WO2008032505A1

WO2008032505A1 - Light-diffusing sheet and backlight unit employing the same for liquid-crystal display

Info

Publication number: WO2008032505A1
Application number: PCT/JP2007/065268
Authority: WO
Inventors: Tetsuya Taniguchi
Original assignee: Konica Minolta Medical & Graphic, Inc.
Priority date: 2006-09-15
Filing date: 2007-08-03
Publication date: 2008-03-20
Also published as: JPWO2008032505A1

Abstract

A light-diffusing sheet which comprises a light-diffusing layer comprising a binder containing a light diffuser, a base sheet, and a binder-containing sticking-preventing layer in this order. It is characterized in that the sticking-preventing layer binder is a polymer (polymer B) obtained by applying to the base sheet an aqueous emulsion which contains particles of a polymer (polymer A) having, as a constituent monomer unit, a monomer unit having a functional group capable of undergoing a crosslinking reaction with a crosslinking agent and further contains a crosslinking agent reactive with the functional group and drying the emulsion. Even when two or more light-diffusing sheets having this constitution are superposed during transportation, storage, etc. after production, the backside of each light-diffusing sheet can be prevented from being marred. A production loss can be reduced. The amount of an organic solvent to be discharged into the air during light-diffusing sheet production can be significantly reduced to improve environmental friendliness during production.

Description

Specification

LIGHT DIFFUSING SHEET AND BACKLIGHT UNIT FOR LIQUID CRYSTAL DISPLAY HAVING THE SAME Technical Field

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 this light diffusion sheet.

Background art

In a 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. In general, as shown in FIG. 2, the backlight unit 20 having a force includes a rod-shaped lamp 21 as a light source, a rectangular plate-shaped light guide plate 22 arranged so that the end of the lamp 21 extends, and A light diffusion sheet 23 disposed on the surface side of the light guide plate 22 and a prism sheet 24 disposed on the surface side of the light diffusion sheet 23 are provided.

[0003] 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. The light is emitted from the surface of the light guide plate 22. 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. Reference can be made to Patent Document 1 or Patent Document 2 for the structure of the light diffusion sheet.

[0004] Thereafter, the light emitted from the light diffusion sheet 23 enters the prism sheet 24, and is emitted as a distribution light having a peak in a substantially upward direction by the prism portion 24a formed on the surface of the prism sheet 24. Is done. In this way, the light beam emitted from the lamp 21 is diffused by the light diffusion sheet 23 and refracted by the prism sheet 24 so as to show a peak in the substantially upward direction. The entire surface is illuminated.

Although not shown, 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 is also included in consideration of the light condensing characteristics of the prism sheet 24 described above.

[0006] The sticking prevention layer and the light diffusion layer are usually formed by applying and drying on a support in a form dissolved by an organic solvent, but sufficient strength can be obtained only with the binder component. Therefore, it is usually used by cross-linking and curing between molecules with a cross-linking agent. However, curing does not progress sufficiently immediately after coating and drying, and it contains a considerable amount of residual solvent.Therefore, it is rubbed and scratched by the back surface due to vibration during transportation until curing is completed by (heating) curing. Or the shape of the light diffusing sheet may be damaged. Therefore, careful handling was necessary while paying great attention to the handling.

Patent Document 1: Japanese Patent Laid-Open No. 7-5305

Patent Document 2: Japanese Patent Laid-Open No. 2000-89007

Disclosure of the invention

Problems to be solved by the invention

[0007] An object of the present invention is to reduce optical characteristics such as a decrease in light transmittance that does not cause scratches or shape changes on the surface of the layer even when vibration is applied during transportation immediately after coating and drying of the anti-sticking layer. An object of the present invention is to provide a light diffusion sheet that can prevent and maintain desired optical characteristics.

[0008] In addition, the amount of organic solvent discharged into the atmosphere during production can be reduced to zero or greatly reduced, and environmental suitability can be greatly improved.

Means for solving the problem

[0009] The above object of the present invention is achieved by the following constitution.

1. A light diffusing sheet comprising a light diffusing layer containing a binder containing a light diffusing agent, a base sheet, and an anti-sticking layer containing a binder in this order, wherein the anti-sticking layer binder comprises A polymer (polymer A) particle containing a monomer unit having a functional group capable of undergoing a crosslinking reaction with a crosslinking agent as a monomer unit and an aqueous emulsion containing a crosslinking agent capable of reacting with the functional group are coated on the base sheet. And a light-diffusing sheet characterized by being a polymer (polymer B) obtained by drying.

2. The polymer containing a monomer unit having a functional group capable of undergoing a crosslinking reaction with a crosslinking agent as the constituent monomer unit is at least one of acrylic polymer, polyester, and polyurethane. Light diffusion sheet.

3. The functional group force S is a functional group capable of reacting with an isocyanato group or a glycidyl group. The light diffusing sheet according to 1 or 2, characterized in.

4. The minimum film-forming temperature of the polymer (polymer A) containing a monomer unit having a functional group capable of crosslinking reaction with a crosslinking agent as the constituent monomer unit is 90 ° C or lower; The light diffusion sheet according to any one of the above.

5. The light diffusing sheet according to any one of! To 4, wherein the light diffusing agent is spherical.

6. A lamp, a light guide plate that is disposed on the side of the lamp and guides light emitted from the lamp in a front direction, and is disposed on the front side of the light guide plate; the light according to any one of! To 5 A backlight unit for a liquid crystal display device, comprising a diffusion sheet.

