KR20170093790A - Highly-adhesive composition, optical film using same, and production method therefor - Google Patents

Abstract

Which is capable of suppressing deterioration in initial performance under prolonged use under high temperature and high humidity and satisfying moisture resistance and heat resistance in a harsh environment, and an optical film using the same. A water dispersible urethane resin (A) having a glass transition temperature of less than 60 占 폚, a water dispersible urethane resin (B) having a glass transition temperature of 60 占 폚 or more and 120 占 폚 or less and a weight- ≪ / RTI > And an easy-to-adhere layer comprising the adhesive composition is formed on at least one surface of the thermoplastic resin film.

Description

TECHNICAL FIELD [0001] The present invention relates to an adhesive composition, an optical film using the same, and a method of producing the same. BACKGROUND ART [0002]

The present invention relates to an adhesive film, and an optical film having an adhesive layer for easy adhesion. The present invention also relates to a production method of the optical film, and a polarizing plate and an image display device provided with the optical film.

It is known that an acrylic resin film formed from a (meth) acrylic polymer represented by methyl polymethacrylate has excellent optical characteristics such as light transmittance and excellent balance between mechanical strength and moldability. For this reason, the acrylic resin film is applied to an optical film inserted in an image display apparatus such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic EL display (OLED).

The optical film is usually used in a laminated state with another functional film. For example, when used as a polarizer protective film, the optical film is laminated on at least one surface of the polarizer with a hydrophilic adhesive layer interposed therebetween. The obtained polarizing plate is used for an image display apparatus 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 has a problem that adhesion with the hydrophilic adhesive is poor and adhesion with the polarizer is not sufficient. Thus, a method has been proposed in which an easy-to-adhere layer mainly composed of a resin such as polyester, acrylic, urethane or the like is formed on the surface of an acrylic resin film to give an adhesive property to an acrylic resin film.

On the other hand, handheld devices and the like using an image display device such as an LCD are often used in various environments, indoors and outdoors, and there is a case in which heat and humidity resistance that can withstand high temperature and high humidity environments is required. The polarizing plate used for such a purpose is required to have high adhesiveness without causing delamination even under high temperature and high humidity.

Therefore, Japanese Laid-Open Patent Publication No. 2009-274390 discloses a laminated film having good adhesion to a polarizer even though it has a thermal history exposed under high temperature, and it has been known that a part of an acid structure included in an acidic urethane- Based urethane resin which is obtained by neutralizing a urethane resin with a nonvolatile base. Japanese Laid-Open Patent Publication No. 2009-205135 discloses a polarizer protective film excellent in adhesion to a polarizer under high temperature and high humidity, which is obtained by emulsion-polymerizing a monomer composition comprising a polyalkylene glycol (meth) acrylate on the surface of an acrylic resin film (Meth) acryl-based resin dispersion to form an easy-to-adhere layer.

However, although the optical film having an easy-to-adhere layer disclosed in the above document shows good adhesion at first, a decrease in adhesion with a polarizer can not be avoided in long-term use under high temperature and high humidity, and an initial performance (initial adhesion property) There is a problem that it is not maintained. In addition, the optical film having an easy-to-adhere layer disclosed in the above document can be used for a long time under high temperature (for example, 80 DEG C) or under high temperature and high humidity (for example, 40 to 60 DEG C, 60 to 95% RH) (For example, 80 deg. C, 90% RH) can not satisfy the wet heat resistance.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and it is an object of the present invention to provide an easy-to-adhere composition capable of suppressing deterioration of initial performance in long-term use under high temperature and high humidity and satisfying humidity and heat resistance under a harsh environment, To provide a film.

According to the present invention,

(1) A water dispersible urethane resin (A) having a glass transition temperature of less than 60 占 폚, a water dispersible urethane resin (B) having a glass transition temperature of 60 占 폚 or more and 120 占 폚 or less and a weight- There is provided a tackifying composition comprising,

(2) The ease of use composition according to (1), wherein the weight ratio of the water dispersible urethane resin (A) and the water dispersible urethane resin (B) is in the range of 95: 5 to 40: 60,

(3) The adhesive composition according to (1) or (2), wherein the water dispersible urethane resin (A) has a glass transition temperature of -25 캜 or higher,

(4) The adhesive composition according to any one of (1) to (3), wherein the water dispersible urethane resin (A) has an elongation at break of 300% or less,

(5) The adhesive composition according to any one of (1) to (4), wherein the water dispersible urethane resin (B) has an elongation at break of 100% or less,

(6) The adhesive composition according to any one of (1) to (5), further comprising 0.1 to 15 parts by weight of fine particles per 100 parts by weight of the total amount of the water dispersible urethane resins (A) and (B) Provided,

