KR20180074288A - Light Diffusing Sheet for Back-light Unit - Google Patents

Abstract

The present invention relates to a light diffusing sheet for a backlight unit which includes: a base film; and a light diffusing layer that is formed by spreading a binder resin in combination with organic particles coated with an inorganic material on one side of the base film. According to the light diffusing sheet for a backlight unit of the present invention, light from a light emitting diode (LED) lamp is uniformly diffused and shielded by spreading the organic particles having the inorganic material coated on a surface thereof in a multi-layer manner so that generation of a lamp mura is restrained, and an excellent viewing angle is assured. Furthermore, in the sheet of the present invention, it is easy to disperse particles in manufacturing a coating liquid for the light diffusing layer using the organic particles coated with the inorganic material.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light diffusing sheet for a backlight unit,

The present invention relates to a light diffusion sheet for a backlight unit, and more particularly, to a light diffusion sheet for a backlight unit, which diffuses light from a lamp to spread light uniformly throughout the screen, thereby suppressing lamp mura defects and improving brightness and viewing angle To a light diffusion sheet for a backlight unit.

Generally, a light diffusion sheet for an LCD backlight unit is widely used for small and medium sized displays such as mobile phones and tablets, and medium and large size displays for notebooks, desktop monitors, and televisions.

The LCD backlight unit is classified into an edge type in which a linear LED lamp is installed in a horizontal or vertical direction on a screen frame and a direct type backlight unit in which an LED lamp is mounted on the entire screen. The edge type backlight unit which is supplied only from one side is mainly used for small backlights such as monitors for mobile phones, notebooks and desktops, and the direct type is mainly used for large size backlights such as televisions.

Especially, in the UHD (Ultra High Definition) TV industry of recent 4K or more, the efficiency of LED lamps is increased and the number of lamps is reduced for cost reduction in order to develop backlight units having high luminance and thin thickness characteristics. As a result, the occurrence of lamp blur is easier, and a luminance deviation is severely generated depending on the position of the backlight unit.

The conventional direct-type backlight unit uses a light diffuser to diffuse light to mitigate lamp muffler. However, since the thickness of the light diffuser plate is thicker than 1.5T, slimming down of the backlight unit is limited. As shown in FIG. 1, the conventional light diffusion film is excellent in terms of brightness, but has a problem that it is difficult to use because it has less hiding power and diffusibility than a light diffusion plate, and FIG. 2 (Korean Patent Application No. 2010-0124832) Conventionally, organic particles and inorganic particles having different refractive indexes are mixed and used to improve the brightness, but there is a limit in terms of suppressing the generation of lamp blur.

Since the brightness of the LED lamp is continuously increasing and the number of lamps used is reduced, the diffusion and shielding of the light from the LED lamp is becoming very important. For the display of high resolution, a wide angle of view . Accordingly, the inventors of the present invention prepared a light diffusion sheet in which the organic particles were coated on at least one surface of the base film in multiple layers using organic particles coated with an inorganic material on the surface, and the prepared light diffusion sheet has improved lamp- Wide viewing angle.

Patent Document 1: Korean Patent Application No. 2013-0037370 Patent Document 2: Korean Patent Application No. 2010-0124832

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved light diffusion sheet by suppressing occurrence of lamp shattering and widening a viewing angle.

A light diffusion sheet for a backlight unit of the present invention comprises a base film; And a light diffusing layer coated on the at least one surface of the base film with a multilayered mixture of organic particles coated with an inorganic material in a binder resin.

And the average particle size of the organic particles coated with the inorganic material is 0.5 to 60 占 퐉.

The refractive index of the organic particles is 1.35 to 1.55, and the refractive index of the inorganic material is 1.50 to 2.75.

The organic particles may be selected from the group consisting of acrylic, styrene, silicone, nylon, and urethane, or a mixture of two or more thereof.

The inorganic material is characterized by being a single material or a mixture of two or more materials selected from the group consisting of silica, titanium oxide and alumina.

