JPH11153791A - Color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a transmission type color display using a backlight and bright reflection type color display. SOLUTION: A liquid crystal cell 10 is constructed by enclosing nematic liquid crystal 6 between a pair of glass substrates 1, 2 having each transparent electrode 3, 4 on inner surfaces facing each other, and a twisted phase plate 12 is arranged on the viewing side of the liquid crystal cell 10 as a double refraction layer, and an absorption type polarizing plate 11 is arranged outside thereof. Moreover, on the viewing side of the liquid crystal cell 10 and on the opposite side thereof, a reflection type polarizing plate 13, a semi-transmissive absorption plate 14, and a backlight 15 are successively arranged.

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, and more particularly to a color liquid crystal display device using birefringence which can change a display color by an applied voltage without using a color filter.

[0002]

2. Description of the Related Art In general, a liquid crystal display device comprises a liquid crystal cell in which a liquid crystal oriented between two opposing glass substrates is sealed, and an electrode pattern is formed on each of the two glass substrates. By applying a voltage to the liquid crystal layer between the electrodes, display is performed by moving the liquid crystal molecules.

In a general color liquid crystal display device that performs color display in such a liquid crystal display device, each pixel of the liquid crystal display device is used as an optical shutter, and one pixel is provided with red (R) and green pixels, respectively. One unit of color is displayed by a set of three pixels to which (G) and blue (B) color filters are added.

A problem in this case is that, for example, when displaying red as a display color, only a pixel to which a red color filter is added among a set of three pixels is displayed, and other green and blue colors are set. The pixels of the filter must be shielded from light, and in principle, the utilization efficiency of incident light is reduced to 1/3. Therefore, when used as a transmissive display device using a backlight, there is no major problem.However, when used as a reflective display device using external light, a sufficient amount of light cannot be obtained. Lack of brightness,
The performance as a display device will be remarkably insufficient.

As a means for solving this problem, the coloring state of one pixel itself is changed by utilizing the fact that the color changes continuously according to the applied voltage based on the birefringence effect of the liquid crystal cell. There has been proposed a birefringent color liquid crystal display device which enables color display without using a color filter.

Particularly recently, for example, Japanese Patent Application Laid-Open No. 9-5072
As shown in the publication, by adding a retardation plate as well as a single liquid crystal cell, by combining the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer,
Devices that perform color display more effectively have been proposed.

According to this method, since a color display is performed by changing a spectral characteristic of one pixel itself, that is, a coloring state, a color filter which requires three pixels to express one color is used. In principle, the light use efficiency is three times higher than that of the display device, and sufficient brightness can be obtained even when used as a reflective display device.

[0008] Therefore, colorful color display can be realized with a relatively low-cost and simple configuration, and application to a display unit of a portable information device such as a game machine, a digital clock, or a mobile phone can be considered.

[0009]

The above-described birefringent color liquid crystal display device can be said to be a very good display device when used as a reflective color liquid crystal display device in a situation where ambient light is sufficiently bright. However, in order to obtain sufficient visibility in a situation where ambient light is dark, such as at night, illumination by a backlight is usually required. However, the conventional birefringence type color liquid crystal display device uses a reflection plate, so that backlight light is blocked and cannot be used as a transmission type.

Therefore, in order to make the backlight usable, a semi-transmissive reflector that transmits incident light at a certain transmittance, instead of a perfect reflector, is used. Become. However, in this case, the transmittance of the semi-transmissive reflector is 30 to 50%, and the reflectance is reduced by that much, and the brightness is reduced when used as a reflection type.

Therefore, the present invention provides a sufficiently bright display even when a birefringence type color liquid crystal display device is used as a reflection type display device, and can be used as a transmission type display device using a backlight. The first thing to do
The purpose of.

In the color liquid crystal display device described in Japanese Patent Application Laid-Open No. 9-5072, the arrangement relationship between the polarizing plate and the liquid crystal molecules of the liquid crystal cell is such that the birefringence effect is maximized, that is, The polarizer is arranged so that the angle between the optical axis (easy transmission axis or absorption axis) of the polarizing plate and the direction of the long axis of the liquid crystal molecules adjacent thereto is about 45 °. Δnd represented by the product of the difference Δn in birefringence of the liquid crystal layer of the liquid crystal cell and the cell gap d which is the gap between the pair of substrates.
There is not much difference between the value and the retardation value of the retardation plate. Even if there is almost the same value or the difference is within 200 nm.

However, the above configuration is not an optimum configuration as a birefringence type color liquid crystal display device, and it is difficult to make the spectral characteristics at the time of displaying each color an ideal spectral characteristic. For example, it is considerably inferior to a color liquid crystal display device using a color filter. First, there is a difference in the wavelength dependence of the Δnd value of the liquid crystal cell and the retardation value of the retardation plate. Furthermore, there is a difference in the birefringence effect depending on whether or not the liquid crystal cell and the phase difference plate are twisted.

It is a second object of the present invention to provide a birefringence type color liquid crystal display device which has better color reproduction characteristics by solving the problem that the color reproduction characteristics are deteriorated. .

[0015]

The color liquid crystal display device according to the present invention is configured as follows to achieve the first object.

That is, a liquid crystal cell in which a nematic liquid crystal is sealed between a pair of transparent substrates each having an electrode on the inner surface facing each other, a birefringent layer provided on the viewing side of the liquid crystal cell, and an outer side of the birefringent layer. And a reflective polarizing plate disposed on the side opposite to the viewing side of the liquid crystal cell. The absorption type polarizing plate is a polarizing plate that absorbs linearly polarized light having a vibration plane in a direction perpendicular to the easy transmission axis, and the reflection type polarization plate has a vibration plane in a direction perpendicular to the easy transmission axis. Linearly polarized light is a polarizing plate that reflects light.

The birefringent layer may be arranged on the side opposite to the viewing side of the liquid crystal cell, and a reflective polarizing plate may be arranged outside the birefringent layer. In these color liquid crystal display devices, it is desirable to arrange a backlight outside the reflective polarizing plate or to arrange a transflective member and a backlight in order. Alternatively, a light absorption layer may be arranged outside the reflective polarizing plate.

The liquid crystal cell has a twist angle of 180 to 2
A 70 ° super twisted nematic liquid crystal cell is preferably used. The birefringent layer has a twisted retardation plate,
Alternatively, a normal retardation plate can be used.

According to this color liquid crystal display device, when no voltage is applied to the liquid crystal cell, the light incident from the viewing side is
The light passes through the absorption type polarizing plate, the birefringent layer, and the liquid crystal cell, and reaches the reflection type polarizing plate in a substantially linearly polarized state.

Therefore, if the reflection-type polarizing plate is arranged so that the axis of easy transmission is orthogonal to the oscillation direction of the linearly-polarized light, almost all of the linearly-polarized light that reaches the reflection-type polarizing plate is reflected, and Return to In this case, since the reflected light is totally reflected, a mirror image of a silver image is displayed on the viewing side.

When a voltage is applied to the liquid crystal cell, the light that reaches the reflective polarizer becomes elliptically polarized light. The polarization state of the elliptically polarized light differs depending on the applied voltage value. Therefore, by changing the voltage value, the component of light reflected on the incident side, that is, the color tone can be changed. Therefore, the background portion of the liquid crystal cell where no voltage is applied is a very bright silver metallic display, and the electrode portion to which the voltage is applied is colored, and furthermore, the display can be made with reflected light having a different color tone depending on the applied voltage. The device can be realized.

When a backlight is used, the reflection type polarizing plate has a function of transmitting half of the incident light from the backlight to the liquid crystal cell side in principle, so that it functions as a transmission type color liquid crystal display device. Can be. The transmitted light color in this case has a complementary color relationship to the reflected light color.

