JP2008268416A - Light diffusion sheet and backlight unit for liquid crystal display using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusion sheet improving damage resistance/screen printing suitability by continuously producing a large amount of the light diffusion sheets by using a large capacity tank. <P>SOLUTION: In the light diffusion sheet provided with a light diffusion layer including a light diffusion agent in a binder, a transparent base material and a sticking prevention layer in the order, the sticking prevention layer or the light diffusion layer comprises layers applying and drying water-based application liquid including an aqueous resin (A), and at least one (B) selected from a water-soluble titanium chelate compound, water-soluble titanium acylate compound, a water-soluble zirconium chelate compound and a water-soluble zirconium acylate compound. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light diffusion sheet used for a backlight unit incorporated in a liquid crystal display device and a backlight unit using the light diffusion sheet.

In the liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back surface is widely used, and a backlight unit is provided on the lower surface side of the liquid crystal layer. As shown in FIG. 2, the backlight unit 20 generally includes a rod-shaped lamp 21 as a light source, a rectangular plate-shaped light guide plate 22 that is disposed so that an end thereof is along the lamp 21, and a light guide plate. The light diffusion sheet 23 disposed on the front surface side of the light diffusion sheet 23 and the prism sheet 24 disposed on the front surface side of the light diffusion sheet 23 are provided. (For example, refer to Patent Documents 1 and 2.)
The function of the backlight unit 20 will be described. First, a light beam incident on the light guide plate 22 from the lamp 21 is reflected by a reflective dot or a reflection sheet (not shown) on the back surface of the light guide plate 22 and each side surface. Emitted from the surface. The light beam emitted from the light guide plate 22 enters the light diffusion sheet 23, is diffused, and is emitted from the surface of the light diffusion sheet 23. Thereafter, the light beam emitted from the light diffusion sheet 23 is incident on the prism sheet 24 and is emitted as a light beam having a distribution having a peak in a substantially upward direction by the prism portion 24 a formed on the surface of the prism sheet 24. In this way, the light emitted from the lamp 21 is diffused by the light diffusion sheet 23 and refracted by the prism sheet 24 so as to have a peak in a substantially directly upward direction. Illuminate.

  Although not shown, there is also a backlight unit in which a light diffusion sheet and a prism sheet are further provided on the surface side of the prism sheet 24 in consideration of the light condensing characteristics of the prism sheet 24 described above.

Conventionally, the anti-sticking layer and the light diffusion layer are usually provided by applying and drying a coating liquid mainly composed of an organic solvent. However, in recent years, needs for improving environmental suitability and reducing exposure to organic solvents during work have increased, and methods for coating a sticking prevention layer and a light diffusion layer with a coating liquid mainly composed of water have been studied. However, since the pot life after preparation of the coating solution, the so-called pot life, is short, it is difficult to carry out continuous production for a long time using a large-capacity tank, and there is a problem that productivity is lowered.
Japanese Patent Laid-Open No. 7-5305 JP 2000-89007 A

  The present invention has been made in view of the above-mentioned problems, and as a result of intensive studies by the inventor on the materials and characteristic values constituting the light diffusion layer and the anti-sticking layer in the light diffusion sheet, the present invention Has been completed. That is, the gist of the present invention is that a transparent base sheet, a light diffusing layer laminated on one surface of the base sheet, and beads dispersed in the binder, and the base sheet In the light diffusion sheet including the anti-sticking layer laminated on the other surface, the anti-sticking layer or the light diffusion layer includes an aqueous resin (A), a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, a water-soluble This is achieved by applying an aqueous coating solution containing at least one selected from the above-mentioned zirconium chelate compounds and water-soluble zirconium acylate compounds (B) and applying a dried layer.

  An object of the present invention is to provide a light diffusion sheet that enables continuous production of a large amount of light diffusion sheet using a large-capacity tank and that has improved scratch resistance and suitability for screen printing.

  The above object of the present invention is achieved by the following configurations.

  1. A light diffusing sheet comprising a light diffusing layer containing a light diffusing agent in a binder, a transparent substrate and an anti-sticking layer in this order, wherein the anti-sticking layer or the light diffusing layer comprises an aqueous resin (A), a water-soluble resin An aqueous coating solution containing at least one selected from a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, a water-soluble zirconium chelate compound, and a water-soluble zirconium acylate compound, and dried. A light diffusion sheet comprising a layer.

  2. The aqueous resin (A) and at least one selected from a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, a water-soluble zirconium chelate compound, and a water-soluble zirconium acylate compound (B) 2. The light diffusing sheet according to 1 above, wherein the layer coated with an aqueous coating solution and dried is the outermost layer.

  3. 3. The light diffusing sheet according to 1 or 2 above, wherein the aqueous resin (A) contains at least one of an aqueous polyester resin, an aqueous resin containing a hydroxyl group, and an aqueous resin containing a carboxyl group.

  4). A lamp, a light guide plate that is arranged on the side of the lamp and guides light emitted from the lamp in a front side direction, and the light diffusion sheet according to any one of 1 to 3 that is arranged on the front side of the light guide plate A backlight unit for a liquid crystal display device.

  According to the method of the present invention, it is possible to produce a high-productivity, high-quality light diffusion sheet and backlight unit using an aqueous coating solution excellent in environmental suitability and work safety.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

  Referring to FIG. 1, in general, a light diffusion sheet 1 of the present invention includes a base sheet 2, a light diffusion layer 3 laminated on one surface (surface) of the base sheet 2, and the other of the base sheet 2. It is comprised from the sticking prevention layer 4 laminated | stacked on the surface (back surface).

