JP2008009042A - Liquid crystal display device and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device on which a favorable white balance can be obtained, and which performs display excellent in color reproducibility. <P>SOLUTION: While having a plurality of scanning signal lines and image signal lines, the liquid crystal display device of this invention makes a liquid crystal panel provided with colored layers in a plurality of colors corresponding to a plurality of sub-pixels select the predetermined scanning signal lines two or more times in one frame period, and writes image signals corresponding to the plurality of colors based on an input image supplied from the image signal lines and dark display signals unrelated to the input image, and selects the sub-pixels corresponding to blue-based sort of colors among the plurality of colors and writes the dark display signals having signal levels of the blue-based sort of colors to the sub-pixels, in the selection of writing the dark display signals among in multiple selections in the one frame period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device and an electronic apparatus.

In recent years, flat panel displays such as liquid crystal display devices (LCD) have been widely used as display devices for computer CRTs and televisions. However, a hold-type display device such as a liquid crystal display device is suitable for displaying still images such as characters because the display state does not change for one frame period. There is a problem of being visually recognized with a blurred outline. Therefore, a plurality of scanning lines of the liquid crystal panel is used as a block, and a backlight corresponding to the block is turned on by sequential pulse driving corresponding to the scanning of the scanning line, thereby realizing a response type (impulse type) display method. There has been proposed a method for reducing blurring of an outline when displaying a moving image (see, for example, Patent Document 1).
JP 2004-157373 A

  By the way, in a liquid crystal display device that performs pseudo-impulse display, in order to improve the display brightness without changing the backlight, in addition to the method of increasing the pixel aperture ratio of the liquid crystal display device to improve the transmittance, color A technique for increasing the transmittance of the filter is mentioned. Among these, the latter method can be brightened only by changing the color filter, and is simple and inexpensive because it is not necessary to greatly change the configuration of the liquid crystal display device. For example, for each of the blue, green, and red color materials constituting the color filter, the ratio of the illumination light that passes through the color filter is increased and the display can be brightened by expanding each transmission wavelength region. However, when a color filter with an expanded transmission wavelength region is used, there is a problem that green light with high visibility becomes too strong, white display is visually recognized as yellow, and display quality is deteriorated.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a liquid crystal display device capable of obtaining a good white balance and capable of displaying with excellent color reproducibility. Yes.

The liquid crystal display device of the present invention includes a plurality of scanning signal lines and image signal lines, and a liquid crystal panel provided with a plurality of colored layers corresponding to a plurality of subpixels. A liquid crystal display device that selects a scanning signal line a plurality of times and writes an image signal corresponding to the plurality of colors based on an input image supplied from the image signal line and a dark display signal unrelated to the input image. In the selection of writing the dark display signal among the plurality of selections in the one frame period, the sub-pixel corresponding to the blue color type is selected from the plurality of colors, and the blue color type is selected. The dark display signal having the signal level is written into the sub-pixel.
That is, the present invention is a pseudo impulse type liquid crystal display device in which an image display period and a display stop period are provided within one frame period, and the display is not black display during the display stop period. Blue display is performed. By displaying blue in the dark display period in this way, the color of the display image can be adjusted. Therefore, even if the white display becomes yellow due to the change of the color filter, the blue color in the dark display period Thus, this yellowness can be corrected, and a liquid crystal display device capable of obtaining a good white display can be obtained. In addition, since the blue color that is difficult to be visually recognized by the user is used as the color displayed during the dark display period, it is possible to obtain the display image quality that is comparable to that when black is inserted and the effect of eliminating the afterimage of the moving image. it can.

  The liquid crystal display device of the present invention includes a plurality of scanning signal lines and image signal lines, and a liquid crystal panel provided with a plurality of colored layers corresponding to a plurality of subpixels. A liquid crystal display device that selects a scanning signal line a plurality of times and writes an image signal corresponding to the plurality of colors based on an input image supplied from the image signal line and a dark display signal unrelated to the input image. In the selection of writing the dark display signal among the plurality of selections in the one frame period, the sub-pixel corresponding to the color type of the shortest wavelength among the plurality of colors is selected and the shortest wavelength is selected. The dark display signal having the signal level of the color type may be written to the sub-pixel. That is, the subpixel driven in the dark display period is not limited to blue as long as it corresponds to the color type on the shortest wavelength side.

