Liquid crystal display unit

• US 4,945,350 A
• Filed: 04/13/1989
• Issued: 07/31/1990
• Est. Priority Date: 07/09/1985
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kawamura, Yasukazu
• Primary Examiner(s): Brier, Jeffery A.
• Application Number:
  US07/338,383
• Time in Patent Office: 474 Days
• Field of Search: 340/765, 340/784, 350/345, 350/334, 362/27, 362/31
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• 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 2330/06 Handling electromagnetic interferences [EMI], covering emitted as well as received electromagnetic radiation
• 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

Abstract

A liquid crystal display unit comprising a liquid crystal display panel and a light source for illuminating the display panel with uniform brightness sufficient for identifying characters and images in a dark or dim place. The light source may be a combination of at least one fluorescent lamp and a light-guiding member, a single meandering fluorescent lamp, or a single fluorescent lamp having a zigzag discharge path. Thermal-pressure-welding type flexible cables connect the display panel with an electric driving circuit therefor. A light source having more thickness than five millimeters is incorporated with the liquid crystal display unit.

Claims

1. A liquid crystal display unit for displaying characters and/or images comprising:

a liquid crystal display panel including a liquid crystal interposed between first and second transparent plates, a first polarizing plate disposed on the upper surface of said first transparent plate, and a second polarizing plate disposed on the rear surface of said second transparent plate;

a substrate carrying an electric circuit for driving said liquid crystal display panel;

means for interconnecting said electric circuit and said liquid crystal display panel;

a planar light source disposed between said liquid crystal display panel and said substrate and comprising two linear fluorescent lamps and a light guiding member, said light guiding member comprising a light guiding plate extending substantially in parallel with said liquid crystal display panel and disposed substantially in a first plane, said linear fluorescent lamps being disposed at opposite side surfaces of said light guiding plate and extending substantially in parallel to each other and disposed in said first plane, said light guiding plate including means for controlling light coupling so as to direct light substantially orthogonal to said first plane direction and toward said liquid crystal display panel;

said light guiding plate having opposite upper and lower surfaces, said upper surface facing said liquid crystal display panel, said means for controlling light coupling from the light guiding plate comprising a concave surface portion on each of the upper and lower surfaces of said light guiding plate to enhance uniformity of brightness;

a casing for containing said fluorescent lamps and light guiding member and including a reflecting plate for efficiently and uniformly utilizing the light from the fluorescent lamps;

said casing reflecting plate extending under said light guiding plate and having a convex surface portion disposed adjacent to and in symmetric alignment with the concave surface portion of said lower surface of said means for controlling light coupling, and end walls disposed closely adjacent respective linear fluorescent lamps for reflecting light therefrom;

wherein said casing member and said planar light source contained therein are disposed between said liquid crystal display panel and said substrate and are detachably mounted to the rear surface of said liquid crystal display panel, thereby said planar light source illuminates said liquid crystal display panel with uniform intensity from behind.

2. A display unit according to claim 1, further comprising holders for detachably fastening said casing to said liquid crystal display panel.

3. A display unit according to claim 1, wherein a light diffusing plate is provided between said liquid crystal display panel and said planar light source.

4. A display unit according to claim 3, wherein said fluorescent lamps are of a cold-cathode type.

5. A display unit according to claim 1, wherein said light guiding member has opposite disposed side grooves for receiving therein at least a part of the respective fluorescent lamps.

6. A display unit according to claim 5, wherein said grooves in said light guiding member are each defined by a flange that covers a substantial portion of the associated fluorescent lamps.

7. A display unit according to claim 6, wherein said end walls, said light guiding plate, and said flange define a lamp accommodating compartment larger than the lamp but substantially smaller than the distance between lamps.

8. A display unit according to claim 1, wherein the thickness of the light guiding plate is varied to have a thinner segment at a position remote from both lamps so as to equalize all light transmission paths through said light guiding plate.

9. A display unit according to claim 1 wherein the liquid crystal display panel has a centrally disposed axis and the concave surface portions likewise have a central axis in alignment with the axis of said liquid crystal display panel.

10. A display unit according to claim 9 wherein said casing reflecting plate convex surface portion likewise has a central axis in alignment with the axis of said concave surface portions of said light guiding plate.

11. A display unit according to claim 10 wherein the radius of curvature of said concave surface portion is substantially the same as the radius of curvature of said convex surface portion.

12. A display unit according to claim 11 wherein said casing convex surface portion is accommodated within the lower concave surface portion of said light guiding plate.