  Since the base material sheet 2 needs to transmit light, it is made of a synthetic resin that is transparent, in particular, colorless and transparent. The synthetic resin used for the base sheet 2 is not particularly limited, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weather resistant vinyl chloride and the like. . Although the thickness of the base material sheet 2 is not specifically limited, For example, about 10 micrometers-about 500 micrometers, Preferably, you may be about 35 micrometers-about 250 micrometers.

  That is, if the thickness of the base sheet 2 is less than the above range, curling tends to occur when the resin composition forming the light diffusion layer 3 is applied. If the thickness exceeds the above range, the luminance of the liquid crystal display device may decrease, and the thickness of the backlight unit increases to violate the demand for thinning the liquid crystal display device.

〔Apply〕
The present invention may be applied to either the anti-sticking layer side or the light diffusion layer side constituting the light diffusion sheet, but a great effect can be obtained by applying to the anti-sticking layer side. Moreover, when the layer of the application side consists of two or more, it is preferable to apply this invention to an outermost layer, and it becomes possible to acquire a printability improvement effect by this.

[Light diffusion layer]
The light diffusion layer 3 is composed of a binder 5 and beads 6 dispersed in the binder 5. As the aqueous resin (A) used for the binder 5, a water-soluble or water-dispersible polymer is preferably used, and a water-dispersible polymer is particularly preferably used among them. Specific examples are shown below.

[Acrylic latex]
A water-dispersible acrylic polymer can be used as the aqueous resin (A) of the present invention, and the water-dispersible acrylic polymer is an acrylic monomer alone or other monomer that can be copolymerized with an acrylic monomer and an acrylic monomer. (Hereinafter referred to as a comonomer). Examples of acrylic monomers include acrylic acid; methacrylic acid; acrylic acid esters such as alkyl acrylates (eg, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, phenylethyl acrylate, etc.), hydroxy-containing alkyl acrylate (eg, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc.); methacrylic acid ester, eg, alkyl methacrylate (eg, , Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, Sopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, phenylethyl methacrylate, etc.), hydroxy-containing alkyl methacrylate (for example, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, etc.); acrylamide; substituted acrylamide, such as N-methylacrylamide, N-methylolacrylamide, N, N-dimethylolacrylamide, N-methoxymethylacrylamide, etc .; methacrylamide; substituted methacrylamide, such as N-methyl Methacrylamide, N-methylol methacrylamide, N, N-dimethyl Methacrylamide, N-methoxymethyl methacrylamide, etc .; amino group-substituted alkyl acrylates such as N, N-diethylaminoethyl acrylate; amino group-substituted alkyl methacrylates such as N, N-diethylamino methacrylate; epoxy group-containing acrylates such as glycidyl acrylate Epoxy group-containing methacrylates such as glycidyl methacrylate; acrylic acid salts such as sodium salts, potassium salts and ammonium salts; methacrylic acid salts such as sodium salts, potassium salts and ammonium salts. The above-mentioned monomers can be used alone or in combination of two or more.

  Examples of comonomers include styrene and derivatives thereof; unsaturated dicarboxylic acids (eg, itaconic acid, maleic acid, fumaric acid); esters of unsaturated dicarboxylic acids (eg, methyl itaconate, dimethyl itaconate, methyl maleate, maleic acid) Dimethyl, methyl fumarate, dimethyl fumarate); salts of unsaturated dicarboxylic acids (for example, sodium salts, potassium salts, ammonium salts); monomers containing sulfonic acid groups or salts thereof (for example, styrene sulfonic acid, vinyl sulfonic acid) And salts thereof (sodium salt, potassium salt, ammonium salt)); acid anhydrides such as maleic anhydride and itaconic anhydride; vinyl isocyanate; allyl isocyanate; vinyl methyl ether; vinyl ethyl ether; The above-mentioned monomers can be used alone or in combination of two or more.

In the present invention, the difference between the glass transition temperature (Tg _L ) of the acrylic polymer latex showing the lowest glass transition temperature and the glass transition temperature (Tg _H ) of the acrylic polymer latex showing the highest glass transition temperature is 80 ° C. When exceeding, that is, when Tg _L is too low, the blocking resistance of the coating film is deteriorated, and when Tg _H is too high, the film forming property of the coating film is deteriorated. When the difference between Tg _L and Tg _H is less than 10 ° C., the effect of the polymer blend is lost.

  In the present invention, the glass transition temperature (Tg) is determined by the method described in “Polymer Handbook” pages III-139 to III-179 (1966, Wiley and Sun, Inc.) by Brandrup et al. The Tg (copolymer) of the copolymer can also be obtained by the following formula.

Tg (copolymer) in _{(° K) = v 1 Tg} 1 + v 2 Tg 2 + ··· + v n Tg n _{-type, v 1, v 2 ··· v} n represents the mass fraction of the monomers in the copolymer, Tg _1, Tg ₂ ··· Tg _n represents Tg (° K) of homopolymer obtained from the monomer in the copolymer. The accuracy of Tg calculated according to the above equation is ± 5 ° C.

[Polyester latex]
A water-dispersible polyester can be used as the aqueous resin (A) of the present invention, and the water-dispersible polyester can be obtained, for example, by condensation polymerization of polyvalent carboxylic acids and polyhydric alcohols.