(7) An optical film comprising a thermoplastic resin film and an easy-to-adhere layer formed on at least one surface of the thermoplastic resin film, wherein the easy-to-adhere layer comprises the adherence improver composition according to any one of (1) to Wherein the optical film is formed of a transparent material,

(8) The resin film is provided with the optical film according to (7), which is made of a (meth) acrylic resin,

(9) A polarizing plate provided with an optical film according to (7) or (8), an adhesive layer, and a polarizer laminated in this order so that the adhesive layer is in contact with the adhesive layer,

(10) a water-dispersible urethane resin (A) diluted with an aqueous solvent and having a glass transition temperature of less than 60 占 폚, a water-dispersible urethane resin (A) having a glass transition temperature of 60 占 폚 to 120 占 폚, A method for producing an optical film comprising a step of coating a thermosetting resin composition comprising an urethane resin (B) on at least one surface of a thermoplastic resin film to form a coating film, and drying the coating film to form an easy adhesion layer / RTI >

The easily adherent composition of the present invention having the above-described structure can suppress deterioration of the initial performance under high temperature and high humidity, and is excellent in heat and humidity resistance under a harsh environment. In the present specification, the term " (meth) acrylic " is used as methacrylic acid, acrylic acid, or both of them. The term "(meth) acrylonitrile" is also the same.

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

[Composition for facilitating adhesion]

(A) having a glass transition point (hereinafter referred to as " Tg ") of less than 60 deg. C and a water-dispersible urethane resin (A) having a Tg of 60 DEG C or more and 120 DEG C or less, % Or less of water-dispersible urethane resin (B). The adhesive property composition of the present invention is excellent in adhesion in long-term use under high temperature and high humidity by incorporating a urethane resin satisfying such characteristics.

The Tg of the water dispersible urethane resin (A) is less than 60 占 폚. The Tg is preferably from -25 DEG C to less than 60 DEG C, more preferably from -15 DEG C to less than 50 DEG C, further preferably from -15 DEG C to less than 45 DEG C. When the Tg of the water dispersible urethane resin (A) is within the above range, the initial adhesion with the thermoplastic resin film is excellent.

In the present specification, Tg means a temperature at which the loss elastic modulus (E ") in the dynamic viscoelasticity measurement shows the maximum. More specifically, the temperature dependency of the loss elastic modulus E "was measured under the condition of a frequency of 10 Hz and a temperature raising rate of 3 ° C / min using a dynamic viscoelasticity measuring apparatus (Rheogel-E4000 manufactured by Ubitech Co., Ltd.) The temperature at which this maximum value is defined as the glass transition temperature (占 폚).

The water dispersible urethane resin (A) preferably has a breaking elongation of 300% or less. The elongation at break is more preferably 100% or less, and further preferably 50% or less. When the elongation at break of the water dispersible urethane resin (A) is within the above range, adhesion with the thermoplastic resin film is excellent.

The breaking elongation is measured by the following method. First, an aqueous dispersion of the water-dispersible urethane resin was prepared so as to have a solid content of 35% by weight, and the resultant was divided into a container such as a chalet such that the urethane resin had a film thickness of about 500 탆. After drying for 15 hours at room temperature, Hour, and further dried at 120 ° C for 20 minutes to prepare a urethane resin film. Subsequently, this urethane resin film was cut into a size of 15 mm x 200 mm to cut the sample, and then a sample with a target point at an interval of 50 mm at the center was prepared. Then, the sample is mounted on a tensile tester, the distance between the clamps of the tester is set at 100 mm, and the sample is measured at a rate of 200 mm / min until it breaks, and is calculated by the following calculation method. The measurement temperature is 23 占 폚.

Elongation at break (%) = ((distance between target points at breakage - distance between target points before test) / (distance between target points before test)) × 100

The water dispersible urethane resin (B) has a Tg of 60 占 폚 or more and 120 占 폚 or less and a weight gain rate of 20% or less in an aqueous temperature resistance test. The Tg of the water-dispersible urethane resin (B) is preferably 65 占 폚 or more and 115 占 폚 or less, more preferably 70 占 폚 or more and 110 占 폚 or less, further preferably 75 占 폚 or more and 105 占 폚 or less. In addition, the weight increase rate in an aqueous temperature resistance test is preferably 15% or less, and more preferably 10% or less. When the Tg of the water dispersible urethane resin (B) and the weight increase rate are in the above ranges, the adhesiveness in long-term use under high temperature and high humidity is excellent.

