KR20070104958A - The plate for brightness enhancement - Google Patents

Abstract

A plate for enhancing the brightness is provided to maximize the brightness of a display by adjusting a sort and a quantity of an optical diffusing agent. A plate for enhancing the brightness includes a base layer(10), a surface layer(20), and an optical diffusion agent. The base layer has a styrene resin as a base resin. The surface layer is formed on a plane or both planes of the base layer. A haze of the plate for enhancing the brightness is more than 60 %. A full beam transmissivity is more than 80 %. The styrene resin has a polystyrene resin or a styrene-acryl copolymerization resin. The styrene-acryl copolymerization rein has a ratio of an acryl monomer and a styrene monomer of 6:4~1:9. The optical diffusion agent has a particle diameter less than 100 mum.

Description

Plate for Brightness Enhancement

1 is a perspective view showing a preferred embodiment of the present invention,

2 is a perspective view showing another preferred embodiment of the present invention;

3 is a perspective view showing another preferred embodiment of the present invention;

4 is a perspective view showing another preferred embodiment of the present invention.

 <Description of main parts of drawing>

10: substrate layer 20: surface layer

30, 40, 50, 60: pattern layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate for improving luminance used in a backlight unit, a lighting device, or the like of a liquid crystal display.

As the industrial society develops into an advanced information age, the importance of the electronic display device as a medium for displaying and transmitting various information is increasing day by day. CRT (Cathode Ray Tube), which has been widely used in the past, has limitations due to large installation space, which makes it difficult to increase the size. Therefore, such as liquid crystal display (LCD), plasma display panel (PDP), field emission display (FED), and organic EL It is being replaced by various flat panel display devices. Among such flat panel display devices, in particular, in the case of liquid crystal display devices (LCDs), due to the advantages of thin, light, and low power consumption as a technology-intensive device in which liquid crystal and semiconductor technologies are combined, its structure and manufacturing technology have been researched and developed. In addition to the areas where liquid crystal displays have been widely used, such as notebook computers, desktop computer monitors, and portable personal communication devices (PDAs and mobile phones), large-scale technology is gradually exceeding its limitations. It is being applied as a new display device that can replace CRT, which is synonymous with display, as it is being applied to large TV of TV.

In the liquid crystal display (LCD) device, since the liquid crystal itself cannot emit light, a separate light source is installed at the rear of the device to adjust the intensity of the passing light through the liquid crystal installed in each pixel to realize contrast. do. In more detail, the liquid crystal display device is a device for controlling the transmittance of light by using the electrical properties of the liquid crystal material, uniformity through various functional sheets or films in order to maximize the efficiency by emitting light from the light source lamp on the back of the device Indirect to implement the image by controlling the gradation of each pixel by electric way through the color filter to control the color of red, blue, green (R, G, B) through the color filter. As a light emitting display device, a light emitting device that provides a light source is an important component for determining image quality such as brightness and uniformity of a liquid crystal display device.

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

Among them, the light diffusion plate achieves the uniformity of luminance of the light emitted from the light source lamp, and at the same time, it serves as a concealing role to cover the bright line of the lamp. In addition, it serves as a support for the above various optical films. Various light diffusing agents are added to the light diffusing plate to cause light refraction, scattering, reflection, etc., and cause a diffusion effect.

In order to collect a large amount of light from such a light diffusion plate to the front, a variety of materials including a light diffusion film, a prism film should be mounted, and thus having a multi-layered material raises the unit cost and lowers productivity.

The light diffusing film effectively disperses the incident light and serves to collect light to the front while assisting the concealment of the diffusion plate. A general light diffusing film includes a transparent substrate and a diffusion layer, which is formed on the surface of the transparent substrate. The diffusion layer includes spherical material particles that are scatterers, and the diffusion effect of the light diffusion film is mainly caused by the difference in refractive index between the binder in the diffusion layer and the scatterers included in the binder. The scatterers are dispersed between the diffuser layers so that the light travels continuously between two media with different refractive indices as the light passes through the diffuser layer.

