JP2000029015A - Reflection type color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need of increasing the number of nozzles and to adjust color balance only by coloring materials used in a transmission type color liquid crystal display device by providing a color filter area for the blue at one part of red or green pixels or a non-pixel part. SOLUTION: The green, blue and red pixels 104 to 106 are rectangles whose width is (a) and whose length is (b), and they are arranged in the longitudinal direction classified by colors. Green and red color filters 101 and 103 are superposed on the green pixel 104 and the red pixel 106, respectively. A blue color filter 102 is superposed on the blue pixel 105, and further has the area superposed on the non-pixel parts corresponding to gaps between the respective pixels 104 to 106. Thus, the entire color liquid crystal panel is given a bluish tint so as to correct the yellow of the color liquid crystal filter. The dyestuff of the filter used is common to the transmission type color liquid crystal panel, and thickness or density has only to be adjusted in order to lower saturation, then the coloring material needs not be exchanged and the nozzle need not be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a reflection type liquid crystal display device, and more particularly to a structure of a reflection type liquid crystal display device capable of multicolor display with a built-in color filter.

[0002]

2. Description of the Related Art A reflection type liquid crystal display device has hitherto
A reflection type liquid crystal display device for monochrome display using a (twisted nematic) liquid crystal element or a STN (super twisted nematic) liquid crystal element has been mainly used. Reflective color liquid crystal display devices have been actively developed.

[0003] Reflection type liquid crystal display devices having a built-in color filter are roughly classified into the following three conventional examples. The first conventional example uses a liquid crystal mode without using a polarizing plate at all, such as a guest-host system in which a black dye is mixed with a liquid crystal material, and a polymer dispersion system in which a liquid crystal material is dispersed in a polymer. There is. In both methods, since no polarizing plate is used, the brightness is good, but the contrast is low and the method has not been put to practical use. A conventional example using the guest host system is disclosed in, for example, Japanese Patent Application Laid-Open No. Sho 59-198489. A conventional example using the polymer dispersion method is disclosed in, for example, JP-A-5-241143.

[0004] In a second conventional example, one polarizing plate is used, and a reflecting plate is provided inside a liquid crystal display device. This method is further classified into two types, a type using a mirror-like internal reflection plate and providing a diffusion layer on the surface, and a type using a scattering reflection plate. Since both types have only one polarizing plate, the brightness is good, but the contrast is also low.

[0005] In the type using a mirror surface as the intrinsic reflection plate, the specular reflection direction of incident light is bright, but becomes dark at other angles, and the viewing angle characteristics are very poor. In the case of a type using a reflecting plate having a scattering property, it is difficult to control the scattering property, and the manufacturing process becomes complicated. A conventional example of a reflection type liquid crystal display device using one polarizing plate is disclosed in, for example,
No. 223715.

A third conventional example is a liquid crystal display device in which a color filter is added to a normal black and white liquid crystal display device using two polarizing plates. This is a drawback that the contrast is good but dark because two polarizing plates are used. Improving the brightness is a major problem for the time being, and there are various devices for reducing unnecessary reflection and absorption. The members that mainly absorb light are a polarizing plate and a color filter. For example, JP-A-10-3078 discloses an example in which a reflective polarizing plate is used as a lower polarizing plate. In order to increase the transmittance of the color filter, the color filter may be thinned or the pigment density may be reduced. However, the phenomenon that the color filter is colored yellow due to the decrease in the saturation is due to the seminar of the 1998 Electronic Display Exhibition ( Session 4) Reported by Toppan Printing Co., Ltd. in "Current State of Color Filters for Reflection". At this time, the company reported that the red filter was colored with magenta dye to improve the color balance.

[0007]

However, in the above method, it is necessary to additionally prepare magenta in addition to the red, blue and green dyes (dyes or pigments) used in the transmission type liquid crystal panel. When the dyes are switched, in the manufacturing process, one spray nozzle is assigned to one dye in order to keep the quality constant. For this reason, there is a problem that the addition of the magenta dye causes an increase in the number of nozzles.

SUMMARY OF THE INVENTION An object of the present invention is to provide a reflective color liquid crystal display device in which the color balance can be adjusted only with the dyes used in the transmission type color liquid crystal display device so as to eliminate the need for additional nozzles.

