KR20060021112A - Multi-layered light diffuser developed warpage and liquid crystal display using the same - Google Patents

Abstract

The multilayer light diffusing plate according to the present invention comprises (A) (a ₁ ) 100 parts by weight of a methacrylic resin copolymerized with 70% by weight or less of a monofunctional unsaturated monomer, (a ₂ ) a siloxane light having an average particle diameter of 1 to 20 μm. A substrate comprising a first resin composition comprising 0.1 to 10 parts by weight of a diffusing agent, (a ₃ ) 0.1 to 10 parts by weight of a styrenic light diffusing agent having an average particle diameter of 1 to 20 μm, and (a ₄ ) 0.1 to 20 parts by weight of glass fibers. layer; And (B) (b ₁₎ a monofunctional unsaturated monomer is 100 parts by weight of a meta-acrylic copolymer resin to less than 70% by weight, (b ₂₎ of the acrylic light-diffusing average particle size of 1~50 ㎛ the range of 0.1 to 30 parts by weight, and (b ₃ ) an application layer made of a second resin composition composed of 0.001 to 10 parts by weight of an antistatic agent; Characterized in that consists of.

Multi-layer diffuser, liquid crystal display (LCD), methacrylic resin, glass fiber, warpage, weather resistance

Description

Multi-layered Light Diffuser developed warpage and Liquid Crystal Display Using the Same}

Field of invention

The present invention relates to a multi-layered light diffuser plate with suppression of deformation due to heat and moisture absorption and excellent light diffusing property and a liquid crystal display device using the same. More specifically, the present invention is excellent in the ability to transmit or diffuse light while compensating for the problems of a light diffusion plate that is easily deformed due to the absorption of heat and ambient moisture from many cold cathode fluorescent lamps and direct sunlight, and has good weather resistance. The present invention relates to a multilayer light diffusing plate formed of a composition and a liquid crystal display device using the same.

Background of the Invention

Among the thermoplastic resins used as the material of the light diffusion plate for liquid crystal display (LCD), there are transparent thermoplastic resins such as methacryl resin, styrene resin, cyclic olefin resin, polycarbonate resin and the like which transmit light. .

However, when only basic resin is used and no light diffusing agent is added, there is a problem in that light transmittance and light diffusivity are not sufficient. Therefore, a light diffusion plate is prepared by adding a light diffusing agent to the transparent thermoplastic resin, and the light diffusing agent transmits light of direct light or fluorescent light with high transmittance and a hiding power such that the light source is not visible to the naked eye. It has a light diffusion effect that diffuses light.

Generally, the light diffusing agent is an inorganic or organic material having a refractive index difference of about 0.02 to 0.13 from the basic resin. The inorganic fine particles include calcium carbonate, barium sulfate, titanium dioxide, aluminum hydroxide, silica, glass, talc, mica, and white. Carbon, magnesium oxide, zinc oxide, etc. are used.

Japanese Patent Application Laid-Open No. 9-31288 adds 0.2-10 parts by weight of precipitated calcium carbonate based on methacrylic resin, and has a hexahedral structure with an average particle diameter of 1-15 μm as a light diffusing agent. Is disclosed.

Japanese Laid-Open Patent Publication No. 11-35779 discloses a composition in which barium sulfate, calcium carbonate, talc and the like are used as a methacrylic resin as a base resin, and a small amount of additives such as an ultraviolet absorber and a light stabilizer are also added.

However, the molded article prepared with the composition disclosed above, there is a difficulty in the manufacturing process due to the severe deformation depending on the cooling conditions during extrusion molding, and when applied to the light source device, it is easy to be absorbed by temperature changes and moisture absorption caused by the lighting and turning off the light source. There is a problem that warpage or wrinkles occur in the light diffusion plate. In addition, since particles having large particle diameters and small particles agglomerate with each other, there is a problem that stains occur when light penetrates or diffuses a molded article. In particular, when the inorganic light diffusing agent is used, the inorganic light diffusing agent is difficult to be evenly dispersed in the transparent thermoplastic resin, which is a matrix, and the manufacturing equipment is worn and damaged depending on the hardness of the inorganic light diffusing agent. There is a problem that a defect such as a die-line occurs.

