JPH0973104A - Color liquid crystal display - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: Coloring light without using a color filter to display a plurality of colors with the same pixel, and displaying the three primary colors of white and black and red, green and blue, which are the basics of display. Further, one color of the red, green and blue is displayed with higher color purity to realize a clear and rich multi-color display. A liquid crystal cell 10 and a pair of polarizing plates 21 and 22.
And a retardation plate 23 and a reflection plate 20, and the liquid crystal cell 1
The value of the twist angle and Δnd of the liquid crystal molecule of 0, the value of the retardation of the retardation plate 23, and the pair of polarizing plates 21 and 21.
The direction of the transmission axis of 2 and the slow axis of the retardation plate 23 is changed so that the color of the emitted light is red depending on the voltage applied to the liquid crystal cell 10.
The liquid crystal 18 of the liquid crystal cell 10 is set to change to green, blue, black, and white, and the color of the emitted light of the red, green, and blue when the voltage applied between the electrodes of the liquid crystal cell 10 is the lowest. A dichroic dye was added.

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

This is due to the absorption of light by the color filter, and the color filter absorbs not only the wavelength light outside the wavelength band corresponding to the color but also the light in the wavelength band with a considerably high absorption rate. Therefore, the colored light that has passed through the color filter 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.

There are two types of liquid crystal display devices, a transmissive type which uses light from a backlight for display, and external light, such as natural light or room illumination light, which is used to direct the light to the back side of the liquid crystal display device. There is a reflection type in which a reflection plate is arranged to reflect and display, but when the above-mentioned color liquid crystal display device is a reflection type, it enters from the front surface side, is reflected by the reflection plate on the back surface side, and is emitted to the front surface side. Since the light passes through the color filter twice and the light intensity is double reduced, the display becomes extremely dark, and it becomes almost unusable as a display device.

Moreover, in the above color liquid crystal display device, since the display color of each pixel is determined by the color of the color filter corresponding to that pixel, in order to display many colors,
For example, it is necessary to obtain a desired display color by controlling the light transmission of each pixel by forming a set of three pixels corresponding to the color filters of the three primary colors of red, green and blue. The intensity of light is significantly weakened and the display color is dark.

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.

In this ECB type liquid crystal display device, a pair of polarizing plates are arranged with a liquid crystal cell sandwiching liquid crystal sandwiched between a pair of substrates. In this ECB type liquid crystal display device, one polarizing plate is used. The linearly polarized light that has entered through the liquid crystal cell becomes elliptically polarized light with different polarization states due to the birefringence effect of the liquid crystal layer in the process of passing through the liquid crystal cell, and that light enters the other polarizing plate. Then, the light transmitted through the other polarizing plate becomes a 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 is
Without using a color filter, the light is colored by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell and the polarization effect of the pair of polarizers. Therefore, there is no light absorption by the color filter. Bright color display can be obtained by increasing the transmittance.

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

[0011]

However, in the conventional ECB type liquid crystal display device, the display contrast is low, and white and black which are the basics of display, and red, green and blue which are the three primary colors of light are used. Since it cannot be displayed, a multicolor display with rich colors called full color or multicolor has been impossible at all.

According to the present invention, light is colored without using a color filter, a plurality of colors are displayed in the same pixel, and the three primary colors of white and black and red, green and blue which are the basics of display are displayed. An object of the present invention is to provide a color liquid crystal display device capable of displaying one of the red, green, and blue with a higher color purity to realize a clear and rich multicolor display. It was done.

[0013]

In order to solve the above-mentioned problems, according to the present invention, liquid crystal is sandwiched between a pair of substrates on which electrodes are formed, and molecules of the liquid crystal are transferred from one substrate side to the other substrate side. A liquid crystal cell having a twist orientation in a predetermined direction at a predetermined twist angle, and a pair of polarizing plates arranged with the liquid crystal cell sandwiched therebetween, and a twist angle of liquid crystal molecules of the liquid crystal cell, The value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the thickness d of the liquid crystal layer and the transmission axis direction of the pair of polarizing plates are determined by the color of the emitted light when the incident light is white light. In accordance with the voltage applied between the electrodes of both substrates of the liquid crystal cell, at least red, green, blue, black, and white are set, and the liquid crystal of the liquid crystal cell has red, green, and blue. Characterized by adding a dichroic dye of one of the colors It is.

