JPH07294908A - Color liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide the birefringence control type liquid crystal display element whose display color is easily controlled. CONSTITUTION:The twist angle of liquid crystal 11 in a liquid crystal display cell is set to 90 deg., and the axis of transmission of an upper polarizing plate 14 is made to cross the direction of orientation treatment 8a of a lower oriented film at 130 deg., and the axis of transmission of a lower polarizing plate 13 is made to cross this direction 8a at 150. In this constitution, the display color is changed to red, green blue, black, and white in order when the voltage impressed to liquid crystal 11 is raised, and the operation range for the hue change and that for only the luminance change of achromatic color are separated in accordance with the impressed voltage.

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 displaying a color image by controlling the birefringence of liquid crystal.
In particular, the present invention relates to a color liquid crystal display device capable of displaying a full-color image and easily controlling a display color.

[0002]

2. Description of the Related Art A birefringence control type color liquid crystal display element that displays a color image by applying a voltage (electric field) to liquid crystal to deform the alignment of liquid crystal molecules and utilizing the change in birefringence that occurs at that time is known. Are known.

[0003]

However, in the conventional birefringence control type liquid crystal display element, one display color in which the hue and the brightness are combined is displayed according to each applied voltage. It was not possible to control hue and brightness independently. For this reason, the birefringence control type color liquid crystal display element can display a plurality of colors in color, but it is difficult to perform gradation display for controlling the brightness of the coloring, and full color display cannot be performed. Further, the conventional birefringence control type liquid crystal display device cannot display red, green, blue, white and black with high color purity, and it is difficult to display a beautiful full color image.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a color liquid crystal display device whose display color can be easily controlled. Another object of the present invention is to provide a color liquid crystal display device capable of displaying highly pure colors.

[0005]

In order to achieve the above object, the color liquid crystal display element of the present invention comprises a pair of substrates each having electrodes formed on the inner surfaces thereof and arranged to face each other.
An alignment film formed on the inner surfaces of the pair of substrates, a liquid crystal sealed between the alignment films, and a liquid crystal cell formed by:
In a liquid crystal display device configured to display a color image by controlling birefringence of liquid crystal by controlling a voltage applied between electrodes facing each other, which is composed of polarizing plates arranged with the liquid crystal cell interposed therebetween, an applied voltage A first operating range in which the hue of the display color changes in accordance with the above, and a second operating range in which the achromatic brightness changes in accordance with the applied voltage and which is different from the first operating range. To do.

[0006]

In the liquid crystal display device of the present invention, the first operation range in which the hue of the display color changes in accordance with the applied voltage, and the first operation range in which the achromatic brightness changes in accordance with the applied voltage and is different from the first operation range. It has two operating ranges. Therefore, for example, when the range of the voltage applied to the liquid crystal is 0 to 7 V, 0 to 3.
When the voltage is changed in the range of 5V, the display color changes continuously in red, green and blue, while when the voltage is changed in the range of 3.5V to 7V, only the brightness is continuously displayed in black and white. Change. Therefore, it is easy to control the color of the display image. Furthermore, since the voltage region that changes the hue and the voltage region that changes only the luminance occupy almost the entire range of the voltage applied to the liquid crystal, the voltage range of the applied voltage is not wasted.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings. (First Embodiment) First, the structure of a liquid crystal display element according to the first embodiment will be described with reference to FIGS. 1 is a cross-sectional view of the liquid crystal display element of this embodiment, FIG. 2 is a plan view of a substrate on which pixel electrodes and thin film transistors are formed, and FIG.
4C is a plan view showing the relationship between the alignment treatment direction and the optical axis of the polarizing plate, and FIGS. 4A to 4C are perspective views showing the relationship between the alignment treatment direction and the optical axis of the polarizing plate. is there.

This liquid crystal display element is of an active matrix type, and of a pair of transparent substrates (eg, glass substrates) 1 and 2, the first lower substrate (hereinafter, lower substrate) 1 in FIG. Transparent pixel electrode 3 and pixel electrode 3
And thin film transistors (hereinafter referred to as TFTs) 4 connected to each other are arranged in a matrix.

As shown in FIG. 2, on the lower substrate 1, gate lines (scanning lines) 5 are arranged between rows of pixel electrodes 3, and data lines (color signal lines) are arranged between columns of pixel electrodes 3.
6 is wired. The gate electrode of each TFT 4 is connected to the corresponding gate line 5, and the drain electrode is connected to the corresponding data line 6. The gate line 5 is covered with the gate insulating film (transparent film) of the TFT 4 except for the terminal portion 5a, and the data line 6 is formed on the gate insulating film. The pixel electrode 3 is formed on the gate insulating film, and one end of the pixel electrode 3 is connected to the source electrode of the TFT 4. The gate line 5 is connected to a row driver (gate driver) 21, and the data line 6 is connected to a column driver (data driver) 22.