In addition, the diffusion plate used in the liquid crystal display device causes serious process defects due to static electricity generated when the protective film is peeled off for mounting of the backlight assembly. Therefore, the antistatic agent is essentially added, but the manufacture of the single-layer diffuser plate requires a considerable amount of antistatic agent, the color of the diffuser plate is yellow, the color coordinates of the light passing through it is distorted, and the cost problem caused by the excessive addition also occurs. .

Therefore, the present inventors, in order to overcome the problems of the prior art, a first resin composition containing a siloxane light diffusing agent, a styrene light diffusing agent and a glass fiber and a second resin composition containing an acrylic diffusing agent and an antistatic agent. The use of the present invention has led to the development of a multi-layered light diffusing plate with little deformation and excellent light transmittance, light diffusing property and weather resistance, and a liquid crystal display device using the same.

An object of the present invention is to provide a multi-layer light diffusion plate with less deformation due to heat and moisture absorption.

Another object of the present invention is to provide a multi-layer light diffusion plate that can prevent the warpage phenomenon easily generated by the cooling conditions during extrusion.

Still another object of the present invention is to provide a multilayer light diffuser plate having excellent weather resistance.

It is still another object of the present invention to provide a multilayer light diffusing plate which produces less defects on die-lines and the like in the manufacture of molded articles.

Still another object of the present invention is to provide a multi-layer light diffusion plate having excellent light diffusivity.

Still another object of the present invention is to provide a liquid crystal display device having a small amount of warpage variation and excellent light resistance by using the multilayer light diffusing plate.

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

Summary of the Invention

The multilayer light diffusing plate according to the present invention comprises (A) (a ₁ ) 100 parts by weight of a methacrylic resin copolymerized with 70% by weight or less of a monofunctional unsaturated monomer, (a ₂ ) a siloxane light having an average particle diameter of 1 to 20 μm. 0.1 to 10 parts by weight of a diffusing agent, (a ₃ ) a first resin composition comprising 0.1 to 10 parts by weight of a styrenic light diffusing agent having an average particle diameter of 1 to 20 μm, and (a ₄ ) 0.1 to 20 parts by weight of glass fibers. Base layer; And (B) (b ₁₎ a monofunctional unsaturated monomer is 100 parts by weight of a meta-acrylic copolymer resin to less than 70% by weight, (b ₂₎ of the acrylic light-diffusing average particle size of 1~50 ㎛ the range of 0.1 to 30 parts by weight, and (b ₃ ) an application layer made of a second resin composition composed of 0.001 to 10 parts by weight of an antistatic agent; Characterized in that consists of. At this time, the base material layer is characterized in that laminated on one or both sides of the coating layer.

Hereinafter, the content of the present invention will be described in detail.

Detailed Description of the Invention

The multilayer light diffusing plate according to the present invention is composed of a base layer (A) made of a first resin composition and a coating layer (B) made of a second resin composition, and each of the raw materials used is as follows.

(A) First Resin Composition

The first resin composition of the present invention forms a base layer (a ₁ ) 100 parts by weight of a methacryl resin, (a ₂ ) 0.1 to 10 parts by weight of a siloxane light diffusing agent, and (a ₃ ) 0.1 to 10 parts by weight of a styrene polymer. Parts and (a ₄ ) 0.1 to 20 parts by weight of glass fibers.

(a ₁ ) Methacrylic resin

The methacryl-based resin according to the present invention is a thermoplastic resin having a transparency and used as a base resin, and has a superior weather resistance than polycarbonate resin because it does not change color even when exposed to light for a long time. For example, a methyl methacrylate resin having a high transmittance may be used.

The methacrylic resin according to the present invention is copolymerized with a monofunctional unsaturated monomer, but preferably copolymerized with 70% by weight or less of a monofunctional unsaturated monomer. More preferably, they are copolymerized with up to 50% by weight of monofunctional unsaturated monomers, and most preferably with less than about 30% by weight of monofunctional unsaturated monomers.

