22 is a uniaxial retardation plate, and has a refractive index n _x in the stretching direction (slow axis direction) on the plane and a direction orthogonal to the stretching direction on the plane. refractive index and n _y are in relation of n _x> n _y, the value of the product Δnd of the refractive index anisotropy _{Δn (Δn = n x -n y} ) and the plate thickness d is of 1557 nm.

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 23 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 liquid crystal cell 10 and the retardation plate 22 and back side polarizing plate 21. Light incident on the back side polarizing plate 21 is reflected by the reflecting plate 23, passes through the back side polarizing plate 21, the liquid crystal cell 10, the retardation plate 22 and the front side polarizing plate 20 and is emitted to the front side. To do.

In this embodiment, since the retardation plate 22 is arranged between the front side polarizing plate 20 and the liquid crystal cell 10, the light transmitted through the front side polarizing plate 20 and incident on the retardation plate 22. Through the liquid crystal cell 10 to enter the liquid crystal cell 1
0, is incident on the back-side polarizing plate 21 and is transmitted through the back-side polarizing plate 21 and reflected by the reflecting plate 23. The light is reflected by the back-side polarizing plate 21, the liquid crystal cell 10, the retardation plate 22, and the front-side polarizing plate. And 20 are sequentially transmitted and emitted to the surface side.

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, but the alignment state of the liquid crystal molecules is maintained. Is in the twist alignment state, the linearly polarized light that has passed through the front-side polarizing plate 20 and is incident is
In the process of passing through the phase difference plate 22 and the liquid crystal cell 10, the polarization state was changed by the birefringence effect of the phase difference plate 22 and the liquid crystal layer of the liquid crystal cell 10, and each wavelength light became elliptically polarized light having a different polarization state. The light is incident on the back-side polarizing plate 21 and the light transmitted through the back-side polarizing plate 21 becomes light of a color corresponding to the light intensity ratio of each wavelength light constituting the light, and the light is reflected. The light is reflected by the plate 23 and is emitted to the front side of the liquid crystal display device.

When the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is changed, the birefringence of the liquid crystal layer changes due to the change in the alignment state of the liquid crystal molecules due to the voltage. The birefringence of the liquid crystal layer decreases as the rising angle of the liquid crystal molecules increases.

When the birefringence of the liquid crystal layer of the liquid crystal cell 10 changes, the polarization state of the light that passes through the retardation plate 22 and the liquid crystal cell 10 and enters the back side polarizing plate 21 changes accordingly. , The light intensity ratio of each wavelength light of the light transmitted through the back side polarizing plate 21 changes, the color of the light changes, and the light of that color is reflected by the reflecting plate 23 to the front side of the liquid crystal display device. Emit.

As described above, the color liquid crystal display device is
By using the birefringence effect of the retardation plate 22 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. By increasing the rate to obtain a bright color display and controlling the voltage applied to the liquid crystal cell 10, a plurality of colors can be displayed in the same pixel.

In this color liquid crystal display device, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ±.
And the value of Δnd of the liquid crystal cell 10 is set to 20 °.
Since the retardation value of the retardation plate 22 is set to 08 nm and the retardation value of the retardation plate 22 is increased to 1557 nm, it is affected by the birefringence action of the retardation plate 22 and the birefringence action of the liquid crystal layer of the liquid crystal cell 10. Since the polarization state of the light incident on is greatly changed according to the voltage applied to the liquid crystal cell 10, a desired color can be displayed with sufficiently high color purity.

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, the Δnd of the liquid crystal cell 10, the retardation value of the retardation plate 22, and the front side polarizing plate 20. And the orientations of the respective optical axes of the back side polarizing plate 21 and the retardation plate 22, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 °, and the Δ of the liquid crystal cell 10 is Δ as in this embodiment.
The value of nd is 1408 nm, the value of retardation of the retardation plate 22 is 1557 nm, and the front and back polarizing plates 2
The direction of the transmission axes 20a and 21a of 0 and 21, and the phase difference plate 2
When the direction of the slow axis 22a of No. 2 is set to the direction shown in FIG. 2, the color that can be displayed by one pixel is white when the incident light is white light, and white that is an achromatic bright display and light. The three primary colors are red, green and blue.

