Liquid crystal display device

• US 6,313,890 B1
• Filed: 07/12/2000
• Issued: 11/06/2001
• Est. Priority Date: 07/16/1999
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Advanced Display Technologies
• Inventors: Tamatani, Akira
• Primary Examiner(s): Dudek, James A.
• Application Number:
  US09/614,733
• Time in Patent Office: 482 Days
• Field of Search: 349/65, 349/61
• US Class Current: 349/61
• CPC Class Codes: G02F 1/133371 Cells with varying thickness of the liquid crystal layer
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]

Abstract

The present invention is directed to a liquid crystal display including: an active matrix liquid crystal display element; and a surface light source; the liquid crystal display element including a liquid crystal substance sandwiched between an electrode substrate and an counter substrate via alignment films; the electrode substrate having a surface formed with a matrix of pixel portion having switching elements surrounded by a plurality of image signal lines and scanning signal lines; wherein a transmittance distribution of the liquid crystal display element reduces a brightness distribution inconsistency in the surface light source; or more specifically; wherein Xmax is a maximum brightness value in a display region of the surface light source, Xmin is a minimum brightness value thereof, Zmax is a maximum brightness value of the liquid crystal display, and Zmin is a minimum brightness value thereof; and wherein the expression of Xmax/Xmin>Zmax/Zmin is satisfied.

Claims

1. A liquid crystal display comprising:

an active matrix liquid crystal display element; and

a surface light source;

the liquid crystal display element including a liquid crystal substance sandwiched between an electrode substrate and an counter substrate via alignment films;

the electrode substrate having a surface formed with a matrix of pixel portion having switching elements surrounded by a plurality of image signal lines and scanning signal lines;

wherein with Xmax being a maximum brightness value in a display region of the surface light source, Xmin a minimum brightness value thereof, Zmax a maximum brightness value of the liquid crystal display, and Zmin a minimum brightness value thereof, an expression of

2. The liquid crystal display of claim 1, wherein with Xmax being a maximum brightness value in a display region of the surface light source, Xmin a minimum brightness value thereof, Zmax a maximum brightness value of the liquid crystal display, and Zmin a minimum brightness value thereof, an expression of

3. The liquid crystal display of claim 1, wherein with Δ

d being a difference between a maximum value and minimum value of a liquid crystal layer thickness, the expression

4. The liquid crystal display of claim 3, wherein with an orientation direction of the liquid crystal near the electrode substrate differs by 90 degrees from an orientation direction of the liquid crystal near the counter substrate, the electrode substrate and the counter substrate being placed between two polarizers, the polarizers on the electrode substrate side and the counter substrate side having an absorption axis in a direction equal to or differing by 90 degrees from the orienting direction of the liquid crystal;

and wherein d1 is the liquid crystal thickness corresponding to a region of the highest brightness in the surface light source, d2 is the liquid crystal thickness in a region of the lowest brightness thereof, Δ

n is a refraction anisotropy of the liquid crystal, and λ

being a wavelength, the expressions of

5. The liquid crystal display of claim 3, wherein a liquid crystal display element has a comb-like shaped electrode;

wherein d1 is liquid crystal thickness corresponding to a region of the highest brightness in the surface light source, d2 is liquid crystal thickness in a region of the lowest brightness thereof, a maximum electric voltage applied to the liquid crystal layer is lower than an electric voltage for achieving the maximum transmittance when the liquid crystal thickness is d2, and the expression

6. The liquid crystal display of claim 1, wherein the brightness value at a center portion of the surface light source is highest, with the brightness value decreasing toward a perimeter region.

7. The liquid crystal display of claim 1, wherein the transmittance distribution of the liquid crystal display element is determined by a transmittance of the counter substrate.

8. The liquid crystal display of claim 7, wherein the transmittance of the counter substrate is determined by an opening ratio of the counter substrate.

9. The liquid crystal display of claim 7, wherein the counter substrate has a surface formed with a color layer for color display, the transmittance of the counter substrate is determined by the color layer.

10. The liquid crystal display of claim 9, wherein the counter substrate has the surface formed with the color layer for color display, the transmittance of the color layer is controlled by mixing non-transparent particles like carbon into the color layer.

11. The liquid crystal display of claim 1, wherein the liquid crystal display element has a transmittance distribution determined by an opening ratio of the electrode substrate.

12. The liquid crystal display of claim 1, wherein a layer controlling the transmittance is provided on a viewer'"'"'s side or on a side away therefrom, for controlling the transmittance of the liquid crystal display element.

13. The liquid crystal display of claim 1, wherein the electrode substrate has an electrode construction for generation of an electric field generally in parallel to the substrates.

14. A liquid crystal display of claim 1,

the electrode having a comb-like construction, the electric field generally parallel to the substrates being generated for in-plane drive of the liquid crystal molecules;

wherein with L1 being an inter-electrode gap of the comb-like shaped electrode corresponding to a region of the highest brightness of the surface light source, L2 being an inter-electrode gap of the comb-like shaped electrode corresponding to a region of the lowest brightness thereof;

an expression of