In the present invention, the dichroic dye added to the liquid crystal of the liquid crystal cell is one of red, green and blue, which is the color of the emitted light when the voltage applied between the electrodes of the liquid crystal cell is the lowest. Is desirable.

In order to solve the above-mentioned problems, the present invention is such that a liquid crystal is sandwiched between a pair of substrates on which electrodes are formed, and the molecules of the liquid crystal are provided in a predetermined direction from one substrate side to the other substrate side. A liquid crystal cell that is twist-aligned in a predetermined direction at a twist angle, a pair of polarizing plates sandwiching the liquid crystal cell, and at least one of the polarizing plates and the liquid crystal cell. A retardation plate, and a twist angle of liquid crystal molecules of the liquid crystal cell, a value of Δnd of the liquid crystal cell, a retardation value of the retardation plate, and transmission axis directions of the pair of polarizing plates. , The direction of the slow axis of the retardation plate, the color of the emitted light when the incident light is white light, depending on the voltage applied between the electrodes of both substrates of the liquid crystal cell, at least red, green , Change to blue, black, white Both the liquid crystal of the liquid crystal cell, wherein the red, green, and is characterized in that the addition of one color of the dichroic dye of blue.

As one form thereof, for example, one retardation plate is provided, and the twist angle of the liquid crystal molecules of the liquid crystal cell is 75 °.
The value of ± 10 °, Δnd is 800 nm to 1100 nm, the value of retardation of the retardation plate is 60 nm ± 20 nm, and the alignment direction of liquid crystal molecules in the vicinity of the substrate on the side opposite to the side where the retardation plate of the liquid crystal cell is arranged is When the direction is 0 °, the transmission axis of the polarizing plate on the side of the retardation plate is 60.5 ° ± 3 ° in the direction opposite to the twist direction of the liquid crystal molecules,
The transmission axis of the polarizing plate on the opposite side is 52.5 ° ± 3 ° in the direction opposite to the twist direction, and the slow axis of the retardation plate is 52.5 ° ± 3 ° in the direction opposite to the twist direction. There is a configuration set to.

In this structure, the color of the emitted light is red when the voltage applied between the electrodes of the liquid crystal cell is the lowest, and the red dye is suitable as the dichroic dye to be added to the liquid crystal of the liquid crystal cell. ing.

In the present invention, the addition amount of the dichroic dye is preferably 0.05% by weight to 5% by weight.

Further, the present invention can be applied to both a transmission type and a reflection type color liquid crystal display device. In the case of being applied to a reflection type color liquid crystal display device, the light of a pair of polarizing plates is used. A reflection plate may be arranged on the outer surface of the polarizing plate on the side opposite to the incident side of.

The color liquid crystal display device according to the present invention utilizes the birefringence action of the liquid crystal layer of the liquid crystal cell or the birefringence action of the liquid crystal layer of the liquid crystal cell and the retardation plate, and the polarization action of the pair of polarizing plates. In this color liquid crystal display device, the linearly polarized light that has passed through one of the polarizing plates and is incident is the birefringence effect of the liquid crystal layer of the liquid crystal cell or the phase difference with the liquid crystal layer of the liquid crystal cell. The polarization state is changed by the birefringence action of both the plate and each wavelength light becomes elliptically polarized light with different polarization state, enters the other polarizing plate, and the light transmitted through this polarizing plate , And becomes colored light of a color corresponding to the ratio of the light intensities of the respective wavelengths of light.

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

The birefringence action of the liquid crystal layer of the liquid crystal cell is changed by the change of the alignment state of the liquid crystal molecules according to the voltage applied to the liquid crystal layer, and the light incident on the other polarizing plate is accordingly changed. Since the polarization state of the light changes, the coloring of the light changes according to the ratio of the light intensity of each wavelength light that passes through this polarizing plate, and the color of the emitted light, that is, the display color, changes between the electrodes of both substrates of the liquid crystal cell. Depending on the voltage applied, at least red,
Change to green, blue, black, white.

Further, in this color liquid crystal display device, since the dichroic dye of one color of red, green and blue is added to the liquid crystal of the liquid crystal cell, the birefringence action and the polarization action are caused. Any of red, green, and blue of the respective colors obtained by the above is displayed with higher color purity due to the absorption of light in the wavelength region other than that color by the dichroic dye.