FIG. 3 is a CIE chromaticity diagram showing a change in display color of the color liquid crystal display device. The display color of this color liquid crystal display device is such that liquid crystal molecules rise and align between the electrodes 13 and 14 of the liquid crystal cell 10. In a non-selected state in which no voltage is applied, that is, in a state in which liquid crystal molecules are twist-aligned at an initial pretilt angle, white is generated. When a voltage is applied between the electrodes 13 and 14 of the liquid crystal cell 10, the applied voltage is The display color changes from white, which is the initial display color, in the order of red, blue, and green as the value is increased.

The relationship between the inter-electrode voltage (effective value) of the liquid crystal cell 10 and the display color is, for example, 2.04 V or less ... White 2.15 V to 2.17 V ... Red 2.18 V to 2.22 V ... Green. 2.26V or higher ... Blue.

Therefore, according to this color liquid crystal display device, red, green and blue which are the three primary colors of light can be displayed in the same pixel, and a multicolor display with rich colors called multicolor can be realized. .

Further, in this color liquid crystal display device, since the phase difference between the time when light is vertically transmitted through the liquid crystal layer of the liquid crystal cell 10 and the time when it is obliquely transmitted, the phase difference plate 22 compensates for the display. The viewing angle can be widened by reducing the viewing angle dependency that the display color changes depending on the viewing direction.

Further, since the change in the birefringence due to the change in temperature is considerably smaller than the change in the birefringence of the liquid crystal layer of the liquid crystal cell 10, the retardation plate 22 is positioned as the liquid crystal layer of the liquid crystal cell 10. The temperature dependence of the total birefringence with the phase difference plate 22 is reduced, and therefore the color liquid crystal display device described above can also reduce the change in display color due to temperature.

Moreover, in this color liquid crystal display device, the value of Δnd of the liquid crystal cell 10 is set to 1408 nm, and the retardation plate 2 is used.
By using a large retardation value of 1557 nm as 2, the desired color can be displayed with sufficient color purity, the viewing angle can be widened, and the temperature can be displayed only by providing one retardation plate 22. Since the change in color is small, the reduction in light transmittance due to the provision of the retardation plate 22 is slight, and high quality color display can be obtained with sufficient brightness.

That is, the birefringence effect of the retardation plate 22 in the color liquid crystal display device can be obtained by using a plurality of retardation plates each having a relatively small retardation value. When the retardation plate is used, the light transmittance is reduced by the increase of the retardation plate.

Therefore, in this color liquid crystal display device, only one retardation plate 22 having a large retardation value is used to minimize the decrease in transmittance due to the provision of the retardation plate. By doing so, it is possible to sufficiently exert the effect of obtaining a bright color display by coloring light by utilizing the birefringence effect and the polarization effect.

Further, when a plurality of retardation plates are used, the retardation of each retardation plate and the direction of its optical axis are involved as parameters for determining the characteristics of the liquid crystal display device. Is a constraint in designing the liquid crystal display device, and the manufacturing cost is increased due to the increase of the retardation plate. However, if there is only one retardation plate, there are restrictions in designing the liquid crystal display device. The cost can be eased to facilitate the design, and the manufacturing cost can be reduced.

In the first embodiment, the liquid crystal cell 1
The value of Δnd of 0 was 1408 nm and the value of retardation of the retardation plate 22 was 1557 nm, but the twist angle of the liquid crystal molecules of the liquid crystal cell 10 was 250 ° ± 20 °, and the transmission axes of the front and back polarizing plates 20 and 21 were When the directions of 20a and 21a and the slow axis 22a of the retardation plate 22 are in the directions shown in FIG. 2, the value of Δnd of the liquid crystal cell 10 is 1300n.
If the retardation value of the retardation plate 22 is in the range of 1450 nm to 1650 nm in the range of m to 1500 nm, the above-described effects can be obtained.