In addition, the prism film should be mounted to collect a large amount of light from the light diffusing film to the front side, which is expensive and exhibits a problem of lowering productivity.

Accordingly, the present inventors can increase the brightness by adjusting the concealment and the total light transmittance to a certain level, and thus can sufficiently increase the brightness while minimizing the application of the optical films to improve the brightness, and furthermore, the micro-patterned shape can be formed at least on the plate. Formed on one side, it is possible to maintain the light emitting quality well while further improving the brightness, and when styrene resin is used as the main component, it is possible to provide a brightness improving plate with dimensional stability. The invention was completed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a brightness improving plate capable of exhibiting sufficient brightness by adjusting total light transmittance while maintaining concealment.

In addition, an object of the present invention is to provide a brightness enhancement plate that can maximize the brightness of the display by adjusting the type and content of the light diffusing agent.

In addition, an object of the present invention is to provide an economical brightness enhancement plate at a low manufacturing cost of the liquid crystal display.

On the other hand, an object of the present invention is to provide a plate for improving luminance having excellent optical characteristics without causing warpage even in an environment of high temperature and high humidity with high dimensional stability.

The present invention for achieving the above object includes a conventional styrene-based resin as a base resin and provides a brightness improving plate having a haze of 60% or more and a total light transmittance of 80% or more. The luminance enhancing plate replaces the existing light diffusion plate and performs a complex function as described in the present invention.

In addition, the present invention is a base layer comprising a styrene resin as a base resin; And a surface layer formed on one or both surfaces of the substrate layer, and has a haze of 60% or more and a total light transmittance of 80% or more.

The styrene resin is characterized in that it comprises a polystyrene resin or a styrene-acrylic copolymer resin.

The styrene-acrylic copolymer resin is characterized in that the ratio of the copolymerized acrylic monomer and styrene monomer is 6: 4 ~ 1: 9.

The brightness improving plate further comprises a light diffusing agent having a particle diameter of 100㎛ or less.

The light diffusing agent is an acrylic polymer particle as organic particles; Styrenic polymer particles; Olefin polymer particles; Copolymer particles of acryl and styrene; Acrylic and olefin copolymer particles; Styrene- and olefin-based copolymer particles; Multi-layered multicomponent particles formed by forming particles of the homopolymer, copolymer or terpolymers and then covering the layers with other types of monomers; Siloxane-based polymer particles; It is characterized by using at least one selected from calcium carbonate, barium sulfate, silicon oxide, aluminum hydroxide, titanium oxide, zirconium oxide, magnesium fluoride, talc, glass, and mica as fluorine resin particles or inorganic particles.

The brightness enhancing plate is further characterized in that a pattern layer is formed on at least one surface.

The pattern layer may be formed of a plurality of polygonal, semi-circular or semi-elliptic polyhedral shapes or cross-sectional polygonal, semi-circular or semi-elliptic columnar patterns, and each pattern may be adjacent to or not adjacent to each other.

Hereinafter, the present invention will be described in more detail.

Although the base resin of the base material layer of this invention contains a styrene resin, polystyrene resin may be used individually, or a polystyrene resin and a polycarbonate resin may be mixed and used, and a styrene-acrylic copolymer resin may be used.

The polystyrene resin is hard, colorless and transparent, has good electrical properties, and is cheap in mass production, so it is inexpensive in kitchen appliances, stationery, furniture, daily necessities such as automobiles, large molded articles for automobiles, telephone cabinets, etc. Is being used by.

The polystyrene resin may be a resin in which a styrene monomer or a substituted styrene monomer is polymerized. Substituted styrene monomers include alkyl styrenes such as α-methylstyrene, halogenated styrenes such as chlorostyrene and vinyl styrene, and the like, and two or more styrene monomers may be used in combination if necessary.

