JPH07270779A - Active matrix type color liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide an active matrix type color liquid crystal display device of a reflection type which makes it possible to obtain colored light of high luminance by coloring the light without using color filter, to obtain bright display by lessening the loss of light quantity by absorption of light at the substrate and polarizing plate of liquid crystal cell and to display plural colors with one pixel. CONSTITUTION:This liquid crystal display device has the liquid crystal cell 10, one sheet of the polarizing plate 30 and a phase difference plate 31. A counter electrode 21 disposed on the inside surface of the rear surface side substrate 12 of the liquid crystal cell 10 is formed out of a light reflection film. The polarizing plate 30 is arranged on the front surface side of the liquid crystal cell 10 and the phase difference plate 31 is arranged between the liquid crystal cell 10 and the polarizing plate 31. The transmission axis of the polarizing plate 30 and the delay axis of the phase difference plate 31 are shifted diagonally at a prescribed angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type color liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as an active matrix type liquid crystal display device, a TN (twisted nematic) type device has been used. This TN active matrix liquid crystal display device includes an active matrix liquid crystal cell in which liquid crystal molecules are twist-aligned at a twist angle of about 90 °, and a pair of polarizing plates arranged with the liquid crystal cell interposed therebetween. The pair of polarizing plates are provided such that their transmission axes are parallel to each other and their transmission axes are substantially parallel to the alignment direction of the liquid crystal molecules on one substrate of the liquid crystal cell.

The active matrix type liquid crystal cell is one of a pair of transparent substrates which face each other across a liquid crystal layer.
A plurality of transparent pixel electrodes and a plurality of switching elements (for example, thin film transistors) corresponding to the respective pixel electrodes are arranged in a matrix on the inner surface of one substrate, and the pixel electrodes are opposed to the pixel electrodes on the inner surface of the other substrate. A transparent counter electrode is provided, and the alignment direction of the liquid crystal molecules is regulated by the alignment films provided on the electrode formation surfaces of both substrates, and the twist angle between both substrates is about 90 °. It is oriented. In addition, in the liquid crystal,
A nematic liquid crystal having a positive dielectric anisotropy is used.

Further, in this active matrix type liquid crystal cell, a capacitor electrode facing the edge of the pixel electrode is provided on the back side of each pixel electrode of the one substrate, with an insulating film interposed therebetween. The pixel electrode and the insulating film therebetween form a compensation capacitor (storage capacitor) that compensates the holding voltage of the pixel in the non-selected period.

In the above-mentioned TN type liquid crystal display device, incident light from the outside is linearly polarized by one of the polarizing plates and is incident on the liquid crystal cell, and the transmission of light passing through the liquid crystal cell is controlled by the other polarizing plate. In the state where the on-voltage is not applied between the electrodes of both substrates of the liquid crystal cell, that is, the liquid crystal molecules are twist-aligned, the linearly polarized light incident on the liquid crystal cell has a polarization direction of approximately 90 degrees. The linearly polarized light that has been deviated from the liquid crystal cell is emitted, and this linearly polarized light is absorbed by the other polarizing plate, and the display becomes dark.

Further, when an on-voltage is applied between the electrodes of the liquid crystal cell, the liquid crystal molecules rise and align substantially vertically to the substrate surface, and the linearly polarized light incident on the liquid crystal cell exits the liquid crystal cell as it is. Is transmitted through the other polarizing plate and the display becomes bright.

There are two types of liquid crystal display devices, a transmissive type and a reflective type in which a reflection plate is arranged on the back surface. In the reflection type liquid crystal display device, the light incident from the front side is the front surface. The light is reflected by the reflection plate through the side polarizing plate, the liquid crystal cell and the back side polarizing plate, and then emitted again through the back side polarizing plate, the liquid crystal cell and the front side polarizing plate.

By the way, as the above-mentioned TN type active matrix type liquid crystal display device, there is one which displays a multicolor color image. In a color liquid crystal display device which displays this color image, a plurality of liquid crystal cells are provided on one substrate. The color of
For example, three color filters of red, green and blue are provided corresponding to each pixel electrode.