Further, a diffusion layer may be provided between the liquid crystal cell and the reflective polarizing plate. In this case, the display state is no longer metallic, and the display is similar to that of a conventional reflection type liquid crystal display device combining a transmission type polarizing plate and a diffuse reflection plate.
Since the reflectivity of the reflective polarizer is much higher than that of the combination of the transmissive polarizer and the diffuse reflector, it is possible to realize a color liquid crystal display capable of displaying much brighter than a conventional reflective liquid crystal display.

As described above, a very bright reflective color display and a transmissive color display using a backlight can be performed without using a reflector, and the display color is a complementary color in reflection and transmission. That is, it is possible to provide a color liquid crystal display device having a feature not found in the related art.

Further, in the color liquid crystal display device according to the present invention, in order to achieve the second object, the liquid crystal cell is a super twisted nematic liquid crystal cell having a twist angle of 180 to 270 °, and the birefringent layer is formed. It is composed of one or a plurality of retardation plates, and the sum of the retardations of the retardation plates is set to be greater than the Δnd value of the liquid crystal cell by 250.
And the angle between the axis of easy transmission of the reflective polarizing plate and the major axis direction of the liquid crystal molecules in contact with the inner surface of the substrate on the reflective polarizing plate side of the liquid crystal cell is 35 ± 5.
It is desirable to set it in the range of ゜.

As described above, the twist angle of the liquid crystal cell, the retardation value of the retardation plate, and the direction of the transmission axis of the reflective polarizer and the major axis direction of the liquid crystal molecules in contact with the inner surface of the substrate on the reflective polarizer side of the liquid crystal cell. By defining each of the ranges of angles formed by the above, a birefringent color liquid crystal display device having excellent color reproduction characteristics can be obtained.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various preferred embodiments of a color liquid crystal display device according to the present invention will be described below with reference to the drawings.

[First Embodiment: FIGS. 1 to 5] First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. FIG. 1 is a schematic cross-sectional view showing the configuration of the color liquid crystal display device, in which the size in the thickness direction is greatly enlarged. FIG. 2 is a plan view showing the arrangement of each optical axis in the configuration of FIG.

As shown in FIG. 1, the color liquid crystal display of the first embodiment has an upper glass substrate 1 on which a first transparent electrode 3 is formed and a lower glass substrate 1 on which a second transparent electrode 4 is formed. The side glass substrate 2 is adhered via the sealing material 5, and a twist angle of 240
The super twisted nematic (STN) type liquid crystal cell 10 is constituted by enclosing and holding the nematic liquid crystal 6 twisted in ゜. The transparent electrodes 3 and 4 are formed of indium tin oxide (ITO).

Then, a twisted phase difference plate 12 as a birefringent layer is arranged above the upper glass substrate 1 of the liquid crystal cell 10, that is, on the viewing side, and an absorption type polarizing plate 11 is arranged outside thereof. Further, a reflective polarizer 13 is disposed below the lower glass substrate 2 of the liquid crystal cell 10, that is, on the side opposite to the viewing side, and further on the outside thereof (the lower side in FIG. 1), which is a semi-transmissive absorbing member. The transmission absorption plate 14 and the backlight 15 are sequentially arranged.

Here, the absorption-type polarizing plate 11 has a function of transmitting linearly polarized light having a vibration plane in a direction parallel to the easy transmission axis and absorbing immediately preceding polarization having a vibration plane in a direction perpendicular to the easy transmission axis. Polarizing plate (sheet). Reflective polarizing plate 13
Is a polarizing plate having a function of transmitting linearly polarized light having a vibration plane in a direction parallel to the easy transmission axis and reflecting linearly polarized light having a vibration plane in a direction perpendicular to the easy transmission axis. The transflective plate 14 is provided on the back surface of the liquid crystal cell 10 or the reflective polarizing plate 13.
A sheet made of a translucent absorbing material may be attached to the upper surface of the substrate, or a translucent absorbing layer may be formed by applying a translucent absorbing material.

Next, the arrangement angle of each element and the angle of the optical axis will be described with reference to FIG. As a reference of the angle, the direction of 3 o'clock at the time of the clock when the liquid crystal display device (panel) is viewed from above is set as the reference axis 21 and the angle is set to 0 °.

In the liquid crystal cell 10, the upper glass substrate 1
The upper liquid crystal alignment direction 6 a on the inner surface of the lower glass substrate 2 forms an angle of 30 ° clockwise with respect to the reference axis 21.
Make an angle of 30 ° counterclockwise with respect to. The twist angle of the liquid crystal molecules from the upper liquid crystal alignment direction 6a toward the lower liquid crystal alignment direction 6b is 240 ° counterclockwise.

The torsional retarder 12 is arranged such that its lower slow axis (molecular orientation direction) 12b is orthogonal to the upper liquid crystal orientation direction 6a of the liquid crystal cell 10. That is, the lower slow axis 12 b of the torsional retarder 12 forms an angle of 60 ° counterclockwise with respect to the reference axis 21, and the upper slow axis (molecular orientation direction) 12 a with respect to the reference axis 21. 6 clockwise
Make an angle of 0 °.

Therefore, the twist angle of the molecule from the upper slow axis 12a to the lower slow axis 12b of the torsional retarder 12 is 240 ° clockwise. That is, the upper slow axis 12a and the lower slow axis 12b of the torsional retarder 12
Is about 240 °, which is almost the same as the twist angle of the liquid crystal cell 10, but the twist direction is reversed.

The easy transmission axis 11 a of the absorption type polarizing plate 11 on the upper side of the liquid crystal cell 10 is arranged at an angle of 45 ° with respect to the upper slow axis 12 a of the torsional retardation plate 12. That is, the easy transmission axis 11a forms an angle of 75 ° counterclockwise with respect to the reference axis 21. The easy transmission axis 13a of the reflective polarizer 13 on the lower side of the liquid crystal cell 10 is arranged to be orthogonal to the easy transmission axis 11a of the absorption polarizer 11. That is,
The easy transmission axis 13a makes an angle of 15 ° clockwise with respect to the reference axis 21.

The display principle of this liquid crystal display device is shown in FIG.
This will be described with reference to FIG. First, the case (a) on the left side in FIG. 3 when no voltage is applied will be described. When natural light having a random polarization direction is incident from the viewing side (upper side in the figure) and passes through the absorption type polarizing plate 11, the polarization component in the direction orthogonal to the easy transmission axis 11a, that is, the absorption axis direction is absorbed, and the polarized light is absorbed. The component becomes linearly polarized light parallel to the easy transmission axis 11a.

When the linearly polarized incident light passes through the torsional retardation plate 12, the linearly polarized light changes to elliptically polarized light due to the birefringence effect. The elliptically polarized light is incident on the liquid crystal cell 10. When no voltage is applied between the transparent electrodes 3 and 4 of the liquid crystal cell 10, the twist phase difference plate 12 and the liquid crystal cell 10 have the same Δnd, and the twist direction Are opposite and shifted by 90 °, the sum of the birefringence effects becomes almost zero.

Therefore, the elliptically polarized light is returned to its original state when passing through the liquid crystal cell 10, and the light emitted from the liquid crystal cell 10
The linearly polarized light after passing through the absorption polarizer 11 becomes the same linearly polarized light as the vibration direction. Here, since the easy transmission axis 13a of the reflection type polarizing plate 13 is arranged perpendicular to the easy transmission axis 11a of the absorption type polarizing plate 11 (at a crossing angle of 90 °), the light enters the reflection type polarizing plate 13. The component passing through the linearly polarized light is zero, and all components are reflected and returned to the viewing side.

Since the reflection by the reflection type polarizing plate 13 is reflected on the entire surface, the mirror-like silver metallic looks to the observer on the viewing side. Therefore, even if a reflector is not provided, about half of the incident light from the viewing side, that is, most of the light passing through the absorbing polarizer 11 is reflected back, and is very bright and silver metallic. Characteristic display can be obtained.

Next, the case (b) on the right side in FIG. 3 when a voltage is applied will be described. Until approximately half of the incident light due to natural light from the viewing side passes through the torsional retardation plate 12 and becomes elliptically polarized light, and enters the liquid crystal cell 10 in the same manner as when no voltage is applied.

