JPH08184805A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE: To increase the number of colors changeable in a pixel to the number of combinations of color numbers generated according to the difference in the effective values of gradation voltage. CONSTITUTION: The pixel 10 opposing by that a signal electrode 2 formed on the surface opposed to one side substrate between a pair of transparent substrates opposing to each other while holding a liquid cryatal therebetween is intersected with a common electrode 5 formed on the surface opposite to the other side substrate is divided to two picture sections 10a, 10b. Then, when the gradation voltage is impressed to respective picture sections 10a, 10b, orientation of liquid crystal molecules of respective picture sections 10a, 10b are changed respectively according to the impressed gradatioon voltage, and Δnd of a liquid crystal cell is changed according to that, and thus, plural colors are selected by the double refractivity effect of the liquid crystal respectively, and the number of colors changeable in the pixel 10 is increased by the number of combination of the number of colors generating according to the difference of the effective value of the gradation voltage according to the mixing conditions of display colors of respective picture sections 10a, 10b, and multi- color with many number of colors is obtained.

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 utilizing the birefringence effect.

[0002]

2. Description of the Related Art In general, a color liquid crystal display device that performs color display using a color filter is widely known. However, such a color liquid crystal display device has the drawbacks that the color filter is expensive and the light utilization rate is extremely low, and the number of pixels is several times that of the monochrome display, so that precise processing technology is required. Is required. Therefore, as a color liquid crystal display device that does not use a color filter, a liquid crystal display device that performs color display utilizing the birefringence effect of light has been proposed. In this color liquid crystal display device, a signal electrode is formed on one of opposing surfaces of a pair of transparent substrates and a common electrode is formed on the other surface, and liquid crystal molecules are twisted at 180 ° to 270 ° between the pair of substrates, and The STN structure has a structure in which a polarizing plate is arranged outside each of a pair of substrates and a phase plate is arranged between one polarizing plate and one substrate facing the polarizing plate. In such a color liquid crystal display device, the phase plate used for achromatization is used for coloring, and a gray scale voltage (for example, a voltage of 8 gray scales) is applied to the pixel where the signal electrode and the common electrode intersect. As a result, the orientation of the liquid crystal molecules is changed according to the applied gradation voltage, and the Δnd of the liquid crystal cell is changed accordingly. As a result, the Δnd of the liquid crystal cell is changed due to the birefringence effect of the liquid crystal. Colored. For example, four colors of achromatic color, red, green, and blue are arbitrarily displayed depending on the difference in effective value of applied voltage.

[0003]

However, in such a color liquid crystal display device, the number of colors that can be changed in one pixel is only the number of colors (for example, about four colors) generated by the difference in the effective value of the gradation voltage. Yes, it was difficult to display more colors. An object of the present invention is to provide a color liquid crystal display device in which the number of colors that can be changed in one pixel can be increased by combining the number of colors generated by the difference in effective value of gradation voltage into a plurality of sets.

[0004]

In order to achieve the above object, the present invention has a pair of transparent substrates facing each other, a signal electrode formed on the facing surface of one substrate, and a facing surface of the other substrate. A common electrode formed to intersect with the signal electrode,
A liquid crystal interposed between a pair of substrates, a pair of polarizing plates sandwiching the pair of substrates, and a phase plate disposed at least one of the pair of polarizing plates and the pair of substrates. In a color liquid crystal display device having a region where a signal electrode and a common electrode face each other as one pixel, at least one of the signal electrode and the common electrode is divided into a plurality of electrodes to divide one pixel into a plurality of sections. It is characterized in that a color is displayed by the birefringence effect of light according to the voltage applied to each of the plurality of sections.

[0005]

According to the present invention, the pixel in which the signal electrode and the common electrode cross each other and are opposed to each other is divided into a plurality of divisions. The orientation of the liquid crystal molecules in each compartment changes according to the adjustment voltage, and the Δnd of the liquid crystal cell changes accordingly. As a result, a plurality of colors are selected by the birefringence effect of the liquid crystal. The number of colors that can be changed in one pixel can be increased by combining the number of colors generated by the difference in the effective value of the gradation voltage into multiple groups depending on the mixture of the display colors in each section. It is possible to obtain many multi-colors.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the color liquid crystal display device of the present invention will be described below with reference to FIGS. FIG. 1 shows a cross section of a reflective color liquid crystal display device. In this figure, a liquid crystal cell 1 includes a signal electrode 2 and this signal electrode 2
One transparent substrate 4 having an alignment film 3 formed thereon, and the other transparent substrate 7 having a common electrode 5 crossing and facing the signal electrode 2 and an alignment film 6 covering the common electrode 5 formed thereon.
And a sealing material 8 for joining the substrates 4 and 7 at a predetermined interval, and a liquid crystal 9 enclosed in a region surrounded by the substrates 4 and 7 and the sealing material 8.