In this case, the light absorptivity of the dichroic dye is highest when the molecules are in the most oriented orientation with respect to the substrate surface of the liquid crystal cell, and the voltage applied between the electrodes of the liquid crystal cell is increased. That is, it becomes smaller as the dye molecules rise and align together with the liquid crystal molecules.

Therefore, the dichroic dyes are red, green,
Among blue, if the dye of the color of the emitted light when the applied voltage is the lowest, the purity of the display color when the applied voltage is the lowest becomes better, and other display colors, that is, the applied voltage The effect of the dichroic dye on the display color when it is raised to a certain extent is small.

That is, for example, in a color liquid crystal display device having one retardation plate, the liquid crystal molecule twist angle and Δnd of the liquid crystal cell, the retardation of the retardation plate, and
When the transmission axis direction of the pair of polarizing plates and the slow axis direction of the retardation plate are set to the above values, the color of the emitted light is
As the voltage applied between the electrodes of the liquid crystal cell is increased, it changes in the order of red → green → blue → black → white, but if the dichroic dye added to the liquid crystal is a red dye , The purity of red, which is the display color when the applied voltage is the lowest, becomes better, and green, blue, black, and white obtained by increasing the applied voltage are added with a dichroic dye. The color is almost the same as when it is not used.

[0027]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
~ It demonstrates with reference to FIG. The color liquid crystal display device of this embodiment uses external light (natural light, indoor illumination light, etc.) and reflects the light incident from the front side by a reflection plate arranged on the back side for display. Is.

FIG. 1 is a cross-sectional view of a color liquid crystal display device. This color liquid crystal display device includes a liquid crystal cell 10 and front side polarizing plates arranged on the front surface side and the back surface side with the liquid crystal cell 10 interposed therebetween. 21 and the back side polarizing plate 22, one retardation plate 23 arranged between the front side polarizing plate 21 and the liquid crystal cell 10, and the reflection plate 20 arranged on the outer surface (back surface) of the back side polarizing plate 22. It consists of The reflection plate 20 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 an active matrix type in which a TFT (thin film transistor) is an active element, and the electrode 1 formed on the substrate 11 on the back side thereof.
3 is a plurality of pixel electrodes arranged in rows and columns,
The electrode 14 formed on the substrate 12 on the front surface side is a single film-shaped counter electrode facing all of the pixel electrodes 13.

Although not shown in FIG. 1, the substrate 11 on which the pixel electrodes 13 are formed has a plurality of TFTs connected to each pixel electrode 13 and a gate wiring for supplying a gate signal to each row TFT. And data wiring for supplying a data signal to the TFTs in each column.

The alignment films 15 and 16 provided on both the substrates 11 and 12 are horizontal alignment films made of polyimide or the like. These alignment films 15 and 16 are each subjected to an alignment process (rubbing process) in a predetermined direction, and the molecules of the liquid crystal 18 are aligned in the alignment direction on both substrates 11 and 12 (on the alignment films 15 and 16). In a state of being regulated by 15, 16 and inclined with a slight pretilt angle with respect to the surfaces of the alignment films 15, 16, twist orientation is performed in a predetermined direction at a predetermined twist angle from one substrate side to the other substrate side. ing.

In this color liquid crystal display device, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 and the value Δnd of the product of the refractive index anisotropy Δn of the liquid crystal 18 of the liquid crystal cell 10 and the liquid crystal layer thickness d. , The retardation value of the retardation plate 23, the transmission axis directions of the pair of front and back polarizing plates 21 and 22, and the slow axis direction of the retardation plate 23 are output when the incident light is white light. The color of the light emitted from both substrates 11 of the liquid crystal cell 10,
It is set such that at least red, green, blue, black, and white are changed according to the voltage applied between the electrodes 13 and 14 of the 12 electrodes, and the red, green, and
0.05% by weight of dichroic dye of one of blue
5% by weight is added.

FIG. 2 shows the alignment state of the liquid crystal molecules of the liquid crystal cell 10, the transmission axes of the polarizing plates 21 and 22, and the retardation plate 2.
3 is a view of the direction of the slow axis of No. 3 viewed from the surface side of the liquid crystal display device. In this example, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 is 75 ° ± 3 °, and the value of Δnd is 800 nm to 11 nm.
The retardation plate 23 has a retardation value of 60 nm ± 20 nm, and the front side and back side polarizing plates 21 and 22 have transmission axes 21a and 2 thereof.
2a is arranged with the following orientation, and the phase difference plate 23
Is arranged with its slow axis 23a oriented as follows.

