Liquid crystal display device comprising at least one groove having an end portion that stops short of the non-adjacent opposite side surfaces and extends in a direction perpendicular to the non-adjacent side surfaces

• US 8,089,582 B2
• Filed: 05/30/2008
• Issued: 01/03/2012
• Est. Priority Date: 05/31/2007
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Hitachi Displays Limited (Japan Display Incorporated), Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Inventors: Sekiguchi, Yoshifumi, Konno, Akitoyo, Sasaki, Hiroshi
• Primary Examiner(s): Robinson, Mark
• Assistant Examiner(s): Kim, Dennis Y
• Application Number:
  US12/129,838
• Publication Number:
  US 20080297695A1
• Time in Patent Office: 1,313 Days
• Field of Search: 362616-620, 345/62, 345/65
• US Class Current: 349/65
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0078 Side-by-side arrangements, e.g. for large area displays
• CPC Class Codes: G02B 6/0085 Means for removing heat created by the light source from the package heat extraction or cooling elements for semiconductor light sources in general H01L33/64
• CPC Class Codes: G02F 1/133601 for spatial active dimming
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

An object of the present invention is to provide a liquid crystal display device having a light guide plate that is capable of providing improved liquid crystal display performance without generating a striped image. The liquid crystal display device includes a light guide plate, which illuminates a liquid crystal panel from its rear surface, and light sources, which shed a light ray on the light guide plate. The rear surface of the light guide plate is separated into a plurality of rear surface divisions by concave grooves. The light sources can adjust the brightness of each rear surface division. The display performance of the liquid crystal panel is improved by individually managing a plurality of regions of the liquid crystal panel, which correspond to the rear surface divisions, and darkening a rear surface division that corresponds to a region where the black color is predominant.

Claims

1. A liquid crystal display device comprising:

a liquid crystal panel;

a light guide plate having side surfaces, the side surfaces including non-adjacent opposite side surfaces, the light guide plate being mounted on a rear surface of the liquid crystal panel;

at least one light source positioned with respect to at least one of the non-adjacent opposite side surfaces of the light guide plate so that a light ray therefrom is incident on the light guide plate at an incidence plane formed on the at least one of the non-adjacent opposite side surfaces of the light guide plate; and

light source driving means for driving the at least one light source;

wherein the light guide plate guides the light ray incident from the incidence plane, outputs the light ray from an output plane of the light guide plate facing the liquid crystal panel, and illuminates the liquid crystal panel from the rear surface of the liquid crystal panel;

wherein at least one groove is formed on a plane of the light guide plate which extends substantially parallel to the rear surface of the liquid crystal panel, the at least one groove having a depth in a direction from the output plane of the light guide plate to a back surface of the light guide plate which is opposite to the output plane without penetrating one of the output plane and the back surface of the light guide plate the direction of the depth thereof;

wherein the at least one groove extends between the non-adjacent opposite side surfaces of the light guide plate, the at least one groove having an end portion thereof which stops short of the non-adjacent opposite side surfaces without penetrating the non-adjacent opposite side surfaces, at least one of the non-adjacent opposite side surfaces having the at least one light source positioned with respect thereto;

wherein the plane on which the at least one groove is formed has an indented portion and raised portions, the raised portions being higher than the indented portion, the indented portion being interposed between the raised portions, the raised portions extending to reach a part of the peripheries of the plane at both of the non-adjacent opposite side surfaces;

wherein the at least one groove extends in a direction perpendicular to the non-adjacent opposite side surfaces.

2. The liquid crystal display device according to claim 1, wherein the at least one groove forms a concave section and a convex section at one end of the incidence plane;

wherein the at least one light source includes light sources positioned relative to the convex section formed at one end of the incidence plane; and

wherein the light source driving means individually controls the light sources positioned relative to the convex section.

