TW201623537A - Highly adhesive composition, optical film using same and method for producing said optical film - Google Patents

Abstract

A highly adhesive composition which contains 100 parts by weight of a water-dispersible urethane resin having a carboxyl group, 1-25 parts by weight of a water-soluble carbodiimide compound and 1-25 parts by weight of a water-dispersible carbodiimide compound. An optical film which is obtained by providing at least one surface of a thermoplastic resin film with a highly adhesive layer that is formed of this highly adhesive composition.

Description

Easy-to-construct composition, optical film using the same, and manufacturing method thereof

The present invention relates to an easy-to-consist composition and an optical film having an easy-to-adhere layer composed of the easy-to-adhere composition. Further, the present invention relates to a method for producing the optical film, and a polarizing plate and an image display device including the optical film.

The acrylic resin film formed of a (meth)acrylic polymer represented by polymethyl methacrylate is excellent in optical characteristics such as light transmittance, and is excellent in balance between mechanical strength and moldability. Therefore, the acrylic resin film can be applied to an optical film assembled in an image display device such as a liquid crystal display device (LCD), a plasma display panel (PDP), or an organic EL display device (OLED).

The optical film is usually used in a state of being laminated with other functional films. For example, when the optical film is used as a polarizer protective film, it is laminated on at least one side of the polarizer through a hydrophilic adhesive. The obtained polarizing plate is used for an image display device or the like. In this case, it is important that the adhesion between the optical film and the polarizer is good.

However, the acrylic resin film is connected to the hydrophilic adhesive. The problem is poor, and there is a problem of insufficient adhesion to the polarizer. Therefore, it has been proposed to provide an easy adhesion layer to the surface of the acrylic resin film with a secondary adhesive resin such as polyester, acrylic, or polyurethane as a main component, and to provide an easy adhesion to the acrylic resin film. .

On the other hand, in recent years, the use of portable devices such as an image display device such as an LCD has been required to be used in various environments such as indoors and outdoors, and it is required to be resistant to heat and humidity in a high-temperature and high-humidity environment. The polarizing plate used for such applications is required to have high adhesion without delamination even under high temperature and high humidity.

In the polarizing plate which is excellent in adhesion under high temperature and high humidity, it is described that the surface of the (meth)acrylic resin film has an oxazoline group as a crosslinking agent in JP-A-2009-193061. The polymer forms an easy adhesion layer. Japanese Laid-Open Patent Publication No. 2014-35411 discloses that a crosslinking agent composed of a polyester resin and a polyvinyl alcohol resin and an isocyanate compound or a melamine compound is provided in order to improve the adhesion between the acrylic film and the polarizer. It is easy to follow the layer.

However, the optical film having an easy-adhesion layer disclosed in the above document initially exhibits good adhesion, but when used for a long period of time under high temperature and high humidity, the adhesion to the polarizer cannot be prevented from deteriorating. Since the adhesion is lowered, there is a problem that the initial performance (initial adhesion) cannot be maintained for a long period of time. In addition, the optical film having an easy-adhesion layer disclosed in the above document satisfies the heat and humidity resistance in an environment of about 40 to 60 ° C and 60 to 90% RH, but It is still unable to meet the heat and humidity resistance under excessively harsh environments (eg 80 ° C, 90% RH).

The present invention has been made in view of the above problems, and an object of the present invention is to provide an easy-to-construct composition which is capable of suppressing the deterioration of initial performance when used for a long period of time under high temperature and high humidity, and which is capable of satisfying the heat and humidity resistance in an excessively harsh environment, and Use this optical film.

According to the present invention,

(1) An easily-concomitant composition comprising 100 parts by weight of a water-dispersible urethane resin having a carboxyl group, 1 to 25 parts by weight of a water-soluble carbodiimide compound, and a water-dispersible carbon dioxide The amine compound is 1 to 25 parts by weight.

The invention further provides

(2) The easy-to-construct composition according to (1), wherein a weight ratio of the water-soluble carbodiimide compound to the water-dispersible carbodiimide compound is in the range of 30:70 to 95:5.

(3) The composition of the water-dispersible urethane resin further contains 0.1 to 15 parts by weight of the fine particles.

(4) An optical film comprising: a thermoplastic resin film; and an easy-to-construct composition formed on at least one surface of the thermoplastic resin film and as described in any one of (1) to (3) Then the layer.

(5) The optical film according to (4), wherein the thermoplastic resin film is made of a (meth)acrylic resin. as well as,

(6) A polarizing plate comprising a polarizer and covering the polarizer The optical film described in (4) or (5) is protected on the surface.