Monofunctional unsaturated monomers according to the present invention include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxy methacrylate Hydroxyethyl, phenyl methacrylate, chlorophenyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate and the like. Acrylic ester compounds; Unsaturated acid compounds including methacrylic acid and acrylic acid; Styrene, acrylonitrile, maleic anhydride, phenyl maleimide, cyclohexyl maleimide and the like. In the present invention, one or more of the above monofunctional unsaturated monomers may be mixed and used.

The methacryl-based resin according to the present invention may further include an impact modifier. Specific examples of the impact modifier include, but are not limited to, rubber components such as acrylic rubber and butadiene rubber. When the rubber component is copolymerized with the methacrylic resin, since the rubber component has great impact resistance and bending elastic modulus, these physical properties of the copolymerized methacrylic resin are improved.

Copolymerization of the methacrylic resin with the monofunctional unsaturated monomer can be easily carried out by those skilled in the art.

(a ₂ ) siloxane light diffusing agent

The siloxane-based light diffusing agent according to the present invention is a siloxane-based crosslinking particle, which is usually a solid silicone resin particle at room temperature, and includes both a silicone rubber having a low crosslinking density and flexibility, and a silicone resin having a high crosslinking density and a hard silicone resin. For example, the silicone resin which has a three-dimensional network structure, such as polydialkyl siloxane resin, such as polydimethyl siloxane and polydimethyl siloxane, and the siloxane which has an epoxy in a terminal group, is mentioned. The siloxane-based crosslinked particles have good weather resistance, unlike styrene-based particles used as conventional organic light diffusing agents, and have no yellowing phenomenon even when the final resin composition is exposed to light for a long time. In addition, the siloxane light diffusing agent has a refractive index of 1.40 to 1.42, which is lower than that of other organic crosslinked particles, and has an excellent advantage of obtaining light diffusion and transmittance equal to or higher than a small amount of addition.

The siloxane light diffusing agent according to the present invention is spherical crosslinked fine particles having an average particle diameter of 1 to 20 µm, and preferably 0.1 to 10 parts by weight based on 100 parts by weight of the methacryl resin. If the average particle diameter is 1 µm or less, the concealability of the light source is lowered. If the average particle diameter is 20 µm or more, a problem arises in that an excessive amount of the light diffusing agent must be added to ensure proper light diffusivity. In addition, when the amount of the light diffusing agent is 0.1 parts by weight or less, the light diffusivity of the final resin composition is not sufficient, so that it is difficult to see a lamp or to diffuse the light. There is a problem that leads to a decrease.

(a ₃ ) Styrene-based light diffusing agent

The styrene-based light diffusing agent according to the present invention is styrene-based crosslinked resin fine particles, and examples thereof include a styrene monomer and a crosslinkable monomer. Moreover, the microparticles | fine-particles obtained by suspension-polymerizing another monomer to the said styrene crosslinked resin microparticles | fine-particles can also be used. Even if styrene crosslinked resin microparticles | fine-particles are mixed with a transparent resin and melt-extruded, it is preferable that they do not melt | dissolve most and support circular spherical shape. In order to improve the weather resistance of the styrene-based crosslinked resin fine particles, light stabilizers such as benzotriazole-based, hindered amine-based, benzophenone-based and salicylic acid ester-based may be added to the resin.

The refractive index of the styrene-based crosslinked resin fine particles may be about 1.53 to 1.61, it is appropriately selected according to the component of the particles. When the styrene-based crosslinked resin fine particles have many phenyl or halogen groups, the refractive index of the particles is usually high.

The styrenic light diffusing agent according to the present invention is spherical crosslinked fine particles having an average particle diameter of 1 to 20 µm, and 0.1 to 10 parts by weight is used with respect to 100 parts by weight of the methacrylic resin.

(a ₄ ) glass fiber

Glass fiber according to the present invention is a type that is commercially distributed and used, and the glass fiber treatment agent is generally treated at the time of fiber manufacture or at a later step. Lubricants, coupling agents, surfactants, and the like are used as the glass fiber treatment agents, and lubricants are used as suitable additives to form good strands in the production of glass fibers. In addition, the coupling agent serves to impart good adhesion between the glass fiber and the resin and impart good physical properties to the glass fiber reinforcement material.