The light diffusion layer is characterized in that the weight ratio of the binder resin to the organic particles coated with the inorganic material is 1: 1.0 to 1: 1.5.

And the refractive index of the binder resin is 1.35 to 1.55.

The light diffusion sheet has a haze of 90 to 95% and a transmittance of 50 to 85%.

The light diffusion sheet for a backlight unit of the present invention includes organic particles coated with a binder resin and an inorganic material on the light diffusion layer and is applied on the surface of the base film in multiple layers to thereby have high brightness and an improved viewing angle, Is excellent.

FIG. 1 is a schematic cross-sectional view of a light diffusion sheet for an edge type backlight unit in which shielding performance is improved by coating organic particles in multiple layers to improve lamp shading.
2 is a schematic cross-sectional view of a light diffusion sheet for a backlight unit in which brightness and shielding performance are improved by mixing organic particles and inorganic particles in a conventional light diffusion layer.
3 is a schematic cross-sectional view of a light diffusion sheet for a backlight unit including organic particles coated with an inorganic material on a light diffusion layer according to the present invention.

3 is a cross-sectional view of a light diffusion sheet for an LCD backlight unit to which an LED lamp according to a preferred embodiment of the present invention is applied.

As shown in FIG. 3, the light diffusion sheet for a backlight unit of the present invention comprises a base film 3; Wherein at least one surface of the base film (3) is composed of a light diffusing layer in which a binder resin (1) and organic particles (5) coated with an inorganic material are combined on the surface, wherein the light diffusing layer . The binder resin 1 is filled between the organic particles 5 coated with the inorganic material so that the light emitted from the LED lamp is effectively transmitted, thereby preventing a decrease in luminance and widening the viewing angle.

In the organic particles coated with the inorganic material, the organic particles and the inorganic material are spherical or amorphous. The organic particles may be used alone or in combination of two or more selected from the group consisting of acrylic, styrene, silicone, nylon, and urethane. The refractive index of the organic particles is preferably 1.35 to 1.55.

The inorganic material may be selected from the group consisting of silica, titanium oxide, alumina, etc., or a mixture of two or more thereof. The refractive index of the inorganic material is preferably from 1.50 to 2.75. Outside the refractive index range of the organic particles and the inorganic material, it has a negative role in improving the luminance and improving the shielding performance.

In order to realize a light diffusion sheet excellent in brightness, viewing angle and shielding against lamp blindness, the organic particles coated with the inorganic material contained in the light diffusion layer preferably have an average particle diameter of 0.5 to 60 탆. If the average particle diameter exceeds 60 탆, the organic particles coated with the inorganic material are excessively precipitated to be difficult to be normally applied to the base film, and the slimming of the backlight unit is hindered, which is not preferable due to an increase in manufacturing cost. If the average particle diameter is less than 0.5 占 퐉, the particles aggregate together and are difficult to disperse, and when the particles of less than 0.5 占 퐉 rise to the upper layer portion, the luminance is lowered.

On the other hand, it is preferable that the composition of the coating liquid applied to the base film (3) is 1: 1.0 to 1: 1.5 by weight ratio of the binder resin (1) and the organic particles (5) coated with the inorganic material. Excessively larger or smaller number of particles out of the above-described ratio may deteriorate the shielding ability and deteriorate the luminance and viewing angle performance.

The binder resin (1) has a refractive index of 1.35 to 1.55 and is colorless and transparent. The binder resin (1) can be used singly or in combination of two or more kinds in the group including acrylic, urethane, epoxy, polyester and polyamide. If the refractive index of the binder resin does not reach 1.35, the transmittance increases to lower the shielding property. If the refractive index exceeds 1.55, the transmittance decreases and the brightness decreases.

The thickness of the light diffusion layer composed of the binder resin and the inorganic particles coated with the organic particles is 5 to 60 탆. When the thickness of the light-diffusing layer is less than 5 mu m, it is difficult to impart shielding characteristics. When the thickness of the light-diffusing layer is more than 60 mu m, the shielding property is improved, but the light transmittance is remarkably decreased.