The weight increase rate in an internal temperature aqueous test is measured by the following method. First, an aqueous dispersion of the water-dispersible urethane resin was prepared so as to have a solid content of 35% by weight, and the resultant was divided into a container such as a chalet such that the urethane resin had a film thickness of about 500 탆. After drying for 15 hours at room temperature, Hour, and further dried at 120 ° C for 20 minutes to prepare a urethane resin film. Subsequently, this urethane resin film is cut into a size of 20 mm x 40 mm, a sample is cut out, and the weight (W0) of the sample is measured. Thereafter, the sample is immersed in hot water at 40 占 폚 for 24 hours, and the weight (W1) of the sample after immersion is measured and calculated by the following calculation method.

Weight increase rate (%) = ((W1 - W0) / W0) x100

The elongation at break of the water dispersible urethane resin (B) is preferably 100% or less. The elongation at break is more preferably 50% or less, and still more preferably 20% or less. When the elongation at break of the water dispersible urethane resin (B) is within the above range, adhesion with the thermoplastic resin film is excellent. The method of measuring the elongation at break is as described above.

(A / B) ratio of the water-dispersible urethane resin (A) and the water-dispersible urethane resin (B) constituting the easy-to-adhere layer in order to exhibit excellent initial adhesion and excellent adhesion at high temperature and high humidity, ) Is preferably 95: 5 to 40:60. The weight ratio (A / B) is more preferably from 85:15 to 50:50, and still more preferably from 80:20 to 60:40, because further excellent adhesion is obtained.

The water-dispersible urethane resins (A) and (B) are not particularly limited as long as they are water-dispersible urethane resins having the above-mentioned characteristics. For example, Chain urethane prepolymer obtained by reacting a polyol with a chain extender having a free carboxyl group after forming an isocyanate group-terminated prepolymer is subjected to chain elongation in water in the presence of a neutralizing agent and water conversion . The term "water-based" as used herein means that the resin is stably dispersed or emulsified in water. The water-dispersible urethane resins (A) and (B) are preferably those having a carboxyl group in the molecule, and have a carboxyl group, so that they have excellent adhesiveness under prolonged use under high temperature and high humidity.

Examples of the polyisocyanate include tetramethylene diisocyanate, dodecamethylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4- Aliphatic diisocyanates such as trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate and 3-methylpentane-1,5-diisocyanate; isophorone diisocyanate, hydrogenated xylylenedi Alicyclic diisocyanates such as isocyanate, 4,4'-cyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate and 1,3-bis (isocyanatemethyl) cyclohexane; alicyclic diisocyanates such as tolylene diisocyanate , 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate Cyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyldiisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4 Aromatic diisocyanates such as phenylenediisocyanate, aromatic aliphatic diisocyanates such as dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, and alpha, alpha, alpha, alpha-tetramethyl xylylene diisocyanate. have. 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 suitable polyol can be employed. Examples thereof include polyalkylene glycols, polyacrylic polyols, polyester polyols, polyether polyols, polyether ester polyols, polycarbonate polyols and the like. These may be used alone or in combination of two or more.

Examples of the chain extender having a free carboxyl group include dihydroxycarboxylic acid and dihydroxysuccinic acid. Examples of the dihydroxycarboxylic acid include dialkylolalkanoic acids such as dimethylolalkanoic acid (e.g., dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutyric acid, and dimethylolpentanoic acid) . These may be used alone or in combination of two or more.

Examples of the neutralizing agent include ammonia, N-methylmorpholine, triethylamine, dimethylethanolamine, methyldiethanolamine, triethanolamine, morpholine, tripropylamine, ethanolamine, triisopropanolamine, -Methyl-1-propanol, and the like. These may be used alone or in combination of two or more.

Other usable chain extenders include low molecular weight diol compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, furandimethanol, diethylene glycol, triethylene glycol and tetraethylene glycol, A polyether diol compound obtained by addition polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, etc., a dicarboxylic acid such as succinic acid, adipic acid and (anhydrous) phthalic acid, and anhydrides thereof Polyester diols having a hydroxyl group at the terminal thereof, polyhydric alcohols such as trimethylolethane and trimethylolpropane, aminoalcohols such as monoethanolamine, diethanolamine and triethanolamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, Phenylenediamine, toluenediamine, xylenediamine, isophoronediamine, etc. , Diamine compounds of water, ammonia, hydrazine, dibasic acid hydrazide, and the like. These may be used alone or in combination of two or more.

The number-average molecular weight of the water-dispersible urethane resins (A) and (B) is preferably from 5,000 to 600,000, and more preferably from 10,000 to 400,000. The acid value of the water-dispersible urethane resin is preferably 10 or more, more preferably 10 to 50, and particularly preferably 20 to 45.

