KR20080065824A - Multi-layered light diffusion plate having improved thermal resistance and liguid crystal display containing the same - Google Patents

Abstract

A multi-layered light diffusion plate having improved thermal resistance and a liquid crystal display including the same are provided to improve a viewing angle by increasing uniformity of brightness. A multi-layered light diffusion plate(1) having improved thermal resistance includes a light diffusion intermediate layer(2) and a pair of light diffusion surface layers(3) placed on both side surfaces of the light diffusion intermediate layer. A plurality of transparent particles(4) are dispersed on at least one layer among the light diffusion intermediate layer, and the first and second light diffusion surface layers. Glass transition temperatures of the first and second light diffusion surface layers are 10 degrees centigrade higher than the light diffusion intermediate layer. A total thickness of the first and second light diffusion surface layers is above 1/30 of a thickness of the light diffusion intermediate layer.

Description

MULTI-LAYERED LIGHT DIFFUSION PLATE HAVING IMPROVED THERMAL RESISTANCE AND LIGUID CRYSTAL DISPLAY CONTAINING THE SAME}

1 is a schematic cross-sectional view of a multi-layer light diffusing plate of the present invention.

2 is a view briefly showing a light diffuser plate for evaluating luminance and luminance uniformity.

3 is a cross-sectional view schematically showing the liquid crystal display device 100 of the present invention.

* Description of Major Symbols in Drawings *

1 multi-layer light diffusing plate, 2 light diffusing intermediate layer, 3 light diffusing surface layer, 4 transparent fine particles, 5 to 21 luminance measurement points,

100 liquid crystal display device, 110 liquid crystal panel, 120 backlight unit, 130 optical sheet, 130a diffusion sheet, 130b prism sheet, 130c protective sheet, 140 light diffuser, 150 light source, 180 reflective sheet, 190 lower chassis

The present invention relates to a multi-layered light diffusing plate with improved heat resistance and a liquid crystal display device including the same, and more particularly, has excellent light transmittance and light diffusivity, high luminance, and high luminance uniformity, thereby improving viewing angle characteristics. The present invention relates to a multilayer structure light diffusion plate having improved heat resistance and a liquid crystal display device including the same.

 In liquid crystal display devices such as a monitor and a liquid crystal TV, a light diffusion sheet is generally used to make a point light source or a line light source appear as a uniform surface light source. Such a light diffusion sheet should have a high diffusivity so that the rear lamps or contents cannot be seen from the outside and at the same time have a uniform brightness, and also have a high light transmittance to obtain excellent light efficiency (high brightness and low power consumption), In order to secure the viewing angle, it is required to have a high luminance uniformity as a whole.

The light diffusion sheet introduced in the prior art can be divided into the following (1) to (5) and the like.

(1) A light-diffusion sheet as disclosed in Japanese Patent Application Laid-open No. Hei 4-275501 (published on October 1, 1992) and the like, which is formed by molding a transparent thermoplastic resin into a sheet shape and then subjecting the surface of the sheet to physical irregularities. .

(2) A light diffusing sheet or film disclosed in Japanese Patent Application Laid-Open No. 6-059108 (1994.03.04), which is obtained by coating a light diffusing layer made of a transparent resin containing fine particles on a transparent base film such as a polyester resin. .

(3) A light diffusing sheet disclosed in Japanese Patent Laid-Open No. 6-347617 (published on December 22, 1994) and the like, wherein inorganic particles are mixed in a transparent resin and molded into a sheet to give light diffusibility.

(4) As disclosed in Japanese Laid-Open Patent Publication No. 2001-322218 (published on November 20, 2001) and Korean Laid-Open Patent Publication No. 2002-0048116 (released on June 22, 2002) and the like, two or more layers of light diffusive orientations produced by coextrusion; Polyester film.

(5) A light-diffusion sheet obtained by melt mixing a bead in a transparent resin introduced in Japanese Unexamined Patent Application Publication No. Hei 6-123802 (published 14.04.05.06) and extrusion molding.

The light diffusing sheets of (1) and (2) are surface-light diffusing sheets which obtain light diffusing effects by forming irregularities on the sheet surface or coating the light diffusing layer.

