JP6775983B2 - How to drive the liquid crystal display - Google Patents

Description

The present invention relates to a method for driving a liquid crystal display device.

A conventional liquid crystal display device that obtains a color image by arranging red, green, and blue filters for each pixel in the horizontal or vertical direction separates red, green, and blue for each pixel when the image is viewed through a lens with a large magnification. There was a problem that the image quality was significantly deteriorated. In order to solve this problem, a field sequential method that displays images for one screen in red, green, and blue in time division is attracting attention. By adopting field sequential, the expected color can be expressed with one pixel, so it is particularly suitable for monitors of professional cameras that require high definition.

However, in a field sequential type liquid crystal display device in which the display time of one frame is short with respect to the response speed of the liquid crystal, the transmittance or reflectance of light following the voltage applied to the liquid crystal cannot be obtained within the time of one frame. Therefore, there is a problem that color mixing occurs between frames, resulting in an image with low saturation. As one of the means for solving the problem, a driving method for improving the response speed of the liquid crystal in the frame by writing predetermined precharge data to all the pixels in advance before displaying one frame has been proposed. (See, for example, Patent Document 1).

FIG. 2 is an example of a timing chart showing a conventional driving method of a liquid crystal display device. The drive method shown in FIG. 2 is a conventional drive method in which predetermined precharge data is written to all pixels in advance. In this drive method, image data of N frames is written to all pixels in line sequence in the first half of N frames. A pixel data writing period 4 is provided, a pixel data holding period 5 for holding image data is provided in the latter half of the N frame, and an all-pixel access period 1 for performing a precharge operation for the N + 1 frame in the latter half of the pixel data holding period 5. Is provided. In the all-pixel access period 1, a voltage (2.5V) that is 1/2 of the maximum voltage applied to the pixels in the N + 1 frame is always written to all the pixels as constant precharge data. Further, the N + 1 frame is provided with a pixel data writing period 4 and a pixel data holding period 5 in the first half and the second half, respectively, as in the N frame, and a pre for the N + 2 frame (not shown) in the latter half of the pixel data holding period 5. An all-pixel access period 1 for performing a charging operation is provided. In this driving method, since predetermined precharge data (2.5V) is written to all pixels in the all pixel access period 1 of the N frame, the response speed of the liquid crystal in the N + 1 frame can be improved by that amount. it can.

Japanese Unexamined Patent Publication No. 2000-162577

In the conventional driving method shown in FIG. 2, since a constant voltage is always written to all pixels as precharge data, the saturation of the displayed image is sufficiently reduced, especially when the response speed of the liquid crystal is slow. There is a problem that it cannot be prevented.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display device capable of preventing a decrease in saturation in a displayed image.

This is a method of driving a liquid crystal display device provided with a liquid crystal panel, in which precharge data corresponding to the frame is written to all the pixels of the liquid crystal panel at a timing prior to one frame for displaying an image. Then, the average voltage value of the image data written to the pixels in the frame is compared with the intermediate voltage value between the predetermined maximum voltage value and the minimum voltage value of the image data, and the average voltage value is the intermediate. When it is smaller than the voltage value, the value obtained by multiplying the average voltage value by a value selected from 0.5 to 0.9 is determined as the voltage value of the precharge data, and the above-mentioned When the average voltage value is larger than the intermediate voltage value, the value obtained by multiplying the average voltage value by a value selected from 1.1 to 1.5 is the voltage of the precharge data. It is a driving method of the liquid crystal display device determined as a value .

According to the present invention, since the voltage of the precharge data can be optimized, it is possible to effectively prevent the decrease in saturation in the displayed image.

An example of a timing chart showing a driving method of a liquid crystal display device in the present invention. An example of a timing chart showing a conventional driving method of a liquid crystal display device

INDUSTRIAL APPLICABILITY The present invention is a liquid crystal display device provided with a liquid crystal panel in which a liquid crystal is enclosed between a pair of substrates in which a plurality of pixel electrodes and counter electrodes are provided on surfaces facing each other. The feature is that the charge data is not written to all the pixels of the liquid crystal panel, but the precharge data is calculated based on the image information (brightness, etc.) of the frame so that the optimum liquid crystal response speed can be obtained and written to all the pixels. It is said. Hereinafter, specific examples of the present invention will be described.