The easy-to-adhere composition may be diluted with an aqueous solvent in workability in forming an easy-to-adhere layer. Examples of the water-based solvent include water or water and a hydrophilic organic solvent (for example, an alcohol solvent such as methanol, ethanol, isopropyl alcohol, ethylene glycol or propylene glycol; an ester such as ethyl acetate, butyl acetate or gamma -butyrolactone A ketone solvent such as acetone, an ether solvent such as tetrahydrofuran or dioxane, or an aprotic polar solvent such as N-methylpyrrolidone), but water is particularly preferable.

The content of the water-dispersible urethane resin (A) and the water-dispersible urethane resin (B) in the easy-to-adhere composition is not particularly limited and may be set appropriately in consideration of the workability of coating, and is preferably, for example, 1 to 25% By weight, more preferably 3 to 20% by weight, and still more preferably 5 to 15% by weight. When the water dispersible urethane resins (A) and (B) in the easy-to-adhere composition are in the above-mentioned range, they are preferable because of their excellent workability in forming an easy-to-adhere layer. The solid content of the easy-to-adhere composition is preferably 1 to 30% by weight, more preferably 2 to 25% by weight, still more preferably 3 to 20% by weight, to be.

The ready-to-use composition may contain any suitable microparticles, preferably water-dispersible microparticles, depending on the desired function. As the fine particles, both inorganic fine particles and organic fine particles can be used. Examples of the inorganic fine particles include inorganic oxides such as silica, titania, alumina and zirconia, and inorganic oxides such as calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, have. Examples of the organic fine particles include a silicone resin, a fluorine resin, a (meth) acrylic resin, a (meth) acrylonitrile resin and the like. Among them, silica or (meth) acrylonitrile-based resin is preferable. Fine particles made of silica or a (meth) acrylonitrile-based resin have excellent blocking inhibiting ability, excellent transparency, no haze, and no coloring, small. In addition, the strength and adhesion of the adhesion-facilitating layer are lowered by blending the fine particles, but the adhesion-facilitating layer comprising the fine particles of the (meth) acrylonitrile-based resin suppresses the deterioration of the strength and adhesiveness of the adhesion- And the like.

The average particle size of the fine particles is not particularly limited, but is preferably from 1 to 500 nm, more preferably from 50 to 350 nm, and still more preferably from 100 to 300 nm from the viewpoint of maintaining the transparency of the adhesive layer. By using fine particles having such a particle size, it is possible to appropriately form irregularities on the surface of the easy-to-adhere layer to effectively reduce the frictional force on the contact surface between the thermoplastic resin film and the adhesive layer and / or the adhesive layer, can do. The average particle diameter mentioned above means the median diameter (d50) measured by 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 total amount of the water-dispersible urethane resins (A) and (B) in terms of solid content. More preferably from 0.3 to 5 parts by weight, still more preferably from 0.5 to 3 parts by weight. In the case of containing other components than the water-dispersible urethane resins (A) and (B), fine particles may be added to the solid content containing other components.

A crosslinking agent may be added in order to improve the heat and humidity resistance under high temperature and high humidity. As the crosslinking agent, any appropriate crosslinking agent can be employed, and examples thereof include urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, silanol-based and carbodiimide-based ones. In order to accelerate the crosslinking reaction, a catalyst or the like may be appropriately used as required.

The ease of bonding composition may further comprise any suitable additive. Examples of the additives include dispersion stabilizers, thixotropic agents, antioxidants, ultraviolet absorbers, antifoaming agents, thickeners, dispersants, surfactants, catalysts, lubricants and antistatic agents.

[Optical film]

Fig. 1 shows an example of the optical film of the present invention. The optical film (1) shown in Fig. 1 has an easy-to-adhere layer (3) formed on the surface of one side of the thermoplastic resin film (2) with the above- In the optical film of the present invention, an easy adhesion layer may be formed on both surfaces of the thermoplastic resin film.

Examples of the thermoplastic resin constituting the thermoplastic resin film include cellulose resins such as triacetylcellulose, polyester resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins Based resin, a cyclic polyolefin-based resin, a (meth) acrylic-based resin, a polyarylate-based resin, a polystyrene-based resin, and a polyvinyl alcohol-based resin. These may be used alone or in combination of two or more. Among them, the (meth) acrylic resin (hereinafter sometimes abbreviated as ACR) has poor adhesion with the hydrophilic adhesive, and therefore, the effect of the present invention is particularly remarkable when ACR is used.

The Tg of the ACR is preferably 115 占 폚 or higher, more preferably 120 占 폚 or higher, and even more preferably 125 占 폚 or higher. The thermoplastic resin film contains ACR having a Tg of 115 占 폚 or more as a main component, thereby making it excellent in durability. The upper limit of the above-mentioned Tg is not particularly limited, but is preferably 170 占 폚 or less from the viewpoint of moldability and the like.