When a voltage is applied between the first transparent electrode 3 and the second transparent electrode 4 of the liquid crystal cell 10 shown in FIG. 1 and an electric field is applied to the nematic liquid crystal 6, the liquid crystal molecules rise. The Δnd value of the liquid crystal cell 10 represented by the product of the birefringence difference Δn and the cell gap d which is the gap between the electrodes 3 and 4 decreases. Therefore, the birefringence effect of the liquid crystal cell 10 is smaller than the birefringence effect of the torsional retardation plate 12, and the liquid crystal cell 1
The elliptically polarized light incident on 0 changes its polarization state but does not return to the original linearly polarized light.
Incident on. The polarization state at that time changes depending on the value of the voltage applied to the liquid crystal cell 10.

Here, of the elliptically polarized light incident on the reflective polarizing plate 13, a component parallel to the easy transmission axis 13a is transmitted. Then, half of the transmitted light is absorbed by the semi-transmissive absorption plate 14 shown in FIG. 1 disposed below the reflection type polarizing plate 13, and the other half passes through it to reach the backlight 15.

A component orthogonal to the easy-to-transmit axis 13a of the reflective polarizer 13 of the incident elliptically polarized light is reflected,
It is returned to the viewing side. The wavelength band of the reflected light differs depending on the polarization state of the elliptically polarized light incident on the reflective polarizer 13. Therefore, if the voltage applied to the liquid crystal cell 10 is controlled to change the polarization state of the elliptically polarized light, the wavelength band of the reflected light, that is, the coloring state can be changed. That is, one pixel can obtain reflected light of a plurality of colors that continuously change. Therefore, information such as characters and figures can be displayed in various colors in a silver metallic background by reflection by natural light.

Next, a case of displaying by using the backlight 15 will be described. This color liquid crystal display device
When no voltage is applied, half of the incident light is reflected in principle, so that the light is very bright. In a normal lighting environment, backlight light is not required. However, in order to obtain visibility when the surrounding environment is dark, such as in a non-illuminated state at night, backlight light is required.

Here, when the backlight 15 is turned on, a component of the backlight light parallel to the easy-to-transmit axis 13a of the reflective polarizing plate 13 is transmitted to the viewing side, and is orthogonal to the easy-to-transmit axis 13a. The component is reflected and returned to the backlight 15 side. In this case, the components of the transmitted light to the viewing side are the same as those described with reference to FIG.
And the same component as the light that is transmitted through and absorbed by the semi-transmissive absorption plate 14. This is the light reflected by the reflective polarizer 13,
The components have orthogonal polarization states, and when viewed in terms of color tone, have a relationship between the color of the reflected light and the complementary color. For example, transmitted light is black for a silver metallic tone, which is a reflected color when no voltage is applied, and transmitted light is cyan for a red reflected color on the display unit.

Hereinafter, specific examples will be described. When the birefringence difference Δn of the nematic liquid crystal is 0.2 and the cell gap d is 8
μm, the Δnd value of the liquid crystal cell 10 was set to 1600 nm. Twisted phase difference plate 12 which is a birefringent layer
Used was 240 ° clockwise with a Δnd value of 1600 nm. That is, the Δnd value of the liquid crystal cell is equal to the Δnd value of the twisted phase difference plate. As the reflective polarizing plate 13,
An optical film DBEF (trade name) sold by Sumitomo 3M Limited was used.

The liquid crystal cell 10, the twisted phase difference plate 12,
In the color liquid crystal display device shown in FIG. 1 using the reflective polarizer 13 and the liquid crystal cell 10, when no voltage is applied to the liquid crystal cell 10, the light that has passed through the absorption polarizer 11 passes through the twisted retarder 12 and the liquid crystal. After passing through the cell 10, the vibrating surface enters the reflective polarizing plate 13 in a linearly polarized state in a direction orthogonal to the easy transmission axis 13 a of the reflective polarizing plate 13. And
Since most of the light was reflected by the reflective polarizing plate 13 and returned to the viewing side, a silver metallic display almost in a mirror state was obtained.

Next, the first transparent electrode 3 of the liquid crystal cell 10
When a voltage was applied between the first transparent electrode 4 and the second transparent electrode 4 and the voltage was gradually increased, the light passing through the torsional phase difference plate 12 and the liquid crystal cell 10 became elliptically polarized light, and the electrode portion was as shown in FIG. The chromaticity locus 40 shown in the CIE1931 chromaticity diagram of FIG. 19 shows a reflection color that becomes a locus of → black → blue → green → yellow → pink as the applied voltage increases from the silver metallic display of the initial stage 41.

Therefore, the liquid crystal display device of this embodiment is
Even without using a reflector, a multi-color display in which a colorful reflection color continuously changes can be performed on a bright background of silver metallic, and a very characteristic display can be realized.

The case where the backlight 15 below the semi-transmissive absorbing plate 14 is turned on in a state where the ambient light is weak and dark will be described. This color liquid crystal display device has a backlight 1
In the case where light is turned on to cause light to enter the viewing side through the reflective polarizing plate 13, a component of the backlight light parallel to the easy transmission axis 13 a of the reflective polarizing plate 13 is transmitted and enters the liquid crystal cell 10. Then, the component orthogonal to the easy transmission axis 13a is reflected and returned to the backlight 15 side.

Therefore, when the light transmitted by the backlight 15 is used, it functions as a transmission type birefringent color liquid crystal display device. When the backlight 15 is turned on, the color liquid crystal display of this embodiment
When no voltage was applied to 0, backlight light was almost blocked, and a dark state was obtained.

Next, the first transparent electrode 3 of the liquid crystal cell 10
When a voltage was applied between the first transparent electrode 4 and the second transparent electrode 4 and this voltage was gradually increased, the transmitted light of the electrode portion was changed as shown in FIG.
The chromaticity locus 50 shown in the CIE1931 chromaticity diagram of FIG.
From the dark state of No. 1, the transmitted light color showed a locus of → white → yellow → purple → blue → green as the applied voltage increased. This is the relationship between the reflected light color and the complementary color.

That is, when the backlight is used, the display of a color complementary to the reflected light color can be performed at the same applied voltage, and a characteristic display can be realized. As described above, the color liquid crystal display device according to the present embodiment can be displayed as a bright reflective color liquid crystal display device without using a reflection plate by disposing the reflection type polarizing plate on the side opposite to the viewing side of the liquid crystal cell. And a sufficient display could be performed as a transmissive color liquid crystal display device using a backlight.

In the case of the reflection type display, the non-voltage-applied portion of the liquid crystal cell has a characteristic display which has not been seen in the past, such as a silver image of a mirror image.
Further, a characteristic display is obtained in which the display color is inverted in a complementary color relationship between the case of displaying the reflection type and the case of displaying the transmission type.

[Modification of First Embodiment: FIG. 6] In the above-described color liquid crystal display device of the first embodiment, as shown in FIG. Although arranged between the viewing side of 10 and the absorbing polarizer 11,
As shown in FIG. 6, a twisted phase difference plate 12 may be provided between the opposite side of the liquid crystal cell 10 on the viewing side and the reflective polarizing plate 13. Even in this case, a color display function substantially equivalent to that of the color liquid crystal display device of the first embodiment is provided.

[Second Embodiment: FIGS. 7 to 10] Next, a second embodiment of the present invention will be described with reference to FIGS.
0 will be described. FIG. 7 is a sectional view similar to FIG. 1 showing the configuration of the color liquid crystal display device, and FIG. 8 is a plan view showing the relationship between the optical axes of each element. In these figures, parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted.

