JP2007206230A - Flat panel display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which is reducible in power consumption. <P>SOLUTION: A liquid crystal panel 11 has a plurality of pixels 15 arrayed in a matrix. Each pixel 15 has pixel electrodes 16R, 16G, 16B, and 16W for red, green, blue, and white and also has a circuit block 17 which writes signals to the respective pixel electrodes 16R, 16G, 16B, and 16W. The circuit block 17 compares levels of the respective input signals for red, green, and blue. A signal having a level corresponding to the smallest level is written to the pixel 16W for white. Signals for red, green, and white from which the level of the signal written to the pixel electrode 16W for white is subtracted are written to the corresponding pixel electrodes 16R, 16G, and 16B. With a light output of white containing light components of red, green, and blue, respective light outputs for red, green, and blue are decreased to reduce the power consumption. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flat display device having a plurality of pixels.

  Conventionally, a liquid crystal display device, which is a flat display device of this type, has been widely used in notebook personal computers and the like because of its low power consumption, and has also been used for monitor applications and television applications. Yes.

  In portable devices typified by notebook personal computers, battery operation is required, and it is important that the battery life is long. In recent years, with the advancement of functions, the power consumption of components constituting devices has been increasing, and among them, the demand for low power consumption for liquid crystal display devices with relatively large power consumption tends to increase.

  In order to reduce the power consumption of this liquid crystal display device, attempts have been made to improve the aperture ratio of the liquid crystal, improve the light utilization factor of the backlight, and reduce the power consumption of the liquid crystal driver.

  In the liquid crystal display device, a plurality of pixels are provided in a matrix on a glass substrate, and each pixel generally has sub-pixels for red, green, and blue. By the way, each of the red, green and blue sub-pixels actually outputs light of each color with the backlight light by providing a color filter. However, the color filter does not have 100% transmittance and absorbs light of green and blue components when outputting red light, so it is 30% at best, in fact about 23% light. It only penetrates. For this reason, there is a problem that the luminance is low and the image quality is low especially in the liquid crystal television and monitor applications.

Therefore, a configuration is known in which luminance is improved by adding one white sub-pixel that does not use a color filter to each pixel and simultaneously turning on the red, green, blue, and white sub-pixels. (For example, refer to Patent Document 1).
Japanese Patent Laying-Open No. 2005-62869 (page 6-7, FIG. 1-3b)

  However, as described above, in order to reduce the power consumption of the liquid crystal display device, methods such as improving the aperture ratio of the liquid crystal, improving the light utilization factor of the backlight, and reducing the power consumption of the driver of the liquid crystal have been tried. However, further reduction of power consumption is required.

  Also, luminance can be improved by adding one white subpixel that does not use a color filter to each pixel and simultaneously turning on the red, green, blue, and white subpixels. However, the power consumption cannot be reduced, and there is a problem that the power consumption increases as the white sub-pixels are driven simultaneously.

  The present invention has been made in view of these points, and an object thereof is to provide a flat display device capable of reducing power consumption.

  The present invention provides a plurality of pixels each having a pixel electrode for a first color, a second color, and a third color corresponding to the three primary colors of light and a pixel electrode for white, and driving of each of these pixels The first color signal, the second color signal, and the third color signal are input for use, and a signal having a predetermined intensity is written to the white pixel electrode and the signal to be written to the white pixel electrode And a drive circuit for writing the signals for the first color, the second color, and the third color having the intensity obtained by subtracting the intensity to the corresponding pixel electrodes.

  According to the present invention, the signals for the first color, the second color, and the third color are input to the drive circuit, the predetermined intensity signal is written to the pixel electrode for white, and the signal for white is used. Since the signals for the first color, the second color, and the third color obtained by subtracting the intensity of the signal written to the pixel electrode are written to the corresponding pixel electrode, the first color corresponding to the three primary colors of light With the white light output including the color, second color, and third color components, it is possible to reduce the light output of the first color, the second color, and the third color, thereby reducing power consumption.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In FIG. 1, reference numeral 11 denotes a liquid crystal panel as a flat display device, and the liquid crystal panel 11 is an active matrix type liquid crystal display device (LCD).

  The liquid crystal panel 11 includes a substantially rectangular flat array substrate 12 that is an active matrix substrate. The array substrate 12 has a glass substrate 13 as an insulating substrate having a substantially transparent rectangular flat plate shape and translucency.