Examples of the ACR include poly (meth) acrylate such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methacrylate methyl- (meth) acrylate ester copolymer, methyl methacrylate (Meth) acrylic acid methyl-styrene copolymer (MS resin and the like), a polymer having an alicyclic hydrocarbon group (e.g., a methacrylic acid-methyl methacrylate-cyclohexyl copolymer , Methyl methacrylate- (meth) acrylate norbornyl copolymer, and the like). Among them, preferable is poly (meth) acrylate of poly (meth) acrylate such as methyl (meth) acrylate and methacrylate having methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% And an acid methyl resin is more preferable.

Specific examples of the ACR include, for example, "ACRIPETT (registered trademark) VH", "ACRIPTET (registered trademark) VRL20A" manufactured by Mitsubishi Rayon Company, high Tg Meth) acryl-based resin.

ACRs preferably have a ring structure in the main chain in that they have high heat resistance, high transparency and high mechanical strength. Examples of the ACR having a ring structure in the main chain include a resin having a glutaric anhydride structure or a glutarimide structure (WO2007 / 26659, WO2005 / 108438), a maleic anhydride structure or an N- (JP-A-57-153008, JP-A-2007-31537), resins having a lactone ring structure (JP-A-2006-96960, JP-A-2006-171464 , Japanese Unexamined Patent Application Publication No. 2007-63541, Japanese Unexamined Patent Publication No. 2008-191426).

The thermoplastic resin film may contain an additive. Examples of the additives include antioxidants such as hindered phenol, phosphorus and sulfur, stabilizers such as a light stabilizer, a weather stabilizer and a heat stabilizer, a reinforcing material such as glass fiber and carbon fiber, an ultraviolet absorber, a near infrared absorber, Antistatic agents such as anionic, cationic, and ionic surfactants, colorants such as inorganic pigments, organic pigments, and dyes, organic fillers and inorganic fillers, resin modifiers, organic fillers and inorganic fillers, plasticizers, lubricants, antistatic agents, ; A retardation reducing agent; and the like.

The method of producing the thermoplastic resin film is not particularly limited. For example, the thermoplastic resin and other polymers and additives may be thoroughly mixed by any suitable mixing method to prepare a thermoplastic resin composition in advance, Can be molded. Alternatively, the thermoplastic resin and the other polymer or additive may be respectively formed into different solutions and then mixed to form a homogeneous mixed solution, followed by film formation.

In order to produce the thermoplastic resin composition, the film raw material is pre-blended with any suitable mixer such as an omni mixer, for example, and the resulting mixture is extrusion kneaded. In this case, the kneader used for the extrusion kneading is not particularly limited, and any suitable mixer such as an extruder such as a single screw extruder, a twin screw extruder, or a pressurized kneader may be used.

Examples of the film forming method include any suitable film forming method such as a solution casting method (solution casting method), a melt extrusion method, a calendering method, and a compression molding method. Of these film forming methods, the melt extrusion method is preferable.

Examples of the melt extrusion method include a T-die method and an inflation method. The molding temperature is preferably 150 to 350 占 폚, more preferably 200 to 300 占 폚.

When the film is formed by the T-die method, a T-die is attached to the tip of a known single-screw extruder or a twin-screw extruder, the film is formed by the T-die, and then the film is wound to obtain a film on the roll.

The thermoplastic resin film may be either an unstretched film or a stretched film. In the case of a stretched film, either a monoaxially stretched film or a biaxially stretched film may be used. In the case of a biaxially oriented film, either a simultaneous biaxially oriented film or a sequential biaxially oriented film may be used. In the case of biaxially stretching, the mechanical strength is improved and the film performance is improved.

The stretching temperature is preferably in the vicinity of the glass transition temperature of the thermoplastic resin composition as the raw material of the film and is preferably in the range of (Tg - 30 ° C) to (Tg + 100 ° C) ) To (Tg + 80 DEG C). If the stretching temperature is less than (Tg - 30 占 폚), there is a possibility that a sufficient stretching ratio may not be obtained. On the contrary, if the stretching temperature exceeds (Tg + 100 deg. C), the resin composition may flow (flow), and stable drawing may not be possible.

The stretching ratio defined by the area ratio is preferably 1.1 to 25 times, more preferably 1.3 to 10 times. If the draw ratio is less than 1.1 times, there is a possibility that the toughness resulting from the draw may not be improved. If the draw ratio exceeds 25 times, there is a possibility that the effect of increasing the draw ratio (improvement in toughness) may not be recognized.

