Color display device

• US 20050243047A1
• Filed: 04/20/2005
• Published: 11/03/2005
• Est. Priority Date: 04/28/2004
• Status: Abandoned Application

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Asao, Yasufumi
• Application Number:
  US11/109,757
• Publication Number:
  US 20050243047A1
• Time in Patent Office: Days
• US Class Current: 345/88
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 3/207 by domain size control G09G3/3637 takes precedence
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/2077 by a combination of two or more gradation control methods
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals

Abstract

One unit pixel is constituted by a subpixel a provided with a red color filter and a subpixel b at which green and blue are displayable in an electrically controlled birefringence (ZCB) mode. The subpixel b is provided with a cyan color filter to increase color purity. As a result, with respect to red, it is possible to effect continuous halftone display. With respect to green and blue, it becomes possible to effect stepwise or continuous halftone display in an areal gradation mode. By the use of the cyan color filter, it is possible to effect green display at a low voltage.

Claims

1. A color display device of the type wherein a display unit is constituted by a plurality of pixels each comprising a first subpixel and a second subpixel, and at each subpixel, a medium for changing an optical property depending on an externally applied voltage is provided,

wherein at the second subpixel, a red color filter is disposed,

wherein the medium changes the optical property within a brightness-changing voltage range in which light passing through the medium changes brightness while assuming achromatic color and a hue-changing voltage range in which the light passing through the medium assumes chromatic color and changes hue of the chromatic color, and

wherein a voltage in the hue-changing voltage range is applied to at least a part of the first subpixel, and a voltage in the brightness-changing voltage range is applied to the second subpixel, thereby to effect color display on a display unit basis.

2. A device according to claim 1, wherein to the first subpixel, a voltage at which the light passing through the medium assumes blue, green, and their intermediary chromatic color is applied.

3. A device according to claim 1, wherein the first subpixel is provided with a color filter of a color complementary to the color of the red color filter, and a voltage in the hue-changing voltage range is applied to the first subpixel to display a color obtained by color mixing of the chromatic color with the color complementary to the color of the color filter.

4. A color display device of-the type comprising:

at least one polarization plate;

a pair of substrates provided with oppositely disposed electrodes; and

a liquid crystal layer, disposed between the substrates, for changing a retardation depending on a voltage applied between the electrodes, wherein a display unit is constituted by a plurality of pixels each comprising a first subpixel and a second subpixel;

wherein at the second subpixel, a red color filter is disposed,

wherein the liquid crystal changes the optical property within a brightness-changing voltage range in which light passing through the liquid crystal changes brightness while assuming achromatic color and a hue-changing voltage range in which the light passing through the medium assumes chromatic color and changes hue of the chromatic color, and

wherein a voltage in the hue-changing voltage range is applied to at least a part of the first subpixel, and a voltage in the brightness-changing voltage range is applied to the second subpixel, thereby to effect color display on a display unit basis.

5. A device according to claim 4, wherein the first subpixel is provided with a color filter of a color complementary to the color of the red color filter, and a voltage in the hue-changing voltage range is applied to the first subpixel to display a color obtained by color mixing of the chromatic color with the color complementary to red.

6. A device according to claim 5, wherein to the first subpixel, a voltage providing a retardation of approximately 750 nm is applied, thus effecting display of green.