Light Guide Element, Backlight Unit, and Display Device

• US 20120262940A1
• Filed: 04/13/2012
• Published: 10/18/2012
• Est. Priority Date: 04/15/2011
• Status: Abandoned Application

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: MIYAIRI, Hidekazu, TANAKA, Koichiro, KOEZUKA, Emi
• Application Number:
  US13/446,244
• Publication Number:
  US 20120262940A1
• Time in Patent Office: Days
• US Class Current: 362/602
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• 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 6/0078 Side-by-side arrangements, e.g. for large area displays
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence
• CPC Class Codes: G02F 1/133622 Colour sequential illumination
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources

Abstract

An object is to provide a novel structure of a backlight unit using color-scan backlight drive, which can relieve a color mixture problem. A backlight unit including a plurality of light guide elements is used. The light guide element has a shape extended in the x direction. The light guide element has a shape of rectangular column. Grooves are provided on a bottom surface of the light guide element so as to traverse it in the y direction. Light sources are provided at the ends of the light guide element in the x direction to supply light into the light guide element. Light supplied into the light guide element is reflected by the grooves in the z direction, and emitted to the outside of the light guide element through the top surface. A reflective layer may be provided under the bottom surface of the light guide element.

Claims

1. A light guide element comprising:

a bottom surface; and

a groove on the bottom surface;

wherein the light guide element has a shape of rectangular column,

wherein the groove is formed along a direction perpendicular to a longitudinal direction of the light guide element, and

wherein the groove is filled with a medium having a lower refractive index than the light guide element.

2. The light guide element according to claim 1, wherein the medium is air.

3. The light guide element according to claim 1, wherein a section of the groove seen from the direction perpendicular to the longitudinal direction is in a circular arc.

4. The light guide element according to claim 1, wherein a ratio of a depth of the groove to a width of the groove is 0.5 or less.

5. The light guide element according to claim 1, wherein a refractive index of the light guide element is higher than a refractive index of a medium in contact with the light guide element.

6. The light guide element according to claim 1, wherein at least part of light entering from ends of the light guide element into the light guide element in the longitudinal direction is reflected by the groove toward a top surface opposed to the bottom surface.

7. A backlight unit comprising:

a plurality of light guide elements,

wherein each of the plurality of light guide elements has a shape of rectangular column,

wherein each of the plurality of light guide elements has a bottom surface,

wherein each of the plurality of light guide elements has a groove on the bottom surface,

wherein the groove is formed along a direction perpendicular to a longitudinal direction of each of the plurality of light guide elements, and

wherein the groove is filled with a medium having a lower refractive index than one of the plurality of light guide elements.

8. The backlight unit according to claim. 7, further comprising:

a reflective layer,

wherein the bottom surfaces of the plurality of light guide elements are over the reflective layer.

9. A display device comprising a backlight unit comprising:

the plurality of light guide elements according to claim 7; and

a reflective layer,

wherein the bottom surfaces of the plurality of light, guide elements are over the reflective layer.

10. A backlight unit comprising:

a reflective layer,

a light guide element having a bottom surface over the reflective layer; and

a groove on the bottom surface;

wherein the light guide element has a shape of rectangular column,

wherein the groove is formed along a direction perpendicular to a longitudinal direction of the light guide element, and

wherein the groove overlaps with the reflective layer, and

wherein a region of the reflective layer overlapping with the groove is flat.

11. The backlight unit according to claim 10, wherein a space between the groove and the reflective layer is filled with a medium having a lower refractive index than the light guide element.

12. The backlight unit according to claim 10, wherein a section of the groove seen from the direction perpendicular to the longitudinal direction is in a circular arc.

13. The backlight unit according to claim 10, wherein a ratio of a depth of the groove to a width of the groove is 0.5 or less.

14. The backlight unit according to claim 10, wherein a refractive index of the light guide element is higher than a refractive index of a medium in contact with the light guide element.

15. The backlight unit according to claim 10, wherein at least part of light entering from ends of the light guide element into the light guide element in the longitudinal direction is reflected by the groove toward a top surface opposed to the bottom surface.

16. A backlight unit comprising:

a reflective layer; and

a plurality of light guide elements each having a bottom surface over the reflective layer,

wherein each of the plurality of light guide elements has a groove on the bottom surface,

wherein the groove is formed along a direction perpendicular to a longitudinal direction of each of the plurality of light guide elements,

wherein the groove overlaps with the reflective layer, and

wherein a region of the reflective layer overlapping with the groove is flat.

17. A display device comprising the backlight unit according to claim 16.