KR100813747B1 - Light diffuser with excellent UV durability and optical properties - Google Patents

Abstract

Disclosed is a light diffusion plate having excellent optical properties and UV durability applicable to large size flat panel display devices and excellent mechanical properties including heat resistance and hygroscopicity. The diffusion plate includes a transparent resin layer formed of a composition selected from the group consisting of a blend composition of a copolyester-based resin and a polycarbonate resin and a copolymer composition of these resins, and in the state where the diffusion agent is not added, At least 90% overall transmittance (TT) and less than 1.0% haze in thickness, with a glass transition temperature of 105-150 ° C. and an absorbency of 0.09-0.30 wt%.

Light Diffusion Plate, Heat Resistance, Hygroscopicity, UV Absorber, Optical Properties, Polyester, Polycarbonate      

Description

 Light diffuser with excellent UV durability and optical properties

1 is a diagram schematically illustrating a multilayer structure of a light diffusion plate in which a skin layer laminated on both surfaces of a core layer is mat rolled, according to an embodiment of the present invention.

2 is a diagram schematically illustrating a multilayer structure of a light diffusion plate in which a skin layer laminated on one surface of a core layer is matte rolled according to another embodiment of the present invention.

The present invention relates to an optical element having a function of diffusing light in a process of receiving and transmitting light from a light source. More specifically, the present invention relates to a diffuser plate exhibiting excellent light transmittance and light diffusivity, and having sufficient mechanical properties to exhibit good light transmittance and light diffusivity in the environment of a flat panel display device, in particular, a back light unit (hereinafter referred to as BLU). It relates to a UV blocker that can supplement the material properties vulnerable to short wavelength ultraviolet rays emitted from the Cold Cathode Flourscent Lamp (hereafter referred to as CCFL) used in the).

In information display technology, the display device has occupied the CRT position for more than half a century. However, in the rapidly developing information age, various types of display technologies are required. Among them, flat panel display is expected to become a technology that surpasses CRT in the near future. Not only small measuring instruments but also portable computers are becoming popular, and existing CRT methods such as monitors and TVs are being coped with by flat paneling.

Flat panel display technology is mainly made up of liquid crystal display (LCD), projection display, and plasma display (PDP), which have already secured market in the TV field, and related technologies such as field emission display (FED) and electroluminescent display (ELD). With the improvement of the market, it is expected to occupy the field according to each characteristic.

LCD is a device that injects liquid crystal between two sheets of glass and applies power to the electrodes installed on the upper and lower glass plates so that the arrangement of liquid crystal molecules in each pixel changes and displays an image. Currently, the range of use of laptops, personal computer monitors, LCD TVs, automobiles, and airplanes is expanding, accounting for about 80% of the flat panel market, and since the second half of 1998, the demand for LCDs has soared worldwide.

The LCD display device is usually composed of an LCD panel unit, a driver, and a backlight unit. The LCD panel does not have self-luminous structure and merely has a function of transmitting light on the rear surface. Therefore, in the absence of light, that is, at night or indoors, it is impossible to show an image without the help of a back light. The backlight unit refers to a system for implementing the backlight of the LCD.

The backlight unit is largely composed of a lamp, sheets, a mechanism part, and a driving circuit. Since the lamp alone cannot produce uniform light over the entire area, the light guide plate, diffuser plate, reflector plate, prism, frame, etc., sheets and mechanisms are provided.

There are various methods for the backlight unit. Currently, the most widely used method is a cold cathode fluorescent lamp (LFT) with a light guiding panel (LGP) printed with a reflection pattern in the center by side light method. Cold cathode fluorescent lamps are located at the edges. At this time, the reflective pattern printed on the light guide plate is printed in a structure to reduce the phenomenon that the brightness difference occurs depending on the position of the lamp is located at the edge of the panel. Although the method of printing the reflective pattern on the light guide plate is high in productivity, the light loss caused by the printing pattern material itself is inferior in efficiency, and the larger the LCD, the worse the uniformity of the overall brightness. Therefore, this method is used for small display devices of 19 inches or less. For example, small 14 inches or less such as a vehicle and a notebook are installed outside a light guide plate and used for monitors and TVs. The 15 to 18 inch backlight unit is provided with two or three lamps each outside the light guide plate to increase brightness. Since the light guide plate method cannot produce sufficient brightness over 19 inches, a direct method in which a plurality of lamps are arranged at regular intervals under the diffuser plate is used. In this method, several fluorescent lamps are arranged in a row on the rear surface of the diffusion sheet to improve luminance and improve uniformity than the photometric type.