The invention further provides

(7) A method for producing an optical film comprising the steps of: water-soluble carbodiimide compound 1 containing 100 parts by weight of a water-dispersible urethane resin having a carboxyl group diluted with an aqueous solvent; 1 to 25 parts by weight, and 1 to 25 parts by weight of the water-dispersible carbodiimide compound, a step of applying the composition to the at least one surface of the thermoplastic resin film to form a coating film, and drying the coating film Easy to follow the steps of the layer.

The easy-advance composition of the present invention having the above-described configuration can suppress a decrease in initial performance when used for a long period of time under high temperature and high humidity, and can maintain high adhesion even in an excessively harsh environment. Therefore, the polarizing plate using the optical film having the easy-adhesion layer formed of the easy-to-adhere composition of the present invention is excellent in adhesion to the polarizer under high temperature and high humidity. In the present specification, the term "(meth)acrylic acid" is used as a general term for methacrylic acid, acrylic acid, or both. The term "(meth)acrylonitrile" is also the same.

Fig. 1 is a cross-sectional view schematically showing an example of an optical film of the present invention.

Fig. 2 is a cross-sectional view schematically showing an example of a polarizing plate of the present invention.

[Easy composition]

The easily-adhesive composition of the present invention contains a water-dispersible urethane resin having a carboxyl group (hereinafter sometimes abbreviated as U resin), and a water-soluble carbodiimide compound as a crosslinking agent (hereinafter sometimes abbreviated as S) A compound) and a water-dispersible carbodiimide compound (hereinafter sometimes abbreviated as a D compound). The easy-to-construct composition thus constituted suppresses the deterioration of the initial performance when used for a long period of time under high temperature and high humidity, and is excellent in adhesion even in an excessively harsh environment.

In this application, the easy-to-understand layer known in the past cannot avoid the decrease in adhesion when used for a long time under high temperature and high humidity. However, the present invention suppresses a decrease in initial performance at a high temperature and high humidity for a long period of time, and is excellent in adhesion under high temperature and high humidity. Although the reason is not clear, it is presumed that the S compound and the D compound form a crosslinked structure at different times, and exhibit the following functions.

That is, the S compound has a good compatibility with other hydrophilic resins and a high crosslinking reaction rate, so that when the easy-to-adhere layer is formed, or after formation, a crosslinked structure is formed with the carboxyl group of the U resin at an early stage. On the other hand, since the crosslinking reaction rate of the D compound is slower than that of the S compound, the unreacted D compound remains in the subsequent layer easily in the formation of the adhesion layer. When the U resin in the easy-adhesion layer is a polyester system under high temperature and high humidity, the polyester causes hydrolysis, and the ester bond is cleaved to generate a carboxylic acid group. Here, it is considered that the unreacted D compound reacts with the produced carboxylic acid group to form a crosslinked structure, and the strength deterioration of the easily-adhesive layer under high temperature and high humidity is suppressed by self-repairing the deterioration of the easily-adhesive layer due to hydrolysis.

Further, a functional group such as a carboxyl group is also present in the functional layer or the thermoplastic film which is laminated on the easy-adhesion layer. It is considered that the carboxyl group present in the functional layer or the thermoplastic film reacts with the unreacted D compound under high temperature and high humidity to form a crosslinked structure and suppress the strength deterioration of the easy-adhesion layer.

The U resin is not particularly limited as long as it is a water-dispersible urethane resin having a carboxyl group in its molecule. The U resin can be produced, for example, in the following manner. First, a polyisocyanate is reacted with a polyol in an organic solvent which is inert to water and is compatible with water to form an isocyanate-terminated prepolymer. This is then reacted with a chain extender having a free carboxyl group to obtain a chain urethane prepolymer. Subsequently, a U resin is obtained by water-based simultaneous elongation with a chain urethane prepolymer in water in the presence of a neutralizing agent. Further, the term "aqueousization" as used herein means that the resin is stably dispersed or emulsified in water.

Polyisocyanates are exemplified by, for example, tetramethylene diisocyanate, decamethyl diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate. , 2,4,4-trimethylhexamethylene diisocyanate, quaternary acid diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate Isoaliphatic diisocyanate; isophorone diisocyanate, hydrogenated xylene diisocyanate, 4,4'-cyclomethylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexyl diisocyanate, 1 , an alicyclic diisocyanate such as 3-bis(isocyanatemethyl)cyclohexane; toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4, 4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diiso Aromatic such as cyanate ester, 4,4'-dibenzyl diisocyanate, 1,5-naphthalene diisocyanate, xylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate Diisocyanate; dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, aromatic aliphatic diisocyanate such as α,α,α,α-tetramethylxylene diisocyanate, and the like. These may be used alone or in combination of two or more.

