KR20100083280A - Multi-structured photo-diffusion panel and liquid display device comprising the same - Google Patents

Abstract

PURPOSE: A multi-layered structured light diffusion plate with a superior optical transmittance rate and a liquid crystal display apparatus for including the same are provided to prevent the deformation of the light diffusion plate at high temperature and high humidity. CONSTITUTION: A light diffusion intermediate layer(2) comprises a heat resistance polystyrene resin. The surface layer comprises the antistatic agent in the upper side of the intermediate layer and lower-part, and the polycarbonate and polystyrene blend resin.

Description

Multi-structured photo-diffusion panel and liquid display device comprising the same

The present invention relates to a blend of polycarbonate and polystyrene blends having a light diffusing intermediate layer of heat resistant PS (styrene-methacrylic acid or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) and comprising an antistatic agent. A multi-layered light diffusion plate having a surface layer and a liquid crystal display device comprising the same, and more particularly, a light diffusion intermediate layer including transparent fine particles in a heat resistant PS resin, and a polycarbonate and polystyrene blend including an anionic antistatic agent. Co-extrusion of the light diffusing plate having the surface layer made of it has excellent light transmittance and light diffusivity, and has high brightness and antistatic agent is included in the surface layer to show the antistatic property without a separate coating process and work in high temperature roll conditions. The internal stress can be minimized to prevent deformation of the diffusion plate at high temperature and high humidity. The present invention relates to a multi-layered light diffuser plate having low luminance unevenness 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 has been 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 in order to make the backlight or the contents of the back visible from the outside and at the same time have a uniform brightness, and at the same time it is required to have a high light transmittance to increase the light efficiency (high brightness, low power consumption). . In addition, in order to secure a wider viewing angle, the overall luminance uniformity is required to be high.

The light diffusion sheets developed so far include, for example, the following: (1) A light diffusion sheet in which inorganic particles are mixed in a transparent resin and molded into a sheet to give light diffusibility (Japanese Patent Laid-Open No. H6-6-). 347617), (2) two or more layers of light diffusive oriented polyester films produced by coextrusion (Japanese Patent Laid-Open Nos. 2001-322218 and 2002-48116) and (3) in transparent resins The light-diffusion sheet obtained by melt-mixing beads and extrusion molding (JP-A-H6-123802).

The light diffusing sheets of (1) to (3) have advantages in that a sheet to which light diffusivity is imparted at the same time as sheet forming can be obtained at once, and a high light diffusivity can be obtained. However, the light diffusing sheet of (1) has the disadvantage of lowering light transmittance, lowering brightness, and significantly lowering mechanical properties of the sheet due to the inorganic particles added to impart light diffusivity. There is also a problem. In the case of (2), since polyester, which is a crystalline resin, is used, in order to obtain a desired light diffusivity and total light transmittance, two or more layers of polyester unstretched sheets are first manufactured, and then a specific draw ratio is specified in the longitudinal and transverse directions at a constant temperature. After the stretching process, the heat treatment process must be performed. 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, there is a disadvantage in that the manufacturing process is complicated and productivity is lowered because the stretching process of the sheet is necessary to ensure transparency and optical characteristics. The light diffusion sheet of (3) is the most commonly used form at present. The light diffusion plate used in the liquid crystal display device of 40 inches or less is mainly polyalkyl (meth) acrylate, alkyl (meth) acrylate-styrene air. It is made of polystyrene and polystyrene resin, and as the size of liquid crystal display grows rapidly, more warpage problems occur due to heat and moisture absorption. This is required. Accordingly, recently, large-sized liquid crystal display devices of 37 inches or more are mainly made of resins such as styrene-methacrylic acid or styrene-alkyl (meth) acrylate-methacrylic acid copolymer, polycarbonate, etc., which have better heat resistance than those listed above. A light diffuser plate is used. Since polycarbonate resins are expensive compared to other resins and are not economical, the light diffusion of heat-resistant PS (styrene-methacrylic acid or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) resin is mainly used for 37-inch large liquid crystal display devices. The plate is being used. Polyalkyl (meth) acrylates, alkyl (meth) acrylate-styrene copolymers, and polystyrene resins are mainly used as the surface layer material of the heat-resistant PS resin light diffusion plate. In order to minimize the internal stress by minimizing internal stress and to minimize deformation under high temperature and high humidity, the surface temperature of the diffusion plate must be maintained above the glass transition temperature (about 120 ℃) made of heat-resistant PS resin after passing through the roll during processing of the diffusion plate. Should be kept at high temperature. In the case of using the above-mentioned polyalkyl (meth) acrylate, alkyl (meth) acrylate-styrene copolymer, or polystyrene resin in a high temperature roll, the resin may adhere to the roll or cause roll contamination, resulting in poor manufacturing of the light diffusion plate. Caused by.