  In the liquid crystal display device of the present invention, the signal level of the dark display signal is a signal for driving the sub-pixel corresponding to the blue color type or the shortest wavelength color type included in the image signal in the same frame. The signal level of the component can be the same. With such a configuration, the luminance of blue display in the same frame and the luminance of blue display by blue insertion can be made uniform. Furthermore, since the luminance changes according to the display image, when displaying an image containing a large amount of blue component, it is possible to obtain a vivid display in which the blue color is emphasized. It is possible to effectively prevent color misregistration due to blue insertion.

  In the liquid crystal display device of the present invention, the signal level of the dark display signal may be constant over a plurality of frames. With such a configuration, it is possible to accurately adjust the white balance depending on the illumination unit and the color filter. Moreover, since the display image can be shifted to the blue side as a whole, the vividness of the image visually recognized by the user can be emphasized.

  An electronic apparatus according to the present invention includes the liquid crystal display device according to the present invention described above. According to this configuration, it is possible to realize an electronic device including a display unit that can obtain a good white display and display a high image quality.

  The liquid crystal display device of the present invention is a liquid crystal display device including a drive unit that writes an image signal and a dark display signal to the liquid crystal panel within one frame period. The image display based on the image signal and the dark display with the screen darkened. This is a color liquid crystal display device that enables display operation approximate to the impulse type by sequentially performing the above.

  FIG. 1 is a block diagram showing the entire liquid crystal display device 100 according to an embodiment of the present invention. 2A and 2B are explanatory diagrams of a driving method of the liquid crystal display device 100. FIG. 2A is a plan view showing a display mode of one pixel in a two-frame period, and FIG. 2B shows an operation timing of the liquid crystal panel 110. FIG. FIG. 2C is a plan view showing a display mode of one pixel in the case of the conventional black insertion method.

  The liquid crystal display device 100 includes a color display type liquid crystal panel 110 and a backlight (illumination unit) 91, and includes a data line driving circuit 101 and a scanning line driving circuit 102 mounted on the liquid crystal panel 110. A drive circuit unit 111 including a control circuit 103, a light emission control circuit 104, and an image processing circuit 105 is provided. The liquid crystal panel 110 has an image display area 110a in which a plurality of pixels are arranged in a matrix in a plan view. The pixel includes a plurality of sub-pixels, and each sub-pixel includes one of a plurality of color filters (blue (B), green (G), and red (R)) as shown in FIG. It has become. A data line driving circuit 101 and a scanning line driving circuit 102 are mounted on the edge of the image display area 110a. The data line driving circuit 101 and the scanning line driving circuit 102 are electrically connected to the TFTs (thin film transistors) of the sub-pixels via wirings (data lines, scanning lines). The sub-pixels can be driven independently.

  The display control circuit 103 receives color signals Sb, Sg, Sr corresponding to the respective colors of blue (B), green (G), and red (R) from the outside, performs signal processing on them, and outputs the processed color signals. Sb ′, Sg ′, and Sr ′ are transmitted to the data line driving circuit 101 in the liquid crystal panel 110. Further, the display control circuit 103 transmits a signal for driving the scanning line driving circuit 102 to the scanning line driving circuit 102. The color signals Sb, Sg, and Sr are signals transmitted from electronic devices such as a mobile phone terminal, a portable information terminal, and an IC recorder via a signal line.

  The light emission control circuit 104 causes the light source provided in the backlight 91 to emit light and controls the illumination light supplied to the liquid crystal panel 110. The image processing circuit 105 generates a dark display signal Sd based on the color signal information supplied from the display control circuit 103, and supplies the dark display signal Sd to the liquid crystal panel 110. The display control circuit 103 also supplies a driving signal synchronized with the dark display signal Sd from the image processing circuit 105 to the scanning line driving circuit 102.