The invention's effect

[0010] Thus, according to the light diffusion sheet of the present invention, even when a plurality of light diffusion sheets are stacked during transportation, storage, etc. after manufacturing the light diffusion sheet, the back surface of the light diffusion sheet (anti-stucking) Can be prevented from occurring and can be easily handled, and not only the light diffusion sheet of the present invention can be easily attached to the backlight unit, but also during production. Since it is possible to greatly reduce the scratches that occur during transportation, it is possible to reduce manufacturing losses. In addition, since it is possible to manufacture with a water-based coating liquid instead of the conventional organic solvent system, the organic solvent discharged into the atmosphere can be reduced to zero or greatly reduced, and environmental suitability is improved. In addition, the health and safety aptitude of manufacturing workers will be improved.

In addition, according to the light diffusing sheet of the present invention, since the generation of scratches on the anti-sticking layer is prevented, optical properties such as the transmission of light accompanying the scratches on the anti-sticking layer being hindered. Deterioration can be prevented and required optical characteristics can be maintained.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view showing a light diffusion sheet according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a general backlight unit.

Explanation of symbols

[0013] 1 Light diffusion sheet

2 Base sheet 3 Light diffusion layer

4 State-king prevention layer

5 Binder

6 Light diffusing particles

7 Binder

8 Light diffusing particles

20 Backlight unit

21 Lamp

22 Light guide plate

23 Light diffusion sheet

24 Prism sheet

24a Prism section

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] The following is a detailed description of the best mode for carrying out the present invention. The present invention is not limited to these.

[0015] The present invention is a light diffusing sheet comprising a light diffusing layer containing a binder containing a light diffusing agent, a base sheet, and a sticking preventing layer containing a binder in this order. A polymer of the polymer (polymer A) in which the binder of the prevention layer contains a monomer unit having a functional group capable of undergoing a crosslinking reaction with a crosslinking agent as a constituent monomer unit, and an aqueous emulsion containing a crosslinking agent capable of reacting with the functional group, It is a polymer (polymer B) obtained by coating on the substrate sheet and drying.

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

Referring to FIG. 1, generally, the light diffusion sheet 1 of the present invention includes a base sheet 2 and a base sheet.

2 is composed of a light diffusion layer 3 laminated on one surface (front surface) 2 and a sticking prevention layer 4 laminated on the other surface (back surface) of the substrate sheet 2.

[0018] The substrate sheet 2 is formed of a synthetic resin that is transparent, in particular, colorless and transparent since it is necessary to transmit light. The synthetic resin used for the base material sheet 2 is not particularly limited. For example, polyethylene terephthalate, polyethylene naphthalate, Examples include acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, and weather-resistant butyl chloride.

[0019] The thickness of the base sheet 2 is not particularly limited.

From the viewpoint of thinning the liquid crystal display device, 10 111 to 500 111 are preferable, particularly 35 111

It is preferred to be ~ 250 μm! / ヽ.

The light diffusing layer 3 is composed of a binder 5 and light diffusing particles (beads) 6 which are light diffusing agents dispersed in the binder 5. Binder 5 consists of polymer B.

[0021] In the present invention, the binder of the anti-sticking layer or the light diffusing layer is obtained by applying and drying an aqueous emulsion, which is a resin composition containing the polymer A and a crosslinking agent, in the form of a base sheet. The resulting polymer (Polymer B).

[0022] The aqueous emulsion according to the present invention is a resin composition containing solid particles of polymer A dispersed in water as a solvent and a crosslinking agent.

[Crosslinking agent and functional group]

Examples of the crosslinking agent according to the present invention include an isocyanato group, a compound having a blocked isocyanato group, a compound having an epoxy group, a compound having an oxazoline group, a polyvalent metal ion, and a melamine compound.

The combination of the crosslinking agent used in the present invention and the functional group capable of crosslinking reaction with the crosslinking agent is not limited to the following, but examples thereof include the following combinations.

[0024] When the crosslinking agent is an isocyanato group or a compound having a blocked isocyanato group, examples of the functional group capable of undergoing a crosslinking reaction with the crosslinking agent include a hydroxyl group, an amino group, a carboxyl group, a mercapto group, and the like. Is mentioned.

[0025] When the crosslinking agent is a compound having an epoxy group, examples of the functional group capable of undergoing a crosslinking reaction with the crosslinking agent include a carboxyl group, an amino group, and a mercapto group.

[0026] When the cross-linking agent is a cross-linking agent using an oxazoline group or a polyvalent metal ion, a carboxyl group is used as a functional group capable of undergoing a cross-linking reaction with the cross-linking agent.

[0027] When the crosslinking agent is a melamine compound, a hydroxyl group is used as a functional group capable of undergoing a crosslinking reaction with the crosslinking agent.

Examples of the polymer A contained in the aqueous emulsion include acrylic polymers, polyesters, Polyurethane is preferably used.

[0028] These polymers have the above-described functional groups capable of reacting with a crosslinking agent. That is, these polymers include monomer units having functional groups capable of reacting with a crosslinking agent as constituent units.

[0029] Polymer A is synthesized by using a monomer having a functional group capable of reacting with a crosslinking agent as a monomer used in the synthesis, or by modifying the monomer so as to have the functional group after synthesis. The

[Acrylic polymer]

The acrylic polymer is a homopolymer or copolymer of (meth) acrylic acid or (meth) acrylic acid ester, and can be copolymerized with an acrylic monomer alone or with an acrylic monomer and an acrylate monomer. Manufacture using other monomers (hereinafter referred to as comonomer).