However, in the case of the light diffusion sheet which obtains the light diffusion effect by the surface treatment as in (1) and (2) above, there is a high risk of damage to the surface of the sheet during handling. Particularly, in case of (2), it is currently widely used in small liquid crystal displays such as notebook computers, and this type of light diffusion sheet has a problem in that it is difficult to form a laminated structure required for high performance and multifunction of liquid crystal display devices. There is a problem that the light diffusion layer coated on the surface is easily peeled off due to the difference in thermal expansion properties with the substrate.

On the other hand, the light diffusing sheets of (3) to (5) have the advantage of being able to obtain a sheet to which light diffusivity is given at the same time as sheet forming, and to obtain a high light diffusing degree.

However, the light diffusing sheet of (3) has a problem in that light transmittance, brightness, and mechanical properties of the sheet are lowered due to the inorganic particles added to impart light diffusivity, and wear of the processing equipment when used for a long time.

Since the light-diffusion sheet of (4) uses polyester which is a crystalline resin, in order to obtain desired light-diffusion and total light transmittance, two or more layers of polyester unstretched sheet are first produced, and then the longitudinal and transverse directions are performed at a constant temperature. As a result, the heat treatment process must be performed after the stretching process by a specific draw ratio. If the stretching process is not performed, the crystals between the polymer chains generated during the sheet cooling process cause serious transparency and optical degradation. Therefore, in order to secure transparency and optical properties, a drawing process of the sheet is necessarily required, and thus there is a problem in that the manufacturing process is complicated and productivity is lowered.

The light diffusing sheet of (5) is the most commonly used form at present, and the light diffusing plate used for the liquid crystal display device of 40 inches or less is mainly polyalkyl (meth) acrylate, alkyl (meth) acrylate-styrene air. It is made of coalescence, polystyrene resin.

However, as the size of liquid crystal displays increases rapidly, warpage problems due to heat and moisture absorption occur, thereby causing problems such as luminance unevenness due to collision with the liquid crystal plate. Accordingly, a large liquid crystal display device of 40 inches or larger mainly uses a light diffusion plate made of resin such as polycarbonate having better heat resistance than the resins listed above.

The resins such as polycarbonates are more expensive than polyalkyl (meth) acrylates, alkyl (meth) acrylate-styrene copolymers, and polystyrene resins, and thus are less economical and have a wider viewing angle characteristic that has been recently developed. There is a limit that the luminance and luminance uniformity are inferior to the liquid crystal panel.

Therefore, there is an urgent need to develop a light diffusion plate having excellent heat resistance and economy, and excellent luminance and uniformity, which can be applied to a liquid crystal panel having a wider viewing angle characteristic.

In order to solve the problems of the prior art as described above, the present invention is excellent in light transmittance and light diffusivity and at the same time high brightness uniformity, the viewing angle characteristic is improved, and the heat resistance is improved multi-layer structure light diffusion plate and including the same It is an object to provide a liquid crystal display device.

The above and other objects of the present invention can be achieved by the present invention described below.

In order to achieve the above object, the present invention is a light diffusion plate of a multi-layer structure consisting of an amorphous transparent thermoplastic resin, consisting of a light diffusion intermediate layer and the first and second light diffusion surface layer located on both sides of the intermediate layer,

Transparent fine particles are dispersed in at least one of the intermediate layer, the first and second surface layers, the glass transition temperature of the first and second surface layers is 10 ° C. or more higher than the intermediate glass transition temperature, and the thickness of the first and second surface layers A multi-layered light diffuser plate having an improved heat resistance having a sum of 1/30 or more of the total thickness of the light diffuser plate is provided.

In addition, the present invention provides a liquid crystal display device including the light diffusion plate.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention, while studying the multi-layer light diffusion plate, in the case of adjusting the glass transition temperature and thickness of the intermediate layer and the surface layer of the light diffusion plate to a constant value, the heat resistance, light transmittance, light diffusivity, brightness and luminance uniformity It was confirmed that the performance and the like were improved, and based on this, the present invention was completed.

