JPWO2016088633A1 - Easy-adhesive composition, optical film using the same, and production method thereof - Google Patents

Abstract

An object of the present invention is to provide an easy-adhesive composition that can suppress deterioration of initial performance during long-term use under high temperature and high humidity, and that can also satisfy moisture and heat resistance in a harsher environment, and an optical film using the same. And A water dispersible urethane resin (A) having a glass transition temperature of less than 60 ° C. and a water dispersibility having a glass transition temperature of 60 ° C. or more and 120 ° C. or less and a weight increase rate in a warm water resistance test of 20% or less. An easy-adhesive composition comprising a urethane resin (B). An optical film in which an easy-adhesion layer comprising the easy-adhesion composition is provided on at least one surface of a thermoplastic resin film. [Selection] Figure 1

Description

  The present invention relates to an easy-adhesion composition and an optical film having an easy-adhesion layer composed of the easy-adhesion composition. Furthermore, this invention relates to the manufacturing method of this optical film, a polarizing plate provided with this optical film, and an image display apparatus.

  Acrylic resin films formed from (meth) acrylic polymers typified by polymethyl methacrylate are known to have excellent optical properties such as light transmittance, as well as excellent balance between mechanical strength and moldability. ing. For this reason, the acrylic resin film is applied to an optical film incorporated 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 where it is laminated with another functional film. For example, when an optical film is used as a polarizer protective film, it is laminated on at least one surface of the polarizer via a hydrophilic adhesive layer. 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 inferior in adhesiveness with a hydrophilic adhesive and has a problem that adhesiveness with a polarizer is not sufficient. In view of this, a method has been proposed in which an easy-adhesion layer mainly composed of an auxiliary-adhesive resin such as polyester, acrylic, or urethane is provided on the surface of the acrylic resin film to impart easy adhesion to the acrylic resin film.

  On the other hand, portable devices using an image display device such as an LCD are recently used in various environments, indoors and outdoors, and may require moisture and heat resistance that can withstand high temperature and high humidity environments. A polarizing plate used for such an application is required to have high adhesion that does not cause delamination even under high temperature and high humidity.

  Thus, JP 2009-274390 A discloses an aqueous structure containing an acid structure on the surface of an acrylic resin film as a laminated film having good thermal adhesion when exposed to high temperatures and having good adhesion to a polarizer. It describes that an easy-adhesion layer containing an aqueous urethane resin formed by neutralizing a part of an acid structure contained in a urethane resin with a nonvolatile base is described. Japanese Patent Application Laid-Open No. 2009-205135 emulsifies a monomer composition containing polyalkylene glycol (meth) acrylate on the surface of an acrylic resin film as a polarizer protective film having excellent adhesion to a polarizer under high temperature and high humidity. It describes that an easy-adhesion layer is formed with an aqueous (meth) acrylic resin dispersion obtained by polymerization.

  However, although the optical film having an easy-adhesion layer disclosed in the above document initially exhibits good adhesion, a decrease in adhesion with a polarizer is inevitable when used for a long time under high temperature and high humidity. There is a problem that the initial performance (initial adhesion) is not maintained for a long time. Furthermore, the optical film having the easy-adhesion layer disclosed in the above document is used in a long time use under high temperature (for example, 80 ° C.) or high temperature and high humidity (for example, 40 to 60 ° C., 60 to 95% RH). Although the heat-and-moisture resistance is satisfactory, the heat-and-moisture resistance in a harsher environment (for example, 80 ° C. and 90% RH) is not satisfactory.

  The present invention has been made in view of such problems, and is an easy-adhesive composition that can suppress deterioration in initial performance in long-term use under high temperature and high humidity, and can also satisfy moisture and heat resistance in a harsh environment. An object is to provide an optical film using the same.

