CN101545987B - Light diffuser - Google Patents

Abstract

An object of the present invention is to provide a light diffusion plate that satisfies optical characteristics and does not allow people to recognize the shape of a light source (lamp) located behind a resin molded product. The light diffusion plate of the present invention is a light diffusion plate composed of a first layer and a second layer and having a thickness of 0.1 to 5.0 mm, wherein the first layer contains 0.05 parts by weight of the transparent thermoplastic resin (A) ~ 10 parts by weight of the resin composition (I) of the light diffusing agent (B) with an average particle diameter of 0.1 to 50 μm is formed, and the second layer contains 0.01 to 9 parts by weight on average with respect to 100 parts by weight of the transparent resin (C). The resin composition (II) of the light storage agent (D) whose particle diameter is 1-30 micrometers is formed.

Description

light diffuser

technical field

The present invention relates to a light-diffusing plate that has a desired plate thickness, is easy to adjust optical characteristics, and has excellent light-diffusing properties. More specifically, it relates to a light-diffusing plate that is excellent in light diffusivity and brightness by laminating layers formed of a resin composition obtained by adding a light-diffusing agent and a light storage agent to a transparent resin. form.

Background technique

In direct-type units and end-illuminated units of LCD TVs, lighting fixture covers, and switches of various devices, etc., light diffusion plates that are part of the unit components used for various light sources, such as acrylic resin or polycarbonate, are used. A light-diffusing plate formed of a resin composition in which an ester resin is used as a matrix resin and various light-diffusing agents are added.

In these applications, if a transparent thermoplastic resin is used, the light source can be seen through the resin due to light transmission, so it is expected that the shape of the light source (lamp) located behind the resin molded product will not be recognized by people, and it will be given as much as possible. A light-diffusing material that impairs the brightness of a light source.

At present, it is required to impart higher light diffusivity and brightness, and various improvements are being made in terms of the composition, refractive index, particle shape, and particle size of the light diffusing agent. Diffusion agent, therefore, the current situation is that it is difficult to achieve the required level of optical performance only by improving the light diffusion agent.

As one of the methods for solving this problem, Patent Document 1 discloses a polycarbonate resin light-diffusing laminate for direct-lit backlights, in which polycarbonate resin having a thickness of 0.05 to 0.3 mm and having a three-dimensional pattern on the surface is laminated. An ester resin film and a polycarbonate resin sheet with a thickness of 0.5 to 3 mm containing a light diffusing agent. However, the sheet with the three-dimensional pattern formed on the surface is expensive, and its handling is also very difficult. In addition, there is a problem of generating surface glare.

On the one hand, after the light storage agent is optically excited by ultraviolet rays, etc., if the irradiation is terminated, it can still emit light for a long time, so it is used for nighttime display applications such as evacuation guide signs or indicator lights (Patent Document 2, Patent Document 3) . Patent Document 4 discloses a light-diffusing plate using 0.01 to 1 part by weight of a strontium aluminate-based light storage agent having an average particle diameter of 1 to 20 μm. However, in this method, since the light storage agent is mixed in the entire panel, there is a problem that the luminance or the total light transmittance decreases more than specified. In addition, regarding the visibility of the shape of the light source (lamp), there was no significant difference compared with conventional products.

(Patent Document 1) Japanese Patent Laid-Open No. 2004-163575

(Patent Document 2) Japanese Patent Application Laid-Open No. 07-240187

(Patent Document 3) Japanese Patent Laid-Open No. 2000-156107

(Patent Document 4) Japanese Patent Laid-Open No. 2006-335973

Contents of the invention

An object of the present invention is to provide a light diffusion plate that satisfies optical characteristics and does not allow people to recognize the shape of a light source (lamp) behind a resin molded product.

As a result of earnest research by the present inventors to achieve the above object, it has been found that a light-diffusing plate having higher optical performance can be obtained by laminating or coating a layer containing a light-diffusing agent in a transparent thermoplastic resin and a layer containing a light-storage agent in a transparent resin. , thus completing the present invention.

That is, according to the present invention, the following light-diffusing plate can be provided.

1. A light diffusion plate comprising a first layer and a second layer and having a thickness of 0.1 to 5.0 mm, wherein the first layer is made of transparent thermoplastic resin (A ), the resin composition (I) containing 0.05 to 10 parts by weight of a light diffusing agent (B) with an average particle diameter of 0.1 to 50 μm is formed; the second layer is made of transparent resin (C) relative to 100 parts by weight, containing Formation of the resin composition (II) of 0.01 to 9 parts by weight of a light storage agent (D) having an average particle diameter of 1 to 30 μm.

2. The light diffusion plate as described in 1 above, wherein the transparent thermoplastic resin (A) is selected from polycarbonate resins, polyester resins, aromatic vinyl monomers, and (meth)acrylic alkyls having lower alkyl groups. One type of resin or a mixture of two or more types of resins in the group consisting of copolymers of base esters, (meth)acrylic resins, and resins having an alicyclic structure.

3. The light-diffusing plate according to the above 1, wherein the light-diffusing agent (B) is a silicon-based compound.