Further, the value of Δnd of the liquid crystal cell 10 and the retardation value of the retardation plate 22 are within the above range (Δnd = 1.
300 nm-1500 nm, retardation = 1450
The value of Δnd of the liquid crystal cell 10 is in the range of 1300 nm to 1750 nm (the twist angle of the liquid crystal molecules is 250 ° ± 20 °), and the retardation value of the retardation plate 22 is 1450 nm.
If the orientations of the transmission axes 20a and 21a of the front and back polarizing plates 20 and 21 and the orientations of the slow axis 22a of the retardation plate 22 are appropriately set in the range of ˜1850 nm, the first The same effect as that of the embodiment can be obtained.

FIG. 4 shows a second embodiment of the present invention.
3 is a view of the liquid crystal molecule alignment direction in the vicinity of both substrates 11 and 12 of the liquid crystal cell 10 and the optical axis directions of the polarizing plates 20 and 21 and the retardation plate 22 as viewed from the surface side of the liquid crystal display device. FIG.

The color liquid crystal display element of this embodiment is also of a reflective type, and as shown in FIG.
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 one retardation plate 22 arranged between the front side polarizing plate 20 and the liquid crystal cell 10, and a reflecting plate 23 arranged on the back side of the back side polarizing plate 21.

In this embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 °, and the front and back polarizing plates 20 and 21 are arranged with their transmission axes 20a and 21a oriented as follows. , The retardation plate 22 to the slow axis 22
The a is arranged in the following direction.

In this embodiment, the liquid crystal cell 10
Is the same as that in the first embodiment, and the retardation plate 22 is also the same as the uniaxial retardation plate used in the first embodiment (the refractive index n _x in the stretching direction and the orthogonal to the stretching direction. Since the refractive index n _y in the direction of doing so has a relationship of n _x > n _y ), the description thereof will be omitted.

As shown in FIG. 4, assuming that the liquid crystal molecule orientation direction 11a in the vicinity of the back surface side substrate 11 of the liquid crystal cell 10 is 0 °, in this embodiment, the transmission axis 20a of the front side polarizing plate 20 is set to the front side. Seen from the above, the liquid crystal molecule 10 has a direction of 70 ° ± 15 ° (preferably 70 ° ± 5 °, more preferably 70 °) in a direction opposite to the twist direction of the liquid crystal molecules (the twist direction viewed from the surface side), The transmission axis 21a of the back-side polarizing plate 21 is oriented at 45 ° ± 15 ° (preferably 45 ° ± 5 °, more preferably 45 °) in the same direction as the liquid crystal molecule twist direction when viewed from the surface side, and the phase difference is The slow axis 22a of the plate 22 is 20 ° ± 15 ° in a direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side with respect to the 0 ° direction.
The direction is (preferably 20 ° ± 5 °, more preferably 20 °).

In this embodiment, the liquid crystal cell 1 described above is used.
0, the refractive index anisotropy Δn of the liquid crystal 18 is 0.219,
The liquid crystal layer thickness d is 6.8 μm, and the value of Δnd is 1489 nm.
The retardation plate 22 having a retardation value of 1610 nm is used.

Also in the color liquid crystal display device of this embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ±.
And the value of Δnd of the liquid crystal cell 10 is set to 20 °.
Since the retardation value of the retardation plate 22 is set to 89 nm and the retardation value of the retardation plate 22 is increased to 1610 nm, the back side polarizing plate 21 receives the birefringence action of the retardation plate 22 and the birefringence action of the liquid crystal layer of the liquid crystal cell 10. The polarization state of the incident light is
Since the color greatly changes according to the voltage applied to the liquid crystal cell 10, a desired color can be displayed with sufficiently high color purity.