In order to display a bright screen, the backlight light source must be very bright. This is because the light from the light source goes through several steps before reaching the LCD, and loses its original brightness in the process. In addition, the uniformity of light throughout the screen is lost because of the scattering effect. One way to overcome this problem is to increase the size of the light source, but this is expensive installation cost, high power consumption, and also has a problem of increasing the weight a lot. Thus, several attempts have been made to improve the light source brightness without loss as much as possible during the transmission process.

In flat panel display devices such as LCDs and projection TVs, a diffuser is an optical element that plays an important role in reaching light from the light source to the viewer's eyes. The diffuser plate uniformly distributes the light from the light source and plays an important role in the direct type than in the case of LCD. Structural metering is a structure where light guided by a light guide can be uniformly distributed throughout the screen, but in the case of a direct type, several light sources are distributed below the screen, so that the point just above the light source and the point between the light source and the light source Because there is a difference in the light intensity, you have to offset it.

The most important optical characteristics of the light diffuser plate used to improve visibility in the backlight unit are light transmittance and haze, which require a total amount of light of 90% or more and 85% or more of visible light. . The light diffusivity of the light diffuser plate is provided, for example, by providing irregularities on the surface of the diffuser plate, or in a light diffuser, for example, fine particles inside the diffuser plate or fine particles in a binder coated on the surface of the diffuser plate. Can be imparted by dispersing several ten percent by weight.

Optical structures for dispersing or diffusing light are generally performed in two ways. First, there are a surface diffuser plate method of refraction or dispersion in a number of directions using surface roughness, and a bulk diffuser plate method having a flat surface and an inherent light dispersing element.

The surface diffusion type diffuser plate uses the rough surface exposed to the air to maximize the difference in refractive index between the material of the diffuser plate and the surrounding medium as much as possible and consequently spreads the incident light at the largest angle. For example, the light diffusivity is imparted by forming irregularities on the surface of the film, and the surface of the transparent resin in which the irregularities are made of polyester (PET) resin, polymethyl methacrylate (PMMA) resin or polycarbonate (PC) resin There is a light diffusion plate formed in the. However, it is difficult to simultaneously obtain excellent light transmittance and light diffusivity only by applying irregularities to the surface by embossing or sand blasting. In addition, in order to exhibit its optical effect, it must be exposed to air. Conventional diffuser substrates exhibit optical properties unsuitable for use due to moisture contained in the air.

The bulk diffuser plate is a light diffusing agent such as fine particles dispersed inside the film, and is usually made of a transparent resin made of a resin such as polymethyl methacrylate, polycarbonate, etc., calcium carbonate, titanium dioxide, glass beads, silica particles, polystyrene There is a light diffusion plate in which particles, silicone resin particles, crosslinked polymer particles and the like are dispersed. This is disclosed in Japanese Patent Laid-Open Nos. 1-172801, 2-173701, 3-78701 and the like.

As the light diffusing agent is dispersed in a solution in which plastic or curable resin is dissolved in a solvent and coated on the film surface, calcium carbonate, silica particles, acrylic polymer particles, silicone resin particles, polystyrene particles, urea resin particles, polyethylene particles And light diffusing films in which fine particles such as polycarbonate particles, PVC particles, and cured melamine resin particles are used. These are disclosed in Japanese Patent Laid-Open Nos. 10172801, 6-138308, 7-209502, 7-218705, 9-113708, and 11-160505. However, the light diffusing film has the following problems. First, there is a big difference between the density of inorganic particles such as calcium carbonate and silica particles and the density of the resin (binder) solution, and the inorganic particles are precipitated, and as a result, it is very difficult to obtain a uniform dispersion. Plastic particles tend to agglomerate with each other due to static electricity, so that the dispersing properties are low, dispersing spots are caused, and the particle concentration is also low.

In recent years, flat panel display devices have become larger and larger. This demand requires an increase in the amount of light of the light source, and when the amount of light is increased, the temperature during use becomes even higher. Conventionally, the diffusion plate is made of a transparent resin such as polymethyl methacrylate, polycarbonate, polyester, or polystyrene resin as the substrate layer. However, such polymers lack the physical properties necessary to enlarge a flat panel display device, and thus do not exhibit the optical properties required as a light diffusion plate for use in a large display device. For example, polymethyl methacrylate has excellent light transmittance, but has a low glass transition temperature (about 99 ° C.), so that it is difficult to use at high temperatures, that is, large in size, and is mainly applied to 32 inches or less. In addition, polymethyl methacrylate (PMMA) has a high absorbency, there is a disadvantage that can lead to a decrease in diffusion at high humidity. In the case of the resin having low hygroscopic resistance at high temperature in the backlight unit, which is an enclosed space, the deformation is severe and cannot be used as a diffusion plate. Therefore, the resin basically used for the diffusion plate should be a resin having high heat resistance and low moisture absorption rate.