According to the present invention,
(1) A water dispersible urethane resin (A) having a glass transition temperature of less than 60 ° C. and a water dispersible urethane having a glass transition temperature of 60 ° C. or more and 120 ° C. or less and a weight increase rate in a warm water resistance test of 20% or less. An easy-adhesive composition comprising resin (B) is provided,
(2) The easy-adhesion 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 easy-adhesion composition according to (1) or (2), wherein the water-dispersible urethane resin (A) has a glass transition temperature of -25 ° C or higher.
(4) The easy-adhesion composition according to any one of (1) to (3), wherein the elongation at break of the water-dispersible urethane resin (A) is 300% or less,
(5) The easily adhesive composition according to any one of (1) to (4), wherein the elongation at break of the water-dispersible urethane resin (B) is 100% or less,
(6) The easy-adhesion composition according to any one of (1) to (5), further comprising 0.1 to 15 parts by weight of fine particles with respect to a total of 100 parts by weight of the water-dispersible urethane resins (A) and (B). Things are provided,
(7) An optical film including a thermoplastic resin film and an easy adhesion layer provided on at least one surface of the thermoplastic resin film, wherein the easy adhesion layer is any one of (1) to (6) An optical film characterized in that it is formed from the easy-adhesive composition described above,
(8) The optical film according to (7), wherein the resin film is made of a (meth) acrylic resin,
(9) Polarized light in which the optical film, the adhesive layer, and the polarizer according to (7) or (8) are laminated in this order so that the easy-adhesion layer is in contact with the adhesive layer Board is provided,
(10) A water-dispersible urethane resin (A) diluted with an aqueous solvent and having a glass transition temperature of less than 60 ° C., a glass transition temperature of 60 ° C. to 120 ° C., and a weight increase rate of 20% in a warm water resistance test Applying an easy-adhesive composition containing the water-dispersible urethane resin (B) below to at least one surface of a thermoplastic resin film to form a coating film, and drying the coating film to facilitate adhesion A method for producing an optical film comprising a step of forming a layer is provided.

  The easy-adhesion composition of the present invention having the above-described configuration suppresses deterioration of initial performance under high temperature and high humidity, and is excellent in heat and humidity resistance under a harsher environment. In the present specification, the term “(meth) acryl” is used as a general term for methacryl, acryl, or both. The same applies to the term “(meth) acrylonitrile”.

It is sectional drawing which shows an example of the optical film of this invention typically. It is sectional drawing which shows typically an example of the polarizing plate of this invention.

[Easily adhesive composition]
The easy-adhesion composition of the present invention comprises a water-dispersible urethane resin (A) having a glass transition point (hereinafter referred to as Tg) of less than 60 ° C., a weight increase rate in a hot water resistance test with a Tg of 60 ° C. to 120 ° C. Containing 20% or less of a water-dispersible urethane resin (B). The easy-adhesion composition of this invention is excellent in the adhesiveness in long-time use under high temperature, high humidity by mix | blending the urethane resin which satisfies such a characteristic.

  The Tg of the water dispersible urethane resin (A) is less than 60 ° C. Tg is preferably −25 ° C. or more and less than 60 ° C., more preferably −15 ° C. or more and less than 50 ° C., and further preferably −15 ° C. or more and less than 45 ° C. If Tg of water-dispersible urethane resin (A) is the said range, it will be excellent in initial stage adhesiveness with a thermoplastic resin film.

  In the present specification, Tg means a temperature at which the loss elastic modulus (E ″) has a maximum in the dynamic viscoelasticity measurement. More specifically, the dynamic viscoelasticity measuring device (Rheogel- manufactured by UBM Co., Ltd.) E4000) was used to measure the temperature dependence of the loss modulus E ″ under the conditions of a frequency of 10 Hz and a heating rate of 3 ° C./min. The temperature at which the obtained E ″ curve becomes a maximum was determined as the glass transition temperature ( ° C).

  The water dispersible urethane resin (A) preferably has a breaking elongation of 300% or less. The breaking elongation 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 in the above range, the adhesiveness with the thermoplastic resin film is excellent.

The breaking elongation is measured by the following method. First, an aqueous dispersion of a water-dispersible urethane resin is prepared so as to have a solid content of 35% by weight, separated into containers such as a petri dish so that the thickness of the urethane resin after drying is about 500 μm, and dried at room temperature for 15 hours. Then, it is dried at 80 ° C. for 6 hours and further at 120 ° C. for 20 minutes to produce a urethane resin film. Next, the urethane resin film is cut into a size of 15 mm × 200 mm to cut out a sample, and then a sample in which marks are written at intervals of 50 mm in the center is created. Then, the sample is attached to a tensile tester, the distance between the grips of the tester is set to 100 mm, the sample is measured until it breaks at a speed of 200 mm / min, and is calculated by the following calculation method. The measurement temperature is 23 ° C.
Elongation at break (%) = ((distance between gauge points at break−distance between gauge points before test) / (distance between gauge points before test)) × 100