Further, as in this embodiment, the liquid crystal cell 10 is
The liquid crystal molecule has a twist angle of 250 ° ± 20 °, the liquid crystal cell 10 has a Δnd value of 1489 nm, the retardation plate 22 has a retardation value of 1610 nm, and the transmission axes 20a and 21a of the front and back polarizing plates 20 and 21 are When the orientation and the orientation of the slow axis 22a of the retardation plate 22 are set to the orientation shown in FIG. 4, the color that can be displayed by one pixel is an achromatic bright display when the incident light is white light. It becomes white and the three primary colors of light are red, green, and blue.

In the second embodiment, the liquid crystal cell 1
Although the value of Δnd of 0 was 1489 nm and the value of retardation of the retardation plate 22 was 1610 nm, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 was 250 ° ± 20 °, and the transmission axes of the front and back polarizing plates 20 and 21 were When the directions of 20a and 21a and the slow axis 22a of the retardation plate 22 are in the directions shown in FIG. 4, the value of Δnd of the liquid crystal cell 10 is 1400n.
If the retardation value of the retardation plate 22 is in the range of 1500 nm to 1700 nm in the range of m to 1600 nm, the effects described above can be obtained.

FIG. 5 shows a third embodiment of the present invention.
3 is a view of the liquid crystal molecule alignment direction in the vicinity of both substrates 11 and 12 of the liquid crystal cell 10 and the optical axis directions of the polarizing plates 20 and 21 and the retardation plate 22 as viewed from the surface side of the liquid crystal display device. FIG.

The color liquid crystal display element of this embodiment is also of a reflective type, and as shown in FIG.
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 one retardation plate 22 arranged between the front side polarizing plate 20 and the liquid crystal cell 10, and a reflecting plate 23 arranged on the back side of the back side polarizing plate 21.

In this embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ± 20 °, and the front and back polarizing plates 20 and 21 are arranged with their transmission axes 20a and 21a oriented as follows. , The retardation plate 22 to the slow axis 22
The a is arranged in the following direction.

In this embodiment, the liquid crystal cell 10
Is the same as that in the first embodiment, and the retardation plate 22 is also the same as the uniaxial retardation plate used in the first embodiment (the refractive index n _x in the stretching direction and the orthogonal to the stretching direction. Since the refractive index n _y in the direction of doing so has a relationship of n _x > n _y ), the description thereof will be omitted.

As shown in FIG. 5, assuming that the liquid crystal molecule orientation direction 11a near the rear substrate 11 of the liquid crystal cell 10 is 0 °, in this embodiment, the transmission axis 20a of the front polarizing plate 20 is set to the front side. Seen from the above, the liquid crystal molecule 10 has a direction of 65 ° ± 15 ° (preferably 65 ° ± 5 °, more preferably 65 °) in a direction opposite to the twist direction of the liquid crystal molecules (the twist direction viewed from the surface side), The transmission axis 21a of the back side polarizing plate 21 is oriented 55 ° ± 15 ° (preferably 55 ° ± 5 °, more preferably 55 °) in the same direction as the liquid crystal molecule twist direction when viewed from the front side, and the phase difference is The slow axis 22a of the plate 22 is 20 ° ± 15 ° in a direction opposite to the twist direction of the liquid crystal molecules when viewed from the surface side with respect to the 0 ° direction.
The direction is (preferably 20 ° ± 5 °, more preferably 20 °).

In this embodiment, the liquid crystal cell 1 described above is used.
0, the refractive index anisotropy Δn of the liquid crystal 18 is 0.240,
The liquid crystal layer thickness d is 6.8 μm, and the value of Δnd is 1632 nm.
And the retardation plate 22 having a retardation value of 1750 nm.

