JP2010519568A - Diffusion plate - Google Patents

Abstract

An object of the present invention is to provide a light diffusing plate having a single layer structure which exhibits an appropriate luminance and is excellent in concealment.
The present invention relates to a light diffusing plate used in a backlight unit or a lighting device of a liquid crystal display, which includes a polycarbonate resin or a polystyrene resin as a base resin, and has appropriate brightness and high concealability or proper concealment. By exhibiting the properties and the high luminance, the luminance is sufficiently high and the light emission quality can be maintained well while minimizing the application of separate optical films. This light diffusing plate has excellent hiding power against the light source and can be manufactured at a low cost. Due to its high dimensional stability, it does not cause a bending phenomenon even in a high temperature and high humidity environment, and exhibits excellent light characteristics.
[Selection] Figure 1

Description

  The present invention relates to a light diffusion plate used for a backlight unit of a liquid crystal display, an illumination device, and the like.

  As the industrial society develops into an advanced information age, the importance of electronic display devices as a medium for displaying and transmitting various information is increasing day by day. The CRT (Cathode Ray Tube), which has been widely used in the past, is limited in terms of installation space and is difficult to increase in size. Therefore, a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display ( It has been replaced by various flat display devices such as FED) and organic EL. Among these flat display devices, in particular, a liquid crystal display (LCD) is a technology-intensive device in which liquid crystal and semiconductor technology are combined, and its structure and manufacturing technology due to advantages such as thinness, light weight, and low power consumption. Has been researched and developed. At present, LCDs are increasingly oversized due to their large-size technology, not only in the areas that have already been used, such as notebook computers, desktop computer monitors, portable personal communication devices (PDAs and mobile phones), etc. It is attracting attention as a new display device that can replace CRT, which is a synonym for display, such as being applied to HD (High Definition) TV-class large TVs.

  In such a liquid crystal display (LCD) device, since the liquid crystal itself cannot emit light, another light source is installed on the back of the device, and the intensity of the passing light is adjusted through the liquid crystal installed in each pixel. A gradation is realized. More specifically, the liquid crystal display device is a device that adjusts the light transmittance by using the electrical characteristics of the liquid crystal material, and is radiated from a light source lamp on the back of the device and is used to maximize luminous efficiency. Light that has been passed through a functional sheet or film and whose uniformity and direction are controlled is passed through a color filter to achieve red, blue, and green (R, G, B) hues. It is an indirect light emission type display device that realizes an image by controlling the gradation of the image. A light emitting device that provides a light source is an important component that determines image quality such as brightness and uniformity of a liquid crystal display device.

  The light emitting device generally includes a light source, a reflection plate, a light guide plate, a reflective high brightness film, a prism film, a light diffusion film, a light diffusion plate, and the like. Various types of plates or films are used so that the maximum amount of light from the light source can reach the liquid crystal device.

  Among them, the light diffusing plate has a concealing function of blocking the bright lines of the lamp while realizing the luminance uniformity of the light generated from the light source lamp. In addition, the light diffusing plate serves as a support for various optical films. Since various light diffusing agents are added to the light diffusion plate, light refraction, scattering, reflection phenomenon, etc. are caused and a diffusion effect is generated.

  Various materials such as a light diffusion film and a prism film must be attached so that a large amount of light from such a light diffusion plate can be collected on the front surface. Manufacturing costs increase and productivity decreases.

  The light diffusing film effectively disperses incident light and plays a role of collecting light on the front surface while assisting the concealability of the diffusing plate. A general light diffusion film includes a transparent substrate and a diffusion layer, and the diffusion layer is formed on the surface of the transparent substrate. The diffusion layer includes spherical material particles as a scatterer, and the diffusion effect of the light diffusion film is realized mainly by the difference in refractive index between the binder in the diffusion layer and the scatterer in the binder. Since the scatterers are dispersed between the diffusing layers, the light rays travel through the diffusing layer while reciprocating continuously between the two media having different refractive indexes.

  In addition, a prism film must be attached so that a large amount of light from the light diffusion film can be collected on the front surface. However, the prism film is expensive and has a problem of reducing productivity.