[0009]

However, the above-mentioned conventional liquid crystal display device has a problem that the brightness of the colored light is low and therefore the display is dark because the light is colored by the color filter.

This is due to the absorption of light by the color filter. The color filter not only absorbs light other than the wavelength band corresponding to the color, but also absorbs light in the wavelength band at a considerably high absorption rate. Since the light is absorbed, the light colored by the color filter becomes light in which the light amount is significantly reduced compared to the light in the wavelength band before entering the color filter, and the display becomes dark.

Further, in the case of the reflection type color liquid crystal display device, in the above-mentioned conventional liquid crystal display device, the light incident from the front side thereof is reflected by the front side polarizing plate, the liquid crystal cell and the back side polarizing plate. Reflected by the plate, the reflected light is emitted through the back side polarizing plate, the liquid crystal cell and the front side polarizing plate,
In the process, the light passes through both the substrates of the liquid crystal cell and the polarizing plates on the front and back sides twice, respectively. Therefore, since the light amount loss due to the light absorption by these substrates and the polarizing plate is large, the display becomes darker. turn into.

Further, in the above-mentioned conventional liquid crystal display device, since the display color is determined by the color of the color filter, one pixel cannot display a plurality of colors. INDUSTRIAL APPLICABILITY The present invention is a reflection type active matrix color liquid crystal display device, which obtains colored light of high brightness by coloring light without using a color filter, and moreover, the amount of light due to light absorption by a substrate and a polarizing plate of a liquid crystal cell. It is an object of the present invention to provide a display capable of displaying a bright display with little loss and displaying a plurality of colors with one pixel.

[0013]

The active matrix type color liquid crystal display device of the present invention comprises a liquid crystal cell, one polarizing plate and a retardation plate, and the liquid crystal cell comprises:
Of the pair of substrates facing each other across the liquid crystal layer, a plurality of transparent pixel electrodes and a plurality of switching elements corresponding to the respective pixel electrodes are provided on the inner surface of the transparent substrate on the front surface side, and An active matrix type cell having a counter electrode provided on an inner surface thereof, wherein the counter electrode is formed of a light reflecting film, the polarizing plate is disposed on a surface side of the liquid crystal cell, and the retardation plate is the liquid crystal cell. It is characterized in that it is arranged between the polarizing plate and the transmission axis of the polarizing plate and the slow axis of the retardation plate are slanted by a predetermined angle.

According to the present invention, in the above liquid crystal display device, the liquid crystal cell is such that liquid crystal molecules are twist-aligned between the two substrates, and the orientation direction of the liquid crystal molecules on the front substrate is the rear substrate. The liquid crystal molecules are offset by 90 ° counterclockwise from the front side with respect to the orientation direction of the liquid crystal molecules, and the transmission axis of the polarizing plate is from the front side with respect to the orientation direction of the liquid crystal molecules on the back side substrate of the liquid crystal cell. When viewed from the counterclockwise direction, the retardation plate has a slow axis of about 45 ° in the counterclockwise direction with respect to the alignment direction of the liquid crystal molecules on the back side substrate of the liquid crystal cell when viewed from the front side. And the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the layer thickness d of the liquid crystal layer.
The product Δn · d and the retardation value of the retardation plate are about 1000 nm and about 600 nm, respectively.

[0015]

In the active matrix color liquid crystal display device of the present invention, a linearly polarized light that has entered through a polarizing plate has a retardation plate whose slow axis is obliquely displaced from the transmission axis of this polarizing plate, In the process of sequentially passing through the liquid crystal layer of the liquid crystal cell, the polarization state can be changed by these birefringence effects, and at the inner surface of the back side substrate of the liquid crystal cell, the light is reflected by the counter electrode composed of the light reflection film, and the reflected light is In the process of passing through the liquid crystal layer and the retardation plate, the polarization state is changed to a polarization state different from the polarization state and enters the polarization plate, and the light of the polarization component that passes through the polarization plate is emitted as colored light.