  The water-dispersible urethane resin (B) has a Tg of 60 ° C. or more and 120 ° C. or less and a weight increase rate of 20% or less in the warm water resistance test. The Tg of the water dispersible urethane resin (B) is preferably 65 ° C. or higher and 115 ° C. or lower, more preferably 70 ° C. or higher and 110 ° C. or lower, and further preferably 75 ° C. or higher and 105 ° C. or lower. Moreover, it is preferable that the weight increase rate in a warm water-resistant test is 15% or less, More preferably, it is 10% or less. When the Tg and the weight increase rate of the water-dispersible urethane resin (B) are in the above ranges, the adhesiveness for long time use under high temperature and high humidity is excellent.

The weight increase rate in the hot water resistance test is measured by the following method. First, an aqueous dispersion of a water-dispersible urethane resin is prepared so as to have a solid content of 35% by weight. Then, it is dried at 80 ° C. for 6 hours and further at 120 ° C. for 20 minutes to produce a urethane resin film. Next, the urethane resin film is cut into a size of 20 mm × 40 mm to cut out a sample, and the weight (W0) of the sample is measured. Thereafter, the sample is immersed in warm water at 40 ° C. for 24 hours, the sample weight (W1) after the immersion is measured, and the following calculation method is used.
Weight increase rate (%) = ((W1-W0) / W0) × 100

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

  The water-dispersible urethane resin (A) and the water-dispersible urethane resin that constitute the easy-adhesion layer in order to exhibit excellent initial adhesion and excellent adhesion in long-term use under high temperature and high humidity. The weight ratio (A / B) to (B) is preferably 95: 5 to 40:60. The weight ratio (A / B) is more preferably 85:15 to 50:50, still more preferably 80:20 to 60:40, because more excellent adhesion can be 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-described characteristics. For example, the organic solvent is inert to isocyanate and compatible with water. In the presence of a neutralizing agent, a linear urethane prepolymer obtained by reacting a polyisocyanate with a polyol to form an isocyanate group-terminated prepolymer and then reacting with a chain extender having a free carboxyl group in water Thus, it can be obtained by making it chain-extending with water and at the same time making it aqueous. The term “water-based” as used herein means that the resin is stably dispersed or emulsified in water. Moreover, it is preferable that water-dispersible urethane resin (A) and (B) has a carboxyl group in a molecule | numerator, and it is excellent in the adhesiveness in long-time use under high temperature, high humidity by having a carboxyl group.

  Examples of polyisocyanates include tetramethylene diisocyanate, dodecamethylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. Aliphatic diisocyanates such as 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate; isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-cyclohexylmethane diisocyanate, 1,4- Cycloaliphatic diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, etc. Cyanate; tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1 , 5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate and other aromatic diisocyanates; dialkyl diphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α, α, α, α-tetramethylxyl Examples include aromatic aliphatic diisocyanates such as range isocyanate. These can 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 adopted. For example, polyalkylene glycol, polyacryl polyol, polyester polyol, polyether polyol, polyether ester polyol, polycarbonate polyol and the like can be mentioned. These can 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 dialkyrol alkanoic acids such as dimethylolalkanoic acid (for example, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolpentanoic acid). These can 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, 2-amino-2-methyl-1 -Propanol etc. are mentioned. These can be used alone or in combination of two or more.

  Further, other usable chain extenders include low molecular weight diol compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, furan methanol, diethylene glycol, triethylene glycol, tetraethylene glycol, and the like. Polyether diol compounds obtained by addition polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, etc .; obtained from the above low molecular weight diol compounds and dicarboxylic acids such as (anhydrous) succinic acid, adipic acid, (anhydrous) phthalic acid, and their anhydrides Polyester diols having a hydroxyl group at the terminal; polyhydric alcohols such as trimethylolethane and trimethylolpropane; amino alcohols such as monoethanolamine, diethanolamine and triethanolamine Le ethylenediamine, propylene diamine, butylene diamine, hexamethylene diamine, phenylene diamine, toluene diamine, xylene diamine, diamine compounds such as isophoronediamine; water, ammonia, hydrazine, may be mentioned dibasic acid hydrazide and the like. These can be used alone or in combination of two or more.

