WO2013039268A1

WO2013039268A1 - Back-light unit and lcd using the same

Info

Publication number: WO2013039268A1
Application number: PCT/KR2011/006767
Authority: WO
Inventors: Kwang Ho Park; Moo Ryong Park; Byoung Eon Lee; Sic Hur
Original assignee: Lg Innotek Co., Ltd.
Priority date: 2011-09-14
Filing date: 2011-09-14
Publication date: 2013-03-21

Abstract

Provided is a back-light unit. A back-light unit includes a plurality of LED light sources disposed on a printed circuit board on which a reflective film is stacked; a resin layer stacked on the LED light sources to diffuse and guide emitted light forward; and a diffusion plate printed with optical patterns light-shielding and reflecting light passing through the resin layer, wherein the optical pattern is formed using light shielding ink including an acryl polyol resin, a hydrocarbon-based and ester-based solvent, and a pigment.

Description

BACK-LIGHT UNIT AND LCD USING THE SAME

The present invention relates to a back-light unit and a liquid crystal display (LCD) using the same capable of making a structure of a back-light unit thin while securing light efficiency, by removing a structure of a light-guide plate.

A liquid crystal display (LCD) is a display capable of controlling desired images by individually supplying data signals according to image information to pixels arranged in a matrix form to control light transmittance of pixels. However, since the LCD is not a self-emitting device, the LCD is designed to display images by mounting a back-light unit on a back surface thereof.

Referring to FIG. 1, a back-light device 1 is configured to include a flat light-guide plate 30 disposed on a substrate 20 and a plurality of side view LEDs 10 (showing only one LED) disposed in an array type on a side of the light-guide plate 30.

Light L incident on the light-guide plate 30 from the LED 10 is reflected upward by a fine reflective pattern or a reflective sheet 40 disposed on a bottom surface of the light-guide plate 30 and is emitted from the light-guide plate 30. Thereafter, back-light is provided to an LCD panel 50 over the light-guide plate 30.

As shown in FIG. 2, the back-light unit may be formed to have a structure in which a plurality of optical sheets, such as a diffusion sheet 31 or

prism sheets

32 and 33, a protective sheet 34, or the like, are further disposed between the light-guide plate 30 and the LCD panel 50.

The back-light unit serves to uniformly project light on a back surface of the LCD that does not emit light itself, so as to display images on the back surface of the LCD. Further, the light-guide plate is a part that performs uniform illumination with luminance of the back-light unit, which is one of plastic molded lenses uniformly transferring light emitted from a light source (LED) to the overall surface of the LCD. Therefore, the light-guide plate is basically used as an essential part of the back-light unit. As a result, there is a limitation in making an overall thickness of a product thin due to a thickness of the light guide plate. Further, in the case of a large-area back-light unit, image quality may be deteriorated.

Further, a diffusion plate or a diffusion sheet 31 used for diffusing light to the back-light unit of the related art is provided with a light shielding pattern so as to prevent light from being concentrated. The light shielding pattern implements a light shielding effect using Ag. However, optical patterns using Ag implementing the light shielding effect may be hard to secure overall uniformity of light due to complete light shielding at a pattern portion, thereby lowering reliability of the back-light unit finally emitting white light due to emission of yellow light generated from an LED light source itself.

An aspect of the present invention is directed to a back-light unit and a liquid crystal display using the same capable of reducing the number of light sources, making an overall thickness of the back-light unit thin, and increasing a degree of freedom in a design of a product securing tensile strength, reliability for constant temperature and humidity, and heat resistance reliability, by removing an essential light-guide plate from a structure of a general back-light unit and forming a structure that guides a light source using a resin layer using oligomer as main component.

In addition, another aspect of the present invention is directed to provide a back-light unit capable of deriving reliable quality of light by applying light shielding ink capable of implementing optical patterns light-shielding or diffusing light to a surface of a diffusion plate of the back-light unit and securing uniformity of light and implementing an effect of shielding yellow light through a combination of a diffusion pattern and a metal pattern.

According to an embodiment of the present invention, there is provided a structure for reducing the number of light sources while remarkably reducing an overall thickness of a back-light unit, by removing a light-guide plate from a structure of the back-light unit of the related art and forming a resin layer using oligomer as main component and including a polymer type of resin such as poly acryl, or the like.