In the glass fiber according to the present invention, a mild glass fiber having a short length was used in consideration of light transmittance, light diffusivity, and the surface of the molded article. It may be added up to 0.1 to 0.2 parts by weight.

(B) Second Resin Composition

The second resin composition of the present invention forms an application layer, (b ₁ ) 100 parts by weight of a methacrylic resin copolymerized with 70% by weight or less of the monofunctional unsaturated monomer, and (b ₂ ) an acrylic particle having an average particle diameter of 1 to 50 μm. polymer 0.1 to 30 parts by weight, and (b ₃₎ made of an antistatic agent of 0.001 to 10 parts by weight.

(b ₁ ) methacrylic resin

Methacrylic resin (b ₁ ) of the second resin composition according to the present invention is the same as the above-described methacrylic resin (a ₁ ), but may be used independently of each other.

(b ₂ ) acrylic light diffusing agent

An acryl-based light diffusing agent is used in a range that does not significantly reduce light transmittance and light diffusivity in order to adjust the feel of matte or the like having a white or irregular surface on the surface of the resin plate of the present invention and to enhance design. The weight average particle diameter is about 1 μm to 50 μm and can be added from 0.1 part to 30 parts by weight to each layer. The refractive index may be about 1.46 to 1.55 and shows the same tendency as the styrenic light diffusing agent.

(b ₃ ) Antistatic Agent

In general, the methacryl-based resin has a high surface resistivity, so that charging by static electricity is large. Therefore, it is preferable to add an antistatic agent because dust may be attached to reduce aesthetics or deteriorate lighting efficiency, and the color of the lamp may change. The antistatic agent according to the present invention includes elastomers such as polyetherimideamide, polyetherester, polyetheretheramide, polyalkylene glycol and dodecyl benzenesulfonic acid, alkali metal, tertiary amine, 4 Primary ammonium, salt, alkyl amines, and the like. The antistatic agent is used in an amount of 0.001 to 10 parts by weight, preferably 0.005 to 5 parts by weight, based on 100 parts by weight of the methacrylic resin.

The resin composition according to the present invention may further include an additive within a range that does not affect the respective physical properties. For example, a ultraviolet absorber includes a benzophenone series, a benzotriazole series and the like, and a light stabilizer includes a hindered amine series and the like. In addition, a blowing agent may be added in order to prevent appearance defects caused by yellowing due to resin deterioration.

In addition, plasticizers, antioxidants, heat stabilizers, lubricants, flame retardants, fillers, mold release agents, dyes, pigments, antibacterial agents, anti-dripping agents, nucleating agents and the like can be further added. Adding the appropriate additives can be easily carried out by those skilled in the art.

In the resin composition according to the present invention, additives such as spherical siloxane light diffusing agent, styrene diffusing agent, glass fiber, acrylic diffusing agent, and antistatic agent may be added by a mechanical mixer such as a Henschel mixer or a Tumbler mixer. Is dispersed.

The method for producing a laminated light diffuser plate by molding the resin composition according to the present invention may include extrusion molding with a polishing roll, injection molding, vacuum forming, hot press molding, coextrusion molding, and film lamination according to the use of the final multilayer light diffuser plate. Method, solvent adhesion method, polymerization adhesion method, cast polymerization method, surface coating method and the like. Among them, a multilayer extrusion molding method having a polishing roll is preferable, which is obtained by melting and kneading the first resin composition and the second resin composition in two extruders, and then feeding each of them to a feed block die or a multi-manifold die to laminate the two. It is a method of manufacturing a multilayer light diffuser plate laminated in layers or three layers.

The coating layer made of the second resin composition according to the present invention is applied to one or both sides of the base layer made of the first resin composition, and the thickness thereof is particularly limited because the thickness varies depending on the application or required properties. It is not necessary to do this, but it is preferable to laminate at a thickness of 10 to 1000 mu m, more preferably at a thickness of 10 to 100 mu m.