  The number average molecular weights of the water dispersible urethane resins (A) and (B) are preferably 5000 to 600000, more preferably 10000 to 400000. 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-adhesion composition may be diluted with an aqueous solvent in view of workability when forming the easy-adhesion layer. Examples of the aqueous solvent include water or water and hydrophilic organic solvents (for example, alcohol solvents such as methanol, ethanol, isopropyl alcohol, ethylene glycol, and propylene glycol; ester solvents such as ethyl acetate, butyl acetate, and γ-butyrolactone; A mixed solvent with a ketone solvent such as acetone; an ether solvent such as tetrahydrofuran and dioxane; and an aprotic polar solvent such as N-methylpyrrolidone) can be used, but water is particularly preferable.

  Content of water dispersible urethane resin (A) and (B) in an easily bonding composition is not specifically limited, What is necessary is just to set suitably considering application workability | operativity etc., for example, 1 to 25 weight% is preferable. More preferably, it is 3 to 20% by weight, and further preferably 5 to 15% by weight. If the water-dispersible urethane resins (A) and (B) in the easy-adhesive composition are in the above ranges, it is preferable because workability at the time of forming the easy-adhesive layer is excellent. Further, the solid content of the easy-adhesive composition may be appropriately set in consideration of coating workability and the like, but is preferably 1 to 30% by weight, more preferably 2 to 25% by weight, and further preferably 3 to 20% by weight. %.

  The easy-adhesion composition can contain any appropriate fine particles, preferably water-dispersible fine particles, in accordance with a desired function. As the fine particles, either inorganic fine particles or organic fine particles can be used. Examples of the inorganic fine particles include inorganic oxides such as silica, titania, alumina, zirconia, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, and the like. Can be mentioned. Examples of the organic fine particles include silicone resins, fluorine resins, (meth) acrylic resins, (meth) acrylonitrile resins, and the like. Among these, silica or (meth) acrylonitrile resin is preferable. Fine particles made of silica or (meth) acrylonitrile-based resin are excellent in blocking suppression ability, excellent in transparency, do not cause haze, and are not colored, so that the easy-contact layer has less influence on optical properties. In addition, the strength and adhesion of the easy-adhesion layer are reduced by adding fine particles, but the easy-adhesion layer containing fine particles made of (meth) acrylonitrile resin is the strength and adhesion of the easy-adhesion layer. It is particularly preferable because it is possible to suppress the decrease in the thickness.

  Although the average particle diameter of microparticles | fine-particles is not specifically limited, From a viewpoint of maintaining the transparency of an easily bonding layer, Preferably it is 1-500 nm, More preferably, it is 50-350 nm, More preferably, it is 100-300 nm. By using fine particles of such a particle size, irregularities are appropriately formed on the surface of the easy-adhesion layer, and the frictional force at the contact surface between the thermoplastic resin film and the easy-adhesion layer and / or the easy-adhesion layer is effectively reduced. It can reduce and blocking can be suppressed. The above average particle diameter means a 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 with respect to a total of 100 parts by weight of the water-dispersible urethane resins (A) and (B) in terms of solid content. More preferably, it is 0.3-5 weight part, More preferably, it is 0.5-3 weight part. In addition, what is necessary is just to mix | blend microparticles | fine-particles with respect to solid content also including other components, when other components other than water-dispersible urethane resin (A) and (B) are included.

  The easy-adhesion composition may contain a crosslinking agent in order to improve the heat and humidity resistance under high temperature and high humidity. Any appropriate crosslinking agent can be adopted as the crosslinking agent, and examples thereof include urea, epoxy, melamine, isocyanate, oxazoline, silanol, and carbodiimide. Moreover, in order to promote a crosslinking reaction, you may use a catalyst etc. suitably as needed.

  The easy adhesion composition can further comprise any suitable additive. Examples of the additive include a dispersion stabilizer, a thixotropic agent, an antioxidant, an ultraviolet absorber, an antifoaming agent, a thickener, a dispersant, a surfactant, a catalyst, a lubricant, and an antistatic agent.

