KR101327869B1 - Liquid Crystal Display Device - Google Patents

Abstract

SUMMARY OF THE INVENTION The present invention provides a liquid crystal display device using a field sequential color system that realizes high-speed response. The present invention provides a high speed and high efficiency of driving light, while driving response of a display image formed by combining R, G, and B. In order to obtain a liquid crystal display device that can be improved, a liquid crystal display device using a field sequential color method using ferroelectric liquid crystal, comprising: a data writing period within one frame period and an AC driving period after the data writing period. In the data writing, in synchronism with the lighting periods of the red, green, and blue backlights, a polarized voltage is sequentially applied to generate red, green, and blue display images, and in the AC driving period, the display is performed. The generation of the image is characterized by applying a reverse polarity voltage.

Ferroelectric liquid crystal, field sequential, AC drive period, entry

Description

[0001] The present invention relates to a liquid crystal display device,

1 is an explanatory diagram schematically illustrating assimilation response

2 is an explanatory diagram schematically showing improvement of assimilation response by a high speed drive method;

3 is an explanatory diagram that schematically realizes improvement of assimilation response by black insertion method;

FIG. 4 is a diagram showing a drive sequence in the case where the first drive method with improved moving picture responsiveness is implemented in Embodiment 1 of the present invention;

FIG. 5 is a diagram showing a drive sequence in the case where the second drive method with improved moving picture responsiveness is implemented in Embodiment 1 of the present invention; FIG.

FIG. 6 is a diagram showing a drive sequence in the case where the third drive method with improved moving picture responsiveness is implemented in Embodiment 1 of the present invention; FIG.

7 is a general plan view of a liquid crystal display using ferroelectric liquid crystal

8 is a diagram showing a driving sequence in the case of performing a field sequential color method in a liquid crystal display device using a general ferroelectric liquid crystal;

9 is a view showing a driving sequence in the driving method of a conventional liquid crystal display device for improving the utilization efficiency of light;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a field sequential color method using a ferroelectric liquid crystal (FLC) that realizes high-speed response. In particular, an isotropic, chiral nematic phase, among the ferroelectric liquid crystals, Cholesteric phase) and a ferroelectric liquid crystal having a phase series of Smetic C phase (hereinafter, such liquid crystals are referred to as ferroelectric liquid crystals having a half-V shape) and assimilating light. The present invention relates to a liquid crystal display device that realizes an improvement in responsiveness.

In addition to attractive features such as low power consumption and thinness, liquid crystal displays have a rapid improvement in display performance itself and are widely used in flat panel TVs, portable computers, monitors, and the like. Among such liquid crystal display devices, it is known that ferroelectric liquid crystals using the Smetic C phase have a high-speed response with time constants of 10 kW to 100 kW.

More specifically, when the temperature of a liquid crystal panel filled with a ferroelectric liquid crystal of a half-V shape is lowered from a high temperature, the liquid crystal molecules themselves are projected at a phase transition temperature from a chiral nematic phase (cholesteric phase) to a smear C phase. The components become approximately the same in the orientation treatment direction. However, then two domains occur. Therefore, in order to obtain a single domain, the method of applying DC in the vicinity of phase transition temperature, etc. is proposed. The liquid crystal panel thus obtained retains good image quality and has a feature of responding at high speed.

Such a half-V shape ferroelectric liquid crystal is easy to apply a field sequential color system. Here, in the field sequential color system, full-color display can be obtained by sequentially displaying images of red (R), green (G), and blue (B) in time, and mixing these images in time.

Applying this field sequential method to a liquid crystal display device, the display of the backlight is switched to red, green, and blue in time to light up, and the liquid crystal panel displays an image corresponding to the color lit by the backlight. This can be achieved by being displayed in synchronization.

If the frame period for displaying an image is a normal 60 Hz, a color sequential frequency is required to be 180 Hz, which is three times that of the field sequential color system. However, in the realization of the field sequential color system which requires such a high speed response, the above-described half-V shape ferroelectric liquid crystal excellent in responsiveness is applied.

Hereinafter, a conventional liquid crystal display device will be described with reference to the accompanying drawings.

7 is a general plan view of a liquid crystal display device using a general ferroelectric liquid crystal. By adopting the field sequential color method, it is not necessary to divide the display screen into three divisions of red, green, and blue, and there is a merit that three times higher definition can be realized using the same technique.

However, in ferroelectricity, data display is possible only in the case of polarity voltage on one side due to the characteristics of the liquid crystal oriented as described above, and cannot be displayed in the case of reverse polarity. Therefore, in order to avoid the abnormality of burn-in accompanying a DC application (a phenomenon in which a predetermined part of the panel is burned and pressed and looks like a stamped part), the drive must be driven by AC. In this case, the utilization efficiency of light is weakened to 50%.

Fig. 8 is a diagram showing a driving sequence in the case of realizing a field sequential color system in a liquid crystal display device using a general ferroelectric liquid crystal. As shown in Fig. 8, as a result of the AC driving, the red, green, and blue light on the backlight side contributes only to the display of [Part A], [B Part], and [C Part], respectively. It becomes about 50%.