Acrylic monomers include, for example, acrylic acid; methacrylic acid; acrylic acid esters such as alkyl acrylate (eg, methyl acrylate, ethyl acrylate, n propylene acrylate, isopropyl acrylate, n butyl acrylate, isobutyl) Acrylate, t-butyl acrylate, 2-ethyl hexyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, phenyl acrylate, etc., hydroxy-containing alkyl acrylate (eg, , 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc .; methacrylate esters such as alkyl methacrylate (eg, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate) Propylmethacrylate, n-Butylmethacrylate, Isobutylmethacrylate, t-Butylmethacrylate, 2-Ethylhexylmethacrylate, Cyclohexylmethacrylate, Phenylmethacrylate, Benzylmethacrylate, Phenylmethacrylate ), Hydroxy-containing alkyl metatalates (eg, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, etc.); acrylamides; substituted acrylamides, eg, N methyl acrylamide, N methylol acrylamide, N, N dimethylol acrylamide, N methoxymethyl acrylamide, etc .; methacrylamide; substituted methacrylamides such as N methyl methacrylate, N methylol methacrylamide, N, N dimethylol methacrylamide , N Toximethyl methacrylamide, etc .; Amino group-substituted alkyl acrylate, for example, N, N-dimethylaminoethyl acrylate; Amino group-substituted alkyl methacrylate, for example, N, N-deethylamino methacrylate: epoxy group-containing Atalylates, such as glycidyl attalylate; Epoxy group-containing metatalylates, such as glycidyl metatalylate; Acrylic acid salts such as sodium salt, potassium salt, ammonium salt; Methacrylic acid salts such as sodium salt, strength lithium salt, ammonium salt Is mentioned. One or more of the above monomers can be used in combination.

[0031] 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, maleic acid) Methyl, dimethyl maleate, methyl fumarate, dimethyl fumarate); salts of unsaturated dicarboxylic acids (eg, sodium, potassium, ammonium salts); monomers containing sulfonic acid groups or salts thereof (eg, styrene sulfone) Acid, vinyl sulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt); acid anhydrides such as maleic anhydride and itaconic anhydride; bur isocyanate; valyl isocyanate; burmethyl ether; Ether; butyl acetate). The above monomers can be used alone or in combination of two or more.

[0032] [Polyester]

The polyester is obtained, for example, by condensation polymerization of polyvalent carboxylic acids and polyhydric alcohols.

[0033] Examples of polyvalent carboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, aromatic dicarboxylic acids such as 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, diphenic acid, and p-oxyl. Aromatic carboxylic acids such as benzoic acid, p- (hydroxyethoxy) benzoic acid, aromatic polyunsaturated carboxylic acids such as phenylene diacrylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid Aliphatic dicarboxylic acid such as fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, hexahydrophthalic acid, tetrahydrophthalic acid, aliphatic unsaturated polycarboxylic acid, and cyclohexane dicarboxylic acid Trivalent or higher polyvalent carboxylic acids such as alicyclic dicarboxylic acid, trimellitic acid, trimesic acid, pyromellitic acid The can be exemplified. [0034] Examples of the polyhydric alcohols include aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, and aromatic polyhydric alcohols.

[0035] The aliphatic polyhydric alcohols include ethylene glycol, propylene glycol, 1,3 propanediol, 2,3 butanediol, 1,4 butanediol, 1,5-pentanediol, 1,6, — Aliphatic diols such as hexanediole, neopentinoleglycol, dimethylololeheptane, diethyleneglycolole, dipropyleneglycolole, 2, 2, 4 trimethylolene 1,3-pentanediol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol And triols and tetraols such as trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol.

[0036] Examples of the alicyclic polyhydric alcohols include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, spiroglycol, hydrogenated bisphenol A, and hydrogenated bisphenol A with ethylene oxide. And propylene oxide adduct, tricyclodecanediol, tricyclodecane dimethanol and the like.

[0037] Examples of the aromatic polyhydric alcohols include para-xylene dallicol, meta-xylene glycol mononole, onoletoxylene glyconole, 1,4-phenylene glycolenole, ethylene oxide adduct of 1,4-phenylene glycol, Examples thereof include ethylene oxide adducts and propylene oxide adducts of bisphenol A and bisphenol A. Furthermore, examples of the polyester polyol include lactone polyester polyols obtained by ring-opening polymerization of latones such as _ε -force prolatatone.

[0038] The polyester may be a monofunctional monomer introduced into the polyester for the purpose of blocking a part of the polar group at the end of the polyester polymer.

[0039] Examples of the monofunctional monomer include benzoic acid, black benzoic acid, bromobenzoic acid, chlorohydrobenzoic acid, sulfobenzoic acid monoammonium salt, sulfobenzoic acid monosodium salt, and cyclohexylaminocarbonylbenzoic acid. Acid, η dodecylaminocarbonylbenzoic 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, stearic acid, and lower alkyls thereof Monocarboxylic acids such as kill esters, aliphatic alcohols, aromatic alcohols

Monoalcohols such as alicyclic alcohols can be used.

[0040] In the present invention, these polyesters may be used alone or in combination of two or more.

[0041] [Polyurethane]

The polyurethane according to the present invention is preferably used in the form of so-called polyurethane emulsion (polyurethane aqueous emulsion) synthesized in the form of particles at the time of synthesis and dispersed in an aqueous solvent. .

The polyurethane aqueous emulsion used in the present invention can be produced by a conventionally known method. For example, a urethane prepolymer having 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 emulsification to obtain an emulsion of the urethane prepolymer having an average particle diameter of 0 to 2.5 m, the urethane prepolymer is chain-extended by continuously reacting with a chain extender. It can be obtained by a method or the like, and specifically can be obtained according to the method described in JP-A-2004-2732.