According to another embodiment of the present invention, there is provided a back-light unit further including: a plurality of LED light sources that are disposed on a printed circuit board so as to increase light efficiency by forming a diffusion plate including an optical pattern layer shielding and diffusing light; a resin layer that is stacked in a structure in which the LED light sources are embedded on the printed circuit board to diffuse and guide emitted light forward; and the diffusion plate that is formed on a top surface of the resin layer and has optical patterns shielding or reflecting the emitted light printed thereon.

As set forth above, the exemplary embodiments of the present invention is directed to a back-light unit and a liquid crystal display using the same capable of reducing the number of light sources, making the overall thickness of the back-light unit thin, and increasing a degree of freedom in a design of a product securing tensile strength, reliability for constant temperature and humidity, and heat resistance reliability, by removing the essential light-guide plate from the structure of the general back-light unit and forming the structure that guides the light source using the resin layer using the oligomer as main component.

In particular, the exemplary embodiments of the present invention can configure the resin layer using the blended composition of the oligomer type and the polymer type to increase the productivity and reliability of the oligomer type and improve the adhesive characteristics of the polymer type, thereby implement the higher quality of products.

Further, the exemplary embodiments of the present invention can mount the side view light emitting diode in a direct type so as to secure the optical characteristics while remarkably reducing the number of light sources, remove the light-guide plate so as to be applied even to the flexible display, and include the reflective film having the reflective pattern and the diffusion plate including the shielding pattern that are disposed on the resin layer, thereby securing the stable light emitting characteristics.

Further, the exemplary embodiments of the present invention can derive the reliable quality of light by applying the light shielding ink capable of implementing the optical patterns shielding or diffusing light to the surface of the diffusion plate of the back-light unit and securing the uniformity of light and implementing the effect of shielding yellow light through the combination of the diffusion pattern and the metal pattern.

The above and other aspects, features and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIGS. 1 and 2 are conceptual diagrams showing a structure of a back-light unit according to the related art;

FIG. 3 is a conceptual diagram showing main parts of a structure of a back-light unit according to an exemplary embodiment of the present invention;

FIG. 4 is an operational status diagram showing functions of a resin layer and a bead of the back-light unit according to the exemplary embodiment of the present invention;

FIG. 5 is a table showing an implementation example of compositions forming the resin layer according to the exemplary embodiment of the present invention;

FIG. 6 is an exemplified diagram showing optical patterns according to the exemplary embodiment of the present invention;

FIG. 7 is a diagram showing a manufacturing example implementing the optical patterns according to the exemplary embodiment of the present invention;

FIG. 8 is a table showing a composition example of ink configuring optical patterns and reflective patterns according to the exemplary embodiment of the present invention;

FIG. 9 is an exemplified diagram showing the reflective patterns according to the exemplary embodiment of the present invention; and

FIG. 10 is a diagram showing an operational status of the back-light unit according to the exemplary embodiment of the present invention.

110: Printed Circuit Board

111: LED Light Source

120: Reflective Film

130: Reflective Pattern

140: Resin Layer

150: Diffusion Plate

151: Optical Pattern

151a: Diffusion Pattern

151b: Light Shielding Pattern

160: Prism Sheet

Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Wherever possible, the same reference numerals will be used to refer to the same elements throughout the specification, and a duplicated description thereof will be omitted. It will be understood that although the terms first, second , etc. are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element.

1. First Exemplary Embodiment

FIG. 3 is a conceptual diagram of main parts of a back-light unit according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the back-light unit may be configured to include a plurality of LED light sources 111 that are disposed on a printed circuit board 110 and a resin layer 140 that is stacked on the LED light source 111 to diffuse and guide emitted light forward. In this configuration, a reflective film 120 may be stacked on a top surface of the printed circuit board, a diffusion plate 150 may be disposed on a top portion of the resin layer 140, and a prism sheet 160, a protective sheet 170, or the like, may be further disposed on a top portion of the diffusion plate 150.

At least a LED light source 111 is disposed on the printed circuit board 110 to emit light. In this case, in the exemplary embodiment of the present invention, a side view LED may be used. That is, a light source having a structure that light emitted from the LED light source 111 does not directly go straight upward, but is emitted to a side may be used. Further, the side view light emitting diode is disposed in a direct type as a disposition manner, which may result in remarkably reducing an overall thickness of the back-light unit while reducing a total number of light sources using the resin layer implementing light diffusion and reflective functions.

The resin layer 140 is stacked in a structure that surrounds a circumference of the LED light source 111 to serve to disperse light from the light source in a side direction. That is, the resin layer 140 may serve a function of a light-guide plate of the related art. The resin layer may use any resin that can basically diffuse light. In this case, FIG. 4 is a partially enlarged view of a structure of FIG. 3, wherein the resin layer 140 may include a bead 141 so as to increase diffusion and reflection of light.