In the color liquid crystal display device of the second embodiment, as shown in FIG. 7, instead of the twisted retardation plate 12 in FIG. The plate 16 is arranged between the viewing side of the liquid crystal cell 10 and the absorption type polarizing plate 11. This phase difference plate 16
Is biaxial stretching in which the refractive index nx in the stretching direction in the plane, the refractive index ny in the direction orthogonal to the stretching direction in the plane, and the refractive index nz in the thickness direction have a relationship of nx>nz> ny. Film.

Next, the arrangement angle of each element and the angle of the optical axis will be described with reference to FIG. As a reference for the angle, the direction of 3 o'clock at the time of the clock when the liquid crystal display device is viewed from above is set as a reference axis 21 and the angle is set to 0 °. In the liquid crystal cell 10, the upper liquid crystal alignment direction 6a
Makes an angle of 20 ° clockwise with respect to the reference axis 21, and the lower liquid crystal alignment direction 6b makes an angle of 20 ° counterclockwise with respect to the reference axis 21. Therefore, the twist angle of the liquid crystal molecules from the upper liquid crystal alignment direction 6a toward the lower liquid crystal alignment direction 6b is 220 ° counterclockwise.

The extension axis 16 a of the retardation plate 16 is at an angle of 65 ° counterclockwise with respect to the reference axis 21. Easy transmission axis 11a of absorption type polarizing plate 11 on the upper side of liquid crystal cell 10
Make an angle of 20 ° counterclockwise with respect to the reference axis 21. The easy transmission axis 13a of the reflective polarizer 13 on the lower side of the liquid crystal cell 10 makes an angle of 40 ° clockwise with respect to the reference axis 21.

In the first embodiment using the twisted phase difference plate as the birefringent layer, as described above, when no voltage is applied to the liquid crystal cell, the sum of the birefringence effects of the twisted phase difference plate and the liquid crystal cell is zero. Although it was set to be, even if a phase difference plate is used instead of the twisted phase difference plate, by optimizing the arrangement angle, when no voltage is applied to the liquid crystal cell,
The sum of the birefringence effects of the retardation plate and the liquid crystal layer can be made substantially zero.

The display state in this case is almost the same as the case where the twisted phase difference plate is used. That is, in the case of displaying with reflected light of external light, when no voltage is applied to the liquid crystal cell, silver metallic is displayed, and when a voltage is applied, a birefringent color is displayed as a reflected color. In the case where display is performed by transmitted light using a backlight, the display color has a relationship between the reflected color and the complementary color.

Hereinafter, specific examples will be described. Liquid crystal cell 1
0 is Δn = 0.2 of the nematic liquid crystal 6, the cell gap d = 8 μm, and the Δnd value is 1600 nm. The phase difference plate 16 is NRZ manufactured by Nitto Denko Corporation.
(Product name) having a retardation of 1770 nm was used. As the reflective polarizing plate 13, an optical film DBEF sold by Sumitomo 3M Limited is used.
(Product name) was used.

In the color liquid crystal display device of this embodiment, when no voltage is applied to the liquid crystal cell 10 shown in FIG. 7, the light passing through the absorbing polarizer 11 among the external light entering from the viewing side has a phase difference. After passing through the plate 16 and the liquid crystal cell 10, the vibrating surface enters the reflective polarizing plate 13 in a linearly polarized state in a direction orthogonal to the easy transmission axis 13 a of the reflective polarizing plate 13. Therefore, the incident light is totally reflected by the reflective polarizing plate 13 and returns to the viewing side, so that a silver metallic display having a substantially mirror surface state is obtained.

On the other hand, when a voltage was applied between the first transparent electrode 3 and the second transparent electrode 4 of the liquid crystal cell 10 and the voltage was gradually increased, the phase difference plate 16 and the liquid crystal cell 10 were The transmitted light becomes elliptically polarized light, and the electrode part is the CIE in FIG.
As shown in the 1931 chromaticity diagram, the chromaticity locus 80 shows a reflected color that becomes a locus of → black → blue → green → yellow → pink (red) from the initial 81 silver metallic display as the applied voltage increases. did. For this reason, the color liquid crystal display device of this embodiment can perform a multi-color display in which a colorful reflection color continuously changes on a bright background of silver metallic without using a reflector, and can realize a characteristic display.

Next, a case where the backlight 15 below the semi-transmissive absorbing plate 14 is turned on in a state where the ambient light is weak and dark will be described. In the color liquid crystal display device of this embodiment,
When the backlight 15 is turned on and light is incident toward the viewing side through the reflective polarizing plate 13, a component of the backlight light parallel to the easy transmission axis 13a of the reflective polarizing plate 13 is transmitted and the liquid crystal cell is The component incident on the optical axis 10 and orthogonal to the easy transmission axis 13a is reflected and returns to the backlight 15 side.

Therefore, when the light transmitted by the backlight 15 is used, it functions as a transmission type birefringent color liquid crystal display device. Then, when the backlight 15 was turned on and no voltage was applied to the liquid crystal cell 10, the backlight was almost blocked, and a dark state was obtained.

A voltage was applied between the first transparent electrode 3 and the second transparent electrode 4 of the liquid crystal cell 10 shown in FIG. 7 and the voltage was gradually increased. As shown in the CIE1931 chromaticity diagram of FIG. 10, the chromaticity locus 90 exhibits a transmitted light color that becomes a locus of white → yellow → purple → blue → green as the applied voltage increases from the initial dark state 91. did. This is the relationship between the reflected light color and the complementary color. Therefore, as in the case of the first embodiment, when the backlight is used, display can be performed in a color complementary to the reflected light color with the same applied voltage to the liquid crystal cell 10.

[Modification of Second Embodiment: FIG. 11] In the above embodiment, a biaxially stretched film was used for the retardation plate 16, but a uniaxially stretched film may be used. Further, in the color liquid crystal display device of the second embodiment, as shown in FIG. 7, a retardation plate 16 which is a birefringent layer is disposed between the viewing side of the liquid crystal cell 10 and the absorbing polarizer 11. Figure 11
As shown in (2), a retardation plate 16 of a biaxially stretched film or a uniaxially stretched film may be provided between the opposite side of the liquid crystal cell 10 on the viewing side and the reflective polarizing plate 13.

[Modification of First and Second Embodiments] In the first embodiment of the color liquid crystal display device according to the present invention described above, the twist angle of the liquid crystal cell 10 is 240 °, and in the second embodiment, the twist angle is Suppose the angle is 220 °
Although the TN type liquid crystal cell was used, the twist angle was 180 to 270.
Any STN type liquid crystal cell in the range of ° may be used.

The liquid crystal cell used in the color liquid crystal display device of the present invention is not limited to the STN type liquid crystal cell. The liquid crystal cell has a silver metallic reflection color when no voltage is applied and a display color due to birefringence when a voltage is applied. If so, a twisted nematic (TN) type liquid crystal cell having a twist angle around 90 ° may be used. Alternatively, a homogeneous liquid crystal cell having a twist angle of almost 0 ° can be used.

The transflective plate 14 may be omitted, and the upper surface of the backlight 15 may have the same function. Further, when a light source is provided in a device to which the color liquid crystal display device is mounted, the backlight 15 can be omitted. Alternatively, a light absorption layer may be provided outside the reflective polarizing plate 13. In that case, the light source is not a transmissive liquid crystal device, but all light transmitted through the reflective polarizer 13 is absorbed, so that a reflective liquid crystal display device with high contrast is obtained. If the light absorbing layer is a semi-transmissive light absorbing layer, a transmissive display is also possible.

Further, a diffusion layer may be provided between the liquid crystal cell 10 and the reflective polarizing plate 13. In this case, the display state is no longer metallic, but since the reflectivity of the reflective polarizer 13 is high, a much brighter display than a conventional reflective color liquid crystal display device can be obtained. As an example, a diffusion adhesive layer in which fine particles are dispersed in an adhesive material having a thickness of 30 μm,
What is necessary is just to apply | coat to the surface of the reflective polarizing plate 13, or just to stick a sheet with a light diffusing property to the surface of the reflective polarizing plate 13.