On the other hand, the drive system which improved the utilization efficiency of light is proposed (for example, refer patent document 1 (Unexamined-Japanese-Patent No. 204-219938)). 9 is a diagram showing a driving sequence in the driving method of a conventional liquid crystal display device for improving the light utilization efficiency.

In this conventional driving method, the data erasing period (corresponding to T2 in FIG. 9) is designed after the data retention period (corresponding to T1 in FIG. 9), and the first data and the reverse polarity voltage are applied. After that, the voltage difference between the pixel electrode and the common electrode is set to 0 V in the reset period (corresponding to T3 in FIG. 9).

By designing the data erasing period T2 and the resetting period T3 in this manner, after increasing the utilization efficiency of the light, it is possible to eliminate the bias of the charge with respect to the liquid crystal, deterioration of the liquid crystal material and burn-in of the liquid crystal panel ( burn-in: A phenomenon in which a certain part of the panel is burned and pressed to look like a painted part can be prevented.

In addition, an impulse driving in which a part of one frame contributes to display can be made, and an improvement in moving picture characteristics can be obtained as compared with a hold type drive that contributes to the display of all periods in a conventional frame. .

However, the above-described conventional techniques have the following problems.

By adopting the conventional driving method, it is possible to improve the utilization efficiency of light and the characteristics of each of R, G, and B images. However, the display image itself is composed of R, G, and B synthesis, and there is a problem that even the moving picture response of the synthesized display image cannot be sufficiently improved.

The present invention has been made to solve the above problems. In the liquid crystal display device using the field sequential color method using a ferroelectric liquid crystal having a half-V shape that realizes high-speed response, the light utilization efficiency is increased at a high speed. SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device capable of improving the drive responsiveness of a display image formed by the synthesis of R, G, and B.

In the liquid crystal display device of the present invention for achieving the above object, in the liquid crystal display device by the field sequential color method using a ferroelectric liquid crystal, the AC drive after the data writing period and the data writing period within one frame period In the data writing, in synchronization with the lighting periods of the red, green, and blue backlights, red, green, and blue display images are sequentially generated in synchronism with the lighting periods of the red, green, and blue backlights. The creation of the display image is the application of a reverse polarity voltage.

In the liquid crystal display device of the present invention, half-V is made possible by using a half-V shape ferroelectric liquid crystal excellent in high-speed response, so that data can be displayed only at one voltage of polarity and almost black at a voltage of reverse polarity. By performing the driving method utilizing the characteristics of the ferroelectric liquid crystal of the shape, the moving picture response can be improved without raising the liquid crystal driving frequency.

Hereinafter, preferred embodiments of the liquid crystal display of the present invention will be described in detail with reference to the accompanying drawings.

Embodiment 1.

First, a method for improving the moving picture response of the liquid crystal display device will be described.

1 is an explanatory diagram in which a moving picture response is realized in a schematic diagram. Specifically, the vertical axis shows time, the horizontal axis shows a place, and the gray screen moves from the left of the black screen.

In the liquid crystal display device, since each pixel performs a hold type display in which transmitted light continues to be emitted during the frame period, when the observer sees it, as shown by the bar at the bottom, the black From the screen to the gray screen, the brightness is shown to change gradually.

In order to improve this, a high speed drive method or a black insertion method is proposed. Fig. 2 is an explanatory diagram schematically showing improvement of moving picture responsiveness according to a high speed driving method. As shown in Fig. 1, the vertical axis shows time, the horizontal axis shows places, and the gray screen moves from the left of the black screen.

In such a high speed drive system shown in FIG. 2, the period in which luminance gradually changes is shortened by using a double drive frequency as compared with the drive system in FIG.

3 is an explanatory diagram schematically showing improvement of assimilation response according to the black insertion method. As shown in Figs. 1 and 2, the vertical axis shows time and the horizontal axis shows places, and the gray screen is moved from the left of the black screen. The black insertion method shown in FIG. 3 uses the same drive frequency as the driving method of FIG. 1, but by inserting a large number of black display periods for the video display periods, pseudo impulse display is performed equivalently. By obtaining the same effect as in the case of raising the frequency, the moving picture response is improved.

Here, as described above, the ferroelectric liquid crystal of the Half-V shape is capable of displaying data only with voltage of one polarity, and has a characteristic of almost black state for the voltage of reverse polarity. Therefore, by utilizing this characteristic, driving of the black insertion method shown in FIG. 3 can be easily realized, and it is possible to improve the moving picture response without raising the liquid crystal drive frequency.

In addition, the liquid crystal display device of the present invention first generates a display image composed of a combination of R, G, and B in one frame period, and then applies a voltage of reverse polarity to that of the display image. It is characterized by realizing drive by AC drive and black insertion system simultaneously. Hereinafter, the driving method of the present invention will be specifically described with reference to the drawings.

Fig. 4 is a diagram showing a drive sequence in the case where the first drive method with improved drive response is implemented in the first embodiment of the present invention. As shown in Fig. 4, one frame period is divided into a data writing period and an AC driving period. Therefore, in this first drive system, first, the display of R, G, and B is successively performed by the voltage of the same polarity in the data writing period. Thereafter, in the AC driving period, corresponding voltages of R, G, and B are applied in reverse polarity to the voltage applied in the data writing period and of the same magnitude.