The multi-layered light diffuser plate having improved heat resistance of the present invention is a multi-layered light diffuser plate made of an amorphous transparent thermoplastic resin, and includes a light diffusion intermediate layer and first and second light diffusion surface layers positioned on both sides of the intermediate layer. Lose,

Transparent fine particles are dispersed in at least one of the intermediate layer, the first and second surface layers, the glass transition temperature of the first and second surface layers is 10 ° C. or more higher than the intermediate glass transition temperature, and the thickness of the first and second surface layers The sum is 1/30 or more of the total thickness of the light diffusion plate.

In addition, the multi-layered light diffusion plate having improved heat resistance of the present invention is characterized by being manufactured by co-extrusion.

The intermediate layer is an alkyl (meth) acrylate polymer, an alkyl (meth) acrylate-styrene copolymer, a styrene polymer polymerized only with a styrene monomer, a styrene-acrylonitrile copolymer, a styrene-acrylonitrile-phenylmaleimide ( phenyl maleimide copolymer, styrene-maleic anhydride copolymer, styrene-phenylmaleimide copolymer, styrene-methacrylic acid, alkyl (meth) acrylate-styrene-methacrylic acid copolymer, polycarbonate, cyclo It may comprise one or more selected from the group consisting of -olefin copolymers, polysulfones, polyethersulfones, polyarylate resins, and the like.

As the styrene monomer, styrene, α-methyl styrene, ρ-bromo styrene, ρ-methyl styrene, or ρ-chloro styrene may be used.

The resin used in the intermediate layer may be used in an amount of 80 to 100% by weight, preferably 90 to 99.5% by weight, based on the total content of the intermediate layer.

The thickness of the intermediate layer is preferably 0.95 to 3.0 mm, more preferably 1.5 to 2.5 mm. If the thickness is less than 0.95 mm, the mechanical properties of the light diffusion plate is lowered, and if it exceeds 3.0 mm, the light diffusion plate becomes heavy and it is difficult to thin.

The surface layer may include one or more selected from the group consisting of resins used in the light diffusion intermediate layer.

The resin used for the surface layer may be used in an amount of 80 to 100% by weight, preferably 90 to 99.5% by weight, based on the total content of the light diffusion surface layer.

The glass transition temperature used for the surface layer is preferably at least 10 ℃ higher than the glass transition temperature of the resin used in the intermediate layer. If the glass transition temperature is not higher than 10 DEG C, the luminance uniformity of the light diffusion plate is lowered, and the heat resistance is significantly lowered. In order to improve heat resistance, when a resin made of polycarbonate or the like is used for the intermediate layer and the surface layer, it is difficult to apply to a liquid crystal panel having high economical efficiency and low luminance and brightness uniformity, and having a wider viewing angle characteristic.

The thickness of the first and second surface layers is preferably 50 to 500 μm, and more preferably 100 to 300 μm. If the thickness is less than 50 μm, light diffusion and heat resistance are insufficient, and if the content of the transparent fine particles is increased to compensate for the insufficient light diffusion, the transmittance and luminance decreases. In addition, when the thickness exceeds 500 μm, light diffusion and heat resistance are improved, but light transmittance and luminance are decreased, and the light diffusion plate becomes heavy and it is difficult to thin.

The sum of the thicknesses of the first and second surface layers is preferably 1/30 or more of the total thickness of the light diffusion plate, and when smaller than 1/30, heat resistance, luminance, luminance uniformity, and the like are deteriorated.

As the transparent fine particles, inorganic fine particles such as glass fine particles, organic fine particles or a mixture thereof can be used, and preferably organic fine particles can be used.

It is preferable to use fine particles made of at least one resin selected from the group consisting of polymethyl (meth) acrylate, methyl (meth) acrylate-styrene copolymer, polystyrene, silicone resin and the like as the organic fine particles.

It is preferable that resin used as said organic microparticles | fine-particles is partially bridge | crosslinked. Particles crosslinked with the resin are relatively unevenly modified in shape and shape even during the manufacturing process of the light diffusion plate.

The average particle diameter of the transparent fine particles is preferably 0.5 to 50 μm, more preferably 1.5 to 20 μm. If the average particle diameter is less than 0.5 μm, sufficient light diffusivity cannot be obtained, resulting in poor overall surface luminescence, and a problem of visible light sources occurs. Similarly, if more than 50 μm, sufficient light diffusivity cannot be obtained. In the case of using a large amount to increase the light diffusivity, there is a problem that the light transmittance and luminance decreases.

