Backlight unit and liquid crystal display including the same

• US 9,726,928 B2
• Filed: 12/07/2012
• Issued: 08/08/2017
• Est. Priority Date: 12/09/2011
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Jang, Hyo Sook, Kang, Hyun A, Jang, Eun Joo, Jun, Shin Ae
• Primary Examiner(s): Frost, Anthony J
• Application Number:
  US13/708,431
• Publication Number:
  US 20130148057A1
• Time in Patent Office: 1,705 Days
• Field of Search: None
• CPC Class Codes: B32B 2457/202 LCD, i.e. liquid crystal displays
• CPC Class Codes: C08K 9/08 Ingredients agglomerated by treatment with a binding agent
• CPC Class Codes: C09D 123/0869 Acids or derivatives thereof
• CPC Class Codes: C09K 11/02 Use of particular materials as binders, particle coatings or suspension media therefor
• CPC Class Codes: C09K 11/565 with zinc cadmium
• CPC Class Codes: C09K 11/70 containing phosphorus
• CPC Class Codes: C09K 11/883 with zinc or cadmium
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
• CPC Class Codes: C09K 2323/03 Viewing layer characterised by chemical composition
• CPC Class Codes: G02F 1/133524 Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides
• CPC Class Codes: G02F 1/133614 using photoluminescence, e.g. phosphors illuminated by UV or blue light
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 2202/022 polymeric
• CPC Class Codes: G02F 2202/10 semiconductor
• CPC Class Codes: G02F 2202/106 Cd×Se or Cd×Te and alloys
• CPC Class Codes: G02F 2202/107 Zn×S or Zn×Se and alloys
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A backlight unit for a liquid crystal display device, the backlight unit including: an light emitting diode (“LED”) light source; a light conversion layer disposed separate from the LED light source to convert light emitted from the LED light source to white light and to provide the white light to the liquid crystal panel; and a light guide panel disposed between the LED light source and the light conversion layer, wherein the light conversion layer includes a semiconductor nanocrystal and a polymer matrix, and wherein the polymer matrix includes a first polymerized polymer of a first monomer including at least two thiol (—SH) groups, each located at a terminal end of the first monomer, and a second monomer including at least two unsaturated carbon-carbon bonds, each located at a terminal end of the second monomer.

Claims

1. A backlight unit for a liquid crystal display device, the backlight unit comprising:

a light emitting diode light source;

a light conversion layer disposed separate from the light emitting diode light source to convert light emitted from the light emitting diode light source to white light and to provide the white light to a liquid crystal panel; and

a light guide panel disposed between the light emitting diode light source and the light conversion layer,

wherein the light conversion layer comprises a polymer matrix and a semiconductor nanocrystal dispersed in the polymer matrix, and

wherein the polymer matrix comprises a first polymerized product of monomers selected from the group consisting of

at least one first monomer including at least two thiol (—

SH) groups, each located at a terminal end of the at least one first monomer, and

at least one second monomer including at least two unsaturated carbon-carbon bonds, each located at a terminal end of the at least one second monomer,

wherein the at least one second monomer of the polymer matrix is represented by the following Chemical Formula 2;

2. The backlight unit for a liquid crystal display device of claim 1, wherein the backlight unit further comprises a diffusion plate on a light guide panel, and the light conversion layer is disposed between the light guide panel and the diffusion plate.

3. The backlight unit for a liquid crystal display device of claim 1, wherein the light emitting diode light source is disposed on at least one side of the light conversion layer.

4. The backlight unit for a liquid crystal display device of claim 1, wherein the semiconductor nanocrystal is a Group II-VI compound, a Group III-V compound, a Group IV-VI compound, a Group IV element, a Group IV compound, or a combination thereof.

5. The backlight unit for a liquid crystal display device of claim 1, wherein the semiconductor nanocrystal has a full width at half maximum of less than or equal to about 45 nanometers in a light emitting wavelength spectrum.

6. The backlight unit for a liquid crystal display device of claim 1, wherein the at least one first monomer of the polymer matrix is represented by the following Chemical Formula 1:

7. The backlight unit for a liquid crystal display device of claim 1, wherein the polymer matrix of the light conversion layer is a product of further polymerizing at least one monomer selected from the group consisting of

at least one third monomer having a thiol group located at a terminal end of the at least one third monomer, and

at least one fourth monomer having an unsaturated carbon-carbon bond at a terminal end of the at least one fourth monomer.

8. The backlight unit for a liquid crystal display device of claim 1, wherein the light conversion layer further comprises an inorganic oxide.

9. The backlight unit for a liquid crystal display device of claim 1, wherein the semiconductor nanocrystal further comprises a coating, the coating comprising a polymer having a carboxyl group, or a salt thereof.

10. The backlight unit for a liquid crystal display device of claim 9, wherein the polymer having a carboxyl group or a salt thereof is a poly(alkylene-co-acrylic acid), a poly(alkylene-co-methacrylic acid), a salt thereof, or a combination thereof.

11. The backlight unit for a liquid crystal display device of claim 1, wherein white light emitted from the light conversion layer has a Cx of about 0.24 to about 0.56 and a Cy of about 0.24 to about 0.42 in a CIE 1931 chromaticity diagram.