That is, as shown in FIG. 2, the liquid crystal molecule alignment direction 11a in the vicinity of one substrate of the liquid crystal cell 10, for example, the rear substrate 11 is 52.5 clockwise with respect to the horizontal axis S of the liquid crystal cell 10. In the direction of ± 5 °, the other surface side substrate 1
The liquid crystal molecule alignment direction 12a in the vicinity of 2 is 52.5 ° ± 5 ° counterclockwise with respect to the horizontal axis S, and the liquid crystal molecules have a twist direction as indicated by a dashed arrow, and The twist alignment is performed clockwise from the side substrate 11 toward the front side substrate 12 at a twist angle of 75 ° ± 10 °.

When the liquid crystal molecule alignment direction 11a in the vicinity of one substrate of the liquid crystal cell 10, for example, the rear substrate 11 on the side opposite to the retardation plate side is 0 °.
The transmission axis 21a of the polarizing plate on which the retardation film 23 is arranged, that is, the front polarizing plate 21 is in the direction of 60.5 ° ± 3 ° in the direction opposite to the twist direction of the liquid crystal molecules, and the polarizing plate on the opposite side. That is, the transmission axis 22a of the back side polarizing plate 22 is in the direction of 52.5 ° ± 3 ° in the direction opposite to the twist direction, and the slow axis 23a of the phase difference plate 23 is in the direction opposite to the twist direction. It is in the direction of 52.5 ° ± 3 °.

In this embodiment, the liquid crystal cell 1 described above is used.
A red dichroic dye is added to the 0 liquid crystal.

The color liquid crystal display device of this embodiment utilizes the birefringence action of the liquid crystal layer of the liquid crystal cell 10, the birefringence action of the retardation plate 23 and the polarization action of the pair of polarizing plates 21 and 22 to emit light. In this color liquid crystal display device, linearly polarized light that has passed through the front-side polarizing plate 21 and is incident on the liquid crystal cell 10 passes through the phase difference plate 23 and the liquid crystal cell 10, and the birefringent action of the phase difference plate 23 and the liquid crystal The polarization state is changed by the birefringence action of the layer, and each wavelength light becomes elliptically polarized light having a different polarization state, enters the back side polarizing plate 22, and the light transmitted through the back side polarizing plate 22 is The colored light becomes a colored light of a color corresponding to the ratio of the light intensity of each wavelength light that constitutes the light, and this colored light is reflected by the reflection plate 20, and the back side polarizing plate 22, the liquid crystal cell 10, the retardation plate 23, and the front side. Polarizer 21
And are sequentially transmitted and emitted to the front surface side of the liquid crystal display device.

The light reflected by the reflection plate 20 is subjected to birefringence by the liquid crystal layer of the liquid crystal cell 10 in the route opposite to that of the incidence in the process of being emitted to the front surface side, and the light is almost the same straight line as the incidence. Since it becomes polarized light and enters the front surface side polarizing plate 21, the light that passes through the front surface side polarizing plate 21 and exits is reflected by the reflection plate 2.
The colored light is almost the same as the light reflected at 0.

The birefringence action of the liquid crystal layer of the liquid crystal cell 10 is changed by the change of the alignment state of the liquid crystal molecules according to the voltage applied to the liquid crystal layer, and accordingly the light is incident on the back side polarizing plate 22. Since the polarization state of the light changes, the coloring of the light changes according to the ratio of the light intensities of the light of the respective wavelengths transmitted through the back side polarizing plate 22.

That is, the electrodes 13 and 14 of the liquid crystal cell 10
When a voltage is applied between the liquid crystal molecules, the liquid crystal molecules are vertically aligned while maintaining the twist alignment state, and the birefringence of the liquid crystal layer decreases as the rising angle of the liquid crystal molecules increases. When the refraction changes,
Since the polarization state of the light that passes through the liquid crystal cell 10 and enters the back-side polarizing plate 22 changes, the coloring of the light changes according to the ratio of the light intensity of each wavelength light that passes through the back-side polarizing plate 22. The light is reflected by the reflection plate 20 and emitted to the front surface side of the liquid crystal display device.

As described above, the color of the emitted light of this color liquid crystal display device, that is, the display color, changes according to the voltage applied between the electrodes 13 and 14 of both substrates 11 and 12 of the liquid crystal cell 10.