Also in the color liquid crystal display device of this embodiment, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 250 ° ±.
And the value of Δnd of the liquid crystal cell 10 was set to 20 °.
Since the retardation value of the retardation plate 22 is set to 32 nm and the retardation value of the retardation plate 22 is increased to 1750 nm, the back side polarizing plate 21 receives the birefringence action of the retardation plate 22 and the birefringence action of the liquid crystal layer of the liquid crystal cell 10. The polarization state of the incident light is
Since the color greatly changes according to the voltage applied to the liquid crystal cell 10, a desired color can be displayed with sufficiently high color purity.

Further, as in this embodiment, the liquid crystal cell 10
The liquid crystal molecule has a twist angle of 250 ° ± 20 °, the liquid crystal cell 10 has a Δnd value of 1632 nm, the retardation plate 22 has a retardation value of 1750 nm, and the transmission axes 20a and 21a of the front and back polarizing plates 20 and 21 are When the direction and the direction of the slow axis 22a of the retardation plate 22 are set to the directions shown in FIG. 5, the color that can be displayed by one pixel is a bright display of achromatic color when the incident light is white light. It becomes white and the three primary colors of light are red, green, and blue.

In the third embodiment, the liquid crystal cell 1
Although the value of Δnd of 0 was 1632 nm and the value of retardation of the retardation plate 22 was 1750 nm, the twist angles of the liquid crystal molecules of the liquid crystal cell 10 were 250 ° ± 20 °, and the transmission axes of the front and back polarizing plates 20 and 21 were When the directions of 20a and 21a and the slow axis 22a of the retardation plate 22 are in the directions shown in FIG. 5, the value of Δnd of the liquid crystal cell 10 is 1550n.
If the retardation value of the retardation plate 22 is in the range of 1650 nm to 1850 nm in the range of m to 1750 nm, the above-described effects can be obtained.

In the first to third embodiments, the uniaxial retardation plate is used as the retardation plate 22, but the retardation plate 22 may be a biaxial retardation plate. Also,
The retardation value of the biaxial retardation plate may be the same as the retardation of the uniaxial retardation plate used in each of the above examples, and the twist angle and the value of Δnd of the liquid crystal molecules of the liquid crystal cell 10 are also the above values. It may be the same as the embodiment.

Thus, even when the retardation plate 22 of the color liquid crystal display device is a biaxial retardation plate, the liquid crystal cell 1
The liquid crystal molecule twist angle of 0 is 250 ° ± 20 °, the Δnd value of the liquid crystal cell 10 is 1300 nm to 1750 nm, and the retardation value of the retardation plate 22 is 1450 nm to 185.
In the range of 0 nm, the directions of the transmission axes 20a and 21a of the front and back polarizing plates 20 and 21 and the slow axis 2 of the retardation plate 22 are set.
If the direction of 2a is set to one of the directions of FIG. 2, FIG. 4, and FIG. 5, the color that can be displayed by one pixel is white when the incident light is white light and is achromatic bright display. , The three primary colors of light are red, green and blue.

That is, for example, when the Δnd value of the liquid crystal cell 10 is in the range of 1300 nm to 1500 nm and the retardation value of the retardation plate 22 is in the range of 1450 nm to 1650 nm, the front side and the back side are the same as in the first embodiment described above. If the directions of the transmission axes 20a and 21a of the polarizing plates 20 and 21 and the direction of the slow axis 22a of the retardation plate 22 are set to the directions shown in FIG. 2, one pixel is divided into three primary colors of white, red, green and blue. Can be displayed.

Further, the value of Δnd of the liquid crystal cell 10 is set to 140
0 nm to 1600 nm, when the retardation value of the retardation plate 22 is in the range of 1500 nm to 1700 nm,
As in the second embodiment described above, the orientation of the transmission axes 20a and 21a of the front and back polarizing plates 20 and 21 and the retardation plate 2
If the direction of the second slow axis 22a is set to the direction of FIG. 4, one pixel can display white and the three primary colors of red, green, and blue.