That is, this liquid crystal display device colors light by utilizing the birefringence effect of the retardation plate and the liquid crystal layer of the liquid crystal cell without using a color filter. Changes the polarization state of the transmitted light and hardly absorbs the light, so the polarization state can be changed by these birefringence effects, and the amount of colored light that passes through the polarizing plate and exits through the polarizing plate. Since the amount of light in the wavelength band that becomes the colored light in the incident linearly polarized light is almost the same, colored light with high brightness can be obtained.

Further, although this liquid crystal display device is of a reflection type, the counter electrode provided on the inner surface of the back side substrate of the liquid crystal cell is formed of a light reflecting film, and the counter electrode reflects light. Therefore, the light that enters the liquid crystal display device from the front surface side, is reflected by the counter electrode, and is emitted to the front surface side of the liquid crystal display device, in the process, the front surface side substrate of the liquid crystal cell, the liquid crystal layer, and the phase difference. Two plates and one polarizing plate each
Since it only passes through each time, there is little loss of light amount due to light absorption by the substrate of the liquid crystal cell and the polarizing plate. The retardation plate and the liquid crystal layer hardly absorb light as described above.

Therefore, according to this liquid crystal display device,
It is possible to obtain a bright display by coloring light without using a color filter to obtain colored light of high brightness and reducing the loss of light amount due to light absorption by the substrate of the liquid crystal cell and the polarizing plate.

Furthermore, in this liquid crystal display device, the alignment state of the liquid crystal molecules changes according to the magnitude of the voltage applied between the electrodes of both substrates of the liquid crystal cell, which changes the birefringence of the liquid crystal layer. Therefore, by controlling the voltage applied to the liquid crystal cell, it is possible to change the color of the colored light that passes through the polarizing plate and is emitted after the polarization state is changed by the birefringence effect of the retardation plate and the liquid crystal layer. Therefore, one pixel can display a plurality of colors.

Further, in the liquid crystal display device of the present invention, as described above, the liquid crystal cell is one in which the liquid crystal molecules are twist-aligned between both substrates, and the alignment direction of the liquid crystal molecules on the front side substrate is It is approximately 9 counterclockwise when viewed from the front side with respect to the alignment direction of the liquid crystal molecules on the back side substrate.
The transmission axis of the polarizing plate is deviated by 0 °, the transmission axis of the retardation plate is approximately 45 ° counterclockwise when viewed from the front side with respect to the liquid crystal molecule alignment direction on the back side substrate of the liquid crystal cell, and the slow axis of the retardation plate is the liquid crystal. The direction of the liquid crystal molecules on the back side substrate of the cell is approximately 140 ° counterclockwise when viewed from the front side, the value of Δn · d of the liquid crystal cell is about 1000 nm, and the retardation value of the retardation plate is When it is about 600 nm, one pixel can display colors such as red, green, blue, and white.

[0021]

1 is a sectional view of a part of an active matrix type color liquid crystal display device showing an embodiment of the present invention. This liquid crystal display device is composed of a liquid crystal cell 10, a polarizing plate 30, and a retardation plate 31. The polarizing plate 30 is arranged on the front surface side of the liquid crystal cell 10. Reference numeral 31 is arranged between the liquid crystal cell 10 and the polarizing plate 30.

First, the liquid crystal cell 10 will be described. The liquid crystal cell 10 is an active matrix type cell. In this embodiment, the molecules of the liquid crystal 23 are provided on both substrates 1.
A twisted orientation between 1 and 12 is used.

Of the pair of substrates 11 and 12 facing each other across the liquid crystal layer of the liquid crystal cell 10, the substrate 11 on the front surface side (upper substrate in the drawing) 11 is a transparent substrate made of a glass plate or the like. A plurality of transparent pixel electrodes 13 and a plurality of switching elements 1 corresponding to the respective pixel electrodes 13 are provided on the inner surface of the front-side substrate 11, that is, the surface facing the liquid crystal layer.
4 are arranged in a matrix in the row direction and the column direction, and the pixel electrodes 13 and the switching elements 1 are arranged.
A transparent alignment film 20 is provided on the surface of No. 4.