The final multilayer light diffusing plate manufactured according to the present invention uses spherical siloxane light diffusing agent, styrene diffusing agent, and glass fiber, so that not only the deformation caused by heat and moisture of many light sources is small, but also the glass fiber having good weather resistance By using methacrylic resin, weather resistance is also excellent. That is, the display quality of the LCD is excellent because it prevents the difference in contrast between the screens generated by dozens of lamps, transmits or diffuses light with uniform brightness, and does not cause yellowing even when exposed to light for a long time. Furthermore, since the organic light diffusing agent is used rather than the conventional light diffusing plate using only the inorganic light diffusing agent, wear and damage of the multilayer light diffusing plate manufacturing equipment is reduced, and the light diffusing agent is evenly dispersed to prevent intergranulation. Antistatic agents can be used only in the surface layer to reduce manufacturing process costs.

Manufacturing a liquid crystal display device using the multilayer light diffusing plate according to the present invention can be easily carried out by those skilled in the art.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example

Example 1

Preparation of First Resin Composition

To 100 parts by weight of methyl methacrylate resin (Mitsubishi Rayon Co., VH), 2 parts by weight of siloxane-based crosslinked particles (GE Toshiba Silicon, 2000B) having an average particle diameter of 8 µm and a styrene-based crosslink having an average particle diameter of 4 µm. 0.3 parts by weight of particles (Sekisui, SBX-4) and 10 parts by weight of glass fibers (Nippon Electric Glass Co, EFH 75, length: 75 μm, diameter: 11 μm) were added.

Preparation of Second Resin Composition

To 100 parts by weight of methyl methacrylate resin (Mitsubishi Rayon Co., VH), 10 parts by weight of acrylic crosslinked particles (Ganz, GM-0806S) having an average particle diameter of 8 µm and 0.5 parts by weight of an antistatic agent (Ciba, Atmer163) were added. It was prepared by.

Fabrication of Multi-layer Diffuser Plates

In order to laminate the application layer made of the second resin composition on both sides of the base material layer made of the first resin composition, the prepared first resin composition and the second resin composition were introduced into each extruder, melted and kneaded, The feed block die was fed to form a three-layered multilayer board of 100 µm / 1800 µm / 100 µm.

Example 2

The preparation of the second resin composition was performed in the same manner as in Example 1, except that 100 parts by weight of methyl methacrylate resin (Mitsubishi Rayon Co., M100) copolymerized with styrene resin was used.

Comparative Example 1

The same procedure as in Example 1 was carried out except that glass fibers (Nippon Electric Glass Co, EFH 75, length: 75 μm, diameter: 11 μm) were not added.

Comparative Example 2

The same procedure as in Example 2 was carried out except that glass fibers (Nippon Electric Glass Co, EFH 75, length: 75 μm, diameter: 11 μm) were not added.

Example Comparative Example One 2 One 2 (A) First Resin Composition (a ₁ ) PMMA, 100 PMMA, 100 PMMA, 100 PMMA, 100 (a ₂ ) 2 2 2 2 (a ₃ ) 0.3 0.3 0.3 0.3 (a ₄ ) 10 10 0 0 (B) Second Resin Composition (b ₁ ) PMMA, 100 MS, 100 PMMA, 100 MS, 100 (b ₂ ) 10 10 10 10 (b ₃ ) 0.5 0.5 0.5 0.5

(a ₁ : methacrylic resin, a ₂ : siloxane light diffusing agent, a ₃ : styrene optical diffuser, a ₄ : glass fiber, b ₁ : methacrylic resin, b ₂ : acrylic light diffusing agent, b ₃ : charging Inhibitor)

The physical properties of the specimens prepared as described above were evaluated in the following manner, and the measurement results are shown in Table 2.

(1) Light transmittance and light scattering property: The light transmittance and the light scattering property of a multilayer board were measured with the haze meter (∑80, 日本 電 色 工業 株 式 會 company).

