Light guide panel for a back light unit, and method of manufacturing the light guide panel

• US 20070070648A1
• Filed: 02/15/2006
• Published: 03/29/2007
• Est. Priority Date: 09/28/2005
• Status: Abandoned Application

• Current Assignee: Samsung Techwin Co., Ltd. (Hanwha Corporation)
• Original Assignee: Samsung Techwin Co., Ltd. (Hanwha Corporation)
• Inventors: Kim, Sung-chul
• Application Number:
  US11/355,344
• Publication Number:
  US 20070070648A1
• Time in Patent Office: Days
• US Class Current: 362/600
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements

Abstract

Provided are a light guide panel, a back light unit including the light guide panel, and a method of manufacturing the light guide panel. The light guide panel includes: a light guide panel body including an incidence surface receiving light irradiated from a back light source and an emission surface emitting the received light; and a polarizing coating layer positioned above the emission surface and including at least one coating layer coated with an inorganic compound having a refractive index of at least 2.0. Here, a difference between transmittances of P and S wave of polarized light having passed through the polarizing coating layer from the light guide panel body is at least 50% in a visible light area.

Claims

1. A light guide panel for a back light unit including a light source, comprising:

a light guide panel body including an incidence surface configured to receive a light irradiated from the light source and an emission surface configured to substantially emit the light as a sheet light; and

a polarizing coating layer positioned above the emission surface and having a refractive index of at least 2.0,

wherein a difference between a P wave transmittance and an S wave transmittance of the sheet light having passed through the polarizing coating layer is at least 50% in a visible light wavelength range.

2. The light guide panel of claim 1, wherein the polarizing coating layer is a single layer having a thickness between about 35 nm and about 85 nm.

3. The light guide panel of claim 1, wherein the polarizing coating layer is an inorganic compound selected from the group consisting of ZrO₂, HfO₂, Ta₂O₅, TiO₂, Ti₃O₅, Ti₂O₃, ZnS, and ZnSe.

4. The light guide panel of claim 3, wherein the polarizing coating layer is Ti₃O₅ and has a thickness between about 35 nm and about 70 nm.

5. The light guide panel of claim 2, wherein:

the light guide panel body is PMMA; and

a hard coating layer is interposed between the light guide panel body and the polarizing coating layer.

6. The light guide panel of claim 1, wherein the polarizing coating layer comprises:

a first coating layer of a first inorganic compound and having a first refractive index; and

a second coating layer of a second inorganic compound and having a second refractive index, a difference between the first and second refractive indexes being at least 0.7.

7. The light guide panel of claim 6, wherein:

the first coating layer has a thickness between about 170 nm and about 190 nm; and

the second coating layer has a thickness between about 50 nm and about 70 nm.

8. The light guide panel of claim 6, wherein:

the first inorganic compound is selected from the group consisting of Na₃AlF₆, MgF₂, SiO₂, CaF₂, and LaF₃; and

the second inorganic compound is selected from the group consisting of ZrO₂, HfO₂, Ta₂O₅, TiO₂, Ti₃O₅, Ti₂O₃, ZnS, and ZnSe.

9. The light guide panel of claim 6, wherein:

the light guide panel body is PMMA; and

a hard coating layer is interposed between the light guide panel body and the polarizing coating layer.

10. The light guide panel of claim 1, wherein the polarizing coating layer comprises three to ten layers formed of an alternating arrangement of first and second coating layers, each of the three to ten layers having a thickness between about 2 nm and about 300 nm, and

wherein a difference between a refractive index of the first coating layer and a refractive index of the second coating layer is at least 0.7.

11. The light guide panel of claim 10, wherein at least one of the first and second coating layers has a refractive index of at least 2, and the other one of the first and second coating layers has a refractive index of at least 1.65.

12. The light guide panel of claim 11, wherein:

one of the first and second coating layers is formed of at least one material that is selected from the group consisting of Na₃AlF₆, MgF₂, SiO₂, CaF₂, and LaF₃; and

the other one of the first and second coating layers is formed of at least one material that is selected from the group consisting of ZrO₂, HfO₂, Ta₂O₅, TiO₂, Ti₃O₅, Ti₂O₃, ZnS, and ZnSe.

13. The light guide panel of claim 12, wherein the first and second coating layers are selected from the group consisting of:

SiO₂/Ta₂O₅, SiO₂/TiO₂, SiO₂/fTi₃O₅, MgF₂/Ta₂O₅, MgF₂/TiO₂, and MgF₂/Ti₃O₅.

14. The light guide panel of claim 11, wherein the first coating layer has a higher refractive index than the second coating layer.

15. The light guide panel of claim 11, wherein the polarizing coating layer further comprises a third coating layer laminated with the first and second coating layers, and

wherein the third coating layer has a thickness between about 60 nm and about 80 nm, the first coating layer has a thickness between about 5 nm and 20 nm, and a second coating layer has a thickness between about 30 nm and about 50 nm.

16. The light guide panel of claim 10, wherein:

the light guide panel body is PMMA; and

a hard coating layer is interposed between the light guide panel body and the polarizing coating layer.

17. A back light unit comprising:

a back light source;

a light guide panel including a light guide panel body having an incidence surface for receiving light from the back light source, an emission surface for emitting the light to an outside, and a polarizing coating layer having a refractive index of at least 2.0, the polarizing coating layer being positioned above the emission surface and formed of an inorganic compound;

a reflector configured opposite to the emission surface for reflecting light toward the emission surface; and

a light controller configured on the light guide panel for uniformly distributing the light substantially on an entire area of the emission surface

18. The back light unit of claim 17, wherein the polarizing coating layer is a single layer having a thickness between about 35 nm and about 85 nm.

19. The back light unit of claim 17, wherein:

the light guide panel body is PMMA; and

a hard coating layer is interposed between the light guide panel body and the polarizing coating layer.

20. The back light unit of claim 17, wherein the polarizing coating layer comprises:

a first coating layer of a first inorganic compound and having a first refractive index; and

a second coating layer of a second inorganic compound and having a second refractive index, a difference between the first and second refractive indexes being at least 0.7.

21. The back light unit of claim 17, wherein the polarizing coating layer comprises three to ten layers formed of an alternating arrangement of first and second coating layers, each of the three to ten layers having a thickness between about 2 nm and about 300 nm, and

wherein a difference between a refractive index of the first coating layer and a refractive index of the second coating layer is at least 0.7.

22. A method of manufacturing a light guide panel for use with a back light unit, the method comprising:

forming a light guide panel body including an incidence surface for receiving light irradiated from a back light source and an emission surface substantially perpendicular to the incidence surface for emitting the received light as a sheet light;

cleaning the light guide panel body;

forming a hard coating layer on the emission surface of the light guide panel; and

forming a polarizing coating layer having a refractive index of at least 2.0 on the hard coating layer, the polarizing coating layer being configured of one or more organic compound layers, and

wherein a difference between a transmittance of a P wave and a transmittance of an S wave of polarized light having passed through the polarizing coating layer from the light guide panel body is at least 50% in a visible light wavelength range.

23. The method of claim 22, wherein the cleaning step comprises:

disposing the light guide panel body into a container of liquid; and

vibrating the liquid at an ultrasonic frequency for about 1 minute.

24. The method of claim 22, wherein the step of forming a hard coating layer comprises:

applying a predetermined amount of coating solution onto the light guide panel body;

rotating the light guide panel body at a low speed to uniformly coat the hard coating solution on the light guide panel body; and

increasing a rotation speed of the light guide panel.

25. The method of claim 24, further comprising the step of, before the increasing step, determining if the solution is uniformly coated on the light guide panel body.