The base film (3) is a transparent polycarbonate film or polyethylene terephthalate film having a transmittance of 60% or more.

The light-diffusing sheet for a backlight unit of the present invention has a haze of 90 to 95% and a transmittance of 50 to 85%.

Hereinafter, the present invention will be described in detail with reference to examples. The following examples illustrate the present invention, but the scope of the present invention is not limited to the following examples.

The binder resins (refractive index: 1.49) used in Examples and Comparative Examples are all the same, and the types of organic particles coated with inorganic materials are as follows.

≪ Example 1 >

On both sides of a transparent polyester film (Toray Advanced Material, XG5P2 125 占 퐉), a coating liquid having the following composition was formed using a microgravure roll to form a coating layer.

Composition of coating liquid

- Binder resin (Acrylic, Aekyung Chemical Co., Ltd., AA-914): 25.0 wt%

- Curing agent (urethane system, Aekyung Chemical Co., Ltd., AH2100): 5.0 wt%

가 코팅된 PMMA, Soken, MT5R-10HH) : 25.0 중량%- Organic particles coated with inorganic material (

Coated PMMA, Soken, MT5R-10HH): 25.0 wt%

Solvent (methyl ethyl ketone): 45.0 wt%

≪ Example 2 >

On both sides of a transparent polyester film (Toray Advanced Material, XG5P2 125 占 퐉), a coating liquid having the following composition was formed using a microgravure roll to form a coating layer.

Composition of coating liquid

- Binder resin (Acrylic, Aekyung Chemical Co., Ltd., AA-914): 25.0 wt%

- Curing agent (urethane system, Aekyung Chemical Co., Ltd., AH2100): 5.0 wt%

가 코팅된 실리콘, KOLON, KS500-T10) : 25.0 중량%- Organic particles coated with inorganic material (

Coated silicon, KOLON, KS500-T10): 25.0 wt%

Solvent (methyl ethyl ketone): 45.0 wt%

≪ Example 3 >

On both sides of a transparent polyester film (Toray Advanced Material, XG5P2 125 占 퐉), a coating liquid having the following composition was formed using a microgravure roll to form a coating layer.

Composition of coating liquid

- Binder resin (Acrylic, Aekyung Chemical Co., Ltd., AA-914): 25.0 wt%

- Curing agent (urethane system, Aekyung Chemical Co., Ltd., AH2100): 5.0 wt%

가 코팅된 PBMA, KOLON, Coffee 8-T10) : 25.0 중량%- Organic particles coated with inorganic material (

Coated PBMA, KOLON, Coffee 8-T10): 25.0 wt%

Solvent (methyl ethyl ketone): 45.0 wt%

≪ Comparative Example 1 &

On both sides of a transparent polyester film (Toray Advanced Material, XG5P2 125 占 퐉), a coating liquid having the following composition was formed using a microgravure roll to form a coating layer.

Composition of coating liquid

- Binder resin (Acrylic, Aekyung Chemical Co., Ltd., AA-914): 25.0 wt%

- Curing agent (urethane system, Aekyung Chemical Co., Ltd., AH2100): 5.0 wt%

- Organic particles (PMMA, Soken, MX500): 25.0 wt%

Solvent (methyl ethyl ketone): 45.0 wt%

≪ Comparative Example 2 &

On both sides of a transparent polyester film (Toray Advanced Material, XG5P2 125 占 퐉), a coating liquid having the following composition was formed using a microgravure roll to form a coating layer.

Composition of coating liquid

- Binder resin (Acrylic, Aekyung Chemical Co., Ltd., AA-914): 25.0 wt%

- Curing agent (urethane system, Aekyung Chemical Co., Ltd., AH2100): 5.0 wt%

- Organic particles (silicone, Kolon, KS-500): 25.0 wt%

Solvent (methyl ethyl ketone): 45.0 wt%

<Experimental Example>

The properties of the sheets prepared in Experimental Examples 1 to 3 and Comparative Examples 1 and 2 were measured as described below and are shown in Table 1.