[Conventional color liquid crystal display device: FIGS. 17 to 19] Here, prior to the description of the third and fourth embodiments of the color liquid crystal display device according to the present invention, the conventional color liquid crystal display which is the premise thereof will be described. The display device will be described. In FIG.
FIG. 18 shows the configuration of a conventional birefringent color liquid crystal display device described in the above-mentioned Japanese Patent Application Laid-Open No. 9-5072, showing the angles of its optical axes, and the display principle thereof. The reference axis 21 of the angle in FIG. 18 is the same as in FIGS. 2 and 8.

In this conventional color liquid crystal display device, an upper glass substrate 1 and a lower glass substrate 2 are adhered to each other with a sealing material 5 interposed therebetween, and a twist liquid crystal 7 in which liquid crystal molecules are twist-aligned is sealed and sandwiched in a gap therebetween. The liquid crystal cell 20 is constituted. A retardation plate 16 is disposed on the viewing side (upper side) of the liquid crystal cell so that its slow axis 16a is at an angle of 50 ° ± 10 ° clockwise with respect to the reference axis 21. The polarizing plate 17 is disposed such that its absorption axis 17a is at an angle of 80 ° ± 10 ° clockwise with respect to the reference axis 21.

On the opposite side (lower side) of the liquid crystal cell 20 from the viewing side, a lower polarizing plate 18 is arranged so that its absorption axis 18a has an angle of 10 ° ± 10 ° clockwise with respect to the reference axis 21. Further, a reflection plate 19 is disposed below the reflection plate 19.

In this liquid crystal cell 20, the upper liquid crystal molecule orientation direction 7a forms an angle of 55 ° ± 10 ° counterclockwise with respect to the reference axis 21, and the lower liquid crystal molecule orientation direction 7b
It makes an angle of 55 ° ± 10 ° clockwise with respect to the reference axis 21. The twist angle of the liquid crystal molecules from the upper liquid crystal molecule alignment direction 7a to the lower liquid crystal molecule alignment direction 7b of the liquid crystal cell 20 is 250 ° ± 20 ° counterclockwise.

With respect to the positional relationship between the polarizing plates 17 and 18 and the liquid crystal molecules in the liquid crystal cell 20, the angle at which the birefringence effect is maximized, that is, the optical axis (easy transmission axis or absorption axis) of the polarizing plates 17 and 18 is determined. And the liquid crystal molecules adjacent thereto are arranged so that the angle between them is about 45 °.

In the case of the example shown in FIG.
The angle between the orientation direction 7b of the liquid crystal molecules in contact with the inner surface of the lower glass substrate 2 of the liquid crystal 7 in 0 and the absorption axis 18a of the lower polarizing plate 18 is set to 45 ° ± 10 °. Also,
The Δnd value of the liquid crystal cell 20 and the retardation values of the phase difference plates 17 and 18 are not so different, and are substantially the same or within 200 nm even if there is a difference.

The display principle of this color liquid crystal display device will be described. The incident light from the viewing side (upper side in FIG. 17) passes through the upper polarizer 17 and becomes linearly polarized light. Incident on. Here, the elliptically polarized light state changes further due to the birefringence effect of the liquid crystal cell 20. Liquid crystal cell 2
Since 0 can change the birefringence effect by applying a voltage, incident light passes through the lower polarizing plate 18 in different polarization states depending on the value of the applied voltage.

Therefore, by controlling the applied voltage, the spectral characteristics of the light passing through the lower polarizing plate 18 can be controlled, and light having different spectral characteristics, that is, light having a different colored state can be obtained. The colored light is reflected by the reflection plate 19 and returned to the viewing side. Therefore, a single pixel can display a plurality of colors.

FIG. 19 shows the locus on the CIE1931 chromaticity diagram of the color change when the voltage applied between the electrodes 3 and 4 of the liquid crystal cell 20 of this color liquid crystal display device is gradually increased from zero. The display color changes along the chromaticity locus 30 shown in FIG. 3, but the display color changes in the order of red → blue → green as the voltage increases from white when no voltage is applied.

However, such a configuration is not the optimum configuration as a birefringent color liquid crystal display device, and it is difficult to make the spectral characteristics at the time of displaying each color an ideal spectral characteristic. For example, the characteristics are considerably inferior to those of the color filter means. First, Δnd of the liquid crystal cell 20 and the phase difference plates 17 and 18 are caused.
Are different in the wavelength dependence of the retardation. Furthermore, there is a difference in the birefringence effect depending on whether or not the liquid crystal cell 20 and the phase difference plates 17 and 18 are twisted.

In such a birefringent color liquid crystal display device, the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal cell are combined. Among them, the birefringence effect of the liquid crystal cell is controlled by an applied voltage. Varying controls the overall birefringence effect.

At this time, the arrangement relationship between the retardation plate and the liquid crystal cell is basically such that the entire retardation is canceled. This is to reduce the birefringence effect as much as possible when no voltage is applied and to reduce the coloring of incident light. In order to obtain a desired color, a voltage is applied to increase the overall phase difference by decreasing the phase difference of the liquid crystal cell. Thereby, the incident light receives a birefringence effect according to the phase difference, and a coloring effect appears.

In the conventional birefringence type color liquid crystal display device, as described above, the retardation value (phase difference) of the retardation plate and the Δnd value of the liquid crystal cell are made substantially equal, so that the total value when no voltage is applied is obtained. The phase difference value was set to almost zero so that white when no voltage was applied was obtained.

When using a stretched film for the retardation plate,
The difference between the Δnd of the liquid crystal cell and the wavelength dependence of the retardation of the retardation plate is different. Further, since the liquid crystal cell has a twist and the retardation plate does not have a twist, the difference in the birefringence effect between the two with respect to incident light. Therefore, in order to obtain white when no voltage is applied, it is necessary to adjust the arrangement angle of the phase difference plate and the polarizing plate.

The white when no voltage is applied is achieved by setting the arrangement angle of the phase difference plate and the polarizing plate. However, when a color liquid crystal display device is intended to display some desired colors, It is not sufficient to simply set the arrangement angle of the retardation plate and the polarizing plate, and it depends on the difference between the wavelength dependence of the Δnd value of the liquid crystal cell and the retardation value of the retardation plate, and the presence or absence of twist between the liquid crystal cell and the retardation plate. Due to the difference in the birefringence effect, the color purity of the display color decreases. In particular, due to the difference in wavelength dependent characteristics,
The color purity is greatly reduced due to the mixture of a desired color and another color.

Actually, comparing the Δnd value of the liquid crystal cell and the wavelength dependence of the retardation value of the retardation plate, the Δnd value of the liquid crystal cell has a greater dependence on the wavelength.
That is, even if the Δnd value of the liquid crystal cell and the retardation value of the retardation plate are the same at the center wavelength near the wavelength λ = 550 nm, the Δnd value of the liquid crystal cell in the short wavelength region and the long wavelength region is reduced.
The value differs from the retardation value of the phase difference plate. Therefore, when displaying a desired color, the ideal spectral characteristics of the desired color are not obtained, and colors in other wavelength regions are mixed, so that the saturation is reduced.

The effect of the difference in the wavelength dependence of the Δnd value of the liquid crystal cell and the retardation value of the phase difference plate will be described with reference to FIG. In the wavelength dependence of the Δnd value of the liquid crystal cell, Δnd increases on the short wavelength side and decreases on the long wavelength side. The liquid crystal material has Δnd at wavelength λ = 550 nm of 1
When λ = 450 nm, 1.1 and λ = 650 n
It has a wavelength dependence of 0.92 at m.

Δnd at λ = 550 nm is 1500 nm
The wavelength dependence of the liquid crystal cell (solid line 25 in FIG. 16) is λ
= 450 nm, Δnd = 1650 nm, λ = 650 n
At m, Δnd = 1380 nm. That is, λ = 45
The Δnd at 0 nm is 150 nm larger than the Δnd at λ = 550 nm, and the Δnd at λ = 650 nm is
Wavelength-dependent characteristics are obtained, which are smaller by 120 nm than Δnd at λ = 550 nm.