The polyol is not particularly limited as long as it has two or more hydroxyl groups in the molecule, and any appropriate polyol can be used. For example, polyacrylic acid polyols, polyester polyols, polyether polyols, polycarbonate polyols, and the like are exemplified. These may be used alone or in combination of two or more. Further, among these, it is preferred to use a polyester polyol, and a polyester urethane resin using a polyester polyol is excellent in the strength deterioration property of the easy-adhesion layer under high temperature and high humidity.

The chain extender having a free carboxyl group is exemplified by, for example, a dihydroxycarboxylic acid, dihydroxysuccinic acid or the like. Dihydroxycarboxylic acids are exemplified by, for example, dimethylol alkanoic acid (for example, dimethylol acetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutanoic acid, dimethylolvaleric acid) Iso-dihydroxyalkyl alkanoic acid. These may be used alone or in combination of two or more.

The neutralizing agent is exemplified by, for example, ammonia, N-methylmorpholine, triethylamine, dimethylethanolamine, methyldiethanolamine, triethanolamine, morpholine, tripropylamine, ethanolamine, triisopropanolamine, 2-amino group. -2-methyl-1-propanol and the like. These may be used alone or in combination of two or more.

Further, other chain extenders which can be used are exemplified by ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, furan dimethanol, diethylene glycol, triethylene glycol, and tetraethylene glycol. Equal low molecular weight diol compound and a polyether diol compound such as ethylene oxide, propylene oxide or tetrahydrofuran; or a dicarboxylic acid such as the above-mentioned low molecular weight diol compound and succinic acid (anhydride), adipic acid or phthalic acid (anhydride) a polyester diol having a hydroxyl group at the terminal obtained by an acid and the acid anhydride; a polyhydric alcohol such as trimethylolethane or trimethylolpropane; an amino alcohol such as monoethanolamine, diethanolamine or triethanolamine; ethylenediamine, Diamine compounds such as propylenediamine, butanediamine, hexamethylenediamine, phenylenediamine, toluenediamine, xylenediamine, isophoronediamine; water, ammonia, hydrazine, dibasic acid Amines, etc. These may be used alone or in combination of two or more.

The U resin has a number average molecular weight of preferably from 5,000 to 600,000, more preferably from 10,000 to 400,000, and preferably from 10 or more, more preferably from 10 to 50, most preferably from 20 to 45. When the acid value is within this range, a crosslinked structure is formed with the carbodiimide compound of the crosslinking agent, and the adhesion under high temperature and high humidity is excellent. Specific examples of the preferred U resin include "SUPERFLEX (registered trademark)" series manufactured by Daiichi Pharmaceutical Co., Ltd., "ADEKA BONTIGHTER (registered trademark) HUX series manufactured by ADEKA Corporation, and "TAKERUCK (registered trademark) manufactured by Mitsui Chemicals Co., Ltd. "W, WPB, WS" series, and the "HYDRAN (registered trademark)" series manufactured by DIC Corporation, and other commercially available U resins.

The composition of the easy-to-adhere composition is preferably diluted with an aqueous solvent based on the workability at the time of formation of an easy-to-adhere layer. As the aqueous solvent, water or water and a hydrophilic organic solvent (for example, an alcohol solvent such as methanol, ethanol, isopropanol, ethylene glycol or propylene glycol; an ester solvent such as ethyl acetate, butyl acetate or γ-butyrolactone; a ketone solvent such as acetone; an ether solvent such as tetrahydrofuran or dioxane; N- A mixed solvent of an aprotic polar solvent such as methylpyrrolidone is most preferably water.

The content of the U resin in the composition to be easily formed is not particularly limited, and may be appropriately set in consideration of coating workability, and is, for example, preferably 1 to 25% by weight, more preferably 3 to 20% by weight, still more preferably 5 to 5 15% by weight. When the U resin of the composition is easily in the above range, workability in forming an easy-to-attach layer is excellent, and it is preferable. Further, the solid content of the composition to be easily formed may be appropriately set in consideration of coating workability, etc., but is preferably from 1 to 30% by weight, more preferably from 2 to 25% by weight, still more preferably from 3 to 20% by weight. .

The S compound is not particularly limited as long as it has a water-soluble compound having two or more carbodiimide groups in the molecule, and is, for example, synthesized by the condensation reaction of the decarbonation of the organic diisocyanate compound to synthesize the isocyanate terminal polycarbodiimide. After the amine, it reacts with a hydrophilic organic compound having a functional group reactive with an isocyanate group, and a polycarbodiimide-based resin obtained by blocking a terminal isocyanate with a hydrophilic segment and dissolved in water. For the S compound, "CARBODILITE (registered trademark) SV-02", "CARBODILITE (registered trademark) V-02", "CARBODILITE (registered trademark) V-04", "CARBODILITE (registered trademark) V- manufactured by Nisshinbo Chemical Co., Ltd. can be used. 10", "CARBODILITE (registered trademark) V-02-L2" and other commercial products.