In the case of polycarbonate, which has higher heat resistance than polymethyl methacrylate, the glass transition temperature is very high at about 138-145 degrees, and is mainly applied to 32 inches or more, but its light transmittance is slightly lower than that of polymethyl methacrylate, This high also has a problem. In order to supplement these properties, a resin (MS-600, product name of Nippon Steel Chemical Co., Ltd.), which has been absorbed by blending polystyrene and polymethyl methacrylate, has been recently developed and used partially. Compared with low glass transition temperature, heat resistance is insufficient, and hygroscopicity is also not satisfactory.

Therefore, there is still a demand for a material having excellent optical properties and physical properties that can be used in a large flat panel display device, and development of a diffuser plate having excellent optical properties including light diffusivity is urgently required in the display industry.

The present invention relates to an optical element having a function of diffusing light in a process of receiving and transmitting light from a light source. More specifically, the present invention relates to a diffuser plate exhibiting excellent light transmittance and light diffusivity and having sufficient mechanical properties to exhibit excellent light transmittance and light diffusivity in the environment of a flat panel display device.

  In order to solve the problems of PMMA, which has been used as a conventional diffusion plate material, intensive and thorough research results show that the optical properties and physical properties of the substrate used in the light diffusion plate are at least 90% or more at a thickness of 2.0 mm. It shows total light transmittance (TT) and less than 1.0% haze, and it is possible to enlarge the diffusion plate by developing resin with glass transition temperature of 105-150 ℃ and absorbency of 0.09-0.30wt%. Invented.

Accordingly, it is an object of the present invention to have a total light transmittance (TT) of at least 90% and a haze of less than 1.0% on a 2.0 mm thickness basis, a glass transition temperature of 105-150 ° C., and an absorbency of 0.09-0.30%. It is providing the resin for diffusion plates containing the transparent support layer shown.

It is another object of the present invention to provide a display diffusion plate to which a light diffusing agent is applied to the resin.

Still another object of the present invention is to provide a use for the light diffusion plate of a blend of a polyester resin and a polycarbonate resin.

Still another object of the present invention is to provide a light diffusion plate having excellent UV durability.

According to the present invention, in order to secure the optical properties and mechanical properties presented above by blending the polyester resin and the polycarbonate resin so that the optical properties are not lost by maximizing the advantages of each resin and eliminating the weakness LCD and rear projection with excellent brightness and diffusivity by combining the light diffusing agent in consideration of the refractive index of the material and the basic optical properties in order to have better physical properties than the polymethyl methacrylate used in the Prepare a diffusion plate suitable for Rear Projection.

In particular, despite the excellent physical properties, the problem of the material itself, which is a problem of UV durability is not a conventional benzotriazole, benzotriazine-based UV absorber Tetra-ethyl-2,2 '-(1,4-phenylene It provides a method for producing a diffusion plate that can be solved without affecting the color coordinates and other physical properties of the diffusion plate itself using -dimethylidene) -bismalonate-based UV absorber.

In light diffusing plates used in various displays, lighting fixtures, and display panels to improve visibility, realizing minimal light loss is very important in terms of economics and material development. This is because it minimizes the energy consumption of the light source and is also associated with the use of low luminescence light sources. For example, the use of a high intensity light source results in a higher price of the light source, resulting in a higher overall production cost. In addition, since a light source of high luminous intensity usually has a high heat generation amount, a higher heat resistance of the diffusion plate is required, so that the light transmittance of the diffusion plate is very important.

In addition, as described above, in the case of a large-area screen, a high light source is required, which is a decisive factor requiring high physical properties in heat resistance of the light diffusion plate. In this regard, as the physical properties required for the light diffusion plate, water absorption resistance is considered. The higher the moisture content, the more the light diffusing plate undergoes morphological deformation at high temperatures, so that good hygroscopicity resistance is required. In conclusion, in order to be used in the light diffusion plate, a general-purpose resin having excellent optical properties while satisfying both properties must be developed.

The physical properties of the resin developed in the present invention has a haze of less than 1.0% of a transmittance (TT) of 90% or more on a 2.0 mm thickness basis, a glass transition temperature of 105-125 ° C, and an absorbency of 0.09-0.30% by weight. Have

According to one embodiment of the invention, the composition of the resin to be developed may be prepared as a blend or composition of copolyester and polycarbonate and the specific blending ratio is based on the total weight, 10 to 60% by weight of polycarbonate and The polyester may comprise 40 to 90% by weight.

The polycarbonate resin used in the present invention may be any polycarbonate, preferably an aromatic polycarbonate, more preferably bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] It is polycarbonate containing.