When a mixture of the polystyrene resin and the polycarbonate resin is used, the polycarbonate resin that can be used is an aromatic polycarbonate resin which is generally used to react dihydroxy phenol and phosgene or to react dihydroxy phenol and carbonate precursor. Linear and branched carbonate homopolymers and polyester copolymers or mixtures of one or more thereof. The dihydroxy phenol is 2,2-bis (4-hydroxyphenyl) propane (ie bisphenol A), bis (4-hydroxy phenyl) methane, 2,2-bis (4-hydroxy-3,5 -Dimethylphenyl) propane and 1,1-bis (4-hydroxyphenyl) cyclohexane and the like, and the carbonate precursors include diphenyl carbonate, carbonyl halide and diaryl carbonate.

The polycarbonate resin preferably has a melt index (MI) of 7 to 30 g / 10 min at a load of 300 ° C. and 1.2 kg, which is a condition of ASTM D1238.

When the polycarbonate resin and the polystyrene resin are mixed and used as the first base resin, the polystyrene resin may have a melt index (MI) of 0.5 to 3 g / 10 min at a load of 200 ° C. and 5 kg, which is a condition of ASTM D1238. good.

For the mixing of the polycarbonate resin and the polystyrene resin, a twin screw extruder having a screw diameter of 30 mm was used, and a molding temperature was prepared by melt kneading at 200 rpm to 300 ° C., preferably 250 ° C., at 250 rpm.

At this time, the mixing ratio of the polycarbonate resin and the polystyrene resin is 1: 9 to 9: 1, because the advantage of the flexibility and dimensional stability of the polycarbonate, and the advantage of the high absorption and strength of polystyrene For this purpose, it is recommended to mix each content to be at least 60% or more.

On the other hand, a styrene-acrylic copolymer resin in which an acrylic monomer and a styrene monomer are copolymerized can be used as the base resin of the base layer.

In this case, the acrylic monomer that can be used as the monomer is at least one selected from alkyl methacrylate, alkyl acrylate, methacrylic acid cycloalkyl ester, acrylic acid cycloalkyl ester, methacrylic acid aryl ester, acrylic acid aryl ester, Styrene or substituted styrene is mentioned as said styrene-type monomer. Substituted styrenes include alkyl styrenes such as α-methylstyrene, halogenated styrenes such as chlorostyrene, vinyl styrene, and the like, and two or more styrene monomers may be used in combination if necessary.

On the other hand, the brightness improving plate of the present invention may be added to the surface layer on one or both surfaces of the base layer to produce a brightness improving plate.

The surface layer composition is not particularly limited, and as an example, a surface layer using a styrene resin that is the same as or different from the base resin of the base layer may be used as the base resin constituting the surface layer.

The brightness enhancing plate of the present invention includes a light diffusing agent, which is usually the same refractive index as the base resin, is used to increase the light diffusion rate, appropriate level of concealment, transmittance and diffusion Serves to provide sex.

As the light diffusing agent, various organic and inorganic particles are used.

Representative organic particles include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid and hydroxyethyl methacrylate. , Hydroxypropyl methacrylate, hydroxy ethyl acrylate, acrylamide, metyrol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate, Acrylic polymer particles such as styrene, substituted styrene polymers or copolymers or terpolymers thereof; Styrenic polymer particles; Olefin polymer particles such as polyethylene and polypropylene; Copolymer particles of acryl and styrene; Copolymer particles of acryl and olefins; Styrene and olefin copolymer particles; Multi-layered multicomponent particles made by forming the particles of the homopolymer, copolymer or terpolymer and then covering the layers with other types of monomers; Siloxane-based polymer particles; Fluorine resin particles and the like.

On the other hand, examples of the inorganic light diffusing agent include calcium carbonate, barium sulfate, silicon oxide, aluminum hydroxide, titanium oxide, zirconium oxide, magnesium fluoride, talc, glass, mica and the like. Normally, the organic particles have excellent light diffusivity compared to inorganic particles, and if necessary, two or more kinds of light diffusing agents can be used in combination.