FIG. 5 is a table showing an exemplary example of compositions forming the resin layer according to the exemplary embodiment of the present invention in the above-mentioned structure.

An example of a main material of the resin layer as an example according to present invention may include a resin (oligomer type) that uses urethane acrylate oligomer as a main raw material. For example, a hybrid of urethane acrylate oligomer that is synthetic oligomer and a polymer type that is poly acryl may be used. Further, a monomer in which a low-boiling diluted reactive monomer, that is, isobornyl acrylate (IBOA), hydroxylpropyl acrylate (HPA), 2-hydroxyethyl acrylate (2-HEA), or the like, are blended may be further included in the hybrid. As additives, a photo initiator (for example, 1-hydroxycyclohexyl phenyl-ketone, or the like), an antioxidant, or the like, may be blended.

In more detail, the resin layer may be composed of a synthetic resin including a hybrid of oligomer and polymer resin (polymer type). In particular, the resin layer may use compositions having a composition of 20 to 42% of the hybrid of oligomer and polymer resin (polymer type), 30 to 63% of monomer, and 1.5 to 6% of additive.

In this case, the oligomer and the polymer resin may be composed of a hybrid of 10 to 21 wt% of urethane acrylate oligomer and 10 to 21 wt% of poly acryl with respect to a total weight of the resin layer. Further, the monomer, which is the low-boiling diluted reactive monomer, may be composed of a hybrid of 10 to 21 wt% of isobornyl acrylate (IBOA), 10 to 21 wt% of hydroxylpropyl acrylate (HPA), and 10 to 21 wt% of 2-hydroxylethyl acrylate (2-HEA). The additive may be composed of a hybrid of 1 to 5 wt% of photo initiator serving to initiate photo reactivity and 0.5 to 1 wt% of antioxidant serving to improve a yellowing phenomenon.

Forming the resin layer using the above-mentioned compositions may replace the effects of the light-guide plate of the related art by forming a resin layer such as UV resin, or the like, instead of the light-guide plate and may supplement a degradation in surface adhesion that is a disadvantage of the oligomer type by using the above-mentioned compositions while controlling a refractive index and a thickness and satisfy adhesive characteristic, reliability and a production speed by removing a degradation problem of a production speed due to long-time curing of the polymer type.

In particular, the resin layer according to the exemplary embodiment of the present invention may be formed by a special process.

That is, the resin layer according to the exemplary embodiment of the present invention uses the urethane acrylate oligomer as a main material. The resin layer performs main reaction at an UV curing wavelength of 300 to 350 mm by blending the urethane acrylate oligomer is blended with the polymer type that is poly acryl and introduces N₂ at the time of curing the polymer type at a wavelength of 400 mm using a mercury lamp and a metal (gallium) lamp to control curing balance together with a general oligomer type, such that the resin layer may obtain excellent flexibility and adhesion and maintain a refractive index of a PMMA light-guide plate, thereby overcoming a limitation in the light-guide plate.

In particular, when nitrogen purging is not performed at the time of a hybrid of polymer and oligomer, a surface crease and crack phenomenon may occur due to internal curing and surface curing balance. The characteristic of the present invention performs the nitrogen purging and as a result, rapid curing may be implemented even in general metal halide, or the like.

Hereinafter, as shown in FIG. 5, comparative experiment results of characteristics of a resin layer (1 type) made of only polymer, a resin layer (2 type) made of only oligomer, a resin layer (3 type) made of a hybrid of oligomer and polymer according to the exemplary embodiment of the present invention will be described.

1.1. Adhesive (tensile strength) Reliability Test

The present test measured the tensile strength using a thin film tension tester (Instron Co. (USA)). Upper and lower grips of equipment were each provided with the resin layer having a coating thickness of 1300 mm and an area of length × width (50 mm×100 mm). Results of comparing and observing a load applied to a rod cell in real time while the upper grip moving up were shown (a test condition is 0.1 m per minute).

[Table 1]

It could be appreciated from the above test results that a single type of oligomer shown low tensile strength but the 3 type according to the exemplary embodiment of the present invention shown tensile strength equivalent to the polymer type that is 1 type.

2.2. Constant Temperature and Humidity Reliability Test

The present test compared constant temperature and humidity characteristics by applying constant temperature and humidity to a chamber using a constant temperature and humidity chamber (temperature humidity bias (THB), THB SH-641/ESPEC Co. (Japan)). Characteristics were compared after 60 C and humidity of 95% as test conditions are maintained for 240 hours (as shown in FIG. 2, the structure in which the reflective film is disposed on the printed circuit board and the resin layer is disposed thereon was an object of an experiment).

