Display device, and method of operation thereof

• US 8,319,714 B2
• Filed: 12/02/2005
• Issued: 11/27/2012
• Est. Priority Date: 12/22/2004
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kojima, Yu, Tachimura, Yuko, Yamazaki, Shunpei, Tanada, Yoshifumi
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): MISHLER, ROBIN J
• Application Number:
  US11/291,787
• Publication Number:
  US 20060158458A1
• Time in Patent Office: 2,552 Days
• Field of Search: 345/76, 345/690, 345 87-104
• US Class Current: 345/89
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0847 being a dynamic memory without any storage capacitor, i.e. with use of parasitic capacitances as storage elements
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607

Abstract

It is an object of the invention to provide a display device which performs high grayscale display in accordance with display contents and a game machine with an improved realistic sensation. The invention is a display device characterized by including a pixel portion which performs display based on a video signal and a driver circuit portion inputted with the video signal, wherein the driver circuit portion has a unit for controlling a grayscale in accordance with display of the pixel portion. In a liquid crystal display device, luminance of a lighting unit is controlled based on a signal from the unit for controlling a grayscale whereas a current supplied to a light emitting element is controlled in a light emitting device. By applying such a display device to a game machine, a realistic sensation can be improved.

Claims

1. A display device comprising:

a pixel portion having a plurality of pixel electrodes and an opposite electrode with liquid crystal molecules interposed therebetween over a first surface of a substrate, wherein the pixel portion displays an image including at least a white display region and a black or gray display region based on a video signal;

a backlight unit provided on a second surface of the substrate, the backlight unit supplying light to the pixel portion; and

a driver circuit portion comprising a control circuit, the driver circuit portion inputted with the video signal and controls the backlight unit,

wherein in the image, all white display regions are displayed at the highest grayscale with the largest number of grayscale levels and all black display regions are displayed at the lowest grayscale with the smallest number of grayscale levels, and

wherein control circuit comprises;

a determining circuit configured to determine a ratio of the white display region to the black or gray display region based on the video signal;

a converter circuit configured to perform an addition process to raise luminance of the white display region and a subtraction process to decrease luminance of a gray display region based on an output of the determining circuit, and

wherein a controller is configured to supply a signal to lower the greyscale of the gray display region to a signal line driving circuit when a signal to perform a high grayscale display is inputted from the control circuit to a power source of the backlight unit.

2. A game machine using the display device according to claim 1.

3. An electronic device comprising the display device according to claim 1, wherein the electronic device is one selected from the group consisting of a television device, a portable phone and a portable computer.

13. The display device according to claim 1,

wherein the determining circuit is electrically connected to a source line driver circuit through the converter circuit and to a power source of the backlight unit through an amplification signal generating circuit.

17. The display device according to claim 1, wherein angles of the liquid crystal molecules in the gray display region are controlled so as to be more parallel to the substrate when enhancing luminance of the white display region in the image.

21. The display device according to claim 1, wherein the backlight unit comprises a diode which emits white light and a lamp reflector.

4. A display device comprising:

a pixel portion having a plurality of pixel electrodes and an opposite electrode with liquid crystal molecules interposed therebetween over a first surface of a substrate, wherein the pixel portion displays an image including at least a white display region and a black or gray display region based on a video signal;

a backlight unit provided on a second surface of the substrate, the backlight unit supplying light to the pixel portion; and

a driver circuit portion which is inputted with the video signal and controls the backlight unit,

wherein in the image, all white display regions are displayed at the highest grayscale with the largest number of grayscale levels and all black display regions are displayed at the lowest grayscale with the smallest number of grayscale levels,

wherein the driver circuit portion includes a control circuit configured to reduce a voltage value supplied to pixel electrodes in the a gray display region in the image for controlling angles of the liquid crystal molecules in the black or gray display region when enhancing luminance of the white display region in the image by enhancing light emission of the backlight unit, and

wherein a controller is configured to supply a signal to lower the greyscale of the gray display region to a signal line driving circuit when a signal to perform a high grayscale display is inputted from the control circuit to a power source of the backlight unit.

5. A game machine using the display device according to claim 4.

6. An electronic device comprising the display device according to claim 4, wherein the electronic device is one selected from the group consisting of a television device, a portable phone and a portable computer.