  Examples of polycarboxylic acids include dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, diphenic acid and other aromatic dicarboxylic acids, p-oxy Aromatic oxycarboxylic acids such as benzoic acid, p- (hydroxyethoxy) benzoic acid, aromatic unsaturated polyvalent carboxylic acids such as phenylenediacrylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, etc. Aliphatic dicarboxylic acids, fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, hexahydrophthalic acid, tetrahydrophthalic acid, aliphatic unsaturated polycarboxylic acids, and cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid Acid, etc., and other polycarboxylic acids include trimellitic acid, Meshin acid, and the like trivalent or higher polycarboxylic acids such as pyromellitic acid can be exemplified.

  Examples of the polyhydric alcohols include aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, and aromatic polyhydric alcohols.

  Examples of the aliphatic polyhydric alcohols include ethylene glycol, propylene glycol, 1,3-propanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. , Aliphatic diols such as neopentyl glycol, dimethylol heptane, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, trimethylol ethane And triols and tetraols such as trimethylolpropane, glycerin, and pentaerythritol.

  Examples of the alicyclic polyhydric alcohols include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, spiroglycol, hydrogenated bisphenol A, ethylene oxide adduct and propylene oxide adduct of hydrogenated bisphenol A, tri Examples include cyclodecanediol and tricyclodecane dimethanol.

  Examples of the aromatic polyhydric alcohols include para-xylene glycol, meta-xylene glycol, ortho-xylene glycol, 1,4-phenylene glycol, 1,4-phenylene glycol ethylene oxide adduct, bisphenol A, and bisphenol A ethylene oxide addition. And propylene oxide adducts. Furthermore, examples of polyester polyols include lactone polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone.

  In the polyester resin used in the water-dispersible polyester of the present invention, a monofunctional monomer may be introduced into the polyester for the purpose of blocking a part of the polar group at the polyester polymer terminal.

  Examples of the monofunctional monomer include benzoic acid, chlorobenzoic acid, bromobenzoic acid, parahydroxybenzoic acid, sulfobenzoic acid monoammonium salt, sulfobenzoic acid monosodium salt, cyclohexylaminocarbonylbenzoic acid, and n-dodecylaminocarbonyl. Benzoic acid, tertiary butylbenzoic acid, naphthalenecarboxylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, salicylic acid, thiosalicylic acid, phenylacetic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, octanecarboxylic acid, lauric acid, Stearyl acid and monocarboxylic acids such as lower alkyl esters thereof, or monoalcohols such as aliphatic alcohols, aromatic alcohols, and alicyclic alcohols can be used.

  In the present invention, these polyester resins can be used alone or in combination of two or more. By using in combination, the compatibility with the aromatic hydrocarbon described later is improved, the emulsified state is improved, and the stability of the entire system is improved.

[Polyurethane latex]
A polyurethane emulsion can be used as the aqueous resin (A) of the present invention, and the polyurethane emulsion can be produced by a conventionally known method. For example, a urethane prepolymer containing substantially no organic solvent and having at least two isocyanate groups in one molecule and water are supplied to a specific emulsifier, and the urethane prepolymer is continuously added to water. After obtaining an emulsion of the urethane prepolymer having an average particle size of 0.1 to 2.5 μm by emulsification, the urethane prepolymer is obtained by a method of chain-extending the urethane prepolymer by continuously reacting with a chain extender. Specifically, it can be obtained according to the method described in JP-A-2004-2732.

  The number average molecular weight of the urethane prepolymer is preferably in the range of 1,000 to 20,000.

  The urethane prepolymer can be produced by a conventionally known method, for example, a method of reacting a polyisocyanate compound and an active hydrogen-containing compound, and 1) without using an organic solvent, which will be described later. A method of reacting a polyisocyanate compound with a polyol compound described later, 2) a method of removing a solvent after reacting a polyisocyanate compound described later with a polyol compound described below in an organic solvent, and a solvent removal step The former method is preferable in that it is unnecessary.

  The reaction is preferably performed at a temperature in the range of 20 to 120 ° C., more preferably in the range of 30 to 100 ° C., and an isocyanate group and an active hydrogen group in an equivalent ratio, preferably 1.1: 1 to 3: 1. More preferably, the polyisocyanate compound and the active hydrogen-containing compound are reacted at a ratio of 1.2: 1 to 2: 1.

  In this reaction, if necessary, an excess of isocyanate groups may be reacted with aminosilane or the like, and the terminal groups may be reactive groups other than isocyanate groups such as alkoxysilyl groups.

  Examples of the polyisocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 2,4′-diphenylmethane diisocyanate. 2,2′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate, 3,3′-dichloro-4,4 ′ -Biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene dii Cyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'- Examples include dicyclohexylmethane diisocyanate and 3,3′-dimethyl-4,4′-dicyclohexylmethane diisocyanate.

  As the active hydrogen-containing compound used for producing the urethane prepolymer, a relatively high molecular weight compound (hereinafter referred to as a high molecular weight compound) and a relatively low molecular weight compound (hereinafter referred to as a low molecular weight compound). Can be used.

  The number average molecular weight of the high molecular weight compound is preferably in the range of 300 to 10,000, more preferably in the range of 500 to 5,000. The number average molecular weight of the low molecular weight compound is less than 300.

  These active hydrogen-containing compounds may be used alone or in combination of two or more.

  Examples of the high molecular weight compound among the active hydrogen-containing compounds include polyester polyols, polyether polyols, polycarbonate polyols, polyacetal polyols, polyacrylate polyols, polyester amide polyols, polythioether polyols, polybutadiene-based polyolefin polyols, and the like. .

  As the polyester polyol, a polyester polyol obtained by subjecting the following glycol component and the following acid component to a dehydration condensation reaction can be used.