  Accordingly, an object of the present invention is to provide a light diffusing plate having a single layer structure that exhibits an appropriate luminance and is excellent in concealment.

  Another object of the present invention is to provide a light diffusing plate having a multilayer structure that exhibits an appropriate luminance and is excellent in concealment.

  Another object of the present invention is to provide a light diffusion plate having a single layer structure capable of adjusting the total light transmittance and exhibiting sufficient luminance while maintaining concealment.

  It is another object of the present invention to provide a light diffusion plate having a multilayer structure capable of adjusting the total light transmittance and exhibiting sufficient luminance while maintaining concealment.

  Another object of the present invention is to provide a light diffusing plate capable of maximizing the luminance of a display by adjusting the type and content of the light diffusing agent.

  Another object of the present invention is to provide an economical light diffusing plate by reducing the manufacturing cost of a liquid crystal display.

  Another object of the present invention is to provide a light diffusing plate that does not cause a bending phenomenon even in a high-temperature and high-humidity environment due to high dimensional stability and has excellent light characteristics.

In the first embodiment of the present invention, a base resin selected from a polycarbonate resin, a polystyrene resin, and a mixture thereof is included, a pattern layer is formed on at least one surface, a total light transmittance of 40% or more, and 4500 cd. A light diffusing plate having a luminance of / mm ² or more is provided.

In the second embodiment of the present invention, a base material layer formed of a base resin selected from a polycarbonate resin, a polystyrene resin, and a mixture thereof, and a surface layer formed on at least one surface of the base material layer And a pattern layer formed on at least one surface of the surface layer, and provides a light diffusion plate having a total light transmittance of 40% or more and a luminance of 4500 cd / mm ² or more.

  In the third embodiment of the present invention, the light diffusion includes a base resin selected from a polycarbonate resin, a polystyrene resin, and a mixture thereof, and has a haze of 90% or less and a total light transmittance of 80% or more. Provide a plate.

  In the fourth embodiment of the present invention, a base material layer formed of a base resin selected from a polycarbonate resin, a polystyrene resin, and a mixture thereof, and a surface layer formed on at least one surface of the base material layer A light diffusing plate having a haze of 90% or less and a total light transmittance of 80% or more.

  The light diffusing plate of the first to fourth embodiments of the present invention may further include a light diffusing agent having a particle size of 100 μm or less.

  In the light diffusing plate of the first to fourth embodiments of the present invention, the light diffusing agent is made of acrylic polymer particles; styrene polymer particles; olefin polymer particles; acrylic and styrene copolymers. Particles; acrylic and olefin copolymer particles; styrene and olefin copolymer particles; after forming the homopolymer, copolymer or terpolymer particles; Multi-layer multi-component particles obtained by covering the layer with other types of monomers; siloxane polymer particles; fluorine resin particles; calcium carbonate particles; barium sulfate particles; silicon oxide particles; It may be at least one selected from aluminum particles; titanium oxide particles; zirconium oxide particles; magnesium fluoride particles; talc particles; glass particles;

  The light diffusing plate of the third to fourth embodiments of the present invention may have a pattern layer further formed on at least one surface.

  In the light diffusing plate of the first to fourth embodiments of the present invention, the pattern layer has a polyhedral shape having a polygonal cross section, a semicircular shape, or a semielliptical shape, or a column shape having a cross sectional polygonal shape, a semicircular shape, or a semielliptical shape. These patterns may be adjacent to each other or not adjacent to each other.

  In the light diffusion plates of the first to fourth embodiments of the present invention, the polystyrene resin may have a glass transition temperature of 105 ° C. or higher.

  In the light diffusion plate of the first to fourth embodiments of the present invention, the polystyrene resin may be a polystyrene resin copolymerized with acrylic acid.

  According to an aspect of the present invention, the light diffusing plate is excellent in concealment while exhibiting sufficient luminance, so that the image of the light source can be sufficiently concealed even when applied to a large screen backlight unit, Due to the high dimensional stability, less bending occurs even in high temperature and high humidity environments.