  A screen portion 14 as an image display region is formed in the central portion on the surface which is one main surface of the glass substrate 13. A plurality of pixels 15 are arranged in a matrix on the screen portion 14 on the glass substrate 13. A pixel electrode 16 is disposed on each of the plurality of pixels 15. The pixel electrode 16 of each of the pixels 15 is for the first color corresponding to the three primary colors of light, red for the red subpixel, for the second color, for green which is the green subpixel, and for the third color. Each pixel electrode 16R, 16G, 16B for blue, which is a blue sub-pixel, and one white sub-pixel corresponding to each pixel electrode 16R, 16G, 16B There are three pixel electrodes 16W for each. Each of the pixel electrodes 16R, 16G, and 16B is arranged in a longitudinally long rectangular shape in plan view with a predetermined interval in the width direction, and each pixel electrode 16W has a smaller area than each of the pixel electrodes 16R, 16G, and 16B. The pixel electrodes 16R, 16G, and 16B are juxtaposed at positions close to one end side in the longitudinal direction.

  Each pixel 15 is electrically connected to each pixel electrode 16R, 16G, 16B, 16W, and each has a circuit block 17 as a drive circuit that controls signal writing to each pixel electrode 16R, 16G, 16B, 16W. One by one. These circuit blocks 17 input red, green, and blue signals for driving the pixels 15, write signals of a predetermined intensity to the white pixel electrode 16W, and also to the white pixel electrode 16W. It has a function of writing red, green, and blue signals obtained by subtracting the intensity of the signal to be written into the corresponding pixel electrodes 16R, 16G, and 16B. Specifically, the intensity of each input signal for red, green and blue is compared, and a signal having the intensity corresponding to the minimum intensity is written to the pixel electrode 16W for white and the pixel electrode 16W for white The red, green, and blue signals, which are obtained by subtracting the intensity of the signal written to, are written to the corresponding pixel electrodes 16R, 16G, and 16B. When writing a signal having the intensity corresponding to the minimum intensity to the pixel electrode 16W for white, since there are three pixel electrodes 16W for white, a signal obtained by dividing the intensity corresponding to the minimum intensity into three equal parts is used for white. Write to each pixel electrode 16W. In addition, when a signal divided into three equal parts with the intensity corresponding to the minimum intensity is written to each pixel electrode 16W for white, a signal is applied to the pixel electrode 16R, 16G, 16B corresponding to the signal with the minimum intensity. Instead of writing, the signal may be written only to the signal corresponding to the signal other than the minimum intensity.

  In addition, a plurality of scanning lines 21 which are gate electrode wirings as electrode wirings are arranged on the surface of the glass substrate 13 along the width direction of the glass substrate 13. These scanning lines 21 are arranged between the respective pixels 15 in the vertical direction so as to be spaced in parallel at equal intervals in the vertical direction of the glass substrate 13. Further, on the surface of the glass substrate 13, a plurality of signal lines 22 that are image signal wirings as electrode wirings are arranged along the vertical direction of the glass substrate 13. These signal lines 22 correspond to the vertical direction pixels 15, the red signal line 22R as the first signal line, the green signal line 22G as the second signal line, and the blue signal as the third signal line. One line 22B is provided, and is arranged in the gap region on one side of each of the pixel electrodes 16R, 16G, and 16B of each pixel 15 so as to be spaced in parallel at equal intervals in the horizontal direction of the glass substrate 13. Accordingly, the scanning lines 21 and the signal lines 22 are wired in a matrix shape that is in a lattice shape so as to intersect perpendicularly on the glass substrate 13.

  The circuit block 17 of each pixel 15 is electrically connected to the scanning line 21 and the signal line 22, that is, each signal line 22R, 22G, 22B.

  In addition, a Y driver circuit (not shown) as a scanning line driving circuit electrically connected to one end of each scanning line 21 is disposed on the periphery of the glass substrate 13, and each signal line 22 is provided. An X driver circuit (not shown) is disposed as a signal line driving circuit electrically connected to one end of each.

  On the other hand, on the surface of the array substrate 12, a rectangular flat plate-like counter substrate (not shown) is disposed so as to face the array substrate 12. The counter substrate includes a glass substrate as a substantially transparent rectangular flat plate-like insulating substrate having translucency. A color filter layer as a colored layer is laminated and provided on the surface which is one main surface of the glass substrate facing the array substrate 12. This color filter layer is configured by repeatedly arranging three dots of a red red layer, a green green layer, and a blue blue layer in the vertical and horizontal directions of the counter substrate. The color filter layer is provided so as to be opposed to each pixel electrode 16R, 16G, 16B of each pixel 15 of the array substrate 12 when the counter substrate is opposed to the array substrate 12. The array substrate 12 is provided so as not to face the white pixel electrodes 16W of the pixels 15 of the array substrate 12.