  Examples of the glycol component that can be used in obtaining the polyester polyol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl-1. , 5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (molecular weight 300 to 6,000), dipropylene glycol, tripropylene glycol, bishydroxyethoxybenzene 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, hydroquinone and their alkylene oxide adducts. It is.

  Examples of the acid component that can be used in obtaining the polyester polyol include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, and 1,3-cyclopentanedicarboxylic acid. Acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bis (phenoxy) ethane-p, p′-dicarboxylic acid and anhydrides or ester-forming derivatives of these dicarboxylic acids; p-hydroxybenzoic acid, p- (2-hydroxyethoxy) benzoic acid and their HI And ester-forming derivatives of loxycarboxylic acid. .

  In addition, polyesters obtained by ring-opening polymerization reaction of cyclic ester compounds such as ε-caprolactone and copolymerized polyesters thereof can also be used.

  Examples of the polyether polyol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, and glycerin. , Trimethylolethane, trimethylolpropane, sorbitol, sucrose, aconite sugar, trimellitic acid, hemimellitic acid, phosphoric acid, ethylenediamine, diethylenetriamine, triisopropanolamine, pyrogallol, dihydroxybenzoic acid, hydroxyphthalic acid, 1,2,3 -1 type, or 2 or more types of compounds which have at least 2 active hydrogen atoms, such as propane trithiol, for example, ethylene oxide, propylene oxide, butylene Kisaido, styrene oxide, epichlorohydrin, tetrahydrofuran, one or compounds by a conventional method was addition-polymerized to a more, such as cyclohexylene and the like.

  Examples of the polycarbonate polyol include compounds obtained by reacting glycols such as 1,4-butanediol, 1,6-hexanediol, diethylene glycol and the like with diphenyl carbonate and phosgene.

  Among the active hydrogen-containing compounds, the low molecular weight compound is a compound having at least two or more active hydrogens in the molecule and having a number average molecular weight of less than 300, for example, a glycol component used as a raw material for the polyester polyol; glycerin, Polyhydroxy compounds such as trimethylolethane, trimethylolpropane, sorbitol, pentaerythritol; ethylenediamine, 1,6-hexamethylenediamine, piperazine, 2,5-dimethylpiperazine, isophoronediamine, 4,4'-dicyclohexylmethanediamine, 3 , 3'-dimethyl-4,4'-dicyclohexylmethanediamine, 1,4-cyclohexanediamine, 1,2-propanediamine, hydrazine, diethylenetriamine, triethylenetetramine, and other amine compounds. It is below.

  In order to introduce a hydrophilic group into the urethane prepolymer, for example, as an active hydrogen-containing compound, a compound having at least one active hydrogen atom in the molecule and containing the hydrophilic group is used as a raw material. May be used.

Examples of the compound having at least one active hydrogen atom in the molecule and having the above hydrophilic group include 2-oxyethanesulfonic acid, phenolsulfonic acid, sulfobenzoic acid, sulfosuccinic acid, 5- Sulfoisophthalic acid, sulfanilic acid, 1,3-phenylenediamine-4,6-disulfonic acid, sulfonic acid group-containing compounds such as 2,4-diaminotoluene-5-sulfonic acid and their derivatives or copolymers thereof The resulting polyester polyol;
Carboxylic acid-containing compounds such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dioxymaleic acid, 2,6-dioxybenzoic acid, 3,4-diaminobenzoic acid And their derivatives or polyester polyols obtained by copolymerization thereof;
Tertiary amino group-containing compounds such as methyldiethanolamine, butyldiethanolamine, alkyldiisopropanolamine, and derivatives thereof, or polyester polyols or polyether polyols obtained by copolymerization thereof;
Polyester polyol or polyether polyol obtained by copolymerizing the tertiary amino group-containing compound and derivatives thereof, and methyl chloride, methyl bromide, dimethyl sulfate, diethyl sulfate, benzyl chloride, benzyl bromide, ethylene A reaction product of a quaternizing agent such as chlorohydrin, ethylene bromohydrin, epichlorohydrin, bromobutane;
A polyoxyethylene glycol or polyoxyethylene-polyoxypropylene copolymer glycol having a molecular weight of 300 to 20,000, containing at least 30% by mass of repeating units of ethylene oxide and containing at least one active hydrogen in the polymer, Nonionic group-containing compounds such as polyoxyethylene-polyoxybutylene copolymer glycol, polyoxyethylene-polyoxyalkylene copolymer glycol, or monoalkyl ethers thereof, or polyester polyether polyols obtained by copolymerization thereof may be mentioned. .

  These can be used alone or in combination of two or more.

  The water used for the polyurethane emulsion does not need to contain an emulsifier particularly when the urethane prepolymer has a hydrophilic group in the molecule, but when the urethane prepolymer does not have a hydrophilic group, In order to improve the storage stability of the polyurethane emulsion, it is necessary to contain an emulsifier.

Examples of such emulsifiers include nonionic emulsifiers such as polyoxyethylene-polyoxypropylene copolymers, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene sorbitol tetraoleate, and the like. ;
Anionic emulsifiers such as fatty acid salts such as sodium oleate, alkyl sulfate esters, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, alkane sulfonate sodium salts, sodium alkyl diphenyl ether sulfonates;
Nonionic anionic emulsifiers such as polyoxyethylene alkyl sulfate and polyoxyethylene alkyl phenyl sulfate are listed.

  As the usage-amount of an emulsifier, the range of 0.1-15 mass parts is preferable with respect to 100 mass parts of urethane prepolymers, More preferably, it is the range of 1-10 mass parts.

