JP4623947B2 - Display driving method for liquid crystal display device - Google Patents

Description

  The present invention relates to a display driving method of a liquid crystal display device in a field sequential system.

  In a liquid crystal display device, a method of performing color display using a monochrome (single color) liquid crystal cell having no color filter has been proposed as a field sequential display driving method. FIG. 5 shows an example of such a display driving method.

  In the case shown in FIG. 5, the display pattern of the liquid crystal display unit is composed of segment 1, segment 2, and segment 3 having the shapes of A, B, and C, and the light source colors are R (red), G (green), and B (blue). ) Is used, and each light source color is displayed through the liquid crystal when the liquid crystal is on (ON) or off (OFF).

  That is, the light sources of three colors R, G, and B are caused to emit light sequentially, and the liquid crystal is turned on and off in accordance with the light emission timing of the corresponding light source. By sequentially driving them at high speed, it can be expressed as a plurality of colors are displayed even on a monochrome liquid crystal by human eyes.

A specific driving method will be described with reference to FIG. Y represents yellow (yellow), C represents cyan, M represents magenta, and W represents white.
Drive 4a; R for segment 1, G for segment 2, and B for segment 3.
Drive 4b; Y for segment 1, C for segment 2, and M for segment 3.
Drive 4c; W for segment 1, C for segment 2, and M for segment 3.

  By performing such driving, it is possible to perform color display in a monochrome liquid crystal, but the above method is a display with additive color mixing by high-speed driving except for the emission color, and color separation appears to occur instantaneously. Color break phenomenon is likely to occur. For this reason, color display by new arbitrary color light emission shown in FIG. 6 has been proposed (see, for example, Patent Document 1). As a result, the occurrence of the color break phenomenon is suppressed, and display of an arbitrary color is facilitated.

A specific driving method will be described with reference to FIG.
Drive 5a: R is displayed in segment 1, G is displayed in segment 2, and B is displayed in segment 3.
Drive 5b; Y for segment 1, C for segment 2, and M for segment 3.
Drive 5c; W for segment 1, C for segment 2, and M for segment 3.

Here, in both of the above-described two driving methods, it is necessary to perform display with a driving cycle that is more than the extent that human eyes cannot recognize the switching. The driving cycle in which the human eye cannot recognize the switching is about 16.5 ms or more. Assuming that the cycle for repeated display is one frame, it is necessary to arrange a segment as a subframe in the driving method 1 in FIG. 5 and a color in the driving method 2 in FIG.
JP 2001-108960 A

  By the way, in the driving method 2 described above, the length of each subframe is usually fixed, but the light emission power differs depending on the light emission color characteristics of the light source. For this reason, a brightness difference will occur depending on the display color.

  As a specific example, when using LED elements in which R, G, and B LED chips are contained in one package, even when the absolute maximum rating of each LED forward current is 25 mA, There is a restriction that 50% of the absolute maximum rating of the forward current is 30% at the time of simultaneous lighting of three colors, and that the forward current of the absolute maximum rating at the total current must not be exceeded.

  Therefore, even when the maximum rating of forward current is 25 mA each for light emission in R, G, B single colors, R • G (Y) display, G • B (C) display, R • B (M) display, etc. In the case of two-color display, a forward current of 7.5 mA is generated as a limitation of the LED element.

  For this reason, the light emission of the mixed color light emission is lower than that of the single color light emission, the contrast difference is increased, and the display quality is lowered.

  The present invention has been made paying attention to the above problems, and in a field sequential driving method, a display driving method for a liquid crystal display device in which the contrast of the entire display is improved and the deterioration of display quality is suppressed. It is intended to provide.