The transparent fine particles should be dispersed in at least one of the intermediate layer, the first and the second surface layer, and each of the dispersed layers may be included in an amount of 20% by weight or less, preferably 0.5 to 10 It is included by weight.

The content of the transparent fine particles and the position at which they are dispersed may be properly adjusted by the required optical properties.

The light diffusion plate may be manufactured by coextrusion of the light diffusion intermediate layer and the light diffusion surface layer.

There is no restriction | limiting in particular in the apparatus used for the said coextrusion process, Any apparatus which can coextrude a polymer resin sheet or a film can be used including well-known coextrusion apparatuses, such as a double or triple coextruder.

The co-extrusion conditions are not particularly limited, and may be appropriately adjusted according to the type of resin used, the thickness of each layer, and the like, based on known co-extrusion conditions.

The light diffusing plate is a UV stabilizer, fluorescent brightener, impact modifier, antistatic agent, heat stabilizer, flame retardant, lubricant, dye, etc. as necessary within the range that can achieve the object and effect of the present invention in addition to the components described above. It may further include an additive.

Looking at the manufacturing process of the light diffusion plate, after mixing a certain amount of alkyl (meth) acrylate polymer, alkyl (meth) acrylate-styrene copolymer or styrene polymer resin, and the transparent fine particles with a Henschel mixer, using an extruder This can be prepared in a resin composition for light diffusion intermediate layer in the form of pellets.

In addition, after mixing a predetermined amount of polycarbonate resin and the like and the transparent fine particles with a glass transition temperature 10 ℃ or more than the resin used in the intermediate layer in a Henschel mixer, using an extruder to form a resin composition for light-diffusion surface layer of the pellet form It can manufacture.

The multi-layered light diffuser plate having excellent heat resistance of the three-layer structure is finally formed by melt co-extrusion of the resin composition pellet for light diffusion intermediate layer and the light diffusion surface layer resin composition pellet prepared using a T-die. It can manufacture.

At this time, if necessary, a suitable additive may be further added at the time of preparing the resin composition of each layer or at the time of co-extrusion, and the thickness of each layer may be adjusted by changing the discharge amount by adjusting the screw rotation speed of the extruder.

The liquid crystal display device of the present invention is characterized by including the light diffusion plate in the direct type backlight unit.

One embodiment of the liquid crystal display device 100 is schematically illustrated as a cross-sectional view in FIG. 3.

The liquid crystal display apparatus 100 may display a liquid crystal panel 110 displaying an image according to a driving signal and a data signal applied from the outside, and a backlight unit 120 disposed at a rear side of the liquid crystal panel to illuminate the liquid crystal panel 110. ).

The precise structural characteristics of the liquid crystal panel 110 are not important, and any liquid crystal panel commonly used in the liquid crystal display device may be applied to the liquid crystal display device of the present invention.

The backlight unit 120 is located at the rear of the liquid crystal panel 110 and provides light, for example, white light, to the liquid crystal panel 110. The backlight unit 120 may include a plurality of light sources 150 for providing light for illuminating the liquid crystal panel 110, a reflection sheet 180, and a bottom chassis in which the light source and the reflection sheet 180 are accommodated; 190, a light diffusion plate 140 and an optical sheet 130 positioned on the light source.

The light source 150 may be a linear light source such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) that generates light having a predetermined wavelength, for example, white light. Can be. However, the linear light source is not only used as the light source 150, and a point light source such as a light emitting diode (LED) may be used.

There is no limitation to the light emitting diode, and one white light emitting diode may be used, or a combination of three light emitting diodes of red (R), green (G), and blue (B) may be used, and the number of the light emitting diodes is to be illuminated. It may be appropriately selected according to the size of the liquid crystal panel 110.

The reflective sheet 180 is positioned below the light source 150, and reflects light emitted from the light source 150 in the direction in which the liquid crystal panel 110 is positioned to improve light utilization efficiency. The reflective sheet 180 may be manufactured by coating silver on the sheet made of stainless steel (SUS), brass, aluminum, PET (PolyEthylene Terephthalate), and coating titanium to prevent deformation due to endothermic long time. have. In addition, the reflective sheet 180 made of synthetic resin such as PET may be manufactured by dispersing bubbles for scattering light.

