ILLUMINATION DEVICE AND DISPLAY DEVICE

Abstract

According to one embodiment, an illumination device comprises a light guide, a light source, a reflective layer, a first prism and a second prism, wherein the light guide has a thickness in a second direction increasing toward a second side surface, the first prism and the second prism have cross-sectional shapes being formed in a triangle shape, a first height of the first prism in the second direction is smaller than a second height of the second prism in the second direction.

Description

Claims

1. An illumination device comprising: a light guide including: a first side surface,a second side surface opposed to the first side surface in a first direction,a main surface, andan opposing surface opposed to the main surface in a second direction intersecting the first direction;a light source that is opposed to the first side surface and emits light to the first side surface;a reflective layer provided on the second side surface;a first prism provided on the opposing surface; anda second prism provided on a side closer to the second side surface in the first direction than the first prism on the opposing surface, whereinthe light guide has a thickness in the second direction increasing from the first side surface toward the second side surface in the first direction,the opposing surface includes a first slope,a second slope located on a side closer to the second side surface than the first slope in the first direction,a third slope located on a side closer to the second side surface than the second slope in the first direction,a fourth slope located on a side closer to the second side surface than the third slope in the first direction,a first plane that connects the first slope and the second slope and is parallel to the main surface, anda second plane that connects the third slope and the fourth slope and is parallel to the main surface,the first prism and the second prism have cross-sectional shapes being formed in a triangle shape protruding to an opposite side of the opposing surface in the second direction,the first prism is disposed on the first plane,the second prism is disposed on the second plane,a first height of the first prism in the second direction is smaller than a second height of the second prism in the second direction, anda sum of the first height, a third height of the first slope in the second direction, and a fourth height of the second slope in the second direction is larger than a sum of the second height, a fifth height of the third slope in the second direction, and a sixth height of the fourth slope in the second direction.

2. The illumination device according to claim 1, wherein the cross-sectional shapes of the first prism and the second prism are formed in an isosceles triangle shape in which two base angles are a first angle,each of the first slope and the second slope is angled at the first angle with respect to the first plane, andeach of the third slope and the fourth slope is angled at the first angle with respect to the second plane.

3. The illumination device according to claim 2, further comprising a third prism disposed on the first plane, wherein the third prism has a cross-sectional shape formed in an isosceles triangle shape in which two base angles are the first angle.

4. The illumination device according to claim 2, wherein the opposing surface has a third plane that connects the second slope and the third slope and is parallel to the main surface.

5. The illumination device according to claim 2, wherein the first angle is equal to or larger than a main ray angle of light emitted from the light source and incident on the light guide from the first side surface.

6. The illumination device according to claim 1, wherein the third height and the fourth height are same,the fifth height and the sixth height are same, andthe third height and the fourth height are larger than the fifth height and the sixth height.

7. The illumination device according to claim 1, wherein the light guide includes a third side surface intersecting the second side surface,a fourth side surface that is opposed to the third side surface in a third direction intersecting the first direction and the second direction and intersects the second side surface,a first surface connecting the first side surface and the third side surface, anda second surface connecting the first side surface and the fourth side surface,the light source includes a first light source, a second light source, and a third light source,a first length of the first side surface in the third direction is smaller than a second length of the second side surface in the third direction,the second light source is interposed between the first light source and the third light source in the third direction, anda first light intensity ratio of the first light source and the third light source is higher than a second light intensity ratio of the second light source.

8. An illumination device comprising: a light guide including: a first side surface,a second side surface opposed to the first side surface in a first direction,a main surface, andan opposing surface that is opposed to the main surface in a second direction intersecting the first direction and is parallel to the main surface;a light source that is opposed to the first side surface and emits light to the first side surface;a reflective layer provided on the second side surface;a first prism group provided on the opposing surface; anda second prism group provided on a side closer to the second side surface in the first direction than the first prism group on the opposing surface, wherein the first prism group includes a first prism,a second prism located on a side closer to the second side surface than the first prism in the first direction, anda third prism located on a side closer to the second side surface than the second prism in the first direction,the second prism group includes a fourth prism,a fifth prism located on a side closer to the second side surface than the fourth prism in the first direction, anda sixth prism located on a side closer to the second side surface than the fifth prism in the first direction,a first height of the second prism in the second direction is smaller than a second height of the fifth prism in the second direction, anda sum of the first height, a third height of the first prism in the second direction, and a fourth height of the third prism in the second direction is larger than a sum of the second height, a fifth height of the fourth prism in the second direction, and a sixth height of the sixth prism in the second direction.

9. The illumination device according to claim 8, wherein each of the second prism and the fifth prism has a cross-sectional shape formed in an isosceles triangle shape in which two base angles are a first angle,each of the first prism, the third prism, the fourth prism, and the sixth prism has a cross-sectional shape formed in a triangle shape having a vertex at which a first side intersects a second side,the first side is angled at the first angle with respect to the opposing surface, andthe second side is located on a side closer to the second side surface than the first side in the first direction, and is angled at a second angle which is larger than the first angle with respect to the opposing surface.

10. The illumination device according to claim 9, wherein the second angle is 90°.

11. The illumination device according to claim 8, wherein the third height and the fourth height are same,the fifth height and the sixth height are same, andthe third height and the fourth height are larger than the fifth height and the sixth height.

12. The illumination device according to claim 8, wherein the light guide includes a third side surface intersecting the second side surface,a fourth side surface that is opposed to the third side surface in a third direction intersecting the first direction and the second direction and intersects the second side surface,a first surface connecting the first side surface and the third side surface, anda second surface connecting the first side surface and the fourth side surface,the light source includes a first light source, a second light source, and a third light source,a first length of the first side surface in the third direction is smaller than a second length of the second side surface in the third direction,the second light source is interposed between the first light source and the third light source in the third direction, anda first light intensity ratio of the first light source and the third light source is higher than a second light intensity ratio of the second light source.

13. An illumination device comprising: a light guide including: a first side surface,a second side surface opposed to the first side surface in a first direction,a third side surface intersecting the second side surface,a fourth side surface that is opposed to the third side surface in a third direction, which intersects the first direction and a second direction intersecting the first direction, and intersects the second side surface,a first surface connecting the first side surface and the third side surface, anda second surface connecting the first side surface and the fourth side surface;a first light source, a second light source, and a third light source that are opposed to the first side surface and emit light to the first side surface; anda reflective layer provided on the second side surface, wherein a first length of the first side surface in the third direction is smaller than a second length of the second side surface in the third direction,the second light source is interposed between the first light source and the third light source in the third direction, anda first light intensity ratio of the first light source and the third light source is higher than a second light intensity ratio of the second light source.

14. The illumination device according to claim 13, further comprising a plurality of prisms provided on the light guide, wherein a first density of prisms disposed on an outer side in the third direction is higher than a second density of prisms disposed at a central portion in the third direction.

15. A display device comprising: the illumination device according to claim 1; anda display panel that displays an image, wherein the display panel is opposed to the illumination device.

16. A display device comprising: the illumination device according to claim 8; anda display panel that displays an image, wherein the display panel is opposed to the illumination device.

17. A display device comprising: the illumination device according to claim 13; anda display panel that displays an image, wherein the display panel is opposed to the illumination device.