[0042] The number average molecular weight of the urethane prepolymer is preferably in the range of 1,000 to 50,000.

[0043] 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) using an organic solvent. Without reacting, a method of reacting a polyisocyanate compound described later with a polyol compound described later, 2) reacting a polyisocyanate compound described later with a polyol compound described later in an organic solvent, and then removing the compound. Although the method of making it a solvent is mentioned, the former method is preferable because the desolvation step is unnecessary!

[0044] 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, with an isocyanate ratio and an active hydrogen group in an equivalent ratio, preferably 1. 1 :;! To 3: 1, more preferably 1. 2:;! To 2: 1, the polyisocyanate compound and the active hydrogen-containing compound are reacted.

[0045] Further, in the reaction, aminosilane or the like is added to an excess isocyanate group as necessary. The terminal group may be reacted with a reactive group other than an isocyanate group such as an alkoxysilyl group.

[0046] Examples of the polyisocyanate compound include 2,4 tolylene diisocyanate, 2, 6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4 , 4'-diphenylmethane diisocyanate, 2, 4'-diphenylmethane diisocyanate, 2, 2, -diphenylmethane diisocyanate, 3, 3, 1-dimethyl-4, 4 'bidiylene diisocyanate Cyanate, 3, 3'-dimethoxy-4,4'-biphenyl diisocyanate, 3, 3, -dichloro-4,4, -biphenylene diisocyanate, 1,5-naphthalenedi

Tinolehexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylisophorone diisocyanate, 4, Examples include 4'-dicyclohexylenomethane diisocyanate, 3,3,4-dimethyl-4,4'-dicyclohexylmethane diisocyanate, and the like.

[0047] 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). It is possible to use a molecular weight compound).

[0048] The number average molecular weight of the high molecular weight compound is preferably in the range of 300 to 20,000, more preferably in the range of 500 to 10,000. The number average molecular weight of the low molecular weight compound is less than 300.

[0049] The number average molecular weight is measured by a force S measured by a known method using gel permeation chromatography.

[0050] The measurement conditions are as follows.

Solvent: Methylene chloride

Column: Shodex K806, K805, K803 (Used by connecting three Showa Denko Co., Ltd.)

Column temperature: 25 ° C Sample concentration: 0.1% by mass

Detector: RI Model 504 (GL Science Co., Ltd.)

Pump: L6000 (manufactured by Hitachi, Ltd.)

1.0ml / min

Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosohichi Co., Ltd.) A calibration fountain with 13 samples from Mw = 1000000-500 was used. 13 Sampnore (Ma, ίma)

[0051] These active hydrogen-containing compounds may be used alone or in combination of two or more.

Yes

[0052] Among the active hydrogen-containing compounds, examples of the high molecular weight compound include polyester polyol, polyether polyol, polycarbonate polyol, polyacetal polyol, polyacrylate polyol, polyester amide polyol, polythioether polyol, polybutadiene, and the like. And polyolefin polyols.

[0053] As the polyester polyol, there can be used a polyester polyol obtained by a dehydration condensation reaction of the following Daricol component and the following acid component.

[0054] 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, 3-methylolene 1,5-pentanediol, 1,6-hexanediol, neopentinoglycolanol, diethyleneglycolanol, triethyleneglycol, tetraethylenedarlicol, polyethylene glycol (molecular weight 300 to 6 000), Dipropylene glycol, tripropylene glycol, bishydroxyethoxybenzene, 1,4-cyclohexanedi-yl alcohol, 1,4-cyclohexanedimethanol, bisphenol Α, hydrogenated bisphenol Α, hydroquinone and their alkylenes Koxide adducts, etc. And the like.

[0055] 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, anhydrous maleic acid, fumaric acid, 1, 3 —Cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4 naphthalene dicarboxylic acid Acid, 2, 5 naphthalene dicarboxylic acid, 2, 6 naphthalene dicarboxylic acid, naphthalic acid, biphenyl dicarboxylic acid, 1,2-bis (phenoxy) ethane p, p'-dicarboxylic acid and anhydrides of these dicarboxylic acids Alternatively, ester-forming derivatives; p-hydroxybenzoic acid, p- (2-hydroxyethoxy) benzoic acid, ester-forming derivatives of these hydroxycarboxylic acids, and the like.

[0056] Polyesters obtained by ring-opening polymerization reaction of cyclic ester compounds such as ε-force prolatatone and their copolyesters can also be used.

[0057] 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, Neopentylglycol monoole, glycerin, trimethylolethane, trimethylolpropane, sonolebithonole, sucrose, aconite sugar, trimellitic acid, hemimerlic acid, phosphoric acid, ethylenediamine, diethylenetriamine, triisopropanolamine, pyrogallol, dihydroxybenzoic acid One or more compounds having at least two active hydrogen atoms such as hydroxyphthalic acid, 1,2,3 propanetrithiol, etc., for example, ethylene oxide, propylene oxide, Emissions oxide, styrene oxide, E peak chlorohydrin, tetrahydrofuran, one or compounds by a conventional method was addition-polymerized to a more, such as xylene cyclohexane and the like.

[0058] 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.

[0059] Among the active hydrogen-containing compounds, the low molecular weight compound is a compound having at least two active hydrogens in the molecule and having a number average molecular weight of less than 300. For example, glycol used as a raw material for the polyester polyol Ingredients: Polyhydroxy compounds such as glycerin, trimethylolethane, trimethylolpropane, sonorebitanol, pentaerythritol, etc .; ethylenediamine, 1,6 hexamethylenediamine, piperazine, 2,5 dimethylpiperazine, isophorone diamine 4,4'-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'-dicyclohexylmethanediamine, 1,4-cyclohexanediamine, 1,2 p-pandiamine, hydrazine, diethylenetriamine , Amine compounds such as triethylenetetramine Such as things.