As for the copolyester, terephthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid or mixtures thereof can be used as the acid component, and ethylene glycol and 1,4-cyclohexanedimethanol ( CHDM) can be used. Examples of suitable copolyesters include poly (1,4-cyclohexylenedimethylene terephthalate) (PCT), poly (1,4-cyclohexylenedimethylene naphthalenedicarboxylate) (PCN), poly (1, 4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) (PCC) can be used.

The blend or composition of copolyester and polycarbonate that may be used in the transparent support layer may include 10 to 60% by weight of polycarbonate, and 40 to 90% by weight of copolyester, based on the total weight of the composition. In this case, when the total mole% of dicarboxylic acid to 100 mole% as the copolyester acid component, from the group consisting of terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and mixtures thereof 65 to 85 mole% of the selected acid component, 15 to 35 mole% of isophthalic acid, and 0 to 20 mole% of other dicarboxylic acids containing 4-40 carbon atoms, and as a glycol component, a total of glycol units Based on mole% based on 100 mole%, 80 to 100 mole% of 1,4-cyclohexanedimethanol and 0 to 20 mole% of other glycol units having 3-13 carbon atoms are included.

In another aspect, a blend or composition of copolyester and polycarbonate that may be used in the transparent support layer may comprise 5 to 45 weight percent polycarbonate, and 55 to 95 weight percent copolyester, based on the total weight of the composition Can be. At this time, when the total mole% of dicarboxylic acid is 100 mol% as the copolyester acid component, from the group consisting of terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and mixtures thereof 80 to 100 mole percent of the selected acid component and 0 to 20 mole percent of other dicarboxylic acids containing 4-40 carbon atoms, and as a glycol component, based on 100 mole percent of the total mole percent of the glycol units. , 1 to 60 mol% of ethylene glycol, 40 to 99 mol% of 1,4-cyclohexanedimethanol and 0 to 20 mol% of other glycol units having 3-13 carbon atoms.

Blends or compositions of copolyesters and polycarbonates that can be used are described in detail in US Patent Publications 2002/0082360, 2002/0086953 and 2003/0187151.

In general, the light diffusion phenomenon of a light diffusion plate is achieved by using the difference in refractive index when light passes through different media, or by modifying the angle of incidence or exit of light when passing through a boundary with another medium.

In order to maximize the diffusibility of the light diffusing plate used for display purposes in the present invention, various particles in consideration of the refractive index and transmittance of the material described in the present invention were examined and applied, and the particle size and refractive index difference of the selected particles were used. By assembling the backlight unit, the brightness can be maximized.

Since the light diffusing particles should be compatible with the binder (resin) containing the particles, organic particles similar in refractive index to the material and spherical silicon particles having a low refractive index were used and inorganic particles having a refractive index of 1.50-1.80 were used. Also available.

     Particularly, the particle selection to be used is advantageous for solving the problem such as showing the bright line due to the spherical particles having the refractive index difference of 0.1 to 0.2 from the material to improve the shielding, and to maximize the diffusion effect with a relatively small particle amount. It is very advantageous.

The refractive index of the diffusing agent particles used increases the light diffusion effect as the difference between the material and the refractive index is larger, but when the refractive index difference is too large, it is disadvantageous in terms of increasing the brightness, so that the proper refractive index difference is obtained and sometimes similar to the material. It is preferable to use the particle | grains with a big difference.

Light diffusing particles that can be used in the present invention are methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate Latex, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, metarollacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate and 2-ethylhexyl acrylate Homopolymers, copolymers or terpolymers of monomers selected from, polyethylene, polystyrene, polypropylene, beads and silicone-based spherical particles made of a copolymer of acryl and olefinic may be used. Preferably, the material is spherical particles between 1 micron and 10 microns having a refractive index difference of about 0.1 to about 0.2. Spherical organic particles having such a refractive index difference can be easily dispersed in the resin because they have densities similar to those of the material used in the present invention (about 1.10 to 1.30 g / cm < 3 >).

The light diffusing particles used in the present invention may use different ones in type and / or size. For example, light diffusion efficiency can be enhanced by mixing two or more kinds of particles having a difference in refractive index rather than a single type. In addition, light diffusing efficiency may be increased by using particles having different refractive indices and having different sizes. Also, by applying hollow particles, brightness may be increased while maximizing light diffusing efficiency after assembling the backlight unit.

The use of particles of uniform particle size requires a large amount of particles to produce a predetermined light diffusing effect, which results in not only economic inefficiency but also lowering the overall light transmittance.

According to one embodiment of the present invention, the size of the light diffusing particles can be used to increase the light diffusion effect while reducing the content of particles by using particles of two sizes of 20 to 30 microns and 1-15 microns.

The light diffusing particles are contained 0.5-30 wt%, preferably 1-15 wt%, based on the total weight of the diffuser plate. For example, when it is 0.5 weight% or less, a predetermined light-diffusion effect cannot be acquired. On the other hand, when it exceeds 30 weight%, light transmittance falls and particle dispersibility falls and uniform particle dispersion | distribution is not obtained.

