KR20140146391A - Aqueous primer composition, optical film and polarizing plate comprising the same - Google Patents

Abstract

The present invention relates to a primer composition comprising a polyurethane resin, water-dispersible fine particles and water, wherein the content of the polyurethane resin is 1 to 30 parts by weight based on 100 parts by weight of the primer composition and the content of the water- Wherein the polyurethane resin is formed by reaction between a polyester polyol and isocyanate, and the polyester polyol is contained in an amount of 30 to 80 wt% based on the total weight of the reactant, , And an optical film and a polarizing plate comprising the primer composition.

Description

[0001] The present invention relates to a water-based primer composition, an optical film comprising the same, and a polarizer,

The present invention relates to an aqueous primer composition, an optical film containing the same and a polarizer, and more specifically, to an aqueous primer composition having excellent adhesiveness and transparency, and an optical film and a polarizer including the same.

The polarizing plate has been used as a structure in which a protective film is laminated on one or both sides of a polarizer made of polyvinyl alcohol (PVA) resin dyed with a dichroic dye or iodine. Conventionally, a triacetyl cellulose (TAC) film has been mainly used as a polarizer protective film. However, such a TAC film has a problem that it is easily deformed in a high temperature and high humidity environment. Recently, protective films of various materials capable of replacing TAC films have been developed. For example, protective films such as polyethylene terephthalate (PET), cycloolefin polymer (COP) Or a mixture thereof.

On the other hand, as the adhesive that can be used for attaching the polarizer and the protective film, an acrylic adhesive, an adhesive for a dry laminate in which a urethane resin solution and a polyisocyanate resin solution are mixed, a styrene butadiene rubber adhesive, an epoxy adhesive, a polyvinyl alcohol adhesive , Urethane-based adhesives, adhesives containing a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group, thermosetting adhesives, and the like are known. Among these adhesives, water-based adhesives comprising an aqueous solution of a polyvinyl alcohol- Sieve is mainly used.

However, when an acryl-based film or a COP film other than TAC is used as a protective film, the water-based adhesive has a problem that its use is limited depending on the film material because the adhesive strength is weak. In order to improve the adhesive strength of the film surface, there is known a method such as plasma treatment or corona treatment of the film surface. However, in the case of an acrylic film or a COP film, sufficient adhesion can not be secured by the above treatment alone.

Therefore, a method of using a non-aqueous UV curable adhesive excellent in adhesion to an acrylic film or a COP film has been proposed. However, when such a UV-curable adhesive is used, a separate UV curing process is required, and an explosion-proof facility due to the use of volatile and flammable monomers is additionally required. In general, since the non-aqueous adhesive has a higher viscosity than an aqueous adhesive, it is difficult to control the thickness of the adhesive layer to 1 mm or less. If the thickness of the adhesive layer increases, the brittleness of the polarizer increases, There is a problem in that a problem such as occurrence of wrinkles or the like is likely to occur. In addition, the non-aqueous adhesive has an excellent adhesive strength with the acrylic film and / or the COP film, but has a problem of poor adhesion to the PVA polarizer. Therefore, a technique of including an acidic reactor in order to improve the adhesion with a polarizer has been proposed, but this is likely to cause corrosion and deformation by acid, which is not desirable in terms of work environment.

Therefore, it is required to develop a technique capable of increasing the adhesive force to an acrylic film or a COP film while using an existing water-based adhesive.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above problems, and it is an object of the present invention to provide a primer composition having excellent adhesion to an aqueous adhesive and an acrylic film, and an optical film and a polarizing plate containing the primer composition.

In one aspect, the present invention is a primer composition comprising a polyurethane resin, water-dispersible fine particles and water, wherein the content of the polyurethane resin is 1 to 30 parts by weight based on 100 parts by weight of the primer composition, The content is 0.1 to 20 parts by weight based on 100 parts by weight of the solid content of the polyurethane resin. The polyurethane resin is formed by reaction of a polyester-based polyol and isocyanate, and the polyester- To 80% by weight, based on the total weight of the primer composition.

In another aspect, the present invention provides a film comprising a substrate film; And a primer layer formed on the at least one surface of the base film by the primer composition.

In another aspect, the present invention provides a polarizing plate comprising a polarizer, an adhesive layer formed on at least one side of the polarizer, and an optical film adhered on the adhesive layer, wherein the optical film comprises a base film, And a primer layer formed by the primer composition of the present invention described above.

In another aspect, the present invention provides an image display device including the polarizing plate.