[0060] In order to introduce a hydrophilic group into a urethane prepolymer, for example, as an active hydrogen-containing compound, the molecule has at least one active hydrogen atom in the molecule, and the hydrophilic group described above is introduced. If you use the compound that contains it as a raw material,

[0061] Examples of the compound having at least one active hydrogen atom in the molecule and containing the above hydrophilic group include 2-oxyethanesulfonic acid, phenolsulfonic acid, sulfobenzoic acid, sulfosuccinic acid. Sulfonic acid group-containing compounds such as acid, 5-sulfoisophthalic acid, sulfanilic acid, 1,3-phenylenediamine-4,6 disulfonic acid, 2,4 diaminotoluene 5 sulfonic acid, etc. and their derivatives or obtained by copolymerization thereof Polyestero Polio I nore;

Carboxylic acid-containing compounds such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolanol valeric acid, dioxymaleic acid, 2,6 dioxybenzoic acid, 3,4 diaminobenzoic acid and their derivatives Or polyesterole polyol obtained by copolymerizing them;

Tertiary amino group-containing compounds such as methyl jetanolamine, butyl jetanolamine, alkyldiisopropanolamine, etc. and their derivatives 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, jetyl sulfate, benzyl chloride, benzyl bromide, ethylene Reaction product of quaternizing agents such as chlorohydrin, ethylene bromohydrin, epichlorohydrin, bromobutane, etc .; containing at least 30% by mass of repeating units of ethylene oxide, and at least one activity in the polymer Polyoxyethylene glycol or polyoxyethylene polyoxypropylene copolymer glycol having a molecular weight of 300 to 20,000 containing hydrogen, polyoxyethylene polyoxybutylene copolymer glycol, polyoxyethylene polyoxyalkylene copolymer glycol or mono Alkyl Nonionic group-containing compounds such as ethers or polyester polyether polyols obtained by copolymerizing these may be mentioned. [0062] These may be used alone or in combination of two or more.

[0063] The water used in 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 finely disperse the urethane prepolymer in water and improve the storage stability of the polyurethane emulsion, it is necessary to contain an emulsifier.

[0064] Examples of the strength and the emulsifier include polyoxyethylene monopolyoxypropylene copolymer, polyoxyethylene nouryl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene sorbitol tet. Nonionic emulsifiers such as laoleate;

Fatty acid salts such as sodium oleate, alkyl sulfate salts, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, alkane sulfonate sodium salts, alkyl diphenyl ether sulfonate sodium salts,

Nonionic anionic emulsifiers such as polyoxyethylene alkyl sulfates and polyoxyethylene alkyl phenyl sulfates may be mentioned.

[0065] The amount of the emulsifier used is preferably 0.1 to 10 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the urethane prepolymer.

[0066] The urethane prepolymer is liquid at room temperature, or has a high viscosity at room temperature, or has a viscosity of 200 to 10, OOOmPa's at a temperature equal to or higher than the melting point even in a solid state. In the emulsifier, it is preferable to use a high shearing force S and to improve workability.

[0067] In the method for producing an aqueous emulsion of polyurethane, an aqueous dispersion, a stabilizer and the like can be added to water as necessary. Examples of such an aqueous dispersion include emulsions such as vinyl acetate, ethylene vinyl acetate, acrylic, and acrylic styrene; latexes such as styrene butadiene, acrylonitrile butadiene, and acryl butadiene; polyethylene, Examples include polyolefins and other ionomers; various aqueous dispersions such as polyurethanes, polyesters, polyamides, and epoxy resins.

[0068] [Minimum film-forming temperature] The minimum film-forming temperature of the polymer A according to the present invention is preferably 90 ° C. or less from the viewpoint of adhesion between particles.

[0069] The minimum film-forming temperature (MFT) refers to the minimum film-forming temperature when the aqueous emulsion of polymer A used as a binder is formed alone. The minimum film-forming temperature can be measured with a known measuring apparatus such as a minimum film-forming temperature measuring apparatus (SKLH-1, manufactured by Shimakawa Seisakusho).

[0070] [Light diffusing agent (beads)]

The light diffusion layer includes a binder and a light diffusing agent contained in the binder. By containing the light diffusing agent in the light diffusing layer in this way, it is possible to uniformly diffuse the light beam that passes through the light diffusing layer from the back side to the front side. Moreover, 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 the fine irregularities formed on the surface of the light diffusion sheet.

[0071] The 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, as an inorganic filler, it is possible to use silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof. Specific materials for organic fillers include the use of acrylic resin, acrylonitrile resin, polyurethane, polychlorinated butyl, polystyrene, polyacrylonitrile, polyamide, and the like. Of these, polymethyl methacrylate (PMMA) is particularly preferred, because acrylic resin with high transparency is preferred!

[0072] 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. Excellent spherical beads are preferred. In particular, it is preferable to use light diffusing particles having a sphericity of 80% by number or more. Note that the sphericity may be measured as follows. First, the particles of the light diffusing agent to be measured are photographed with an optical microscope at a magnification of 300 times and counted. The value obtained by calculating the ratio of the number of spheres (minor axis / major axis> 0.8) is the sphericity. However, since it is often difficult to discriminate a three-dimensional spherical shape in the optical microscope photographed image, the photographed image that is a planar image is a circular one (minor axis / major axis) 0.8. ) The circularity which is a value obtained by calculating the ratio of the number of the above may be used as the sphericity.