  The urethane prepolymer is liquid at normal temperature, has high viscosity at normal temperature, or is solid and has a viscosity of 200 to 10,000 mPa · s at a temperature equal to or higher than the melting point. This is preferable from the viewpoint of easy application of high shearing force and emulsification.

  In the method for producing the polyurethane emulsion, an aqueous dispersion, a stabilizer and the like can be added to water as necessary. Examples of the aqueous dispersion include emulsions such as vinyl acetate, ethylene vinyl acetate, acrylic, and acrylic styrene; latexes such as styrene / butadiene, acrylonitrile / butadiene, and acrylic / butadiene; polyethylene, polyolefin And various aqueous dispersions such as polyurethane, polyester, polyamide, and epoxy resin.

  When the present invention is not applied to the light diffusion layer, it is not always necessary to use an aqueous coating solution, and an organic solvent solution of the above polymer may be used.

[Sticking prevention layer binder]
As the binder 7 used for the anti-sticking layer, various resins of the aqueous resin (A) used for the light diffusion layer can be used.

(Application layer of the present invention)
The layer to which the present invention is applied particularly preferably contains at least one of an aqueous polyester resin, an aqueous resin containing a hydroxyl group, and an aqueous resin containing a carboxyl group as the aqueous resin (A).

  In the case of water-based polyester resins, active sites such as hydroxyl groups and carboxyl groups may be introduced into the molecular chain, but the ester bond site undergoes a reversible reaction at high temperatures without any particular introduction, so that a crosslinking reaction can take place at any location. As a result, a dense film is obtained.

  When other resins are used, a dense film can be obtained by introducing a crosslinkable functional group such as a hydroxyl group or a carboxyl group into the molecular chain.

[Crosslinking agent used in the application layer of the present invention]
In the application layer of the present invention, at least one selected from a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, a water-soluble zirconium chelate compound, and a water-soluble zirconium acylate compound as a crosslinking agent (B ) Is used. The above water-soluble means to dissolve in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

  Examples of water-soluble titanium chelate compounds include diisopropoxybis (acetylacetonato) titanium, isopropoxy (2-ethyl-1,3-hexanediolato) titanium, diisopropoxybis (triethanolaminato) titanium, di -N-butoxybis (triethanolaminato) titanium, hydroxybis (lactato) titanium, ammonium salt of hydroxybis (lactato) titanium, titanium beloxocitrate ammonium salt and the like.

  Examples of the water-soluble titanium acylate compound include oxotitanium bis (monoammonium oxalate), and examples of the water-soluble zirconium compound include zirconium tetraacetylacetonate and zirconium acetate.

[Crosslinking agent and functional group]
Other cross-linking agents can be used for the layers to which the present invention is not applied. Although the combination of the crosslinking agent applicable as a thermal crosslinking agent and the functional group capable of crosslinking reaction with the crosslinking agent is not limited to the following, for example, the following combinations may be mentioned.

  For cross-linking agents using isocyanate groups and blocked isocyanate groups as reactive groups of the cross-linking agent, hydroxyl groups, amino groups, carboxyl groups, mercapto groups, etc., for cross-linking agents using epoxy groups as reactive groups Carboxyl groups, amino groups, mercapto groups, etc., carboxyl groups are used for cross-linking agents using oxazoline groups or polyvalent metal ions, and carboxyl groups, glycidyl groups, etc. are used for ethyleneimine-based cross-linking agents. . In addition, a combination of crosslinking a melamine compound crosslinking agent and a hydroxyl group can be used.

  Further, the crosslinking agent applicable to photocrosslinking that is another crosslinking treatment and its functional group are not limited to these, but a compound having an ethylenically unsaturated double bond capable of radical polymerization, and acryloyl as a specific functional group. A compound having a group or a methacryloyl group can be used.

[Minimum film forming temperature]
When a water-dispersible polymer is used for the binder of the present invention, the minimum film-forming temperature (MFT) is preferably 90 ° C. or lower. The minimum film-forming temperature refers to the minimum film-forming temperature when a water-dispersible polymer emulsion used as a binder is formed alone. The minimum film-forming temperature can be measured with a known measuring apparatus, for example, a minimum film-forming temperature measuring apparatus (SKLH-1, manufactured by Shimakawa Seisakusho).

  When the minimum film-forming temperature is higher than 90 ° C., the dispersed polymer particles are not sufficiently fused in the coating / drying process, and it becomes difficult to obtain the intended effect.

  However, this is not the case when a crosslinking agent is used and a functional group capable of crosslinking reaction with the crosslinking agent is contained in the water-dispersible particles according to the combination.

[Dimethylsiloxane structural unit]
In the present invention, it is preferable to use a compound having a dimethylsiloxane structural unit. The compound having a dimethylsiloxane structural unit refers to a compound having a structural unit represented by the following general formula (1) in the molecule.