  According to another aspect of the present invention, the light diffusing plate is excellent in total light transmittance and sufficiently high in luminance and can maintain a good light emission quality. The manufacturing cost can be reduced, and the high dimensional stability causes less bending phenomenon even in a high temperature and high humidity environment.

FIG. 1 is a perspective view showing a diffusion plate according to an embodiment of the present invention. FIG. 2 is a perspective view showing a diffusion plate according to another embodiment of the present invention. FIG. 3 is a perspective view showing a diffusion plate according to another embodiment of the present invention. FIG. 4 is a perspective view showing a diffusion plate according to another embodiment of the present invention.

  Hereinafter, the present invention will be described in detail.

  According to an embodiment of the present invention, a single-layer or multi-layer light diffusing plate exhibiting appropriate brightness and excellent concealability is provided. Any of such light diffusing plates may be a polycarbonate resin as a base resin. Resins or polystyrene resins may be used alone or in combination.

  Polycarbonate resin has excellent impact resistance and light transmittance, but also has excellent cold resistance and electrical characteristics, as well as high heat resistance and absorption resistance. It is a resin with a wide range and is used for optical lenses, optical disk materials, helmets, protective equipment, covers and the like.

  The polycarbonate resin used in the present invention is a commonly used aromatic carbonate resin, which is a linear and branched carbonate produced solely by reaction of dihydroxyphenol and phosgene or reaction of dihydroxyphenol and a carbonate precursor. Including polymers, polyester copolymers and mixtures thereof. The dihydroxyphenol is 2,2-bis (4-hydroxyphenyl) propane (ie, bisphenol A), bis (4-hydroxyphenyl) methane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl). Propane, 1,1-bis (4-hydroxyphenyl) cyclohexane and the like, and the carbonate precursor includes diphenyl carbonate, carbonyl halide and diallyl carbonate.

  Such a polycarbonate resin has a melt index (MI) of 7 to 30 g / 10 min according to ASTM D1238 at a temperature of 300 ° C. and a load of 1.2 kg.

  When a polystyrene resin is used alone as a base resin, one having a glass transition temperature of 105 ° C. or higher can be used as a part for improving heat resistance, for example, a polystyrene series copolymerized with acrylic acid. Examples thereof include resins.

  Polystyrene resin is hard, colorless and transparent, has good electrical properties, can be mass-produced, and is inexpensive, so it can be used in household goods such as kitchen supplies, stationery and furniture, large molded products for automobiles, and television cabinets. It is used in etc.

  When a polycarbonate resin and a polystyrene resin are mixed and used as the base resin, the polystyrene resin must have a melt index (MI) of 0.5 to 3 g / 10 min according to ASTM D1238 at a temperature of 200 ° C. and a load of 5 kg. May be used.

  When a polycarbonate resin and a polystyrene resin are mixed and used, a twin screw extruder having a screw diameter of 30 mm can be used, and melt kneading is performed at a molding temperature of 200 to 300 ° C., preferably 250 ° C. and a motor speed of 250 rpm. Can be manufactured.

  When mixing polycarbonate resin and polystyrene resin, the mixing ratio is 1: 9 to 9: 1 in order to take advantage of the flexibility and dimensional stability of polycarbonate and the high absorption resistance and strength of polystyrene. It may be a weight ratio.

  Meanwhile, in one embodiment of the present invention, the light diffusing plate may be a light diffusing plate having a multilayer structure by adding a surface layer to one or both surfaces of the base material layer.

  Rather than limiting the composition of the surface layer, for example, a surface layer using a styrene-acrylic copolymer resin in which an acrylic monomer and a styrene monomer are copolymerized is used as a base resin constituting the surface layer. Can be mentioned.

  The acrylic monomer that can be used as the monomer is at least one selected from methacrylic acid alkyl ester, acrylic acid alkyl ester, methacrylic acid cycloalkyl ester, acrylic acid cycloalkyl ester, methacrylic acid aryl ester, and acrylic acid aryl ester. It is. Examples of the styrenic monomer include styrene and substituted styrene. Examples of the substituted styrene include alkyl styrene such as α-methylstyrene, halogenated styrene such as chlorostyrene, and vinyl styrene. If necessary, two or more styrene monomers can be used in combination.