Further, the value of Δnd of the liquid crystal cell 10 is set to 15
When the retardation value of the retardation film 22 is set to 50 nm to 1750 nm and 1650 nm to 1850 nm, the directions of the transmission axes 20a and 21a of the front and back polarizing plates 20 and 21 are the same as those in the third embodiment. If the slow axis 22a of the phase plate 22 is oriented in the direction shown in FIG.
One pixel can display white and the three primary colors of red, green and blue.

If a biaxial retardation plate is used as the retardation plate 22 of the color liquid crystal display device, the viewing angle can be widened. In this case, as the biaxial retardation plate, a refractive index n _x in the stretching direction (slow axis direction) on the plane, and a refractive index n _{y in the} direction orthogonal to the stretching direction on the plane, The refractive index n _{z in the} thickness direction is n _x
> N _z > n _y , and (n _x −n _z ) /
Those N _z value represented by (n _x -n _y) is 0.3 to 0.7, more preferably not less to use those N _z value of 0.45 ± 0.1, the If a biaxial retardation plate satisfying such conditions is used, the viewing angle can be further widened.

In the color liquid crystal display device of the above embodiment, one pixel displays white, which is an achromatic bright display, and red, green and blue, which are the three primary colors of light. As a color which can be displayed by one pixel, the value of Δnd of the liquid crystal cell 10 is selected in the range of 1300 nm to 1750 nm, and the retardation value of the retardation plate 22 is set to 1450 nm to 185 nm.
It can be arbitrarily selected by selecting in the range of 0 nm and the orientations of the optical axes of the front and back polarizing plates 20 and 21 and the retardation plate 22.

Further, in the above embodiment, the retardation plate 22 is arranged between the liquid crystal cell 10 and the front side polarizing plate 20, but the retardation plate 22 is arranged between the liquid crystal cell 10 and the back side polarizing plate 21. You may arrange.

Further, although the color liquid crystal display device of the above-mentioned embodiment is of a reflection type in which the reflection plate 23 is provided on the back surface side, the present invention is a transmission type which uses light from a backlight for display. Can be applied to the color liquid crystal display device of
Further, the liquid crystal cell 10 is not limited to the simple matrix type, but may be the active matrix type or the segment type.

[0082]

The color liquid crystal display device of the present invention utilizes the birefringence effect of the retardation plate and the liquid crystal layer of the liquid crystal cell and the polarization effect of the polarizing plate to obtain a colored display without using a color filter. Therefore, it is possible to obtain a bright color display and display a plurality of colors in the same pixel by controlling the voltage applied to the liquid crystal cell.

In this color liquid crystal display device, the twist angle of the liquid crystal molecules of the liquid crystal cell is 250 ° ±.
And the value of Δnd of this liquid crystal cell is 1300.
nm to 1750 nm and the retardation value of the retardation plate is set to a large value of 1450 nm to 1850 nm, so that the other polarized light receives the birefringence action of the retardation plate and the birefringence action of the liquid crystal layer of the liquid crystal cell. Since the polarization state of the light incident on the plate largely changes according to the voltage applied to the liquid crystal cell, a desired color can be displayed with sufficiently high color purity.

Further, in the color liquid crystal display device of the present invention, the phase difference between the time when light is vertically transmitted through the liquid crystal layer of the liquid crystal cell and the time when the light is obliquely transmitted is compensated by the retardation plate, so that the viewing angle is reduced. Becomes wider.

Moreover, in the retardation plate, since the change in birefringence due to the change in temperature is considerably smaller than the change in birefringence of the liquid crystal layer of the liquid crystal cell, the liquid crystal layer of the liquid crystal cell and the retardation plate are different from each other. The temperature dependence of the total birefringence is reduced, and therefore the change in display color due to temperature is also reduced.

According to this color liquid crystal display device, the value of Δnd of the liquid crystal cell is set to 1300 nm to 1750 n.
and a retardation value of 1450 as a retardation plate.
By using as large as nm to 1850 nm,
Since the desired color can be displayed with sufficient color purity and the viewing angle can be widened and the change in the display color due to temperature can be reduced by providing only one retardation plate, the provision of the retardation plate The decrease in light transmittance is slight, and high quality color display can be obtained with sufficient brightness.