The stretching speed is preferably 10 to 20,000% / min, more preferably 100 to 10,000% / min, in one direction. If the drawing speed is less than 10% / min, it takes time to obtain a sufficient drawing magnification, which may increase the manufacturing cost. If the stretching speed exceeds 20,000% / min, there is a possibility that the stretched film is broken.

The thermoplastic resin film can be subjected to a heat treatment (annealing) or the like after the stretching treatment in order to stabilize the optical isotropy and the mechanical properties. As the condition of the heat treatment, any appropriate condition can be employed.

The thickness of the thermoplastic resin film is preferably 5 to 200 占 퐉, more preferably 10 to 100 占 퐉. If the thickness is less than 5 占 퐉, there is a fear that sufficient strength as an optical film can not be obtained. If the thickness exceeds 200 占 퐉, the transparency is lowered, and the film may not be suitable for use as an optical film.

The thickness of the easy-to-adhere layer can be set to any appropriate value. Preferably 0.1 to 10 占 퐉, more preferably 0.1 to 5 占 퐉, and particularly preferably 0.2 to 1 占 퐉. By setting to such a range, adhesion with other functional films is excellent, and the occurrence of a retardation in the easy-to-adhere layer can be suppressed.

Various functional layers may be formed on the surface of the optical film opposite to the surface on which the adhesion-facilitating layer is formed, if necessary. The functional layer may be formed of any one of antistatic layer, antireflection layer, hard coat layer, ultraviolet shielding layer, heat ray shielding layer, antireflection layer, antistatic layer, antistatic layer, antistatic layer, adhesive layer, adhesive layer, antiglare layer An electromagnetic wave shielding layer, a gas barrier layer, and the like.

The optical film can be used, for example, as a polarizer protective film, a retardation film, a viewing angle compensation film, a light diffusion film, a reflection film, an antireflection film, an antiglare film, a luminance enhancement film and a conductive film for a touch panel. Among them, it is particularly preferable to use them 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 is provided on the surface of the easy-to-adhere layer of the optical film 1 having the easy-to-adhere layer 3 formed on the one surface of the thermoplastic resin film 2 with the above- And has a structure in which the polarizers 6 are laminated via the adhesive 5. Although not shown, the polarizing plate 10 may have a protective film laminated on the opposite side of the optical film 1 of the polarizer 6 with an adhesive layer interposed therebetween.

As the polarizer, any suitable polarizer may be employed depending on the purpose. For example, a hydrophilic polymer film such as a polyvinyl alcohol film, a partially porous polyvinyl alcohol film, and an ethylene-vinyl acetate copolymerization system partially saponified film may be produced by adsorbing a dichromatic substance such as iodine or a dichroic dye to a single- Stretched polyvinyl alcohol films, stretched polyvinyl alcohol films, polyvinyl alcohol dehydrated films, polyvinyl chloride dehydrochlorinated films, and the like. Among them, a polarizer obtained by adsorbing a dichromatic substance such as iodine on a polyvinyl alcohol film is uniaxially stretched is particularly preferable because of high polarizing dichroism ratio. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 mu m.

As the adhesive forming the adhesive layer, any appropriate adhesive may be employed. Preferably, the adhesive layer is formed of an adhesive composition comprising a polyvinyl alcohol-based resin.

As the protective film to be formed on the opposite side of the optical film 1 of the polarizer 6, any appropriate protective film may be employed and it may be formed of the same material as the aforementioned thermoplastic resin.

[Image display device]

The image display apparatus of the present invention comprises the above-described polarizing plate. Specific examples of the image display device include a self-emission type display device such as an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED), and a liquid crystal display .

[Production method of optical film]

(A) which is diluted with an aqueous solvent and has a glass transition temperature (Tg) of less than 60 DEG C and a water-dispersible urethane resin (A) which has a glass transition temperature (B) in an aqueous temperature-resistant aqueous test is 20% or less, is applied to at least one surface of the thermoplastic resin film to form a coating film (coating step), and then the coating film To form an easy-to-adhere layer (drying step).

Any suitable method may be employed as a method of applying the composition for easy adhesion in the coating step. Examples of the coating method include a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slot orifice coating method, a curtain coating method, and a fountain coating method. The thickness of the coating film formed in the coating step can be appropriately adjusted in accordance with the thickness required when the coating film becomes an adhesion-facilitating layer.

The surface to which the composition for easy adhesion in the thermoplastic resin film is applied is preferably subjected to surface treatment. The surface treatment is preferably a corona discharge treatment or a plasma treatment. By performing the corona discharge treatment or the plasma treatment, the adhesion between the thermoplastic resin film and the easy adhesion layer can be improved.