  In particular, when a styrene-acrylic copolymer resin is used, the ratio of the copolymerized acrylic monomer and styrene monomer may be 6: 4 to 1: 9 in consideration of the bonding strength with the base material layer. Good.

  The light diffusing plate of the present invention may further include a pattern layer on at least one surface, and the pattern layer can maintain appropriate luminance while improving concealment.

  The pattern layer may have a large number of patterns, and each pattern may have a polygonal shape with a cross-sectional polygon, a semicircular shape, or a semielliptical shape, or a columnar shape with a cross-sectional polygonal shape, a semicircular shape, or a semielliptical shape. It may be a combination of one or more shapes. Further, the patterns may be adjacent to each other or may not be adjacent. Examples thereof are shown in FIGS.

  FIG. 1 shows a light diffusing plate including a base layer and a surface layer, and further including a pattern layer in which a columnar shape with a semicircular cross section is linearly arranged on one surface of the surface layer, and FIG. 2 shows a light diffusing plate including pattern layers linearly arranged at regular intervals. FIG. 3 shows a light diffusing plate including a pattern layer in which columnar shapes having a deformed semicircular shape are linearly arranged at regular intervals. On the other hand, FIG. 4 shows a light diffusing plate including a pattern layer in which pyramid-shaped tetrahedrons having a triangular cross section are arranged at regular intervals.

  By further forming the pattern layer on the base material layer and / or the surface layer in this way, the image of the light source device is not seen while collecting the diffused light on the front surface by controlling the light path and maintaining the brightness appropriately. The concealment property can be improved.

Therefore, the light diffusion plate according to an embodiment of the present invention may have a total light transmittance of 40% or more and a luminance of 4500 cd / mm ² or more.

  When satisfying such a total light transmittance and brightness, it has a high hiding power and satisfies an appropriate brightness value, so that it can be applied to a backlight unit such as a large-area liquid crystal display, and an image of the light source is effective. Can be concealed.

  Although the present invention has been described with reference to the drawings, it is not intended to limit the present invention, and any modifications within the scope of the technical idea of the present invention can be made by those having ordinary knowledge in the technical field to which the present invention belongs. Obviously, it can be implemented.

  When the light diffusing plate of the present invention forms a surface layer on one or both surfaces of the base material layer, it can be produced by a known technique such as coextrusion molding, lamination, thermal bonding, surface coating, or the like. .

  In the case where the pattern layer is formed in the light diffusion plate of the present invention, known techniques such as lamination, thermal bonding, roll transfer, film transfer, press transfer, and printing technique can be applied.

  Another embodiment of the present invention provides a light diffusing plate that has a suitable hiding power and satisfies high brightness, thereby significantly reducing the use of optical films, which will be described in detail. The light diffusion plate can be achieved without a pattern layer.

  The base resin used here, the multilayer structure by forming an additional surface layer, the specific composition of the surface layer, and the like are as described above.

  In this case, a light diffusion plate having a haze of 90% or less and a total light transmittance of 80% or more can be provided. This light diffusing plate can achieve high brightness while exhibiting an appropriate hiding power, and can reduce the number of additional optical films used. In particular, this light diffusion plate is further useful as a diffusion film for a backlight unit having an appropriate area.

  If necessary, the pattern layer described above may be further provided in order to further increase the hiding power and increase the luminance.

  In all the embodiments relating to the light diffusing plate of the present invention described above, a light diffusing agent may be included. The light diffusing agent usually has a refractive index different from that of the base resin, and is used to increase the light diffusivity. The light diffusing agent serves to provide an appropriate level of concealability, transmittance, and diffusibility. .