The primer composition of the present invention can be applied as it is without any additional process or equipment to the existing polarizer laminating process without adversely affecting the transparency of the optical film and excellent in adhesiveness. Particularly, when an acrylic film is used as a polarizer protective film, And does not adversely affect the optical properties and durability of the polarizing plate.

Hereinafter, the present invention will be described in more detail.

The inventors of the present invention have conducted research to develop a technique capable of increasing the adhesion to an acrylic film or a COP film while using an existing water based adhesive. As a result, they have found that a polyurethane resin containing a specific amount of a polyester- Of the present invention in a specific amount.

More specifically, the primer composition of the present invention is a primer composition comprising a polyurethane resin, water-dispersible fine particles and water, wherein the content of the polyurethane resin is 1 to 30 parts by weight per 100 parts by weight of the primer composition, The content of the water-dispersible fine particles is 0.1 to 20 parts by weight based on 100 parts by weight of the solid content of the polyurethane resin. The polyurethane resin is formed by reaction of a polyester-based polyol and isocyanate, And is contained in an amount of 30 to 80% by weight based on the weight.

As used herein, the term " remainder " means the remaining parts by weight excluding the contents of the polyurethane resin, the fine particles and optionally the components when the total primer composition is 100 parts by weight. That is, after the addition of the polyurethane resin, the fine particles and the optionally contained components, water is added to adjust the content of the entire primer composition to 100.

In the present invention, the polyurethane resin is used for ensuring adhesion to an acrylic film and an aqueous adhesive. The polyurethane resin is used in an amount of 1 to 30 parts by weight, preferably 3 to 20 parts by weight, More preferably 5 to 15 parts by weight. When the content of the polyurethane resin is less than 1 part by weight, it is difficult to obtain a sufficient adhesive strength. When the amount of the polyurethane resin is more than 30 parts by weight, viscosity is increased and leveling is not smooth during coating.

In the present invention, it is preferable that the polyurethane resin is formed by the reaction of a polyester polyol and isocyanate. Polyester-based urethanes are advantageous in that they can achieve various chemical structures and adhesive strength since various polyols necessary for synthesis can be obtained in various combinations. In addition, the polyester system has advantages over the polyether system and the carbonate system, and has advantages of excellent solvent resistance, chemical resistance, and water resistance.

On the other hand, the content of the polyester polyol in forming the polyurethane is preferably about 30 to 80% by weight of the total reactants. In this case, the content of the total reactant means the total amount of the components used at the time of producing the polyurethane, that is, the contents of arbitrarily included components such as polyol component, isocyanate component and chain extender, not included. As a result of research conducted by the present inventors, it has been found that the content of the polyester polyol in the polyurethane resin must satisfy the above-mentioned range in order to obtain the adhesive property with the water-based adhesive at an effective level.

On the other hand, the polyester polyol is typically obtained by reacting a polybasic acid component with a polyol component. Examples of the polybasic acid component include ortho-phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalene dicarboxylic acid, 2,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid , Aromatic dicarboxylic acids such as biphenyldicarboxylic acid and tetrahydrophthalic acid; Aliphatic dicarboxylic acids such as oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, linoleic acid, maleic acid, fumaric acid, mesaconic acid and itaconic acid; Alicyclic dicarboxylic acids such as hexahydrophthalic acid, tetrahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; Or reactive derivatives thereof such as acid anhydrides, alkyl esters, acid halides and the like. These may be used alone or in combination of two or more.

On the other hand, the polyol is not particularly limited as long as it has two or more hydroxyl groups in the molecule, and any suitable polyol may be employed. Examples of the polyol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, Hexanediol, 1,8-octanediol, 1,10-decanediol, 4,4'-dihydroxyphenylpropane, 4,4'-dihydroxymethylmethane, diethylene glycol, triethylene glycol, polyethylene glycol PEG), dipropylene glycol, polytetramethylene glycol (PTMG), polypropylene glycol (PPG), 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, bisphenol A, bisphenol F, glycerin, , 1-trimethylol propane, 1,2,5-hexatriol, pentaerythritol, glucose, sucrose, and sorbitol. Among these, at least one selected from the group consisting of polytetramethylene glycol (PTMG), polypropylene glycol (PPG) and polyethylene glycol (PEG) is particularly preferable.

It is particularly preferable that the polyester polyol is a polyester diol.

On the other hand, the isocyanate is not limited as long as it is a compound having two or more NCO groups, and examples thereof include toluene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI), 1,5- (TODI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), p-phenylene diisocyanate, transcyclohexane, 1,4-diisocyanate and xylene diisocyanate May be used singly or in combination of two or more.