The resin layer having a coating thickness of 1300 ㎛ and an area of length ×width (115 mm ×175 mm) was disposed on the above-mentioned reflective film and the appearance and lighting tests thereof were compared after the above-mentioned test conditions are applied.

[Table 2]

Referring to shown Table, the 3 type according to the exemplary embodiment of the present invention and the 2 type that is the resin layer made of only oligomer formed blue light and did not change the attachment degree, but the 1 type that is the resin layer made of only polymer caused the yellowing phenomenon at the front portion and causes the whitening phenomenon. Further, the defect in the attachment characteristic also occurred.

3.3. Heat Resistance Reliability Test

The present test evaluated and compared heat resistance of the product by applying predetermined heat to an oven (HT330/ETAC Co. (Japan)) for predetermined time. The heat resistance and attachment characteristics of the resin layer were compared after 240 hours at 80℃ that are test conditions. In a test method, the resin layer having a coating thickness of 1300 ㎛ and an area of length ×width (115 mm ×175 mm) was disposed on the above-mentioned reflective film of FIG. 2 and the appearance and lighting tests thereof were compared after the above-mentioned test conditions are applied.

[Table 3]

In the present test, the 3 type according to the exemplary embodiment of the present invention and the 2 type that is the resin layer made of only oligomer formed blue light and did not change the attachment degree, but the 1 type that is the resin layer made of only polymer caused a defect in which the yellowing phenomenon occurs at the front portion.

Comparing the above-mentioned three characteristic tests, it could be appreciated that the resin layer having the compositions of the blending type of oligomer and polymer is more efficient in terms of various aspects such as tesnsile strength, constant temperature and humidity characteristic, heat resistance, reliability, attachment characteristic, or the like, than the single resin layer.

Referring to the structure of the present invention shown in FIGS. 3 and 4, the action of the configuration of the unique back-light unit according to the exemplary embodiment of the present invention will be described below in detail with reference to the characteristics of the above-mentioned resin layer.

In the back-light unit according to the exemplary embodiment of the present invention, the resin layer 140 may further include the bead 141 so as to increase the diffusion and reflection of light. 0.01 to 0.3% of the bead 141 with respect to a total weight of the resin layer may be provided. That is, the light emitted in a lateral direction from the LED is diffused and reflected through the resin layer 140 and the bead to be progressed upward. Further, when the reflective film 120 and the reflective patterns 130 to be described below are provided, the reflective function may be more promoted. The thinness of all the products can be implemented by remarkably reducing the thickness occupied by the light-guide plate of the related art due to the presence of the resin layer. Further, all the products may be made of flexible material and thus, have generality that can also be applied to a flexible display.

In addition, the reflective film 120 may include the reflective patterns 130 through white printing so as to promote dispersion of light while being made of a reflective material so as to disperse light emitted from the light source. The reflective patterns may be printed using the reflective ink including any one of TiO₂ and Al₂O₃.

Further, the diffusion plate 150 serves to diffuse light emitted through the resin layer 140. In particular, in order to prevent optical characteristics from being deteriorated or yellow light from being yellowished due to excessive strength of light, a predetermined portion of the optical patterns 151 may be formed so as to implement the light shielding effect. That is, the light shielding pattern may be printed using the light shielding ink so that light is not concentrated.

2.2. Second Exemplary Embodiment

Hereinafter, a structure of a back-light unit in which a diffusion plate and optical patterns are further provided in addition to the above-mentioned first exemplary embodiment will be described.

One surface of the above-mentioned diffusion plate 150 in FIGS. 3 and 4 may be provided with the optical patterns 151, which may solve the problem of the deterioration of the optical characteristics by shielding the concentration of light.

The optical patterns 151 may be basically implemented in a manner in which the optical patterns 151 are printed on the bottom surface or the top surface of the diffusion plate 150. In particular, preferably, the optical patterns may be disposed in a direction (front direction) in which light is emitted from a position of the LED light source 111 disposed on the bottom portion of the diffusion plate. That is, the optical patterns may be disposed on the diffusion plate at a position corresponding to a vertical top surface or a light emitting directional surface of the LED light source.

In order to partially shield and diffusion light, not completely shield light, the optical patterns may be implemented so as to control the light shielding degree or the diffusion degree of light using a single optical pattern. More preferably, the optical patterns according to the exemplary embodiment of the present invention may be implemented by an overlapping printing structure of a complex pattern. The overlapping printing structure means a structure implemented by forming a single pattern and printing another pattern shape thereon.