The colors which can be displayed by one pixel of this color liquid crystal display device are all three primary colors of red, green and blue, black which is a nearly achromatic dark display, and white which is a nearly achromatic bright display. Contains.

FIG. 3 is an a ^* -b ^* chromaticity diagram showing a change in display color of the color liquid crystal display device. The display color does not apply a voltage between the electrodes 13 and 14 of the liquid crystal cell 10. In the initial state, the color is close to purple (P), and as the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is increased, red (R) → green (G) → blue (B). → black →
It changes in the order of white.

Further, in the color liquid crystal display device, since the dichroic dye of one of red, green and blue is added to the liquid crystal 18 of the liquid crystal cell 10, the birefringence action and One of red, green, and blue obtained by the polarization effect is displayed with higher color purity due to absorption of light in a wavelength range other than that color by the dichroic dye.

In this case, the light absorptivity of the dichroic dye is the largest when the molecules are in the most laid-down alignment state with respect to the substrate surfaces 11 and 12 of the liquid crystal cell 10,
As the applied voltage between the electrodes of is increased, that is,
It becomes smaller as the dye molecules rise and align with the liquid crystal molecules.

Therefore, the dichroic dyes are red, green,
Among blue, if the dye of the color of the emitted light when the applied voltage is the lowest, the purity of the display color when the applied voltage is the lowest becomes better, and other display colors, that is, the applied voltage The effect of the dichroic dye on the display color when it is raised to a certain extent is small.

That is, in the color liquid crystal display device of the above embodiment, as the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is increased, the color of the emitted light is red → green → blue → Although the color changes from black to white, if the dichroic dye added to the liquid crystal 18 is a red dye, the purity of red, which is the display color when the applied voltage is the lowest, becomes better,
The green, blue, black, and white obtained by increasing the applied voltage have almost the same colors as those obtained when the dichroic dye is not added.

In the a ^* -b ^* chromaticity diagram of FIG. 3, the solid line shows the change when the dichroic dye is not added to the liquid crystal 18 of the liquid crystal cell 10, and the broken line shows the liquid crystal 1 of the liquid crystal cell 10.
8 shows a change in display color when a red dichroic dye is added.

As shown in this chromaticity diagram, when a red dichroic dye is added to the liquid crystal 18 of the liquid crystal cell 10, the change in the display color shifts in the direction in which the saturation of red increases, but the shift amount is , Larger in the red area, and becomes smaller as the display color changes in the order of red → green → blue → black → white.

Further, the shift amount of the change in the display color is determined by the characteristics of the dichroic dye and its addition amount. When a general dichroic dye is used, the addition amount of this dichroic dye is 0. In the range of 0.05% by weight to 5% by weight, the purity of red, which is the display color when the applied voltage is the lowest, is improved, and the green color obtained by increasing the applied voltage is increased. Blue, black, and white can be made to have almost the same colors as those when no dichroic dye is added.

Therefore, according to the color liquid crystal display device described above, light is colored without using a color filter to display a plurality of colors in the same pixel, and white and black and red, green and blue which are the basics of display are displayed. Display the three primary colors of
Display one color of green and blue with higher color purity,
It is possible to realize a multicolor display that is clear and rich in color.

The values of the twist angle and Δnd of the liquid crystal molecules of the liquid crystal cell 10, the retardation of the retardation plate 23, the directions of the transmission axes 21a and 22a of the polarizing plates 21 and 22 and the retardation of the retardation plate 23 are set. The orientation of the shaft 23a is not limited to the above-mentioned embodiment, and the point is that the color of the emitted light when the incident light is white light depends on the voltage applied between the electrodes of both substrates of the liquid crystal cell. , At least red, green, blue,
The dichroic dye added to the liquid crystal 18 of the liquid crystal cell 10 may be any color that is set to change to black and white.
Of red, green, and blue, any dye may be used as long as the color of the emitted light when the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is the lowest.

Further, in the above embodiment, the phase difference plate 23 is
The retardation plate 23 is disposed between the liquid crystal cell 10 and the front polarizing plate 21 which also serves as a light incident surface and a display surface (display observation surface). Board) 22
May be disposed between the liquid crystal cell 10 and the liquid crystal cell 10, and even in that case, the twist angle of the liquid crystal molecules of the liquid crystal cell 10 and Δnd
And the retardation of the retardation plate 23 and the polarizing plates 21 and 2.
If the directions of the two transmission axes 21a and 22a and the direction of the slow axis 23a of the retardation plate 23 are properly selected, red, green, blue, black,
It is possible to obtain a white display, and the liquid crystal 18 of the liquid crystal cell 10 has a dichroic dye of red, green, or blue, which is the color of the emitted light when the voltage applied between the electrodes of the liquid crystal cell 10 is the lowest. If is added, the purity of the display color when the applied voltage is the lowest can be improved.