A display driving method of a liquid crystal display device according to the present invention is a multi-chip package LED element in which a plurality of LED chips of different emission colors are housed in one package, and the multi-chip package LED element performs simultaneous lighting. wherein a multi-chip package LED device variation of the rated current is generated in response to the LED chip number, with a back lighting unit having the multi-chip package LED element as a light-emitting element on the back side of the liquid crystal cell, a plurality by the overall control unit Display color signals are sequentially output , the LED drive unit sequentially emits light including a mixed color of the plurality of light emitting elements by the display color signal, and the liquid crystal drive unit by the display color signal causes the liquid crystal cell of the liquid crystal display unit to perform on-off operation, and sequentially emit light on-off operation of the liquid crystal cell line synchronization of the plurality of light emitting elements Is a display driving method for a liquid crystal display device, the a plurality of light emitting element and the frame cycle for repeatedly driving the liquid crystal cell, when the period for emitting driving each light-emitting element within the frame and subframe, the a plurality of said in one frame period to repeatedly drive the liquid crystal cell and the light emitting element performs source light transmission operation of the back lighting unit in the following sub-frame period of each pixel is one of the liquid crystal cell, LED emit light simultaneously A display driving method for a liquid crystal display device, characterized in that the LED chip is driven with a predetermined difference in the length of the sub-frame when light is emitted from the LED chip according to the number of chips .

  In addition, the subframe length is changed according to the display color, and the ratio of the subframe length is sequentially changed according to the brightness difference of the display color.

  According to the present invention, in the field sequential driving method, there is an effect that the contrast of the entire display is improved and the deterioration of display quality can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings.

  The present invention improves the overall display contrast in the driving method 2 shown in FIG. In the driving method 2, the time of each subframe is displayed uniformly, but in the present invention, the time of the subframe is made variable without changing the frame period by the combination of the light emission colors.

  FIG. 1 schematically shows a configuration of a liquid crystal display device according to the present invention. In the figure, 1 is a control unit for controlling the entire display, 2 and 3 are a liquid crystal drive unit and an LED drive unit, and the liquid crystal drive unit 2 drives a liquid crystal (LCD) cell 5 of the liquid crystal display unit 4 and an LED drive unit. 3 drives a backlight unit 6 having R, G, and B light sources of the liquid crystal display unit 4.

  This liquid crystal display device includes a backlight unit 6 having a plurality of LEDs (light emitting elements) of different emission colors (here, three colors of R, G, and B) on the back side of the liquid crystal cell 5, and has a plurality of display colors. A signal is sequentially output to drive the plurality of LEDs and the liquid crystal cell 5 in synchronization. The sub-frame length for driving each LED within one frame of a cycle in which the three color LEDs and the liquid crystal cell 5 are repeatedly driven. Is driven with a predetermined difference.

  Further, the subframe length is changed according to the display color, and the ratio of the subframe lengths is sequentially changed according to the brightness difference between the display colors.

A specific driving method will be described with reference to FIG. The configuration of the display pattern is the same as that shown in FIG.
Drive 1a: R is displayed in segment 1, G is displayed in segment 2, and B is displayed in segment 3.
Drive 1b: Y is displayed in segment 1, G is displayed in segment 2, and B is displayed in segment 3.
Drive 1c: W is displayed in segment 1, G is displayed in segment 2, and B is displayed in segment 3.

  Further, even in the case of emitting light in accordance with the power difference of the light source in monochromatic light emission, display quality can be improved by changing each period of the subframe as needed.

A specific driving method will be described with reference to FIG.
Drive 2a: R is displayed in segment 1, G is displayed in segment 2, and B is displayed in segment 3.
Drive 2b: W is displayed in segment 1, G is displayed in segment 2, and B is displayed in segment 3.
Drive 2c; W for segment 1, G for segment 2, and M for segment 3.

Here, a confirmation example in the above-described embodiment will be described with reference to FIG. This figure shows a case where W is displayed for segment 1, G for segment 2, and B for segment 3.
Drive 3a; frame period 16.5 ms, each subframe is 5.5 ms.
Drive 3b; with a frame period of 16.5 ms, W: G: B is 6.5 ms: 5.0 ms: 5.0 ms in each subframe.

  By switching the subframe length ratio according to the display color as in the drive 3b, the brightness of the W is higher than that of the drive 3a, the brightness of G and B is lowered, the contrast of the entire display is improved, and the deterioration of display quality is suppressed. it can.