According to another embodiment of the present invention, the convex and convexity is also formed on the outer surface of the light diffusion plate by imparting light diffusivity. This can be achieved by matte roll processing. Mat roll processing can be performed to one side or both sides of the outer surface of a diffuser plate.

In addition to the light diffusing particles, the matte surface further enhances the refractive index of the light diffuser plate and thus exhibits a maximized diffusion effect. As a result, by minimizing the content of the light diffusion particles, the cost can be reduced. In addition, the matte rolled surface appears to increase the brightness.

In the present invention, the light diffusion plate may have a single layer and a multilayer structure. Multilayered structures can be advantageous because they can impart additional properties and functionality. For example, UV blocking and antistatic properties can be added to the outer layer of the multilayer structure.

1A shows a diffuser plate structure in accordance with one embodiment of the present invention. As shown, the light diffusion plate 10 of the present invention is a laminate structure including a transparent support layer 11 and a skin layer 12 laminated on one surface of the transparent support layer. In this structure, the skin layer faces away from the backlight light source.

1B shows a diffuser plate structure in accordance with another embodiment of the present invention. As shown, the light diffusing plate 10 of the present invention is a laminate structure including a transparent support layer 11 and skin layers 12 and 13 laminated on both sides of the transparent support layer.

As described above, the skin layer 12 and / or 13 is matt rolled to impart light diffusivity.

The light diffusing particles serving as light diffusing elements in the present invention are dispersed in the skin layer 12 and / or 13 or in the transparent support layer 11. Therefore, the role of the binder for the light diffusing particles may be a skin layer or a transparent support layer, and the amount of the light diffusing particles may vary with respect to the layer serving as the binder as described above.

The structure and thickness of the diffuser plate may vary depending on the display size and the desired transmittance and haze, and may vary according to the display size that is generally applied in the range of 1 to 3 mm, and the skin layer may have a property of the diffuser plate and a diffuser plate. Additives can be added to give a UV protection function to prevent yellowing and antistatic function to prevent adsorption of dust, and may have a thickness range of 50 to 200 microns depending on the product characteristics.

In the present invention, the skin layer may be made of polyester, polycarbonate, polymethyl methacrylate, polystyrene, a mixture of polystyrene and polymethyl methacrylate, or a mixture of polyester and polycarbonate.

In order to impart a function to the light diffusion plate of the present invention, the skin layer may include various additives. For example, a UV blocker, an antistatic agent, an antistatic agent and the like can be added to the skin layer. The amount of such additives is preferably used in about 2 to 10% by weight based on the weight of the skin layer. For example, when used at 2% by weight or less, the desired physical properties cannot be exhibited. On the contrary, when it exceeds 10% by weight, the overall light transmittance and light diffusion efficiency are reduced.

     In particular, the present invention can be solved by applying a UV absorber that does not modify the color coordinates of the diffusion plate in order to overcome problems such as yellowing and mechanical property degradation due to short-wave UV exposure emitted from the CCFL in the BLU, Most of the commercially available UV absorbers have a very high UV absorption effect, but the molecular structure itself contains a large amount of benzene rings or naphthalene rings, such that the initial b value is high when the UV absorbers are used.

In order to solve this problem, the present inventors have studied a UV absorber capable of maximizing the UV wavelength absorption effect with a minimum benzene ring, as a result, tetra-ethyl-2,2 '-(1,4-phenylene It has been found that -dimethylidene) -bismalonate-based compound is suitable for the purpose of the present invention. When this compound was used as a UV absorber of the light diffusion plate, it exhibited excellent UV absorption effect without affecting the color coordinates and other physical properties of the diffusion plate itself.

Accordingly, the present invention includes a UV absorber comprising a tetra-ethylethyl-2,2 '-(1,4-phenylene-dimethylidene) -bismalonate compound alone or in combination with any optional UV absorber. Provide a light diffusion plate.

In the present invention, the optional UV absorber is selected from the group consisting of benzotriazole-based, benzotriazine-based, benzophenol-based, bismalonate-based, and cyanoacrylate-based compounds.

According to an aspect of the present invention, the tetra-ethylethyl-2,2 '-(1,4-phenylene-dimethylidene) -bismalonate-based compound is 0.1 to 10% by weight based on the weight of the resin layer including the same %, More preferably 0.2 to 5.0 wt%.

According to another aspect of the invention, a UV comprising tetra-ethylethyl-2,2 '-(1,4-phenylene-dimethylidene) -bismalonate compound alone or in combination with any optional UV absorbers The absorbent is included in an amount of 0.1 to 10.0 wt%, more preferably 1.0 to 8.0 wt%, based on the weight of the resin layer including the same.