The amount of the S compound used is preferably from 1 to 25 parts by weight, more preferably from 3 to 20 parts by weight, still more preferably from 5 to 15 parts by weight, per 100 parts by weight of the U resin.

Compound D as long as it has two or more carbon diimine in the molecule The water-dispersible compound is not particularly limited, and is exemplified by, for example, a compound having reactivity with an isocyanate group after synthesizing an isocyanate terminal polycarbodiimide by a condensation reaction of a decarbonation reaction of an organic diisocyanate compound. The hydrophilic organic compound is reacted, and the polycarbodiimide-based resin obtained by blocking the terminal isocyanate with a hydrophilic segment is finely dispersed (emulsified) without being dissolved in water. As the water-dispersible carbodiimide compound, commercially available products such as "CARBODILITE (registered trademark) E-01" and "CARBODILITE (registered trademark) E-02" manufactured by Nisshinbo Chemical Co., Ltd. can be used.

The amount of the compound D to be used is preferably from 1 to 25 parts by weight, more preferably from 1 to 20 parts by weight, still more preferably from 1 to 10 parts by weight, per 100 parts by weight of the U resin. The weight ratio (S/D) of the S compound to the D compound in the easily-conducting composition is usually in the range of 30:70 to 95:5, preferably in the range of 40:60 to 90:10, more preferably 50:50. ~80:20 range.

The easy-to-concomitant composition may contain any suitable microparticles, preferably water-dispersible microparticles, in conjunction with the desired function. As the fine particles, any of inorganic fine particles and organic fine particles can be used. Examples of the inorganic fine particles include inorganic oxides such as cerium oxide, titanium oxide, aluminum oxide, and zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium citrate, calcium silicate hydrate, aluminum citrate, and strontium. Magnesium acid, calcium phosphate, and the like. The organic fine particles are, for example, a polyfluorene-based resin, a fluorine-based resin, a (meth)acrylic resin, or a (meth)acrylonitrile-based resin. Among these, a (meth)acrylonitrile-based resin is preferred. Microparticles made of (meth)acrylonitrile-based resin due to It has excellent adhesion inhibition, excellent transparency, no haze, and no coloration, so the adhesion layer has less influence on optical characteristics. Further, since the strength and the adhesion of the easy-adhesion layer are lowered by the distribution of the fine particles, the easy-adhesion layer of the fine particles formed of the (meth)acrylonitrile-based resin can suppress the strength and adhesion of the easily-adhesive layer. It is better to drop.

The average particle diameter of the fine particles is not particularly limited, but is preferably from 1 to 500 nm, more preferably from 50 to 350 nm, even more preferably from 100 to 300 nm, from the viewpoint of maintaining transparency of the adhesion layer. By using the fine particles of the particle size, moderate irregularities can be formed on the surface of the easy-adhesion layer, which can effectively reduce the friction between the thermoplastic resin film and the contact layer of the easy-adhesive layer and/or the easy-adhesion layer, and can inhibit adhesion. . The above average particle diameter means the median diameter (d50) measured by the laser diffraction/scattering particle size distribution measurement.

The content of the fine particles is preferably 0.1 to 15 parts by weight based on 100 parts by weight of the U resin in terms of solid content. More preferably, it is 0.3 to 5 parts by weight, and more preferably 0.5 to 3 parts by weight.

The easily-adhesive composition may contain a crosslinking agent different from the above-mentioned S and D compounds or a resin containing a crosslinking group in order to increase the coating film strength. The crosslinking agent is exemplified by a urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, stanol-based or the like. Further, in order to promote the crosslinking reaction, a catalyst or the like may be appropriately used as needed.

The easy-to-concomitant composition may further contain any suitable additives. The additives are exemplified by, for example, a dispersion stabilizer, a shaker, an antioxidant, an ultraviolet absorber, an antifoaming agent, a tackifier, a dispersant, a surfactant, a catalyst, a slip agent, an antistatic agent, and the like.

[Optical film]

Fig. 1 shows an example of an optical film of the present invention. The optical film 1 shown in Fig. 1 has an easy-adhesion layer 3 formed of the above-mentioned easy-to-adhere composition on one surface of the thermoplastic resin film 2. Further, the optical film of the present invention may form an easy-adhesion layer on both surfaces of the thermoplastic resin film.