Here, if the wavelength dependence of the retardation value of the retardation plate is the same as the wavelength dependence of the Δnd value of the liquid crystal cell, the difference between the central wavelength region of λ = 550 nm and the short and long wavelength regions is obtained. Does not occur, but in practice, the wavelength dependence of the retardation value of the retardation plate is smaller than that of the liquid crystal cell. For example, when the retardation value of the retardation plate at the wavelength λ = 550 nm is 1, the retardation value at the wavelength λ = 450 nm is 1.08, and the retardation value at the wavelength λ = 650 nm is 0.94. .

The retardation value at λ = 550 nm is 1
Wavelength dependence of a 500 nm retardation plate (broken line 2 in FIG. 16)
6) is 1620 nm for λ = 450 nm and λ = 650
In nm, it is 1410 nm. That is, λ = 450 nm
Is larger by 120 nm than the retardation value at λ = 550 nm, and λ = 650 nm.
Has a wavelength-dependent characteristic that is smaller by 90 nm than the retardation value at λ = 550 nm.

When this is compared with the above-mentioned liquid crystal cell having a Δnd value at λ = 550 nm of 1500 nm, λ = 45 nm
At 0 nm, the Δnd value of the liquid crystal cell increases by 30 nm, and at λ = 650 nm, the Δnd value of the liquid crystal cell decreases by 30 nm. Therefore, a mismatch between the Δnd value of the liquid crystal cell and the retardation value of the retardation plate occurs in the short wavelength region and the long wavelength region. Due to this inconsistency, when displaying a desired color, the ideal spectral characteristics of the desired color are not obtained, and the colors in other wavelength regions are mixed, thereby lowering the saturation.

[Third and Fourth Embodiments of the Invention: FIG. 7, FIGS. 11 to 16] The third and fourth embodiments of the present invention are similar to those of the second embodiment described above. It is also an object of the present invention to solve the problem and to obtain a color liquid crystal display device capable of displaying the above-mentioned reflective and transmissive characteristics and having good color reproducibility.

FIG. 7 or FIG. 11 shows the basic arrangement of the liquid crystal cell, the polarizing plate and the retardation plate serving as the birefringent layer in the third and fourth embodiments of the color liquid crystal display device according to the present invention. Since the configuration is the same as that of the color liquid crystal display device according to the second embodiment of the present invention, description thereof is omitted.

In the color liquid crystal display devices according to the third and fourth embodiments of the present invention, the Δnd value of the liquid crystal cell 10 and
In order to reduce the difference in consideration of the difference in the wavelength dependence of the retardation value of the retardation plate 16, the retardation value of the retardation plate 16 is set to be 250 to 250 μm smaller than the Δnd value of the liquid crystal cell 10.
It is configured to be 350 nm larger.

Here, the Δnd value of the liquid crystal cell 10 is 1500 nm as in the case of the above-described example, and the retardation value of the retardation plate 16 is 300
An example will be described in which the thickness is set to 1800 nm.
The wavelength dependence of the liquid crystal cell 10 and the phase difference plate 16 is the same as in the example shown in FIG.

In FIG. 16, the wavelength dependence of the retardation plate with a retardation value at λ = 550 nm of 1800 nm (solid line 27) is as follows: the retardation value at λ = 450 nm is 1944 nm, and the retardation value at λ = 650 nm is 1692 nm. Become. That is, the retardation value at λ = 450 nm is 14 times smaller than that at λ = 550 nm.
The retardation value at λ = 650 nm is 108 nm smaller than that at λ = 550 nm.

This is compared with the above-mentioned Δnd at λ = 550 nm.
When compared with a liquid crystal cell having a value of 1500 nm, λ = 4
At 50 nm, the Δnd value of the liquid crystal cell is larger,
The difference is 6 nm. At λ = 650 nm, the Δnd value of the liquid crystal cell is smaller, but the difference is 12 nm. This value is λ = 550 nm when compared with the retardation plate having a retardation value of 1500 nm.
= 450 nm, it is 1/5, and λ = 650 nm, it is less than half.

That is, the mismatch between the Δnd value of the liquid crystal cell and the wavelength dependence of the retardation value of the retardation plate on the short wavelength side and the long wavelength side can be sufficiently reduced, and a desired color can be displayed. In addition, colors in other wavelength regions are not mixed, the spectral characteristics are close to ideal, and reproduced colors with high color purity can be realized.

Further, in the third and fourth embodiments of the present invention, the liquid crystal cell 1 of the pair of polarizing plates 11 and 13 is provided.
The angle between the axis of easy transmission of the reflective polarizing plate 13 disposed on the side opposite to the viewing side of the liquid crystal cell 0 and the long axis direction of the liquid crystal molecules on the inner surface of the lower glass substrate 2 of the liquid crystal cell 10 is 35 ° ± 5 °.
This is because, as described above, the birefringence effect differs between the liquid crystal cell and the retardation plate depending on the presence or absence of the twist.

For example, as in the case of a correction cell, if the twist angle of the liquid crystal cell and the correction cell is the same and there is no difference in the birefringence effect, the optical axis of the polarizing plate and the long axis direction of the liquid crystal molecules on the substrate surface will not change. The angle to be formed is preferably set to around 45 ° so that the birefringence effect occurs most.However, when a stretched retardation plate is used, there is a difference in the presence or absence of twist with the liquid crystal cell.
It is not effective around 45 °.

Therefore, in the third and fourth embodiments of the present invention, the angle between the optical axis of the polarizing plate and the major axis direction of the liquid crystal molecules on the substrate surface is examined, and the lower substrate 2 of the liquid crystal cell 10 is examined.
Of the long axis of the liquid crystal molecules on the inner surface of
The best color reproducibility can be obtained by setting the angle of the easy transmission axis 3 to around 35 °.

Further, in each of the embodiments of the present invention, the twist angle of the liquid crystal cell is set to 180 to 270 °. In particular, when the twist angle is narrowed, the birefringence between the liquid crystal cell and the retardation plate due to the presence or absence of the above-mentioned twist is determined. Since the difference between the effects is reduced, the color reproducibility is improved. However, if the twist angle is too small, the steepness is reduced and it is not suitable for time-division driving. Therefore, the twist angle is desirably 180 ° or more.

Thus, the birefringence type color liquid crystal display device can be optimized, and the color reproduction range by applying a voltage can be greatly expanded as compared with the conventional birefringence type color liquid crystal display device.

Further, by using a reflective polarizing plate as a polarizing plate disposed on the side opposite to the viewing side of the liquid crystal cell,
The reflection type display by external light and the transmission type display by the backlight become possible, and the point that color display can be performed with colors having a complementary color relationship to each other, and in the reflection type display,
The point that the entire reflection part is a metallic display of a mirror image is the same as in the first and second embodiments.

[Third Embodiment: FIGS. 12 and 13] Next, a third embodiment of the color liquid crystal display device according to the present invention will be described with reference to FIGS. FIG. 12 is a plan view showing the arrangement of the optical axes of the color liquid crystal display device according to the third embodiment, and the reference axis 21 is the same as in FIGS.

The basic structure of this color liquid crystal display device is the same as that shown in FIG. 7 or FIG. Then, a retardation plate 16 is disposed above or below the upper glass substrate 1 of the liquid crystal cell 10 so that the slow axis 16a thereof is at an angle of 20 ° clockwise with respect to the reference axis 21. The absorption type polarizing plate 11 is set such that its absorption axis 11b is rotated counterclockwise by 30 ° with respect to the reference axis 21 (the easy transmission axis is 12 °).
0 °).