As an example, referring to FIG. 6, the optical patterns 151 may be implemented by the overlapping printing structure of diffusion patterns 151a formed using the light shielding ink including any one selected from TiO₂, CaCO₃, BaSO₄, Al₂O₃, and silicon on the bottom surface of the diffusion plate in the light emitting direction and light shielding patterns 151b using the light shielding ink including the hybrid material of Al or Al and TiO₂. That is, the diffusion patterns 151a are formed on the surface of the diffusion plate by the white printing and then, the light shielding patterns 151b are formed thereon; however, may be formed to have a double structure in a reverse order. Further, it is apparent that the formation design of the patterns may be variously changed in consideration of the efficiency, strength, and light shielding rate of light.

Alternatively, the optical patterns may be formed in a triple structure that implements a metal pattern, that is, the light shielding patterns 151b disposed on a middle layer and the diffusion patterns 151a each disposed on the top and bottom portions thereof in the sequential stacking structure. In the triple structure, the optical patterns may be implemented by selecting the above-mentioned materials. As an exemplary example, the efficiency and uniformity of light may be secured through the triple structure in which one of the diffusion patterns is implemented using TiO₂ having the excellent refractive index, another diffusion pattern may be implemented using CaCO₃ having excellent light stability and color sense together with TiO₂ and the light shielding pattern is implemented using Al having excellent masking property is implemented. In particular, the CaCO₃ serves to finally implement the white light through a function of reducing the exposure of yellow light, thereby more stably implementing the light efficiency. In addition to the CaCO₃, the particle sizes of BaSO₄, Al₂O₃, silicon bead, or the like, may be large and inorganic materials having a similar structure may be used.

Further, it is preferable to form the optical patterns by controlling pattern density so as to reduce the pattern density as the optical patterns are far away from the emitting direction of the LED light source, in terms of the light efficiency.

In addition, the structure of the back-light unit according to the exemplary embodiment of the present invention, in particular, the structure of FIGS. 3 and 4, the exemplary embodiment of the present invention further includes a surface treatment layer 152 capable of planarizing a pattern unevenness of the optical patterns between the resin layer 140 and the optical patterns 151 disposed on the surface of the diffusion plate 150, which may be implemented as a planarized layer having a structure covering all the steps of the optical pattern 151 so as to remove a difference between a dark portion and a bright portion generated due to an air layers formed due to the steps generated at the time of bonding the optical pattern 151 of the diffusion plate with the resin layer 140 disposed thereunder. Further, the surface treatment layer is basically to improve adhesion using the same material as the resin layer 140.

FIG. 7 shows a process view of forming the optical patterns and FIG. 8 shows an example of a composition of the light shielding ink and the reflective ink configuring the above-mentioned optical pattern and reflective pattern. In 1-degree, 2-degree, and 3-degree light shielding ink suggested in Table shown, a composition example in which 1-degree and 2-degree each implement the diffusion pattern and 2-degree implements the light shielding pattern is shown. The structure of the above-mentioned light shielding ink may be changed according to the structure of the optical pattern.

Referring to FIGS. 7 and 8, the optical patterns according to the exemplary embodiment of the present invention may be formed in a structure in which the optical patterns are printed on the top or bottom surface of the diffusion plate 150. FIG. 7A shows a structure of implementing 1-degree printing so that the optical pattern is formed in one pattern layer (first pattern: 151a), FIG. 1B shows a structure in which the second pattern 151b is overlappingly printed on the first pattern, or FIG. 7C shows a triple layer structure in which the first and second patterns are printed and then, a third pattern is overlappingly printed thereon. The overlapping printing structure means a structure implemented by forming a single pattern and printing another pattern shape thereon.

(1) Implement Optical Pattern With Diffusion Pattern Of Single Layer

As shown in FIG. 7A, when implementing the optical patterns through the printing on the surface of the diffusion plate 150, the optical pattern may be formed in a structure including the single diffusion pattern.