4. The light-diffusing plate according to the above 1, wherein the thickness of the second layer is 1 to 200 μm.

5. The light-diffusing plate according to 1 above, wherein the transparent resin (C) is one resin or two or more resins selected from the group consisting of acrylic resins, polycarbonate resins, melamine resins, and silicone resins. mixture.

6. The light-diffusing plate according to the above 1, wherein the light storage agent (D) is contained in an amount of 0.03 to 7 parts by weight.

7. The light-diffusing plate according to the above 1, wherein the light absorption wavelength of the light storage agent (D) is 200 nm to 500 nm.

8. The light-diffusing plate according to the above 1, wherein the light storage agent (D) is a strontium aluminate compound.

Description of drawings

Fig. 1 is a schematic cross-sectional view of the average brightness evaluation device in the light diffusion plate of the present invention.

Fig. 2 is a schematic plan view of the average luminance evaluation device in the light diffusion plate of the present invention.

Fig. 3 is a diagram of an apparatus (method of coating with a roller) for forming a light storage agent layer on a polycarbonate resin sheet in an example of the present invention.

Explanation of reference signs:

1 light diffuser

2 white reflective resin board

3～10 light source (cold cathode tube)

11～19 Measuring point

20 continuous extruded sheets

21 Nozzles for supplying paint containing light storage agent

22 Nozzle openings about 3mm in diameter for supplying paint

23 A roller with a diameter of about 80mm made of rubber on the outer periphery

Detailed ways

The present invention will be described in detail below.

<Light diffusion plate>

The thickness of the light diffusion plate of the present invention is 0.1-5.0 mm, preferably 0.3-4.0 mm, more preferably 0.5-3.0 mm. If the thickness is less than 0.1 mm, it is not suitable for the present invention due to insufficient rigidity, and if the thickness exceeds 5.0 mm, it is not practical from the viewpoint of weight, so it is not preferable.

Moreover, the total light transmittance of the light-diffusing plate of this invention is 40 % or more, Preferably it is 45 % or more, More preferably, it is 50 % or more. If the total light transmittance is low, the luminance will decrease, which is not preferable.

Furthermore, the haze value of the light-diffusing plate of this invention is 98% or more, Preferably it is 98.5% or more, More preferably, it is 99% or more. When the haze value is low, since the light source can be seen through the light-diffusing plate, it is not preferable.

<first floor>

The thickness, total light transmittance, and haze value of the above-mentioned light-diffusing plate largely depend on the thermoplastic resin sheet (first layer) in which the light-diffusing agent is blended and used as the base material of the light-diffusing plate.

The thickness of the thermoplastic resin sheet used as the base material of the light diffusion plate is preferably 0.08 to 4.9 mm, more preferably 0.28 to 3.9 mm, and still more preferably 0.48 to 2.9 mm,

The total light transmittance of the thermoplastic resin sheet used as the base material of the light diffusion plate is preferably 50% or more, and the haze value is preferably 98% or more. method, and a method of further including a light-diffusing agent in a transparent thermoplastic resin sheet and processing the surface shape into a concave-convex shape. In addition, the thermoplastic resin sheet may be a laminate of a light-diffusing sheet and a non-light-diffusing sheet.

The light-diffusing agent used in the method of including the light-diffusing agent in the thermoplastic resin sheet is in the form of particles, and examples thereof include inorganic particles represented by glass particles, organic particles such as polystyrene resins, (meth)acrylic resins, and silicone resins. Microparticles, among which organic microparticles are preferred.

The organic fine particles are preferably cross-linked organic fine particles, which are at least partially cross-linked during the production process and remain in the state of fine particles without being deformed during the actual use during the processing of the plastic resin. That is, fine particles that do not dissolve in the thermoplastic resin even when heated to the molding temperature of the thermoplastic resin (for example, the molding temperature of polycarbonate resin is about 350°C) are more preferable, specifically, crosslinked (methyl ) organic particles of acrylic resin and silicone resin. Particularly preferred specific examples include polymer microparticles based on partially crosslinked methyl methacrylate, and polymers having a core of poly(butyl acrylate)/shell of poly(methyl methacrylate). , a polymer having a core/shell form comprising a core and a shell of a rubbery ethylene polymer [for example, Rohm & Haas company's trade name Pararoid EXL-5136], a silicone resin having a cross-linked siloxane bond [for example, Toshiba Organic TOSUPER 120 manufactured by Silicon Co., Ltd.]. In particular, silicon-based compounds such as silicone resins are preferably used.

The average particle diameter of the said particulate light-diffusion agent is 0.1-50 micrometers, Preferably it is 0.5-30 micrometers, More preferably, it is 1-20 micrometers. The particle diameter of the light diffusing agent is the weight average particle diameter measured by the Coulter counter (Coulter counter) method, and the measuring device adopts the particle number and particle size distribution analyzer MODEL Zm of Co., Ltd. Ricoji. If the weight-average particle size is less than 0.1 μm, sufficient light diffusibility cannot be obtained, and the surface luminous property is poor. If it exceeds 50 μm, sufficient light diffusivity cannot be obtained, and the surface luminous property is poor. In order to obtain a sufficient light diffusing effect, the compounding amount, there is a defect that light transmittance is impaired and brightness unevenness increases.