At this time, the light diffusing agent exhibits a light diffusing effect even in a small amount when the refractive index with the base resin is large, and a relatively large amount should be included when the refractive index difference is small.

In addition, in the past, the higher the content of the light diffusing agent is thought to increase the brightness, but if the content of the light diffusing agent is too high may cause a phenomenon that the brightness is rather reduced. Therefore, by controlling the content of the light diffusing agent can exhibit a high brightness characteristics while showing an appropriate concealability.

According to the present invention, a styrene-based resin is used as a base resin, a haze of 60% or more, and a method of obtaining a luminance improving plate having a monolayer or multilayer structure having a total light transmittance of 80% or more. These methods may be used individually or in combination.

The first method includes 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; The second method includes a method of controlling the content of the light diffusing agent in the base layer and the surface layer in the case of a multilayer; The third method includes a method of adjusting the type of light diffusing agent; As a 4th method, the method of adjusting the size of a light-diffusion agent, etc. are mentioned.

In consideration of the above, the content of the light diffusing agent may be preferably 10 parts by weight or less based on 100 parts by weight of the first base resin.

In addition, in the case of using the light diffusing agent in the surface layer, the content of the light diffusing agent should be varied according to the refractive index of the base resin used in the surface layer and the light diffusing agent content of the base layer, 20 parts by weight based on 100 parts by weight of the surface layer base resin Part or less can be considered.

And the particle diameter of the light diffusing agent may be considered 100㎛ or less.

In addition, the processing stabilizer, ultraviolet absorber, ultraviolet stabilizer, etc. may be added to the brightness improving plate of the present invention as necessary.

On the other hand, in order to achieve high brightness by adjusting the haze and transmittance of the brightness improving plate, a pattern layer may be further formed on at least one surface during manufacturing of the brightness improving plate.

The pattern layer is formed of a plurality of patterns, the pattern may be a polygonal, semi-circular or semi-elliptic polyhedron cross section, or the cross-section is a polygonal, semi-circular or semi-elliptic columnar shape, the shape is one or more This can be formed complex. Also, each pattern may or may not be adjacent to each other. Examples are shown in FIGS. 1 to 4.

FIG. 1 illustrates a brightness enhancement plate including a base layer and a surface layer, and a pattern layer in which a columnar shape having a semicircle cross section is linearly arranged on one surface of the surface layer, and FIG. 3 is a brightness enhancing plate having linearly arranged pattern layers, and FIG. 3 illustrates a brightness enhancing plate having linearly arranged pattern layers spaced apart from each other in a semicircle whose cross section is deformed.

On the other hand, Figure 4 shows a luminance-enhancing plate is formed with a pattern layer in which the pyramidal tetrahedron having a triangular cross section is arranged at intervals.

By forming a pattern layer on the base layer and the surface layer as described above, the brightness is further increased by collecting the diffused light to the front part by controlling the optical path, and the concealability of preventing the image of the light source device from appearing on the brightness enhancing plate. Can improve.

Although the present invention has been described above with reference to the accompanying drawings, the present invention is not limited thereto. Those skilled in the art may change the present invention without departing from the technical spirit of the present invention. Self-explanatory

When the luminance-improving plate of the present invention forms a surface layer on one or both surfaces of the base layer, it can be produced by a method such as co-extrusion molding, lamination, thermal bonding, or surface coating, which is a well-known technique.

In addition, in the case where the luminance-improving plate of the present invention forms a pattern layer, known techniques such as lamination, thermal bonding, roll transfer, film transfer, press transfer, and printing techniques are applied.

Hereinafter, examples of the present invention will be described in more detail, but the scope of the present invention is not limited to these examples.