[0009]

To achieve the above object, a reflection type color liquid crystal display device of the present invention comprises a first substrate having a first electrode and a second substrate having a second electrode. A color filter provided on one of the substrates,
In a reflection type color liquid crystal display device having reflection means,
A non-pixel portion or a portion of a red or green pixel has a blue filter region.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a reflective type color liquid crystal display device in the best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged view of a main part showing a relationship between a color filter and a pixel when the liquid crystal panel is viewed from above in the first embodiment of the present invention. The green, blue, and red pixels 104, 105, and 106 are rectangles having a width a and a length b, and are arranged in the vertical direction for each color. A green color filter 101 indicated by a horizontal line and a red color filter 103 indicated by a vertical line are each a green pixel 104.
And the red pixel 106. The shaded blue color filter 102 overlaps with the blue pixel 105, and also has a region that overlaps with the non-pixel portion corresponding to the gap between the pixels 104, 105, and 106.

FIGS. 2A and 2B show the arrangement of members in the first embodiment of the present invention. FIG. 2A is a plan view showing an electrode structure in a region corresponding to FIG. 1, and FIG. FIG. 4C is a cross-sectional view of a pixel portion, and FIG. 4C is a cross-sectional view of a non-pixel portion in the same region.
Note that the same numbers as those in FIG. 1 indicate the same members and pixels. In FIG. 2A, signal electrodes 201, 202, and 203 as first electrodes made of indium tin oxide (hereinafter, referred to as ITO) and scanning electrodes 204, 205, and 206 as second electrodes made of ITO are arranged in a straight line. are doing. As pixels, intersections between the signal electrodes 201, 202, and 203 and the scanning electrode 205 correspond to a green pixel 104, a blue pixel 105, and a red pixel 106, respectively. In the future,
The signal electrodes 201, 202, and 203 are referred to as a green signal electrode 201, a blue signal electrode 202, and a red signal electrode 2, respectively.
Call it 03.

In FIG. 2B, between a first substrate 210 made of a 0.5 mm thick glass plate and a second substrate 214 made of a 0.5 mm thick glass plate, a pigment dispersion method is used. A color filter 101, 102, 103 composed of three colors of green, blue and red having a thickness of 0.4 μm, a protective film 211 made of an acrylic material and a scanning electrode 205 having a thickness of 2 μm,
An upper alignment film 213a, a nematic liquid crystal 212 having a 225 ° twist alignment, and a lower alignment film 213b;
Green, blue, and red signal electrodes 201, 202,
Reference numeral 203 denotes a stacked arrangement. Further, a retardation plate 218 having a retardation value R = 0.55 μm and a polarizing plate 219 having a transmittance of 46% are stacked and arranged in order from the glass plate 210 to the outside. Similarly, a diffusion layer 215, a reflective polarizing plate 216, and a light absorption layer 217 are stacked in the order from the glass plate 214 to the outside. Here the blue color filter 102
Are the signal electrodes 201 and 20 for green, blue and red.
The area is also provided in the gap between 2 and 203. Green, blue, and red color filters 101, 102, and 1 used here
Reference numeral 03 denotes a transmission type color liquid crystal panel having a thickness of 0.4 μm instead of a thickness of 1.0 μm, thereby improving the light transmittance while reducing the saturation. .

FIG. 2C shows a case where the green and red color filters 101 and 103 are replaced with a blue color filter 102 in FIG. 2B, and the others are the same as FIG. 2B. is there.

Here, the reflection type polarizing plate 216 will be described. A normal polarizing plate has an axis for transmitting light and an axis for absorbing light, while the reflective polarizing plate 216 has an axis for transmitting light and an axis for reflecting. The light absorbing layer 21 is provided outside the reflective polarizing plate 216.
When printing black or placing a black film as 7,
The transmission axis displays black, the reflection axis displays white, and
Since the reflection efficiency is high, a bright white display can be obtained. Further, since the surface of the white display of the reflective polarizing plate 216 has a mirror surface, a diffusion layer 215 is provided on the surface in order to improve the viewing angle characteristics. In this embodiment, fine particles are dispersed in an adhesive as the diffusion layer 215. The resulting diffusion adhesive layer was obtained.

