Reflection liquid crystal display apparatus

• US 7,388,569 B2
• Filed: 12/09/2002
• Issued: 06/17/2008
• Est. Priority Date: 12/10/2001
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Inoue, Mitsuo, Yoshida, Shigeyuki, Yamamoto, Takashi, Agari, Masafumi, Sakamoto, Takao
• Primary Examiner(s): Tran; Henry N
• Application Number:
  US10/496,948
• Publication Number:
  US 20050067553A1
• Time in Patent Office: 2,017 Days
• Field of Search: 345/102, 345/207, 345/690, 349/61, 349/68, 349/106, 349/110, 362/561
• US Class Current: 345/102
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/133616 Front illuminating devices
• CPC Class Codes: G02F 1/133618 for ambient light
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night
• CPC Class Codes: G02F 1/13454 Drivers integrated on the active matrix substrate G02F1/136277 takes precedence
• CPC Class Codes: G02F 2201/58 Arrangements comprising a monitoring photodetector
• CPC Class Codes: G02F 2203/02 reflective
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: H01L 27/1251 comprising TFTs having a different architecture, e.g. top- and bottom gate TFTs

Abstract

A reflective liquid crystal display device is integrated with a liquid crystal display panel (1), detects display surface illuminance by a plurality of light sensors (10) provided in the vicinity of the display surface, and in accordance with the detection result, controls luminous intensity of a front light (lighting means) (19) using a lighting control circuit (22) so that the display surface illuminance becomes a predetermined magnitude. Even if the use environment of the reflective liquid crystal display device changes, or more specifically, intensity of external light shone from outside of the device into the display surface varies, the configuration allows controlling automatically the amount of emission from the front light to automatically maintain an appropriate display luminance and to reduce electric power consumption.

Claims

1. A liquid crystal display device comprising:

a liquid crystal display panel having a display surface and producing a display by reflecting light incident through said display surface;

lighting means located at a front side of said display surface for irradiating light illuminating the front side of said display surface;

light-detecting means for detecting illumination of said display surface by ambient light and by light irradiated by said lighting means, said light-detecting means being located proximate said display surface; and

lighting control means for controlling luminous intensity of said lighting means through feedback control that reduces difference between the illumination of said display surface detected by said light-detecting means and an externally input light control target.

2. The liquid crystal display device according to claim 1, further comprising an array substrate on which is located pixel matrix including a plurality of pixels, each pixel having a reflecting electrode, on an insulating substrate, wherein said light-detecting means is located proximate said pixel matrix on said array substrate.

3. The liquid crystal display device according to claim 2, wherein:

said pixel matrix comprises a thin film transistor for controlling application of voltage applied to a liquid crystal;

said thin film transistor is polycrystalline silicon; and

a photodetector of said light-detecting means is amorphous silicon.

4. The liquid crystal display device according to claim 3, further comprising a resistor on said array substrate and connected in series with said photodetector, as a serially connected pair of components, wherein:

a first potential is supplied to a first end of said serially connected pair of components and a second potential is supplied to a second end of said serially connected pair of components; and

an electric potential at a connection point between said photodetector and said resistor, varying in accordance with illuminance at a light incident portion of said photodetector, is output as the illumination of said display surface that is detected.

5. The liquid crystal display device according to claim 4, wherein:

nonlinearity of the potential at the connection point of said photodetector and said resistor with respect to detection of the illumination of said photodetector is corrected; and

the luminous intensity of said lighting means is controlled in accordance with the non-linearity that is corrected.

6. The liquid crystal display device according to claim 2, further comprising a color filter substrate having an area with a marginal portion corresponding to said display surface and including a black matrix layer, and constituting, in combination with said array substrate, a liquid crystal cell, wherein:

said light-detecting means is located on said array substrate where said array substrate corresponds to said marginal portion where said black matrix layer is located; and

a portion where the black matrix layer is not present at a position corresponding to a light incident portion of a photodetector of said light-detecting means.

7. The liquid crystal display device according to claim 2, further comprising a color filter substrate having an area with a marginal portion corresponding to said display surface and including a black matrix layer, and constituting, in combination with said array substrate, a liquid crystal cell, wherein:

said light-detecting means is located on said array substrate where said array substrate corresponds to said marginal portion where said black matrix layer is located; and

a light incident portion of a photodetector is located at a gap between said display-surface and said black matrix layer.

8. The liquid crystal display device according to claim 1, wherein said lighting control means is controlled within a controllable range of said lighting control means to keep the illumination of said display surface substantially constant.