Compositions and composition ratios of Examples 1 to 18 are shown in the following [Table 1], and the polystyrene resin used was a melt index (MI) of 1.5 g / 10 min at a load of 200 ° C. and 5 kg, which is a condition of ASTM D1238.

When mixing polycarbonate and polystyrene as the base resin of the base layer in the present embodiment, the melt ratio was kneaded at a temperature of 250 ℃ by a twin screw extruder at a composition ratio of Table 1 below, the melt index (MI ) Is 22 g / 10min under ASTM D1238 standard conditions at 300 ° C and 1.2 kg load.

On the other hand, the pattern layer was patterned on the upper surface of the plate using a roll coating having a semi-cylindrical shape having a pitch (a) of 150 µm and a height (b) of 75 µm (see Fig. 1).

Examples 1 to 6 are plates for improving luminance of a single layer without forming a surface layer, Examples 7 to 12 are surface layers formed on one surface of a base layer, and Examples 13 to 18 are the same compositions as Examples 7 to 12. The substrate layer and the surface layer are formed, and each surface layer is formed on both sides of the substrate layer.

At this time, the molding was coextruded at a screw diameter of 135 mm and 60 mm, respectively, and the molding temperature was performed at 250 ° C. and 220 ° C., respectively. Examples 1 to 6 had a thickness of the substrate layer of 2.0 mm and Example 7 respectively. The thickness of the substrate layer was 1.9 mm, the thickness of the surface layer was 0.1 mm, and the thickness of the substrate layer was 1.8 mm, and the thickness of the surface layer was 0.1 mm on both sides.

Example Base layer (parts by weight) Surface layer (parts by weight) Pattern layer PS PC MS MM resin beads MS PS Bead One 1000 - - One - - × 2 800 200 - One - - × 3 - - 1000 1.3 - - × 4 1000 - - One - - ○ 5 800 200 - One - - ○ 6 - - 1000 1.3 - - ○ 7, 13 1000 - - One 100 13 × 8, 14 800 200 - One 100 13 × 9, 15 - - 1000 1.5 100 13 × 10, 16 1000 - - One 100 13 ○ 11, 17 800 200 - One 100 13 ○ 12, 18 - - 1000 1.5 100 13 ○ * PS: polystyrene, Toyo Styrene, HRM40 * PC: polycarbonate (polycarbonate obtained by reacting 2,2-bis (4-hydroxyphenyl) propane with phosgene), LG Dow, Caliber 300-22 * MS: styrene-acrylate copolymer resin, A & L, MM20 * PS bead: styrene resin bead, Sekisui

As a composition of the luminance improving plate according to the embodiment, the base layer is a base resin and a light diffusing agent according to the composition of Table 1 as a light stabilizer B-Cap (Tetra-ethyl-2,2 '-(1, 0.5 parts by weight of 4-phenylene-dimethylidene) -bismalonate) is mixed, and the surface layer is B-Cap (Tetra-ethyl-2,2′-) which is an ultraviolet absorber as a light stabilizer to the base resin and the light diffusing agent according to the composition of Table 1. 2 parts by weight of (1,4-phenylene-dimethylidene) -bismalonate) are mixed.

The results of measuring the total light transmittance, the haze, the brightness, the warpage, the moisture absorption rate, and the heat distortion temperature of the luminance improving plate manufactured in the above embodiment are shown in Table 2 below.

At this time, the total light transmittance and the haze were measured by the ASTM D1003 method, and the luminance was measured by using LS-100 of Minolta.

The curvature was measured for 96 hours at 60 ℃ and 75% relative humidity after mounting the sheet in the backlight unit of 20 ″ size. After cutting in water, the water absorption was measured from the change in weight after standing for 25 hours in water at 25 ℃, the heat deformation temperature was measured by the ASTM D648 method.