The thermoplastic resin constituting the thermoplastic resin film is, for example, a cellulose resin such as triethyl fluorenyl cellulose, a polyester resin, a polyether oxime resin, a polycarbonate resin, a polyamide resin, or a polyruthenium resin. An amine resin, a polyolefin resin, a cyclic polyolefin resin, a (meth)acrylic resin, a polyarylate resin, a polystyrene resin, a polyvinyl alcohol resin, or the like. These may be used alone or in combination of two or more. These intermediate (meth)acrylic resins (hereinafter sometimes abbreviated as ACR) have poor adhesion to a hydrophilic adhesive, and therefore the effects of the present invention are particularly remarkable when ACR is used.

The glass transition temperature of ACR (hereinafter referred to as Tg) is preferably 115 ° C or more, more preferably 120 ° C or more, and still more preferably 125 ° C or more. The thermoplastic resin film contains ACR having a Tg of 115 ° C or higher as a main component, and is excellent in durability. Further, the upper limit of the Tg is not particularly limited, but is usually 170 ° C or less from the viewpoint of moldability.

The ACR is exemplified by poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth) acrylate copolymer, and Methyl methacrylate-(meth) acrylate-(meth)acrylic acid copolymer, methyl methacrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl group) Methyl acrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.). In the above, a poly(meth)acrylic acid C _1~6 alkyl ester such as poly(methyl) acrylate is preferable, and more preferably methyl methacrylate (50 to 100% by weight, preferably 70 to 100% by weight of a methyl methacrylate resin.

Specific examples of the ACR are, for example, "ACRYPET (registered trademark) VH", "ACRYPET (registered trademark) VRL20A" manufactured by Mitsubishi Corporation, and high Tg obtained by intramolecular crosslinking or intramolecular cyclization. Base) acrylic resin.

The ACR preferably has a ring structure from the viewpoint of high heat resistance, high transparency, and high mechanical strength. The ACR having a ring structure in the main chain is exemplified by, for example, a resin having a glutaric anhydride structure or a glutarimide structure (WO2007/26659, WO2005/108438), a maleic anhydride structure or an N-substituted Malayan A resin having an amine structure (Japanese Unexamined Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. 2007-31537) Japanese Laid-Open Patent Publication No. 2007-63541 and JP-A-2008-191426.

The thermoplastic resin film may also contain an additive. Examples of the additives include antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; ultraviolet absorbers; and near ultraviolet absorbers; Burning agent Antistatic agents such as cationic, nonionic surfactants; colorants such as inorganic pigments, organic pigments, dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers or inorganic fillers; plasticizers; A lubricant; an antistatic agent; a flame retardant; a phase difference reducing agent.

The method for producing the thermoplastic resin film is not particularly limited, and for example, the thermoplastic resin may be sufficiently mixed with another polymer or an additive by any appropriate mixing method, and a thermoplastic resin composition may be prepared in advance, and then formed into a film. . Alternatively, the thermoplastic resin may be separately mixed with another polymer or an additive to form a uniform solution, and then formed into a uniform mixture.

When the thermoplastic resin composition is produced, the film raw material is preliminarily blended by any appropriate mixer such as an OM mixer, and then the mixture obtained by kneading is extruded. In this case, the kneading machine used for the extrusion kneading is not particularly limited, and any suitable mixer such as an extruder such as a single-screw extruder or a two-axis extruder or a pressure kneader can be used.

The film forming method is exemplified by any suitable film forming method such as a solution casting method (solution casting method), a melt extrusion method, a roll method, or a compression molding method. Among these film forming methods, a melt extrusion method is preferred.

The melt extrusion method is exemplified by, for example, a T die method, a blow molding method, or the like. The forming temperature is preferably from 150 to 350 ° C, more preferably from 200 to 300 ° C.

When the film is formed by the T-die method, the T-die can be attached to the front end of a conventional single-axis extruder or a two-axis extruder, and after the film is formed by the T-die, the film is taken up by winding. A film in the form of a roll was obtained.

The thermoplastic resin film can be either an unstretched film or a stretched film One. When the film is stretched, it may be either a 1-axis stretch film or a 2-axis stretch film. When the film is stretched in two directions, it may be either a simultaneous 2-axis stretch film or a sequential 2-axis stretch film. When the 2-axis is extended, the mechanical strength is improved and the film performance is improved.

The stretching temperature is preferably near the glass transition temperature of the thermoplastic resin composition of the film raw material, and specifically, it is preferably (glass transition temperature -30 ° C) ~ (glass transition temperature + 100 ° C), more preferably (glass transfer) Temperature -20 ° C) ~ (glass transition temperature + 80 ° C) within the range. When the extension temperature is not reached (glass transition temperature - 30 ° C), there is a possibility that a sufficient stretching ratio cannot be obtained. On the contrary, when the stretching temperature exceeds (glass transition temperature + 100 ° C), the resin composition is caused to flow, and there is a possibility that the stable extension cannot be performed.