In FIG. 1, the upper second substrate (hereinafter,
A transparent counter electrode 7 facing each pixel electrode 3 of the lower substrate 1 is formed on the upper substrate 2. The counter electrode 7 is composed of one electrode having an area over the entire display area, and a constant reference voltage is applied. A first alignment film (hereinafter, lower alignment film) 8 is provided on the electrode formation surface of the lower substrate 1. Further, a second alignment film (hereinafter, upper alignment film) 9 is provided on the electrode formation surface of the upper substrate 2. The upper and lower alignment films 9 and 8 are made of, for example, an organic polymer compound such as polyimide, and their facing surfaces are subjected to an alignment treatment by rubbing.

The lower substrate 1 and the upper substrate 2 are adhered to each other via a frame-shaped sealing material 10 at their outer peripheral edges. Liquid crystal 11 is enclosed in a region surrounded by the lower substrate 1, the upper substrate 2, and the sealing material 10. The gap between the lower substrate 1 and the upper substrate 2 (more accurately, the gap between the alignment films 8 and 9 = the liquid crystal layer thickness d) is a gap material 1 arranged in a scattered state in the liquid crystal enclosing region.
It is held at a constant value by 2. A first polarizing plate (hereinafter, lower polarizing plate) 13 is arranged under the lower substrate 1, and a second polarizing plate (hereinafter, upper polarizing plate) 14 is arranged on the upper substrate 2. The optical axes of the polarizing plates 13 and 14 are set with reference to the alignment treatment direction of the alignment film 8. A reflection plate 15 is arranged below the lower polarization plate 13. In FIG. 1, reference numeral 16 indicates a liquid crystal cell.

The liquid crystal 11 is composed of, for example, a nematic liquid crystal to which a chiral liquid crystal for twist alignment is added. The product of optical anisotropy Δn of liquid crystal 11 and layer thickness d Δn ·
If d is too large, the viewing angle becomes narrow and the response speed becomes slow. Furthermore, the display color changes abruptly due to a slight change in the applied voltage, which is not preferable. If Δn · d is too small, full-color display becomes difficult. Therefore, in this embodiment, the optical anisotropy Δn of the liquid crystal 11 is 0.1.
9 to 0.25, the liquid crystal layer thickness d is 4 to 5 μm, and the product Δn · d is 0.7 μm or more and less than 1.1 μm, preferably 0.85 to 1.05 μm, and more preferably 0.
95 to 1.03 μm.

As shown in FIGS. 3B and 4B, the alignment treatment direction 9a of the upper alignment film 9 intersects the alignment treatment direction 8a of the lower alignment film 8 counterclockwise at 90 °. ing. As a result, the liquid crystal molecules are in an aligned state in which they are twisted by 90 ° from the lower substrate 1 side toward the upper substrate 2.

Further, as shown in FIGS. 3A and 4A, the transmission axis 14a of the upper polarizing plate 14 intersects the alignment treatment direction 8a of the lower alignment film 8 at 130 °. further,
As shown in FIGS. 3C and 4C, the transmission axis 13a of the lower polarizing plate 13 intersects the alignment treatment direction 8a of the lower alignment film 8 at 150 °. Therefore, the transmission axis 13a of the lower polarizing plate 13 and the transmission axis 14a of the upper polarizing plate 14 intersect at approximately 20 °.

According to the liquid crystal display device having such a structure,
By controlling the voltage applied between the pixel electrode 3 and the counter electrode 7, the alignment state of liquid crystal molecules is changed. The birefringence effect of the liquid crystal layer changes with the change of the alignment state of the liquid crystal molecules,
Depending on the retardation for each wavelength, each wavelength light has a different polarization state for each wavelength. Therefore, the peak wavelength of the light emitted from the upper polarizing plate 14 changes according to the change of the applied voltage, and the display color changes. That is, the display color (hue) can be controlled by controlling the applied voltage.