That is, it is preferable to implement the diffusion effect while effectively implementing the light shielding effect by performing the printing using the light shielding ink basically including TiO₂. In this case, the light shielding ink may be implemented as a structure in which inorganic pigments such as TiO₂, or the like, are added to, for example, a resin agent, that is, a resin such as acryl polyol, or the like, and a hydrocarbon-based or ester-based solvent. In particular, the light shielding ink may be implemented by further including additives such as a silicon type of wetting dispersant or forming agent/leveling agent, or the like, in addition thereto. In addition, as the inorganic pigments, TiO₂ or at least any one selected from CaCO₃, BaSO₄, Al₂O₃, and Silicon added to TiO₂ may be used. In the case of the 3-degree light shielding ink, a hybrid of 20 to 25% of acryl polyol resin, 20 to 29% of solvent (5 to 10% of hydrocarbons, 15 to 19% of esters), 50 to 55% of TiO₂ as the inorganic pigment, and 1 to 2% of additives (0.5 to 1% of silicon-based wetting dispersant, 0.5 to 1% of a silicon type of foaming agent/leveling agent to a total weight of the light shielding ink may be used. In this case, the inorganic pigments of which the particle size is 500 to 550 nm may be used.

Alternatively, the diffusion pattern of the single layer may use the light shielding ink of FIG. 1.

That is, As in the 3-degree light shielding ink, a hybrid of 20 to 25% of acryl polyol resin, 20 to 29% of solvent (5 to 10% of hydrocarbons, 15 to 19% of esters), 15 to 20% of TiO₂ as the inorganic pigment, 30 to 35% of CaCO₃, and 1 to 2% of additives (0.5 to 1% of silicon-based wetting dispersant, 0.5 to 1% of a silicon type of foaming agent/leveling agent) to a total weight of the light shielding ink may be used. In this case, the inorganic pigments of which the particle size is 500 to 550 nm may be used. In particular, the fact that the CaCO₃ serves to finally implement the white light through a function of reducing the exposure of yellow light, thereby more stably implementing the light efficiency and in addition to the CaCO₃, the particle sizes of BaSO₄, Al₂O₃, silicon bead, or the like, may be large and the inorganic materials having a similar structure may be used are already described. In this case, the CaCO₃ of which the particle size is 1 to 2 mm may be used.

FIG. 4B is a plan view showing the structure of the reflective film and the reflective pattern according to the exemplary embodiment of the present invention.

That is, the reflective film 120 according to the exemplary embodiment of the present invention is stacked on the printed circuit board and the LED light source 111 is protruded to the outside by penetrating through the holes formed on the reflective film. When the LED light source is implemented as a structure of a side view light emitting type, the number of light sources may be remarkably reduced. The reflective pattern 130 is implemented so as to remarkably improve the reflectivity of light.

As in the shown example, the reflective pattern may be formed in the light emitting direction of the LED light source. In particular, as the reflective pattern is far away from the light emitting direction of the LED light source, the reflective pattern may be disposed so as to increase the pattern density. That is, more increasing the pattern density of the second area 132 far away from the light emitting direction than that of the first area 131 near the light emitting direction may increase the reflectivity. Further, the structure of the pattern may be implemented in various shapes according to design s intention. Further, the formation of the reflective pattern may be implemented by a printing manner using the reflective ink including any one of TiO₂ and Al₂O₃.

(2) Form Optical Pattern Of Double Layer (Diffusion Pattern + Light Shielding Pattern)

As shown in FIG. 7B, the optical patterns having the overlapping printed structure may be implemented.

That is, another optical pattern according to the exemplary embodiment of the present invention may be formed so as to implement a double structure in which the diffusion pattern (first pattern) implementing the diffusion or light shielding effect and the light shielding pattern (second pattern) implementing the light shielding effect are overlappingly printed. That is, the optical pattern may be implemented as a structure in which the first pattern shown in FIG. 7A described above is printed and then, the second pattern through the light shielding ink using a metal-based material is printed on the first pattern. The second pattern may be printed using the light shielding ink including Al or a hybrid material of Al and TiO₂. In addition, the optical pattern may be formed by changing a stacked order of the first pattern and the second pattern.

The second pattern may include a metal-based pigment. Describing the light shielding ink configuring the second pattern as an example, a hybrid material of a resin such as acryl polyol, or the like, a hydrocarbon-based or ester-based solvent, a metal-based pigment, and a wetting dispersant, or additives such as a foaming agent/leveling agent, or the like, may be used. As an example of the composition, the light shielding ink may be made of 36 to 40% of acryl polyol resin, 33 to 40% of solvent, 20 to 25% of inorganic pigment, and 1 to 2% of additives. In addition, 33 to 40% of solvent may be made of a hybrid of 10 to 15% of hydrocarbon-based solvent that is a low-boiling solvent and 23 to 25% of ester-based solvent. The second pattern that is the metal pattern may basically implement the light shielding effect. In this case, the Al used as the inorganic pigment of which the particle size is 5 to 15 mm may be used.