The extension ratio defined by the area ratio is preferably 1.1 to 25 times, more preferably 1.3 to 10 times. When the stretching ratio is less than 1.1 times, the toughness does not increase with the extension. When the stretching ratio is more than 25 times, the effect of increasing the stretching ratio (increased toughness) is not confirmed.

The stretching speed is preferably from 10 to 20,000%/min in a direction, more preferably from 100 to 10,000%/min. When the stretching speed is less than 10%/min, the time for obtaining a sufficient stretching ratio becomes long, so that the manufacturing cost is high. When the stretching speed exceeds 20,000%/min, there is a possibility that the stretched film is broken or the like.

The thermoplastic resin film can be subjected to heat treatment (annealing) or the like after the stretching treatment in order to stabilize the optical isotropic properties or mechanical properties. The heat treatment conditions may be any suitable conditions.

The thickness of the thermoplastic resin film is preferably from 5 to 200 μm, more preferably from 10 to 100 μm. When the thickness is less than 5 μm, the sufficient strength as an optical film cannot be obtained. When the thickness exceeds 200 μm, the transparency is lowered, and it is not suitable for use as an optical film.

The thickness of the easy-to-back layer can be set to any appropriate value. It is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, most preferably 0.2 to 1.0 μm. By setting it in this range, it is excellent in adhesiveness with another functional film, and it can suppress the display phase difference with respect to an easy adhesion layer.

Various functional layers may also be formed on the surface of the optical film opposite to the surface on which the easy-to-adhere layer is formed. The functional layer is exemplified by, for example, an antistatic layer, an adhesive layer, an adhesive layer, an easy adhesion layer, an anti-glare layer, an anti-fouling layer such as a photocatalyst layer, an anti-reflection layer, a hard coat layer, an ultraviolet shielding layer, and a heat line. A shielding layer, an electromagnetic wave shielding layer, a gas barrier layer, and the like.

The optical film can be used as, for example, a polarizer protective film, a retardation film, a viewing angle compensation film, a light diffusion film, a reflective film, an antireflection film, an antiglare film, a brightness enhancement film, and a conductive film for a touch panel. And these are preferably used as a polarizer protective film.

[Polarizer]

Next, an example of the polarizing plate of the present invention will be described. The polarizing plate 10 shown in FIG. 2 has a surface on the surface of the thermoplastic resin film 2 having the easy-adhesive layer 3 formed of the above-mentioned easy-to-adhere composition, and the surface of the easy-adhesion layer is transmitted through the adhesive 5 to form a polarizer. The structure of 6. Further, although not shown, the polarizing plate 10 may have a surface on the opposite side of the polarizer 6 from the optical film 1. A protective film that is laminated on the adhesive layer.

The polarizer can be any suitable polarizer depending on the purpose. For example, a dichroic substance such as iodine or a dichroic dye is adsorbed onto a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formaldehydeized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partial saponified film. A uniaxially stretcher, a polyene alignment film such as a dehydration treatment of polyvinyl alcohol or a dehydrochlorination treatment of polyvinyl chloride. Among these, a polarizing two-color polarizer which adsorbs a dichroic substance such as iodine to a polyvinyl alcohol-based film and is uniaxially stretched is preferably high. The thickness of the polarizers is not particularly limited and is generally about 1 to 80 μm.

The adhesive forming the adhesive layer may be any suitable adhesive. Preferably, the adhesive layer is formed of an adhesive composition containing a polyvinyl alcohol-based resin.

The protective film provided on the opposite side of the optical film 4 of the polarizer 6 may be any suitable protective film or may be formed of the same material as the above thermoplastic resin.

[Image display device]

The image display device of the present invention includes the above-described polarizing plate. Specific examples of the image display device are exemplified by a self-luminous display device such as an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED: Field Emission Display), and a liquid crystal display device (LCD).

[Method of Manufacturing Optical Film]

In the preferred method of producing the optical film of the present invention, the solvent is diluted with an aqueous solvent. The easy-to-construct composition containing a water-dispersible urethane resin having a carboxyl group, a water-soluble carbodiimide compound, and a water-dispersible carbodiimide compound is applied to at least one of the thermoplastic resin film A coating film is formed on the surface (coating step), and then the coating film is dried to form an easy-adhesion layer (drying step).

The method of coating the easy-to-concomitant composition in the coating step may employ any appropriate method. For example, a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slit die coating method, a curtain flow coating method, a fountain coating method, and the like are exemplified. The thickness of the coating film formed in the coating step can be appropriately adjusted depending on the thickness required when the coating film becomes an easy-to-attach layer.