Since the yellowing phenomenon of the resin when blending the polyester resin and the polycarbonate resin mentioned in the present invention appears, in order to improve this problem, a phosphate-based heat stabilizer may be used, and in order to control heat resistance and hygroscopic resistance, respectively. When modifying the resin content of the thermal stabilizer content can be adjusted appropriately within 0.01 to 5.0wt%.

  Hereinafter, the present invention will be described in more detail with reference to exemplary but non-limiting examples.

   [Example 1]

A 1: 1 ratio of a polycarbonate resin containing a polyester resin mainly containing 1,4-cyclohexanedicarboxylic acid and bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] The phosphate-based heat stabilizer was blended to 0.3 wt% based on the total content. In order to give a light diffusion effect to the blended resin, methacrylate-based and silicon-based particles were added. The methacrylate-based organic particles had a refractive index of 1.49 and an average diameter of 8 microns, and added 0.02 wt% to the total resin. As for the silicon-based particles, a refractive index of 1.42 was used, and an average particle diameter of 2.0 microns was 0.99 wt% for the entire resin, and an average particle diameter of 1.5 microns was uniformly added to 0.05 wt% for the whole resin. Thereafter, the prepared resin was made into a light diffusion sheet having a thickness of 1.0 mm through a twin screw coextrusion facility at 260 ° C.

The light diffusion sheet thus obtained was measured for transmittance (TT) and haze (Haze) by the ASTM D1003 method using a Japanese NIPPON DENSHOKU 300A analyzer. In order to evaluate the light diffusion characteristics, the light diffusivity (Clarity) was measured according to the ASTM D1044 analysis method by using the Haze-gard plus 4725 analyzer of BYK Gardner, Germany. The heat resistance and hygroscopicity of the resin were analyzed according to ASTM D 648 and ASTM D 570, respectively. The manufactured sheet was mounted on LTA260W2-L6 (model name) produced by Taishan LCD (backlight unit manufacturer), and the brightness was increased on a stage equipped with TOPCON BM-7 under the conditions of CCFL voltage of 16.5V and dimming value of 2.8V. It was measured, and the shape stability such as bending or distortion in the backlight unit (Back light unit) was evaluated as top, middle, and bottom. UV durability was measured by using a NIPPON DENSHOKU 300A analysis equipment after measuring the YI (Yellow Index) using the NIPPON DENSHOKU 300A analytical equipment after irradiating for 10 minutes at a height of 10cm with the output of the 355nm UV lamp 130mW. The measurement results are shown in Table 1 below.

    [Example 2]

     In Example 1, a polycarbonate-based resin comprising a polyester-based resin mainly containing 1,4-cyclohexanedicarboxylic acid and bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] The same procedure was followed except that the compounding ratio was 2: The physical properties are shown in Table 1 below.

    [Example 3]

     In Example 1, a polycarbonate resin containing a polyester resin mainly composed of 1,4-cyclohexanedicarboxylic acid and bisphenol-A [2,2-bis (4-hydroxyphenyl) propane] The same procedure was followed except that the compounding ratio was 1: 1, and the physical property results are shown in Table 1.

    [Example 4]

Except for using 1.1 wt% of 8 micron methacrylate particles having a refractive index of 1.49 alone in Example 1, the physical properties are shown in Table 1.

    [Example 5]

    Except for using 1.1wt% of the 10 micron styrene-based particles having a refractive index of 1.59 alone in Example 1, the physical properties are shown in Table 1.

    [Example 6]

     Except for using 0.3wt% of 2- (2H-benzotriazole-2-yl) -4-methylphenol, a benzotriazole-based UV absorber in Example 1 was carried out in the same manner, Table 1 shows.

    [Example 7]

     0.3 wt% of the benzotriazine-based UV absorber 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-hexyloxy-phenol in Example 1 was used. Except that was carried out in the same manner, the physical properties are shown in Table 1.

    [Example 8]

   Except for using the tetra-ethyl-2,2 '-(1,4-phenylene-dimethylidene) -bismalonate-based UV absorber 0.3wt% with respect to the total content in Example 1, Physical property results are shown in Table 1.

    [Example 9]

     Coextruded in the form of a three-layer structure (thickness ratio, 0.5: 9: 0.5) having a skin layer on both sides of the core layer, and tetra-ethyl-2,2 '-(1,4-phenyl as a UV absorber for the skin layer. 6 wt% of lene-dimethylidene) -bismalonate-based UV absorber and 2- (2H-benzotriazole-2-yl) -4-methylphenol were added to the skin layer, and the core layer was the same as in Example 1. The physical properties are shown in Table 1.

