Back light unit and liquid crystal display using the same

Abstract

Provided is a back light unit comprising a plurality of LED light source formed on a printed circuit board and a resin layer which is laminated on the LED light source and forwardly induces diffusion of the emitted light wherein the resin layer is made of synthetic resin comprising an oligomer. According to the present invention, an essential light guide plate for a general back light unit configuration is removed and a resin layer mainly consisting of an oligomer is used to guide the light source, and thereby decreasing the number of the light source, minimizing luminance variation when the unit is lighted at a high temperature and kept it for a predetermined time period, and implementing excellent heat-resistant property and optical property.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

As shown in FIG. 10, the light shielding pattern 151b, which can be provided in a single monolithic pattern, can have a pattern shape having recesses 153b and protrusions 152b in a light emission direction. Also, as shown in FIG. 10, a maximum distance D1 from the light emitting device 111 to the outermost portion 155b of the part of the light shielding pattern 151b that is not overlapped with the diffusion pattern 151a can be greater than a maximum distance D2 from the light emitting device 111 to the outermost portion 154b of the part of the light shielding pattern 151b that is overlapped with the diffusion pattern 151a. It is also noted that FIG. 10 depicts cross sections of the light shielding pattern 151b and the diffusion pattern 151a and, as seen in FIG. 10, the cross section area of the light shielding pattern 151b can be greater than that of the diffusion pattern 151a.

In addition, the light shielding pattern 151b of a metal layer may be formed as a middle layer among sequentially laminated configurations and then the diffusion pattern 151a may be formed on upper and lower surface of the light shielding pattern as a triple layer. In this triple configuration, the material as described in the forgoing may be used wherein as a preferable example, one of diffusion patterns may be formed using TiO₂ having excellent refraction rate and the other diffusion pattern may be formed using CaCO₃, having excellent light stability and color sense, together with TiO₂ and the light shielding pattern may be formed therebetween using Al shaded excellently, and thereby ensuring light efficiency and uniformity through a triple configuration. Specially, CaCO₃ is used for deducting an expose of yellow light and implementing white light and thereby implementing light of more stable efficiency and further in addition to CaCO₃, BaSO₄, Al₂O₃ and Silicon of inorganic material having a large particle size and similar configuration may be used.

Meanwhile, the optical pattern may be formed by adjusting pattern density in consideration of light efficiency in such manner that as it is far away from the light emission direction of the LED light source, a pattern density is lowed. Further, in the back light configuration as described in the forgoing according to the present invention, a surface treatment layer (not shown) enabling rough patterns of the optical patterns to be flat may be further provided between the resin layer 140 and the optical patterns 151 formed on the surface of the diffusion plate 150, and thereby excluding differences between a dark part and a light part which are caused from an air layer formed by a step difference occurred when the optical patterns 151 of the diffusion plate is adhered to the resin layer 140 placed on the lower part of the optical pattern wherein the surface treatment layer is formed to cover step difference of the entire optical pattern 151 as a flat layer. Additionally, the surface treatment layer may be same material as the resin layer 140 to improve an adhering property.

FIG. 11 is a plane view illustrating configurations of the reflection film and the reflection pattern according to the present invention. That is, the reflection film 120 according to the present invention may be laminated on the printed circuit board and the LED light source 111 may be exposed outside through a hole formed on the reflection film. In a case where the LED light source is formed as the side view LED, the number of the light source can be greatly decrease and further the reflection patterns 130 may be provided to greatly improve reflection rate of light for decreasing the decreasing rate number of the light source.

The reflection patterns may be formed in the light emission direction of the LED light source, as shown in an example of FIG. 11, and specially the patterns are arranged in such a manner that as the reflection patterns are far away from the light emission direction of the LED light source, pattern density thereof increases. That is, the pattern density of a second area 132 disposed farther from the light emission direction than a first area 131 is higher than that of the first area. Of course, configuration of the patterns may be varied depending on a designer's intention. Addition, the patterns may be formed through a printing method using a reflection ink comprising one of TiO₂ and Al₂O₃.

FIG. 12 is view illustrating an operational state of the back light configuration according to the present invention.