The switching element 14 is a TFT, for example.
The TFT 14 is a thin film transistor, and the TFT 14 includes a gate electrode 15 formed on the substrate 11, a gate insulating film 16 covering the gate electrode 15, and the gate insulating film 16 described above.
A- formed on the upper surface so as to face the gate electrode 15.
Semiconductor film 17 made of Si (amorphous silicon) or the like
And a source electrode 18 and a drain electrode 19 formed on both sides of the semiconductor film 17. In addition,
The gate insulating film 16 is formed on almost the entire surface of the substrate 11.

Although not shown, the front side substrate 11 is also provided.
Includes a gate line (address line) for supplying a gate signal to the gate electrode 15 of the TFT 14, and the TF.
A data line for supplying a data signal according to the image data is wired to the drain electrode 19 of T14.

The gate line is formed integrally with the gate electrode 15 of the TFT 14 on the substrate 11,
The gate line is covered with the gate insulating film 16 except for its terminal portion. Also, the above data line is
The data line is formed on the gate insulating film 16 and is connected to the drain electrode 19 of the TFT 14.

The pixel electrode 13 is formed on the gate insulating film 16, and each pixel electrode 13 is connected to the source electrode 18 of the corresponding TFT 14 at one end thereof.

On the other hand, the substrate (lower substrate in the figure) 12 on the back side of the liquid crystal cell 10 is made of glass or a resin film (the glass plate in the figure), and the inner surface of the substrate 12 on the back side, that is, the liquid crystal layer. A counter electrode 21 that faces all the pixel electrodes 13 of the front-side substrate 11 is provided on the surface opposite to, and a transparent alignment film 22 is provided thereon.

The counter electrode 21 is formed of a light reflecting film made of a metal film having a high light reflectance such as an Al (aluminum) film, and the surface thereof is roughened to diffusely reflect the light. There is.

Although not shown, the front-side substrate 11 and the back-side substrate 12 are bonded to each other via a frame-shaped sealing material at the outer peripheral edge thereof, and the liquid crystal 23 is provided on both substrates 1.
The region surrounded by the sealing material between 1 and 12 is filled.

This liquid crystal 23 is a nematic liquid crystal having a positive dielectric anisotropy, and the molecules of this liquid crystal 23 are
Alignment directions on the substrates 11 and 12 are regulated by the alignment films 20 and 22 provided on the substrates 1 and 12, respectively.
The twist orientation is provided between the first and the second portions. The alignment films 20 and 22 are horizontal alignment films made of polyimide or the like, and the film surfaces thereof are subjected to an alignment treatment by rubbing.

The retardation plate 31 is made of a uniaxially stretched film such as polycarbonate, and the retardation plate 31 includes the polarizing plate 30 disposed on the front surface side of the liquid crystal cell 10 and the liquid crystal cell 10. In between, the slow axis (stretching axis) of the retardation plate 31 and the transmission axis of the polarizing plate 30 are arranged so as to be obliquely offset by a predetermined angle. The retardation plate 31 is adhered to the surface of the liquid crystal cell 10 (the outer surface of the front substrate 12), and the polarizing plate 30 is adhered to the surface of the retardation plate 31.

In the liquid crystal display device of this embodiment,
An alignment direction of liquid crystal molecules on both substrates 11 and 12 of the liquid crystal cell 10 (rubbing direction of the alignment films 20 and 22),
The direction of the transmission axis of the polarizing plate 30 and the direction of the slow axis of the retardation plate 31 are set as follows.

In this embodiment, the orientation direction of liquid crystal molecules on the rear substrate 12 of the liquid crystal cell 10 is 0 °.
Direction, and with this direction as a reference, the alignment direction of the liquid crystal molecules on the front surface side substrate 11 of the liquid crystal cell 10 and the polarizing plate 30.
The transmission axis direction and the slow axis direction of the retardation plate 31 are set.