[0073] The lower limit of the average particle diameter of the light diffusing agent particles (light diffusing particles) is 1 am, particularly 2 μm, and 5 m is more preferable. The upper limit of the average particle diameter of the light diffusing particles is preferably 50 m, In particular, 20 μm, and more preferably 15 111 are preferred. This is because if the average particle size of the light diffusing particles is less than the above range, the unevenness of the surface of the light diffusing layer formed by the light diffusing agent is reduced and the light diffusing property required for the light diffusing sheet is not satisfied. Conversely, if the average particle diameter of the light diffusing particles exceeds the above range, the thickness of the light diffusing sheet increases, and uniform diffusion becomes difficult.

[0074] The particle size of the light diffusing particles is derived by enlarging 100 arbitrarily extracted light diffusing particles with a microscope, measuring the diameter of the particles, and simply averaging them. When the light diffusing particles are not spherical, the average value of the size of the light diffusing particles in any one direction and the size of the light diffusing particles in the direction orthogonal thereto is taken.

[0075] The lower limit of the amount of the light diffusing agent (the 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 10 parts, particularly 20 parts, and further 50 parts. The upper limit of the preferred amount is 500 parts, particularly 300 parts, and even 200 parts. This is because 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, there is an effect of fixing the light diffusing agent. It is because it falls. In the case of a so-called upward light diffusing sheet disposed on the surface side of the prism sheet, high light diffusibility is not required, so that the light diffusing agent is added in an amount of 10 to 40 parts, particularly 10 parts. More than 30 parts is preferable.

[Matting agent for anti-sticking layer]

In order to prevent sticking with the light guide plate, it is preferable to use a matting agent that protrudes from the sticking prevention layer. As the matting agent, the same one as the light diffusing agent can be used. The average particle diameter is preferably 1 to 10 m, preferably in the form of a substantially spherical shape in terms of the influence on optical performance and the prevention of damage to the contact member.

[0077] [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. [0078] Examples of the coating method include air doctor coater method, blade coater method, wire bar method, nif coater method, dip coater method, reverse roll coater method, gravure coater method, cast coating method, curtain coater method and extrusion coater method. Can be mentioned.

[0079] Examples of coating methods that can be used include dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, or US Pat. No. 2,681,294. The Etrusion Coating method using the hopper described in the issue. 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 ( It is the power to use the method of applying two or more layers as described in 1973, published by Asakura Shoten).

[0080] [Pretreatment primer]

Prior to the application of the coating solution of the present invention, a primer layer is provided on the base material as necessary.

[0081] In the case where the primer layer is provided or not, when the PET film is used as the base material, it is preferable to perform pretreatment. For the pre-treatment, the so-called etching solvent (for example, phenol, cresol, resorcin, chloral hydrate, black mouth phenol, etc.) to be bonded by the throwing effect, mechanical treatment, corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment There are surface activation treatments such as treatment, glow discharge treatment, active plasma treatment, laser treatment, mixed acid treatment and ozone treatment. When a primer layer is provided on a PET film, it can be provided before or after stretching during film formation of the PET film.

[0082] [Dry]

Drying according to the present invention is a step of removing water, which is a solvent of the aqueous emulsion applied on the base sheet, and is a step of heating at a temperature of 60 ° C. or higher.

[0083] The heating temperature is preferably 60 to 160 ° C, more preferably 80 to 140 ° C, and particularly preferably 90 to 120 ° C. Examples of the drying method include a method of supplying heated air to the applied aqueous emulsion, a method of radiating infrared rays with an infrared radiation device, and the like. [0084] [Film thickness]

States King preventing layer of the present invention is 0.1 after drying mass;! ~ 10g / m ^2, it is preferable the light diffusion layer is in the range of to 50 g / m ² after drying mass. If necessary, a surfactant, an antistatic agent, a chromaticity adjusting dye, a chromaticity adjusting pigment, a pH adjusting agent, an antiseptic, and the like may be added to the anti-sticking layer and the light diffusion layer.

Example

[0085] Hereinafter, the present invention will be described in detail based on examples, but the present invention is not construed as being limited based on the description of the examples. In the examples, “parts” represents “parts by mass” unless otherwise specified.

[0086] [Comparative Example 1]

Preparation of comparative sample:

(Light diffusion layer)

Polyester polyol having a cycloalkyl group (Cyclohexyl acrylate / butyl acrylate / ethyl acrylate / hydroxyethyl acrylate / acrylic acid copolymerization ratio 30/30/30/5/5 acrylic polymer and ethylene 100 parts of 20% methyl ethyl ketone solution of glycol reaction product, 50 parts of colloidal silica (“PL-1” from Fuso Chemical Co., Ltd.) with an average particle size of 20 nm and curing agent (Nippon Polyurethane Co., Ltd.) "Coronate HX" (hexamethylene diisocyanate)) In a polymer composition containing 5 parts, acrylic resin beads with an average particle size of 15 m ("MBX-15" from Sekisui Plastics Co., Ltd.) 50 parts are mixed to prepare a coating solution, and this coating solution is applied to the surface of a 100 m thick transparent polyester base material sheet (“A-4300” from Toyobo Co., Ltd.) by roll coating. to 15g / m ² (solid content conversion ) To become so coated was dried at 80 ° C and cured.