The present invention relates to a blend of polycarbonate and polystyrene blends having a light diffusing intermediate layer of heat resistant PS (styrene-methacrylic acid or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) and comprising an antistatic agent. A multi-layered light diffusion plate having a surface layer and a liquid crystal display device comprising the same, and more particularly, a light diffusion intermediate layer including transparent fine particles in a heat resistant PS resin, and a polycarbonate and polystyrene blend including an anionic antistatic agent. Co-extrusion of the light diffusing plate having the surface layer made of it has excellent light transmittance and light diffusivity, and has high brightness and antistatic agent is included in the surface layer to show the antistatic property without a separate coating process and work in high temperature roll conditions. The internal stress can be minimized to prevent deformation of the diffusion plate at high temperature and high humidity. The present invention relates to a multi-layered light diffuser plate having low luminance unevenness and a liquid crystal display device including the same.

The present invention provides a light-diffusion intermediate layer comprising a heat-resistant PS (styrene-methacrylic acid (MAA) or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) resin and the upper and lower surfaces of the intermediate layer. It provides a light diffusing plate, characterized in that the surface layer comprising an antistatic agent and a polycarbonate and polystyrene blend resin is laminated.

In addition, the present invention provides a liquid crystal display device including the multilayer structure light diffusion plate in a direct type backlight unit.

According to the present invention, a poly-diffusion interlayer of heat-resistant PS (styrene-methacrylic acid (MAA) or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) and comprising an antistatic agent A multi-layered light diffusing plate having a surface layer of a polycarbonate and polystyrene blend, and a liquid crystal display device comprising the same, and more particularly, a light diffusing intermediate layer comprising transparent fine particles in a heat-resistant PS resin, and an anionic system. Co-extrusion of a light diffusion plate having a surface layer consisting of a polycarbonate and a polystyrene blend containing an antistatic agent is excellent in light transmittance and light diffusivity, and has a high brightness and at the same time the antistatic agent is included in the surface layer is charged without a separate coating process It exhibits prevention characteristics and can be operated in hot roll conditions to minimize internal stress. By preventing deformation of the diffusion plate at high temperature and high humidity, a multilayer structure light diffusion plate having less luminance unevenness and a liquid crystal display device including the same can be obtained.

In the light diffusion plate of the present invention, the light diffusion intermediate layer is a styrene-based monomer (styrene, α-methyl styrene, ρ-bromo styrene, ρ-methyl styrene ( Methacrylic acid (MAA) or alkyl (meth) acrylate-meta to improve the heat resistance of styrene-based polymers polymerized using ρ-methyl styrene or ρ-chloro styrene Transparent microparticles | fine-particles are contained in resin using the heat-resistant PS (styrene-methacrylic acid or styrene-alkyl (meth) acrylate-methacrylic acid copolymer which copolymerized acrylic acid. Particulates or mixtures thereof are used, preferably organic fine particles, which are selected from the group consisting of polymethyl (meth) acrylate, methyl (meth) acrylate-styrene copolymer and silicone resin. It is preferable to use microparticles prepared from one or more selected resins, and it is preferable to use partially crosslinked organic microparticles because the shape of the particles can be maintained without changing the shape of the microparticles during the resin processing. Do.

Moreover, it is preferable that it is 0.5-50 micrometers, and, as for the average particle diameter of transparent fine particles, it is more preferable that it is 1.5-20 micrometers. If the average particle diameter of the transparent fine particles is less than 0.5 μm, sufficient light diffusivity is not obtained, resulting in poor overall surface luminescence, and a problem in that the light source is visible occurs. In order to increase the light diffusivity, when a large amount is added, the transmittance and luminance decrease.

Further, in the light diffusion plate of the present invention, the light diffusion intermediate layer is 80 to 100 parts by weight of a resin using heat resistant PS (styrene-methacrylic acid or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) and transparent 0 to 20 parts by weight of fine particles, and more preferably 90 to 99.5 parts by weight of the resins listed above and 0.5 to 10 parts by weight of transparent fine particles.

Further, in the light diffusion plate of the present invention, the light diffusion surface layer contains an antistatic agent and transparent fine particles in the polycarbonate-polystyrene blend resin composition.