  In the liquid crystal display device 100 of the present embodiment, as shown in FIGS. 2A and 2B, pseudo display is performed by performing dark display (blue insertion) within a certain period of each frame. ing. In the “image display” period shown in FIG. 2A, the selection pulse for “image display” shown in FIG. 2B is supplied from the scanning line driving circuit 102 to the scanning line. Further, blue (B), green (G), and red (R) color signals Sb, Sg, and Sr are input to the display control circuit 103 shown in FIG. The color signals Sb ′, Sg ′, and Sr ′ are supplied to the data line driving circuit 101. Then, in synchronization with the “image display” selection pulse supplied to the scanning lines, the color signals Sb ′, Sg ′, Sr ′ are supplied from the data line driving circuit 101 to the data lines, and the image display area is displayed. An image is displayed at 110a.

  On the other hand, in the “blue insertion” period shown in FIG. 2A, the selection pulse for “blue insertion” shown in FIG. 2B is supplied from the scanning line driving circuit 102 to the scanning line. Further, the dark display signal Sd is supplied from the image processing circuit 105 to the data line driving circuit 101. The dark display signal Sd is a color signal Sb ″ for driving only the blue sub-pixel (B) among the three sub-pixels B, G, and R shown in FIG. 2A. In synchronization with the selection pulse for “blue insertion” supplied to the scanning line, the color signal Sb ″ is supplied from the data line driving circuit 101 to the data line, and the image display area 110a receives the signal of the color signal Sb ″. Blue display according to the level.

  In this way, by turning on the blue (B) sub-pixel after the image display, the liquid crystal display device 100 of the present embodiment can perform color adjustment on the display image. In the conventional pseudo impulse display, as shown in FIG. 2 (c), black is displayed (black insertion) together with the image display in one frame period, so the chromaticity of the illumination light supplied from the backlight and the liquid crystal panel The display color depending on the transmission wavelength range of the color filter could not be changed. On the other hand, in the liquid crystal display device 100 of the present embodiment, blue insertion is performed instead of black insertion, so that the color of the display visually recognized by the user includes blue due to blue insertion. Thus, the color of the display image can be adjusted as appropriate. In addition, since a blue color that is difficult to be visually recognized by the user is used as the color displayed during the dark display period, it is possible to obtain the same display image quality as when black is inserted and the effect of eliminating the afterimage of the moving image. it can.

  In addition, if the signal level of the dark display signal Sd is adjusted, the sub-pixels driven during the dark display period can be displayed in an intermediate gradation, so that white balance adjustment by blue insertion can be accurately performed. Thereby, a favorable white display can be obtained, and a liquid crystal display device capable of high-quality display can be obtained.

Here, FIG. 3 is an xy chromaticity diagram for explaining the operation of the liquid crystal display device 100.
In FIG. 3, point C0 is the chromaticity of white light visually recognized as a good white display, and C1 is the chromaticity corresponding to yellowish white light shown as an example. For example, when the illumination light supplied from the backlight 91 is strong in yellow, white light transmitted through the liquid crystal panel 110 and emitted as white light corresponding to the point C1. Become. The spectral characteristics of the backlight 91 can be changed by replacing the light emitting elements provided in the backlight 91 or adjusting the luminance balance among the light emitting elements of a plurality of colors. Increases costs. Therefore, as in this embodiment, if an image display period and a dark display period for displaying blue are provided in one frame, the white balance can be adjusted without changing the configuration of the backlight 91. In addition, a liquid crystal display device capable of high-quality display can be provided at low cost. In the present embodiment, the blue luminance level in the dark display period can be arbitrarily adjusted. Therefore, even if the white balance changes with time, it can be easily corrected by adjusting the level of the dark display signal. There is also an advantage of being able to.

Further, the transmittance of the color filter of the liquid crystal panel 110 may be increased for the purpose of improving the brightness of the liquid crystal display device 100. This will be described below with reference to FIG.
FIG. 4 is a diagram showing the spectral characteristics of the color filter for explaining the operation of the liquid crystal display device 100 together with the spectral characteristics of the backlight. In FIG. 4, the curve shown by the solid line is the spectral characteristic of the blue color filter, green color filter, and red color filter in order from the short wavelength side. Moreover, the curve shown with a broken line has shown the spectral characteristic of the backlight which used LED (light emitting diode) for the light source.