A reflective polarizer 13 is arranged below the lower glass substrate 2 of the liquid crystal cell 10 so that the easy transmission axis 13a is at an angle of 25 ° clockwise with respect to the reference axis 21. The transflective plate 14 and the backlight 15 are sequentially arranged on the lower side. In this liquid crystal cell 10, the orientation direction 6a of the liquid crystal molecules on the inner surface of the upper glass substrate 1
Makes an angle of 60 ° counterclockwise with respect to the reference axis 21, and the orientation direction 6 b of the liquid crystal molecules on the inner surface of the lower glass substrate 2 makes an angle of 60 ° clockwise with respect to the reference axis 21.

The twist angle of the liquid crystal molecules from the orientation direction 6a of the liquid crystal molecules on the inner surface of the upper glass substrate 1 to the orientation direction 6b of the liquid crystal molecules on the inner surface of the lower glass substrate 2 is 240 ° counterclockwise.

With the above setting, in this embodiment, of the pair of polarizing plates 11 and 13, the easy transmission axis 13 a of the reflection type polarizing plate 13 disposed below the liquid crystal cell 10 and the lower portion of the liquid crystal cell 10. The angle formed by the long axis direction 6b of the liquid crystal molecules on the inner surface of the side glass substrate 2 is 35 °, and the liquid crystal cell 10
There is an effect of minimizing the influence on the color reproducibility caused by the difference in the birefringence effect between the presence and absence of the twist of the retardation plate 16.

Hereinafter, a specific example of the third embodiment will be described. As a material of the nematic liquid crystal 6, R.D.
Using DP-60166 (trade name), Δ of liquid crystal cell 10
The nd value was set to 1470 nm. Phase plate 16
Is the refractive index nx in the stretching direction in the plane and the refractive index ny in the direction orthogonal to the stretching direction in the plane.
And an NRZ polycarbonate film manufactured by Nitto Denko having a relationship of nx>nz> ny with respect to the refractive index nz in the thickness direction and having a retardation of 1770 nm.
That is, the retardation value of the retardation plate 16 is 300 nm larger than Δnd of the liquid crystal cell.

FIG. 13 shows a chromaticity locus 31 of a display color by applying a voltage in a reflective display state of the color liquid crystal display device of the third embodiment, and a chromaticity locus 30 of the above-described conventional color liquid crystal display device. With CIE 193
This is shown in a single chromaticity diagram.

FIG. 13 shows a chromaticity change locus 31 of the color liquid crystal display device according to the third embodiment of the present invention.
Is located at approximately white chromaticity coordinates when no voltage is applied, similar to a conventional color liquid crystal display device, and as the voltage increases, red →
The chromaticity coordinates are moved in the order of blue → green, but show a wider color reproduction range as compared with the chromaticity change locus 30 of the conventional color liquid crystal display device. Is improving. In other words, in addition to the initial white, more vivid red, blue, and green than before can be displayed.

In the above example, one retardation plate is used, but a plurality of retardation plates may be used. Further, the retardation value of the retardation plate is set to be 300 times smaller than the Δnd value of the liquid crystal cell.
Although the value is increased by nm, this value can be applied without any problem if it is in the range of 250 to 350 nm.

The phase difference plate 16 is provided as shown in FIG.
As shown in the above, the liquid crystal cell 10 may be arranged on the viewing side or on the opposite side to the viewing side. The translucent absorption plate 14 is
A semi-transmissive absorbing material may be attached to the back surface of the liquid crystal cell 10 or the upper surface of the reflective polarizing plate 13, or a semi-transmissive absorbing material may be applied to form a transflective absorbing layer.

The transflective absorbing plate 14 may be omitted, and the surface of the backlight 15 may have the same function. Further, when a light source is provided in a device to which the color liquid crystal display device is mounted, the backlight 15 can be omitted. Alternatively, a light absorption layer may be provided outside the reflective polarizing plate 13. In that case, the light source is not a transmissive liquid crystal device, but all light transmitted through the reflective polarizer 13 is absorbed, so that a reflective liquid crystal display device with high contrast is obtained.

Further, a diffusion layer may be provided between the liquid crystal cell 10 and the reflective polarizing plate 13. In this case, the display state is no longer metallic, but since the reflectivity of the reflective polarizer 13 is high, a much brighter display than a conventional reflective color liquid crystal display device can be obtained. As an example, a diffusion adhesive layer in which fine particles are dispersed in an adhesive material having a thickness of 30 μm,
What is necessary is just to apply | coat to the surface of the reflective polarizing plate 13, or just to stick a sheet with a light diffusing property to the surface of the reflective polarizing plate 13.

[Fourth Embodiment: FIGS. 14 and 15] Next, a fourth embodiment of the color liquid crystal display device according to the present invention will be described with reference to FIGS. 14 and 15. FIG. FIG. 14 is a plan view showing the arrangement of the optical axes of the color liquid crystal display device of the fourth embodiment, and the reference axis 21 is the same as in FIGS.

The basic structure of this color liquid crystal display device is the same as that shown in FIG. 7 or FIG. 11, as in the third embodiment. In the above-described third embodiment, the twist angle of the liquid crystal cell 10 is set to 240 °.
The twist angle of the liquid crystal cell 10 in the embodiment is 22
It may be 0 ° or less.

In the color liquid crystal display device according to the fourth embodiment of the present invention, as shown in FIG. 14, a retardation plate 16 is provided on the viewing side of the liquid crystal cell 10 or on the opposite side thereof, and its slow axis 16a is provided.
Is disposed at an angle of 20 ° clockwise with respect to the reference axis 21. Further, the absorption type polarizing plate 11 is disposed on the viewing side thereof, and the absorption axis 11b is counterclockwise with respect to the reference axis 21 by 30 ° (easy transmission). The axis is arranged at an angle of 120 °).

Then, a reflective polarizer 13 is provided on the opposite side of the liquid crystal cell 10 from the viewing side, and its easy-to-transmit axis 13a is
1 is arranged clockwise at an angle of 35 °, and a transflective absorbing plate 14 and a backlight 15 are further arranged below the same. The alignment direction (major axis direction) 6a of the liquid crystal molecules on the inner surface of the upper glass substrate 1 of the liquid crystal cell 10 is the reference axis 2
1 forms an angle of 70 ° counterclockwise with respect to 1, and the orientation direction of liquid crystal molecules on the inner surface of the lower glass substrate 2 (long axis direction)
6b makes an angle of 70 ° clockwise with respect to the reference axis 21.

Accordingly, the liquid crystal molecule orientation direction 6b on the inner surface of the lower glass substrate 2 is changed from the liquid crystal molecule orientation direction 6a on the inner surface of the upper glass substrate 11 of the liquid crystal cell 10.
The twist angle of the liquid crystal molecules toward
0 °.

With the above setting, in this embodiment, of the pair of polarizing plates 11 and 13, the easy transmission axis 13 a of the reflection type polarizing plate 13 disposed below the liquid crystal cell 10 and the lower portion of the liquid crystal cell 10. The angle between the inner surface of the side glass substrate 2 and the alignment direction 6b of the liquid crystal molecules is 35 °, and the liquid crystal cell 1
There is an effect of minimizing the influence on the color reproducibility caused by the difference in the birefringence effect between the 0 and the retardation plate 16 due to the presence or absence of the twist.

The following is a specific example of the fourth embodiment. As in the third embodiment, RDP-60166 manufactured by Roddick is used as the liquid crystal material, and Δnd of the liquid crystal cell 10 is used.
The value was set to 1470 nm. The phase difference plate 16 is
A refractive index nx in the stretching direction in the plane, a refractive index ny in a direction orthogonal to the stretching direction in the plane,
A NRZ polycarbonate film (trade name) manufactured by Nitto Denko having a refractive index nz in the thickness direction having a relationship of nx>nz> ny and having a retardation value of 1770 nm was used. That is, the retardation value of the phase difference plate 16 is larger than the Δnd value of the liquid crystal cell 10 by 300 nm.