The drying step is not particularly limited, and conventionally known methods can be used. The drying temperature is typically 50 占 폚 or higher, preferably 90 占 폚 or higher, more preferably 110 占 폚 or higher. By setting the drying temperature in such a range, an optical film excellent in color resistance (particularly under high temperature and high humidity) can be obtained. The upper limit of the drying temperature is preferably 200 占 폚 or lower, more preferably 180 占 폚 or lower.

When the thermoplastic resin film is stretched, the stretching may be carried out before the easy-to-adhere layer is formed, or after the easy-adhesion layer is formed. Further, the formation of the adhesion-facilitating layer and the stretching of the thermoplastic resin film may be performed at the same time.

When the formation of the adhesion-facilitating layer and the stretching of the thermoplastic resin film are simultaneously performed, for example, after the application step, the thermoplastic resin film having the coating film of the composition for easy adhesion can be stretched under a heating atmosphere. The applied film of the easy-to-adhere composition formed on the surface of the thermoplastic resin film is dried by the heat applied to the film for stretching, and becomes an easy-to-adhere layer. In this case, the stretching treatment of the film and the drying of the easy-to-adhere composition can be carried out at the same time, which is preferable in terms of productivity.

Example

Hereinafter, the present invention will be described in more detail by examples. The present invention is not limited to the following examples.

The following materials were used as raw materials. Table 1 shows the glass transition temperature, the elongation at break, and the weight increase rate of the water resistance test at room temperature with respect to the property values of the water dispersible urethane resins (A) and (B).

<Water-dispersible urethane resin (A)>

Emulsion of water-dispersible urethane resin (A-1) [Superflex (registered trademark) 210 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 35%

Emulsion of water-dispersible urethane resin (A-2) (Superflex 占 150, solid content 30% by weight, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

Emulsion of water-dispersible urethane resin (A-3) [Superflex (registered trademark) 420, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 32%

(Emulsion of water-dispersible urethane resin (A-4) (Superflex (registered trademark) 460, solid content: 38% by weight, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

<Water-dispersible urethane resin (B)>

Emulsion of water-dispersible urethane resin (B-1) (Superflex 占 130, solid content 35% by weight, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

Emulsion of a water dispersible urethane resin (B-2) (Superflex (registered trademark) 870, solid content 30% by weight, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

&Lt; Particles &gt;

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

Examples 1 to 4 and Comparative Examples 1 to 8

1. Preparation of the adhesive composition

The raw emulsion was selected and mixed so that each component shown in Table 2 contained the solid amount (unit: parts by weight) shown in Table 2, and an easy-to-adhere composition was prepared. Further, ion-exchanged water was used as an aqueous solvent, and the solid content of the easy-to-adhere composition was adjusted so as to be finally 8 wt%.

2. Manufacture of optical film

(Φ = 20.0 mm, L / D = 25) of a methacrylic resin [Tg: 135 ° C., melt viscosity: 700 Pa · s (temperature: 270 ° C., shear rate: And a coat hanger type T die (width 150 mm) at 280 DEG C, and the molten resin was discharged onto a cooling roll maintained at 110 DEG C to form a methacrylic resin film having a thickness of 100 mu m . Next, the easy-to-adhere composition obtained above was applied to one surface of the methacrylic resin film using a bar coater, then put in a hot air drier and dried at 100 ° C for 90 seconds. Then, the film was subjected to uniaxial stretching (stretching magnification: 2.5 times) using a table stretcher, and an optical film having an easy adhesion layer with a thickness of 0.3 mu m was produced on the surface of a methacrylic resin film having a thickness of 40 mu m.

3. Preparation of Polarizer

The polyvinyl alcohol-based adhesive composition was coated on the easy-to-adhere side of the optical film obtained above. A polyvinyl alcohol-based adhesive composition was applied to one side of a triacetylcellulose film (protective film) having a saponification treatment and a thickness of 40 탆. Next, an optical film and a protective film were laminated on both sides of a polarizer having a thickness of 30 탆 with a polyvinyl alcohol adhesive application layer interposed therebetween. The resulting laminate was put in a hot air dryer (70 캜) and dried for 5 minutes, . A reference polarizing plate for evaluation in which triacetyl cellulose protective films were formed on both sides of the polarizer was prepared in the same manner.

The following evaluations were performed on the polarizing plate obtained above. The evaluation results are shown in Table 2.

(1) Initial adhesion

A test piece having dimensions of 25 mm x 250 mm was cut from the polarizing plate obtained above, and the surface of the optical film of the test piece was adhered to the glass plate, and a measurement sample was obtained. Thereafter, a cut was made between the polarizer of the sample and the optical film, the polarizer and the protective film were held, and the peel adhesion strength at 90 degrees was measured according to the floating roller method of Japanese Industrial Standard JAI 13-1996. The peel adhesion strength was also measured on the reference polarizing plate under the same conditions. From the measurement results, the peel adhesion strength was evaluated according to the following criteria.