The compounding ratio of the transparent thermoplastic resin and the light diffusing agent is such that the light diffusing agent is 0.05 to 10 parts by weight, preferably 0.1 to 8 parts by weight, particularly preferably 0.2 to 7 parts by weight, based on 100 parts by weight of the transparent thermoplastic resin. When the compounding quantity of a light-diffusion agent is less than 0.05 weight part, light diffusivity may run short, and a light source may transmit and be seen. On the one hand, when the compounding quantity of a light-diffusion agent exceeds 10 weight part, light transmittance may fall, and desired brightness|luminance may not be acquired.

In addition, as a method of processing the surface shape of the thermoplastic resin sheet into a concavo-convex shape, there may be mentioned a method of sandwiching a melt-extruded thermoplastic resin sheet with an embossed cooling roll having a reverse pattern of a desired pattern on the surface of the roll, or A method in which a thermoplastic resin sheet is sandwiched between flat plates having a reverse pattern of a desired pattern on the surface, heated to a heat distortion temperature or higher, and then pressurized.

Moreover, in the thermoplastic resin sheet used as a light-diffusion plate base material, a polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate, Polyester resins such as polyethylene 2,6-naphthalate, polyethylene resins, propylene-ethylene copolymers, polystyrene resins, aromatic vinyl monomers, and (meth)acrylic acid with lower alkyl groups Copolymers of alkyl esters, copolymers of terephthalic acid-ethylene glycol-cyclohexyldimethanol, (meth)acrylic resins such as polymethyl methacrylate, ring-opening polymers of norbornene-based monomers Hydrogenate, norbornene-based monomers and ring-opening copolymer hydrogenated products of other monomers capable of ring-opening copolymerization with the norbornene-based monomers, double bond parts of vinyl aromatic monomer polymers (including Aromatic ring) and hydrogenated products of vinyl aromatic monomers and other monomers that can be copolymerized with the vinyl aromatic monomers. Structural resins, etc. Among them, polycarbonate resins, polyester resins, copolymers of aromatic vinyl monomers and alkyl (meth)acrylates having a lower alkyl group, (meth)acrylic resins, and resins having an alicyclic structure are preferable. etc., polycarbonate resins are particularly preferred. Next, polycarbonate resins preferably used will be described.

The polycarbonate resin preferably used in the present invention is generally a resin obtained by reacting a dihydric phenol and a carbonate precursor by an interfacial polymerization method or a melt polymerization method. Representative examples of dihydric phenols include 2,2-bis(4-hydroxyphenyl)propane (commonly referred to as "bisphenol A"), 2,2-bis{(4-hydroxy-3-methyl base) phenyl} propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)-3-methylbutane, 2,2-bis(4- Hydroxyphenyl)-3,3-dimethylbutane, 2,2-bis(4-hydroxyphenyl)-4-methylpentane, 1,1-bis(4-hydroxyphenyl)cyclohexane , 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 9,9-bis{(4-hydroxy-3-methyl)phenyl}fluorene, and α , α'-bis(4-hydroxyphenyl)-m-diisopropylbenzene, etc. Among them, bisphenol A is preferred. These dihydric phenols may be used alone or in combination of two or more.

As the carbonate precursor, carbonyl halide (Carbonyl halide), carbonate or haloformate (Haro Holmet) etc. are used, specifically, phosgene, diphenyl carbonate or bis Dihaloformic acid esters of phenol, etc.

When the polycarbonate resin is produced by reacting the dihydric phenol and the carbonate precursor by interfacial polymerization or melt polymerization, a catalyst, a terminal stopper, an antioxidant for dihydric phenol, etc. may be used as necessary. In addition, the polycarbonate resin may be a branched polycarbonate resin in which a polyfunctional aromatic compound with more than three functions is copolymerized, or a polyester carbonate resin in which an aromatic or aliphatic difunctional carboxylic acid is copolymerized. The resin may also be a mixture of two or more obtained polycarbonate resins.

The molecular weight of the polycarbonate resin is usually 15,000 to 40,000, preferably 18,000 to 35,000 in terms of viscosity average molecular weight (M). The viscosity-average molecular weight of the present invention refers to the solution obtained by dissolving 0.7g polycarbonate resin in 100ml methylene chloride at a temperature of 20°C, from which the specific viscosity (η _sp ) is obtained and substituted into the following formula And the calculated viscosity average molecular weight.

η _sp /c=[η]+0.45×[η] ² c

[η]=1.23×10 ^-4 M ^0.83

(wherein, c=0.7, [η] is the intrinsic viscosity)

Various well-known additives, polymers, and the like can be added to the thermoplastic resin composition (I) used in the first layer of the present invention according to practically required performance and if necessary. For example, in order to suppress discoloration of resin molded products that occur when exposed to light for a long time, hindered amine-based light stabilizers, benzotriazole-based, benzophenone-based, triazine-based, and malonic acid-based ultraviolet light stabilizers can be added. Absorbents can also use these additives in combination.

<second floor>

The light-diffusing plate of the present invention is a light-diffusing plate in which a light storage agent layer (second layer) is formed on at least one surface of the thermoplastic resin sheet (first layer).