That is, FIG. 2 shows the alignment direction of the liquid crystal molecules of the liquid crystal cell 10 and the retardation plate 31 in the liquid crystal display device.
11A is a plan view showing the slow axis of the liquid crystal cell 10 and the transmission axis of the polarizing plate 30. In FIG.
Alignment direction of liquid crystal molecules in the upper part, 12a is liquid crystal cell 10
3 shows the alignment direction of liquid crystal molecules on the rear substrate 12.

As shown in FIG. 2, the liquid crystal molecule alignment direction 11a on the front surface side substrate 11 of the liquid crystal cell 10 is relative to the liquid crystal molecule alignment direction 12a on the back surface side substrate 12, that is, the azimuth angle of 0 °. 9 from left to right
It is offset by 0 °, and the molecules of the liquid crystal are twist-aligned between the substrates 11 and 12 at a twist angle of approximately 90 °.

Further, in FIG. 2, 30a is a polarizing plate 30.
, 31a indicates the slow axis of the retardation plate 31, and the transmission axis 30a of the polarizing plate 30 is about 45 ° counterclockwise when viewed from the surface side with respect to the above azimuth angle of 0 °. The slow axis 31a of the retardation plate 31 is in the direction of approximately 140 ° counterclockwise as viewed from the surface side with respect to the direction of the azimuth angle of 0 °. Therefore, the slow axis 31a of the retardation plate 31 is a polarizing plate. Thirty
With respect to the transmission axis 30a of FIG.

Further, in the liquid crystal display device of this embodiment,
The value of the product Δn · d of the refractive index anisotropy Δn of the liquid crystal 23 of the liquid crystal cell 10 and the layer thickness d of the liquid crystal layer is set to about 1000 nm (eg Δn = 0.2, d = 500 nm), and the retardation plate is set. Retardation value of about 600 nm.

In the above liquid crystal display device, the liquid crystal cell 1 receives light (natural light or light from an illumination light source) incident from the surface side thereof.
0 is a reflection type that is displayed on the inner surface of the back side substrate 12 by the counter electrode 21 formed of a light reflecting film,
The incident light from the front surface side enters the liquid crystal cell 10 through the polarizing plate 30 and the retardation plate 31, passes through the liquid crystal layer thereof, is reflected by the counter electrode 21, and again passes through the liquid crystal layer to pass through the liquid crystal cell 10. Of the phase difference plate 31 and the polarizing plate 30.

Further, this liquid crystal display device has a liquid crystal cell 10
The display drive is performed by controlling the magnitude of the voltage applied between each pixel electrode 13 of the front side substrate 11 and the counter electrode 22 of the front side substrate 12.

In the above liquid crystal display device, the polarizing plate 30
Since the slow axis 31a of the retardation plate 31 is obliquely shifted with respect to the transmission axis 30a of the linearly polarized light, linearly polarized light that has entered through the polarizing plate 30 passes through the retardation plate 31 due to its birefringence effect. The polarization state is changed to elliptically polarized light, and this elliptically polarized light can be further changed in polarization state by the birefringence effect in the process of passing through the liquid crystal layer of the liquid crystal cell 10, and at the inner surface of the rear substrate 11 of the liquid crystal cell 10. The light is reflected by the counter electrode 21 formed of a reflective film, and in the process of passing through the liquid crystal layer and the retardation plate 31 again, the polarization state is further changed by the birefringence effect of these and returns to the polarizing plate 30.

Since the light returning to the polarizing plate 30 is a non-linear polarized light whose polarization state is changed by the birefringence effect of the retardation plate 31 and the liquid crystal layer, the light of the polarizing plate Only the wavelength light of the polarization component that passes through 30 passes through the polarizing plate 30 and is emitted, and this emitted light becomes colored light corresponding to that wavelength.