FIG. 3 is a graph showing the amount of transmitted light in each region of the liquid crystal panel according to the first embodiment of the present invention, in which the vertical axis represents the transmitted light amount T and the horizontal axis represents the wavelength λ. For convenience of description, it is assumed that the spectral characteristics of the illumination light are flat. Curves 302, 30 of green, blue and red pixels 104, 105, 106
Nos. 1 and 303 have peaks in the middle wavelength, short wavelength, and long wavelength regions, respectively. Each of the curves 301, 302,
As for the relationship between 303 and the transmittance, the peak transmittance is 80-9.
On the other hand, since the color filter is thinned and the saturation is reduced, the spread is large and the bottom transmittance (white bias) is about 30% to 50%. The curve 304 indicating the transmission amount of the non-pixel portion has the spectral characteristics of the blue color filter 104, but has a smaller area than the pixel portion, and thus is similar to the curve 301 but has a lower intensity. . Since the transmitted light amounts of the green, blue, and red pixels 104, 105, and 106 are equal, if the light from the pixel portion is overcolor-mixed, it becomes white. However, the liquid crystal panel as a whole becomes bluish because transmitted light from the non-pixel portion is added.

FIG. 4 is an enlarged view of a main part showing a relationship between a color filter and a signal electrode when the liquid crystal panel is viewed from above in the second embodiment of the present invention. Since only the color filter pattern is different from the first embodiment shown in FIGS. 1, 2 and 3, in FIGS. 4 and 5, the pixel and signal electrode are denoted by the same reference numerals as those in FIGS. Is shown.
Green, blue, red signal electrode pixels 201, 202, 203
Has a rectangular shape with a width a and a long length in the vertical direction. The shaded blue color filter 402 is a signal electrode 2 for blue.
02, a signal electrode 201 for green and a signal electrode 202 for blue
, The blue signal electrode 202 and the red signal electrode 203
, And a part of the green signal electrode 201 and a part of the red signal electrode 203. The green color filter 401 indicated by a horizontal line and the red color filter 403 indicated by a vertical line are a signal electrode 201 for green and a signal electrode 203 for red, and a signal electrode 201 for green and a signal electrode for red, respectively. It overlaps with the gap 203 (half each).

FIG. 5 is a graph showing the amount of transmitted light in each region of the liquid crystal panel according to the second embodiment of the present invention. The ordinate represents the amount of transmitted light T, and the abscissa represents the wavelength λ. For convenience of description, it is assumed that the spectral characteristics of the illumination light are flat. Curves 502, 50 of green, blue and red pixels 104, 105, 106
1, 503 have peaks in the middle wavelength, short wavelength, and long wavelength regions, respectively. The right peaks of the curves 502 and 503 of the green pixel 104 and the red pixel 106 are lower than the peak of the curve 501 of the blue pixel 105. This is because there is an area occupied by the blue color filter 402 in some of the green pixels 104 and the red pixels 106.
For the same reason, curve 5 of green pixel 104 and red pixel 106
02 and 503 have a low peak at the same position as the peak of the curve 501 of the blue pixel 105. A curve 504 indicating the transmission amount of the non-pixel portion is represented by green, blue, and red pixels 104 and 105,
The curve 501, 502, 503 of 106 has a small peak at the higher peak position. The reason why the blue peak is highest in the curve 504 is that the area occupied by the blue color filter 402 in the non-pixel portion is the largest. In the present embodiment, similarly to the first embodiment, in addition to the non-pixel portion having a bluish tint, even when the green or red pixels 104 and 106 display white (transmissive), the pixels 104 and 106 are displayed. Is bluish.

In this embodiment, the color filters 101, 1
02 and 103 have a thickness of 0.4 to improve brightness.
μm. In a reflective type color liquid crystal device, it is preferable to increase the maximum transmittance as much as possible. However, if the thickness of the color filter is too thin, the minimum transmittance becomes 50%.
As a result, the saturation is extremely reduced. When prototype experiments were conducted with color filters of various film thicknesses, the maximum transmittance of each color was 8
0% or more was good, and 90% or more was most preferable. On the other hand, the minimum transmittance of each color is preferably between 30% and 50%, and 40% is most preferable in terms of saturation and brightness. Color filters 101, 102, and 10 employed in the present embodiment
The dye No. 3 (also related to the density) is a popular product used in a transmission type color liquid crystal device with a thickness of 1.0 μm. Use this to reduce the thickness of the color filter to 0.3-0.5 μm
Then, it was within the aforementioned conditions.