12. The backlight unit for a liquid crystal display device of claim 1, wherein the semiconductor nanocrystal of the light conversion layer comprises a green light emitting semiconductor nanocrystal and a red light emitting semiconductor nanocrystal in an optical density ratio of about 2:

1 to about 7;

1, wherein the optical density is determined using an absorbance of a first absorption maximum in a UV-Vis absorption spectrum, and when the light emitting diode light source is a blue light emitting diode light source.

13. The backlight unit for a liquid crystal display device of claim 1, wherein the light conversion layer is in the form of a film comprising the semiconductor nanocrystal and the polymer matrix;

further comprising at least one of a first polymer film and a second polymer film disposed on at least one surface of the film,

wherein the first polymer film and the second polymer film each independently comprise

a polyester, a cyclic olefin polymer (COP), a second polymerized product of the at least one first monomer comprising at least two thiol (—

SH) groups, each located at the terminal end of the at least one first monomer, and the at least one second monomer comprising at least two unsaturated carbon-carbon bonds at a terminal end of the at least one second monomer, or a combination thereof, and

an inorganic oxide,

wherein the at least one first monomer and the at least one second monomer of the first and second polymerized products are each independently selected.

14. The backlight unit for a liquid crystal display device of claim 13, wherein at least one of the first polymer film and the second polymer film has concavo-convex pattern on a surface opposite the light conversion layer.

25. The backlight unit for a liquid crystal display device of claim 1, wherein in Chemical Formula 2, X is (meth)acrylate and a C3 to C30 alicyclic hydrocarbon group including a carbon-carbon double bond, L₂ is a C1 to C20 alkylene group;

Y₂ is a single bond;

n is 1;

k3 is 0;

k4 is 2; and

the sum of n and k4 is 3.

26. The backlight unit for a liquid crystal display device of claim 25, wherein the second monomer comprises tricyclodecane dimethanol diacrylate.

15. A liquid crystal display device, comprising:

a light emitting diode light source;

a light conversion layer disposed separate from the light emitting diode light source to convert light emitted from the light emitting diode light source to white light and to provide the white light to a liquid crystal panel;

a light guide panel disposed between the light emitting diode light source and the light conversion layer; and

a liquid crystal panel for providing an image using light provided from the light conversion layer,

wherein the light conversion layer comprises a polymer matrix and a semiconductor nanocrystal dispersed in the polymer matrix, and

wherein the polymer matrix comprises a first polymerized product of monomers selected from

at least one first monomer including at least two thiol (—

SH) groups, each located at a terminal end of the at least one first monomer, and

at least one second monomer including at least two unsaturated carbon-carbon bonds, each located at a terminal end of the at least one second monomer,

wherein the at least one second monomer of the polymer matrix is represented by the following Chemical Formula 2;

16. The liquid crystal display device of claim 15, further comprising a diffusion plate on the light guide panel.

17. The liquid crystal display device of claim 15, wherein the light emitting diode light source is disposed on at least one side of the light conversion layer.

18. The liquid crystal display device of claim 15, wherein the at least one first monomer of the polymer matrix is represented by the following Chemical Formula 1:

19. The liquid crystal display device of claim 15, wherein the polymer matrix of the light conversion layer is a product of further polymerizing at least one monomer selected from the group consisting of

at least one third monomer having a thiol group located at the terminal end of the at least one third monomer, and

at least one fourth monomer having an unsaturated carbon-carbon bond at a terminal end of the at least one fourth monomer.

20. The liquid crystal display device of claim 15, wherein the light conversion layer further comprises an inorganic oxide.

21. The liquid crystal display device of claim 15, wherein the semiconductor nanocrystal further comprises a coating, the coating comprising a polymer having a carboxyl group, or a salt thereof.

22. The liquid crystal display device of claim 15, wherein the light conversion layer is in the form of a film comprising the semiconductor nanocrystal and the polymer matrix;

further comprising at least one of a first polymer film and a second polymer film disposed on at least one surface of the film,

wherein the first polymer film and the second polymer film each independently comprise a polyester, a cyclic olefin polymer (COP), or a second polymerized product of the at least one first monomer including at least two thiol (—

SH) groups, each located at the terminal end of the at least one first monomer, and the at least one second monomer comprising at least two unsaturated carbon-carbon unsaturated bonds at a terminal end of the at least one second monomer, or a combination thereof,

wherein the at least one first monomer and the at least one second monomer of the first and second polymerized products are each independently selected.

23. The liquid crystal display device of claim 22, wherein at least one of the first polymer film and the second polymer film further comprises an inorganic oxide.

24. The liquid crystal display device of claim 22, wherein at least one of the first polymer film and the second polymer film has concavo-convex pattern on a surface opposite the light conversion layer.

27. The liquid crystal display device of claim 15, wherein in Chemical Formula 2, X is (meth)acrylate and a C3 to C30 alicyclic hydrocarbon group including a carbon-carbon double bond, L₂ is a C1 to C20 alkylene group;

Y₂ is a single bond;

n is 1;

k3 is 0;

k4 is 2; and

the sum of n and k4 is 3.

28. The liquid crystal display device of claim 27, wherein the second monomer comprises tricyclodecane dimethanol diacrylate.