That is, this liquid crystal display device colors light by utilizing the birefringence effect of the retardation plate 31 and the liquid crystal layer of the liquid crystal cell 10 without using a color filter. Since the liquid crystal layer and the liquid crystal layer only change the polarization state of the transmitted light and hardly absorb the light, the polarization state can be changed by these birefringence effects, and the amount of the colored light transmitted through the polarizing plate 30 and emitted is Since the amount of light in the wavelength band that becomes the colored light in the linearly polarized light that has entered through the plate 30 is almost the same, colored light with high brightness can be obtained.

Moreover, although this liquid crystal display device is of a reflection type, the counter electrode 21 provided on the inner surface of the back side substrate 11 of the liquid crystal cell 10 is formed of a light reflecting film.
Since the light is reflected at 1, the light that enters the liquid crystal display device from the front surface side thereof, is reflected by the counter electrode 21 and is emitted to the front surface side of the liquid crystal display device, in the process,
It only passes through the front-side substrate 11 of the liquid crystal cell 10, the liquid crystal layer, the retardation plate 31, and the single polarizing plate 30 twice each, and therefore the amount of light due to light absorption by the substrate and the polarizing plate of the liquid crystal cell 10 is increased. There is little loss.

That is, in a conventional reflective liquid crystal display device in which a pair of front and back polarizing plates are arranged across a liquid crystal cell and a reflecting plate is provided on the back surface of the back surface side polarizing plate, the light is incident from the front surface side and the reflection is performed. Light reflected by the plate and emitted to the front side again passes through both substrates of the liquid crystal cell four times in total, and passes through the polarizing plates on the front and back sides four times in total, so that the liquid crystal cell substrate. Although the light amount loss due to the absorption of light by the polarizing plate is large, in the liquid crystal display device of the above-described embodiment, the light incident from the front surface side and emitted to the front surface side again has a total of 2 on the front surface side substrate 11 of the liquid crystal cell 10. Since it only passes through one polarizing plate 30 twice in total, the light amount loss due to light absorption by the substrate and the polarizing plate of the liquid crystal cell 10 is small.

In the liquid crystal display device of the above embodiment, light also passes through the retardation plate 31 and the liquid crystal layer of the liquid crystal cell 10, but the retardation plate 31 and the liquid crystal layer hardly absorb light as described above. Therefore, there is no light amount loss due to these.

Therefore, according to the liquid crystal display device of the above-mentioned embodiment, the light is colored without using the color filter to obtain the colored light of high brightness, and the light amount due to the light absorption by the substrate and the polarizing plate of the liquid crystal cell 10 is obtained. A bright display can be obtained with less loss.

Further, in the conventional liquid crystal display device, since the display color is determined by the color of the color filter, it is not possible to display a plurality of colors with one pixel. For example, one pixel can display a plurality of colors.

That is, in the liquid crystal display device of the above embodiment, the electrodes 13 of both substrates 11 and 12 of the liquid crystal cell 10 are
The alignment state of the liquid crystal molecules changes according to the magnitude of the voltage applied between the two, and thereby the birefringence of the liquid crystal layer changes. Therefore, by controlling the voltage applied to the liquid crystal cell 10, the phase difference plate is controlled. It is possible to change the color of the colored light that passes through the polarizing plate 30 and is emitted after the polarization state is changed by the birefringence effect between the liquid crystal layer 31 and the liquid crystal layer of the liquid crystal cell 10. Can be displayed.

The display drive of this liquid crystal display device is basically the same as the display drive of a generally known active matrix type liquid crystal display device (using a TFT as a switching element). Counter electrode 21
, A reference signal having a waveform synchronized with the synchronization signal is supplied, and the gate signals are sequentially supplied to each gate line in synchronization with the synchronization signal, and in synchronization with that, a data signal having a potential corresponding to the image data is supplied to each data line. The potential of the data signal is controlled according to the image data, and the data signal of the potential corresponding to the image data is supplied to the pixel electrode 13 via the TFT 14, and each pixel electrode 13 A voltage corresponding to the image data is applied between the counter electrode 21 and the counter electrode 21.