[0087] (Sticking prevention layer)

50 parts of the above polymer composition was mixed with 10 parts of acrylic resin beads having an average particle size of 5 m (“MBX-5” from Sekisui Plastics Co., Ltd.) to prepare a coating liquid. Comparison of light diffusing sheet in which anti-sticking layer is laminated by applying to the back side of the above base sheet by roll coating method to 3g / m ² (converted to solid content), drying and curing at 80 ° C Sample 1 was obtained. [Example 1]

Preparation of the sample of the present invention:

A light diffusing sheet was produced in the same manner as in Comparative Example 1 except that the anti-sticking layer in Comparative Example 1 was as follows.

[0089] (Sticking prevention layer)

Carboxyl group-containing water-dispersible polyester polyurethane (Dai Nippon Ink Co., Ltd. Hydran AP-40 (F), MFT = 29 ° C) 100 parts (This was originally a polyester. It is the same thing, this is probably the power, if possible, I would like one example of Polyester, I want the power S, what the power, thank you for your confirmation), polyfunctional poly Isocyanate aqueous dispersion (Dai Nippon Ink Co., Ltd., Bernock DNW-5010) 15 parts, colloidal silica with an average particle size of 20 nm (“PL-1” from Fuso Chemical Industries, Ltd.) 50 parts, average particle size 5 m acrylic resin beads (“MB X-5” from Sekisui Plastics Co., Ltd.) A coating solution that is an aqueous emulsion containing the above water-dispersible polyester polyurethane particles. And apply this coating solution to the The coating is a 3 g / m ² (solid content) on the back surface of the substrate sheet by Rukoto method, and dried at 100 ° C, light diffusion by laminating States King preventing layer by causing hardening sheet sample 1 Got.

[Example 2]

Preparation of the sample of the present invention:

[0091] (Sticking prevention layer)

Carboxyl group-containing water-dispersible polyester-based polyurethane (Hydran 8? -40 ^ from Dainippon Ink Co., Ltd.), ^^ Ding = 29 ° 0 100 parts, polyfunctional epoxy compound (Dainippon Ink Co., Ltd. containing glycidinole group) 10 parts of cross-linking agent CR-5L, colloidal silica with an average particle size of 20 nm (“PL-1” from Fuso Chemical Industry Co., Ltd.) 50 parts, acrylic resin beads with an average particle size of 511 m (Sekisui Plastics) “MBX-5” from Kogyo Co., Ltd.) was mixed to prepare an aqueous emulsion containing the above water-dispersible polyester-based polyurethane particles, and this coating solution was prepared by a roll coating method. Apply to the back of the base material layer to 3g / m ² (solid content conversion). A light diffusing sheet sample 2 on which a sticking prevention layer was laminated was obtained by coating, drying and curing at 100 ° C.

[0092] [Example 3]

Preparation of the sample of the present invention:

[0093] (Synthesis of water-dispersible acrylic polymer 1)

By emulsion polymerization, solid content consisting of monomer ratio of methyl methacrylate / butyl acrylate / tripropylene glycol dialylate / pentaerythritol tritalylate / hydroxyethyl methacrylate = 6 5/20/5/2/8 20% by mass of water dispersible acrylic polymer 1 was obtained. The MFT was 95 ° C.

[0094] (Sticking prevention layer)

100 parts of the above water-dispersible acrylic polymer 1, 15 parts of polyisocyanate aqueous dispersion (Dai Nippon Ink Co., Ltd., Bernock DNW-5010), colloidal silica with an average particle size of 20 nm (Fuso Chemical Co., Ltd.) "PL-1") of 50 parts and an acrylic resin bead with an average particle diameter of 511 m ("MBX-5" from Sekisui Plastics Co., Ltd.) are mixed to obtain the above water-dispersible acrylic polymer. A coating liquid that is a water-based emulsion containing the particles of the above is prepared, and this coating liquid is applied to the back surface of the base material layer at 3 g / m ² (in terms of solid content) by a roll coating method. A light diffusing sheet sample 3 on which a sticking prevention layer was laminated was obtained by drying with C and curing.

[0095] [Example 4]

(Synthesis of water-dispersible acrylic polymer 2)

By emulsion polymerization, solid content 20% by mass consisting of constituent monomer ratio of methyl methacrylate / ethyl acrylate / butyl acrylate / propylene glycol ditalylate / hydroxyethyl methacrylate = 35/30/20/5/10 Of water dispersible acrylic polymer 2 was obtained. The MFT was 55 ° C.

[0096] (Light diffusion layer)

100 parts of the above water-dispersible acrylic polymer 2, polyisocyanate aqueous dispersion (Dainippon Inn) The above-mentioned water dispersibility is obtained by mixing 15 parts of Kiln's Vernock DNW-5010) and 50 parts of an acrylic resin bead having an average particle size of 15 m (“MBX-15” from Sekisui Plastics Co., Ltd.). A coating liquid, which is an aqueous emulsion containing particles of acrylic polymer 2, was prepared, and this coating liquid was made by a roll coating method with a base sheet made of transparent polyester (Toyobo Co., Ltd.) having a thickness of _{100 iU m.}

) “8-4300”)) was applied at 15 g / m ² (in terms of solid content), dried at 100 ° C. and cured.

[0097] (Sticking prevention layer)

100 parts of the above water-dispersible acrylic polymer 2, 15 parts of polyisocyanate aqueous dispersion (Dai Nippon Ink Co., Ltd. Bernock DNW-5010), colloidal silica with an average particle size of 20 nm (Fuso Chemical Co., Ltd.) "PL-1") of 50 parts and an acrylic resin bead with an average particle size of 511 m ("MBX-5" of Sekisui Plastics Co., Ltd.) is mixed and mixed with the above water-dispersible acrylic polymer. A coating solution that is a water-based emulsion containing the above particles is prepared, and this coating solution is applied to the back surface of the base material layer to 3 g / m ² (in terms of solid content) by a roll coating method, and 90 ° A light diffusing sheet sample 4 on which a sticking prevention layer was laminated was obtained by drying with C and curing.