The coating of the thermoplastic resin film is preferably carried out by surface treatment of the surface of the composition. The surface treatment is preferably corona discharge treatment or plasma treatment. By applying a corona discharge treatment, the adhesion between the thermoplastic resin film and the easy-adhesion layer can be improved.

The drying step is not particularly limited, and a conventionally known method can be used. The drying temperature is typically 50 ° C or higher, preferably 90 ° C or higher, more preferably 110 ° C or higher. By setting the drying temperature to this range, it is possible to obtain an optical film excellent in color fastness (especially, under high temperature and high humidity). The upper limit of the drying temperature is preferably 200 ° C or higher, more preferably 180 ° C or higher.

According to the method for producing an optical film of the present invention, when an optical film of a stretched film is produced from a thermoplastic resin film which is not stretched, and when an optical film of a biaxially stretched film is produced from a uniaxially stretched thermoplastic resin film, it is necessary to These thermoplastic resin films are stretched. The extension of the thermoplastic resin film can be performed before the formation of the easy adhesion layer, or after the formation of the easy adhesion layer get on. Further, the formation of the easy-adhesion layer can be performed simultaneously with the extension of the thermoplastic resin film.

When the formation of the easy-adhesion layer is performed simultaneously with the extension of the thermoplastic resin film, the thermoplastic resin film forming the coating film of the easy-to-conform composition may be extended in a heating atmosphere after, for example, the coating step. By applying heat to the film for stretching, the coating film of the composition which is formed on the surface of the thermoplastic resin film is easily dried to form an easy-adhesion layer. In this case, the film stretching treatment and the drying of the easily-adherent composition can be simultaneously performed, and it is preferable because of excellent productivity.

[Examples]

Hereinafter, the present invention will be described in more detail by way of examples. Further, the present invention is not limited to the following embodiments.

The following materials are used as the raw materials.

<U resin>

Emulsion of a water-dispersible urethane resin having a carboxyl group [manufactured by First Industrial Pharmaceutical Co., Ltd., SUPERFLEX (registered trademark) 210, solid content: 35 wt%]

<S Compound (1)>

An aqueous solution containing a water-soluble carbodiimide compound [manufactured by Nisshinbo Chemical Co., Ltd., CARBODILITE (registered trademark) V-02-L2, solid content 40% by weight]

<S Compound (2)>

An aqueous solution containing a water-soluble carbodiimide compound [manufactured by Nisshinbo Chemical Co., Ltd., CARBODILITE (registered trademark) V-10, solid content: 40% by weight]

<D compound>

Emulsion of water-dispersible carbodiimide compound [manufactured by Nisshinbo Chemical Co., Ltd., CARBODILITE (registered trademark) E-02, solid content 40% by weight]

<microparticle>

Emulsion containing acrylonitrile-based fine particles (PAN fine particles) [manufactured by Sekisui Chemical Co., Ltd., ADVANCELL NS K-001, average particle diameter: 150 nm, solid content: 20% by weight]

Examples 1 to 5 and Comparative Examples 1 to 10 1. Easy to follow the manufacture of the composition

The components shown in Tables 1 and 2 were mixed so as to have a solid content (unit: parts by weight) shown in Tables 1 and 2 to produce an easy-to-extend composition. Further, the aqueous solvent which is easily followed by the composition was ion-exchanged water to prepare a solid content of 8 wt%.

2. Manufacturing of optical film

Acrylic resin [Tg: 135 ° C, melt viscosity: 700Pa. s (temperature 270 ° C, shear viscosity 100 (1/sec))] particles using a single-axis extruder ( = 20.0 mm, L/D = 25) and a coat hanger type T die (width 150 mm) were melt-extruded at 280 ° C, and the resin composition in a molten state was sprayed onto a cooling roll maintained at 110 ° C to form a thickness of 100 μm. Acrylic resin film. Next, the above-obtained easy-to-construct composition was applied onto the surface of one of the acrylic resin films using a bar coater, and then dried in a hot air dryer at 100 ° C for 90 seconds. Subsequently, the film was uniaxially stretched (stretching ratio: 2.5 times) using a table spreader, and an optical film having an easy-adhesion layer having a thickness of 0.3 μm was formed on the surface of the acrylic resin film having a thickness of 40 μm.

3. Manufacture of polarizing plates

A polyvinyl alcohol-based adhesive composition was applied to the easy-adhesion layer side of the optical film obtained above. Further, a polyvinyl alcohol-based adhesive composition was applied to one side of a triacetonitrile cellulose film (protective film) having a thickness of 40 μm which was subjected to a chemical treatment. Then, the laminated optical film and the protective film were applied through a polyvinyl alcohol-based adhesive on both sides of a polarizer having a thickness of 30 μm, and the obtained laminated body was dried in a hot air dryer (70 ° C) for 5 minutes to prepare a polarizing plate. Further, a protective film made of a triacetyl cellulose film was provided on both sides of the polarizer to prepare a reference polarizing plate for evaluation.