In the formula, n is an integer of 1 or more, m is 0 or an integer of 1 or more, and X, Y, and Z are not particularly limited as long as they are atoms or atomic groups capable of forming a covalent bond. As methyl group, hydroxyl group, HOOC—CH ₂ —, CH ₃ O (CH ₂ CH ₂ O) _n CH ₂ —, CH ₃ O (CH ₂ CH (CH ₃ ) O) _n CH ₂ —, NH ₂ —CH _{2 -, HO (CH 2 CH} 2 O) n CH 2 -, HO (CH 2 CH (CH 3) O) n CH 2 -,

Etc., and examples of _{Y, -H, -Si (CH 3} ) 3, -Si (CH 3) 2 CH 2 O (CH 2 CH 2 O) n CH 3, -Si (CH 3) 2 CH 2 _{O (CH 2 CH (CH 3} ) O) n CH 3, -Si (CH 3) 2 CH 2 O (CH 2 CH 2 O) n H, -Si (CH 3) 2 CH 2 O (CH 2 CH ( _{CH 3) O) n H,} -Si (CH 3) 2 -CH 2 -COOH, -Si (CH 3) 2 -CH 2 -NH 2,

Etc. As Z, an alkyl group, an aralkyl group, an alkoxy group, —CH ₂ — (CH ₂ ) ₂ —CF ₃ , a phenyl group, —CH ₂ O (CH ₂ CH ₂ O) _n CH ₃ , —CH _{2 O (CH 2 CH (CH 3} ) O) n -CH 3, -CH 2 O (CH 2 CH 2 O) n H, -CH 2 O (CH 2 CH (CH 3) O) n H, -CH 2 _{-COOH, -CH 2 -NH 2, -CH} 2 -NHCO-CH 2 - (CH 2 CH 2 O) n -CH 3,

  Etc.

  When mixed with a water-soluble or water-dispersible polymer and used as a part of a binder, a composite that has a high affinity with a binder such as acrylic and has a film-forming property connected to any part of X, Y, or Z It is preferable to use a polymer.

  When mixed with a water-soluble or water-dispersible polymer and used as a non-film-forming additive, it is preferable to use a polyether-modified dimethylsiloxane compound such as polyoxyethylene or polyoxypropylene.

[Light diffusing agent (beads)]
The light diffusion layer includes a binder and a light diffusing agent contained in the binder. Thus, by containing a light-diffusion agent in a light-diffusion layer, the light ray which permeate | transmits a light-diffusion layer from the back side to the front side can be spread | diffused uniformly. Further, fine irregularities are formed substantially uniformly on the surface of the light diffusion layer by the light diffusing agent. Thus, the light can be diffused better by the lens-like refracting action of fine irregularities formed on the surface of the light diffusion sheet.

  A light diffusing agent is a particle having a property of diffusing light, and is roughly classified into an inorganic filler and an organic filler. Specifically, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof can be used as the inorganic filler. Specific examples of the organic filler include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide, and the like. Among them, an acrylic resin having high transparency is preferable, and polymethyl methacrylate (PMMA) is particularly preferable.

  The shape of the light diffusing agent is not particularly limited, and examples thereof include a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scale shape, and a fiber shape. Beads are preferred.

  The lower limit of the average particle diameter of the light diffusing agent is preferably 1 μm, particularly 2 μm, and more preferably 5 μm, and the upper limit of the average particle diameter of the light diffusing agent is preferably 50 μm, particularly 20 μm, and more preferably 15 μm. This is because if the average particle size of the light diffusing agent is less than the above range, the unevenness of the surface of the light diffusing layer formed by the light diffusing agent becomes small, and the light diffusing property necessary for the light diffusing sheet may not be satisfied. Conversely, if the average particle diameter of the light diffusing agent exceeds the above range, the thickness of the light diffusing sheet increases and uniform diffusion becomes difficult.

  The lower limit of the blending amount of the light diffusing agent (the blending amount in terms of solid content with respect to 100 parts of the base polymer in the polymer composition as the binder forming material) is preferably 10 parts, particularly 20 parts, and more preferably 50 parts. The upper limit of the amount is preferably 500 parts, particularly 300 parts, and more preferably 200 parts. If the blending amount of the light diffusing agent is less than the above range, the light diffusing property becomes insufficient. On the other hand, if the blending amount of the light diffusing agent exceeds the above range, the effect of fixing the light diffusing agent is obtained. It is because it falls. In the case of a so-called upward light diffusion sheet disposed on the surface side of the prism sheet, high light diffusibility is not required, so the amount of the light diffusing agent is 10 parts or more and 40 parts or less, particularly 10 parts or more. 30 parts or less are preferable.

[Matting agent for anti-sticking layer]
In order to prevent the sticking prevention layer from sticking to the light guide plate, it is preferable to use a matting agent protruding from the sticking prevention layer. As the matting agent, the same one as the light diffusing agent can be used. The shape is preferably substantially spherical from the viewpoint of influence on optical performance and prevention of damage to the contact member, and the average particle size is preferably 0.3 to 10 μm.

[Coating method]
The anti-sticking layer and the light diffusion layer of the present invention can be formed by coating and drying using a generally well-known coating method.

  Examples of the coating method that can be used include a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, or a hopper described in US Pat. No. 2,681,294. Extrusion coating method using If necessary, U.S. Pat. Nos. 2,761,791, 3,508,947, 2,941,898 and 3,526,528, Yuji Harasaki, “Coating Engineering”, page 253 ( A method of simultaneously applying two or more layers described in 1973, published by Asakura Shoten) can also be used.

[Pretreatment / Primer]
Prior to application of the coating solution of the present invention, a primer layer can be provided on the substrate as required.

  In the case where the primer layer is provided or not, in the case where the primer layer is not provided, when a PET film is used as the substrate, it is preferable to perform a pretreatment. Pre-treatment includes so-called etching solvent (for example, phenol, cresol, resorcin, chloral hydrate, chlorophenol, etc.) treatment, mechanical treatment, corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow There are surface activation treatments such as discharge treatment, active plasma treatment, laser treatment, mixed acid treatment, and ozone treatment. When providing a primer layer in a PET film, it can be provided before or after stretching during film formation of the PET film.