In the present invention, it is preferable that the polyurethane resin contains a carboxyl group or a tertiary amine group. When a carboxyl group or a tertiary amine group is contained in the polyurethane resin, the dispersibility to water is improved and the adhesion to the polarizer is improved. On the other hand, the polyurethane resin containing a carboxyl group or a tertiary amine group can be prepared by reacting a polyester polyol with an isocyanate by adding a chain extender having a free carboxyl group or a free amine group in the reaction. Examples of the chain extender having the free carboxyl group include dihydroxycarboxylic acid and dihydroxysuccinic acid. Examples of dihydroxycarboxylic acids include dialkylolalkanoic acids including dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutyric acid, and dimethylolalkanoic acid such as dimethylolpentanoic acid. These may be used alone or in combination of two or more. On the other hand, examples of the chain extender having a free amine group include aliphatic diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, 1,4-butanediamine and aminoethylenecanolamine; Alicyclic diamines such as isophoronediamine and 4,4'-dicyclohexylmethanediamine; And aromatic diamines such as xylylenediamine and tolylene diamine.

In the present invention, the weight average molecular weight of the polyurethane polymer is preferably 10,000 to 100,000. When the molecular weight is less than 10,000, it is difficult to achieve a sufficient adhesive strength, and when it exceeds 10,000, the water dispersibility may be deteriorated.

The method for producing the polyurethane resin may employ any appropriate method known in the art. Specifically, a single shot method in which each component is reacted at a time, and a multi-step method in which the components are reacted stepwise. When the polyurethane resin has a carboxyl group or a tertiary amine group, it is more preferable that the polyurethane resin is produced by a multi-stage method. Because the carboxyl group can be easily introduced by the multistage method. Further, any appropriate urethane reaction catalyst may be used in the production of the polyurethane resin.

On the other hand, the polyurethane resin may further include other polyol or chain extender in addition to the above components, so long as the properties of the present invention are not impaired.

Examples of other polyols include polyols having three or more hydroxyl groups such as sorbitol, glycerin, trimethylol ethane, trimethylol propane, pentaerythritol, etc., polyether polyols and polycarbonate diols. At this time, the polyether polyol is typically obtained by ring-opening polymerization of an alkylene oxide to a polyhydric alcohol. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, and trimethylolpropane. These may be used alone or in combination of two or more. The polycarbonate polyol may be at least one or more selected from the group consisting of, for example, poly (hexamethylene carbonate) glycol and poly (cyclohexanecarbonate) glycol.

Examples of other chain extenders include but are not limited to acetylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, Glycols such as hexanediol, propylene glycol and the like.

Further, the polyurethane resin may further include a neutralizing agent, if necessary. The stability of the urethane resin in water can be improved when a neutralizing agent is included. Examples of the neutralizing agent include ammonia N-methylmorpholine, triethylamine, dimethylethanolamine, methyldiethanolamine, triethanolamine, morpholine, tripropylamine, ethanolamine, triisopropanolamine and the like. These may be used alone or in combination of two or more.

In addition, the production of the polyurethane resin is preferably carried out in an organic solvent which is inert to the polyisocyanate and has compatibility with water. Examples of the organic solvent include ester solvents such as ethyl acetate and ethyl cellosolve acetate; Ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; And ether solvents such as dioxane tetrahydrofuran. These may be used alone or in combination of two or more.

Next, the primer composition of the present invention comprises 0.1 to 10 parts by weight of water-dispersible fine particles per 100 parts by weight of the polyurethane resin solid content. When the content of the water-dispersible fine particles is less than 0.1 part by weight, there is a problem in that the film is not slipped between the films during winding and breakage may occur. When the content is more than 10 parts by weight, haze value increases and transparency of the film is deteriorated It is because.

The water dispersible microparticles that can be used in the present invention may be any suitable microparticles, for example, inorganic fine particles. Organic fine particles, or a combination thereof. Examples of the inorganic fine particles include inorganic oxides such as silica, titania, alumina, zirconia and antimony. Examples of the organic fine particles include a silicone resin, a fluorine resin, a (meth) acrylic resin, a crosslinked polyvinyl alcohol, and a melamine resin.