  In order to improve the transmittance of the color filter, for example, the green color filter is changed to a color filter having a wide transmission wavelength region having spectral characteristics shown by a two-dot chain line in FIG. By using a color filter having a wide wavelength range of transmitted light in this way, a component that passes through the color filter in the illumination light incident on the liquid crystal panel 110 can be increased, so that the display becomes brighter. However, on the other hand, since human visibility is the highest in green, the user feels that the green color is stronger than the actual increase in the amount of light, and the white display appears yellowish. . In this embodiment, even in such a case, by performing blue insertion for the dark display period, it is possible to shift the color of the display image to the blue side while maintaining the brightness of the display. An indication can be obtained. Further, when adjusting the deviation of the white balance due to the characteristics of the color filter, the liquid crystal display device 100 can perform the intermediate gradation display for the sub-pixels in the dark display period, so that the white balance is adjusted with high accuracy. be able to.

  Further, in the liquid crystal display device 100, since the luminance of the sub-pixels in the dark display period can be freely adjusted, the signal level of the dark display signal Sd according to the signal level of the blue color signal Sb ′ in the display image in the same frame. Can be adjusted. The coloration of white display due to the change in the transmittance of the color filter is caused by the high visibility of green color. Therefore, the color is colored according to the signal levels of the color signals Sb ′, Sg ′, Sr ′ constituting the display image. The degree of is different. Therefore, when blue display with a constant luminance (for example, maximum gradation) is performed during the dark display period, the signal level of the blue color signal Sb ′ is small, and the signal level of the green color signal Sg ′ or the red color signal Sr ′ is low. In a frame including a large display image, the color of blue may become too strong, causing a color shift in the display image. Therefore, in the present embodiment, the signal level of the dark display signal Sd is preferably set to the same signal level as the blue color signal Sb 'of the display image of the same frame. With such a configuration, since the luminance of the sub-pixels in the dark display period is lowered in a frame with a small blue component included in the display image, it is possible to prevent the above-described problem of color misregistration.

  In this embodiment, the case where the color type to be displayed in the dark display period is blue has been described. However, the color type of the sub pixel that is displayed in the dark display period is not limited to blue. Of these, the color having the shortest wavelength may be used. When the color filter is composed of R (red), G (green), and B (blue), a sub-pixel corresponding to B (blue) is selected during the dark display period and a predetermined luminance (signal level) is selected. ), But when the color filter is composed of Y (yellow), C (cyan), and M (magenta), M (magenta) is used during the dark display period, and the color filters are R (red) and G (green). ), B (blue), and C (cyan or emerald green), a sub-pixel corresponding to B (blue) is selected and written at a predetermined luminance (signal level) during the dark display period. . By selecting the color type in this way, it is possible to prevent the display characteristics of the moving image from being impaired due to the lighting of the sub-pixel in the dark display period.

(Configuration example of liquid crystal display device)
Hereinafter, a specific configuration example of the liquid crystal display device according to the present invention will be described with reference to FIGS.
In each embodiment, description will be made with reference to the drawings. In each drawing, each layer and each member have different scales so that each layer and each member can be recognized on the drawing. is there.

  FIG. 5 is a diagram illustrating a configuration example of the liquid crystal panel 110. FIG. 5A is a schematic plan view of the liquid crystal panel 110, and FIG. 5B is a schematic cross-sectional view of the liquid crystal panel 110 and the backlight 91 at a position along the line AA ′ in FIG. is there. The liquid crystal panel 110 is an active matrix transmissive color liquid crystal panel using amorphous silicon TFTs (Thin Film Transistors) as switching elements.

In the liquid crystal panel 110, a first substrate 22a and a second substrate 22b that are opposed to each other with the liquid crystal layer 32 interposed therebetween are bonded and integrated by a sealing material 23 provided annularly on the peripheral edge of these two substrates. The first substrate 22a constituting the display surface of the liquid crystal panel 110 has a liquid crystal alignment composed of a color filter 25, a common electrode 26a, an alignment film (not shown), and the like on the surface of the substrate body 24a which is a transparent substrate. And a control layer. A polarizing plate 6a is provided on the surface of the substrate body 24a opposite to the liquid crystal layer.
The second substrate 22b arranged on the side opposite to the display surface (the lower surface side in the drawing) is a liquid crystal alignment composed of a pixel electrode 26b, an alignment film (not shown) and the like on the surface on the liquid crystal layer side of the substrate body 24b which is a transparent substrate. And a control layer. A polarizing plate 6b that forms a pair with the polarizing plate 6a of the first substrate 22a is provided on the surface of the substrate body 24b opposite to the liquid crystal layer.