1. Light diffusion sheet thickness measurement

The thickness of the light-diffusing sheet was measured using a side pressure measuring instrument (Mitsutoyo Corporation, Model: ID-FF125) using a micrometer.

2. Measurement of haze and transmittance

Haze used a haze meter (NIPPON DENSHOKU KOGYO Co. Ltd. Model 1000) manufactured by Nippon Denshoku Co., Ltd. according to ASTM D-1003.

3. Measurement of luminance

For the manufactured light diffusing sheet, the vertical luminance of the assembled backlight unit was measured using BM-7 equipment of Topcon.

4. Adhesion measurement

100 square cells were fabricated using a cross cutter (NITTO DENDKO) and the degree of peeling was measured using a 3M magic tape.

○: When the square cell does not fall off at all

X: One square cell is missing

5. Shielding force measurement

The manufactured light diffusing sheet was assembled into a direct-type backlight unit (LC320DXN-SE-R2) using an LED lamp, and the degree of lamp shattering was confirmed using a CA-2000 apparatus manufactured by Minolta Co.,

Bad Good Great

Lamp Mura

6. Measurement of viewing angle

For the manufactured light diffusing sheet, the backlight unit was assembled using BM-7 equipment of Topcon Co., and the BM-7 was fixed to the center of the backlight unit. Then, the brightness was measured in units of 1 ° from -80 ° to 80 ° do. A half value (half value) of the maximum luminance value is calculated, and a viewing angle is measured by calculating an angle corresponding to the semi-luminance value.

division Thickness (㎛) Haze (%) Transmittance (%) Luminance (cd / cm ² ) Adhesion Shielding Force Viewing angle Example 1 155 탆 92.42% 64.30% 9787 ○ Great 51.1˚ Example 2 156 탆 91.31% 65.40% 9704 ○ Good 51.2˚ Example 3 155 탆 91.33% 65.30% 9630 ○ Good 51.4˚ Comparative Example 1 155 탆 89.10% 71.10% 9831 ○ Bad 51.0˚ Comparative Example 2 155 탆 89.50% 72.30% 9747 ○ Bad 51.3˚

Examples 1 to 3, in which inorganic particles are coated on the surface of the organic particles, show excellent characteristics in shielding the lamps when comparing the shielding forces of Examples 1 to 3 and Comparative Examples 1 and 2 in Table 1 You can see what you see.

1 - binder resin
2 - organic particles
3 - substrate film
4-inorganic particles
5 - Organic particles coated with inorganic material

Claims (8)

A base film; And a light diffusing layer formed by coating at least one side of the base film with organic particles coated with an inorganic material on a binder resin and coated in multiple layers. The light diffusion sheet for a backlight unit according to claim 1, wherein an average particle diameter of the organic particles coated with the inorganic material is 0.5 to 60 탆. The light diffusion sheet for a backlight unit according to claim 1, wherein the refractive index of the organic particles is 1.35 to 1.55, and the refractive index of the inorganic material is 1.50 to 2.75. The light diffusion sheet for a backlight unit according to claim 1, wherein the organic particles are selected from the group consisting of acrylic, styrene, silicone, nylon, and urethane. The light diffusion sheet for a backlight unit according to claim 1, wherein the inorganic material is selected from the group consisting of silica, titanium oxide, and alumina. The light diffusion sheet for a backlight unit according to claim 1, wherein the weight ratio of the binder resin to the organic particles coated with the inorganic material is 1: 1.0 to 1: 1.5. The light diffusing sheet for a backlight unit according to claim 1, wherein the refractive index of the binder resin is 1.35 to 1.55. The light diffusion sheet for a backlight unit according to claim 1, wherein the light diffusion sheet comprising a base film and a light diffusion layer has a haze of 90 to 95% and a transmittance of 50 to 85%.

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