[Film thickness (mass after drying)]
The anti-sticking layer of the present invention is preferably in the range of 0.1 to 10 g / m ^{2 by} weight after drying, and in the case of applying the present invention to the anti-sticking layer, it is in the range of 0.1 to 3 g / m ^2. More preferably. The light diffusion layer is preferably in the range of 1 to 50 g / m ^{2 by} mass after drying.

〔Additive〕
If necessary, a surfactant, an antistatic agent, a chromaticity adjusting dye, a chromaticity adjusting pigment, a pH adjusting agent, a preservative, and the like may be added to the antisticking layer and the light diffusion layer.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example. Unless otherwise specified, “part” in the examples represents “part by mass”, and% represents mass%.

[Comparative Example 1]
Preparation of comparative sample:
(Light diffusion layer)
100 parts of a binder resin compound comprising a polyester polyol having a cycloalkyl group as a base polymer, 50 parts of colloidal silica (“PL-1” from Fuso Chemical Industry Co., Ltd.) having an average particle diameter of 20 nm, and a curing agent (Nippon Polyurethane) 50 parts of acrylic resin beads (“MBX-15” of Sekisui Plastics Co., Ltd.) having an average particle size of 15 μm are mixed and coated in a polymer composition containing 5 parts of “Coronate HX” of Co., Ltd. to prepare a coating liquid, surface 15 g / m ² (solid basis of transparent polyester base layer having a thickness of 100μm by the roll coating method the coating liquid ( "a-4300" of Toyobo Co.) ) Coated and cured.

(Anti-sticking layer)
Water-dispersible hydroxyl group-containing acrylic / styrene resin (Bernock WE-306, Dainippon Ink Co., Ltd., MFT = 50 ° C., Tg = 50 ° C., hydroxyl value = 100), 100 parts of water-dispersible polyisocyanate (Dai Nippon Ink 15 parts of Vernock DN-5010), 50 parts of colloidal silica having an average particle size of 20 nm (“PL-1” of Fuso Chemical Industry Co., Ltd.), spherical silica particles having an average particle size of 0.5 μm (Nippon Catalyst ( "KE-P50") 10 parts was mixed to prepare a coating solution, and this coating solution was applied to the back surface of the base material layer by a roll coating method at a rate of 0.45 g / m ² (solid content conversion). The light diffusing sheet having the anti-sticking layer laminated thereon was obtained by heating, drying and thermosetting.

  Coating, drying, and thermal curing were continuously performed until winding, and thermal curing was performed by passing through a heat treatment zone at 140 ° C. for 3 minutes by folding conveyance with a contact roll.

  The light diffusing sheet was prepared for the 1 h coating solution after preparation of the sticking layer coating solution, the coating solution after 8 hours, and the coating solution after 16 hours, respectively, to obtain light diffusing sheets -1a, -1b, and -1c, respectively.

[Example 1]
Preparation of the sample of the present invention:
15 parts of water-dispersible polyisocyanate (Bernock DNW-5010 from Dainippon Ink Co., Ltd.) in the anti-sticking layer of Comparative Example 1 was replaced with 18 parts of hydroxybis (lactato) titanium (“TC310” from Matsumoto Pharmaceutical Co., Ltd.). A light diffusing sheet was produced in the same manner as in Comparative Example 1 except for the above.

  The thermosetting was performed in a roll state wound after coating and drying, and the thermosetting was performed by putting in a temperature control chamber at 50 ° C. for 36 hours.

  In addition, also about the above, the light-diffusion sheet | seat was produced about each coating liquid of 1h, 8h, and 16h after preparation of a coating liquid like the comparative example 1, and it was set as light-diffusion sheet-2a, -2b, -2c.

[Example 2]
A light diffusion sheet was produced in the same manner as in Comparative Example 1 except that the sticking prevention layer of Comparative Example 1 was changed to the following.

(Anti-sticking layer)
96 parts of water-dispersible hydroxyl group-containing acrylic / styrene resin (Bernock WE-306 from Dainippon Ink, MFT = 50 ° C., Tg = 50 ° C., hydroxyl value = 100), silicone / acrylic composite resin dispersion (Nissin) 4 parts of Charine FE-230N from Chemical Co., 18 parts of hydroxybis (lactato) titanium ("TC310" from Matsumoto Pharmaceutical Co., Ltd.), colloidal silica with an average particle size of 20 nm PL-1 ") 50 parts, 10 parts of spherical silica particles (" KE-P50 "from Nippon Shokubai Co., Ltd.) with an average particle size of 0.5 μm are mixed to prepare a coating liquid, and this coating liquid is rolled. A light diffusion sheet having a sticking prevention layer laminated thereon was obtained by coating, drying, and thermosetting 0.45 g / m ² (solid content conversion) on the back surface of the base material layer by a coating method.

  The thermosetting was performed in a roll state wound after coating and drying, and the thermosetting was performed by putting in a temperature control chamber at 50 ° C. for 36 hours.

  In addition, also about the above, the light-diffusion sheet was produced about each coating liquid of 1h, 8h, and 16h after preparation of a coating liquid like the comparative example 1, and it was set as light-diffusion sheet-3a, -3b, -3c.

[Comparative Example 2]
A light diffusion sheet was produced in the same manner as in Comparative Example 1 except that the sticking prevention layer of Comparative Example 1 was changed to the following.