The light source 150 and the reflective sheet 180 are accommodated in the lower chassis 190, and the light generated from the light source 150 is incident on the light diffusion plate 140 positioned above the light source 150.

An optical sheet 130 is positioned on the light diffusion plate 140, and the optical sheet includes a diffusion sheet 130a, a prism sheet 130b, and a protective sheet 130c. The light passing through the light diffusion plate 140 is incident on the diffusion sheet 130a, and the diffusion sheet scatters the incident light to uniform the luminance and widen the viewing angle of the entire visible surface of the liquid crystal panel 110.

A prism sheet 130b is disposed on the diffusion sheet 130a to improve light efficiency and brightness, and the prism sheet serves to compensate for the reduced luminance in the diffusion sheet. Since the prism sheet 130b refracts the light emitted from the diffusion sheet 130a and concentrates the light incident at a low angle toward the front side, the prism sheet 130b increases the luminance in the effective viewing angle range.

A protective sheet 130c is disposed above the prism sheet 130b, and the protective sheet prevents scratches of the prism sheet and re-expands the viewing angle reduced by the prism sheet within a predetermined range.

In the liquid crystal display device, since the light generated from the light source 150 passes through the multi-layered light diffusion plate 140 according to the present invention, the liquid crystal display device has a higher luminance than the conventional light diffusion plate in the direction of the liquid crystal panel located in front of the liquid crystal display device. While having, it is possible to enter at a wide angle.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the appended claims.

[ Example ]

Example  1 to 5 and Comparative example  1 to 3

After the ingredients and contents of the resin and transparent fine particles used in the light-diffusion intermediate layer and mixed in the Henschel mixer as shown in Table 1 below, the resin composition for the light-diffusion intermediate layer using an extruder (Leistritz, 27Φ L / D = 48) Was prepared in pellet form.

In addition, the components and contents of the resin and the transparent fine particles used in the light diffusion surface layer as described in Table 1 were added to the Henschel mixer, mixed, and then used for the light diffusion surface layer using an extruder (Leistritz, 27Φ L / D = 48). The resin composition was prepared in pellet form.

By using the co-extruder equipped with a T-die, the resin composition for the light diffusion intermediate layer and the surface layer prepared by melting and co-extrusion by adjusting the discharge amount, to produce a light diffusion plate having a multi-layer structure having a layer thickness shown in Table 1 It was.

division Light Diffusion Interlayer Light Diffusion Surface Layer Suzy Content (% by weight) Transparent fine particles (wt%) Thickness (mm) Glass transition temperature (℃) Suzy Content (% by weight) Transparent fine particles (wt%) Thickness (mm) First layer / Second layer Glass transition temperature (℃) Example 1 PS 99.8 A: 0.2 1.7 105 PC 96.5 A: 1.2 B: 2.3 0.15 / 0.15 145 Example 2 MS200 99.8 A: 0.2 1.7 103 PC 96.5 A: 1.2 B: 2.3 0.15 / 0.15 145 Example 3 MS600 99.8 A: 0.2 1.7 105 PC 96.5 A: 1.2 B: 2.3 0.15 / 0.15 145 Example 4 PMMA 99.7 A: 0.3 1.7 107 PC 96.0 A: 4.0 B: 0.0 0.15 / 0.15 145 Example 5 MS200 99.7 A: 0.3 1.3 103 PC 96.0 A: 1.5 B: 2.5 0.1 / 0.1 145 Comparative Example 1 MS200 99.4 A: 0.3 B: 0.3 1.9 103 MS600 100 - 0.05 / 0.05 105 Comparative Example 2 PC 99.4 A: 0.3 B: 0.3 1.9 145 PC 100 - 0.05 / 0.05 145 Comparative Example 3 MS200 99.4 A: 0.3 B: 0.3 1.94 103 PC 100 - 0.03 / 0.03 145

* PMMA: Polymethylmethacrylate (LG MMA, EG920)

PS: Polystyrene (LG Chem, 25SP IDI)

* MS200: Methyl methacrylate-styrene copolymer (New Nippon Steel Chemical)

* MS600: Methyl methacrylate-styrene copolymer (New Nippon Steel Chemical)

* PC: Polycarbonate (LG DOW, Caliber 300-22)

* A: silicon organic particles (GE Toshiba, Tospearl 120, average particle diameter: 2 ㎛)

* B: acrylic organic particles (Nippon Shokubai, MA1002, average particle diameter: 2.5 ㎛)

[ Test Example ]

The properties of the multilayered light diffuser plates prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were measured by the following methods, and the results are shown in Tables 1 and 2 below.