The change in the liquid crystal retardation is Δnd
Depends on the size of. Therefore, if Δn · d is too large, the display color changes abruptly in response to changes in applied voltage, and Δn · d
If is too small, the display color hardly changes even if the applied voltage is changed. In this embodiment, by adopting the liquid crystal 11 having Δn · d of 0.7 μm or more and less than 1.1 μm and the optical arrangement shown in FIGS. 3 and 4, the color changes in accordance with the change of the applied voltage. The second operation range in which the brightness (brightness) changes according to the change in the operation range and the applied voltage can be provided, and the color selection and the lightness selection can be controlled separately. Therefore, it becomes easy to control the display color, and the three primary colors of red, green, and blue can be sequentially displayed in the first operation range, and black and white can be displayed in the second operation range. Can be displayed. In addition, the contrast is high and the color purity is excellent. Moreover, since the twist angle of the liquid crystal molecules is as small as about 90 °, the response speed is fast and a moving image or the like can be displayed. Twisting the liquid crystal 11 about 90 ° is possible with almost all liquid crystal materials,
The range of selection of the liquid crystal material and the material of the alignment film is widened. Further, since Δn · d is relatively small, that is, 0.7 μm or more and less than 1.1 μm, the viewing angle is wide, and the display color of the display color due to the slight variation of the thickness d of the liquid crystal layer due to the variation of the manufacturing process, the variation of the power supply voltage, or the like. Variation is unlikely to occur, and a desired color image can be stably displayed.

Specific examples and comparative examples of the liquid crystal display element based on the first embodiment will be described below. Specific Example 1 In Specific Example 1, the liquid crystal 11 is BDH manufactured by Merck & Co., Inc.
-TL205 (hereinafter referred to as liquid crystal 1) was used. The liquid crystal has an NI point of 87 ° C., Δn of 0.218, and a viscosity of 45 c.
The p and the pitch P were 69 μm. The liquid crystal layer thickness d was set to 4.63 μm, and Δn · d was set to 1.01 μm. Further, the single transmittances of the polarizing plates 13 and 14 are 44%, the polarization degree is 99.5%, and the lower polarizing plate 13 is used as the reflecting plate 15.
The bottom surface of aluminum was vapor-deposited with aluminum. Furthermore, as described above, the crossing angle between the transmission axis 14a of the upper polarizing plate 14 and the alignment treatment direction 8a of the lower alignment film 8 is 130 °, the alignment treatment direction 9a of the upper alignment film 9 and the alignment treatment of the lower alignment film 8 are performed. The intersection angle with the direction 8a was set to 90 ° (the twist angle of the liquid crystal 11 was 90 °), and the intersection angle between the transmission axis 13a of the lower polarizing plate 13 and the alignment treatment direction 8a of the lower alignment film 8 was set to 150 °.

FIG. 5 shows the relationship between the applied voltage, the reflectance and the display color in this case, and FIG. 6 shows the CIE (x, y) chromaticity diagram. As shown in FIGS. 5 and 6, the display color changed in the order of red → green → blue → black → white as the applied voltage increased, and full-color display was possible. Further, in the low applied voltage region (applied voltage <2.4V), the hue changes, and in the high applied voltage region (2.4V <applied voltage <7), only the brightness changes and the hue changes. It is possible to clearly separate the voltage region to be applied and the voltage region in which only the brightness is changed in the achromatic color, and it is very easy to control the display color. In the voltage region in which only the brightness is changed in the achromatic color, the brightness monotonously increases or decreases according to the increase or decrease of the applied voltage, and the control of the display gradation becomes very easy. The color purity of the display color was also excellent.

Concrete Example 2 In Concrete Example 2, the liquid crystal 11 is trade name BDH manufactured by Merck & Co., Inc.
-TL215 (hereinafter referred to as liquid crystal 2) was used. The liquid crystal has an NI point of 83 ° C., Δn of 0.204, and a viscosity of 44 c.
The p and the pitch P were 73 μm. The liquid crystal layer thickness d was set to 4.63 μm, and Δn · d was set to 0.945 μm. The other configurations were the same as those in Example 1. Also in this case, the display color changes from red → green → blue → as the applied voltage rises.
It changed from black to white, and full-color display was possible. In addition, the voltage range in which the hue changes and the voltage range in which only the brightness changes in the achromatic color can be clearly separated, which makes it very easy to control the display color. In the voltage region in which only the brightness is changed in the achromatic color, the brightness monotonously increases or decreases according to the increase or decrease of the applied voltage, and the control of the display gradation becomes very easy. The color purity of the display color was also excellent.

(Second Embodiment) Next, a second embodiment of the present invention will be described. The basic structure of the liquid crystal display element of this embodiment is the same as that of the liquid crystal display element of the first embodiment shown in FIGS. However, the transmission axis 14a of the upper polarizing plate 14 intersects with the alignment treatment direction 8a of the lower alignment film 8 at 40 °, and the transmission axis 13a of the lower polarizing plate 13 aligns with the alignment treatment direction 8a of the lower alignment film 8.
This is different from the first embodiment in that the upper and lower polarizing plates 14 and 13 are arranged so as to intersect with each other at 155 °.