Further, although the color liquid crystal display device of the above-mentioned embodiment is provided with at least one retardation plate 23, the retardation plate may not be used or a plurality of retardation plates may be used.
Even in that case, the twist angles and Δnd of the liquid crystal molecules of the liquid crystal cell 10 and the transmission axes 21 a and 22 of the polarizing plates 21 and 22 are also included.
If the orientation of a is properly set, and if more than one retardation plate is used, the retardation of each retardation plate and the orientation of the slow axis are properly set, and red, green, blue,
Black and white display can be obtained.

As an example, when the retardation plate is not used, the liquid crystal cell 10 has a twist angle of 75 ° ±±.
When the value of Δnd of 800 ° to 1100 nm at 10 ° is used, the transmission of the front side polarizing plate 21 with respect to the liquid crystal molecule alignment direction 11a (0 ° direction) in the vicinity of the back side substrate 11 of the liquid crystal cell 10. The axis 21a is set to the direction of 47.5 ° ± 3 ° in the direction opposite to the twist direction of the liquid crystal molecules, and the transmission axis 22a of the back side polarizing plate 22 is set to the direction of 52.5 ° ± 3 ° in the direction opposite to the twist direction. With such a configuration, the color of the emitted light when the incident light is white light is increased as the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is increased. The order is red → green → blue → black → white.

Further, for example, the front polarizing plate 21 and the liquid crystal cell 1
When two retardation plates are placed so as to overlap with each other, the liquid crystal cell 10 has a twist angle of 75 ° ±±.
When the value of Δnd is 800 nm to 1100 nm at 10 °, the retardation value of the first retardation plate adjacent to the front polarizing plate 21 of the retardation plates of the two retardation plates is 585 nm ± 20 nm, the retardation value of the second retardation plate adjacent to the liquid crystal cell 10 is set to 610.
nm ± 20 nm, and the liquid crystal molecule alignment direction 11a (0 ° near the rear surface side substrate 11 of the liquid crystal cell 10).
Direction), the transmission axis 21a of the front-side polarizing plate 21 is moved to the direction opposite to the twist direction of the liquid crystal molecules by 142.5 ° ± 3.
Direction, the transmission axis 22a of the back side polarizing plate 22 is opposite to the twist direction in the direction of 142.5 ° ± 3 °, the second direction.
Set the slow axis of the retardation plate of 7 in the direction opposite to the twist direction.
It is only necessary to set the direction of 4.5 ° ± 3 ° and the slow axis of the second retardation plate to the direction of 172.5 ° ± 3 ° in the direction opposite to the twist direction. For example, when the color of the emitted light when the incident light is white light is increased as the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is increased, red → green → blue → black → white. Change in order.

The liquid crystal 18 of the liquid crystal cell 10 is also used in a color liquid crystal display device that does not use these retardation plates or in a color liquid crystal display device that uses two retardation plates.
In addition, if a dichroic dye of the color of the emitted light when the applied voltage is the lowest (red in the above example) among red, green and blue is added, the display color when the applied voltage is the lowest Is further improved, and the influence of the dichroic dye on other display colors, that is, the display color when the applied voltage is increased to some extent, is reduced.

Further, the color liquid crystal display device of the above-mentioned embodiment is a reflection type in which the reflection plate 20 is arranged on the back surface side, but the present invention does not have a reflection plate and uses light from the backlight. The present invention can also be applied to a transmissive color liquid crystal display device that displays images.

When the transmission type color liquid crystal display device is provided with a retardation plate, it is desirable to dispose the retardation plate between the polarizing plate on the light emitting surface (display surface) side and the liquid crystal cell. It may be arranged between the polarizing plate on the light incident surface side and the liquid crystal cell.

Further, in each of the above embodiments, the liquid crystal cell 10
Although an active matrix type is used as this, the liquid crystal cell 10 may be a simple matrix type or a segment type.