  Between the first substrate 22a and the second substrate 22b constituting the liquid crystal panel 110, granular spacers 29 for maintaining a constant distance (cell gap) between these substrates are dispersedly arranged. The spacer 29 may be a columnar spacer made of a resin layer patterned using a photolithography method. In addition, a retardation plate or an optical compensation plate can be provided between the substrate body 24a and the polarizing plate 6a and between the substrate body 24b and the polarizing plate 6b as necessary.

  The second substrate 22b of the liquid crystal panel 110 is provided with an overhanging portion 24c that projects outward from the first substrate 22a. This overhanging portion 24c is used as a mounting terminal forming region. A wiring pattern (not shown) is formed on the overhanging portion 24c, and the pixel electrode 26b of the second substrate 22b is electrically connected to the wiring pattern of the overhanging portion 24c via a wiring pattern (not shown). The common electrode 26a of the first substrate 22a is also electrically connected to the wiring pattern of the overhanging portion 24c through a wiring pattern and a conductive material (not shown). A data line driving circuit 101 and a scanning line driving circuit 102 for electrically driving the liquid crystal panel 110 are COG mounted on the wiring pattern of the overhanging portion 24c. As a mounting form of the drive circuit, it is needless to say that other forms such as FPC mounting can be adopted besides COG mounting.

The backlight 91 is disposed on the light guide plate 15 made of a transparent resin material, the light source 52 disposed on one end face of the light guide plate 15, and the back side of the light guide plate 15 (the side opposite to the liquid crystal panel 110). And a reflection plate 17.
The light source 52 includes a light emitting element composed of an LED (light emitting diode) or the like. Light emitted from the light emitting element of the light source 52 is introduced into the light guide plate 15 from the side end face of the light guide plate 15 and the light is introduced. The light is emitted as illumination light to the liquid crystal panel 110 side while being reflected by the reflecting plate 17. As a structure of a light emitting element, it can also be set as the structure provided with LED of each color of blue, green, and red other than white LED. In addition, a light diffusion sheet can be attached to the surface of the light guide plate 15 facing the liquid crystal panel 110 as necessary, and a prism sheet may be provided together with the light diffusion sheet or alone.

  FIG. 6 is a plan configuration diagram illustrating a pixel configuration of the liquid crystal display device 100. As shown in FIG. 6, in the display area of the liquid crystal display device 100, a plurality of scanning lines 18a extend in the horizontal direction in the figure, and a plurality of data lines 16 extend in a direction intersecting these scanning lines. is doing. A rectangular area in plan view surrounded by the scanning lines 18a and the data lines 16 is a sub-pixel area. One color filter 25 of the three primary colors is formed corresponding to one sub-pixel region, and one pixel region having the three color filters 25B, 25G, and 25R is formed in the three sub-pixel regions shown in the figure. ing. These color filters 25B, 25G, and 25R are periodically arranged in the display area of the liquid crystal panel 110.

  In each subpixel region, a pixel electrode 26b having a substantially rectangular shape in plan view made of a light-transmitting conductive film such as ITO (indium tin oxide) is provided. The pixel electrode 26b, the scanning line 18a, and the data A TFT 60 is inserted between the line 16. The TFT 60 includes a semiconductor layer 33, a gate electrode 80 a provided on the lower layer side (substrate side) of the semiconductor layer 33, a source electrode 34 provided on the upper layer side of the semiconductor layer 33, and a drain electrode 35. Has been. A channel region of the TFT 30 is formed in a region where the semiconductor layer 33 and the gate electrode 80a face each other, and a source region and a drain region are formed in the semiconductor layers on both sides thereof.

