JPH0373903A - Color filter - Google Patents

Abstract

PURPOSE:To smooth the partition between adjacent picture elements and to improve the quality of displayed images by setting the transmittance or luminance of color filters at the curve distribution characteristics which rise in a central part and fall in a peripheral part. CONSTITUTION:The film thicknesses of filter elements 13 are changed with the curve distribution where the film thickness is small in the central part of the filter elements 13 and increases in the peripheral part by forming the inside surfaces 16 of the respective filter elements 13 to a curved recess surface of a hemispherical surface in order to apply the curve distribution to the transmittance of the filter elements 13. The recessed part of the element 13 is preferably embedded by a flat control film 17 in such a manner that the liquid crystal cell gap does not change by the change of film thickness of the element 13. The formation of the conspicuous peripheral parts of the picture elements is obviated and the connection of the picture elements is smoothed. The boundary lines of the images have inconspicuous zigzags.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is for displaying images in color on display devices such as liquid crystal display devices, electroluminescence display devices, and plasma display devices that display images by a collection of pixels. The present invention relates to a color filter in which a filter element is provided corresponding to each pixel, these filter elements are composed of a plurality of filter elements having different color characteristics, and the filter elements having different color characteristics are mixed and distributed almost uniformly.

"Prior art" This type of color filter is, for example, as shown in Figure 3.
The red filter element R1, the green filter element G, and the blue filter element B are composed of three filter elements having different color characteristics, which are mixed and distributed almost uniformly. Although not shown in the figure, each filter element corresponds to each pixel of the display device.

For example, color filters used in liquid crystal display devices are
As shown in the figure, a glass plate 1 forms one side of the liquid crystal cell at the bottom of the tank.
1, black stripes 12 are formed in a vertical and horizontal lattice pattern on the inner surface, and filter elements 13 are formed in each rectangular opening constituted by the black stripes 12, and these filter elements 13 are shown in FIG. 3, for example. A distribution of colors with different color characteristics is formed as shown in FIG. A transparent electrode 14 is placed on the color filter made up of these filter elements 13.
is formed and the orientation I! is formed on the transparent electrode 14. ! ! 15 is formed. Although not shown in the figure, the alignment film 15 is in contact with the liquid crystal. Each filter element 13 has a side of A as shown in FIG.
A' and u are rectangular with BB'.

In conventional color filters, the transmittance of each filter element has a flat distribution characteristic in each part, as shown in FIG.

"Problems to be Solved by the Invention" In a conventional display device using a color filter configured with a constant transmittance within a filter element, when the border of a displayed image is a diagonal line, The result was a jagged line that changed stepwise from pixel to pixel, making it impossible to display a smooth display.To improve this, it was necessary to make the pixel pitch finer. Also, color mixing did not work well at the borders of the image.

"Means for Solving the Problem" According to the present invention, each filter element of a color filter corresponding to a part or the entire display surface of a display device has a transmittance in which the transmittance increases in the center and decreases in the periphery. It is considered to be a rate distribution characteristic or a brightness distribution characteristic in which the brightness increases in the center and decreases in the peripheral area.

In order to obtain such transmittance distribution characteristics or brightness distribution characteristics, the concentration distribution of the material that provides the color characteristics of each filter element is different between the central portion and the peripheral portion. Alternatively, in order to obtain such transmittance distribution characteristics or brightness distribution characteristics, each filter element has a film thickness that is different between the central portion and the peripheral portion.

"Embodiment" For example, in a color filter used in a liquid crystal display device, in this invention, the transmittance of each filter element is made to have a Gaussian distribution characteristic such that it increases in the center and decreases in the periphery, as shown by the solid line in FIG. . This distribution characteristic is not limited to the Gaussian distribution, but may also be a normal distribution or other distribution characteristics.For example, the distribution characteristic can be selected according to the characteristics of the image, such as an image of only text, an image of a landscape, or an enlarged image of a microscope. can.