FIG. 7 shows an example of the relationship between applied voltage, reflectance and display color in a concrete example of the liquid crystal display device according to the second embodiment, and FIG. 8 shows its chromaticity diagram. In these graphs, the above-mentioned liquid crystal 2 is used as the liquid crystal 11, and the liquid crystal layer thickness d is 4.
63 μm, the single transmittance of the polarizing plates 13 and 14 is 44%, the polarization degree is 99.5%, and the lower polarizing plate 13 is used as the reflecting plate 15.
It was obtained when using the aluminum whose bottom surface was vapor-deposited.

As is clear from FIGS. 7 and 8, the display color changed in the order of green → blue → red → white → black as the applied voltage increased, and full-color display was possible. Further, the voltage range in which the hue changes (0 to 2.8V) and the voltage range in which only the brightness changes in the achromatic color (0 to 7V) can be clearly separated, and the brightness in the achromatic color depends on the change in the voltage. It increased or decreased monotonically.

(Third Embodiment) Next, a third embodiment of the present invention will be described. The configuration of the liquid crystal display element of the third embodiment is the same as that of the liquid crystal display of the first embodiment except that a retardation plate 31 is arranged between the upper substrate 2 and the upper polarizing plate 14 as shown in FIG. It has the same structure as the element. The retardation plate 31 is composed of a biaxial retardation plate having a retardation also in the thickness direction, and for example, the Nz coefficient value (nx-nz) / (nx-ny) is 0.
It is about 2 to 0.8. Here, nx is the refractive index in the direction in which the refractive index is maximum on the plane of the retardation plate, ny is the refractive index in the direction orthogonal to the direction of nx on the plane of the retardation plate, and nz is the direction of nx and The refractive index in the direction orthogonal to the ny direction is shown.

As shown in FIGS. 10A and 11A, the transmission axis 14a of the upper polarizing plate 14 intersects with the alignment treatment direction 8a of the lower alignment film 8 at 170 °. Figure 10
As shown in (D) and FIG. 11 (D), the transmission axis 13a of the lower polarizing plate 13 has the alignment treatment directions 8a and 150 of the lower alignment film 8.
They intersect at °. That is, the transmission axis 13a of the lower polarization plate 13
And the transmission axis 14a of the upper polarizing plate 14 intersects at approximately 20 °. In the retardation plate 31, the direction (stretching axis) 31 a having the largest refractive index on the plane is the alignment treatment direction 8 of the lower alignment film 8.
It is arranged so as to intersect with a at 150 °.

According to the liquid crystal display device having such a structure,
By controlling the voltage applied between the pixel electrode 3 and the counter electrode 7, the alignment state of the liquid crystal molecules changes, and the display color changes from red → green → blue → black → white as the applied voltage increases. .
Therefore, full-color display is possible, and the voltage range for changing the hue and the voltage range for changing the brightness in an achromatic color can be divided.

FIG. 12 shows an example of the relationship between applied voltage, reflectance and display color in a concrete example of the liquid crystal display device according to the third embodiment, and FIG. 13 shows its chromaticity diagram. In these graphs, the above-mentioned liquid crystal 2 is used as the liquid crystal 11, the liquid crystal layer thickness d is 4.63 μm, and the single transmittance of the polarizing plates 13 and 14 is 47.
%, The degree of polarization is 95%, and the lower polarizing plate 1 is used as the reflection plate 15.
The bottom surface of No. 3 was aluminum vapor-deposited, and the phase difference plate 31 had Δn · d of 370 nm and an Nz value of 0.3.
It was obtained when the one used.

As shown in FIGS. 12 and 13, the display color changes in the order of red → green → blue → black → white as the applied voltage rises, the voltage range in which the hue changes, and the achromatic brightness shows the brightness. The changing voltage range could be separated. Therefore, the display color can be easily controlled. In the voltage region in which only the brightness is changed in the achromatic color, the brightness monotonously increases or decreases according to the increase or decrease of the applied voltage, and the control of the display gradation becomes very easy. The color purity of the display color was also excellent.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. The basic structure of the liquid crystal display element of the fourth embodiment is the same as that of the third embodiment shown in FIG. However,
The transmission axis 14a of the upper polarization plate 14 intersects the alignment treatment direction 8a of the lower alignment film 8 at 140 °, and the transmission axis 13a of the lower polarization plate 13
a intersects the alignment treatment direction 8a of the lower alignment film 8 at 155 °, and the stretching axis (direction in which the refractive index becomes the maximum) 31a on the plane of the retardation plate 31 and the alignment treatment direction 8a of the lower alignment film 8 are 70. The third embodiment differs from the third embodiment in that the upper and lower polarizing plates 14 and 13 and the retardation plate 31 are arranged so as to intersect at an angle of °.

