Light guide plate for a display panel having arcuate grooves formed in the incident and upper surfaces

1. A liquid crystal display device comprising:

a liquid crystal panel; and

an illumination device which is arranged on a back surface of said liquid crystal panel;

wherein said illumination device includes a light guide plate and a plurality of spot light sources on at least one side surface of said light guide plate;

wherein said light guide plate includes a large number of upper-surface arcuate cross-sectional grooves in the direction orthogonal to said one side surface on an upper surface thereof which faces said liquid crystal panel;

wherein a large number of light-incident-surface arcuate cross-sectional grooves are formed in the thickness direction of said light guide plate on at least a portion of said one side surface which faces a position at which said plurality of spot light sources are arranged; and

wherein a relationship between a contact angle Oa of the upper-surface arcuate cross-sectional grooves and a contact angle Ea of the light-incident-surface arcuate cross-sectional grooves is set as

1.5 ×Oa− 35(°)≦ Ea (°)≦1.5 ×Oa− 27(°).

2. A liquid crystal display device according to claim 1 , wherein

a flat portion is formed on said one side surface of said light guide plate at a position thereof which faces a position between two of said plurality of spot light sources.

3. A liquid crystal display device according to claim 1 , wherein when a distance which is ½ of a distance between two of said plurality of spot light sources is smaller than a distance between one of said plurality of spot light sources which is arranged at an outermost side and a corner portion of said light guide plate, on said upper surface of said light guide plate, a flat portion is formed on said upper surface of said light guide plate in the vicinity of a region which extends from said one of said plurality of spot light sources which is arranged at said outermost side to said corner portion.

4. A liquid crystal display device according to claim 2 , wherein when a distance which is ½ between two of said plurality of spot light sources is smaller than a distance between one said plurality of spot light sources which is arranged at an outermost side and a corner portion of said light guide plate, on said upper surface of the light guide plate, a flat portion is formed in the vicinity of a region which extends from said one of said plurality of spot light sources which is arranged at said outermost side to said corner portion.

5. A liquid crystal display device according to claim 1 , wherein between said liquid crystal panel and said illumination device, a prism sheet on which a large number of prism grooves are formed in parallel in the direction orthogonal to the direction that said upper-surface arcuate cross-sectional grooves of said light guide plate are formed on said light guide plate side.

6. A liquid crystal display device according to claim 1 , wherein on a surface of said light guide plate opposite to a surface on which the upper-surface arcuate cross-sectional grooves are formed, a large number of lower-surface triangular cross-sectional grooves are formed in the direction orthogonal to the direction that said upper-surface arcuate cross-sectional grooves of said light guide plate are formed.

7. A liquid crystal display device according to claim 6 , wherein a reflection film or a reflection sheet is arranged on a lower side of the lower-surface triangular cross-sectional grooves of said light guide plate.

8. A liquid crystal display device according to claim 1 , wherein the relationship between the contact angle Oa and the contact angle Ea enable said light guide plate to have excellent brightness distribution without brightness irregularities in a vicinity of said one side surface of said light guide plate which faces the position at which said plurality of spot light sources are arranged.

9. A liquid crystal display device comprising:

a liquid crystal panel; and

an illumination device which is arranged on a back surface of a liquid crystal panel;

wherein said illumination device includes a light guide plate and a plurality of spot light source on at least one side surface of said light guide plate;

wherein said light guide plate includes a large number of upper-surface arcuate cross-sectional grooves in the direction orthogonal to said one side surface on an upper surface thereof which faces said liquid crystal panel;

wherein a large number of light-incident-surface arcuate cross-sectional grooves are formed in the thickness direction of said light guide plate on at least a portion of said one side surface which faces a position at which said plurality of spot light sources are arranged; and

wherein a relationship between a contact angle Oa of the upper-surface arcuate cross-sectional grooves and a contact angle Ea of the light-incident-surface arcuate cross-sectional grooves is set as

1.5 ×Oa− 39(°)≦ Ea (°)≦1.5 ×Oa− 23(°).

10. A liquid crystal display device according to claim 9 , wherein a flat portion is formed on said one side surface of said light guide plate at a position thereof which faces a position between two of said plurality of spot light sources.

11. A liquid crystal display device according to claim 9 , wherein when a distance which is ½ of a distance between two of said plurality of spot light sources is smaller than a distance between one of said plurality of spot light sources which is arranged at an outermost side and a corner portion of said light guide plate, on said upper surface of said light guide plate, a flat portion is formed in the vicinity of a region which extends from said one of said plurality of spot light sources which is arranged at said outermost side to said corner portion.

12. A liquid crystal display device according to claim 10 , wherein when a distance which is ½ between two of said plurality of spot light sources is smaller than a distance between one said plurality of spot light sources which is arranged at an outermost side and a corner portion of said light guide plate, on said upper surface of said light guide plate, a flat portion is formed in the vicinity of a region which extends from said one of said plurality of said spot light sources which is arranged at said outermost side to said corner portion.

13. A liquid crystal display device according to claim 9 , wherein between said liquid crystal panel and said illumination device, a prism sheet on which a large number of prism grooves are formed in parallel in the direction orthogonal to the direction that the upper-surface arcuate cross-sectional grooves of said light guide plate are formed on said light guide plate side.

14. A liquid crystal display device according to claim 9 , wherein on a surface of said light guide plate opposite to a surface on which the upper-surface arcuate cross-sectional grooves are formed, a large number of lower-surface triangular cross-sectional grooves are formed in the direction orthogonal to the direction that the upper-surface arcuate cross-sectional grooves of said light guide plate are formed.

15. A liquid crystal display device according to claim 9 , wherein a reflection film or a reflection sheet is arranged on a lower side of the lower-surface triangular cross-sectional grooves of said light guide plate.

16. A liquid crystal display device according to claim 9 , wherein the relationship between the contact angle Oa and the contact angle Ea enable said light guide plate to have excellent brightness distribution without brightness irregularities in a vicinity of said one side surface of said light guide plate which faces the position at which said plurality of spot light sources are arranged.