   [Example 10]

    Example 11 was carried out in the same manner, except that the layer structure in the form of a two-layer structure (thickness ratio, 1: 9), the physical properties are shown in Table 1.

Table 1

division Example One 2 3 4 5 6 7 8 9 10 SHEET structure (layer ratio) fault fault fault fault fault fault fault fault 3rd floor (0.5: 0.1: 0.5) 2nd floor (1: 9) Brendby Co-PET 50 34 66 50 50 50 50 50 50 50 PC 50 66 34 50 50 50 50 50 50 50 Particle size silicon 2.0 / 0.99 1.5 / 0.05 2.0 / 0.99 1.5 / 0.05 2.0 / 0.99 1.5 / 0.05 - - 2.0 / 0.99 1.5 / 0.05 2.0 / 0.99 1.5 / 0.05 2.0 / 0.99 1.5 / 0.05 2.0 / 0.891 1.5 / 0.045 2.0 / 0.891 1.5 / 0.045 PMMA 8 / 0.02 8 / 0.02 8 / 0.02 8 / 1.1 - 8 / 0.02 8 / 0.02 8 / 0.02 8 / 0.02 8 / 0.02 PS - - - - 10 / 1.1 - - - - - UV absorber (input wt%) - - - - - 0.3 0.3 0.3 0.6 0.6 Thickness (mm) 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Heat resistance (℃) 115 126 95 114 113 115 114 115 115 114 Hygroscopicity (%) 0.15 0.28 0.17 0.15 0.18 0.15 0.16 0.15 0.15 0.15 UV durability Early 2.35 2.67 2.64 2.31 2.45 5.35 4.43 2.97 2.34 2.34 △ YI 18.0 21.0 19.0 22.0 24.0 11.0 10.5 8.7 4.3 3.9 Optical properties 1 luminance (cd) 7,200 7,120 7,140 6,500 6,600 7,090 7,060 7,170 7,160 7,170 TT 48.5 49.5 48.6 55.0 59.0 47.5 48.1 48.3 48.1 48.2 Haze 94.5 94.2 94.1 93.9 93.1 94.6 94.7 94.2 94.3 94.1 Light diffusion Clarity 2.5 2.8 2.6 4.3 4.7 2.5 2.5 2.4 2.3 2.4 Form stability Prize Prize medium Prize Prize Prize Prize Prize Prize Prize

   As described above, the diffusion plate according to the present invention is not only excellent in optical properties such as light transmittance, haze and light diffusivity, but also excellent in heat resistance and hygroscopicity compared to conventional diffusion plates, and especially without affecting color coordinates. Since UV durability shows excellent physical properties, it is suitable for application to flat display devices of large area screens.

Claims (26)