[Example 5]

Preparation of the sample of the present invention:

[0099] (Sticking prevention layer)

Carboxyl group-containing water-dispersible polyester-based polyurethane (Hydran 8? -40 ^ from Dainippon Ink Co., Ltd.), ^^ Ding = 29 ° 0 100 parts, polyfunctional epoxy compound (Dainippon Ink Co., Ltd. containing glycidinole group) 10 parts of cross-linking agent CR-5L, colloidal silica with an average particle size of 20 nm (“PL-1” from Fuso Chemical Industry Co., Ltd.) 50 parts, acrylic resin beads with an average particle size of 511 m (Sekisui Plastics) “MBX-5” from Kogyo Co., Ltd.) was mixed to prepare an aqueous emulsion containing the above water-dispersible polyester-based polyurethane particles, and this coating solution was prepared by a roll coating method. A light diffusing sheet that is coated on the back surface of the base material layer so that the amount is 3 g / m ² (in terms of solid content), and is dried and cured at 100 ° C to form a anti-sticking layer. Sample 5 was obtained.

[0100] [Comparative Example 2]

Preparation of comparative sample:

In Example 3, coating was carried out in the same manner as in Example 3 except that the anti-sticking layer was prepared without using 15 parts of polyisocyanate aqueous dispersion (Dai Nippon Ink Co., Ltd. Bernock DN W-5010). A light diffusing sheet comparative sample 2 which was dried and laminated with a sticking prevention layer was obtained.

[0101] << Evaluation >>

(Evaluation of light diffusion)

Examples;! To 5 and Comparative Examples 1 and 2 all had sufficient light diffusibility and light transmittance as a light diffusion sheet. Used for the backlight unit and marked with ○ if there is no problem with light diffusion.

[0102] (Evaluation of scratch resistance)

During the process of preparing the light diffusing sheet in Examples and Comparative Examples, the anti-scratch layer was evaluated for scratch resistance immediately after coating and drying.

[0103] The evaluation method was to wrap a 5-inch diameter paper core for 1000 m, swing it 20 cm at a speed of 2 sec / l reciprocating speed of 10 cm in the direction parallel to the axis, and then 200 from the top of the winding. Force, et al.

[0104] The evaluation criteria are as follows: ◎ when no flaws or shape changes were observed, ◯ when flaws were recognized, and X when flaws or shape changes were clearly recognized as X. Table 1 Shown in

[0105] (Evaluation of environmental suitability during production)

In the production of the anti-sticking layer, X indicates that organic solvent gas is generated, and ◯ indicates that there is no organic solvent gas.

[0106] [Table 1] Anti-sticking anti-sticking layer

Light diffusion sheet Light diffusion

(Immediately after drying) Environmental suitability during production

Comparative sample 1 O X X

Sample 1 ○ ○ ○

Sample 2 ○ ○ ○

Sample 3 ○ ○ ○

Sample 4 ○ ○ ○

Sample 5 ○ ○ ○

Comparative sample 2 X X

[0107] From Table 1, it is clear that Examples;! To 5 have sufficient light diffusibility and light transmittance, and are superior in scratch resistance after drying to the comparative example.

[0108] When the light diffusion sheet 1 is incorporated in the backlight unit as shown in Fig. 2, the sticking prevention layer 4 is in contact with other sheets such as a prism sheet and the light diffusion layer of the adjacent light diffusion sheet. Even so, damage to the anti-sticking layer 4 can be prevented. In addition, the backlight unit incorporating the light diffusion sheet of the present invention not only prevents the deterioration of the optical characteristics, but also makes it easier to maintain the desired optical characteristics.

Claims

The scope of the claims

[1] A light diffusing sheet comprising in this order a light diffusing layer containing a binder containing a light diffusing agent, a base sheet, and a anti-sticking layer containing a binder, wherein the anti-sticking layer binder comprises: A polymer (polymer A) particle containing a monomer unit having a functional group capable of undergoing a crosslinking reaction with a crosslinking agent as a constituent monomer unit and an aqueous emulsion containing a crosslinking agent capable of reacting with the functional group are formed on the substrate sheet. A light diffusion sheet, which is a polymer (polymer B) obtained by coating and drying.

[2] The first aspect of the invention is characterized in that the polymer containing a monomer unit having a functional group capable of undergoing a crosslinking reaction with a crosslinking agent as the constituent monomer unit is at least one of acrylic polymer, polyester, and polyurethane. The light diffusing sheet described in 1.

[3] The light diffusing sheet according to claim 1 or 2, wherein the functional group is a functional group capable of reacting with an isocyanato group or a glycidyl group.

[4] The scope of the claim characterized in that the minimum film-forming temperature of the polymer (polymer A) containing a monomer unit having a functional group capable of crosslinking reaction with a crosslinking agent as the constituent monomer unit is 90 ° C or lower. ;! The light diffusing sheet according to any one of items 3 to 3.

[5] The light diffusion sheet according to any one of claims 1 to 4, wherein the light diffusing agent is spherical.

[6] A lamp, a light guide plate arranged on the side of the lamp to guide the light emitted from the lamp in the front direction, and any force according to claims 1 to 5 arranged on the front side of the light guide plate A backlight unit for a liquid crystal display device, comprising the light diffusing sheet according to item 1.