Liquid crystal display using different light radiation angles of light emitting diodes

• US 8,007,158 B2
• Filed: 10/17/2007
• Issued: 08/30/2011
• Est. Priority Date: 06/19/2007
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Woo, Seung-Gyun, Lee, Ik-Soo, Chu, Young-Bee
• Primary Examiner(s): Han; Jason Moon
• Application Number:
  US11/874,042
• Publication Number:
  US 20080316767A1
• Time in Patent Office: 1,413 Days
• Field of Search: 362/235, 362/612, 362/621, 362/800, 349 61- 62, 349/65, 349/69
• US Class Current: 362/612
• CPC Class Codes: G02B 6/002 by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

A liquid crystal display with low manufacturing cost, small dark area and compact exterior is provided by utilizing a plurality of differently radiating light emitting diodes at different angles. The liquid crystal of present invention includes a thin film transistor panel for displaying image, a backlight assembly for providing light to the thin film transistor panel with a plurality of light emitting diodes with different light radiation angles and a light guiding plate, and a frame unit for encompassing the thin film transistor panel and the backlight assembly. The light emitting diodes are placed either at the mid-point of light incident surface or the corner portion of the light guiding plate.

Claims

1. A backlight assembly comprising:

a light guiding plate having an incident light receiving surface with a first thickness and having an adjacent lateral surface, the light receiving surface having a major surface portion and a cutaway minor surface portion disposed at an edge of the major surface portion of the incident light receiving surface, the cutaway minor surface portion being slanted relative to the major surface portion and relative to the lateral surface;

a plurality of light emitting diodes (LEDs) disposed adjacent to the major and minor surface portions of the incident light receiving surface for thereby providing incident light to the major and minor surface portions, where each of the LEDs has a respective light radiation angle that is defined by a limited light emitting range of that LED;

wherein a first of the plural light emitting diodes faces in substantially paralleling manner, the major surface portion of the incident light receiving surface and is structured to have a respective first light radiation angle;

wherein a second of the plural light emitting diodes faces in substantially paralleling manner, the cutaway minor surface portion of the incident light receiving surface and is spaced apart from the first light emitting diode and is structured to have a respective second light radiation angle greater than the first light radiation angle; and

wherein the light guiding plate has a dark area and an active light emitting area.

2. The backlight assembly of claim 1, wherein the first light radiation angle is larger than 90 degrees.

3. The backlight assembly of claim 1, wherein the second light radiation angle is smaller than 90 degrees.

4. The backlight assembly of claim 1, wherein the second light emitting diode has a light emitting semiconductor, a housing encompassing the light emitting semiconductor and a light emitting opening on the housing.

5. The backlight assembly of claim 4, wherein the light emitting opening of the second light emitting diode faces the cutaway minor surface portion and is smaller than the cutaway minor surface portion.

6. The backlight assembly of claim 5, wherein the light emitting opening is substantially parallel with the cutaway minor surface portion.

7. The backlight assembly of claim 1, wherein the second light emitting diode has a housing located within an extensive area from the dark area.

8. The backlight assembly of claim 1, wherein the second light radiation angle has a first radiation edge line close to the incident light receiving surface and a second radiation edge line close to the lateral surface, wherein the light guiding plate has a dark area and active light emitting area within a light emitting surface, wherein the active light emitting area has a gap with the lateral surface, and wherein the second radiation edge line is within the range between the lateral surface and the active light emitting area.

9. The backlight assembly of claim 1, wherein the first light emitting diode is placed at a mid-point of the incident light receiving surface, and wherein the second light emitting diode is placed adjacent to the lateral surface and is thus spaced relatively far apart from the first light emitting diode.

10. The backlight assembly of claim 1, wherein the second light emitting diode is disposed at a corner portion of a long side of the light guiding plate.

11. The backlight assembly of claim 1, wherein the second light emitting diode is disposed at a portion of a long side of the light guiding plate.

12. A liquid crystal display, comprising:

a thin film transistor panel having a first substrate and a second substrate larger than the first substrate with circuitry unit area where a thin film transistor driving circuit is mounted,

a plurality of light emitting diodes (LEDs) each having a respective light radiation angle that is defined by a limited light emitting range of that LED;

said plural light emitting diodes including a first light emitting diode and a second light emitting diode providing light to the thin film transistor panel, the first and second light emitting diodes respectively having a first light radiation angle and a second light radiation angle, where the second light radiation angle is larger than the first light radiation angle, and

a light guiding plate next to the first and second light emitting diodes to propagate light from the first and second light emitting diodes and disposed under the thin film transistor panel,

wherein the light guiding plate has a light receiving surface having a major surface portion and a cutaway minor surface portion disposed at an edge of the major surface portion of the light receiving surface, the cutaway minor surface portion being slanted relative to the major surface portion, and has a dark area and an active light emitting area,

wherein the circuitry unit overlaps the first and second light emitting diodes, wherein the first light emitting diode faces in a substantially paralleling manner the major surface portion, and wherein the second light emitting diode faces in a substantially paralleling manner the cutaway minor surface portion.

13. The liquid crystal display of claim 12, wherein the circuitry unit overlaps the dark area of the light guiding plate.

14. A method for making a backlight assembly, the method comprising:

providing a plurality of light emitting diodes (LEDs) each having a respective light radiation angle that is defined by a limited light emitting range of that LED;

facing a first of the light emitting diodes toward a first point on an incident light receiving surface of a light guiding plate,

wherein the incident light receiving surface has a major surface portion and one or more cutaway minor surface portions each disposed at an edge of the major surface portion of the incident light receiving surface, the cutaway minor surface portions each being slanted relative to the major surface portion,

wherein the first light emitting diode is structured to respectively have a first light radiation angle; and

facing a second of the light emitting diodes toward a second point on the incident light receiving surface, wherein the second light emitting diode is structured to respectively have a second light radiation angle larger than the first light radiation angle,

wherein the second point is on one of the cutaway minor surface portions of the incident light receiving surface; and

wherein the light guiding plate has a dark area and an active light emitting area.