A transparent resin layer formed of a composition selected from the group consisting of a blend composition of a copolyester-based resin and a polycarbonate resin and a copolymer composition of these resins, (1) 90% or more transmittance at 1.0 mm thickness, (2) less than 1.5% haze at 1.0 mm thickness, (3) a glass transition temperature of 105 to 130 ° C., and (4) A light diffusing plate having an absorbency of 0.09-0.30 wt%. The light diffusing plate of claim 1, wherein the transparent resin layer comprises light diffusing particles and a UV absorber therein. The light diffusing plate of claim 2, wherein the blend composition comprises 5 to 65 wt% of polycarbonate resin and 35 to 95 wt% of copolyester resin based on the weight of the total blend composition. The light diffusing plate of claim 2, wherein the blend composition comprises 15 to 40 wt% of polycarbonate resin and 60 to 85 wt% of copolyester resin based on the weight of the total blend composition. The method of claim 2 or 3, The copolyester-based resin is composed of a dicarboxylic acid component and a glycol component High, The dicarboxylic acid component when the total mole% of dicarboxylic acid to 100 mole%, (1) terephthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid or its 65 to 85 mole% of acid components selected from the group consisting of mixtures, (2) 15 to 35 mole percent isophthalic acid and (3) 0 to 20 mole percent of other dicarboxylic acids containing 4-40 carbon atoms; And The glycol component is based on 100 mole% of the total mole% of the glycol unit, (1) 80 to 100 mol% of 1,4-cyclohexanedimethanol and (2) Light Diffusion comprising from 0 to 20 mole percent of other glycol units having 3-13 carbon atoms plate. The light diffusing plate of claim 3, wherein the light diffusing particles are composed of at least two kinds of particles alone or of different sizes. The light diffusing plate of claim 6 wherein the light diffusing particles are in the range of 20 to 30 microns in diameter and in the range of 1 to 15 microns. The light diffusing plate of claim 3, wherein the light diffusing particles are formed of spherical particles having a refractive index difference of about 0.1 to about 0.2 from the resin layer . The method of claim 3, wherein the light diffusing particles are methyl polysiloxane, methyl silicon, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylate Acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, metalolacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate And light diffusing plates using beads made of homopolymers, copolymers or terpolymers of monomers selected from 2-ethylhexyl acrylate, polyethylene, polystyrene, polypropylene, copolymers of acrylic and olefins. The light diffusing plate of claim 9, wherein the light diffusing agent is contained in an amount of 0.5 to 30 wt% based on the total weight of the diffusion plate. The light diffusing plate of claim 3, wherein the UV absorber comprises 0.1 to 10.0 wt% based on the total weight of the diffusion plate. The method of claim 3, wherein the UV absorber is tetra-ethyl-2,2 '-(1,4-phenylene-dimethylidene) -bismalonate compound alone or benzotriazole-based, benzotriazine-based, benzophenol-based and A light diffusion plate composed of at least one compound selected from the group consisting of cyanoacrylates and used with 0.3-10.0 wt% of the total weight of the diffusion plate. In the light diffusion plate of the multi-layer structure, formed of a composition selected from the group consisting of a blend composition of copolyester-based resin and polycarbonate-based resin and a copolymer composition of these resins, (1) 90% or more transmittance at 1.0 mm thickness (2) less than 1.5% haze at 1.0 mm thickness (3) a glass transition temperature of 105 to 130 ° C., and (4) A light diffusion plate comprising a transparent resin layer having a water absorption of 0.09-0.30 wt%. The light diffusion plate according to claim 13, wherein a skin layer is formed on at least one surface of the transparent resin layer. 15. The light diffusing plate of claim 14 wherein said multilayer structure comprises additives that impart UV blocking and antistatic functionality to any layer. 15. The light diffusing plate of claim 14 wherein said skin layer is made of polyester, polycarbonate, polymethylmethacrylate, polystyrene, a mixture of polystyrene and polymethylmethacrylate, or a blend composition of polyester and polycarbonate. 15. The light diffusing agent as claimed in claim 14, wherein the transparent resin layer has light diffusing agent therein. Particles, wherein the skin layer has a UV absorber within 0.1 based on the total weight of the diffuser plate. Light diffusion plate containing 10.0wt% 15. The method of claim 14, wherein the skin layer is tetra-ethyl-2,2 '-(1,4-phenylene-dimethylidene) -bismalonate compound alone or benzotriazole-based, benzotriazine-based, benzophenol Light diffusion plate comprising a 0.3-10.0wt% based on the total weight of the diffusion plate comprising a UV absorber is mixed with at least one compound selected from the group consisting of a group and a cyanoacrylate-based. The light diffusing plate of claim 13, wherein the blend composition comprises 5 to 65 wt% of polycarbonate resin and 35 to 95 wt% of copolyester resin, based on the weight of the total blend composition. The light diffusion plate of claim 13, wherein the blend composition comprises 15 to 40 wt% of a polycarbonate resin and 60 to 85 wt% of a copolyester resin, based on the weight of the total blend composition. The method according to claim 14 or 16, The copolyester-based resin is composed of a dicarboxylic acid component and a glycol component High, The dicarboxylic acid component when the total mole% of dicarboxylic acid to 100 mole%, (1) terephthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid or its 65 to 85 mole% of acid components selected from the group consisting of mixtures, (2) 15 to 35 mole percent isophthalic acid and (3) 0 to 20 mole percent of other dicarboxylic acids containing 4-40 carbon atoms; And The glycol component is based on 100 mole% of the total mole% of the glycol unit, (1) 80 to 100 mol% of 1,4-cyclohexanedimethanol and (2) Light Diffusion comprising from 0 to 20 mole percent of other glycol units having 3-13 carbon atoms plate. The method of claim 13 or 15, wherein the light diffusing agent has a refractive index difference with the resin layer Light diffusion plate consisting of spherical particles of about 0.1-0.2 degree. 18. The particle of claim 17, wherein the light diffusing agent is in the range of 20 to 30 microns in diameter. Light, consisting of two kinds of particles: a ruler and a particle in the range of 1 to 15 microns in diameter Diffuser plate. 18. The method of claim 14 or 17, wherein the light diffusing agent is methylpolysiloxane, methylsilyl Cone, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl Methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxy Tyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, ah Krillamide, metalolacrylamide, glycidyl methacrylate, ethyl acrylate, Selected from sobutyl acrylate, normal butyl acrylate and 2-ethylhexyl acrylate Homopolymers, copolymers or terpolymers of monomers, polyethylene, polystyrene, poly A light diffusion plate composed of beads made of propylene, acryl and olefin copolymers. The light diffusing plate of claim 17, wherein the light diffusing agent is contained in an amount of 0.5 to 30 wt% based on the total weight of the diffusion plate. delete

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