The display color of the liquid crystal display device will be described. For example, as described above, the liquid crystal cell 10 is one in which liquid crystal molecules are twist-aligned between the substrates 11 and 12, and on the front surface side substrate 11. The alignment direction 11a of the liquid crystal molecules is approximately 90 ° counterclockwise when viewed from the front side with respect to the alignment direction 12a of the liquid crystal molecules on the rear substrate 12.
The transmission axis 30a of the polarizing plate 30 is displaced and the liquid crystal cell 10
The counterclockwise direction of the liquid crystal molecule alignment direction 12a on the back side substrate 12 is approximately 45 ° when viewed from the front side, and the slow axis 31a of the retardation plate 31 is the back side substrate 12 of the liquid crystal cell 10.
The direction is approximately 140 ° counterclockwise when viewed from the surface side with respect to the liquid crystal molecule alignment direction 12a above, the value of Δn · d of the liquid crystal cell 10 is about 1000 nm, and the retardation value of the retardation plate 31 is about 600 nm. In some cases, one pixel can display colors such as red, green, blue, and white according to the applied voltage.

FIG. 3 is a CIE chromaticity diagram showing the color change of the emitted light with respect to the applied voltage of the liquid crystal display device. The liquid crystal display device has a direction of 30 ° with respect to its normal line (the azimuth may be arbitrary). The result of observing the emitted light from the normal direction of the liquid crystal display device is shown by allowing white light to enter.

As shown in FIG. 3, in the above liquid crystal display device, the color of the emitted light is changed to P as the voltage value applied between the electrodes 13 and 21 of the liquid crystal cell 10 is increased.
The color changes from point S to point Pe as shown by the arrow, and in the middle of that, the colors become green G, blue B, red R, and white W with high light intensity and good color purity.

The x coordinate value and y coordinate value of each of these colors G, B, R and W are x = 0.299, y for green G.
= 0.396, blue B x = 0.247, y = 0.23
3, red R x = 0.399, y = 0.402, white W x
= 0.332, y = 0.351, and both have sufficiently satisfactory color purity.

In the above liquid crystal display device, as shown in FIG.
As described above, the color of the emitted light is close to white W while changing from green G to blue B, but in this vicinity, the color change due to the change in voltage is large, and therefore this color is displayed. Therefore, it is desirable to display the white W at a voltage higher than the voltage for obtaining the display color of red R, because the voltage control for this is troublesome.

As described above, in the above liquid crystal display device, the colors of the emitted light are green G, blue B, red R, and white W according to the applied voltage, so that red, green, and blue are formed in one pixel. It is also possible to display a white color, or by displaying different colors in a plurality of adjacent pixels, it is possible to display a mixed color of a plurality of colors of red, green, blue, and white.

The liquid crystal display device of the above embodiment is
The display colors of green, blue, and white are displayed. The display colors of this liquid crystal display element are the applied voltage and both substrates 1 of the liquid crystal cell 10.
Alignment direction 11a, 12a of liquid crystal molecules on 1, 12
And the direction of the transmission axis 30a of the polarizing plate 30 and the phase difference plate 3
Since it depends on the direction of the slow axis 31a of 1, the display color of the liquid crystal display element can be arbitrarily selected by selecting these conditions.

Further, in the above-mentioned embodiment, the liquid crystal cell 10 is one in which the liquid crystal molecules are twist-aligned, but in the liquid crystal cell 10, the liquid crystal molecules are either homeotropic alignment, homogeneous alignment, or hybrid alignment. Alternatively, the switching element is not limited to the TFT but may be MIM or the like.