&Amp; cir &amp;: Excellent peel adhesion strength than the reference polarizing plate

&Amp; cir &amp;: peeling adhesion strength with the reference polarizing plate is equal

?: Peeling adhesive strength is lower than that of the reference polarizing plate

X: Measurement is impossible because it is not closely attached

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

The peel adhesion strength was measured in the same manner as in the evaluation of the initial adhesion, except that the measurement sample obtained in the same manner as above was placed in a thermo-hygrostat at a temperature of 60 ° C and a humidity of 90% RH for 250 hours and 500 hours of heat treatment Respectively. From the measurement results, the peel adhesion strength was evaluated according to the following criteria.

&Amp; cir &amp;: Excellent peel adhesion strength than the reference polarizing plate

&Amp; cir &amp;: peeling adhesion strength with the reference polarizing plate is equal

?: Peeling adhesive strength is lower than that of the reference polarizing plate

X: Measurement is impossible because it is not closely attached

(3) Humidity resistance (80 캜, 90% RH)

The peel adhesion strength was measured in the same manner as in the evaluation of the initial adhesion, except that the measurement sample obtained in the same manner as above was placed in a thermo-hygrostat at a temperature of 80 캜 and a humidity of 90% RH for 100 hours of heat treatment. From the measurement results, the peel adhesion strength was evaluated according to the following criteria.

&Amp; cir &amp;: Excellent peel adhesion strength than the reference polarizing plate

&Amp; cir &amp;: peeling adhesion strength with the reference polarizing plate is equal

?: Peeling adhesive strength is lower than that of the reference polarizing plate

X: Measurement is impossible because it is not closely attached

As shown in Table 2, the water dispersible urethane resin (A) having a Tg of less than 60 占 폚 and the water dispersible urethane resin (B) having a Tg of 60 占 폚 or more and 120 占 폚 or less and a weight gain rate of 20% The optical films of Examples 1 to 4 using the easy-to-adhere layer having excellent adhesiveness were excellent in initial adhesion and excellent in adhesiveness in long-term use under high temperature and high humidity. On the other hand, as shown in Table 2, the optical films of Comparative Examples 1 to 6, which contained only the water-dispersible urethane resin (A) having a Tg of less than 60 占 폚, exhibited inferior adhesiveness in prolonged use under high temperature and high humidity. The optical films of Comparative Examples 7 and 8, which had a Tg of 60 ° C or more and 120 ° C or less and which contained only the water-dispersible urethane resin (B) having a weight gain ratio of 20% or less in the water temperature resistance test, But the initial adhesion was inferior.

Claims (10)

(A) having a glass transition temperature of lower than 60 占 폚 and a water-dispersible urethane resin (B) having a glass transition temperature of 60 占 폚 or higher and 120 占 폚 or lower and a weight increase rate of 20% / RTI &gt; The method according to claim 1,
Wherein the weight ratio of the water dispersible urethane resin (A) to the water dispersible urethane resin (B) is in the range of 95: 5 to 40: 60. 3. The method according to claim 1 or 2,
Wherein the water dispersible urethane resin (A) has a glass transition temperature of -25 캜 or higher. 4. The method according to any one of claims 1 to 3,
Wherein the water dispersible urethane resin (A) has an elongation at break of 300% or less. 5. The method according to any one of claims 1 to 4,
Wherein the water dispersible urethane resin (B) has an elongation at break of 100% or less. 6. The method according to any one of claims 1 to 5,
Further comprising 0.1 to 15 parts by weight of fine particles per 100 parts by weight of the total amount of the water dispersible urethane resins (A) and (B). An optical film comprising a thermoplastic resin film and an easy-to-adhere layer formed on at least one surface of the thermoplastic resin film, wherein the easy-to-adhere layer is formed from the adherence-easy composition according to any one of claims 1 to 6 Wherein the optical film has a refractive index different from that of the optical film. 8. The method of claim 7,
The resin film is made of a (meth) acrylic resin. 8. A polarizing plate comprising the optical film according to claim 7 or 8, an adhesive layer, and a polarizer laminated in this order such that the adhesive layer is in contact with the adhesive layer. (A) diluted with an aqueous solvent and having a glass transition temperature of less than 60 占 폚, a water dispersible urethane resin having a glass transition temperature of 60 占 폚 or more and 120 占 폚 or less and a weight gain rate of 20% B) on at least one surface of a thermoplastic resin film to form a coated film; and drying the coated film to form an easy-to-adhere layer.

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