The liquid crystal cell 1 is of a simple matrix type, and the signal electrode 2 and the common electrode 5 are respectively shown in FIG.
As shown in FIG. 5, the pixel 10 is formed in a strip shape that intersects with each other, and the portions where these electrodes 4 and 7 intersect and face each other. In this case, the signal electrode 2 is divided into two unit signal electrodes 2a and 2b as shown in FIG. Therefore, one pixel 10 is divided into two compartments 10a and 10b in which the two unit signal electrodes 2a and 2b and the common electrode 5 face each other, as shown in FIG. The liquid crystal cell 1 is of STN type, and the liquid crystal 9 has 18 molecules.
The twist orientation is in the range of 0 to 270 °.

On the outside of the other substrate 7 of the liquid crystal cell 1, a polarizer 11 composed of a linear polarizing plate is arranged. Also,
On the outer side of one of the substrates 4, an analyzer 1 composed of a linear polarizing plate is provided.
2 are arranged. Then, the other substrate 7 and the polarizer 1
Between 1 is a phase plate 13 made of polycarbonate or the like.
Is arranged. Further, a reflector 14 is arranged outside the analyzer 12.

In such a color liquid crystal display device, the light from the outside is linearly polarized by the polarizer 11 and the phase plate 13 is provided.
Is incident on the phase plate 1 and passes through the phase plate 13.
A phase difference occurs in the incident light according to the value of the retardation R of 3, and the light with the phase difference enters the liquid crystal cell 1. When this incident light passes through the liquid crystal cell 1,
Due to the birefringence effect of the twist-aligned liquid crystal 9, the phase of the incident light is shifted according to Δnd (the product of the refractive index anisotropy Δn of the liquid crystal 9 and the liquid crystal layer thickness d) of the liquid crystal cell 1. The phase shift differs depending on the wavelength, and the wavelength light shifted along the transmission axis of the analyzer 12, that is, the major axis of the ellipse of the wavelength lights having different elliptically polarized states, is detected. Light having a wavelength along the transmission axis of the photon 12 passes through the analyzer 12. Then, when this wavelength light passes through the analyzer 12, it is linearly polarized, this wavelength light is reflected by the reflection plate 14, and this reflected light is emitted from the polarizer 11 to the outside via the route opposite to the above. It

When no voltage is applied between the signal electrode 2 and the common electrode 5, that is, when the voltage is off, the liquid crystal molecules are in an initial alignment state in which they are twisted at a set twist angle in the range of 180 ° to 270 °. ing. When the voltage is off, the light of each wavelength that has passed through the liquid crystal cell 1 has substantially the same polarization state and forms elliptically polarized light along the transmission axis of the analyzer 12, so that achromatic light is emitted.

From the above-mentioned initial orientation state, a gradation voltage is applied to each unit signal electrode 2a, 2b of the signal electrode 2 and the common electrode 5. In this case, a grayscale voltage is applied to each unit signal electrode 2a, 2b. Then, in the section 10a where the one unit signal electrode 2a and the common electrode 5 face each other, the orientation of the liquid crystal molecules changes according to the applied gradation voltage, and the Δnd of the liquid crystal cell 1 changes accordingly. . As a result, in the portion corresponding to the section 10a, one of a plurality of colors (for example, red, green, blue, etc.) is selectively displayed due to the birefringence effect of the liquid crystal 9. Similarly, the other unit signal electrode 2b
Also in the section 10b where the common electrode 5 and the common electrode 5 face each other, the orientation of the liquid crystal molecules changes according to the applied gradation voltage, and the Δnd of the liquid crystal cell 1 changes accordingly. As a result, section 10
In the portion corresponding to b, any one of a plurality of colors (for example, red, green, blue, etc.) is selectively displayed due to the birefringence effect of the liquid crystal 9.

In this case, when different gradation voltages are applied to the unit signal electrodes 2a and 2b, respectively, different colors are displayed in the portion corresponding to the section 10a and the portion corresponding to the section 10b. It will be. Therefore, the display colors of each of the divisions 10a and 10b are mixed, and the mixed color becomes the display color of one pixel 10. Therefore, the number of colors that can be changed in one pixel can be increased by the number of combinations of the number of colors generated by the difference in the effective value of the gradation voltage, depending on the mixture of the display colors of the respective sections 10a and 10b. It is possible to obtain a multi-color having a large number of colors.