Among the water-dispersible fine particles, silica is particularly preferable. Silica is more excellent in blocking inhibition ability and is excellent in transparency, does not cause haze and has no coloration, and therefore has a smaller influence on the optical characteristics of the polarizing plate. In addition, since the colloidal silica has good dispersibility and dispersion stability with respect to the primer composition, it is superior in workability at the time of forming the primer layer

On the other hand, the water-dispersible fine particles preferably have an average diameter (average primary particle diameter) of about 10 to 200 nm, more preferably about 20 to 70 nm. When the average diameter of the water-dispersible microparticles is less than 10 nm, surface energy is increased, so that the stability of the solution may be deteriorated due to the aggregation and precipitation of the water-dispersible particles in the primer solution. When the average diameter is larger than 200 nm, The dispersion does not occur uniformly in the primer solution, and as the particles aggregate, the particle size becomes larger than the wavelength of visible light (400 nm-800 nm), so that light of 400 nm or more is scattered and the haze increases. By using the fine particles having the particle diameters in the above-mentioned range, it is possible to appropriately form irregularities on the surface of the primer layer, effectively reducing the frictional force particularly on the contact surface between the acrylic film and the primer layer and / or the primer layer. As a result, blocking ability can be further improved.

Since the primer composition of the present invention is aqueous, the fine particles are preferably formulated as an aqueous dispersion. Specifically, when silica is employed as the fine particles, it is preferably blended as colloidal silica. As the colloidal silica, products commercially available in the technical field can be used as it is. Examples of the colloidal silica include SNOWTEX series manufactured by Nissan Chemical Industries, AEROSIL series manufactured by Air Products, epostar series and soliostar RA series manufactured by Japan Catalyst, Ranco LSH series can be used.

On the other hand, the primer composition of the present invention may further comprise a crosslinking agent, if necessary. When the cross-linking agent is further included, an effect of improving the water resistance and the adhesive force holding ability under a high-temperature environment can be obtained. The crosslinking agent is preferably contained in an amount of 1 to 100 parts by weight, more preferably 1 to 50 parts by weight, and most preferably 1 to 30 parts by weight based on 100 parts by weight of the solid content of the polyurethane resin. When the content of the crosslinking agent satisfies the above-described numerical value range, the adhesive strength and water resistance are excellent. On the other hand, the crosslinking agent used in the present invention preferably contains an oxazoline group, an epoxy silane group, a block isocyanate group, a carbodiimide group, or a combination thereof. The crosslinking agent containing the functional groups is excellent in water dispersibility and storage stability at room temperature.

Next, the optical film of the present invention will be described.

The optical film of the present invention comprises a base film; And a primer layer formed from the primer composition of the present invention on at least one surface of the base film. Since the primer composition is the same as that described above, a detailed description thereof will be omitted.

On the other hand, the primer layer formed by the primer composition of the present invention has a water contact angle of about 40 to 100 degrees, more preferably 50 to 90 degrees, and more preferably 60 to 80 degrees at its surface. When the water contact angle is less than 40 degrees, the hydrophilic property of the primer layer is strong. Therefore, the primer layer reacts with the iodine of the polarizer to inhibit the iodine arrangement so that the single color may be disturbed and the polarization degree may be inhibited. When the water contact angle exceeds 100 degrees, The hydrophobicity of the polarizer is strong and the adhesion to the polarizer is difficult.

On the other hand, the base film may be a single layer or a structure in which two or more films are laminated, or in the case of a structure in which two or more films are laminated, the laminated films may be made of the same or different materials.

More preferably, the base film is preferably an acrylic film. Herein, the acrylic film refers to a film containing a resin containing an acrylate-based unit and / or a methacrylate-based unit as a main component, and includes not only a homopolymer resin composed of an acrylate-based unit or a methacrylate- A film mainly composed of a copolymer resin copolymerized with other monomer units in addition to a system unit and / or a methacrylate unit, and a film formed by a blend resin blended with another resin in the above acrylic resin.

The monomer unit copolymerizable with the acrylic resin may include a styrene unit, a vinyl unit, a 3- to 6-membered heterocyclic unit substituted with a carbonyl group, an acrylic acid unit, a glycidyl unit, and the like.

For example, the acrylic film may be a film comprising a copolymer comprising an alkyl (meth) acrylate-based unit and a 3- to 10-membered heterocyclic unit substituted with at least one carbonyl group. The 3 to 6 membered heterocyclic unit substituted with the carbonyl group may be a lactone ring, a glutaric anhydride, a glutarimide, a maleic anhydride, a maleimide And so on.

Another example of the acrylic film is a film comprising a blending resin blended with an aromatic resin having a carbonate moiety in the main chain of the acrylic resin. At this time, the aromatic resin having a carbonate moiety in the main chain may be, for example, a polycarbonate resin or a phenoxy resin.