(2) Light Diffusion: The light diffusivity of the multilayer plate was measured by a variable photometer (GC-5000L, Nippon Denshoku).

Light Diffusion (%) = (I ₂₀ + I ₇₀ ) / (2 × I ₀ ) × 100

(I ₀ , I ₂₀ , I ₇₀ : Intensity according to transmission angle 0 degrees, 20 degrees, 70 degrees for vertical incident light)

(3) Warpage measurement: After leaving the sample of 2 mm x 300 mm x 400 mm at 60 ° C, 75%, and 96 h, the sample was placed on the surface and the warpage was measured.

(4) Weather resistance: After irradiating ultraviolet rays for 48h at a temperature of 60 ℃ using ATLAS-UVCON, the amount of YI (Yellow Index) change was measured.

Example Comparative Example One 2 One 2 Light transmittance (%) 59.17 55.89 65.12 65.03 Light scattering rate (%) 95.51 95.58 95.50 95.57 Light Diffusion Rate (%) 51.65 55.01 51.18 54.68 Deflection amount (mm) 2.72 2.65 3.01 2.92 ΔYI 1.38 1.70 1.76 2.39

From the results in Table 2, the first resin composition consisting of methacryl-based resin, siloxane-based optical acid, styrene-based optical acid, styrene-based light diffusing agent and glass fiber, and a methacryl-based resin, an acrylic light-diffusing agent and an antistatic agent Examples 1 and 2 prepared from the second resin composition showed a small amount of warpage change and excellent weatherability compared to Comparative Examples 1 and 2, in which glass fibers were not added.

The present invention uses a first resin composition containing a siloxane light diffusing agent, a styrene light diffusing agent and a glass fiber, and a second resin composition containing an acrylic diffusing agent and an antistatic agent so that the deformation is small, and the light transmittance and light diffusion are reduced. There is an effect of providing a multilayer light diffusing plate and a liquid crystal display device having excellent resistance and weather resistance.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (7)

(A) (a ₁ ) 100 parts by weight of a methacrylic resin copolymerized with 70% by weight or less of a monofunctional unsaturated monomer, (a ₂ ) 0.1 to 10 parts by weight of a siloxane light diffusing agent having an average particle diameter of 1 to 20 μm, ( a ₃ ) a base layer composed of 0.1 to 10 parts by weight of a styrene-based light diffusing agent having an average particle diameter of 1 to 20 μm and (a ₄ ) 0.1 to 20 parts by weight of glass fiber; And (B) (b ₁ ) 100 parts by weight of a methacrylic resin copolymerized with 70% by weight or less of the monofunctional unsaturated monomer, (b ₂ ) 0.1 to 30 parts by weight of an acrylic light diffusing agent having an average particle diameter of 1 to 50 μm, and (b ₃ ) an application layer made of a second resin composition composed of 0.001 to 10 parts by weight of an antistatic agent; Multilayer light diffusing plate, characterized in that consisting of. The method of claim 1, wherein the monofunctional unsaturated monomer is methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid 2 Hydroxyethyl, phenyl methacrylate, chloro phenyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc. Acrylic ester compound containing a; Unsaturated acid compounds including methacrylic acid and acrylic acid; And at least one selected from the group consisting of styrene, acrylonitrile, maleic anhydride, phenyl maleimide, and cyclohexyl maleimide. The multilayer light diffusing plate according to claim 1, wherein the coating layer is laminated on one or both surfaces of the base layer. The method of claim 1, wherein the first resin composition or the second resin composition is UV absorbers, light stabilizers, blowing agents, plasticizers, antioxidants, heat stabilizers, lubricants, flame retardants, fillers, mold release agents, dyes, pigments, antibacterial agents, anti drip agents Or an additive of any one or more of the nucleating agents. The multilayer light diffusing plate of claim 1, wherein surface irregularities are formed on at least one surface of the light diffusing plate. A backlight unit for a liquid crystal display device (LCD), comprising using the multilayer light diffusing plate of any one of claims 1 to 5. A liquid crystal display (LCD), comprising using the multilayer light diffusing plate of any one of claims 1 to 5.