FIG. 15 shows the chromaticity locus 32 of the display color due to the application of a voltage in the reflective display state of the color liquid crystal display device of the fourth embodiment, and the chromaticity locus 30 of the conventional color liquid crystal display device, and Along with the chromaticity locus 31 of the color liquid crystal display device of the third embodiment,
This is shown in a 931 chromaticity diagram.

The chromaticity change locus 32 of the color liquid crystal display device according to the fourth embodiment of the present invention in FIG.
It is located at almost white chromaticity coordinates when no voltage is applied, and moves in the order of red → blue → green as the voltage increases. The chromaticity change trajectory 32 has a wider color reproduction range than the chromaticity change trajectory 30 of the color liquid crystal display device of the third embodiment as well as the chromaticity change trajectory 30 of the conventional color liquid crystal display device. The color reproducibility of each of the red, blue, and green colors is greatly improved.

This means that the twist angle of the liquid crystal cell 10 is
240 ° in the color liquid crystal display device of the third embodiment
Due to the smaller 220 °, the liquid crystal cell 10
Since the difference between the birefringence effect due to the presence and absence of the twist of the phase difference plate 16 is further reduced, the color reproduction range is wider than the chromaticity change locus 31 of the color liquid crystal display device of the third embodiment. is there. It should be noted that various modifications described after the description of the third embodiment are provided in the fourth embodiment.
The same can be applied to the embodiment.

[0130]

As described above, the color liquid crystal display device according to the present invention uses a reflective polarizing plate as the polarizing plate disposed on the side opposite to the viewing side of the liquid crystal cell, thereby eliminating the need for a reflecting plate. It has a sufficient reflectance, and can perform very bright reflective color display and transmissive color display using a backlight.

Further, in the reflection type display, a metallic image of a mirror image is displayed, and furthermore, a characteristic color display, which has not existed in the past, can be realized in which the display colors of the reflection type and the transmission type are in a complementary color relationship. . Further, the color reproduction characteristics of the birefringent color liquid crystal display device can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a configuration of a first embodiment of a color liquid crystal display device according to the present invention.

FIG. 2 is a plan view showing angles of optical axes in the color liquid crystal display device of the first embodiment.

FIG. 3 is a perspective view for explaining a display principle of the color liquid crystal display device of the first embodiment.

FIG. 4 is a CIE1931 chromaticity diagram showing a locus of chromaticity change of reflected light by the color liquid crystal display device of the first embodiment.

FIG. 5 is a CIE1931 chromaticity diagram showing a locus of chromaticity change of transmitted light by the color liquid crystal display device of the first embodiment.

FIG. 6 is a schematic cross-sectional view showing a configuration of a modification of the first embodiment of the color liquid crystal display device according to the present invention.

FIG. 7 is a schematic sectional view showing a configuration of a second embodiment of a color liquid crystal display device according to the present invention.

FIG. 8 is a plan view showing angles of optical axes in the color liquid crystal display device of the second embodiment.

FIG. 9 is a CIE1931 chromaticity diagram showing a locus of chromaticity change of reflected light by the color liquid crystal display device of the second embodiment.

FIG. 10 is a CIE1931 chromaticity diagram showing a locus of chromaticity change of transmitted light by the color liquid crystal display device of the second embodiment.

FIG. 11 is a schematic cross-sectional view showing a configuration of a modification of the second embodiment of the color liquid crystal display device according to the present invention.

FIG. 12 is a plan view illustrating angles of optical axes in a color liquid crystal display device according to a third embodiment of the present invention.

FIG. 13 is a CIE1931 chromaticity diagram showing the locus of chromaticity change of the color liquid crystal display device of the second embodiment and the conventional color liquid crystal display device.

FIG. 14 is a plan view showing angles of optical axes in a color liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 15 is a CIE1931 chromaticity diagram showing chromaticity change trajectories of the color liquid crystal display device of the second embodiment and the color liquid crystal display devices of the related art and the third embodiment.

FIG. 16 is a diagram showing wavelength dependence characteristics of a Δnd value of a liquid crystal cell and a retardation value of a phase difference plate.

FIG. 17 is a schematic sectional view showing a configuration example of a conventional color liquid crystal display device.

FIG. 18 is a plan view showing an angle of an optical axis in the conventional color liquid crystal display device.

FIG. 19 is a CIE1931 chromaticity diagram showing a chromaticity change locus of the conventional color liquid crystal display device.

[Explanation of symbols]

 1: upper glass substrate 2: lower glass substrate 3: first transparent electrode 4: second transparent electrode 4: sealing material 6: nematic liquid crystal 6a: upper liquid crystal molecule alignment direction 6b: lower liquid crystal molecule alignment direction 10: Liquid crystal cell 11: Absorption type polarizing plate 11a: Easy transmission axis of absorption type polarizing plate 11b: Absorption axis of absorption type polarizing plate 12: Twisted phase difference plate 12a: Upper molecular orientation direction of twisted phase difference plate 12b: Twisted phase difference plate 13: reflective polarizer 13a: easy transmission axis of reflective polarizer 14: semi-transmissive absorber 15: backlight 16: retarder 16a: retarder slow axis 21 reference axis

Claims (10)

[Claims] 1. A liquid crystal cell in which a nematic liquid crystal is sealed between a pair of transparent substrates having electrodes on opposite inner surfaces, a birefringent layer provided on a viewing side of the liquid crystal cell, and an outer side of the birefringent layer. And a reflective polarizing plate disposed on the side opposite to the viewing side of the liquid crystal cell, wherein the absorbing polarizing plate has a linearly polarized light having a vibration plane in a direction perpendicular to the easy transmission axis. Is a polarizing plate that absorbs light, and the reflective polarizing plate is a polarizing plate that reflects linearly polarized light having a vibration plane in a direction perpendicular to the axis of easy transmission. 2. A liquid crystal cell in which a nematic liquid crystal is sealed between a pair of transparent substrates each having an electrode on an opposing inner surface; an absorbing polarizer disposed on a viewing side of the liquid crystal cell; A birefringent layer provided on the side opposite to the side, and a reflective polarizer disposed outside the birefringent layer, wherein the absorption polarizer has linearly polarized light having a vibration plane in a direction orthogonal to the easy transmission axis. Is a polarizing plate that absorbs light, and the reflective polarizing plate is a polarizing plate that reflects linearly polarized light having a vibration plane in a direction perpendicular to the axis of easy transmission. 3. The color liquid crystal display device according to claim 1, wherein a backlight is disposed outside the reflective polarizing plate. 4. The color liquid crystal display device according to claim 1, wherein a semi-transmissive absorbing member and a backlight are sequentially disposed outside the reflective polarizing plate. 5. The color liquid crystal display device according to claim 1, wherein a light absorbing layer is disposed outside the reflective polarizing plate. 6. The liquid crystal cell has a twist angle of 180 to 2
The color liquid crystal display device according to any one of claims 1 to 5, wherein the color liquid crystal display device is a 70 ° super twisted nematic liquid crystal cell. 7. The color liquid crystal display device according to claim 1, wherein the birefringent layer is a twisted retardation plate. 8. The method according to claim 1, wherein the birefringent layer is a retardation plate.
A color liquid crystal display device according to any one of claims 1 to 6. 9. The color liquid crystal display device according to claim 1, wherein the liquid crystal cell is a super twisted nematic liquid crystal cell having a twist angle of 180 to 270 °, and one or more birefringent layers are provided. Phase difference plate,
The sum of the retardations of the retardation plate is 250 to 350 nm larger than the Δnd value represented by the product of the difference Δn in birefringence of the nematic liquid crystal of the liquid crystal cell and the cell gap d that is a gap between the pair of substrates, The angle between the axis of easy transmission of the polarizer and the major axis direction of the liquid crystal molecules in contact with the inner surface of the substrate of the liquid crystal cell on the reflective polarizer side is 35 ° ±
A color liquid crystal display device having a range of 5 °. 10. A color liquid crystal display device comprising a diffusion layer provided between the liquid crystal cell and the reflective polarizing plate.