As described in the exemplary embodiment of the present invention, when the stacked structure of two pattern structures of the diffusion pattern and the light shielding pattern is formed, any one the 1-degree light shielding ink and the 3-degree light shielding ink implementing the above-mentioned diffusion pattern may be selected and applied.

(3) Optical Pattern Of Triple Layer Structure (Diffusion Pattern + Light Shielding Pattern + Diffusion Pattern)

As shown in FIG. 7C, the optical patterns according to the exemplary embodiment of the present invention may be formed in the overlapping printing structure of the triple layer structure.

That is, the optical patterns may be implemented as a structure in which the intermediate layer of the optical pattern is implemented as a light shielding pattern layer configured in a metal pattern and the diffusion patterns are implemented on the top and bottom portions of the optical pattern.

The light shielding pattern (second pattern) that is the metal pattern is formed in a pattern printed using the 2-degree light shielding ink including Al or a hybrid material of Al and TiO₂ as described above and the top or bottom portions thereof may be implemented as a structure of forming the diffusion pattern using the above-mentioned 1-degree and 3-degree light shielding ink described in FIG. 7A and 7B. Further, the diffusion patterns stacked on the top or bottom portion of the light shielding pattern may be formed by changing the stacked order.

At any rate, each of the diffusion and light shielding patterns configuring the above-mentioned optical pattern may be formed to have a thickness of 4 to 10 mm.

FIG. 9 is a plan view showing the structure of the reflective film and the reflective pattern according to the exemplary embodiment of the present invention.

That is, the reflective film 120 according to the exemplary embodiment of the present invention is stacked on the printed circuit board and the LED light source 111 is protruded to the outside by penetrating through the holes formed on the reflective film. When the LED light source is implemented as a structure of a side view light emitting type, the number of light sources may be remarkably reduced. In order to reduce the reduction rate, the reflective pattern 130 is implemented so as to remarkably improve the reflectivity of light.

As in the shown example, the reflective pattern may be formed in the light emitting direction of the LED light source. In particular, as the reflective pattern is far away from the light emitting direction of the LED light source, the reflective pattern may be disposed so as to increase the pattern density. That is, more increasing the pattern density of the second area 132 far away from the light emitting direction than that of the first area 131 near the light emitting direction may increase the reflectivity. Further, the structure of the pattern may be implemented in various shapes according to design s intention. Further, the formation of the reflective pattern may be implemented by the printing manner using the reflective ink including any one of TiO₂ and Al₂O₃.

The composition of the reflective ink configuring the reflective pattern is shown in FIG. 8 as an example. As the reflective ink, a hybrid of 20 to 25% of acryl polyol resin, 20 to 29% of solvent (5 to 10% of hydrocarbons, 15 to 19% of esters), 50 to 55% of TiO₂ as the inorganic pigment, and 1 to 2% of additives (0.5 to 1% of silicon-based wetting dispersant, 0.5 to 1% of a silicon type foaming agent/leveling agent) to a total weight of the reflective ink may be used.

As shown in FIG. 10, the back-light unit according to the exemplary embodiment of the present invention emits light from the side view LED 111 to the lateral direction. In this case, the emitted light is reflected and diffused from and to the resin layer 140 formed instead of the structure of the light-guide plate of the related art, which more increases the reflectivity by, in particular, the reflective film 120 and the reflective pattern 130 so as to guide light forward. The light passing through the resin layer 140 is subjected to the diffusion or light shielding process through the optical pattern 151 formed on the diffusion plate 150. Light L subjected to the process passes through the optical sheet such as a prism sheet 160, or the like, and as a result, is incident on the LCD panel as white light.

As described above, the back-light unit according to the exemplary embodiment of the present invention can implement the thinness and reduce the number of light sources by removing the structure of the light-guide plate, the side view LED as the supply source of light, and guiding light by diffusing and reflecting light through the resin layer and can implement the uniformity of image quality by supplementing the problem of the degradation in luminance and the uniformity due to the reduction in the light source through the optical patterns such as the reflective pattern, the light shielding pattern, the diffusion pattern, or the like.

Further, in order to prevent the degradation in the adhesion that may be caused due to the steps of the optical patterns at the time of bonding the resin layer 140 and the diffusion plate 150 and remove the generation of the dark portion due to the formation of the air layer, the surface treatment layer 152 may be further provided so as to implement the reliable back-light unit and may be applied to the liquid crystal display including the same.