* Total light transmittance and light diffusivity (haze)-It measured using the haze transmittance meter (trade name: HR-100, Murakami Color Research Laboratory) according to JIS K 7105.

Average luminance-The sheet was cut and placed on a 32-inch direct type backlight unit at a width of 720 mm and a length of 420 mm, and the luminance of 17 points was measured with a BM-7 manufactured by TOPCON, and the average value was taken as the average luminance. The light diffusion plate for evaluation is briefly shown in FIG. 3.

Luminance Uniformity-Among the measured luminances, luminance uniformity was evaluated from the value obtained by dividing the maximum luminance by the minimum luminance. When the luminance uniformity is 1.00, the luminance uniformity is the best, and as the value becomes larger, the luminance uniformity becomes worse.

* Heat resistance-In a constant temperature and humidity chamber with a relative humidity of 50%, a multi-layered light diffuser plate made of 5 cm x 30 cm with varying temperatures from 80 ° C to 110 ° C was placed over two jigs for 4 hours. The bending length of the center part of the test piece was determined and measured as ○ (good) when the length was 0 to 2 mm, Δ (normal) when 2 to 4 mm, and × (bad) when 4 mm or more.

division Total light transmittance (%) Light Diffusion (%) Average luminance (cd / m ² ) Luminance uniformity Example 1 65.7 84.5 5425 1.37 Example 2 66.2 84.5 5464 1.38 Example 3 66.9 84.5 5459 1.38 Example 4 70.1 84.4 5470 1.40 Example 5 68.5 84.4 5492 1.39 Comparative Example 1 70.8 84.5 5450 1.45 Comparative Example 2 65.2 84.6 5412 1.45 Comparative Example 3 67.2 84.6 5448 1.45

As shown in Table 2, the multilayered light diffusing plates (Examples 1 to 5) of the present invention have a total light transmittance equal to or higher than that of the multilayered light diffusing plates (Comparative Examples 1 to 3), which are currently used commercially. , Light diffusivity and average luminance were shown, and in particular, the luminance uniformity was remarkably excellent.

More specifically, when the glass transition temperature of the resin used as the surface layer of the light diffusion plate is not more than 10 ℃ higher than the case of the intermediate layer (Comparative Example 1), it was confirmed that the luminance uniformity is lowered, both the surface layer and the intermediate layer using polycarbonate Case (Comparative Example 2) It was confirmed that luminance, luminance uniformity and total light transmittance were lower than those of the present invention.

In addition, the glass transition temperature is within the scope of the present invention, but when the sum of the thicknesses of both surface layers is less than 1/30 of the total thickness of the light diffusion plate (Comparative Example 3), it was confirmed that the luminance uniformity was lower than that of the present invention. .

division 80 ℃ 90 ℃ 100 ℃ 110 ℃ Example 1 ○ ○ ○ △ Example 2 ○ ○ ○ ○ Example 3 ○ ○ ○ ○ Example 4 ○ ○ ○ ○ Example 5 ○ ○ ○ ○ Comparative Example 1 △ × × × Comparative Example 2 ○ ○ ○ ○ Comparative Example 3 ○ △ × ×

As shown in Table 3 above, the multilayer structure light diffusion plates (Examples 1 to 5) of the present invention have a glass transition temperature of the resin used as the surface layer of the light diffusion plate is not greater than 10 ° C or more than that of the intermediate layer ( Compared with Comparative Example 1) and the sum of the thicknesses of both surface layers less than 1/30 of the total thickness of the light diffusion plate (Comparative Example 3), it was confirmed that the heat resistance characteristics were remarkably excellent.