[0059]

The active matrix type color liquid crystal display device of the present invention comprises a liquid crystal cell, one polarizing plate and a retardation plate, and the liquid crystal cell faces each other across a liquid crystal layer. Of the pair of substrates, a plurality of transparent pixel electrodes and a plurality of switching elements corresponding to these pixel electrodes are provided on the inner surface of the front transparent substrate, and an opposing electrode is provided on the inner surface of the back substrate. In a matrix type cell, the counter electrode is formed of a light reflecting film, the polarizing plate is disposed on the surface side of the liquid crystal cell, and the retardation plate is provided between the liquid crystal cell and the polarizing plate. Along with the arrangement, the transmission axis of the polarizing plate and the slow axis of the retardation plate are deviated at a predetermined angle from each other, so that light is colored without using a color filter. Get high intensity colored light Moreover, the amount of light loss due to light absorption in the liquid crystal cell substrate and a polarizing plate may be reduced, it is possible to obtain a bright display, it is possible to display a plurality of colors in a single pixel.

Further, in the liquid crystal display device of the present invention, the liquid crystal cell is one in which liquid crystal molecules are twist-aligned between the two substrates, and the orientation direction of the liquid crystal molecules on the front side substrate is on the back side substrate. It is deviated by 90 ° counterclockwise from the surface side with respect to the alignment direction of the liquid crystal molecules.
The transmission axis of the polarizing plate is approximately 45 ° counterclockwise when viewed from the front side with respect to the alignment direction of the liquid crystal molecules on the back side substrate of the liquid crystal cell.
, The slow axis of the retardation plate is approximately 140 ° counterclockwise when viewed from the front side with respect to the liquid crystal molecule alignment direction on the back side substrate of the liquid crystal cell, and Δn.
When the value of d is about 1000 nm and the retardation value of the retardation plate is about 600 nm, red, green,
Blue and white colors can be displayed.

[Brief description of drawings]

FIG. 1 is a sectional view of a part of an active matrix type color liquid crystal display device showing a first embodiment of the present invention.

FIG. 2 is a plan view showing an alignment direction of liquid crystal molecules of a liquid crystal cell of the liquid crystal display device, a slow axis of a retardation plate, and a transmission axis of a polarizing plate.

FIG. 3 is a CIE chromaticity diagram of the liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Liquid crystal cell 11 ... Front side substrate 12 ... Back side substrate 13 ... Pixel electrode 14 ... TFT (Switching element) 20 ... Alignment film 21 ... Counter electrode (light reflection film) 22 ... Alignment film 23 ... Liquid crystal 11a, 12a ... Liquid crystal Molecular orientation direction 30 ... Polarizing plate 30a ... Transmission axis 31 ... Retardation plate 31a ... Slow axis

Claims (2)

[Claims] 1. A liquid crystal cell comprising a liquid crystal cell, one polarizing plate and a retardation plate, wherein the liquid crystal cell is one of a pair of substrates facing each other across a liquid crystal layer, and is a transparent substrate on the front side. An active matrix cell in which a plurality of transparent pixel electrodes and a plurality of switching elements corresponding to the respective pixel electrodes are provided on the inner surface, and a counter electrode is provided on the inner surface of the substrate on the back surface side, wherein the counter electrode is a light It is formed of a reflective film, the polarizing plate is arranged on the surface side of the liquid crystal cell, the retardation plate is arranged between the liquid crystal cell and the polarizing plate, and the transmission axis of the polarizing plate. An active matrix type color liquid crystal display device characterized in that the slow axis of the retardation plate is obliquely displaced by a predetermined angle. 2. A liquid crystal cell is one in which liquid crystal molecules are twist-aligned between both substrates, and the orientation direction of the liquid crystal molecules on the front surface side substrate is the front side with respect to the orientation direction of the liquid crystal molecules on the back surface side substrate. 90 degrees counterclockwise from the side
The transmission axis of the polarizing plate is about 45 ° counterclockwise when viewed from the front side with respect to the alignment direction of the liquid crystal molecules on the back side substrate of the liquid crystal cell, and the slow axis of the retardation plate is ,
The direction is approximately 140 ° counterclockwise with respect to the alignment direction of the liquid crystal molecules on the back side substrate of the liquid crystal cell, the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the layer thickness of the liquid crystal layer. 2. The active matrix type color liquid crystal display device according to claim 1, wherein the product Δn · d value with d is about 1000 nm, and the retardation value of the retardation plate is about 600 nm.