[0062]

According to the color liquid crystal display device of the present invention, light is colored without using a color filter to display a plurality of colors in the same pixel, and white, black, red, and green, which are the basics of display, are used. , The three primary colors of blue are displayed, and the red,
Display one color of green and blue with higher color purity,
It is possible to realize a multicolor display that is clear and rich in color.

[Brief description of drawings]

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

FIG. 2 is a view of the alignment state of liquid crystal molecules of the liquid crystal cell, the transmission axis of each polarizing plate, and the direction of the slow axis of the retardation plate as viewed from the surface side of the liquid crystal display device.

FIG. 3 is an a ^* -b ^* chromaticity diagram showing a change in display color of the color liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal cell 11a ... Liquid crystal molecule alignment direction in the vicinity of the back side substrate 12a ... Liquid crystal molecule alignment direction in the vicinity of the front side substrate 18 ... Liquid crystal added with dichroic dye 20 ... Reflectors 21, 22 ... Polarizing plate 21a, 22a ... Transmission axis 23 ... Retardation plate 23a ... Slow axis

Claims (7)

[Claims] 1. A liquid crystal is sandwiched between a pair of substrates on which electrodes are formed, and molecules of the liquid crystal are twist-aligned in a predetermined direction at a predetermined twist angle from one substrate side to the other substrate side. A liquid crystal cell, and a pair of polarizing plates arranged to sandwich the liquid crystal cell. The twist angle of the liquid crystal molecules of the liquid crystal cell, the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell, and the liquid crystal layer thickness. The value of the product Δnd of d and the transmission axis direction of the pair of polarizing plates are set so that the color of the emitted light when the incident light is white light is the voltage applied between the electrodes of both substrates of the liquid crystal cell. Accordingly, at least red, green, blue, black, and white are set, and the liquid crystal of the liquid crystal cell is added with a dichroic dye of one of red, green, and blue. Characteristic color liquid crystal display device. 2. The dichroic dye is one of red, green and blue, which is a dye of the color of emitted light when the voltage applied between the electrodes of the liquid crystal cell is the lowest. The described color liquid crystal display device. 3. A liquid crystal is sandwiched between a pair of substrates on which electrodes are formed, and molecules of the liquid crystal are twist-aligned in a predetermined direction at a predetermined twist angle from one substrate side to the other substrate side. A liquid crystal cell, a pair of polarizing plates sandwiching the liquid crystal cell, and at least one retardation plate disposed between any one of the polarizing plates and the liquid crystal cell, The twist angle of the liquid crystal molecules of the liquid crystal cell, the value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the liquid crystal layer thickness d, the value of the retardation of the retardation plate, and the pair of polarizing plates. Direction of the transmission axis and the direction of the slow axis of the retardation plate, the color of the emitted light when the incident light is white light, depending on the voltage applied between the electrodes of both substrates of the liquid crystal cell. , At least when set to change to red, green, blue, black, white Moni, the liquid crystal of the liquid crystal cell, wherein the red, green, a color liquid crystal display device, characterized in that the addition of one color of the dichroic dye of blue. 4. The number of retardation plates is one, the twist angle of liquid crystal molecules of the liquid crystal cell is 75 ° ± 10 °, and the value of Δnd of the liquid crystal cell is 800 nm to 1100 nm,
The retardation value of the retardation plate is 60 nm ± 20 n
When the alignment direction of the liquid crystal molecules in the vicinity of the substrate on the opposite side of the liquid crystal cell on the side of the retardation plate is 0 °, the transmission axis of the polarizing plate on the side of the retardation plate is The direction opposite to the twist direction of the liquid crystal molecules is 60.5 ° ± 3 °, the transmission axis of the polarizing plate on the opposite side is 52.5 ° ± 3 ° in the direction opposite to the twist direction, and the phase difference is The color liquid crystal display device according to claim 3, wherein a slow axis of the plate is in a direction of 52.5 ° ± 3 ° in a direction opposite to the twist direction. 5. The color of emitted light when the voltage applied between the electrodes of the liquid crystal cell is the lowest, and the dichroic dye added to the liquid crystal is a red dye. 4. The color liquid crystal display device according to item 4. 6. A dichroic dye is added in an amount of 0.05% by weight to 5%.
It is weight%, The color liquid crystal display device as described in any one of Claims 1-5. 7. The reflecting plate is arranged on the outer surface of the polarizing plate opposite to the light incident side of the pair of polarizing plates. The color liquid crystal display device described in 1.