  Various organic and inorganic particles can be used as the light diffusing agent. Examples of organic particles typically used include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, n -Butylmethyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, methylol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and these Acrylic polymer particles such as polymers, copolymers or terpolymers; styrene, substituted styrene, and their polymers, copolymers or Styrenic polymer particles such as base polymer; Olefin polymer particles such as polyethylene and polypropylene; Acrylic and styrene copolymer particles; Acrylic and olefin copolymer particles; Styrene and olefinic particles Copolymer particles: a multilayer multicomponent system obtained by forming particles of the homopolymer, copolymer or terpolymer and then covering the layer with another type of monomer. Particles; siloxane polymer particles; fluorine resin particles.

  On the other hand, examples of inorganic particles include calcium carbonate, barium sulfate, silicon oxide, aluminum hydroxide, titanium oxide, zirconium oxide, magnesium fluoride, talc, glass and mica. Usually, the light diffusibility of the organic particles is superior to that of the inorganic particles, and two or more kinds of light diffusing agents can be used in combination as required.

  The light diffusing agent exhibits a light diffusing effect even when the difference in refractive index with the base resin is large, and a relatively large amount is included when the difference in refractive index with the base resin is small. There must be.

  In addition, it was previously thought that the higher the light diffusing agent content, the higher the luminance. However, if the light diffusing agent content is too high, the luminance may rather decrease. Therefore, by adjusting the content of the light diffusing agent, it is possible to show high luminance characteristics while showing an appropriate concealing property.

  The following various methods can be used as a method for obtaining a light diffusing plate in which the hiding power and the luminance characteristics are adjusted according to the present invention, and these methods can be used alone or in combination.

  A first method for adjusting the content of the light diffusing agent in consideration of the difference in refractive index between the base resin and the light diffusing agent, and a second method for adjusting the content of the light diffusing agent in the base layer and the surface layer in the case of a multilayer. , A third method for adjusting the type of the light diffusing agent, a fourth method for adjusting the size of the light diffusing agent, and the like.

  As an example, when the content of the light diffusing agent is 10 parts by weight or less with respect to 100 parts by weight of the base resin, a light diffusing plate having a haze of 90% and a total light transmittance of 80% or more can be manufactured. When the pattern layer is further provided, the total light transmittance can be further lowered to improve the concealability, and appropriate luminance can be exhibited.

  When a light diffusing agent is used for the surface layer, the content of the light diffusing agent must be changed according to the difference in refractive index from the base resin used for the surface layer and the content of the light diffusing agent in the base layer. Instead, it may be 20 parts by weight or less with respect to 100 parts by weight of the base resin of the surface layer. The particle size of the light diffusing agent may be 100 μm or less.

  In addition, a processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer and the like can be added to the light diffusion plate of the present invention as necessary.

  Hereinafter, preferred examples of the present invention will be described in detail, but these examples are for explaining the present invention and do not limit the present invention.

(Examples 1-12)
The compositions and composition ratios of Examples 1 to 12 are as shown in Table 1 below.

  The polycarbonate resin used has a melt index (MI) according to ASTM D1238 at a temperature of 300 ° C. and a load of 1.2 kg of 22 g / 10 min.

  In this example, when a mixture of polycarbonate and polystyrene was used as the base resin, it was charged at a composition ratio shown in Table 1 and melt kneaded at a temperature of 250 ° C. with a twin screw extruder.

  The polystyrene resin used at this time has a melt index (MI) of 1.5 g / 10 min according to ASTM D1238 at a temperature of 200 ° C. and a load of 5 kg.

  As the base resin for the surface layer, a normal styrene-acrylic copolymer resin having the composition shown in Table 1 below was used.

  In the composition of the light diffusing plate according to this example, the base material layer is composed of a base resin and a light diffusing agent according to the composition shown in Table 1 below, an ultraviolet absorber B-Cap (tetraethyl-2,2 ′-( 1,4-phenylene-dimethylidene) -bismalonate) is mixed to form 0.5 parts by weight, and the surface layer is composed of a base resin and a light diffusing agent having the composition shown in Table 1 below, and an ultraviolet absorber B- It is formed by mixing 2 parts by weight of Cap (tetraethyl-2,2 ′-(1,4-phenylene-dimethylidene) -bismalonate).