(Anti-sticking layer)
Water-dispersible carboxyl group-containing urethane resin (Dai Nippon Ink Co., Ltd. Hydran AP-40N, MFT = 33 ° C., Tg = 50 ° C.) 100 parts, Water dispersible polyisocyanate (Dai Nippon Ink Co., Ltd. Bernock DN- 5010) 15 parts, 50 parts of colloidal silica having an average particle size of 20 nm (“PL-1” from Fuso Chemical Industries), spherical silica particles having an average particle size of 0.5 μm (“KE-” of Nippon Shokubai Co., Ltd.) P50 ") 10 parts are mixed to prepare a coating solution, and this coating solution is applied to the back surface of the base material layer by a roll coating method at 0.45 g / m ² (in terms of solid content), dried and thermally cured. As a result, a light diffusion sheet having a sticking prevention layer laminated thereon was obtained.

  In addition, also about the above, the light-diffusion sheet was produced about each coating liquid of 1h, 8h, and 16h after preparation of a coating liquid like the comparative example 1, and it was set as light-diffusion sheet -4a, -4b, -4c.

[Example 3]
15 parts of water dispersible polyisocyanate (Bernock DNW-5010 from Dainippon Ink, Inc.) in the anti-sticking layer of Comparative Example 2 was replaced with 18 parts of hydroxybis (lactato) titanium ("TC310" from Matsumoto Pharmaceutical Co., Ltd.). A light diffusing sheet was produced in the same manner as in Comparative Example 2 except for the above.

  The thermosetting was performed in a roll state wound after coating and drying, and the thermosetting was performed by putting in a temperature control chamber at 50 ° C. for 36 hours.

  In addition, also about the above, the light-diffusion sheet was produced about each coating liquid of 1h, 8h, and 16h after preparation of a coating liquid like the comparative example 1, and it was set as light-diffusion sheet -5a, -5b, -5c.

<Evaluation>
(Evaluation of solvent resistance)
One drop of methyl ethyl ketone was dropped on the film surface, and after 10 seconds, wiped with a cloth to evaluate the presence or absence of a drop mark. The evaluation criteria were “A” where no trace of dripping was observed, “B” where microscopic recognition was observed, and “C” where it was clearly recognized.

(Scratch resistance evaluation)
The evaluation was performed by applying a load of 200 g / cm ² and rubbing the light diffusion layer and the anti-sticking layer 10 times at a speed of 20 mm / sec to evaluate the presence or absence of scratches generated in the sticking layer. The evaluation criteria were ◎ for those in which no scratches or shape changes were observed, ◯ for those in which minute scratches were recognized, and × for those in which scratches or shape changes were clearly recognized.

(Evaluation of printability)
As an evaluation of shading frame printability, 10 parts of a curing agent (SSUR100B of Toyo Ink Co., Ltd.) and a diluent solvent (100 Toyo Ink Co., Ltd. SS16-911 black) are added to each light diffusion sheet. A printing ink added and mixed with 10 parts of Toyo Ink Co., Ltd. S-799) was printed by screen printing, dried in an oven at 80 ° C. for 2 minutes, and left in an environment of 60 ° C. and 90% for 1000 hours. The ink film peeling resistance was evaluated.

  Judgment criteria for the evaluation are adhesive tapes, where peeling is not recognized as to whether or not peeling occurs, △ when peeling is partially recognized, 50% or more peeling or printing can be performed normally The thing which does not exist was set as x.

  The above results are shown together in Table 1.

  As shown in the table, in the light diffusion sheet of the embodiment of the present invention, after the preparation of the coating solution, there is no deterioration of the coating film performance even after a long time, and a light diffusion sheet excellent in scratch resistance and printability is obtained. I can do it.

  Thereby, after preparing a coating liquid in a large-capacity tank, it becomes possible to produce continuously for a long time, and it becomes possible to improve productivity. Moreover, even when the light diffusing sheet is incorporated in the backlight unit, it is possible to prevent deterioration of optical characteristics such as hindering the transmission of light accompanying damage to the anti-sticking layer, and maintain desired optical characteristics. It becomes possible to obtain a high-quality backlight unit that does not cause problems due to poor adhesion of the printed film even after many years of use.

Schematic sectional view showing a light diffusing sheet according to an embodiment of the present invention. Schematic perspective view showing a general backlight unit

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light diffusion sheet 2 Base material layer 3 Light diffusion layer 4 Sticking prevention layer 5 Binder 6 Light diffusion particle 7 Binder 8 Light diffusion particle 20 Backlight unit 21 Lamp 22 Light guide plate 23 Light diffusion sheet 24 Prism sheet 24a Prism part

Claims (4)

A light diffusing sheet comprising a light diffusing layer containing a light diffusing agent in a binder, a transparent substrate and an anti-sticking layer in this order, wherein the anti-sticking layer or the light diffusing layer comprises an aqueous resin (A), a water-soluble resin An aqueous coating solution containing at least one selected from a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, a water-soluble zirconium chelate compound, and a water-soluble zirconium acylate compound, and dried. A light diffusion sheet comprising a layer. The aqueous resin (A) and at least one selected from a water-soluble titanium chelate compound, a water-soluble titanium acylate compound, a water-soluble zirconium chelate compound, and a water-soluble zirconium acylate compound (B) The light diffusing sheet according to claim 1, wherein a layer obtained by applying and drying the aqueous coating liquid containing is the outermost layer. 3. The light diffusion sheet according to claim 1, wherein the aqueous resin (A) contains at least one of an aqueous polyester resin, an aqueous resin containing a hydroxyl group, and an aqueous resin containing a carboxyl group. The light diffusion plate according to any one of claims 1 to 3, wherein the lamp, a light guide plate that is disposed on a side of the lamp and guides light emitted from the lamp in a front side direction, and is disposed on the front side of the light guide plate. A backlight unit for a liquid crystal display device comprising a sheet.

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