Liquid Crystal Display Device and Driving Method Thereof

Abstract

To provide a hold-type display device without a problem of motion blur and a driving method thereof. The length of a period for displaying a blanking image in one frame period is controlled in accordance with a control parameter showing the degree of motion blur, and the level of a signal supplied to a display element is changed in accordance with the length of the period for displaying the blanking image. Accordingly, the hold-type display device without a problem of motion blur and the driving method thereof can be provided.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a display device and an operating method of the display device. In particular, the present invention relates to a method for improving quality of a moving image of a hold-type display device.[0003]2. Description of the Related Art[0004]In recent years, there have been growing interests in thin display devices. Liquid crystal displays, plasma displays, projection displays, and the like have been developed and becoming popular instead of CRT displays. Further, field emission displays, inorganic electroluminescence displays, organic electroluminescence displays, electronic paper, and the like have been developed as next-generation display devices.[0005]In a display portion which is provided in the above-described display device, pixels which are minimum units for forming an image are arranged. Each of the pixels emits light with desired luminance by being supplied with a signal generated by...

AI Technical Summary

Benefits of technology

[0021]Although various methods for solving a problem of motion blur in hold-type display devices have been considered, advantageous effects thereof are not sufficient in some cases. In addition, other troubles are increased by using the methods in some cases. For example, a flicker increases in a method in which display is made closer to that of impulsive-type display devices by displaying a black image. In addition, by displaying the black image, luminance of an image decreases compared with the case of not inserting a black image. In that case, in order to obtain luminance which is equal to that of the case of not inserting a black image, it is necessary to increase luminance instantaneously. Accordingly, loads on display devices are increased to decrease reliability or increase power consumption, which becomes problematic.

[0022]In a method of increasing a frame rate, a driver circuit which can process data at high speed is necessary because data processing becomes complicated, so that manufacturing cost increases, heat is generated in accordance with data processing, and power consumption increases, which become problematic. In addition, in a method in which a new image is generated by compensating image data, it is difficult to obtain high-quality compensated image, and on the contrary, quality of a moving image decreases in some cases by displaying an image by insertion of compensated data.

[0023]Further, when the above-described method for solving a problem of motion blur is applied to a liquid crystal display device, there is a problem in that speed during which transmittance of a liquid crystal is change is slow and it is difficult to sufficiently follow change in signals. Furthermore, there is a problem in that degree of light emission of a pixel is changed depending on viewing angles.

[0024]The present invention has been made in view of the foregoing problems. It is an object of the present invention to provide a hold-type display device without a problem of motion blur and a driving method of thereof. It is another object of the present invention to provide a display device with low power consumption and a driving method of thereof. In addition, it is another object of the present invention to provide a display device with improved quality for still images and moving images and a driving method of thereof. Further, it is another object of the present invention to provide a display device with a wider viewing angle and a driving method of thereof. Furthermore, it is an object of the present invention to provide a display device with improved response speed of a liquid crystal and a driving method of thereof.

[0025]One aspect of the present invention is a driving method of a liquid crystal display device in which an image is displayed by applying signal voltage Vi in accordance with an image signal to a liquid crystal element. One frame period is divided into a first subframe period and a second subframe period. When the length of the first subframe period is denoted by τa, first voltage which is applied to the liquid crystal element in the first subframe period is denoted by Va, and second voltage which is applied to the liquid crystal element in the second subframe period is denoted by Vb, the first voltage V1 is determined in accordance with a difference between the second voltage Vb and the signal voltage Vi, and the length of the first subframe period τa. The second voltage Vb is voltage at which the liquid crystal element performs black display.

[0026]Another aspect of the present invention is a driving method of a liquid crystal display device in which an image is displayed by applying signal voltage Vi in accordance with an image signal to a liquid crystal element. The liquid crystal display device includes a backlight. When the length of a backlight lighting period in one frame period is denoted by τa, first voltage which is applied to the liquid crystal element in one frame period is denoted by Va, and initialization voltage which is applied to the liquid crystal element right before one frame period is denoted by V0, the first voltage V1 is determined in accordance with a difference between the initialization voltage V0 and the signal voltage Vi, and the length of the backlight lighting period τa.

Problems solved by technology

Although various methods for solving a problem of motion blur in hold-type display devices have been considered, advantageous effects thereof are not sufficient in some cases.

In addition, other troubles are increased by using the methods in some cases.

Accordingly, loads on display devices are increased to decrease reliability or increase power consumption, which becomes problematic.

In a method of increasing a frame rate, a driver circuit which can process data at high speed is necessary because data processing becomes complicated, so that manufacturing cost increases, heat is generated in accordance with data processing, and power consumption increases, which become problematic.

In addition, in a method in which a new image is generated by compensating image data, it is difficult to obtain high-quality compensated image, and on the contrary, quality of a moving image decreases in some cases by displaying an image by insertion of compensated data.

Further, when the above-described method for solving a problem of motion blur is applied to a liquid crystal display device, there is a problem in that speed during which transmittance of a liquid crystal is change is slow and it is difficult to sufficiently follow change in signals.

Furthermore, there is a problem in that degree of light emission of a pixel is changed depending on viewing angles.

Images