In this manner, first, in the data writing period, the display image is generated by the R, G, and B signals, and then in the AC driving period, the reverse polarity is applied to drive the display image to AC the display image. In a state where generation is prioritized, abnormalities such as burn-in due to DC application can be eliminated.

In FIG. 4, for convenience, data of R, G, and B written in the pixel are shown as different values. By performing such driving, not only the AC driving but also the same effect as the black data insertion as shown in Fig. 3 described above can be obtained, and as a result, the moving picture responsiveness can be improved. In other words, the AC drive period is achieved at the same time as the AC drive and the black insertion.

FIG. 5 is a diagram showing a drive sequence in the case where the second drive method with improved moving picture responsiveness is implemented in Embodiment 1 of the present invention. In this second driving method, compared with the first driving method shown in Fig. 4, in the data writing period, the reset period (T3R, T3G in Fig. 5) at the time of data writing of R, G, and B is shown. Is equivalent to T3B).

In synchronization with the timing of turning off each backlight contributing to display performance, a reset period for resetting data is inserted. In this way, each data write of R, G, and B becomes a write operation from a constant voltage after data reset, and the stable color display is possible without the influence of hysteresis accompanying the write voltage of previous data.

Fig. 6 is a diagram showing a drive sequence in the case where the third drive method with improved moving response in Embodiment 1 of the present invention is implemented. This third drive method is the same as the first drive method shown in Fig. 4, in which R, G, and B are first displayed, and then the data erasing period is collectively designed. .

As an example, it is considered that the integral value of the applied voltages of R, G, and B and the integral value of the applied voltage of the data erasing period are equal in magnitude and applied so as to be inverted. By designing the collective data erasing period, the AC drive can be achieved, the data write period for the AC drive period can be made longer, the utilization efficiency of the backlight can be increased, and the brightness can be improved.

Also, as shown in Fig. 6, even when the collective data erasing period is designed, as shown in Fig. 5, the reset period (corresponding to T3R, T3G, and T3B in Fig. 5) can be inserted. In this way, it is possible to realize stable color display without the influence of hysteresis accompanying the write voltage of the previous data.

As described below, according to the first embodiment, in a ferroelectric liquid crystal having a half-V shape, one frame period is divided into a data writing period and an AC driving period subsequent thereto, where R, G, After first generating a display image composed of B synthesis, in the AC drive period, both AC drive and black insertion drive can be realized, and the utilization efficiency of light is increased, and the synthesis of R, G, and B is performed. The liquid crystal display device which can aim at the improvement of the moving picture responsiveness of the display image which consists of these is obtained.

In addition, in the AC driving period, the application period of the reverse polarity voltage can be designed not only individually for each of the red, green, and blue display images, but also can be collectively designed together with the light utilization efficiency. It can be improved.

In addition, by designing the reset period in the data write period, each data write of R, G, and B can perform a write operation from a constant voltage after data reset, and influence the hysteresis accompanying the write voltage of the previous data. And stable color display becomes possible.

In addition, the present invention effectively utilizes a feature that enables data display only at one polarity voltage in the case of a ferroelectric liquid crystal having an isotropic, chiral nematic phase (cholesteric phase) and a smear C phase sequence. . As a result, the black display can be inserted without increasing the driving frequency, and the moving picture responsiveness can be improved.

In practice, the present invention can also be applied to field sequential displays using nematic liquid crystals that can display data equally at bipolar voltages. In this case, however, black display is performed with a voltage, and as a result, the driving frequency of the liquid crystal is increased, so that the response of the liquid crystal may not be followed.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Will be apparent to those of ordinary skill in the art.

The liquid crystal display of the present invention as described above has the following effects.

According to the present invention, one frame period is divided into a data writing period and an AC driving period after the data writing period. In the data writing period, a polarized voltage is sequentially applied to generate red, green, and blue display images. In the AC driving period, the use of light in a liquid crystal display device using a half-V shape ferroelectric liquid crystal that realizes high-speed response in a field sequential manner by applying a reverse polarity voltage to generate a display image. A liquid crystal display device capable of improving the efficiency and improving the moving picture response of a display image formed by the synthesis of R, G, and B can be obtained.

Claims (4)

In the liquid crystal display device by the field sequential color method using a ferroelectric liquid crystal, The period of one frame period is divided into a data writing period and an AC driving period after the data writing period, In the data writing, in synchronization with the lighting periods of the red, green, and blue backlights, a polarized voltage is sequentially applied to generate a red, green, and blue display image. In the AC driving period, a reverse polarity voltage is applied to the generation of the display image. The data writing period has a reset period for applying a predetermined reset voltage while sequentially applying respective voltages corresponding to red, green, and blue. In the liquid crystal display device according to claim 1, And the AC driving period is individually designed to correspond to each of the red, green, and blue display images. The method of claim 1, And said AC drive period is designed to collectively designate each of the red, green, and blue display images. delete

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