As the transparent fine particles included in the light diffusion surface layer, inorganic fine particles such as glass fine particles, organic fine particles or a mixture thereof are used, and organic fine particles are preferably used. As the organic fine particles, it is preferable to use fine particles prepared from at least one resin selected from the group consisting of polymethyl (meth) acrylate, methyl (meth) acrylate-styrene copolymer, polystyrene and silicone resin. In addition, it is preferable to use partially crosslinked organic fine particles because the shape of the particles can be maintained without deforming even during the resin processing.

Moreover, it is preferable that it is 0.5-50 micrometers, and, as for the average particle diameter of transparent fine particles, it is more preferable that it is 1.5-20 micrometers. If the average particle diameter of the transparent fine particles is less than 0.5 μm, sufficient light diffusivity is not obtained, resulting in poor overall surface luminescence, and a problem in that the light source is visible occurs. In order to increase the light diffusivity, when a large amount is added, the transmittance and luminance decrease.

Alkyl sulfonate, Alkylbenzene sulfonate, Alkyl phosphate, Alkali metal salts and the like may be used as the anionic antistatic agent used for the light diffusion surface layer, and more preferably, an anionic antistatic agent based on Alkylsulphonate sodium salt is preferable.

In addition, in the light diffusion plate of the present invention, preferably, the light diffusion surface layer contains 30 to 70 parts by weight of polycarbonate, 30 to 70 parts by weight of polystyrene, 0.5 to 5 parts by weight of an antistatic agent and 0 to 20 parts by weight of transparent fine particles. . More preferably, it contains 40-60 weight part of polycarbonates, 40-60 weight part of polystyrenes, 1-2 weight part of antistatic agents, and 0.5-20 weight part of transparent fine particles. If the polycarbonate content of the light diffusion surface layer is less than 30 parts by weight and more than 70 parts by weight of polystyrene, sufficient heat resistance for working on a high temperature roll may not be obtained, so that the resin may stick to the roll or roll contamination may occur. Anionic antistatic agents and polystyrene Due to the lowering of the compatibility of the surface may cause defects such as patterns, stains, etc. is not preferable. If the polycarbonate content is more than 70 parts by weight and the polystyrene content is less than 30 parts by weight, the adhesive force with the heat-resistant PS, which is the intermediate layer of the light diffusion plate, may be degraded, which may cause the phenomenon that the intermediate layer and the surface layer are peeled off. In addition, if the content of the antistatic agent used in the light diffusion surface layer is less than 0.5 parts by weight does not exhibit a sufficient antistatic performance required, if more than 5 parts by weight may cause a defect in the roll contamination and stains on the surface may occur Can not do it. In addition, the content of the transparent fine particles of the light diffusing intermediate layer and the light diffusing surface layer is preferably adjusted appropriately according to the required optical properties.

The light diffusing plate of the present invention, UV stabilizer, fluorescent brightener, impact modifier, heat as necessary within the range that can achieve the object and effect of the present invention in addition to the above components in the light diffusion intermediate layer or light diffusion surface layer Additives such as stabilizers, flame retardants, lubricants, dyes and the like may be further selected as appropriate.

In the light diffusion plate of the present invention, the thickness of the light diffusion intermediate layer is preferably 0.95 to 3.0 mm, more preferably 1.5 to 2.5 mm. If the thickness of the light diffusion intermediate layer is less than 0.95 mm, the mechanical properties of the light diffusion plate are weak and not suitable. If the thickness of the light diffusion intermediate layer is more than 3.0 mm, the light diffusion plate becomes heavy and the thickness becomes difficult, which is not practically desirable.

The multi-layered light diffusing plate of the present invention is produced by coextrusion of the light diffusing intermediate layer and the light diffusing surface layer as described above. There is no particular restriction on the apparatus used in the coextrusion process and coextrusion conditions, and any apparatus capable of coextrusion of a polymer resin sheet or film, including a known coextrusion apparatus such as a double or triple coextruder, can be used. Do. Co-extrusion conditions can also be suitably adjusted according to the kind of resin used, the thickness of each layer, etc. based on well-known co-extrusion conditions. According to one embodiment for producing a multilayer structure light diffusing plate of the present invention, 80 to 100 parts by weight of heat-resistant PS (styrene-methacrylic acid) or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) resin and After mixing 0 to 20 parts by weight of the transparent fine particles as described above in a Henschel mixer, it is prepared as a resin composition for light diffusing intermediate layer in the form of pellets using an extruder. Further, 30 to 70 parts by weight of polycarbonate, 30 to 70 parts by weight of polystyrene, 0.5 to 5 parts by weight of the antistatic agent as described above, and 0 to 20 parts by weight of the transparent fine particles as described above were mixed with a Henschel mixer, followed by using an extruder. This was prepared as a resin composition for light diffusion surface layer in the form of pellets. The multi-layered light diffusion plate having a three-layer structure is produced by melt co-extrusion of the resin composition pellet for light-diffusion intermediate layer and the light-diffusion surface layer resin composition pellet prepared above using a co-extruder equipped with a T-die. At this time, if necessary, an appropriate 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.