The method for producing the acrylic resin film is not particularly limited. For example, an acrylic resin, other polymers, additives, and the like may be thoroughly mixed by any appropriate mixing method to prepare a thermoplastic resin composition, Or an acrylic resin, other polymers, additives, etc. may be prepared as separate solutions and then mixed to form a homogeneous mixture solution, which may then be film-formed.

The thermoplastic resin composition is prepared by pre-blending the film raw material with any suitable mixer such as an omni mixer, and then extruding and kneading the resulting mixture. In this case, the mixer 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 press kneader can be used.

As the film forming method, any suitable film forming method such as a solution casting method (solution casting method), a melt extrusion method, a calendering method, a compression molding method and the like can be used. Among these film forming methods, a solution casting method (solution casting method) and a melt extrusion method are preferable.

Examples of the solvent used in the solution casting method (solution casting method) include aromatic hydrocarbons such as benzene, toluene and xylene; Aliphatic hydrocarbons such as cyclohexane and decalin; Esters such as ethyl acetate and butyl acetate; Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Alcohols such as methanol, ethanol, isopropanol, butanol, isobutanol, methyl cellosolve, ethyl cellosolve and butyl cellosolve; Ethers such as tetrahydrofuran and dioxane; Halogenated hydrocarbons such as dichloromethane, chloroform and carbon tetrachloride; Dimethylformamide; Dimethyl sulfoxide and the like. These solvents may be used alone or in combination of two or more.

Examples of the apparatus for carrying out the solution casting method (solution casting method) include a drum casting machine, a band casting machine and a spin coater. 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 a 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, and a rolled film is obtained by winding a film extruded in a film form. At this time, uniaxial stretching can also be performed by stretching in the extrusion direction by appropriately adjusting the temperature of the winding roll. Further, simultaneous biaxial stretching, sequential biaxial stretching, and the like can also be carried out by stretching the film in a direction perpendicular to the extrusion direction.

The acrylic film may be either an unoriented film or a stretched film. In the case of a stretched film, it may be a uniaxially stretched film or a biaxially stretched film, and in the case of a biaxially stretched film, it may be a simultaneous biaxially stretched film or a sequential biaxially stretched film. When biaxially stretched, the mechanical strength is improved and the film performance is improved. By mixing other thermoplastic resins, the acrylic film can suppress an increase in retardation even when stretching, and can maintain optical isotropy.

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 (glass transition temperature-30 占 폚) to (glass transition temperature + 100 占 폚) Temperature -20 占 폚) to (glass transition temperature + 80 占 폚). If the stretching temperature is lower than (glass transition temperature -30 占 폚), there is a possibility that a sufficient stretching ratio may not be obtained. On the other hand, if the stretching temperature exceeds (glass transition temperature + 100 deg. C), the resin composition may flow (flow), and stable drawing may not be performed.

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 accompanying the draw may not be improved. If the stretching magnification exceeds 25 times, there is a possibility that the effect of increasing the stretching magnification may not be recognized.

The stretching speed is preferably 10 to 20,000% / min, more preferably 100 to 10.000% / min in one direction. When the drawing speed is less than 10% / min, it takes a long time to obtain a sufficient drawing magnification, which may increase the manufacturing cost. If the stretching speed is more than 20,000 < RTI ID = 0.0 >< / RTI ><

The acrylic film may be subjected to a heat treatment (annealing) after the stretching treatment so as to stabilize its optical isotropy or mechanical properties. The heat treatment conditions are not particularly limited and any suitable conditions known in the art can be employed.

Meanwhile, the optical film of the present invention can be produced by coating the primer composition of the present invention on at least one side of the above base film to form a primer layer. At this time, the coating is performed by applying a primer composition onto a substrate film by using a method well known in the art, for example, a bar coating method, a gravure coating method, a slot die coating method, . The drying may be carried out through a convection oven or the like, but is not limited thereto. The drying is preferably performed at a temperature of 100 ° C to 120 ° C for 1 minute to 5 minutes. The drying temperature may vary depending on the coating step and may be carried out in a range not exceeding the glass transition temperature (Tg) of the film in the case of the film being drawn. If the film is stretched, drying is effected at the stretching temperature, Is not in excess of the decomposition temperature (Td).

Meanwhile, the thickness of the primer layer formed by the above-described method is preferably 50 nm to 1000 nm, more preferably 100 nm to 800 nm, and still more preferably 200 nm to 500 nm. When the thickness of the primer layer is less than 50 nm, there is a problem that the adhesive strength is not sufficient. When the thickness exceeds 1000 nm, there is a problem that drying is not sufficient or the water dispersible fine particles are embedded in the primer layer.