Total light transmittance (%) Haze (%) Luminance (cd / m ² ) Deflection (mm) Water absorption (%) Heat Deflection Temperature (℃) Example 1 90.9 80 5779 0.12 0.13 97.0 Example 2 91.9 79 5789 0.14 0.14 101.5 Example 3 91.5 81 5791 0.15 0.16 80.7 Example 4 89.3 83 6714 0.13 0.17 96.7 Example 5 90.1 81 6874 0.15 0.18 99.0 Example 6 90.0 84 6911 0.16 0.18 82.4 Example 7 93.1 77 5819 0.14 0.13 96.4 Example 8 93.9 76 5923 0.15 0.14 99.6 Example 9 93.2 80 5987 0.16 0.16 80.7 Example 10 92.7 80 6789 0.16 0.14 99.1 Example 11 92.5 79 6934 0.17 0.15 100.3 Example 12 92.9 83 7031 0.18 0.18 83.7 Example 13 94.2 78 5917 0.17 0.13 96.9 Example 14 94.1 78 6050 0.18 0.14 97.6 Example 15 93.9 80 6134 0.16 0.16 85.1 Example 16 93.9 81 6894 0.19 0.14 96.1 Example 17 93.5 82 7132 0.20 0.15 100.3 Example 18 93.1 82 7255 0.22 0.18 89.7

As a result of the physical property evaluation, it can be seen that the total light transmittance of all the examples is very high, 90% or more, and the luminance is excellent. In addition, it can be seen that the dimensional stability is also excellent.

Among them, Examples 4, 5, 6, 10, 11, 12, 16, 17, and 18 having a pattern layer showed higher luminance characteristics than those otherwise.

On the other hand, Examples 1, 4, 7, 10, 13, and 16 in which the PS was applied to the base layer showed lower water absorption and relatively lower tendency of warpage than the other cases.

As described above, the luminance improving plate of the present invention is excellent in total light transmittance and high in luminance to maintain a good light emitting quality, thereby minimizing the application of optical films in the future to reduce the manufacturing cost. In addition, high dimensional stability can provide a plate for improving the luminance is less generated in high temperature, high humidity environment.

Claims (8)

A plate for improving luminance, comprising styrene resin as a base resin, having a haze of 60% or more and a total light transmittance of 80% or more. A base layer containing styrene resin as a base resin; And And a surface layer formed on one or both surfaces of the substrate layer, wherein the haze is 60% or more, and the total light transmittance is 80% or more. The method according to claim 1 or 2, The styrene resin is a plate for improving brightness, characterized in that it comprises a polystyrene resin or a styrene-acrylic copolymer resin. The method of claim 3, wherein The styrene-acrylic copolymer resin is a luminance-enhancing plate, characterized in that the ratio of the copolymerized acrylic monomer and styrene monomer is 6: 4 ~ 1: 9. The method according to claim 1 or 2, The brightness improving plate further comprises a light diffusing agent having a particle diameter of 100㎛ or less. The method of claim 5, The light diffusing agent is an acrylic polymer particle as organic particles; Styrenic polymer particles; Olefin polymer particles; Copolymer particles of acryl and styrene; Acrylic and olefin copolymer particles; Styrene- and olefin-based copolymer particles; Multi-layered multicomponent particles formed by forming particles of the homopolymer, copolymer or terpolymers and then covering the layers with other types of monomers; Siloxane-based polymer particles; A plate for improving luminance, characterized by using at least one selected from calcium carbonate, barium sulfate, silicon oxide, aluminum hydroxide, titanium oxide, zirconium oxide, magnesium fluoride, talc, glass, and mica as fluorine resin particles or inorganic particles. . The method according to claim 1 or 2, The brightness enhancing plate further comprises a pattern layer on at least one surface. The method of claim 7, wherein The pattern layer is formed of a plurality of polygonal, semi-circular or semi-elliptic polyhedron shape or cross-sectional polygonal, semi-circular or semi-elliptic columnar pattern, each pattern is adjacent or non-adjacent luminance Enhancement Plate.

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