On the other hand, according to another aspect of the present invention, there is provided a liquid crystal display device comprising a multilayer structure light diffusion plate of the present invention.

Hereinafter, a liquid crystal display device including the multilayered light diffusing plate of the present invention in a direct type backlight unit will be described in detail with reference to the accompanying drawings.

4 is a cross-sectional view schematically showing an embodiment of the liquid crystal display device 100 according to the present invention.

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. It includes.

In understanding and practicing the present invention, the precise structural characteristics of the liquid crystal panel 110 are not important, and any structure of liquid crystal panel commonly used in the liquid crystal display device may be applied to the liquid crystal display device according to 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 includes a plurality of light sources 150 that provide light for illuminating the liquid crystal panel 110, a reflective sheet 180, a bottom chassis 190 in which the light sources and the reflective sheet are accommodated, and The light diffusing plate 140 and the optical sheet 130 according to the present invention are disposed above the light source.

The light source 150 uses a linear light source such as a Cold Cathode Fluorescent Lamp (CCFL) or an External Electrode Flourscent Lanm (EEFL) that generates light having a predetermined wavelength, for example, white light. do. 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. In this case, the number of light emitting diodes used as the light source 150 may be appropriately selected according to the size of the liquid crystal panel 110 to be illuminated. In addition, the light emitting diode used as the light source 150 is not limited, and one white light emitting diode may be used or a combination of three light emitting diodes generating colors of red (R), green (G), and blue (B) may be used. It is also possible to use.

The reflective sheet 180 is positioned below the light source 150, and reflects the 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 (Ag) on a sheet made of SUS, brass, aluminum, PET, and the like, and titanium coating to prevent deformation due to endotherm for a long time even if heat is generated minutely. In addition, the reflective sheet 180 may be manufactured by dispersing bubbles for scattering light on a sheet made of synthetic resin such as PET.

The light source 150 and the reflective sheet 180 described above are accommodated in the lower chassis 190.

The light generated from the light source 150 is incident on the multi-layered light diffuser plate 140 according to the present invention disposed on the light source 150.

An optical sheet 130 is disposed 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 130a scatters the incident light to uniform the luminance and widen the viewing angle of the entire visible surface of the liquid crystal panel. . A prism sheet 130b is disposed on the diffusion sheet 130a to improve light efficiency and brightness, and the prism sheet 130b compensates for the reduced luminance in the diffusion sheet 130a. 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 scratching of the prism sheet 130b, and measures the viewing angle reduced by the prism sheet 130b within a predetermined range. Function to enlarge.

In the liquid crystal display device of the present invention, since the light generated from the light source 150 passes through the multi-layered light diffusing plate 140 according to the present invention, the luminance is higher than that of the conventional light diffusing plate in the direction of the liquid crystal panel located on the front surface thereof. It is possible to enter at a wide angle with.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

[Examples 1-5 and Comparative Examples 1-4]

Heat diffusion PS (styrene-methacrylic acid copolymer) resin made by PS Japan was used as the light diffusion intermediate layer, and 0.3 parts by weight of silicon organic particles (Momentive Performance Materials, Tospearl 120, average particle diameter: 2 μm) was added as transparent fine particles. The mixture was added to a Henschel mixer and mixed, and then a resin composition for light-diffusion intermediate layers was prepared in pellet form using an extruder (Leistritz, 27Φ, L / D = 48).

In addition, the light diffusion surface layer was added to the resin and the transparent fine particles and the antistatic agent in the Henschel mixer in a ratio as shown in Table 1 below, mixed, and then light diffused using an extruder (Leistritz, 27Φ, L / D = 48) The resin composition for surface layers was prepared in pellet form. (However, Comparative Examples 3 and 4 used a light diffusing surface layer material that is currently widely used. Comparative Example 3 is a resin of a copolymer of 20% methacrylate and 80% styrene in the methacrylate-styrene copolymer. The light-diffusion surface layer prepared in Comparative Example 4 prepared a light-diffusing surface layer material made of a resin of a copolymer of 60% methacrylate and 20% styrene in the methacrylate-styrene copolymer.)