The gate electrode 80 a is formed by branching a part of the scanning line 18 a in the extending direction of the data line 16, and the semiconductor layer 33 and an unillustrated insulating film (gate insulating film) are interposed at the tip of the gate electrode 80 a. It faces the vertical direction of the page. The source electrode 34 is formed by branching a part of the data line 16 in the extending direction of the scanning line 18a, and is electrically connected to the semiconductor layer 33 (source region). One end (left end in the drawing) side of the drain electrode 35 is electrically connected to the semiconductor layer 33 (drain region), and the other end (right end in the drawing) side of the drain electrode 35 is electrically connected to the pixel electrode 26b. ing.
In the above configuration, the TFT 60 is turned on for a predetermined period by a gate signal input via the scanning line 18a, whereby an image signal supplied via the data line 16 is supplied to the liquid crystal at a predetermined timing. On the other hand, it functions as a switching element for writing.

  The liquid crystal panel 110 is not limited to the TFT active matrix type, but may be an active matrix type using a two-terminal nonlinear element such as a TFD (Thin Film Diode) as a switching element. Various known forms such as TN type, VAN type, STN type, ferroelectric type, and antiferroelectric type can be adopted. Alternatively, a transflective liquid crystal display device may be configured by partially forming a reflective layer in a pixel.

(Electronics)
FIG. 7 is a perspective view showing an example of an electronic apparatus according to the present invention. A cellular phone 1300 shown in this figure includes the liquid crystal display device of the present invention as a small-sized display portion 1301 and includes a plurality of operation buttons 1302, an earpiece 1303, and a mouthpiece 1304. The liquid crystal display device of the embodiment is not limited to the mobile phone, but is an electronic book, a personal computer, a digital still camera, a video monitor, a viewfinder type or a direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, It can be suitably used as an image display means for calculators, word processors, workstations, videophones, POS terminals, devices equipped with touch panels, and the like. Alternatively, it can be used as a light valve of a projector. Such an electronic device is excellent in display performance.

1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment. FIG. 6 is an operation explanatory diagram of a liquid crystal display device. FIG. 6 is an operation explanatory diagram of a liquid crystal display device using an xy chromaticity diagram. FIG. 9 is an operation explanatory diagram of a liquid crystal display device using a spectral characteristic diagram. FIG. 6 illustrates a configuration example of a liquid crystal display device. The figure which shows the structural example of a pixel area. FIG. 14 illustrates an example of an electronic device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Liquid crystal display device, 25, 25G, 25B, 25R Color filter, 52 Light source, 91 Backlight, 101 Data line drive circuit, 102 Scan line drive circuit, 103 Display control circuit, 104 Light emission control circuit, 105 Image processing circuit, 110 LCD panel, 111 drive circuit

Claims (5)

A liquid crystal panel provided with a plurality of scanning signal lines and image signal lines and provided with a plurality of colored layers corresponding to a plurality of sub-pixels causes a predetermined scanning signal line to be selected a plurality of times in one frame period. A liquid crystal display device for writing an image signal corresponding to the plurality of colors based on an input image supplied from the image signal line, and a dark display signal unrelated to the input image,
In the selection of writing the dark display signal among the plurality of selections in the one frame period, the sub-pixel corresponding to the blue color type is selected from the plurality of colors, and the signal level of the blue color type is selected. A liquid crystal display device, wherein the dark display signal having the above is written to the sub-pixel. A liquid crystal panel provided with a plurality of scanning signal lines and image signal lines and provided with a plurality of colored layers corresponding to a plurality of sub-pixels causes a predetermined scanning signal line to be selected a plurality of times in one frame period. A liquid crystal display device for writing an image signal corresponding to the plurality of colors based on an input image supplied from the image signal line, and a dark display signal unrelated to the input image,
In the selection of writing the dark display signal among the plurality of selections in the one frame period, the sub-pixel corresponding to the color type of the shortest wavelength among the plurality of colors is selected, and the color type of the shortest wavelength is selected. A liquid crystal display device, wherein the dark display signal having a signal level is written to the sub-pixel.   The signal level of the dark display signal is the same as the signal level of the signal component that drives the sub-pixel of the blue color type or the shortest wavelength color type included in the image signal in the same frame. The liquid crystal display device according to claim 1 or 2.   4. The liquid crystal display device according to claim 1, wherein a signal level of the dark display signal is constant over a plurality of frames. 5.   An electronic apparatus comprising the liquid crystal display device according to claim 1.

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