The evaluation of the polarizing plate obtained above was performed as follows. The evaluation results are shown in Tables 1 and 2.

(1) Initial adhesion

A test piece of a size of 25 mm × 250 mm was cut out from the polarizing plate obtained above, and the surface of the optical film of the test piece was adhered, and then attached to a glass plate to obtain a sample for measurement. Subsequently, a slit was cut between the polarizer of the sample and the optical film, and the polarizer and the protective film were cut, and the peeling strength of 90 degrees was measured according to the floating roll method of Japanese Adhesive Industrial Standard JAI 13-1996. Further, the peeling strength was measured under the same conditions for the reference polarizing plate. The peeling strength was evaluated from the measurement results on the following basis.

○: peeling strength is superior or equivalent to the reference polarizer

△: peeling strength is worse than the reference polarizer

×: Undensed and cannot be measured

(2) Humidity resistance (60 ° C, 90% RH)

The measurement sample obtained in the same manner as described above was placed in a thermo-hygrostat having a temperature of 60 ° C and a humidity of 90% RH, and the heat treatment was carried out for 250 hours and 500 hours, and the peeling was measured in the same manner as the evaluation of the initial adhesion. Then the intensity. The peeling strength was evaluated from the measurement results on the following basis.

◎: peeling strength is superior to the reference polarizer

○: peeling strength is equal to that of the reference polarizer

△: peeling strength is worse than the reference polarizer

×: Undensed and cannot be measured

(3) Moisture and heat resistance (80 ° C, 90% RH)

The sample for measurement obtained in the same manner as above was placed in a constant temperature and humidity machine at a temperature of 80 ° C and a humidity of 90% RH, and heat treatment was performed for 100 hours. The peeling strength was measured in the same manner as the evaluation of the initial adhesion. The peeling strength was evaluated from the measurement results on the following basis.

◎: peeling strength is superior to the reference polarizer

○: peeling strength is equal to that of the reference polarizer

△: peeling strength is worse than the reference polarizer

×: Undensed and cannot be measured

As shown in Table 1, a water-dispersible urethane resin (U resin) containing a carboxyl group and a water-soluble carbodiimide compound (S compound) and a water-dispersible carbodiimide compound (D compound) were used. The optical film of Examples 1 to 5 which can be easily formed by the composition can suppress the initial performance degradation under high temperature and high humidity (60 ° C, 90% RH), and is displayed with a polarizer for a long time under high temperature and high humidity. As a result of excellent adhesion, it was also excellent in adhesion in a severe high-temperature and high-humidity environment (80 ° C, 90% RH). On the other hand, as shown in Table 2, the optical films of Comparative Examples 1 to 7 which did not contain a crosslinking agent or contained only the S compound showed a decrease in adhesion to the polarizer under high temperature and high humidity. Further, the optical films of Comparative Examples 8 to 10 containing only the D compound were excellent in adhesion when used for a long period of time under high temperature and high humidity, but showed poor initial adhesion.

Claims (7)

An easy-to-construct composition comprising 100 parts by weight of a water-dispersible urethane resin having a carboxyl group, 1 to 25 parts by weight of a water-soluble carbodiimide compound, and a water-dispersible carbodiimide compound 1 ~25 parts by weight. The composition of claim 1, wherein the weight ratio of the water-soluble carbodiimide compound to the water-dispersible carbodiimide compound is in the range of 30:70 to 95:5. The composition of claim 1 or 2, which further comprises 0.1 to 15 parts by weight of the fine particles of the water-dispersible urethane resin. An optical film comprising a thermoplastic resin film, and an easy-adhesion layer formed on at least one surface of the thermoplastic resin film and formed of the easy-to-adhere composition according to any one of claims 1 to 3. The optical film of claim 4, wherein the thermoplastic resin film is made of a (meth)acrylic resin. A polarizing plate comprising a polarizer and an optical film as claimed in claim 4 or 5 protected by a surface of the polarizer. A method for producing an optical film, which comprises the steps of: 100 parts by weight of a water-dispersible urethane resin having a carboxyl group diluted with an aqueous solvent, and 1 to 25 weight of a water-soluble carbodiimide compound; And a water-dispersible carbodiimide compound, wherein 1 to 25 parts by weight of the easily-adhesive composition is applied to at least one surface of the thermoplastic resin film to form a coating film, and the coating film is dried to form an easy-adhesion layer The steps.