  Moreover, the pattern layer formed the semi-cylindrical shape of pitch (a) 150 micrometers and height (b) 75 micrometers on the upper surface of the plate by roll coating (refer FIG. 1).

  Specifically, Examples 1 to 4 are single-layer light diffusing plates in which no surface layer is formed, and Examples 5 to 8 are light diffusing plates in which a surface layer is formed on one surface of a base material layer. Examples 9-12 are light diffusing plates in which a base material layer and a surface layer were formed with the same composition as in Examples 5-8, and surface layers were formed on both surfaces of the base material layer.

  At this time, for molding, co-extrusion was performed using a single screw extruder having a screw diameter of 135 mm and 60 mm, respectively, and the molding temperatures were 250 ° C. and 220 ° C., respectively. In Examples 1 to 4, the thickness of the base material layer was set to 2.0 mm, and in Examples 5 to 8, the thickness of the base material layer was set to 1.9 mm, and the thickness of the surface layer was set to 0.1 mm. No. 12, the thickness of the base material layer was 1.8 mm, and the thickness of the surface layer was 0.1 mm on both sides.

  Table 2 shows the results of measuring the total light transmittance, haze, luminance, deflection, moisture absorption rate, and heat distortion temperature for the light diffusion plates produced in these examples.

  Under the present circumstances, the total light transmittance and haze were measured by ASTM D1003 method, and the brightness | luminance was measured using LS-100 of Minolta.

  Deflection is measured by attaching a sheet to a 20 ″ size backlight unit, leaving it to stand at 60 ° C. and 75% relative humidity for 96 hours, and then measuring from the degree of square creaking from the bottom. After cutting to × 10 cm, it was left in water at 25 ° C. for 24 hours, and the moisture absorption rate was measured from the change in weight, and the heat distortion temperature was measured by the ASTM D648 method.

  From Table 2, it was found that all of these Examples had a very high total light transmittance of 90% or more and excellent luminance. It was also found that dimensional stability was excellent. In particular, it was found that Examples 3, 4, 7, 8, 11, and 12 having the pattern layer had higher luminance than the plate not including the pattern layer. On the other hand, Examples 2, 4, 6, 8, 10 and 12 in which the PS content of the base material layer is higher than the PC content show a lower moisture absorption rate and heat distortion temperature than the other cases, and are relatively bent. There was a tendency for the amount of deformation to be small.

  On the other hand, lamp concealment was measured for the light diffusion plates obtained in Examples 1, 2, 5, 6, 9, and 10. Specifically, after each light diffusing plate is attached to a 24-inch backlight unit and a diffusion film, a prism film, and a reflective polarizing film are sequentially placed thereon, can the image of the lamp be observed with the naked eye? When the image was not seen, it was judged as good, and when the image was seen, it was judged as bad. As a result, the lamp concealability was good in all cases.

  Further, the lamp concealment property was also measured for the light diffusion plate having the pattern layer as in Examples 3, 4, 7, 8, 11, and 12. Specifically, after each light diffusion plate is attached to a 32-inch backlight unit and a diffusion film, a prism film, and a reflective polarizing film are sequentially placed thereon, can the image of the lamp be observed with the naked eye? When the image was not seen, it was judged as good, and when the image was seen, it was judged as bad. As a result, the lamp concealability was good in all cases.

(Examples 13 to 18)
A light diffusion plate is produced by the same standard and method as in Examples 1 to 12, respectively. However, as a base resin for the base material layer, a polystyrene resin partially copolymerized with acrylic acid (glass transition temperature 115 ° C.) In Examples 15 and 16, a surface layer was formed on one surface of the base material layer, and in Examples 17 and 18, a surface layer was formed on both surfaces of the base material layer.

  The specific composition is as shown in Table 3 below.

  Each light diffusion plate thus obtained was measured for total light transmittance, haze, luminance, deflection, moisture absorption rate, and heat distortion temperature by the method described above. The results are shown in Table 4 below.