The light storage agent used in the present invention is a light storage agent commonly used as a light storage agent for synthetic resins, and examples thereof include sulfide-based light storage agents such as CaS:Bi, CaSrS:Bi, ZnCdS:Cu, and zinc sulfide-based light storage agents such as ZnS:Cu. Light storage agent. In addition, aluminum acid compounds represented by MAalbOc, etc. can also be mentioned, wherein M is composed of at least one metal element selected from calcium, strontium, and barium, and the compound is usually relative to the above-mentioned metal element represented by M Containing less than 10 mole % of an activator selected from europium, lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, ruthenium, manganese, tin, bismuth Consists of at least one of the above elements. From the viewpoint of hydrolyzability and afterglow characteristics, aluminate compounds are preferable, and strontium aluminate compounds using strontium as the metal element and europium or dysprosium as the activator are more preferable. In addition, the light absorption wavelength of the light storage agent is preferably 200 nm to 500 nm. Since brightness is excellent in the said range, it is preferable.

Furthermore, the light storage agent is required to have an average particle diameter in the range of 1 to 30 μm. The preferable average particle diameter is the range of 1-20 micrometers, More preferably, it is the range of 2-17 micrometers. When the average particle diameter is less than 1 μm, it is difficult to manufacture, so it is not practical and difficult to obtain, which is not preferable. On the other hand, when it exceeds 30 μm, the optical characteristics are impaired, which is not preferable. Furthermore, two or more light storage agents having different average particle diameters, particle size distributions, and types may be used in combination, or light storage agents having two or more particle size distributions with different particle size distributions may be used alone or in combination.

The compounding quantity of a light storage agent is 0.01-9 weight part with respect to 100 weight part of transparent resins (C). When the compounding quantity is less than 0.01 weight part, since it becomes difficult to obtain the optimization of an optical characteristic, it is unpreferable. On the other hand, since optical characteristics will be impaired when it exceeds 9 weight part, it is unpreferable. A preferable compounding amount is 0.03 to 7 parts by weight, more preferably 0.05 to 6 parts by weight, and further excellent optical properties can be obtained within the above range.

In practice, various well-known additives, polymers, and the like can be added to the resin composition (II) used in the light storage agent layer of the present invention according to the required performance and if necessary. For example, in order to suppress discoloration of resin molded products that occur when exposed to light for a long time, hindered amine light stabilizers, benzotriazoles, benzophenones, triazines, and malonic acid UV absorbers can be added. agent, these additives may also be used in combination.

In the present invention, an acrylic resin, polycarbonate resin, melamine resin, or silicone resin is preferably used as the transparent resin (C) used in the light storage agent layer.

Acrylic resin is a resin obtained by polymerizing acrylic monomers. As acrylic monomers, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, Methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, phenyl methacrylate, etc.

As the polycarbonate resin, the same polycarbonate resin as that used in the description of the above-mentioned polycarbonate resin sheet can be preferably used.

As the melamine resin, it is preferable to use a thermosetting melamine resin obtained by reacting polyols and etherified methylolmelamine in the presence of an acid catalyst, a solvent, and various additives, wherein the etherified methylolmelamine is The alkyl etherification reaction product of methylol melamine produced by the reaction of melamine and formaldehyde.

Examples of etherified methylol melamine include completely alkyl-type methylated melamine represented by hexamethoxymethyl melamine, in which a part of the methoxymethyl group of hexamethoxymethyl melamine becomes a methylol group. Substances, substances partially imino, substances partially butoxymethyl, or completely alkyl-type butylated melamine represented by hexabutoxymethylmelamine, etc., particularly preferably hexamethoxymethylolmelamine .

As the polyhydric alcohols, diols and ethylene glycols are preferably used, butanediol and hexylene glycol are preferable among the diols, and polyethylene glycol is preferable among the ethylene glycols.

As the silicone resin, a resin mainly composed of a thermosetting organopolysiloxane resin is preferable. Specifically, a silicone resin mainly composed of organopolysiloxane obtained by coating and curing a paint composed of alkoxysilane, colloidal silica, curing catalyst, solvent, and additives as necessary is preferable.

Alkoxysilane means for example methyltrimethoxysilane, ethyltrimethoxysilane, isobutyltrimethoxysilane, vinyltrimethoxysilane, gamma-methacryloxypropyltrimethoxysilane , β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, N-β(amino Trifunctional alkoxysilanes such as ethyl) γ-aminopropyltrimethoxysilane, and tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane , Tetra-isobutoxysilane and other tetrafunctional alkoxysilanes, such as tetrafunctional alkoxysilanes, or mixtures of two or more kinds of tetrafunctional alkoxysilanes, in which a part or all of them are hydrolyzed, and a condensate in which a part or all of the hydrolyzate undergoes a condensation reaction.

Colloidal silica is a substance in which silica fine particles having a particle diameter of 5 to 200 nm, preferably 5 to 40 nm, are dispersed in water or an organic solvent in a colloidal state. Alternatively, after applying a primer mainly composed of an acrylic resin, a silicon topcoat layer composed of a thermosetting film mainly composed of an organopolysiloxane resin may be applied thereon.