As shown in FIG. 12, the back light unit according to the present invention light is emitted sideward from the side view LED 111 and is reflected and diffused through the resin layer 140 formed instead of the prior light guide plate, and reflection rate is increases further through the reflection film 120 and the reflection pattern 130 and thereby allowing light to be guided toward a front direction. The light passing through the resin layer 140 is diffused or shielded through the optical patterns 151 formed on the diffusion plate 150 and the refined light L is entered to the LCD panel as white light through optical sheet of a prism sheet.

As described in the forgoing, in the back light unit according to the present invention, the light guide plate is removed and light is emitted from the side view LED as light supply source, and light is guided through diffusion and reflection using a resin layer, and thereby thinning the back light unit and decreasing number of light source. Further, luminance decreasing and light uniformity problems may be supplemented through the optical patterns such as the reflection pattern, the light shielding pattern and the diffusion pattern and thereby implementing uniform image.

INDUSTRIAL APPLICABILITY

While the invention has been shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present invention.

Claims

1. A back light unit comprising:

a printed circuit board;

a plurality of LED light sources light emitting devices on a the printed circuit board;

a resin layerwhich is laminated on the printed circuit board and buries burying the plurality of LED light sources, wherein the resin layer comprises 10-21% of an oligomer, 30-63% of a monomer, and 1.5-6% of additives light emitting devices;

a diffusion plate disposed on an upper surface of the resin layer; and

an optical pattern disposed between the diffusion plate and the resin layer,

wherein the optical pattern comprises a light shielding pattern and a diffusion pattern on the light shielding pattern, the diffusion pattern comprising a material different from that of the light shielding pattern and having a pattern shape different from that of the light shielding pattern, such that the optical pattern controls the extent of light that is diffused and light that is shielded; first pattern and a second pattern,

wherein the light shielding second pattern has a pattern shape having a recess and a protrusion in a light emission direction different from a pattern shape of the first pattern,

wherein the diffusion pattern shields, reflects, and diffuses light;

wherein the light shielding pattern shields and reflects light,

wherein the diffusion pattern is in contact with a bottom surface of the diffusion plate,

wherein the light shielding first pattern comprises: a first part being in direct physical contact with a part of the diffusion the second pattern and vertically overlapped with the part of the diffusion second pattern, and a second part not vertically overlapped with the LED light source second pattern; and

wherein the diffusion pattern is not overlapped with the LED light source and comprises a first diffusion pattern entirely vertically overlapped with the light shielding pattern, and a second diffusion pattern partially vertically overlapped with the light shielding pattern

wherein the first part is disposed in a light exit direction of the light emitting devices.

2. The back light unit of claim 1, wherein the oligomer is a urethane acrylate oligomer, and

wherein the monomer is formed with a mixture comprising 10-21% of IBOA (isobornyl acrylate). 10-21% of HBA (hydroxybutyl acrylate) and 10-21% of HEMA (hydroxyethyl methacrylate).

3. The back light unit of claim 1, wherein the diffusion pattern further comprises a third diffusion pattern not vertically overlapped with the light shielding pattern.

4. The back light unit of claim 1, wherein the resin layer further comprises the additives containing a photo initiator of 1-5% and an anti-oxidant of 0.5-1% on the basis of the total weight of the resin layer.

5. The back light unit of claim 1, wherein the LED light sources comprise a side view light emitting diode (LED).

6. The back light unit of claim 1, which further comprises a reflection film laminated on an upper surface of the printed circuit board.

7. The back light unit of claim 6, wherein the reflection film further comprises a reflection pattern for reflecting light formed on a surface of the reflection film.

8. The back light unit of claim 7, wherein the reflection pattern is printed-patterned using a reflection ink comprising one selected from a group consisting of TiO₂, CaCO₃, BaSO₄, Al₂O₃, Silicon and PS.

9. The back light unit of claim 1, wherein the diffusion pattern is formed using a light shielding ink comprising one or more selected from a group consisting of TiO₂, CaCO₃, BaSO₄, Al₂O₃ and silicon, and the light shielding pattern is formed using a light shielding ink comprising Al or a mixture of Al and TiO₂.

10. The back light unit of claim 1, wherein the resin layer further comprises beads of 0.01-0.3 wt % on the basis of the total weight of the resin layer for increasing light reflection.

11. The back light unit of claim 10, wherein the beads are one or more selected from a group of silicon, silica, glass bubble, PMMA, urethane, Zn, Zr, Al₂O₃, and acryl.