Further, if necessary, a surface treatment for improving the adhesive strength may be performed on at least one side of the substrate film, and the surface treatment method may be at least one selected from the group consisting of alkali treatment, corona treatment, and plasma treatment have. In particular, when the base film used in the present invention is an acrylic film not containing a lactone ring, the surface treatment is preferably performed.

Next, the polarizing plate of the present invention will be described.

The polarizing plate of the present invention is a polarizing plate comprising a polarizer, an adhesive layer formed on at least one side of the polarizer, and an optical film adhered on the adhesive layer, wherein the optical film of the present invention, And an optical film comprising a primer layer formed by the above-described primer composition of the present invention on at least one surface of the base film.

At this time, the adhesive layer is preferably a polyvinyl alcohol (PVA) adhesive, and among these, a modified PVA adhesive containing an acetoacetyl group or the like is preferable. An adhesive force superior to that in the case of using the modified PVA adhesive can be realized. Specific examples of the polyvinyl alcohol adhesive include, but are not limited to, Z-100, Z-200, Z-200H, Z-210, Z-220 and Z-320 manufactured by Japan Synthetic Chemicals Gohsefimer .

The base film of the optical film is preferably an acrylic film. When an acrylic film is used, excellent heat resistance and durability can be obtained. Further, when the primer layer formed by the primer composition of the present invention is formed on one side of the base film as in the present invention, there is no problem of deterioration of adhesive strength that occurs when a conventional acrylic film is used as a protective film. The primer layer of the present invention is present between a very small number of acrylic films having a water contact angle of 90 degrees and an extreme hydrophilic polarizer or water based adhesive having a water contact angle of 50 degrees or less and having polarities different from each other between polarizers This is because a buffering action is given to give an adhesive force.

Meanwhile, the polarizing plate according to the present invention preferably has a light transmittance of 35% to 45% and a polarization degree of 98% or more.

As described above, the polarizing plate according to the present invention is advantageous in that it has excellent optical properties such as transmittance, polarization degree and color, and is excellent in adhesion between the adhesive layer and the protective film, between the adhesive layer and the polarizer, and excellent in durability. In addition, since the conventional polyvinyl alcohol adhesive is used as an adhesive, there is an advantage that it can be applied to a mass production line without any change in process conditions.

Furthermore, the optical film or polarizing plate of the present invention can be applied to various image display devices such as liquid crystal display devices.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are for illustrative purposes only, and the scope of the present invention is not limited by the following examples.

Synthetic example  1 - polyurethane A synthesis

66 g of methyl ethyl ketone was added to 40 g of polyester diol (SKC, molecular weight: 2000), and the mixture was sufficiently stirred to dissolve. After adding 8 g of ethylene glycol and 40 g of isophorone diisocyanate, For 1 hour. After completion of the reaction, the reaction mixture was cooled to 60 deg. C, 12 g of dimethyrolpropionic acid and 9 g of triethylamine were added and reacted at 75 DEG C to obtain a prepolymer solution. after that. This prepolymer solution was cooled to 40 캜, and 150 g of water was added thereto, followed by stirring at a high speed using a homomixer to emulsify. This emulsion was heated and reduced to remove methyl ethyl ketone to obtain an aqueous polyurethane resin solution (CK-PUD-PF) having a solid content of 35%.

Synthetic example  2-polyurethane B synthesis

To 63 g of polyester diol (SKC, molecular weight: 2000), 66 g of methyl ethyl ketone was added and sufficiently stirred to dissolve. To this was added 25 g of isophorone diisocyanate, followed by reaction at 75 ° C for 1 hour . After completion of the reaction, the reaction mixture was cooled to 60 deg. C, 12 g of dimethyrolpropionic acid and 9 g of triethylamine were added and reacted at 75 DEG C to obtain a prepolymer solution. after that. This prepolymer solution was cooled to 40 캜, and 150 g of water was added thereto, followed by stirring at a high speed using a homomixer to emulsify. This emulsion was heated and reduced to remove methyl ethyl ketone to obtain an aqueous polyurethane resin solution (CK-PUD-PF) having a solid content of 35%.

Synthetic example  3-polyurethane C synthesis

After adding 66 g of methyl ethyl ketone to 50 g of polyester diol (SKC, molecular weight 2000) and sufficiently stirring and dissolving, 5 g of ethylene glycol and 35 g of isophorone diisocyanate were added thereto, Lt; 0 > C for 1 hour. After completion of the reaction, the mixture was cooled to 60 deg. C, 10 g of dimethyrolpropionic acid and 7.5 g of triethylamine were added, and the mixture was reacted at 75 DEG C to obtain a prepolymer solution. after that. This prepolymer solution was cooled to 40 캜, and 150 g of water was added thereto, followed by stirring at a high speed using a homomixer to emulsify. This emulsion was heated and reduced to remove methyl ethyl ketone to obtain an aqueous polyurethane resin solution (CK-PUD-PF) having a solid content of 35%.

