JPS6048037B2 - Color LCD display panel for TV - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a matrix type color liquid crystal display panel for televisions, and its purpose is to provide a color liquid crystal display panel for televisions with good color balance and contrast. The purpose is to prevent the entire image from appearing colored when viewed.

An example of a television LCD panel is the so-called twisted nematic type (TN), which has an approximately 90-degree twist structure.
The structure of a liquid crystal display panel (type) is as shown in FIG.

1 is a transparent substrate, 2 is a matrix-like electrode, and 3 is a TN type liquid crystal, and the long axis directions of the liquid crystal molecules in contact with the surfaces of each transparent substrate form an angle of approximately 90 degrees with each other and are in a twisted positional relationship.

Reference numeral 4 denotes a pair of polarizing plates, each polarizing direction being substantially parallel or substantially perpendicular to the long axis direction of the liquid crystal molecules in contact with the substrate surface.

In such a structure, the relationship between the light transmittance and the applied voltage (effective voltage) at the part where the electric field is applied is as shown in FIG. The horizontal axis is the applied voltage (effective voltage), and the vertical axis is the light transmittance. Curves 5 and 6 are for cases where the polarization directions of the pair of polarizing plates are parallel and perpendicular to each other, respectively. FIG. 3 is a planar schematic diagram of the matrix electrode of FIG. 1,
The shaded areas are the intersections of the matrix electrodes formed on each substrate. In a television liquid crystal display panel with such a configuration, the effective voltage applied to the liquid crystal in the shaded area shown in Fig. 3 is set to the effective voltage between the sloped parts of the curve shown in Fig. 2. Halftone display is performed. There is a color liquid crystal display panel for television as shown in FIG. 7 is a transparent substrate, 8 is a transparent electrode, 9 is a TN type liquid crystal, and 10 is a pair of polarizing plates whose polarization directions are substantially parallel to each other.

11 is an inorganic thin film color filter located between the liquid crystal and the transparent electrode.

Figure 5 shows the planar overlapping structure of the matrix and matrix electrodes used in Figure 4, with red, blue, and green inorganic thin films running in the row direction between the liquid crystal and the electrodes at the intersections of the matrix electrodes. The filters are formed alternately. Therefore, the three intersections of the matrix electrodes, red, blue, and green, correspond to one pixel of the monochrome liquid crystal display panel. When the television LCD panel shown in Figure 4 is illuminated with white light or natural light from the outside and observed with transmitted light, it is found that when the voltage applied to the liquid crystal at the intersection of the matrix is below the threshold voltage of the liquid crystal, Since the incident light is cut by the polarizing plate on the opposite side, the whole is dark. For each pixel, if you want to observe red color, you can apply a voltage higher than the threshold voltage of the liquid crystal to the liquid crystal in the red filter part to make the liquid crystal stand up against the substrate surface. That is, in one pixel consisting of three intersections, red light is transmitted through only one intersection. If you want to observe blue or green color, you can apply a voltage higher than the threshold voltage to the liquid crystal in the corresponding filter section. If you want to observe other composite colors, you can independently control the tilt of the liquid crystal molecules in the filter parts at the three intersections in each pixel, and the light intensity passing through each color filter will be combined and controlled. Color is observed. The present invention provides a color liquid crystal display panel for television as described above that has good color balance and contrast, and furthermore, prevents the entire panel from appearing colored when viewed as a black and white television.

The present invention will be explained below with reference to Examples. In Figure 2, the ratio between the effective voltage at 90% saturation and the effective voltage at 10% saturation, that is, the ratio between the saturation voltage and the threshold voltage, is approximately 1.5 to 1.5, although there are differences depending on the liquid crystal. It is about 1.7. However, in the case of matrix drive,
When the number of scanning electrodes is several tens, the ratio of the effective voltages applied to the liquid crystal of a selected pixel and the liquid crystal of a non-selected pixel is about 1.1 to 11. Therefore, the effective voltage can only be taken within a range of about 30% to 40% of the slope portion in FIG. In addition, in the case of television image display, it is necessary to divide the effective voltage between the intermediate tones. However, among red, blue, and green, the brightness decreases in the order of green, red, and blue. Therefore, if the transmittance of the red, blue, and green filters is the same, for example, when the video signal is to display white, the effective voltage applied to the liquid crystal corresponding to the green, red, and blue filters is The numbers must be increased in order of 3.
This means that when the maximum effective voltage applied to the liquid crystal corresponding to the blue filter is saturated at about 40% in Figure 2, the maximum effective voltage applied to the liquid crystal corresponding to the red or green filter is is saturated at about 30% or 20%. Furthermore, as mentioned above, it is necessary to divide the effective voltage for halftone display. Therefore, the gap between the effective voltages to be divided to be applied to the liquid crystal corresponding to the green filter becomes very narrow. This is inconvenient with respect to variations in the thickness of the liquid crystal layer or changes in temperature.

FIG. 6 shows an example of the present invention, and shows the transmittance characteristics of each filter alone. 12, 13, and 14 correspond to blue, green, and red filters, respectively.

By changing the transmittance of the filter in this manner, the maximum effective voltage applied to the liquid crystal corresponding to each filter node is unified to the largest value. Therefore, it becomes easy to divide the effective voltage to obtain halftones, and the color balance and contrast are improved. Furthermore, since the effective voltage for halftones is common to each filter, when viewed as a black and white TV,
A common display signal may be applied to the liquid crystal corresponding to each filter. Furthermore, bright greens and reds are not emphasized, and the entire image does not appear colored. Although the present invention has been described with respect to a television display panel, it is clear that the present invention can be applied to other color liquid crystal displays.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a liquid crystal display panel. 1...Transparent substrate. 2...Matrix electrode. 3...TN type liquid crystal. 4... A pair of polarizing plates. Figure 2 shows the relationship between applied voltage and light transmittance. 5...
When the polarization direction is flat. 6...When the polarization direction is perpendicular. Figure 3 is an example of a matrix electrode. FIG. 4 is a sectional view of the display panel. 7...Transparent substrate. 8...Transparent electrode. 9...TN type liquid crystal. 10... A pair of polarizing plates. 11... Inorganic thin film color filter. FIG. 5 is a plan view of the relationship between matrix electrodes and color filters. FIG. 6 shows the transmittance characteristics of each filter in an example of the present invention. 12...Blue filter. 13...Green filter. 14...Red filter.

Claims (1)

[Claims] 1 Consists of a transparent substrate with transparent electrodes formed in a matrix, a liquid crystal layer with an approximately 90-degree twisted structure installed between the substrates, a pair of polarizing plates, red, blue, and green filters corresponding to each pixel, etc. 1. A color liquid crystal display panel for television, characterized in that the transmittance of the red, blue, and green filters is decreased in the order of blue, red, and green.