The display color of this color liquid crystal display device is determined by the twist angle of the liquid crystal molecules, Δnd of the liquid crystal cell 1, and the retardation R of the phase plate 13.
As an example, the twist angle of liquid crystal molecules is 240
When Δnd of the liquid crystal cell 1 is 0.84 μm and the retardation R of the phase plate 13 is 1350 nm, the display color becomes “achromatic” when the liquid crystal molecules of the liquid crystal cell 1 are in the initial twist alignment state. , Section 10a or 10
When a low gray scale voltage is applied to b and the liquid crystal molecules rise slightly, the display color becomes “blue”, and when a middle gray scale voltage is applied and the liquid crystal molecules further rise and align, the display color becomes The display color becomes "green", and the display color becomes "red" when the liquid crystal molecules are vertically aligned and aligned. And each of these divisions 10
The display color in one pixel 10 changes to 10 colors as shown in Table 1 depending on the mixture of the display colors a and 10b.

[0014]

[Table 1]

Although the reflector 14 is arranged outside the analyzer 12 in the above embodiment, the invention is not limited to this, and a semitransparent reflector may be arranged. In this case, by arranging the backlight device on the outside of the semitransparent reflection plate, the light from the backlight device can be incident on the liquid crystal cell 1 through the semitransparent reflection plate. When light is obtained, it can be used as a reflection type, and when external light is dark, a backlight can be turned on to be used as a transmission type liquid crystal display device.

In the above embodiment, the case where one pixel 10 is divided into two sections 10a and 10b has been described. However, the present invention is not limited to this and, for example, as shown in FIG. 4, three signal electrodes 2 are provided. One pixel is divided into unit signal electrodes 2a to 2c.
0 may be divided into three compartments 10a to 10c. By doing so, it is possible to increase the number of combinations of the numbers of colors generated by the difference in the effective value of the gradation voltage. Also,
As shown in FIG. 5, the signal electrode 2 is replaced by two unit signal electrodes 2
It is also possible to divide the common electrode 5 into two unit common electrodes 5a and 5b and divide one pixel 10 into four sections 10a to 10d while dividing the pixel into a and 2b. When the pixels are divided in this manner, the common electrodes 5a and 5b are scanned with different voltages, and the number of display colors of one pixel is further increased by the number of combinations of the numbers of colors caused by the difference in the effective value of the gradation voltage. be able to.

Further, in the above embodiment, 18 liquid crystal molecules are used.
Although the STN type liquid crystal cell 1 twisted in the range of 0 to 270 ° has been described, the present invention is not limited to this, and the present invention can also be applied to a TN type liquid crystal cell in which liquid crystal molecules are twisted approximately 90 °. Further, the present invention can be applied not only to the reflective color liquid crystal display device but also to a transmissive color liquid crystal display device.

[0018]

As described above, according to the present invention, the pixel in which the signal electrode and the common electrode intersect and face each other is divided into a plurality of sections, so that the gradation voltages are respectively applied to the plurality of sections. Is applied, the orientation of the liquid crystal molecules in each compartment changes according to the applied gradation voltage, and the Δnd of the liquid crystal cell changes accordingly. As a result, due to the birefringence effect of the liquid crystal, a plurality of colors are obtained. By selecting the combination of the display colors of each of these sections, the number of colors that can be changed in one pixel can be increased by the number of combinations of the number of colors generated by the difference in the effective value of the gradation voltage. It is possible to obtain multi-color with more colors than

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a reflective color liquid crystal display device to which the present invention is applied.

FIG. 2 is a diagram showing a correspondence relationship between signal electrodes and common electrodes.

FIG. 3 is a diagram showing one pixel in FIG.

FIG. 4 is a diagram showing a first modification in which one pixel is divided into three.

FIG. 5 is a diagram showing a second modification in which one pixel is divided into four.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal cell 2 Signal electrode 4, 7 Substrate 5 Common electrode 9 Liquid crystal 10 Pixel 10a-10d Section 11 Polarizer 12 Analyzer 13 Phase plate 14 Reflector

Claims (4)

[Claims] 1. A pair of transparent substrates facing each other, a signal electrode formed on the facing surface of the one substrate, and a common electrode formed on the facing surface of the other substrate so as to intersect with the signal electrode. A liquid crystal interposed between the pair of substrates, and a pair of polarizing plates having the pair of substrates sandwiched therebetween.
A color liquid crystal display device comprising a pair of polarizing plates and a phase plate disposed on at least one of the pair of substrates, wherein a region where the signal electrode and the common electrode face each other is one pixel, At least one of the signal electrode or the common electrode is divided into a plurality of electrodes to divide the one pixel into a plurality of sections.
A color liquid crystal display device, which displays a color due to a birefringence effect of light according to a voltage applied to each of the plurality of sections. 2. The color liquid crystal display device according to claim 1, wherein the signal electrode is divided into a plurality of parts. 3. The color liquid crystal display device according to claim 1, wherein a reflecting plate or a semitransparent reflecting plate is arranged outside one of the pair of polarizing plates. 4. The color liquid crystal display device according to claim 1, wherein the molecules of the liquid crystal are twisted between the pair of substrates.