FIG. 14 shows an example of the relationship between applied voltage, reflectance and display color in a concrete example of the liquid crystal display device according to the fourth embodiment, and FIG. 15 shows its chromaticity diagram. These characteristics are
The above liquid crystal 2 is used as the liquid crystal 11, the liquid crystal layer thickness d is 4.63 μm, and the single transmittances of the polarizing plates 13 and 14 are 47.
%, The degree of polarization is 95%, and the lower polarizing plate 1 is used as the reflection plate 15.
The bottom surface of No. 3 was aluminum vapor-deposited, and the phase difference plate 31 had Δn · d of 370 nm and an Nz value of 0.3.
It was obtained when the one used. As is clear from FIG. 14 and FIG. 15, red,
Green, blue, white, and black can be displayed, and the voltage range in which the hue changes and the voltage range in which the brightness changes in the achromatic color can be separated.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described. The basic structure of the liquid crystal display element of the fifth embodiment is the same as that of the liquid crystal display element of the third embodiment shown in FIG. However, the transmission axis 14a of the upper polarizing plate 14 intersects the alignment treatment direction 8a of the lower alignment film 8 at 130 °, and the lower polarizing plate 1
The transmission axis 13a of 3 is the same as the alignment treatment directions 8a of the lower alignment film 8 and 1
So that the stretching axis 31a of the retardation plate 31 intersects with the alignment treatment direction 8a of the lower alignment film 8 at 140 °.
It differs from the third embodiment in that the upper and lower polarizing plates 14 and 13 and the retardation plate 31 are arranged.

FIG. 16 shows an example of the relationship between applied voltage, reflectance and display color in a specific example of the liquid crystal display device according to the fifth embodiment, and FIG. 17 shows its chromaticity diagram. These characteristics are
The liquid crystal 11 shown in the liquid crystal 2 is used, the liquid crystal layer thickness d is 4.63 μm, the single transmittance of the polarizing plates 13 and 14 is 47%, the polarization degree is 95%, and the lower polarizing plate is the reflecting plate 15. 13 was obtained by using aluminum on the lower surface of which was vapor-deposited and using a retardation plate 31 having Δn · d of 370 nm and an Nz value of 0.3. As is apparent from FIGS. 16 and 17, in this configuration also, the voltage range in which the hue changes to red, green, and blue and the voltage range in which the brightness changes in the achromatic color can be separated.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described. FIG. 18 shows a cross-sectional structure of the liquid crystal display element according to this example, in which the space between the upper polarizing plate 14 and the upper substrate 2 is 2 mm.
1 except that the phase difference plates 31 and 32 are arranged.
The configuration is the same as that shown in.

As shown in FIGS. 19 and 20, the upper polarizing plate 1
The transmission axis 14a of No. 4 intersects with the alignment treatment direction 8a of the lower alignment film 8 at 165 °, and the transmission axis 13a of the lower polarizing plate 13 intersects with the alignment treatment direction 8a of the lower alignment film 8 at 150 °. . That is, the transmission axis 13a of the lower polarization plate 13 and the upper polarization plate 14
The transmission axes 14a of the two intersect at approximately 15 °. Further, the upper retardation plate 32 has its stretching axis (the axis having the largest refractive index).
32a is arranged so as to intersect the alignment treatment direction 8a of the lower alignment film 8 at 75 °, and the lower retardation plate 31 has its stretching axis 3
1a is arranged so as to intersect the alignment treatment direction 8a of the lower alignment film 8 at 150 °.

Also in such a structure, the voltage range in which the hue changes between the three primary colors and the voltage range in which only the luminance changes in the achromatic color can be separated.

An example of the relationship between the applied voltage, the reflectance and the display color in a specific example of the liquid crystal display element according to the sixth embodiment is shown in FIG. 21 and its chromaticity diagram is shown in FIG. These characteristics are obtained by using the above-mentioned liquid crystal 1 as the liquid crystal 11, setting the liquid crystal layer thickness d to 5.1 μm, setting the single transmittances of the polarizing plates 13 and 14 to 47%, the polarization degree to 95%, and the reflection plate 15 to be used. Using the lower surface of the lower polarizing plate 13 vapor-deposited with aluminum,
The lower retardation plate 31 and the upper retardation plate 32 are obtained when Δn · d of 370 nm and Nz value of 0.3 are used.