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

A back-light unit, comprising:

a plurality of LED light sources disposed on a printed circuit board; and

a resin layer stacked in a structure in which the LED light sources are embedded on the printed circuit board to diffuse and guide emitted light forward,

wherein the resin layer is made of a synthetic resin including a hybrid of oligomer and polymer resin.
The back-light unit of claim 1, wherein the resin layer is made of the synthetic resin further including monomer and additives.
The back-light unit of claim 2, wherein the synthetic resin is a hybrid of 10 to 21% of urethane acrylate oligomer and 10 to 21% of poly acryl to a total weight of the resin layer.
The back-light unit of claim 3, wherein the monomer is configured including a hybrid of 10 to 21% of isobornyl acrylate (IBOA), 10 to 21% of hydroxypropyl acrylate (HPA), and 10 to 21% of 2-hydroxyethyl acrylate (2-HEA) to a total weight of the resin layer.
The back-light unit of claim 4, wherein the additive is 1.5 to 6% to a total weight of the resin layer.
The back-light unit of claim 5, wherein the additive is a hybrid of 1 to 5% of photo initiator and 0.5 to 1% of antioxidant to a total weight of the resin layer.
The back-light unit of claim 1, further comprising: a diffusion plate formed on a top surface of the resin layer and printed with optical patterns light-shielding or reflecting the emitted light.
The back-light unit of claim 7, wherein the resin layer further includes 0.01 to 0.3 % of bead increasing reflection of light to a total weight of the resin layer.
The back-light unit of claim 7, wherein the optical pattern is disposed on one surface of the diffusion plate and is configured in a diffusion pattern implemented in at least one layer or a structure in which a light shielding pattern shielding light is combined on the diffusion pattern layer.
The back-light unit of claim 7, wherein the optical pattern is configured of an overlapping structure of the diffusion pattern formed using light shielding ink including at least any one selected from TiO₂, CaCO₃, BaSO₄, Al₂O₃, and silicon and the light shielding pattern using the light shielding ink including Al or a hybrid material of Al and TiO₂.
The back-light unit of claim 9, wherein the optical pattern is formed using light shielding ink including an acryl polyol resin, a hydrocarbon-based and ester-based solvent, and a pigment.
The back-light unit of claim 11, wherein first light shielding ink forming the diffusion pattern is configured including 20 to 25% of acryl polyol resin, 20 to 29% of hydrocarbon-based and ester-based solvent, and 50 to 55% of inorganic pigment to a total weight of the first light shielding ink.
The back-light unit of claim 12, wherein the inorganic pigment is TiO₂ or Al₂O₃.
The back-light unit of claim 11, wherein second light shielding ink forming the diffusion pattern is configured including 20 to 25% of acryl polyol resin, 20 to 30% of hydrocarbon-based and ester-based solvent, and 45 to 55% of inorganic pigment to a total weight of the second light shielding ink.
The back-light unit of claim 14, wherein the inorganic pigment uses any one selected from CaCO₃, BaSO₄, Al₂O₃, and silicon or a hybrid of the selected any one and TiO₂.
The back-light unit of claim 9, wherein the light shielding pattern configuring the optical pattern is configured using third light shielding ink including the acryl poly resin, the hydrocarbon-based and ester-based solvent, and the inorganic pigment including a metal material.
The back-light unit of claim 16, wherein the third light shielding ink configuring the light shielding pattern includes 36 to 40% of acryl polyol resin, 33 to 40% of hydrocarbon-based and ester-based solvent, and 20 to 25% of metal pigment to a total weight of the third light shielding ink.
The back-light unit of claim 17, wherein the metal pigment includes Al or a hybrid material of Al and TiO₂.
The back-light unit of claim 7, wherein the back-light unit further includes a reflective film on which a reflective pattern stacked on the top surface of the printed circuit board is formed.
The back-light unit cof claim 19, wherein the reflective pattern is formed on the reflective film and the reflective pattern is configured including 20 to 25% of acryl polyol resin, 20 to 29% of hydrocarbon-based and ester-based solvent, and 50 to 55% of inorganic pigment.
The back-light unit of claim 20, wherein the inorganic pigment includes any one of TiO₂ and Al₂O₃.
A liquid crystal display, comprising:

a reflective film on which a reflective pattern stacked on a top surface of a printed circuit board is formed; and

a diffusion plate formed on a top surface of a resin layer and a diffusion plate printed with optical patterns light-shielding or reflecting emitted light,

wherein a side view LED is used as a light source and the resin layer of claim 9 stacked in a structure receiving the light source is used as the light-guide plate.