3. The liquid crystal display device according to claim 2, wherein the liquid crystal panel displays videos by periodically rewriting the image data to be displayed;

wherein the at least one light source becomes extinguished during a extinguishment period, which a part of a frame period that is required to rewrite one image data displayed on the display surface of the liquid crystal panel; and

wherein the timing with which the extinguishment period begins varies from one individually-controlled light source to another.

4. The liquid crystal display device according to claim 2, wherein the liquid crystal panel displays videos by periodically rewriting the image data to be displayed;

wherein the at least one light source becomes extinguished during a extinguishment period, which a part of a frame period that is required to rewrite one image data displayed on the display surface of the liquid crystal panel; and

wherein the timing with which the extinguishment period begins varies between at least two of the individually-controlled light sources.

5. The liquid crystal display device according to claim 1, wherein the at least one groove extends on the plane from the one of the non-adjacent opposite side surfaces of the incidence plane to about halfway toward the other of the non-adjacent opposite side surfaces.

6. The liquid crystal display device according to claim 1, wherein the at least one groove forms a concave section and a convex section at one end of the incidence plane;

wherein the at least one light source is positioned relative to the convex section formed at end of the incidence plane; and

wherein the light guide plate is such that the convex section near the one end of the incidence plane is wider than the convex section near the center.

7. The liquid crystal display device according to claim 1, wherein the at least one groove forms a concave section and a convex section at one end of the incidence plane;

wherein the at least one light source is composed of a plurality of LEDs and positioned relative to the convex section formed at end of the incidence plane; and

wherein the light source LEDs for a convex section near the one end of the incidence plane of the light guide plate are smaller in number than the light source LEDs for a convex section near the center.

8. The liquid crystal display device according to claim 1, further comprising:

a rear cover mounted with respect to a rear surface of the light guide plate; and

a heatsink positioned between the liquid guide plate and the rear cover;

wherein heat generated by the at least one light source is transferred to the heatsink, and the rear cover is mounted so as to be spaced from the rear surface of the light guide plate and to delimit a space therebetween.

9. The liquid crystal display device according to claim 8, wherein the heatsink is L-shaped when viewed from above, and wherein a bent portion of the heatsink is positioned between the light guide plate and the rear cover.

10. The liquid crystal display device according to claim 8, wherein the rear cover has an air inlet and an air outlet.

11. The liquid crystal display device according to claim 1, wherein the light guide plate is divided in a plurality of optically separated regions by the at least one groove, and a same light source of the at least one light source is utilized for at least two optically separated regions of the plurality of optically separated regions of the light guide plate.

12. The liquid crystal display device according to claim 1, wherein the light guide plate is divided in a plurality of optically separated regions by the at least one groove, and the at least one light source corresponding to at least two optically separated regions of the plurality of optically separated regions of the light guide plate are simultaneously driven by the light source driving means.

13. The liquid crystal display device according to claim 1, wherein the plane on which the at least one groove is formed is one of the output plane and the back surface of the light guide plate.

14. The liquid crystal display device according to claim 1, wherein the at least one light source is positioned only with respect to the one of the non-adjacent opposite side surfaces of the light guide plate.

15. The liquid crystal display device according to claim 1, wherein at least one other groove is formed to extend in a direction substantially transverse to the extension direction of the at least one groove at a position adjacent to the other end portion of the at least one groove.

16. The liquid crystal display device according to claim 1, wherein a plurality of the grooves are formed on the plane of the light guide plate;

one of the raised portions being interposed between a pair of the grooves next to each other, the one of the raised portions having a width between the pair of the grooves, the width being greater than a width of each of the grooves.

17. The liquid crystal display device according to claim 1, wherein a plurality of the light sources are positioned with respect to the at least one of the non-adjacent opposite side surfaces of the light guide;

one of the light sources being positioned next to at least two of the raised portions having the at least one groove interposed therebetween to share the light ray emitted from the one of the light sources.

18. The liquid crystal display device according to claim 17, wherein the one of the light sources is equipped with a plurality of LEDs that are simultaneously driven by the light source driving means.