[Optical film]
FIG. 1 shows an example of the optical film of the present invention. An optical film 1 shown in FIG. 1 has an easy adhesion layer 3 formed from the above-mentioned easy adhesion composition on one surface of a thermoplastic resin film 2. 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 triacetyl cellulose, polyester resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, Examples include cyclic polyolefin resins, (meth) acrylic resins, polyarylate resins, polystyrene resins, and polyvinyl alcohol resins. These can be used alone or in combination of two or more. Among these, the (meth) acrylic resin (hereinafter sometimes abbreviated as ACR) is inferior in adhesiveness with a hydrophilic adhesive, and therefore the effect of the present invention is particularly remarkable when ACR is used.

  The TCR of ACR is preferably 115 ° C. or higher, more preferably 120 ° C. or higher, and still more preferably 125 ° C. or higher. The thermoplastic resin film can be made excellent in durability by containing ACR having a Tg of 115 ° C. or higher as a main component. The upper limit of Tg is not particularly limited, but is preferably 170 ° C. or lower from the viewpoint of moldability and the like.

  As ACR, for example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate -Acrylic acid ester- (meth) acrylic acid copolymer, methyl (meth) acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-methacrylic acid) Acid cyclohexyl copolymer resistance, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Among these, poly (meth) acrylate C1-6 alkyl such as methyl poly (meth) acrylate is preferable, and methacryl having methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is preferable. An acid methyl resin is more preferable.

  Specific examples of ACR include, for example, “Acrypet (registered trademark) VH”, “Acrypet (registered trademark) VRL20A” manufactured by Mitsubishi Rayon Co., Ltd., high Tg (meta) obtained by intramolecular crosslinking and intramolecular cyclization reaction. An acrylic resin is mentioned.

  ACR preferably has a ring structure in the main chain in that it has 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-substituted maleimide structure. Resins (Japanese Patent Laid-Open Nos. 57-153008 and 2007-31537) and resins having a lactone ring structure (Japanese Patent Laid-Open Nos. 2006-96960, 2006-171464, and 2007-63541) JP, 2008-191426, A).

  The thermoplastic resin film may contain an additive. Examples of additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat stabilizers and other stabilizers; reinforcing materials such as glass fibers and carbon fibers; ultraviolet rays Absorbers; Near infrared absorbers; Flame retardants; Antistatic agents such as anionic, cationic and nonionic surfactants; Colorants such as inorganic pigments, organic pigments and dyes; Organic fillers and inorganic fillers; Resin modification Agents; organic fillers and inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants;

  The method for producing the thermoplastic resin film is not particularly limited. For example, the thermoplastic resin and other polymers and additives are sufficiently mixed by any appropriate mixing method and heated in advance. From the plastic resin composition, it can be formed into a film. Alternatively, the thermoplastic resin and other polymers, additives, and the like may be made into separate solutions and mixed to form a uniform mixed solution, and then formed into a film.

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

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

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

  When forming a film by the T-die method, a T-die is attached to the tip of a known single-screw extruder or twin-screw extruder, a film is formed by the T die, and then the film is wound to form a roll. A film can be obtained.

  The thermoplastic resin film may be an unstretched film or a stretched film. In the case of a stretched film, either a uniaxially stretched film or a biaxially stretched film may be used. In the case of a biaxially stretched film, either a simultaneous biaxially stretched film or a sequential biaxially stretched film may be used. In the case of biaxial 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 which is a film raw material, specifically, preferably (Tg-30 ° C) to (Tg + 100 ° C), more preferably (Tg-20). ° C) to (Tg + 80 ° C). If the stretching temperature is less than (Tg-30 ° C), a sufficient stretching ratio may not be obtained. On the other hand, when the stretching temperature exceeds (Tg + 100 ° C.), the resin composition may flow and stable stretching may not be performed.

  The draw ratio defined by the area ratio is preferably 1.1 to 25 times, more preferably 1.3 to 10 times. There exists a possibility that it may not lead to the improvement of the toughness accompanying extending | stretching that a draw ratio is less than 1.1 times. When the draw ratio exceeds 25 times, there is a possibility that the effect of only increasing the draw ratio (improvement of toughness) is not recognized.

  The stretching speed is unidirectional, preferably 10 to 20,000% / min, more preferably 100 to 10,000% / min. When the stretching speed is less than 10% / min, it takes time to obtain a sufficient stretching ratio, and the production cost may increase. If the stretching speed exceeds 20,000% / min, the stretched film may be broken.