In addition, when the surface layer and the intermediate layer were both polycarbonate (Comparative Example 2), it was confirmed that the heat resistance is excellent, but this is expensive and inferior in economic efficiency, as shown in Table 2, luminance, luminance uniformity and total light transmittance are It could be confirmed that the fall compared to.

As described above, according to the present invention, the optical diffusing plate has excellent economical efficiency, light transmittance and light diffusivity, and has high luminance, and has high luminance uniformity, thereby improving viewing angle characteristics and improving heat resistance. There is an effect of providing a plate and a liquid crystal display device including the same.

Claims (16)

   A light diffusion plate having a multilayer structure made of an amorphous transparent thermoplastic resin, A light diffusing intermediate layer and first and second light diffusing surface layers positioned on both sides of the intermediate layer, Transparent fine particles are dispersed in at least one of the intermediate layer, the first and second surface layers, the glass transition temperature of the first and second surface layers is 10 ° C. or more higher than the intermediate glass transition temperature, and the thickness of the first and second surface layers The sum is at least 1 / 30th of the thickness of the intermediate layer Multi-layer light diffusion plate with improved heat resistance. The method of claim 1, The intermediate layer is a polyalkyl (meth) acrylate, an alkyl (meth) acrylate-styrene copolymer, a styrene polymer polymerized only with a styrene monomer, a styrene-acrylonitrile copolymer, a styrene-acrylonitrile-phenylmaleimide Copolymer, styrene-maleic anhydride copolymer, styrene-phenylmaleimide copolymer, styrene-methacrylic acid, alkyl (meth) acrylate-styrene-methacrylic acid copolymer, polycarbonate, cyclo-olefin copolymer, polysulfone And at least one selected from the group consisting of polyether sulfones and polyarylate resins. Multi-layer light diffusion plate with improved heat resistance. The method of claim 2, The styrene monomer is styrene, α-methyl styrene, ρ-bromo styrene, ρ-methyl styrene, or ρ-chloro styrene, characterized in that Multi-layer light diffusion plate with improved heat resistance. The method of claim 2, The resin, characterized in that it comprises 80 to 100% by weight Multi-layer light diffusion plate with improved heat resistance. The method of claim 1, The intermediate layer is characterized in that the thickness is 0.95 to 3.0 mm Multi-layer light diffusion plate with improved heat resistance. The method of claim 1, The said surface layer contains 1 or more types chosen from the group which consists of resin used for the said intermediate | middle layer, It is characterized by the above-mentioned. Multi-layer light diffusion plate with improved heat resistance. The method of claim 6, The resin, characterized in that contained in 80 to 100% by weight Multi-layer light diffusion plate with improved heat resistance. The method of claim 1, The first and the second surface layer is characterized in that the thickness of 50 to 500 ㎛ each Light diffusion plate with improved heat resistance. The method of claim 1, The transparent fine particles are inorganic fine particles, organic fine particles or a mixture thereof. Multi-layer light diffusion plate with improved heat resistance. The method of claim 9, The organic fine particles are produced by at least one member selected from the group consisting of polymethyl (meth) acrylate, methyl (meth) acrylate-styrene copolymer, polystyrene and silicone resin. Multi-layer light diffusion plate with improved heat resistance. The method of claim 9, The organic fine particles are partially crosslinked. Multi-layer light diffusion plate with improved heat resistance. The method of claim 1, The transparent fine particles have an average particle diameter of 0.5 to 50 µm, characterized in that Multi-layer light diffusion plate with improved heat resistance. The method of claim 1, The transparent fine particles, characterized in that contained in 20% by weight or less in each of the layers to be dispersed Multi-layer light diffusion plate with improved heat resistance. The method of claim 1, The multilayer structure light diffusion plate is characterized in that which is produced by coextrusion Multi-layer light diffusion plate with improved heat resistance.        The method of claim 1, The light diffusing plate further comprises at least one member selected from the group consisting of UV stabilizers, fluorescent brighteners, impact modifiers, antistatic agents, heat stabilizers, flame retardants, lubricants and dyes. Multi-layer light diffusion plate with improved heat resistance. A liquid crystal display device comprising the multi-layer light diffusing plate of claim 1 in a direct backlight unit.

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