The multi-layered light diffusion plate was manufactured by melt co-extrusion of the resin composition pellets for the light diffusion intermediate layer and the surface layer prepared above using a co-extruder equipped with a T-die. In order to compare the optical properties and warpage according to the surface layer and the processing conditions, the total thickness of the light diffusion plate was 1.5mm and the thickness of the surface layer was 50㎛.

The total light transmittance, the light diffusivity, the average brightness, the antistatic property (surface resistance) and the surface layer peeling of the multi-layer light diffusing plates of the Examples and Comparative Examples were measured and shown in Table 2 below. In addition, after the roll contamination and high temperature and high humidity according to the roll temperature conditions of each Example and Comparative Example was measured by the following method and shown in Table 3.

Property measurement method

(1) total light transmittance

According to JIS K 7105, it measured using the haze transmittance meter (brand name: HR-100, Murakami Color Research Laboratory).

(2) average brightness

The sheet was cut and placed on a 32-inch direct backlight unit with a width of 720 mm and a length of 420 mm, and the luminance of 17 points was measured by TOPCON BM-7, and the average value was set as the average luminance. A simplified diagram of the evaluation device is shown in FIG. 3.

 (3) Antistatic property (surface resistance)

Specimens obtained by cutting the prepared light diffusing plate into 10 cm X 10 cm were measured for 24 hours at 23 ° C. and 50% relative humidity, and then measured using a surface resistance meter.

(4) surface pattern

After manufacturing the light diffusion plate, the surface was visually observed to observe the occurrence of abnormal patterns and stains with the naked eye. The evaluation criteria are as follows.

  ○ (good): pattern, no dirt

△ (usually): slightly occurs

× (bad): Patterns, stains very severe

(5) surface layer peeling

The light diffuser plate was cut with a circular saw blade with a specimen cutter, and the degree of peeling from the cut surface was visually observed. The evaluation criteria are as follows.

○ (good): no separation of intermediate and surface layers

△ (usually): slight peeling occurs at the cut surface

× (bad): Complete separation of the intermediate layer and the surface layer

(6) roll pollution

While manufacturing the light diffusion plate using the co-extruder, the degree of staining on the surface of the light diffusion plate due to resin sticking to the roll or contaminating the roll was visually observed.

○ (good): no roll contamination

△ (usually): slight roll contamination occurs, but no light diffuser surface stain

× (bad): Resin sticks to the roll or smears the surface of the light diffusion plate due to roll contamination

(7) luminance blotches

When manufacturing the light diffusion plates of Examples 1 to 5 and Comparative Example 4, a heat-resistant PS light diffusion plate manufactured at a roll temperature of 120 ° C. (However, Comparative Example 2 was 100 ° C.) was mounted on a 37-inch direct type backlight unit, and the optical member And after fully tightening up to the liquid crystal panel and put in a constant temperature and humidity chamber at 50 ℃, 70% relative humidity for 72 hours. After 72 hours was taken out and left for 24 hours at room temperature and humidity conditions, the backlight was turned on to measure the disappearance after the occurrence of luminance unevenness.

PC content (% by weight) PS content (% by weight) Transparent particles
(weight%) Antistatic agent
(weight%) Example 1 70 30 4.0 1.5 Example 2 60 40 4.0 1.5 Example 3 50 50 4.0 1.5 Example 4 40 60 4.0 1.5 Example 5 30 70 4.0 1.5 Comparative Example 1 100 0 4.0 1.5 Comparative Example 2 0 100 4.0 1.5 Comparative Example 3 MS200 5.0 2.0 Comparative Example 4 MS600 5.0 2.0

PC: Polycarbonate (LG DOW Polycarbonate, Caliber DVD 1080)

PS: Polystyrene (LG Chemical, 25SPE)

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

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

Transparent fine particles: Acrylic organic particles (SEKISUI, average particle diameter: 20㎛)

Antistatic Agent: Alkylsulphonic acid sodium salts (SUKANO, TA32)

Total light transmittance (%) Average brightness
(cd / m ² ) Surface resistance
(Ω / m ² ) Surface Surface layer peeling Example 1 54.0 6015 10 ¹¹ ○ △ Example 2 54.2 6028 10 ¹¹ ○ ○ Example 3 53.1 6010 10 ¹¹ ○ ○ Example 4 53.7 5984 10 ¹¹ ○ ○ Example 5 54.5 5953 10 ¹² △ ○ Comparative Example 1 54.5 6037 10 ¹¹ ○ × Comparative Example 2 54.9 5921 10 ¹³ × ○ Comparative Example 3 55.2 5962 10 ¹³ × ○ Comparative Example 4 55.1 5987 10 ¹² △ ○

As described above, when the content of the styrene component in the light diffusion surface layer increases, the antistatic agent is hardly dispersed due to the decrease in compatibility between the anionic antistatic agent and the styrene and methyl methacrylate. It can be confirmed that the pattern occurred (Comparative Examples 2-4).