12. A liquid crystal display provided with a back light, using a side view light emitting diode (LED) as a light source and a resin layer as a light guide plate, which is laminated on a printed circuit board in a structure of burying a light source, and light unit comprising:

a printed circuit board;

a reflection film having a reflection pattern laminated disposed on an upper surface of the printed circuit board, and

a diffusion plate that is formed on an upper surface of the resin layer and printed with an optical pattern that partially shields, partially reflects, and partially diffuses an emitted light;

a plurality of light emitting devices disposed on the printed circuit board;

a resin layer disposed on the reflection film and the plurality of light emitting devices; and

an optical pattern disposed on the resin layer,

wherein the optical pattern is disposed between the diffusion plate and the resin layer, and comprises a light shielding includes a first pattern and a diffusion second pattern on the light shielding pattern, the diffusion pattern comprising a material different from that of the light shielding pattern and having a pattern shape different from that of the light shielding pattern, such that the optical pattern controls the extent of the light that is diffused and the light that is shielded;

wherein the light shielding pattern has a pattern shape having a recess and a protrusion in a light emission direction,

wherein the diffusion pattern shields, reflects, and diffuses light;

wherein the light shielding pattern shields and reflects light;

wherein the diffusion pattern is in contact with a bottom surface of the diffusion plate,

wherein the light shielding pattern comprises a first part being in direct physical contact with a part of the diffusion pattern and vertically overlapped with the part of the diffusion pattern, and a second part vertically overlapped with the LED light source, and

wherein the diffusion pattern is not overlapped with the LED light source and comprises a first diffusion pattern entirely vertically overlapped with the light shielding pattern, and a second diffusion pattern partially vertically overlapped with the light shielding pattern,

wherein the optical pattern includes a first part where the first pattern and the second pattern vertically overlap each other, and a second part where the first pattern and the second pattern do not vertically overlap each other,

wherein a thickness of the first part is greater than a thickness of the second part,

wherein the second pattern comprises a plurality of second unit patterns,

wherein the first pattern is formed such that a pattern density thereof decreases in a light emission direction as distance from the plurality of light emitting devices increases, and

wherein the second pattern is formed such that a pattern density of the plurality of second unit patterns decreases in the light emission direction as distance from the plurality of light emitting devices increases.

13. The liquid crystal display of claim 12, which further comprises a prism sheet or protection sheet laminated on an upper part of the diffusion plate.

14. The light unit of claim 1,

wherein a maximum distance from the light emitting devices to the outermost portion of the second part is greater than a maximum distance from the light emitting devices to the outermost portion of the first part.

15. The light unit of claim 1,

wherein the first pattern has a pattern shape having a recess and a protrusion in a light emission direction.

16. The light unit of claim 1,

wherein the optical pattern shields, reflects, and diffuses light.

17. The light unit of claim 1,

wherein a cross section area of the first pattern is greater than a cross section area of the second pattern.

18. The light unit of claim 17,

wherein a shape of the first pattern is different from a shape of the second pattern.

19. The light unit of claim 1,

wherein the first pattern and the second pattern are formed so that a pattern density is lowered in a light emission direction.

20. The light unit of claim 1,

wherein a portion of the optical pattern is disposed to vertically overlap the light emitting devices.

21. The light unit of claim 1,

wherein the second pattern is laminated under the first pattern.

22. The light unit of claim 12,

wherein a maximum distance from the light emitting device to the outermost portion of the second part is greater than a maximum distance from the light emitting devices to the outermost portion of the first part.

23. The light unit of claim 12,

wherein the first pattern has a pattern shape having a recess and a protrusion in the light emission direction.

24. The light unit of claim 12,

wherein the optical pattern shields, reflects, and diffuses light.

25. The light unit of claim 12,

wherein a cross section area of the first pattern is greater than a cross section area of the second pattern.

26. The light unit of claim 25,

wherein a shape of the first pattern is different from a shape of the second pattern.

27. The light unit of claim 12,

wherein a portion of the optical pattern is disposed to vertically overlap the light emitting device.

28. The light unit of claim 12,

wherein the second pattern is laminated under the first pattern.

29. The light unit of claim 28,

wherein the optical pattern is laminated in dual pattern layers.

30. The light unit of claim 28,

wherein the optical pattern is laminated in triple layers.