The cured layer of the above-mentioned acrylic resin is a cured layer obtained by curing an acrylic copolymer with a crosslinking agent. Specifically, as the acrylic copolymer, it is preferable to use 50 to 95 mol% or more of methyl methacrylate, ethyl methacrylate, etc. ester and 5-50 mole % of 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate copolymerized Acrylic copolymer.

In addition, in the present invention, as a preferable aspect, the surface of the resin layer (second layer) containing the light storage agent is provided on the light source side.

<stacking method>

In the present invention, as a method of laminating the light storage agent layer (second layer) on the thermoplastic resin sheet (first layer), melting the thermoplastic resin composition (II) for forming the light storage agent layer through a T-die A method of extruding on a thermoplastic resin sheet and laminating it. There is also a method of continuously laminating a light storage agent layer previously formed on a film on the surface of the sheet with a heating roll or the like during the production process of the thermoplastic resin sheet. In addition, there is also a co-extrusion method in which a thermoplastic resin sheet and a light storage agent layer are simultaneously melt-extruded and laminated. In addition, there is also a method of laminating a light storage agent layer on a thermoplastic resin sheet by a coating method such as dip coating, flow coating, roll coating, gravure coating, or reverse coating. Alternatively, there is also a method of laminating a thermoplastic resin sheet by transferring a transfer foil film having a light storage agent layer.

As the transfer foil film, a foil film having a multilayer structure consisting of base film/release layer/protective layer/light storage agent layer/adhesive layer is preferably used. By sticking the adhesive layer of the transfer foil film on the thermoplastic resin sheet and peeling off the release layer, the adhesive layer/storage agent layer/protection layer can be sequentially transferred on the thermoplastic resin sheet from the side of the resin sheet. layers of light diffuser panels.

When a lamination method or a co-extrusion method is used as a method of laminating a light storage agent layer on a thermoplastic resin sheet, a thermoplastic resin is preferable as the resin for forming the light storage agent layer, and an acrylic resin or polycarbonate is also preferable among thermoplastic resins. resin.

In addition, when a coating method is used as a method of laminating a light storage agent layer on a thermoplastic resin sheet, it is preferable to use a thermoplastic resin or a thermosetting resin as a material for forming the covering layer. Acrylic resins or polycarbonate resins are also preferred among thermoplastic resins. Alternatively, as the thermosetting resin, melamine resin, silicone resin, acrylic resin, or the like is preferable.

Furthermore, when a transfer foil film is used as a method of laminating the light storage agent layer on the thermoplastic resin sheet, it is easy to form the light storage agent layer into a thin film, and an acrylic copolymer is preferably used as a material for forming the coating layer.

The thickness of the light storage agent layer is preferably in the range of 1 to 200 μm, more preferably in the range of 2 to 70 μm. Among them, when the lamination method or the co-extrusion method is adopted, the thickness of the light storage agent layer is preferably in the range of 10-100 μm, more preferably in the range of 20-70 μm. In addition, when the coating method or transfer foil film is used, the thickness of the light storage agent layer is preferably in the range of 1-20 μm, more preferably in the range of 1-10 μm. In addition, the thinner the light storage agent layer is, the less likely it is to cause a warpage problem due to a difference in heat shrinkage rate or a difference in water absorption rate between the thermoplastic resin sheet and the light storage agent layer, which is preferable.

In addition, since the shape of the light source (lamp) can be more effectively hidden by applying the paint containing the light storage agent in stripes, it is preferably used.

<additive>

In the above-mentioned thermoplastic resin sheet, other components can also be blended within the scope of not impairing the object and effect of the present invention, for example, a fluorescent whitening agent, a heat stabilizer, a mold release agent, and an ultraviolet absorber can be blended according to requirements. , Blueing agent, flame retardant, flame retardant additives and other additives.

<Fluorescent whitening agent>

The fluorescent whitening agent has the effect of improving the color of the resin to white or bluish white, and improving the brightness of the light diffusion plate of the present invention. Here, the fluorescent whitening agent has the function of absorbing the energy of the ultraviolet portion of light and emitting the energy as a visible portion.

Examples of fluorescent whitening agents include stilbenzene, benzimidazoles, benzoxazoles, naphthalimides, rhodamines, coumarins, and oxazines. wait. Among them, benzoxazole-based compounds and coumarin-based compounds are preferable. One kind of these fluorescent whitening agents may be used, or two or more kinds may be used in combination. Specifically, Cayalite OS (CI Fluorescent Brightener 219:1, benzoxazole compound) manufactured by Nippon Kayaku Co., Ltd., Hatsuko-ru PSR (coumarin-based compound) manufactured by Hatsukoll Chemical Co., Ltd. compound), EASTOBRITE OB-1 manufactured by EASTOMAN Chemical Co., Ltd., etc.

The compounding amount of the fluorescent whitening agent is preferably 0.0001 to 3 parts by weight, more preferably 0.0002 to 0.5 parts by weight, still more preferably 0.0003 to 0.1 parts by weight, and especially preferably 0.0005 to 0.05 parts by weight relative to 100 parts by weight of the thermoplastic resin used. parts by weight. By controlling the blending amount of the fluorescent whitening agent within the above-mentioned range, sufficient surface luminescence can be obtained, and the effect of improving the color of the light-emitting surface can be obtained, and there is no unevenness in color (hue), so it is preferable.