Synthetic example  Synthesis of 4-polyurethane D

After adding 30 g of polyester diol (SKC, molecular weight: 2000) and adding 5.7 g of ethylene glycol and 66 g of methyl ethyl ketone, the mixture was thoroughly stirred to dissolve, 44.3 g of isophorone diisocyanate was added thereto, For 1 hour. After completion of the reaction, the mixture was cooled to 60 deg. C, 20 g of dimethyrolpropionic acid and 15.1 g of triethylamine were added, and the mixture was reacted at 75 DEG C to obtain a prepolymer solution. after that. This prepolymer solution was cooled to 40 캜, and 150 g of water was added thereto, followed by stirring at a high speed using a homomixer to emulsify. This emulsion was heated and reduced to remove methyl ethyl ketone to obtain an aqueous polyurethane resin solution (CK-PUD-PF) having a solid content of 30%.

Synthetic example  Synthesis of 5-polyurethane E

To 83 g of polyester diol (SKC, molecular weight 2000), 66 g of methyl ethyl ketone was added and dissolved sufficiently to dissolve. 14 g of isophorone diisocyanate was added thereto, and the mixture was reacted at 75 DEG C for 1 hour . After completion of the reaction, the mixture was cooled to 60 deg. C, 3 g of dimethyrolpropionic acid and 2.3 g of triethylamine were added, and the mixture was reacted at 75 DEG C to obtain a prepolymer solution. after that. This prepolymer solution was cooled to 40 캜, and 150 g of water was added thereto, followed by stirring at a high speed using a homomixer to emulsify. This emulsion was heated and reduced to remove methyl ethyl ketone to obtain an aqueous polyurethane resin solution (CK-PUD-PF) having a solid content of 35%.

Example  One

20 g of the polyurethane A prepared in Synthesis Example 1, 7 g of colloidal silica (20% aqueous solution of solid content) and 73 g of pure water were mixed to prepare a primer composition of 8.4% by weight. Then, the primer composition was coated on one surface of the corona-treated acrylic film to a thickness of about 200 nm, followed by drying at 100 ° C for 5 minutes, to prepare an acrylic film having a primer layer. At this time, AX-film of Japanese catalyst having a thickness of 50 탆 was used as the acrylic film, and the surface of the film was subjected to corona treatment under the condition of 50 W / m ² / min.

Then, a polyvinyl alcohol-based adhesive was applied to both sides of the polarizer, and an acrylic film and an alkali-treated TAC film were placed on one side and the other side, respectively. Then, the film was compressed using a pressing roll, followed by hot air drying To prepare a polarizing plate.

Example  2

A polarizing plate was prepared in the same manner as in Example 1, except that the polyurethane B prepared in Synthesis Example 2 was used instead of the polyurethane A prepared in Synthesis Example 1.

Example  3

A polarizing plate was prepared in the same manner as in Example 1, except that the polyurethane C prepared in Synthesis Example 3 was used in place of the polyurethane A prepared in Synthesis Example 1.

Example  4

1.3 g of a crosslinking agent (Nippon Catalyst WS700, 25%), 7 g of colloidal silica (20% aqueous solution of solid content) and 69.4 g of pure water were mixed to prepare a 7% by weight primer composition . Then, the primer composition was coated on one surface of the corona-treated acrylic film to a thickness of about 200 nm, followed by drying at 100 ° C for 5 minutes, to prepare an acrylic film having a primer layer. At this time, AX-film of Japanese catalyst having a thickness of 50 탆 was used as the acrylic film, and the surface of the film was subjected to corona treatment under the condition of 50 W / m ² / min.

Then, a polyvinyl alcohol-based adhesive was applied to both sides of the polarizer, and an acrylic film and an alkali-treated TAC film were placed on one side and the other side, respectively. Then, the film was compressed using a pressing roll, followed by hot air drying To prepare a polarizing plate.

Comparative Example  One

A polarizing plate was produced in the same manner as in Example 1, except that the polyurethane D prepared in Synthesis Example 4 was used instead of the polyurethane A prepared in Synthesis Example 1.