As shown in FIGS. 21 and 22, the display color changes in the order of red → green → blue → black → white as the applied voltage rises, and the voltage region in which the hue changes and the achromatic color shows only the brightness. The changing voltage domain can be isolated. In the voltage region in which only the brightness is changed in the achromatic color, the brightness monotonously increases or decreases according to the increase or decrease of the applied voltage. The color purity of the display color was also excellent. The color purity of each color was also excellent.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described. The basic structure of the liquid crystal display element according to this embodiment is the same as that of the seventh embodiment shown in FIG. However, the transmission axis 14a of the upper polarizing plate 14 intersects with the alignment treatment direction 8a of the lower alignment film 8 at 120 °, and the upper retardation plate 32
The stretching axis 32 a of the lower alignment film 8 is aligned with the alignment treatment directions 8 a and 50 of the lower alignment film 8.
And the stretching axis 31a of the lower retardation plate 31 intersects with the alignment treatment direction 8a of the lower alignment film 8 at 140 °.
The transmission axis 13a of 3 is the same as the alignment treatment directions 8a of the lower alignment film 8 and 1
It differs from the sixth embodiment in that the upper and lower polarizing plates 14 and 13 and the retardation plates 31 and 32 are arranged so as to intersect at 50 °.

As described above, each axis is arranged, the above-mentioned liquid crystal 2 is used as the liquid crystal 11, the liquid crystal layer thickness is 5.1 μm, the single transmittance of the polarizing plates 13 and 14 is 47%, and the polarization degree is 95%, a reflector 15 having a lower polarizing plate 13 with aluminum vapor-deposited on the lower surface thereof, an upper retardation plate 32 having Δn · d of 570 nm, and a lower retardation plate 31 having Δn · d of 400 nm. FIG. 23 shows a change in reflectance and color with respect to an applied voltage in the case of using the above, and FIG. 24 shows a chromaticity diagram thereof. As shown in FIGS. 23 and 24,
Also in this embodiment, the display color changes in the order of red → green → blue → black → white as the applied voltage rises, and a voltage region in which the hue changes between the three primary colors and a voltage region in which only the brightness changes are displayed. Could be separated. The color purity was also excellent.

(Eighth Embodiment) Next, an eighth embodiment of the present invention will be described. The basic structure of the liquid crystal display element according to this embodiment is the same as the basic structure of the sixth and seventh embodiments shown in FIG. However, the transmission axis 14a of the upper polarizing plate 14 intersects the alignment treatment direction 8a of the lower alignment film 8 at 175 °, and the stretching axis 32a of the upper retardation plate 32 is 155 ° with the alignment treatment direction 8a of the lower alignment film 8. Crossing, extending axis 31 of lower phase plate 31
a intersects the alignment treatment direction 8a of the lower alignment film 8 at 75 °,
The upper and lower polarizing plates 14, so that the transmission axis 13a of the lower polarizing plate 13 intersects with the alignment treatment direction 8a of the lower alignment film 8 at 155 °.
13. The sixth point is that the upper and lower retardation plates 32 and 31 are arranged.
It differs from the embodiment and the seventh embodiment.

In this way, each optical axis is arranged, the liquid crystal 11 having the structure shown in the above formula 2 is used, the liquid crystal layer thickness is 5.1 μm, the single transmittance of the polarizing plates 13 and 14 is 47%,
The degree of polarization is set to 95%, the lower polarizing plate 13 is formed by vapor-depositing aluminum on the lower surface of the lower polarizing plate 13, the upper retardation plate 32 is Δn · d of 400 nm, and the lower retardation plate 31 is Δn · d. FIG. 25 shows changes in reflectance and color with respect to applied voltage when d of 570 nm is used.
FIG. 26 shows the chromaticity diagram thereof. As shown in FIGS. 25 and 26, also in this embodiment, the display color changes in the order of red → green → blue → black → white with the increase of the applied voltage, and only the voltage region and the luminance in which the hue changes are displayed. It was possible to separate the voltage region in which the voltage changes, and the color purity was excellent.

As described above, according to the first to eighth embodiments, the hue of the display color changes according to the control of the applied voltage within the control range (0 to 7V) of the applied voltage. Voltage range (0 to about 2.5V) and voltage range (about 2.5V to about 7V) where hue does not change and only brightness changes
Since it is separated, the display color can be easily controlled. Further, in a region where only the brightness changes, the brightness monotonously increases or decreases as the voltage increases or decreases, and it is easy to control the gradation. Further, since the voltage region for changing the hue and the voltage region for changing only the luminance occupy almost the entire range of the voltage applied to the liquid crystal (0 to 7 V in the embodiment), the voltage range of the applied voltage is wasted. Therefore, a desired image can be displayed even when the resolution of the applied voltage is relatively small. According to the first to eighth embodiments, it is possible to display not only the three primary colors of red, green and blue but also an intermediate color between these hues within the first operation range where the hue changes. In the operation range of 2, the brightness can be controlled, so that one pixel is formed by a plurality of pixel electrodes, and the voltage applied to these pixel electrodes is made independent according to the display color to be displayed. Full-color display is possible by controlling the above.

The intersecting angles of the respective optical axes shown in the first to eighth embodiments do not have to be exactly these values, but may be substantially these values. For example, each angle may deviate by about ± 6 °. However, it is desirable to suppress the deviation by about ± 3 °.

