Viewing angle switchable back light unit

Patent metadata

Field	Value
Publication number	US-9851489-B2
Application number	US-201615184349-A
Country	US
Kind code	B2
Filing date	Jun 16, 2016
Priority date	Jul 8, 2015
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

The present disclosure relates to a viewing angle switchable back light unit in which the general mode and the privacy mode in a liquid crystal display can be selected. The present disclosure suggests a thin film type back light unit comprising: a light guide film including a light entering part disposed at one side, a light changing part disposed at other side and a light guiding part connecting the light entering part and the light changing part; a light radiating part disposed on an upper surface of the light guide film; and a light source disposed at the light entering part of the light guide film. The light entering part includes a wedge light coupler and a light deflection element. The light changing part includes a light reflecting pattern. The light radiating part includes a light radiating film providing some of the collimated lights as back lights.

First claim

What is claimed is:

1. A back light unit, comprising:
a light guide film including a light entering part disposed at one side, a light changing part disposed at other side and a light guiding part connecting the light entering part and the light changing part;
a light radiating part disposed on an upper surface of the light guide film; and
a light source disposed at the light entering part of the light guide film,
wherein the light entering part includes:
a wedge light coupler converting expanded incident lights provide from the light source into vertical semi-collimated lights having a narrow expanding angle on a horizontal plane and being semi-collimated on a vertical plane; and
a light deflection element converting the vertical semi-collimated lights received from the wedge light coupler into vertical collimated lights on the vertical plane satisfying a total reflection condition within the light guiding part,

wherein the light changing part includes: a light reflecting pattern for coverting the vertical collimated lights received from the light guiding part into collimated lights being further collimated on the horizontal plane, breaking the total reflection condition within the light guiding part and satisfying a total reflection condition at the interface with the light radiating part, and for sending the collimated lights to the light guiding part,
wherein the light radiating part includes: a light radiating film providing some of the collimated lights as back lights and reflecting others of the collimated lights into the light guiding part.

2. The back light unit according to the claim 1 , further comprising:
a light absorbing pattern being disposed between the wedge light coupler and the light radiating part and absorbing some of the vertical collimated lights unsatisfying the total reflection condition within the light guiding part.

3. The back light unit according to the claim 1 , wherein the light guiding part includes:
a high refractive film; and
a low refractive film attached on any one of an upper surface and a bottom surface of the high refractive film, and
wherein the light radiating pattern includes any one of a surface grating film and a volume grating film attaching on outer surface of the lower refractive film.

4. The back light unit according to the claim 1 , wherein the wedge light coupler includes:
a horizontal wedge part disposed close to the light source; and
a vertical wedge part extended from the horizontal wedge part.

5. The back light unit according to the claim 4 , wherein the horizontal wedge part includes:
a light incident surface disposed close to the light source and having a height and a width corresponding to a size of the light source;
an upper surface and a bottom surface extended to one direction with a distance and expanded with a expanded angle; and
two side surfaces having a height corresponding to the height of the light incident surface and a length corresponding to the certain distance,
wherein the vertical wedge part includes an inclined surface extended to the one direction from the horizontal wedge part in which the height of the two side surfaces are linearly reduced from the upper surface to the bottom surface along to a length of the vertical wedge part.

6. The back light unit according to the claim 5 , wherein a plurality of the horizontal wedge part is disposed along to a side of the vertical wedge part which is perpendicular to the one direction, and
wherein a plurality of the light source is disposed close to a plurality of the light incident surface one by one.

7. The back light unit according to the claim 1 , wherein the light guiding part sends the vertical collimated lights from the light entering part to the light changing part by repeating the total reflection, and
wherein the light guiding part refracts some of the collimated lights to the light radiating part and sends others of the collimated lights from the light changing part to the light entering part.

8. The back light unit according to the claim 1 , wherein the wedge light coupler is disposed at one side close to the light source, on an upper surface of the high refractive film,
wherein the light deflection element is disposed under the bottom surface of the high refractive film as facing with the wedge light coupler,
wherein the low refractive film is attached on the upper surface of the high refractive film,
wherein the light reflecting pattern is disposed at an opposite side to the wedge light coupler, on the upper surface of the high refractive film, and
wherein the light radiating film is attached on an upper surface of the low refractive film.

9. The back light unit according to the claim 1 , wherein the wedge light coupler is disposed at one side close to the light source, on an upper surface of the high refractive film,
wherein the light deflection element is disposed under the wedge light coupler, on an upper surface of the high refractive film,
wherein the low refractive film is attached on the upper surface of the high refractive film,
wherein the light reflecting pattern is disposed at an opposite side to the wedge light coupler, on the upper surface of the high refractive film, and
wherein the light radiating film is attached on an upper surface of the low refractive film.

10. The back light unit according to the claim 1 , wherein the wedge light coupler is disposed at one side close to the light source, on an upper surface of the high refractive film,
wherein the light deflection element is disposed as facing with the wedge light coupler, under a bottom surface of the high refractive film,
wherein the low refractive film is attached close to the wedge light coupler, under the bottom surface of the high refractive film,
wherein the light reflecting pattern is disposed at an opposite side to the wedge light coupler, under the bottom surface of the high refractive film, and
wherein the light radiating film is attached under a bottom surface of the low refractive film.

11. The back light unit according to the claim 1 , further comprising:
a switchable light scattering film disposed on the light guide film.

12. The back light unit according to the claim 1 , further comprising:
any one of a direct type back light unit and an edge type back light unit disposed under the light guide film.

Assignees

• Lg Display Co Ltd
• Covestro Deutschland Ag

Inventors

• Bang Hyungseok
• Ryu Seungman
• Hyun Joobong
• Bruder Friedrich-Karl

Classifications

• G02B6/005

  provided by one optical element, or plurality thereof, placed on the light output side of the light guide · CPC title

• G02B6/0073

  Light emitting diode [LED] · CPC title

• G02B6/002 Primary

  by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces · CPC title

• G02B6/0028

  Light guide, e.g. taper · CPC title

• G02B6/0055

  Reflecting element, sheet or layer · CPC title