Comparative Example  2

A polarizing plate was prepared in the same manner as in Example 1, except that the polyurethane E prepared in Synthesis Example 5 was used instead of the polyurethane A prepared in Synthesis Example 1.

Experimental Example  1 - Water adhesion evaluation

PVA / protective film structure using the protective film prepared in Examples 1 to 4 and Comparative Examples 1 and 2, and dried for 5 minutes in an oven at 80 ° C using a 3% PVA water-based adhesive. The 90 degree peel force was measured using an XT.Plus (Stable Micro Systems) texture analyzer. A width of 2 cm and a length of 8 cm were prepared and the acrylic film surface was fixed to the lower surface of the measuring device and peel force of 90 degrees peel was measured. The measuring distance was 5 cm, and the results are shown in Table 1 below.

With respect to the adhesive strength, when the laminate is joined to the polarizing plate, the peeling force should be 3.0 N / 2 cm or more so that the rework work can be performed stably on the panel.

Experimental Example  2 - Re-workability  evaluation

The polarizing plates produced in Examples 1 to 4 and Comparative Examples 1 and 2 were cut into sample pieces each having dimensions of 5 cm x 5 cm to form an adhesive layer on the acrylic film surface and adhered to the plate glass. Then, even if one edge of the polarizing plate was grasped, the polarizing plate was peeled at a rate of 1 mm / sec in the diagonal direction so as to be 90 degrees with respect to the plate glass, and then the peeling position was observed. The results are shown in Table 1, and the case where the interface between the pressure-sensitive adhesive and the plate glass was peeled off was indicated by o, and the case where the interface between the polarizer and the acrylic film was peeled off was indicated by x.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Aqueous adhesion 4N 4.5N 3.0N 3.5N 1.9N 2.0N Re-workability ○ ○ ○ O × ×

Claims (15)

A primer composition comprising a polyurethane resin, water-dispersible fine particles and water,
The content of the polyurethane resin is 1 to 30 parts by weight based on 100 parts by weight of the primer composition,
The content of the water-dispersible fine particles is 0.1 to 20 parts by weight based on 100 parts by weight of the solid content of the polyurethane resin,
Wherein the polyurethane resin is formed by reaction of a polyester polyol and isocyanate, and the polyester polyol is contained in an amount of 30 to 80% by weight based on the total weight of the reactant.
The method according to claim 1,
Wherein the polyurethane resin comprises a carboxyl group or a tertiary amino group.
The method according to claim 1,
In the polyurethane resin, the ester-based polyol is a polyester diol-based primer composition
The method according to claim 1,
The isocyanate may be selected from the group consisting of toluene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), hexamethylene diisocyanate Is selected from the group consisting of isophorone diisocyanate (IPDI), p-phenylene diisocyanate, transcyclohexane, 1,4-diisocyanate and xylene diisocyanate (XDI), tetramethyl 1,3 xylene diisocyanate (TMXDI) Lt; / RTI >
The method according to claim 1,
The water dispersible fine particles have an average diameter of 10 to 300 nm.
The method according to claim 1,
The water-dispersible fine particles may be at least one kind of inorganic fine particles selected from the group consisting of silica, titania, alumina, zirconia and antimony fine particles or a group consisting of a silicone resin, a fluororesin, a (meth) acrylic resin, a crosslinked polyvinyl alcohol and a melamine resin Based on the total weight of the primer composition.
The method according to claim 1,
1 to 100 parts by weight of a crosslinking agent based on 100 parts by weight of a solid polyurethane resin.
A base film; And
An optical film comprising a primer layer formed by the primer composition according to any one of claims 1 to 7 on at least one surface of the base film.
9. The method of claim 8,
Wherein the base film is an acrylic film.
10. The method of claim 9,
Wherein the acrylic film comprises a copolymer comprising an alkyl (meth) acrylate-based unit and a 3- to 6-membered heterocyclic unit substituted with at least one carbonyl group.
11. The method of claim 10,
Wherein the acrylic film further comprises an aromatic resin having a carbonate moiety in its main chain.
9. The method of claim 8,
Wherein the base film is corona-treated or plasma-treated at least on one side.
A polarizing plate comprising a polarizer, an adhesive layer formed on at least one side of the polarizer, and an optical film adhered on the adhesive layer,
Wherein the optical film comprises a base film and a primer layer formed on at least one side of the base film with the primer composition according to any one of claims 1 to 7.
14. The method of claim 13,
Wherein the adhesive layer is formed of a polyvinyl alcohol-based water-based adhesive,
Wherein the base film is an acrylic film.
An image display device comprising the polarizer of claim 13.