In the first to eighth embodiments, examples in which the present invention is applied to a liquid crystal display device having a pair of polarizing plates 13 and 14 are shown, but the present invention is not limited to these embodiments. For example, as shown in FIG. 27, the present invention is also applicable to a liquid crystal display device in which a polarizing plate 14 is arranged only on one upper substrate 2 side and a reflecting plate 33 is provided on the outer surface or inner surface (not shown) of the lower substrate 1. is there. The present invention is not limited to the reflective liquid crystal display element, and can be applied to, for example, a transmissive liquid crystal display element in which the reflection plate 15 is removed from the liquid crystal display elements of the first to eighth embodiments.

In the sixth to seventh embodiments, an example in which the two retardation plates 31 and 32 are arranged between the upper polarizing plate 14 and the upper substrate 2 has been shown. However, for example, two retardation plates are provided. Between the lower polarizing plate and the lower substrate, or one retardation plate between the upper polarizing plate and the upper substrate, and another one between the lower polarizing plate and the lower substrate. It may be arranged at.

The present invention is also applicable to a liquid crystal display element of the type in which liquid crystal molecules are twisted without using an alignment film by controlling the layer thickness of liquid crystal. Further, the twist angle is not limited to 90 °, but 0 °, 45 °, 180
Any value such as °, 270 °, 360 ° may be used. Although the active matrix type liquid crystal display element using the TFT (thin film transistor) as an active element has been described in the above embodiments, the present invention is based on the MIM (Metal Insulator Meth).
It is also applicable to an active matrix type liquid crystal display element using tal) as an active element. Also,
The present invention can also be applied to a simple matrix type liquid crystal display element. In this case, the display color is controlled by controlling the voltage applied to the signal electrode to control the effective voltage applied to the liquid crystal.

[0046]

As described above, according to the liquid crystal display element of the present invention, it is possible to display a full-color image, and further, to provide an operating range in which the hue changes and an operating range in which the brightness changes in an achromatic color. It can be separated and the display color can be easily controlled.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to first and second embodiments of the present invention.

FIG. 2 is a plan view of a substrate on which pixel electrodes and TFTs are formed.

FIG. 3 is a plan view for explaining the alignment treatment direction of the liquid crystal display element and the position of the transmission axis of the polarizing plate according to the first example.

FIG. 4 is a perspective view for explaining the alignment treatment direction of the vertical alignment film and the position of the transmission axes of the upper and lower polarization plates according to the first example.

FIG. 5 is a graph showing a relationship among an applied voltage, a reflectance and a display color in the liquid crystal display element of the first embodiment.

FIG. 6 is a chromaticity diagram of the liquid crystal display element according to the first example.

FIG. 7 is a graph showing the relationship among applied voltage, reflectance and display color in the liquid crystal display element of the second embodiment.

FIG. 8 is a chromaticity diagram of a liquid crystal display element according to a second example.

FIG. 9 is a sectional view of a liquid crystal display device according to third to fifth embodiments of the present invention.

FIG. 10 is a plan view for explaining the alignment treatment direction of the liquid crystal display element according to the third example, the transmission axis of the polarizing plate, and the position of the stretching axis of the retardation plate.

FIG. 11 is a perspective view for explaining the alignment treatment direction of the liquid crystal display element, the transmission axis of the polarizing plate, and the position of the stretching axis of the retardation plate according to the third example.

FIG. 12 is a graph showing the relationship between the applied voltage, the reflectance, and the display color in the liquid crystal display element of the third embodiment.

FIG. 13 is a chromaticity diagram of the liquid crystal display element according to the third example.

FIG. 14 is a graph showing the relationship between the applied voltage, the reflectance, and the display color in the liquid crystal display element of the fourth example.

FIG. 15 is a chromaticity diagram of a liquid crystal display element according to a fourth example.

FIG. 16 is a graph showing the relationship between the applied voltage and the reflectance and display color in the liquid crystal display element of the fifth embodiment.

FIG. 17 is a chromaticity diagram of the liquid crystal display element according to the fifth example.

FIG. 18 is a sectional view of a liquid crystal display device according to sixth to eighth embodiments of the present invention.

FIG. 19 is a plan view for explaining the alignment treatment direction of the liquid crystal display element, the transmission axis of the polarizing plate, and the position of the stretching axis of the retardation plate according to the sixth example.

FIG. 20 is a perspective view for explaining the alignment treatment direction of the liquid crystal display element, the transmission axis of the polarizing plate, and the position of the stretching axis of the retardation plate according to the sixth example.

FIG. 21 is a graph showing the relationship among applied voltage, reflectance and display color in the liquid crystal display element of the sixth embodiment.