14. The display device according to claim 4, further comprising a determining circuit in the driver circuit portion, the determining circuit electrically connected to a power source of the backlight unit, wherein when the determining circuit determines to perform a white display, a signal to enhance the light emission of the backlight unit is inputted to the power source from the determining circuit through an amplification signal generating circuit.

18. The display device according to claim 4, wherein the angles of the liquid crystal molecules in the gray display region are controlled so as to be more parallel to the substrate when enhancing the light emission of the backlight unit.

22. The display device according to claim 4, wherein the backlight unit comprises a diode and a lamp reflector.

7. A display device comprising:

a pixel portion having a plurality of pixel electrodes and an opposite electrode with liquid crystal molecules interposed therebetween over a first surface of a substrate, wherein the pixel portion displays an image including at least a white display region and a black or gray display region based on a video signal;

a backlight unit provided on a second surface of the substrate, the backlight unit supplying light to the pixel portion; and

a driver circuit portion comprising a control circuit, the driver circuit portion inputted with the video signal and controls the backlight unit,

wherein in the image, all white display regions are displayed at the highest grayscale with the largest number of grayscale levels and all black display regions are displayed at the lowest grayscale with the smallest number of grayscale levels, and

wherein the control circuit includes;

a frame memory configured to store the video signal for one frame;

a determining circuit configured to determine a ratio of the white display region to the black or gray display region based on the video signal;

a converter circuit configured to perform an addition process to raise luminance of the white display region and a subtraction process to decrease luminance of a gray display region based on an output of the determining circuit and an amplification signal generating circuit, and

wherein a controller is configured to supply a signal to lower the greyscale of the gray display region to a signal line driving circuit when a signal to perform a high grayscale display is inputted from the control circuit to a power source of the backlight unit.

8. A game machine using the display device according to claim 7.

9. An electronic device comprising the display device according to claim 7, wherein the electronic device is one selected from the group consisting of a television device, a portable phone and a portable computer.

15. The display device according to claim 7,

wherein the determining circuit is electrically connected to a source line driver circuit through the converter circuit and to a power source of the backlight unit through an amplification signal generating circuit.

19. The display device according to claim 7, wherein angles of the liquid crystal molecules in a gray display region are controlled so as to be more parallel to the substrate when enhancing luminance of the white display region in the image.

23. The display device according to claim 7, wherein the backlight unit comprises a diode which emits white light.

10. A display device comprising:

a pixel portion having a plurality of pixel electrodes and an opposite electrode with liquid crystal molecules interposed therebetween over a first surface of a substrate, wherein the pixel portion displays an image including at least a white display region and a black or gray display region based on a video signal;

a backlight unit provided on a second surface of the substrate, the backlight unit supplying light to the pixel portion; and

a driver circuit portion comprising a control circuit, a controller, a signal line driver circuit, and a scan line driver circuit,

wherein in the image, all white display regions are displayed at the highest grayscale with the largest number of grayscale levels and all black display regions are displayed at the lowest grayscale with the smallest number of grayscale levels,

wherein the control circuit is configured to reduce a voltage value supplied to pixel electrodes in a gray display region in the image for controlling angles of the liquid crystal molecules in the gray display region when enhancing luminance of the white display region in the image by enhancing light emission of the backlight unit,

wherein the control circuit includes a frame memory, a determining circuit, a converter circuit, and an amplification signal generating circuit, and

wherein the controller is configured to supply a signal to lower the grayscale of the gray display region to the signal line driver circuit when a signal to perform a high grayscale display is inputted from the control circuit to a power source of the backlight unit.

11. A game machine using the display device according to claim 10.

12. An electronic device comprising the display device according to claim 10, wherein the electronic device is one selected from the group consisting of a television device, a portable phone and a portable computer.

16. The display device according to claim 10, wherein when the determining circuit is electrically connected to the power source of the backlight unit and configured to determine to perform a white display, a signal to enhance the light emission of the backlight unit is inputted to the power source from the determining circuit through the amplification signal generating circuit.

20. The display device according to claim 10, wherein the angles of the liquid crystal molecules in the gray display region are controlled so as to be more parallel to the substrate when enhancing the light emission of the backlight unit.

24. The display device according to claim 10, wherein the backlight unit comprises a diode.