The retardation plate may be a normal uniaxial retardation plate or a biaxial retardation plate having a retardation in the thickness direction. If a biaxial retardation plate is used, the viewing angle can be widened.

When a biaxial retardation plate is used as the retardation plate, the biaxial retardation plate has a refractive index n _x in the stretching direction on the plane and the stretching direction on the plane. the refractive index n _y in orthogonal directions and the refractive index n _z in the thickness direction is in the relation of n _x> n _z> n _y in, _{and, (n x -n z) /} (n x -n y ), The N _z value is 0.3 to 0.7, and more preferably the N _z value is 0.45 ±.
If the value of 0.1 is used, the viewing angle can be further widened.

[Brief description of drawings]

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

FIG. 2 is a view of the alignment direction of liquid crystal molecules in the vicinity of both substrates of the liquid crystal cell and the orientations of the optical axes of each polarizing plate and the retardation plate as viewed from the surface side of the liquid crystal display device.

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

FIG. 4 shows a second embodiment of the present invention, in which the alignment direction of liquid crystal molecules in the vicinity of both substrates of a liquid crystal cell and the orientations of optical axes of respective polarizing plates and retardation plates are viewed from the surface side of the liquid crystal display device. Fig.

FIG. 5 shows a third embodiment of the present invention, in which the alignment direction of liquid crystal molecules in the vicinity of both substrates of a liquid crystal cell and the optical axes of the respective polarizing plates and retardation plates are viewed from the front side of the liquid crystal display device. Fig.

[Explanation of symbols]

 Reference Signs List 10: liquid crystal cell 11a: liquid crystal molecule alignment direction near the rear substrate 12a: liquid crystal molecule alignment direction near the front substrate 20: front polarizing plate 20a: transmission axis 21: rear polarizing plate 21a: transmission axis 22: phase difference Plate 22a: Slow axis 23: 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 an inner surface thereof, a pair of polarizing plates disposed between the liquid crystal cells, and A liquid crystal cell; and a retardation plate disposed between the liquid crystal cell and the liquid crystal cell.
°, product of refractive index anisotropy Δn of liquid crystal and liquid crystal layer thickness d Δnd
Of 1300 nm to 1750 nm, the retardation value of the retardation plate is 1450 nm to 1850 nm, and the directions of the optical axes of the pair of polarizing plates and the retardation plate and in the vicinity of both substrates of the liquid crystal cell. The linearly polarized light that has passed through the polarizing plate and is incident on the alignment direction of the liquid crystal molecules is
During transmission through the retardation plate and the liquid crystal cell, each wavelength light becomes elliptically polarized light having a different polarization state due to the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer of the liquid crystal cell. A color liquid crystal display device wherein the elliptically polarized light is further transmitted through a polarizing plate, and the ratio of the light intensity of each wavelength light is set to a desired ratio. 2. The color liquid crystal display device according to claim 1, wherein a reflection plate is disposed on an outer surface of one of the polarizing plates. 3. The retardation plate has a relationship in which the refractive index n _x in the stretching direction on the plane and the refractive index n _{y in the} direction orthogonal to the stretching direction on the plane are n _x > n _y. The color liquid crystal display device according to claim 1 or 2, which is a uniaxial retardation plate. 4. A retardation plate has a refractive index n _x in the stretching direction on the plane, a refractive index n _{y in the} direction orthogonal to the stretching direction on the plane, and a refractive index n _{z in the} thickness direction. Is a biaxial retardation plate having a relationship of n _x > n _z > n _y . 3. The color liquid crystal display device according to claim 1, wherein 5. A biaxial retardation plate is (n _x −n _z ) / (n
color liquid crystal display device according to claim 4, N _z value represented by _x -n _y) is characterized in that 0.3 to 0.7.