  Further, on the surface of the color filter layer of the counter substrate, a rectangular flat counter electrode which is a common electrode as a common electrode is laminated. This counter electrode is formed of an ITO film as a transparent electrode. The counter electrode is a large rectangular electrode facing the entire screen portion 14 of the glass substrate 13 of the array substrate 12 when the surface of the counter substrate and the surface of the array substrate 12 are opposed to each other. . Further, a liquid crystal sealing region having a predetermined interval is formed between the array substrate 12 and the counter substrate, and a liquid crystal composition having a positive dielectric anisotropy as a liquid crystal material is formed in the liquid crystal sealing region. Is injected and sandwiched to form a liquid crystal layer as a light modulation layer.

  In addition, a backlight (not shown) is arranged as a planar light source body that illuminates by irradiating planar light from the rear surface side that is the array substrate 12 side of the liquid crystal panel 11. The backlight has a light guide plate made of, for example, an acrylic substantially rectangular flat plate, and a light source (not shown) such as a cold cathode lamp or a light emitting diode is disposed so as to face the incident surface of the side of the light guide plate. Has been. On the surface of the light guide plate facing the liquid crystal panel 11, a light emitting surface from which light incident from the light source into the light guide plate is emitted is formed.

  Next, the operation of the liquid crystal display device will be described.

  The circuit block 17 of each pixel 15 is driven by the Y driver circuit and the X driver circuit.

  Each circuit block 17 receives red, green and blue signals from the X driver circuit through the signal lines 22, that is, the signal lines 22R, 22G and 22B.

  In each circuit block 17, the intensities of the input signals for red, green and blue are compared, and the signal having the smallest intensity is detected. A red signal obtained by subtracting the intensity of the minimum intensity signal written to the white pixel electrode 16W, and writing the intensity signal corresponding to the minimum intensity, which is divided into three equal parts, into each pixel electrode 16W for white. , Green and blue signals are written to the corresponding pixel electrodes 16R, 16G and 16B. Among the white pixel electrodes 16W and the pixel electrodes 16R, 16G, and 16B, the one to which the signal is written is turned on according to the intensity of the signal.

  FIG. 2 shows the light output of each color in one pixel 15. FIG. 2 (a) shows the light output in the case of not displaying white, and shows the light output in the conventional case, and each of the pixel electrodes 16R, 16G, red subpixel, green subpixel, and blue subpixel, A signal is written to 16B, and red, green, and blue light outputs are output.

  In FIG. 2A, since the red light output is the lowest, that is, the intensity of the signal applied to the red subpixel is the smallest, a signal having an intensity corresponding to this minimum intensity signal is applied to the pixel electrode 16W which is a white subpixel. FIG. 2B shows the result of writing and writing each intensity signal obtained by subtracting the intensity corresponding to the minimum intensity signal to the pixel electrodes 16R, 16G, and 16B, which are the red subpixel, the green subpixel, and the blue subpixel. An optical output such as

  Since the white sub-pixel contains all red, green, and blue light components, as shown by the broken line in FIG. 2 (b), the light output of each of the red, green, and blue components is equivalent only with the white light output. Therefore, by adding the green and blue light outputs indicated by the solid lines in FIG. 2B, substantially the same light output as in FIG. 2A can be obtained.

  In this way, the intensities of the red, green and blue signals input to the circuit block 17 are compared, and a signal having the intensity corresponding to the minimum intensity is written to the white pixel electrode 16W, and the white White that includes red, green, and blue light components to write the red, green, and blue signals to the corresponding pixel electrodes 16R, 16G, and 16B after subtracting the intensity of the signal written to the pixel electrode 16W With the display, it is possible to reduce the power consumption by reducing the signals written to the pixel electrodes 16R, 16G, and 16B for red, green, and blue for the plurality of pixels 15. In addition, a desired display color can be obtained, luminance can be improved, and a screen with a sharp edge can be obtained.

  By the way, each of the red, green, and blue sub-pixels actually outputs light of each color by providing a color filter. However, the color filter does not have 100% transmittance, and the red color is red. When the above light is output, light of green and blue components is absorbed, so that only 30% or less of light of 23% is actually transmitted. However, since such a color filter is not used in the white subpixel, 100% light can be used. Therefore, for example, a lower-brightness backlight is sufficient to obtain the same luminance as the conventional one, and the power consumption of the light source of the backlight can be reduced.

  Therefore, it is possible to reduce power consumption by reducing signals written to the pixel electrodes 16R, 16G, and 16B of the plurality of pixels 15, and to reduce power consumption of the light source of the backlight, thereby reducing power consumption of the entire liquid crystal display device. It can be reduced sufficiently. That is, the white light output including red, green, and blue light components can reduce the red, green, and blue light outputs, thereby reducing the power consumption of the liquid crystal display device.