<Heat Stabilizer>

In order to prevent a reduction in molecular weight or a deterioration in hue when molding a thermoplastic resin, a heat stabilizer may be used. Examples of the heat stabilizer include phosphorous acid, phosphoric acid, phosphonous acid, phosphonic acid, and esters thereof.

Specifically, triphenyl phosphite, tris(nonylphenyl) phosphite, tridecyl phosphite, trioctyl phosphite, trioctadecyl phosphite, didecyl Monophenyl phosphite, Dioctyl monophenyl phosphite, Diisopropyl monophenyl phosphite, Monobutyl diphenyl phosphite, Monodecyl diphenyl phosphite, Monooctyl Diphenyl phosphite, three (2,4-di-tert-butylphenyl) phosphite, bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, 2 , 2-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, bis(nonylphenyl)pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl) ) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tributyl phosphate, triethyl phosphate, trimethyl phosphate, triphenyl phosphate, diphenyl mono-o-biphenyl phosphate, diphenyl phosphate Butyl ester, octyl phosphate, diisopropyl phosphate, tetrakis(2,4-diisopropylphenyl)-4,4'-biphenylene diphosphonite, tetrakis(2,4-di n-Butylphenyl)-4,4'-biphenylene diphosphonite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite , Tetrakis(2,4-di-tert-butylphenyl)-4,3'-biphenylene diphosphinate, tetrakis(2,4-di-tert-butylphenyl)-3,3'- Phenylene diphosphonite, tetrakis(2,6-diisopropylphenyl)-4,4'-biphenylene diphosphonite, tetrakis(2,6-di-n-butylphenyl) )-4,4'-biphenylene diphosphonite, tetrakis(2,6-di-tert-butylphenyl)-4,4'-biphenylene diphosphonite, tetrakis(2, 6-di-tert-butylphenyl)-4,3'-biphenylene diphosphonite, tetrakis(2,6-di-tert-butylphenyl)-3,3'-biphenylene diphosphonite Phosphonate, bis(2,4-di-tert-butylphenyl)-biphenylene phosphonite, dimethyl phenylphosphonate, diethyl phenylphosphonate, dipropyl phenylphosphonate, etc., among which , preferably tris(2,4-di-tert-butylphenyl)phosphite, distearyl pentaerythritol diphosphite, trimethyl phosphate, tetrakis(2,4-di-tert-butylphenyl)-4, 4'-biphenylene diphosphonite, and bis(2,4-di-tert-butylphenyl)-biphenylene phosphonite.

These thermal stabilizers may be used alone or in combination of two or more. The heat stabilizer is preferably used in an amount of 0.001 to 0.5 parts by weight relative to 100 parts by weight of the thermoplastic resin.

<Release agent>

The mold release agent is used to improve the release property of the metal roll during extrusion molding. As the release agent, a fatty acid ester compound can be used, and the fatty acid ester is preferably a partial or full ester of a monohydric or polyhydric alcohol having 1 to 20 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms. As the partial ester or full ester of the monoalcohol or polyalcohol and saturated fatty acid, stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, stearic acid monosorbide, sorbyl Glyceryl Glyceride, Pentaerythritol Monostearate, Pentaerythritol Tetrastearate, Pentaerythritol Tetranonanoate, Propylene Glycol Monostearate, Stearyl Stearate, Palmitoyl Palmitate, Stearic Acid Butyl ester, methyl laurate, isopropyl palmitate, biphenyl biphenyl (bifenyl biphenyl), sorbitan monostearate, 2-ethylhexyl stearate, etc. Among them, stearic acid monoglyceride, stearic acid triglyceride, and pentaerythritol tetrastearate are preferably used. The amount of the fatty acid ester used is preferably 0.001 to 0.5 parts by weight relative to 100 parts by weight of the thermoplastic resin.

<Ultraviolet absorber>

A light diffusion plate made of thermoplastic resin is easily discolored because it is intermittently or continuously irradiated with light having various wavelength distributions and intensities in the ultraviolet range to visible light range from a light source for a long time. In order to prevent this discoloration, it is preferable to use an ultraviolet absorber.

As a ultraviolet absorber contained in a light-diffusion plate, the following thing is mentioned specifically. That is, examples of benzophenones include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2-hydroxy-4-octyloxybenzophenone. , 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfoxy Trihydrogen Benzophenone (2-Hiderokishi-4-Metokishi-5-Sulhokishitri Hidride Reitto Benzophenone), 2,2'-Dihydroxy-4-methoxybenzophenone, 2,2' , 4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethyl Oxy-5-sulfoxysodium benzophenone, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2-hydroxy-4-n-dodecyloxydiphenyl Methanone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, etc. Examples of triazine-based ultraviolet absorbers include 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol.

