JP2589567B2 - Liquid crystal display - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device that obtains an image by sequentially supplying grayscale data to a driver corresponding to a pixel arrangement of a liquid crystal panel.

FIG. 5 shows a conventional full-color liquid crystal display device. The color television signal selected by the tuner 11 is supplied as an intermediate frequency signal to the IF amplified video detection circuit 12, where it is subjected to the intermediate frequency amplification and then video detected. The detection output is demodulated by a chroma demodulation circuit 13 into red gradation data R, green gradation data G, and blue gradation data B and supplied to an RGB switching circuit 14. A synchronization signal is selected from the detection output of the IF amplified video detection circuit 12 by the synchronization control circuit 15, and RG is selected by the synchronization control circuit 15.
The B switching circuit 14 is controlled, and the red gradation data, the green gradation data, and the blue gradation data are sequentially extracted in the order of the pixel arrangement of the color liquid crystal panel 16 and
It is supplied to the driver 17. A Y driver 18 composed of a shift register is controlled by a horizontal synchronization signal from a synchronization control circuit 15, and a color liquid crystal panel 16 is driven line-sequentially to obtain a color image.

"Problems to be Solved by the Invention" As described above, the conventional color liquid crystal display device does not perform temperature compensation, so that a wide temperature environment, for example, -15 ° C
When used at + 55 ° C., the liquid crystal luminance-applied voltage characteristic changes due to a temperature change, and as a result, there is a disadvantage that the display luminance also changes. FIG. 6 shows an example of a change in the liquid crystal luminance depending on the actually measured temperature. In the same figure, when performing full-color display, the gradation level is from 98HEX (2V) to D
It can be obtained by controlling in the range of 8HEX (7V), that is, the transition region of the liquid crystal luminance. Therefore, if the liquid crystal luminance-applied voltage characteristic changes due to the temperature change, the gradation level also changes, and the liquid crystal luminance-gradation level characteristic becomes, for example, as shown in FIG. In other words, even if the liquid crystal luminance-gray level characteristic is set to be linear at + 20 ° C., the gray level changes due to a temperature change.

An object of the present invention is to provide a liquid crystal display device in which display luminance does not change over a wide temperature range.

According to the present invention, the temperature of the liquid crystal panel is detected by the temperature sensor, one of the plurality of applied voltage correction tables is selected according to the detected output, and the selected applied voltage is selected. The correction table is read out using digital gradation data, and the read data is converted into an analog signal by a D / A converter and supplied to a driver of a liquid crystal panel. The plurality of applied voltage correction tables are for correcting the gradation data so that the liquid crystal luminance-gradation data characteristics are almost the same regardless of the temperature change.

FIG. 1 shows an embodiment of the present invention. Digital color gradation data is generated by the CPU 21 and the data is stored in the video RAM.
Stored at 22. The video RAM 22 is controlled by the display control circuit 23 so that red gradation data, green gradation data, and blue gradation data are sequentially read out in the pixel arrangement order of the color liquid crystal panel 16. The gradation data read from the video RAM 22 is, for example, 4 bits and is supplied to the applied voltage correction table 24 as an address.

On the other hand, the temperature of the color liquid crystal panel 16 is detected by the temperature sensor 25, and the detection output is converted into a digital signal by the A / D converter 26. This digital signal is converted into a table selection signal by the CPU 21 and supplied to the applied voltage correction table 24 as an address. Applied voltage correction table 24
Has a plurality of tables, one of which is selected by a table selection signal, and the selected table is read out as gradation data.

The applied voltage correction table 24 includes, for example, four tables as shown in FIG.
Is 50 ℃ ≦ T, + 20 ℃ ≦ T <+ 50 ℃, 0 ℃ ≦ T <+ 20 ℃,-
One table is selected by a table selection signal according to any one of 15 ° C. ≦ T <0 ° C. Each table stores 8-bit correction data for each level of the gradation data, and the corresponding correction data is read based on the gradation data. According to the correction data, each correction data is selected such that the liquid crystal luminance-gradation data characteristics are linear as shown in FIG. 3 and substantially the same regardless of the temperature of the liquid crystal panel. I have. The correction data shown in FIG.
This is a case where the characteristics shown in the figure are corrected.

In FIG. 1, the correction data read from the applied voltage correction table 24 is converted into an analog signal by the D / A converter 27 and supplied to the X driver 17. As described above, since the gradation data is corrected according to the temperature and supplied to the X driver 17, the relationship between the liquid crystal luminance and the gradation level is kept constant even if the temperature changes.

Next, an example in which the present invention is applied to a device for displaying an analog color television signal is shown in FIG. 4 by attaching the same reference numerals to portions corresponding to FIG. RGB switching circuit 14
The serial data of the red gradation data, the green gradation data, and the blue gradation data output from the A / D converter 28 is converted into 4-bit digital data by the A / D converter 28, and the applied voltage correction table 24
Is supplied as an address. The output of the temperature sensor 25 is A /
The data is directly converted into a data selection signal by the D converter 26 and supplied to the applied voltage correction table 24 as an address. One table is selected according to the detected temperature, the gradation data is corrected by the selected table, and the D / A converter 27 is selected.
Supplied to The analog signal converted by the D / A converter 27 is supplied to the X driver 17.

In the above description, the present invention is applied to a color liquid crystal display device, but can also be applied to a black and white liquid crystal display device.

[Effects of the Invention] As described above, according to the present invention, by providing the applied voltage correction table and correcting the gradation data according to the temperature, it is possible to obtain a display in which the luminance does not change over a wide temperature range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing a specific example of an applied voltage correction table, and FIG. 3 is a liquid crystal luminance-gradation level characteristic using the temperature of the present invention as a parameter. FIG. 4 is a block diagram showing another embodiment of the present invention. FIG. 5 is a block diagram showing a conventional color liquid crystal display device.
FIG. 7 is a liquid crystal luminance-gradation level characteristic diagram in which the temperature of the conventional device is used as a parameter.

Claims (1)

(57) [Claims] 1. A liquid crystal display device which obtains an image by sequentially supplying grayscale data to a driver in accordance with a pixel arrangement of a liquid crystal panel, comprising: a temperature sensor for detecting a temperature of the liquid crystal panel; A plurality of applied voltage correction tables which are selected in response to which digital grayscale data is given as addresses and from which correction data is read, and wherein the correction data read from these applied voltage correction tables are converted into analog signals and converted into analog signals. D / to supply to
A liquid crystal display device comprising an A converter, wherein the correction data is selected so that the applied voltage correction table has substantially the same liquid crystal luminance-gray level characteristic regardless of a temperature change.