FIG. 1 is an example of a timing chart showing a driving method of the liquid crystal display device in the present invention. In the case of a liquid crystal display device that operates in a normal white mode using a TN liquid crystal, the voltage applied to the liquid crystal is the minimum (0V) in the N frame shown in FIG. 1, and a white image having a transmittance of 100% is displayed. It will be. Further, in the case of the field sequential type liquid crystal display device, the red (R) image is displayed in the N frame shown in FIG. 1, the green (G) image is displayed in the next N + 1 frame, and the next N + 2 frame ( In (not shown), a blue (B) image is displayed, and one color image is displayed by these three images.

In this embodiment, first, the average voltage value (2V) of one frame of image data to be written to all pixels (pixel electrodes) in the next N + 1 frame at a timing prior to the all-pixel access timing 1 of the N frame shown in FIG. ), In other words, find the average brightness of the image. Next, the obtained average voltage value (2V) is compared with the intermediate voltage value (2.5V) of the image data, and when the average voltage value (2V) is smaller than the intermediate voltage value (2.5V), The average voltage value (2V) is multiplied by 0.9, and the value (1.8V) obtained by this is written as precharge data 9 in all pixels in the all pixel access period 1 of the N frame. The voltage applied to the liquid crystal is the difference between the voltage applied to the counter electrode and the voltage applied to the pixel. In this case, the precharge data of 1.8 V is more liquid crystal than the case of 2.5 V (intermediate voltage value). A high voltage (3.2V) is applied to the voltage, which is closer to the average voltage value (3V) applied to the liquid crystal in the N + 1 frame. Therefore, the response speed of the liquid crystal in the N + 1 frame can be improved by that amount as compared with the conventional technique in which the precharge data is 2.5 V (intermediate voltage value).

The value (multiplier) to be multiplied by the average voltage value of the image data is not limited to 0.9, and when the average voltage value of the image data is smaller than the intermediate voltage value, for example, a multiplier of 0.5 to 0.9 is used. When selected and the average voltage value of the image data is larger than the intermediate voltage value, for example, a multiplier of 1.1 to 1.5 is selected. That is, the voltage of the precharge data written in the pixel in the N frame is higher or lower than the average voltage value by about 10 to 50% depending on the magnitude of the average voltage value of the image data written in the pixel in the N + 1 frame. It changes to become.

It is a well-known fact that the response speed of the liquid crystal increases as the applied voltage increases, and a higher voltage is applied to the liquid crystal during the all-pixel access period 1 of the N frame before the image data is written to the pixels in the N + 1 frame. By doing so, it is possible to make the liquid crystal easy to move when the image data is written in the N + 1 frame.

In particular, in this embodiment, by writing a voltage that is about 10% higher than the average voltage value of the image data of the N + 1 frame as precharge data to all the pixels in the all pixel access period 1 of the N frame, the liquid crystal in the N + 1 frame The response speed of is improved.

In this embodiment, the precharge data is determined based on the average voltage value of the image data of the N + 1 frame, but it is also possible to determine the precharge data based on other information contained in the image data of the N + 1 frame. is there. Further, the present invention can be applied not only to a liquid crystal display device using a TN liquid crystal display but also to a liquid crystal display device using another liquid crystal such as a ferroelectric liquid crystal display. Further, the present invention is not limited to the field sequential type liquid crystal display device, and can be applied to other drive type liquid crystal display devices.

1 All pixel access period 4 Pixel data writing period 5 Pixel data retention period 9 Precharge data

Claims (1)

It is a driving method of a liquid crystal display device provided with a liquid crystal panel, in which precharge data corresponding to the frame is written to all pixels of the liquid crystal panel at a timing prior to one frame for displaying an image. hand,
The average voltage value of the image data written to the pixel in the frame is compared with the intermediate voltage value between the predetermined maximum voltage value and the minimum voltage value of the image data.
When the average voltage value is smaller than the intermediate voltage value, the value obtained by multiplying the average voltage value by a value selected from 0.5 to 0.9 is the value of the precharge data. Determined as a voltage value,
When the average voltage value is larger than the intermediate voltage value, the value obtained by multiplying the average voltage value by a value selected from 1.1 to 1.5 is used as the precharge data. Determined as a voltage value,
A method of driving a liquid crystal display device.

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