In this way, the transmittance of each filter element is not uniform in each part, but has a curved distribution and the transmittance decreases in the peripheral area, so in a liquid crystal display device using this color filter, the peripheral area of the pixel is It becomes less noticeable, the connections between pixels become smoother, and the jagged edges of the image become less noticeable.

For example, when a part of an image normally displayed on one half of the screen is enlarged and displayed on the other half of the screen, the transmittance of each filter element of the color filter is given a curved distribution only in the part corresponding to the enlarged display. The transmittance of each filter element of the color filter in a portion corresponding to the display may have a flat distribution, and the transmittance of each filter element over the entire surface of the color filter does not necessarily have to have a curved distribution.

In order to give a curved distribution to the transmittance of the filter element, for example, as shown in Figure 4, the film thickness of the filter element should be varied in each part, and the concentration of the material that gives the filter element its color characteristics, such as dyes and pigments, should be varied. The distribution is a curved line with low concentration in the center and high concentration in the periphery, as shown by the broken line in FIG.

Alternatively, as shown in FIG. 2 with the same reference numerals assigned to the parts corresponding to those in FIG. The film thickness is changed in a curved distribution so as to increase the thickness, so that a curved distribution of transmittance is obtained. in this case,
The liquid crystal cell gap is 1 of the filter element 13! It is preferable to fill the concave portion of the filter element 13 with a flatness control film 17 made of a transparent resin material or the like so as not to change due to changes in thickness.

In a liquid crystal display device, if the film thickness of the filter element of a color filter differs depending on the color characteristics of the filter element, that is, the red filter element, green filter element, and blue filter element, each filter element transmits at the center wavelength of each color. rate is minimized. In this case as well, the present invention is applied, and each filter element has a curved distribution of material concentration or film thickness.

In the above description, the present invention is applied to a color filter of a liquid crystal display device, but it can also be applied to a color filter or a light emitting layer of other display devices, such as an electroluminescent display device. In this case, if it is a color filter, it will have a structure placed between the light-emitting layer and the display surface, and if it is a light-emitting layer, a light-emitting material is used as the material that gives color characteristics. The brightness distribution characteristic is curved so that the brightness is high in the central part and low in the peripheral part as a curved distribution that changes between the central part and the peripheral part.

"Effects of the Invention" As described above, according to the present invention, each filter element of the color filter has a curved distribution characteristic in which the transmittance or luminance increases in the center and decreases in the periphery. In a display device that uses conventional technology, the separation between adjacent pixels becomes very smooth, improving the quality of the displayed image.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the transmittance distribution and material concentration distribution of a filter element in an embodiment of the present invention, and FIG. 2 is a diagram showing a part of an example in which the embodiment of the present invention is applied to a liquid crystal display device. 3 is a diagram showing an example of the distribution of filter elements of a color filter, FIG. 4 is a sectional view showing a part of a liquid crystal display device to which a conventional color filter is applied, and FIG. 5 is a plan view of the filter element. FIG. 6 is FIG. 2 showing a transmittance distribution of a filter element of a conventional color filter.

Claims (3)

[Claims] (1) Used to display images in color on a display device that displays images by a collection of pixels, and a filter element is provided corresponding to each pixel, and these filter elements are made of a plurality of filter elements with different color characteristics. In a color filter in which these filter elements having different color characteristics are distributed almost uniformly, each filter element of the color filter corresponding to a part or the entire display surface of the display device has a transmittance at the center. A color filter characterized by having a transmittance distribution characteristic in which the transmittance decreases in the upper and peripheral areas, or a brightness distribution characteristic in which the brightness increases in the center and decreases in the peripheral areas. (2) A claim characterized in that the concentration distribution of the material that provides the color characteristics of the filter element is changed between the central part and the peripheral part to obtain the transmittance distribution characteristic or the brightness distribution characteristic. 1. The color filter described in 1. (3) The color filter according to claim 1, wherein the film thickness of the filter element is changed between a central portion and a peripheral portion to obtain the transmittance distribution characteristic or the luminance distribution characteristic.