  From Table 4, when a polystyrene resin that satisfies certain thermal characteristics is used alone, it does not affect the total light transmittance, haze, deflection, etc., and dimensional stability, etc., in the same manner as that used in combination with the polycarbonate resin. Were found to show equivalent results.

(Examples 19 to 24)
A light diffusing plate is manufactured by the same standard and method as in each of Examples 1 to 12, except that the type of diffusing beads is changed from acrylic resin beads to silicon beads, and in Examples 21 to 22, the surface of the base layer is formed. A surface layer was formed, and in Examples 23 and 24, a surface layer was formed on both sides of the base material layer. The specific composition is as shown in Table 5 below.

  Each light diffusion plate thus obtained was measured for total light transmittance, haze, luminance, deflection, moisture absorption rate, and heat distortion temperature by the method described above. The results are shown in Table 6 below.

  From Table 6, it was found that the light diffusing plate including the pattern layer has a total light transmittance of nearly 40% and realizes high luminance.

  In addition, each light diffusion plate is attached to a 32-inch backlight unit, a diffusion film, a prism film, and a reflective polarizing film are sequentially placed thereon, and then whether or not the image of the lamp is observed with the naked eye. As a result of evaluation, all showed good results in lamp concealment.

10: Base material layer
20: Surface layer 30, 40, 50, 60: Pattern layer

Claims (11)

Including a base resin selected from a polycarbonate-based resin, a polystyrene-based resin, and a mixture thereof, having a pattern layer formed on at least one surface, having a total light transmittance of 40% or more and a luminance of 4500 cd / mm ² or more, Light diffusion plate. A base material layer formed of a base resin selected from polycarbonate resins, polystyrene resins and mixtures thereof;
A surface layer formed on at least one surface of the base material layer;
A pattern layer formed on at least one surface of the surface layer,
A light diffusion plate having a total light transmittance of 40% or more and a luminance of 4500 cd / mm ² or more.   A light diffusing plate comprising a base resin selected from polycarbonate resins, polystyrene resins and mixtures thereof, having a haze of 90% or less and a total light transmittance of 80% or more. A base material layer formed of a base resin selected from polycarbonate resins, polystyrene resins and mixtures thereof;
A surface layer formed on at least one surface of the base material layer,
A light diffusion plate having a haze of 90% or less and a total light transmittance of 80% or more.   The light diffusing plate according to claim 1, further comprising a light diffusing agent having a particle size of 100 μm or less.   The light diffusing agent is acrylic polymer particles; styrene polymer particles; olefin polymer particles; acrylic and styrene copolymer particles; acrylic and olefin copolymer particles; Styrene and olefin copolymer particles; forming homopolymer, copolymer or terpolymer particles and then covering the layer with other types of monomers. Multi-component particles obtained by: siloxane polymer particles; fluorine resin particles; calcium carbonate particles; barium sulfate particles; silicon oxide particles; aluminum hydroxide particles; titanium oxide particles; zirconium oxide particles; The light diffusing plate according to claim 5, wherein the light diffusing plate is at least one selected from talc particles; glass particles; and mica.   The light diffusing plate according to claim 3, further comprising a pattern layer formed on at least one surface.   The pattern layer includes a plurality of patterns having a polygonal cross-section, a semicircular or semi-elliptical polyhedron shape, or a polygonal cross-section, a semi-circular or semi-elliptical column shape, and each pattern is adjacent to each other. The light diffusing plate according to claim 1, wherein the light diffusing plate is not adjacent to the light diffusing plate.   The pattern layer includes a plurality of patterns having a polygonal cross-sectional shape, a semicircular or semi-elliptical polyhedron shape, or a columnar shape having a cross-sectional polygonal, semi-circular or semi-elliptical shape, and each pattern is adjacent to each other. The light diffusing plate according to claim 7, wherein the light diffusing plate is not adjacent to the light diffusing plate.   The light diffusion plate according to claim 1, wherein the polystyrene-based resin has a glass transition temperature of 105 ° C. or higher.   The light diffusion plate according to claim 10, wherein the polystyrene resin is a polystyrene resin copolymerized with acrylic acid.

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