  The thermoplastic resin film can be subjected to heat treatment (annealing) or the like after the stretching treatment in order to stabilize its optical isotropy and mechanical properties. Arbitrary appropriate conditions can be employ | adopted for the conditions of heat processing.

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

  The thickness of the easy adhesion layer can be set to any appropriate value. Preferably it is 0.1-10 micrometers, More preferably, it is 0.1-5 micrometers, Most preferably, it is 0.2-1 micrometers. By setting to such a range, it is excellent in adhesiveness with another functional film, and it can suppress that a phase difference expresses in an easily bonding layer.

  Various functional layers may be formed on the surface of the optical film opposite to the surface on which the easy adhesion layer is formed, if necessary. The functional layer is, for example, an antistatic layer, an adhesive layer, an adhesive layer, an easy adhesion layer, an antiglare layer (non-glare) layer, an antifouling layer such as a photocatalyst layer, an antireflection layer, a hard coat layer, an ultraviolet shielding layer, A heat ray shielding layer, an electromagnetic wave shielding layer, a gas barrier layer, etc. are mentioned.

  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 reflection film, an antireflection film, an antiglare film, a brightness enhancement film, and a conductive film for a touch panel. Of these, the use as a polarizer protective film is particularly preferable.

[Polarizer]
Next, an example of the polarizing plate of the present invention will be described. A polarizing plate 10 shown in FIG. 2 has an adhesive 5 on the surface of the optical film 1 having the easy adhesion layer 3 formed from the above-mentioned easy adhesion composition on one surface of the thermoplastic resin film 2. The polarizer 6 has a stacked structure. Although not shown, the polarizing plate 10 may have a protective film laminated via an adhesive layer on the opposite side of the polarizer 6 from the optical film 1.

  Any appropriate polarizer can be adopted as the polarizer depending on the purpose. For example, a dichroic substance such as iodine or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film or an ethylene-vinyl acetate copolymer partially saponified film. And polyene-based oriented films such as a uniaxially stretched product, a polyvinyl alcohol dehydrated product and a polyvinyl chloride dehydrochlorinated product. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film and uniaxially stretching is particularly preferable because of its high polarization dichroic ratio. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 μm.

  Arbitrary appropriate adhesives can be employ | adopted as an adhesive agent which forms an adhesive bond layer. Preferably, the adhesive layer is formed from an adhesive composition containing a polyvinyl alcohol-based resin.

  Any appropriate protective film can be adopted as the protective film provided on the opposite side of the optical film 1 of the polarizer 6 and may be formed of the same material as the thermoplastic resin described above.

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

[Method for producing optical film]
In a preferred method for producing the optical film of the present invention, a water-dispersible urethane resin (A) diluted with an aqueous solvent and having a glass transition temperature (Tg) of less than 60 ° C., and a glass transition temperature (Tg) of 60 ° C. or more and 120 ° C. An easy-adhesive composition containing a water-dispersible urethane resin (B) having a weight increase rate of 20% or less in a warm water resistance test is applied to at least one surface of a thermoplastic resin film. A film is formed (application process), and then the coating film is dried to form an easy-adhesion layer (drying process).

  Any appropriate method can be adopted as a method of applying the easy-adhesion composition in the application step. Examples thereof 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 process can be appropriately adjusted according to the thickness required when the coating film becomes an easy-adhesion layer.

  It is preferable that the surface to which the easily bonding composition in a thermoplastic resin film is apply | coated is surface-treated. The surface treatment is preferably corona discharge treatment or 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.

  A drying process in particular is not restrict | limited, A conventionally well-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 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 ° C. or lower, more preferably 180 ° C. or lower.

  When stretching a thermoplastic resin film, the stretching may be performed before the formation of the easy-adhesion layer or after the formation of the easy-adhesion layer. Moreover, you may perform formation of an easily bonding layer and extending | stretching of a thermoplastic resin film simultaneously.

  When forming an easily bonding layer and extending | stretching a thermoplastic resin film simultaneously, what is necessary is just to extend | stretch the thermoplastic resin film in which the coating film of the easily bonding composition was formed in a heating atmosphere after an application | coating process, for example. Due to the heat applied to the film for stretching, the coating film of the easy-adhesive composition formed on the surface of the thermoplastic resin film is dried to form an easy-adhesive layer. If it does in this way, the extending | stretching process of a film and drying of an easily bonding composition can be implemented simultaneously, and it is preferable from being excellent in productivity.