  Further, since the circuit block 17 is provided in each pixel 15, it can be dealt with by simply applying the same signal as before to each pixel 15 without performing complicated image conversion outside.

  In addition, one pixel electrode 16W for white is provided corresponding to each of the pixel electrodes 16R, 16G, and 16B for red, green, and blue, so that the white subpixels can be dispersedly arranged in the pixels 15. Therefore, it is possible to prevent concentration and unevenness of luminance, and by reducing the intensity of signals written to the pixel electrodes 16R, 16G, and 16B, it is possible to cope with a decrease in light output from the red, green, and blue sub-pixels. The light output from the white subpixel can be supplemented.

  The circuit block 17 receives the red, green, and blue signals described above, writes a signal having a predetermined intensity to the white pixel electrode 16W, and outputs a signal to be written to the white pixel electrode 16W. When the first mode is to write the signals for red, green, and blue with the intensity subtracted to the corresponding pixel electrodes 16R, 16G, and 16B, for the input red, green, and blue The second mode is a mode in which each signal is written to the corresponding pixel electrodes 16R, 16G, and 16B, and an average value signal of the red, green, and blue signals is written to the white pixel electrode 16W. It is possible to switch between the first mode and the second mode.

  In this case, the array substrate 12 is provided with a mode switching signal line as a fourth signal line, and a signal is input from the X driver circuit to the circuit block 17 through the mode switching signal line. In this circuit block 17, switching between the first mode and the second mode is controlled by the input of a signal.

  This second mode displays red, green, and blue subpixels in the same manner as in the past, and additionally displays white subpixels based on the average value of the red, green, and blue signals. The brightness of white can be increased. In this way, when a part of the screen is white, it is possible to increase the peak luminance by only a part of the screen by switching to the second mode. Therefore, a screen with high brightness and sharpness can be realized without increasing the power consumption of the backlight.

  Further, in each of the above embodiments, the signal of the predetermined intensity written to the white pixel electrode 16W is compared with the intensity of each of the input red, green and blue signals, and the intensity corresponding to the minimum intensity However, it may be the same as the minimum intensity, less than the minimum intensity, or greater than the minimum intensity, and can be appropriately set according to obtaining a desired light output.

  One pixel electrode 16W for white is provided corresponding to each of the pixel electrodes 16R, 16G, and 16B. However, one pixel electrode 16W may be provided, or two or four or more may be used.

  Further, although red, green, and blue are used as the three primary colors of light, other three primary colors of light such as cyan, magenta, and yellow can be used in the same manner.

  Also, the liquid crystal panel 11 has been described. However, other than the liquid crystal panel 11, a flat panel display display device such as an SED (Surface-conduction Electron-emitter Display) or a PDP (Plasma Display Panel) is used. Even a flat display device can be used correspondingly.

It is a partial explanatory view of a flat display device showing an embodiment of the present invention. The explanatory drawing of the light output of each color in one pixel of a flat display apparatus same as the above is shown, (a) is explanatory drawing when not displaying white, (b) is explanatory drawing when displaying white.

Explanation of symbols

11 Liquid crystal panel as a flat panel display
15 pixels
16R, 16G, 16B, 16W pixel electrodes
17 Circuit block as drive circuit

Claims (5)

A plurality of pixels each having a pixel electrode for a first color, a second color, a third color and a pixel electrode for white corresponding to the three primary colors of light;
For driving each of these pixels, the signals for the first color, the second color, and the third color are input, and a signal of a predetermined intensity is written into the white pixel electrode, A drive circuit for writing the signals for the first color, the second color, and the third color having the intensity obtained by subtracting the intensity of the signal written to the pixel electrode to each corresponding pixel electrode. A flat display device. The drive circuit compares the intensities of the input signals for the first color, the second color, and the third color, and writes a signal having an intensity corresponding to the minimum intensity to the white pixel electrode. The signals for the first color, the second color, and the third color obtained by subtracting the intensity of the signal written to the white pixel electrode are written to the corresponding pixel electrodes. 1. A flat display device according to 1. The drive circuit writes the input signals for the first color, the second color, and the third color to the corresponding pixel electrodes, and for the first color, the second color, and the second color. 3. The flat display device according to claim 1, further comprising: a mode in which a signal of an average value of the signals for the three colors is written to the white pixel electrode, and the mode can be switched. 4. The flat display device according to claim 1, wherein one drive circuit is provided for each pixel. 5. 5. The pixel electrode for white is provided for each of the pixel electrodes for the first color, the second color, and the third color. Or a flat display device.

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