Examples of benzotriazoles include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2 -(2-Hydroxy-3,5-dicumylphenyl)phenylbenzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole Azole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-( 2-hydroxy-3,5-di-tert-butylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-( 2-hydroxy-3,5-di-tert-amylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-5-tert Butylphenyl)benzotriazole, 2-(2-hydroxy-4-octyloxyphenyl)benzotriazole, 2,2'-methylenebis(4-cumyl-6-benzotriazole oxazobenzene), 2,2'-p-phenylene bis(1,3-benzoxazin-4-one), 2-[2-hydroxy-3-(3,4,5,6-tetrahydro-o Phthalamidomethyl)-5-methylphenyl]benzotriazole.

Examples of cyclic imino esters include 2,2'-p-phenylenebis(3,1-benzoxazin-4-one), 2,2'-(4,4'-diethylene phenyl)bis(3,1-benzoxazin-4-one), 2,2'-(2,6-naphthyl)bis(3,1-benzoxazin-4-one).

Among the above, 2-hydroxy-4-n-octyloxybenzophenone, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol are preferred , 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-3,5-dicumylphenyl)phenylbenzotriazole, 2-(2- Hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl )-6-(2H-benzotriazol-2-yl)phenol], 2,2'-p-phenylenebis(3,1-benzoxazin-4-one), more preferably 2-hydroxy- 4-n-octyloxybenzophenone, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol, 2-(2-hydroxy-5 -tert-octylphenyl)benzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole- 2-yl)phenol], 2,2'-p-phenylene bis(3,1-benzoxazin-4-one), etc.

The ratio of the ultraviolet absorber to 100 parts by weight of the thermoplastic resin is preferably 0.01 to 2 parts by weight, more preferably 0.01 to 1 part by weight, further preferably 0.01 to 0.8 parts by weight, and especially preferably 0.02 to 0.5 parts by weight. When content of a ultraviolet absorber exceeds 2 weight part, it may cause deterioration of the light-diffusion plate of this invention.

Moreover, when a light-diffusion plate has a protective film containing an ultraviolet absorber, the ratio of an ultraviolet absorber is preferably 0-0.5 weight part with respect to 100 weight part of thermoplastic resins, More preferably, it is 0-0.3 weight part. On the one hand, when the light diffusion plate does not have a protective film, the ratio of the ultraviolet absorber is preferably 0.01 to 2 parts by weight, more preferably 0.02 to 1 part by weight, based on 100 parts by weight of the thermoplastic resin.

<Surface Shape of Light Diffusion Plate>

The light-diffusing plate of the present invention may have a three-dimensional pattern shape on one surface or both surfaces, for example, preferably has a rib shape (sawtooth shape), a ridge shape, or a corrugated shape with excellent light diffusing properties. By providing a concavo-convex pattern on the surface of the light-diffusing plate, brightness can be improved and light-diffusing performance can be made excellent.

As a method of obtaining a thermoplastic resin light-diffusing plate having a three-dimensional pattern shape on the surface, it is preferable to use an embossed cooling roll and a silicon roll having a reverse pattern of a desired pattern such as ribs (serrations), ridges, or corrugations on the surface of the roll. In the method of sandwiching the melt-extruded thermoplastic resin sheet between rubber rolls, it is also preferable to pinch the patterned light-diffusing plate between mirror rolls and silicone rubber rolls in the subsequent cooling rolls. According to this method, an industrially stable patterned light-diffusing plate can be produced without causing damage to manufacturing equipment.

Example

Hereinafter, the present invention will be further described by way of examples. In addition, the evaluation method is as follows.

(1) Image evaluation when mounted on a liquid crystal display

Assemble a light diffusion plate with a length of 231mm, a width of 321mm, and a thickness of 2mm to the 10.4-type direct backlight unit, so that the surface of the light diffusion plate with the resin layer containing the light storage agent becomes the side of the cold cathode lamp, and observe the liquid crystal display with the naked eye. When the color tone of the surface was observed to be excellent, it was indicated as ⊚, when the color tone of the entire surface of the display did not change, it was indicated as ◯, and when the display image became dark and there was a place where the color tone changed, it was indicated as ×.

(2) The average brightness and average brightness difference of the light diffusion plate

To the 10.4-type direct-type backlight unit, assemble a light diffusion plate with a length of 173mm, a width of 224mm, and a thickness of 2mm so that the surface of the light diffusion plate with the light storage agent resin layer becomes the side of the cold cathode lamp, and continuously turn on the light for 5000 hours, then, as The average luminance was expressed as a ratio with respect to Comparative Example 3 after measuring the luminance (cd/m ² ) at nine places of the light-diffusing plate with a luminance meter BM-7 manufactured by TOPCON Corporation. The evaluation apparatus is shown in FIG. 1 and FIG. 2 . In addition, the average luminance difference is represented by the ratio of the difference between the maximum luminance and the minimum luminance to the maximum luminance (minimum luminance/maximum luminance).

(3) Total light transmittance (Tt)

Using a light diffusion plate with a length and width of 50mm and a thickness of 2mm, according to JIS K-6735, and using an integrating sphere type total light transmittance measuring instrument NDH-2000 (C light source) manufactured by Nippon Denshoku Kogyo Co., Ltd. Determination.