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

The following were used as raw materials. Table 1 shows the glass transition temperature, elongation at break, and weight increase rate of the hot water resistance test for the characteristic values of the water-dispersible urethane resins (A) and (B).
<Water-dispersible urethane resin (A)>
-Emulsion of water-dispersible urethane resin (A-1) [Daiichi Kogyo Seiyaku Co., Ltd., Superflex (registered trademark) 210, solid content: 35% by weight]
-Emulsion of water-dispersible urethane resin (A-2) [Daiichi Kogyo Seiyaku Co., Ltd., Superflex (registered trademark) 150, solid content: 30% by weight]
-Emulsion of water-dispersible urethane resin (A-3) [Daiichi Kogyo Seiyaku Co., Ltd., Superflex (registered trademark) 420, solid content: 32% by weight]
-Emulsion of water-dispersible urethane resin (A-4) [Daiichi Kogyo Seiyaku Co., Ltd., Superflex (registered trademark) 460, solid content: 38% by weight]
<Water-dispersible urethane resin (B)>
-Emulsion of water-dispersible urethane resin (B-1) [Daiichi Kogyo Seiyaku Co., Ltd., Superflex (registered trademark) 130, solid content 35% by weight]
-Emulsion of water-dispersible urethane resin (B-2) [Daiichi Kogyo Seiyaku Co., Ltd., Superflex (registered trademark) 870, solid content: 30% by weight]
<Fine particles>
-Emulsion containing acrylonitrile-based fine particles (PAN fine particles) [manufactured by Sekisui Chemical Co., Ltd., ADVANCEL NS K-001, average particle size 150 nm, solid content 20% by weight]

Examples 1-4 and Comparative Examples 1-8
1. Manufacture of an easily bonding composition The said raw material emulsion was selected and mixed so that each component shown in Table 2 might contain the solid content amount (unit is a weight part) shown in Table 2, and the easily bonding composition was manufactured. In addition, ion exchange water was used as an aqueous solvent, and the solid content of the easy-adhesion composition was adjusted to 8% by weight.

2. Production of optical film Pellets of methacrylic resin [Tg: 135 ° C., melt viscosity: 700 Pa · s (temperature: 270 ° C., shear rate: 100 (1 / sec))] were uniaxially extruded (φ = 20.0 mm, L / D = 25) and a coat hanger type T die (width: 150 mm), melt extruded at 280 ° C., and the molten resin is discharged onto a cooling roll held at 110 ° C. to obtain a methacrylic resin film having a thickness of 100 μm. Formed. Next, after applying the easy-adhesion composition obtained above on one surface of the methacrylic resin film using a bar coater, it was put into a hot air dryer and dried at 100 ° C. for 90 seconds. Then, the film is uniaxially stretched using a table stretching machine (stretching ratio: 2.5 times), and an optical film having an easy-adhesion layer having a thickness of 0.3 μm is formed on the surface of the methacrylic resin film having a thickness of 40 μm. Manufactured.

3. Manufacture of a polarizing plate The polyvinyl alcohol-type adhesive composition was apply | coated to the easily bonding layer side of the optical film obtained above. Moreover, the polyvinyl alcohol-type adhesive composition was apply | coated to one side of the 40-micrometer-thick triacetylcellulose film (protective film) which performed the saponification process. Next, an optical film and a protective film are laminated on both sides of a polarizer having a thickness of 30 μm via a polyvinyl alcohol adhesive coating layer, and the obtained laminate is put into a hot air dryer (70 ° C.). It was made to dry for a while and the polarizing plate was manufactured. Further, a reference polarizing plate for evaluation in which both sides of the polarizer were provided with a triacetyl cellulose protective film was similarly prepared.