FIG. 22 is a chromaticity diagram of the liquid crystal display element according to the sixth example.

FIG. 23 is a graph showing the relationship between the applied voltage, the reflectance, and the display color in the liquid crystal display element of the seventh embodiment.

FIG. 24 is a chromaticity diagram of a liquid crystal display element according to a seventh example.

FIG. 25 is a graph showing the relationship between applied voltage, reflectance and display color in the liquid crystal display element of the eighth embodiment.

FIG. 26 is a chromaticity diagram of a liquid crystal display element according to an eighth example.

FIG. 27 is a sectional view of a liquid crystal display element according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Lower substrate, 2 ... Upper substrate, 3 ... Pixel electrode, 4 ... Thin film transistor, 5 ... Gate line, 6 ... Data line, 7 ... Counter electrode, 8. ..Lower alignment film, 9 ... Upper alignment film,
10 ... Sealing material, 11 ... Liquid crystal, 12 ... Gap material,
13 ... Lower polarizing plate, 14 ... Upper polarizing plate, 15 ... Reflecting plate,
16 ... Liquid crystal cell, 21 ... Row driver, 22 ... Column driver, 31 ... Retardation plate, 32 ... Retardation plate, 33 ... Reflector plate

Claims (11)

[Claims] 1. A pair of substrates each having an electrode formed on the inner surface thereof and facing each other, an alignment film formed on the inner surfaces of the pair of substrates, and a liquid crystal sealed between the alignment films. ,
A liquid crystal cell formed by the liquid crystal cell and a polarizing plate arranged with the liquid crystal cell sandwiched therebetween. By controlling the voltage applied between the opposing electrodes, the birefringence of the liquid crystal is controlled to display a color image. In the liquid crystal display element, the first operation range in which the hue of the display color changes according to the applied voltage, and the second operation range in which the achromatic brightness changes according to the applied voltage and which is different from the first operation range A color liquid crystal display device having a range. 2. The color liquid crystal display device according to claim 1, wherein the first operating range has operating characteristics in which a display color changes into a plurality of colors including three primary colors according to an applied voltage. 3. The color liquid crystal according to claim 1, wherein the first operating range has operating characteristics in which the hue changes in the order of red, green and blue in response to an increase in applied voltage. Display element. 4. The color liquid crystal according to claim 1, wherein the first operating range has operating characteristics in which the hue changes in the order of green, blue and red in response to an increase in applied voltage. Display element. 5. A value of an applied voltage in a second voltage range in which a voltage for operating in the second operation range is applied, as compared with a first voltage range in which a voltage for operating in the first operation range is applied. Is high, any one of claims 1 to 4 characterized in that
And the color liquid crystal display device described in 1. 6. The method according to claim 1, wherein within the second operation range, the brightness is monotonically increased or decreased by increasing the applied voltage. Color liquid crystal display device. 7. A pair of substrates having electrodes formed on the inner surfaces thereof and facing each other, an alignment film formed on the inner surfaces of the pair of substrates, and a liquid crystal sealed between the pair of alignment films. A liquid crystal display element having a first voltage range in which a hue changes according to an applied voltage and a second voltage range in which a brightness changes according to an applied voltage. , The birefringence is controlled by changing the applied voltage in the first range by controlling the applied voltage in the second range, and the applied voltage is controlled in the second range different from the first range. Thus, a color liquid crystal display device comprising: a driving unit that controls the birefringence to change the luminance without changing the hue. 8. The drive means sets the applied voltage to the second voltage.
The color liquid crystal display device according to claim 7, wherein the brightness is monotonically increased or decreased by increasing within the voltage range of. 9. The driving means applies the applied voltage to the second voltage.
9. The color liquid crystal display element according to claim 7, wherein the brightness of the achromatic display is changed by controlling the voltage within the voltage range. 10. The color liquid crystal display device according to claim 7, wherein the first and second voltage ranges occupy substantially the entire range of the voltage applied by the driving means. . 11. A pair of substrates having electrodes formed on the inner surface and arranged to face each other, a liquid crystal sealed between the pair of substrates, and a polarizing plate arranged with the pair of substrates sandwiched therebetween. A polarizing plate arranged on one outer side of the pair of substrates, and a reflection plate arranged on the other inner side or outer side of the pair of substrates,
And a liquid crystal display element having a first voltage range in which the hue changes in accordance with the applied voltage and a second voltage range in which the brightness changes, and a voltage connected to the electrodes and applied to the liquid crystal is controlled. To control the display of the liquid crystal display element by controlling the birefringence, to change the hue of the display color by controlling the applied voltage in the first voltage range, and to control the applied voltage in the second voltage range. A color liquid crystal display device comprising: a driving unit that changes the brightness by doing so.