  In this way, by driving the display color in conjunction with the time of the subframe, it is possible to reduce the contrast difference of each display, improve the display quality, and realize a color display using monochrome liquid crystal that is easy to recognize. it can.

  Table 1 shows an example in which the frame period is 16.5 ms and the simultaneous display colors are three colors. In frame 1, R (5.5 ms) is displayed in segment 1, G (5.5 ms) is displayed in segment 2, B (5.5 ms) is displayed in segment 3, and W (6.5 ms) is displayed in segment 1 in frame 2. , G (5.0 ms) is displayed in segment 2, and B (5.0 ms) is displayed in segment 3. In frame 3, R (5.0 ms) is displayed for segment 1, W (6.5 ms) is displayed for segment 2, B (5.0 ms) is displayed for segment 3, and Y (5. 5 ms), W (6.0 ms) is displayed in segment 2, and B (5.0 ms) is displayed in segment 3.

  Here, an example in which the above-described subframe length is displayed with a difference will be described. In this case, when the reference subframe length is set to 5.5 ms, it is desirable that subframe 1: subframe 2: subframe 3 = 1: 1.3: 1.2.

Moreover, when displaying by changing the subframe length by the display color (lightness), when the reference sub Boeuf frame length was 5.5ms, R: G: B = 1: 1: 1, W: G: B = It is desirable that 1.2: 0.9: 0.9 and W: Y: B = 1.1: 1.05: 0.85.

Further, as an example of the case where the subframe length ratio is sequentially changed due to the brightness difference of display colors when simultaneous display is performed while changing the color combination, when the reference subframe length is 5.5 ms, R: G : B = 1: 1: 1, W: G: B = 1.2: 0.9: 0.9, G: W: B = 0.9: 1.2: 0.9, Y: W: B = 1.05: 1.1: 0.85 is desirable.

  The present invention can be widely used in information processing devices that perform color display and liquid crystal display devices of other electrical and electronic devices.

The block diagram which shows the structure of the liquid crystal display device which concerns on this invention Explanatory drawing which shows the drive method of Example 1. FIG. Explanatory drawing which shows the drive method of Example 2. FIG. Explanatory drawing showing a confirmation example of the example Explanatory drawing which shows the drive method of the prior art example 1. Explanatory drawing which shows the drive method of the prior art example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control part 2 Liquid crystal drive part 3 LED drive part 4 Liquid crystal display part 5 Liquid crystal cell 6 Back illumination part

Claims (3)

A multi-chip package LED element in which a plurality of LED chips of different emission colors are housed in one package, and the multi-chip package LED element varies in rated current according to the number of LED chips that are simultaneously lit. a multi-chip package LED device, said multi-chip back lighting unit having a package LED element as a light-emitting element provided on the back side of the liquid crystal cell, a plurality of display color signals by the overall control unit are sequentially output, the display color signals Accordingly, the LED driving unit sequentially emits light including a mixed color of the plurality of light emitting elements , and the liquid crystal driving unit performs ON / OFF operation of the liquid crystal cell of the liquid crystal display unit according to the display color signal, and the plurality of light emitting elements sequentially. the on-off operation of the light emitting and the liquid crystal cell a display driving method of a liquid crystal display device are synchronized,
Wherein the plurality of the periods repeatedly driving the light emitting element and the liquid crystal cell and the frame, when the period for emitting driving each light-emitting element within the frame and subframe, repeatedly driving the liquid crystal cell and said plurality of light emitting elements Within one frame of the cycle, each pixel of the liquid crystal cell performs the light source light transmission operation of the back illumination unit for one subframe period or less, and causes the LED chips to emit light according to the number of LED chips that emit light simultaneously. A display drive method for a liquid crystal display device, wherein the subframe length is driven with a predetermined difference.   2. The display driving method for a liquid crystal display device according to claim 1, wherein the subframe length is changed in accordance with the display color.   2. The display driving method for a liquid crystal display device according to claim 1, wherein the ratio of the subframe lengths is sequentially changed in accordance with the brightness difference of display colors.

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