Roll contamination by temperature Luminance smear
Restore time (hours) 80 ℃ 100 ℃ 120 DEG C Example 1 ○ ○ ○ 29 Example 2 ○ ○ ○ 25 Example 3 ○ ○ ○ 23 Example 4 ○ ○ ○ 21 Example 5 ○ ○ △ 30 Comparative Example 1 ○ ○ ○ - Comparative Example 2 ○ × × - Comparative Example 3 ○ × × - Comparative Example 4 ○ △ × 37

As can be seen in Table 2, the heat-resistant PS multi-layer light diffusing plate of the present invention prepared in Examples 1 to 5, the total light transmittance and average luminance of equal or more than those of Comparative Examples 3 to 4 which are currently used commercially a lot And excellent antistatic properties. In addition, as can be seen in Table 3, the heat-resistant PS multi-layer light diffusing plate of the present invention prepared in Examples 1 to 5 can work without the roll contamination in a high temperature roll to minimize the internal stress in Comparative Example 4 In comparison, the restoration time of the luminance unevenness is significantly shortened.

1 is a schematic cross-sectional view of a heat-resistant PS three-layer structure light diffusion plate according to an embodiment of the present invention.

2 is a view schematically showing a plane of the luminance and luminance uniformity evaluation apparatus.

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

<Description of the symbols for the main parts of the drawings>

1 ...... Multilayer Light Diffusion Plate

2 ...... Heat-resistant PS Light Diffusion Interlayer

3 ...... Polycarbonate-Polystyrene Surface Layer

4 ...... Transparent fine particles

5 ~ 21 ... luminance measuring point

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 diffusion plate, 150: light source, 180: reflection sheet , 190: lower chassis

Claims (11)

Light diffusion intermediate layer comprising heat-resistant PS (styrene-methacrylic acid (MAA) or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) resin, and an antistatic agent on the upper and lower surfaces of the intermediate layer and A light diffusing plate, characterized in that the surface layer comprising a polycarbonate and a polystyrene blend resin is laminated. The light diffusing plate according to claim 1, wherein any one of the light diffusing intermediate layer and the surface layer contains transparent fine particles. The light diffusing plate according to claim 2, wherein the transparent fine particles are inorganic fine particles, organic fine particles or a mixture thereof. The light diffusing method according to claim 3, wherein the organic fine particles are fine particles prepared from at least one resin selected from the group consisting of polymethyl (meth) acrylate, methyl (meth) acrylate-styrene copolymer, and silicone resin. plate. The light diffusing plate according to claim 3, wherein the organic fine particles are partially crosslinked. The light diffusing plate according to claim 2, wherein the average particle diameter of the transparent fine particles is 0.5 to 50 µm. The method of claim 2, wherein the light diffusion intermediate layer is 80 to 100 parts by weight of resin using a heat-resistant PS (styrene-methacrylic acid or styrene-alkyl (meth) acrylate-methacrylic acid copolymer) and 0 to 20 parts by weight of transparent fine particles Light diffusion plate comprising a portion. The light diffusing plate of claim 2, wherein the surface layer comprises 30 to 70 parts by weight of polycarbonate, 30 to 70 parts by weight of polystyrene, 0.5 to 5 parts by weight of an antistatic agent, and 0 to 20 parts by weight of transparent fine particles. The light diffusing plate according to claim 1, further comprising an ultraviolet stabilizer, a fluorescent brightener, an impact modifier, a heat stabilizer, a flame retardant, a lubricant, or a dye as necessary in the light diffusing intermediate layer or the surface layer. The multi-layer light diffusing plate of claim 1, wherein the multi-layered light diffusing plate is manufactured by coextrusion of the intermediate layer and the surface layer. A liquid crystal display device comprising the multi-layer light diffusion plate according to any one of claims 1 to 10 in a direct backlight unit.

Images