The following evaluation was performed about the polarizing plate obtained above. The evaluation results are shown in Table 2.
(1) Initial adhesion After cutting out a test piece having a size of 25 mm × 250 mm from the polarizing plate obtained above, and applying an adhesive process to the surface of the optical film of the test piece, a sample for measurement was obtained by sticking to a glass plate. It was. After that, a notch is made between the sample polarizer and the optical film, and the polarizer and the protective film are gripped. Was measured. The peel adhesion strength was also measured under the same conditions for the reference polarizing plate. From the measurement results, the peel adhesion strength was evaluated according to the following criteria.
◎: Peeling adhesive strength is superior to the reference polarizing plate ○: Peeling adhesive strength is equivalent to the reference polarizing plate △: Peeling adhesive strength is inferior to the reference polarizing plate ×: Not measured and cannot be measured (2) Moist heat resistance (60 ° C, 90% RH)
The measurement sample obtained in the same manner as described above was put in a constant temperature and humidity chamber at a temperature of 60 ° C. and a humidity of 90% RH, and was subjected to a heat treatment that was allowed to stand for 250 hours and 500 hours. The peel adhesion strength was measured. From the measurement results, the peel adhesion strength was evaluated according to the following criteria.
◎: Peeling adhesive strength is superior to the reference polarizing plate ○: Peeling adhesive strength is equivalent to the reference polarizing plate △: Peeling adhesive strength is inferior to the reference polarizing plate ×: Not measured and cannot be measured (3) Moisture and heat resistance (80 ° C, 90% RH)
The sample for measurement obtained in the same manner as described above was put into a constant temperature and humidity chamber at a temperature of 80 ° C. and a humidity of 90% RH, and was subjected to a heat treatment that was allowed to stand for 100 hours. Strength was measured. From the measurement results, the peel adhesion strength was evaluated according to the following criteria.
◎: Peeling adhesive strength is superior to the reference polarizing plate ○: Peeling adhesive strength is equivalent to the reference polarizing plate △: Peeling adhesive strength is inferior to the reference polarizing plate

As shown in Table 2, a water dispersible urethane resin (A) having a Tg of less than 60 ° C. and a water dispersible urethane resin having a Tg of 60 ° C. or more and 120 ° C. or less and a weight increase rate in a warm water resistance test of 20% or less. The optical films of Examples 1 to 4 using the easy-adhesion layer containing (B) showed excellent results in initial adhesion and excellent adhesion 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 containing only the water-dispersible urethane resin (A) having a Tg of less than 60 ° C. are adhesive in long-time use under high temperature and high humidity. Inferior results. Further, the optical films of Comparative Examples 7 and 8 containing only the water-dispersible urethane resin (B) having a Tg of 60 ° C. or more and 120 ° C. or less and a weight increase rate of 20% or less in the hot water resistance test are high temperature and high humidity treatments. Although the later adhesion was improved, the results showed inferior initial adhesion.

Claims (10)

  A water-dispersible urethane resin (A) having a glass transition temperature of less than 60 ° C. and a water-dispersible urethane resin (B) having a glass transition temperature of 60 ° C. or more and 120 ° C. or less and a weight increase rate in a warm water resistance test of 20% or less. ).   The easily adhesive composition according to claim 1, wherein a 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.   The easily adhesive composition according to claim 1 or 2, wherein the water-dispersible urethane resin (A) has a glass transition temperature of -25 ° C or higher.   The easy-adhesion composition according to any one of claims 1 to 3, wherein the water-dispersible urethane resin (A) has a breaking elongation of 300% or less.   The easily bonding composition according to any one of claims 1 to 4, wherein the water-dispersible urethane resin (B) has a breaking elongation of 100% or less.   Furthermore, the easily bonding composition in any one of Claims 1 thru | or 5 which contains 0.1-15 weight part with respect to a total of 100 weight part of water dispersible urethane resin (A) and (B) fine particle.   An easily adhesive layer according to any one of claims 1 to 6, wherein the easily adhesive layer is an optical film comprising a thermoplastic resin film and an easily adhesive layer provided on at least one surface of the thermoplastic resin film. An optical film formed from a composition.   The optical film according to claim 7, wherein the resin film is made of a (meth) acrylic resin.   9. A polarizing plate comprising the optical film according to claim 7 or 8, an adhesive layer, and a polarizer laminated in this order so that the easy-adhesion layer is in contact with the adhesive layer. A water-dispersible urethane resin (A) diluted with an aqueous solvent and having a glass transition temperature of less than 60 ° C., a glass transition temperature of 60 ° C. or more and 120 ° C. or less, and a weight increase rate in a warm water resistance test of 20% or less. Applying an easy-adhesive composition containing a water-dispersible urethane resin (B) to 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 The manufacturing method of the optical film which consists of a process to do.