In the first and second embodiments, the STN liquid crystal element has a twist of 225 °,
By optimizing the arrangement angle of the polarizing plate 219, the retardation plate 218, and the reflective polarizing plate 216 even with a 70 ° twist, a similar reflective color display device can be obtained. In the first and second embodiments, the STN liquid crystal element is used. However, the phenomenon in which the color filter takes on a yellow tint due to a decrease in saturation is also applicable to other types of reflective color liquid crystal display devices using the color filter. it can. If the first embodiment is combined with the second embodiment, both functions are added. In the first and second embodiments, the color filter is made thinner than the transmissive color liquid crystal panel in order to lower the saturation and increase the transmission efficiency. Good. In the first and second embodiments, a color filter (vertical stripe filter) which is long in the vertical direction is modified, but the present invention is also applicable to a color filter having a delta-nabla arrangement or a diagonal arrangement.

[0020]

As is apparent from the above description, according to the present invention, the color filter has a yellow tint when the saturation of the color filter is reduced to obtain a bright reflective color liquid crystal display device. To respond to the phenomenon,
A color filter region for blue is provided in a part or non-pixel part of the red or green pixel. As a result, the entire color liquid crystal panel becomes bluish, and the yellow color of the color filter is corrected. The dye of the color filter used at this time is the same as that used in the transmission type color liquid crystal panel, and only the thickness or density is adjusted to reduce the saturation. In this manner, the necessity of exchanging the dye in the manufacturing process is eliminated, so that an effect of eliminating the need for additional nozzles is obtained.

[Brief description of the drawings]

FIG. 1 is a main part enlarged view showing a relationship between a color filter and a pixel when a liquid crystal panel of a reflection type color liquid crystal display device according to a first embodiment of the present invention is viewed from above.

FIGS. 2A and 2B show a positional relationship of members of the reflective color liquid crystal display device according to the first embodiment of the present invention, wherein FIG. 2A is a plan view showing an electrode structure in a region corresponding to FIG. 1, and FIG. FIG. 4C is a cross-sectional view of a pixel portion in the same region, and FIG. 4C is a cross-sectional view of a non-pixel portion in the same region.

FIG. 3 is a graph showing the amount of transmitted light from each region in the first embodiment of the present invention.

FIG. 4 is a main part enlarged view showing a relationship between a color filter and a signal electrode when a liquid crystal panel of a reflection type color liquid crystal display device according to a second embodiment of the present invention is viewed from above.

FIG. 5 is a graph showing the amount of transmitted light from each region according to the second embodiment of the present invention.

[Explanation of symbols]

 101, 401 Green color filter 102, 402 Blue color filter 103, 403 Red color filter 104 Green pixel 105 Blue pixel 106 Red pixel 201 Green signal electrode 202 Blue signal electrode 203 Red signal Electrodes 204, 205, 206 Scanning electrodes 210, 214 Glass plate 211 Protective film 212 STN liquid crystal 213a, 213b Alignment film 215 Diffusion layer 216 Reflection type polarizing plate 217 Light absorbing layer 218 Phase difference plate 219 Polarizing plate 301, 501 Blue pixel 105 The amount of transmitted light 302, 502 The amount of transmitted light of the green pixel 104 303, 503 The amount of transmitted light of the red pixel 106 304, 504 The amount of transmitted light of the non-pixel portion

Claims (3)

[Claims] 1. A reflection type color liquid crystal display comprising a color filter provided on one of a first substrate having a first electrode and a second substrate having a second electrode, and a reflection means. A reflective color liquid crystal display device, comprising: a non-pixel portion or a blue filter region in a part of a red or green pixel. 2. The thickness of the color filter is 0.3 to
0.5 μm, and 180 μm between the first and second substrates.
2. The reflection type color liquid crystal display device according to claim 1, wherein the reflection type liquid crystal display device has a nematic liquid crystal having a twist alignment of .about.270.degree. 3. The color filter according to claim 1, wherein the color filters are arranged in a vertical stripe arrangement, wherein a stripe width of a blue color filter is wider than a stripe width of a red or green color filter.
2. The reflection type color liquid crystal display device according to claim 1, further comprising a region overlapping with the signal electrodes for red or green.