(4) Haze (turbidity) (H)

Using a light diffusion plate with a length and width of 50mm and a thickness of 2mm, according to JIS K-6735, and using an integrating sphere type total light transmittance measuring instrument NDH-2000 (C light source) manufactured by Nippon Denshoku Kogyo Co., Ltd. Determination. The haze was calculated by the following formula.

H=Td/Tt×100(%)

(where, Td = scattered light transmittance)

Examples 1-8, Comparative Examples 1-3

To 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight of 24300 obtained from bisphenol A and phosgene, add 0.3 parts by weight of a cross-linked silicone resin [TOSUPER 120 manufactured by Toshiba Silicone Co., Ltd., weight average Particle size 2 μm], 0.2 parts by weight of benzotriazole UV absorber [ChemiSorb79 manufactured by CHEMIPRO Chemicals Co., Ltd. Under the conditions of 300°C, mold temperature of 260-300°C, and exhaust vacuum of 26.6kPa, a polycarbonate resin sheet with a thickness of 2mm and a width of 1000mm was melt-extruded.

Using a nozzle having a hole with a diameter of about 3 mm, along the width direction of the polycarbonate resin sheet, and at an interval of about 3 cm, supply the light storage agent strontium aluminate [Nemoto Special Chemical Co., Ltd.] in the compounding ratio shown in Table 1. Manufactured, trade names GLL-300FFS (average particle size 3.4 μm, light absorption wavelength 200-450 nm), BGL-300FFS (average particle size 3.0 μm, light absorption wavelength 200-450 nm)] and acrylic acid as a binder Coating (solvent: 2-butanol) of resin-like resin (manufactured by Shin Nakamura Co., Ltd., trade name: 2-butanol), and after 0.3 to 1 second, use a roller with a diameter of about 80 mm and the outer peripheral material to be made of rubber. Spread on the surface.

Fig. 3 shows a schematic diagram (sectional schematic diagram) of an acrylic paint coating method containing the light storage agent. In the figure, 20 denotes a continuously extruded sheet, 21 denotes a nozzle for supplying acrylic paint containing a light storage agent, 22 denotes a nozzle opening with a diameter of about 3 mm and the paint is supplied, and 23 denotes a nozzle with a diameter of about 80 mm and the outer peripheral material is made of rubber. roll. To the continuously extruded sheet, the coating material containing a light storage agent was supplied in an amount of 100 cc/min per 1 mm in the width direction. In addition, the paint containing the light storage agent remaining after roll coating is recovered in the equipment and used for resupply.

Next, the surface of the sheet coated with the light storage agent-containing paint was dried with hot air at 70 to 90° C. for about 10 to 20 seconds, and then various evaluations were performed. The measurement results are shown in Table 1.

Table 1

Embodiment 9～12, comparative example 4,5

After extruding the polycarbonate resin sheet in the same manner as in Example 1, the light storage agent strontium aluminate (manufactured by Nemoto Special Chemicals Co., Ltd., trade name GLL-300FFS ) and a coating of acrylic resin as a binder.

Next, the surface of the sheet coated with the light storage agent-containing paint was dried with hot air at 90° C. for about 10 to 20 seconds, and then various evaluations were performed. The measurement results are shown in Table 2.

Table 2

Industrial Applicability

Since the light diffusion plate of the present invention has excellent light source concealment ability, it can be used in parts covering light sources, that is, it can be used in direct-type backlight units of LCD TVs and diffusion plates of end-illuminated units, light boxes of lighting appliances, and various equipment. Switches and all applications that require light diffusion.

Claims (8)

1. light diffusing sheet; It is characterized in that; Be to constitute and thickness is the light diffusing sheet of 0.1～5.0mm by the ground floor and the second layer; Said ground floor is that the resin combination (I) of the light diffusing agent (B) of 0.1～50 μ m forms by contain 0.05～10 weight portion mean grain size with respect to the transparent thermoplastic resin (A) of 100 weight portions, and it is that the resin combination (II) of the light-accumulating agent (D) of 1～30 μ m forms that the said second layer contains 0.01～9 weight portion mean grain size by the transparent resin (C) with respect to 100 weight portions.

2. light diffusing sheet as claimed in claim 1; Wherein, transparent thermoplastic resin (A) be selected from by polycarbonate resin, vibrin, aromatic vinyl class monomer and have low alkyl group (methyl) alkyl acrylate multipolymer, (methyl) acryl resin and have a kind of resin or the two or more resin compounds in the group that the resin of ester ring type structure forms.

3. light diffusing sheet as claimed in claim 1, wherein, light diffusing agent (B) is the silicon compounds.

4. light diffusing sheet as claimed in claim 1, wherein, second layer thickness is 1～200 μ m.

5. light diffusing sheet as claimed in claim 1, wherein, transparent resin (C) is a kind of resin or the two or more resin compound that is selected from the group of being made up of acrylic resin, polycarbonate resin, melamine resin and silicones.

6. light diffusing sheet as claimed in claim 1, wherein, the content of light-accumulating agent (D) is 0.03～7 weight portion.

7. light diffusing sheet as claimed in claim 1, wherein, the light absorption wavelength of light-accumulating agent (D) is 200nm～500nm.

8. light diffusing sheet as claimed in claim 1, wherein, light-accumulating agent (D) is the strontium aluminate compounds.

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