KR102133645B1 - Biaxially-oriented polyester film for optical use - Google Patents

Abstract

The present invention relates to a biaxially oriented polyester film for optics, and more specifically, to an optical function coating process having a uniform adhesion after processing of a functional optical coating such as a substrate and a prism, adhesion, or hard coating, and a heating process. The present invention relates to a biaxially oriented polyester film for optics that prevents oligomer precipitation by heat treatment to be useful, maintains transparency, and has excellent ease of adhesion, thereby achieving product quality and reducing defect rates.

Description

Optical biaxially oriented polyester film {BIAXIALLY-ORIENTED POLYESTER FILM FOR OPTICAL USE}

The present invention relates to a biaxially oriented polyester film for optics, and more specifically, to a laminated optical polyester film applied to films mounted inside a touch panel, LCD, PDP, etc., a primer to improve processability As a structure having a layer, it is possible to suppress the oligomer precipitated from the polyester film in a processing process involving uniform ease of adhesion and heat treatment after post-processing such as a substrate and a prism, adhesion, or hard coating, and transparent biaxial orientation for optical It relates to a polyester film.

In general, the polyester film is excellent in dimensional stability, thickness uniformity, and optical transparency, so that the display device has a wide range of applications as well as various industrial materials. Among them, the polyester film for optics is a plastic film used for optics. More specifically, a plastic film is frequently used as a component of a display device. Among them, a polyester film is used when optical transparency is required. , When durability and heat resistance are required, polyimide films are mainly used. In particular, the biaxially stretched polyester film has excellent dimensional stability, thickness uniformity, and optical transparency, and has been used in various industrial fields as a base film.

In addition, the polyester film for optics is used as a base film by various resins through post-processing treatment, and is used for various purposes. As the resin used for post-processing, UV curable resin is usually used. Therefore, a method of forming a primer coating layer on the surface of the polyester film is generally the most widely used method for uniform adhesion between the UV-curable resin coating layer applied through post-processing and the optical polyester film.

However, although adhesion with various UV resins can be obtained, if heat treatment is applied in the processing process, precipitation of oligomers from the thermoplastic resin film occurs, and practical application as a final product is not possible due to whitening or contamination of the film surface. For this reason, studies have conventionally been made to laminate a coating film on the resin film surface for the purpose of suppressing oligomer precipitation. For example, a coating film having a resin or styrene and acrylic acid structure having an acryloyl group (Patent Documents 1 and 2), a method of designing a coating film using acrylic modified polyester (Patent Documents 3 and 4), and having specific functional groups A method for designing additives such as resins, mineral oils, and crosslinking agents in a resin layer (Patent Document 5) has been proposed.

Even if a resin having an acryloyl group or a resin layer having a styrene and acrylic acid structure is designed as in Patent Documents 1 and 2 among these prior arts, the adhesion between the polyester-based base film and the resin is sufficient, but the heat resistance, It has poor adhesion to moisture, and when it is post-processed with a prism processing layer, a lens processing layer, an anti-reflection layer or a hard coating layer, which is another base material, there is a problem that adhesion is very insufficient, and also acrylic modified polyester on the film surface as in Patent Documents 3 and 4 The method of designing the resin layer by using contains an acrylic component having a glass transition point of a certain temperature or higher in the acrylic modified polyester, but when curing the resin layer, defects or cracks occur in the resin layer and sufficient oligomer suppression effect is not exhibited. Not only that, there is a problem of reducing the transparency and easy adhesion of the laminated film, and the method of using additives as in Patent Document 5 also causes the additive itself to bleed out on the surface layer of the resin layer at the time of forming the resin layer or over time after film formation. There is a problem in that the adhesion is deteriorated and the whitening of the resin film or contamination of the film surface is generated in the same way as the oligomer precipitation.

Therefore, the optical polyester film used as a base film requires post-processing work characteristics, in particular, uniform adhesion with water used for post-processing, and the technology to maintain transparency as an optical base by suppressing oligomer precipitation reduces the defect rate of the product. And it can be said to be essential to achieve improved life and high quality, and thus, the present inventors have solved the above-mentioned drawbacks, and have developed an optically biaxially oriented polyester film for excellent adhesion and oligomer suppression at the same time.

Japanese patent JP 6040934 Japanese patent JP 6023227 Japanese Patent Laid-Open Publication No. 4-263937 Japanese Patent Publication No. 2003-012841 Japanese Patent Publication No. 2006-281498

The present invention has been devised to solve the above problems and to meet the conventional requirements, the object of the present invention is to improve the adhesive strength with the optical polyester film having a primer layer and post-processing resin, and at the same time at a high temperature It is to provide a biaxially oriented polyester film for optics that can effectively suppress the precipitation of oligomers that may occur and maintain transparency, and have excellent easy adhesion.

The above and other objects and advantages of the present invention will become more apparent from the following description of the preferred embodiment.

The object is an optical biaxially oriented polyester film made of polyester and comprising a base film stretched in at least one direction and a primer layer coated with a primer coating solution on one or both surfaces of the base film, at 150°C 1 When the heat treatment is performed for a period of time, the haze change amount before and after the heat treatment is 1% or less, and the primer coating solution includes an acrylic resin and a urethane resin having a carboxyl group and a hydroxyl group, and a carbodiimide or melamine compound, and the primer layer and UV curing type The adhesion between the coating layers of the acrylic resin, which is a resin, is achieved by a biaxially oriented polyester film for optics, characterized in that it is 95% or more after a moisture resistance test for 96 hours at 60°C and 90%RH.

Here, the acrylic resin is characterized in that it comprises 20 to 35% by weight based on the total weight of the primer coating liquid, and the urethane resin comprises 20 to 35% by weight based on the total weight of the primer coating liquid.

Preferably, the glass transition temperature of the acrylic resin and the urethane resin having the carboxyl group and the hydroxy group is characterized in that 40 to 80 ℃.

Preferably, the molar ratio of the carboxyl group and the hydroxy group is characterized by 1:3 to 1:5.

Preferably, the hydroxyl value of the acrylic resin and the urethane resin having the hydroxy group is characterized in that 10 to 300 mgKOH / g, respectively.

Preferably, the carbodiimide compound is characterized by having a cyclohexane or benzene ring group in the molecular skeleton.

Preferably, the carbodiimide or melamine compound is characterized in that it contains 30 to 60% by weight relative to the total weight of the primer coating solution.

Preferably, the primer coating solution is characterized in that it comprises a carbodiimide compound and a melamine compound at the same time.

Preferably, the primer coating solution is characterized in that it comprises organic or inorganic nanoparticles.

Preferably, the nanoparticles have an average particle diameter of 50 nm to 500 nm, and are characterized in that they contain 0.01 to 8% by weight based on the total weight of the primer coating solution.

According to the present invention, it is possible to improve the adhesion between an optical polyester film having a primer layer and a post-processing resin, for example, a functional optical resin such as a prism, adhesive coating or hard coating, and at the same time, oligomers that can occur at high temperatures It has an effect of effectively suppressing the precipitation phenomenon and maintaining transparency as an optical substrate.

Furthermore, the present invention has effects such as having excellent easy-adhesiveness.

However, the effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a schematic cross-sectional view of an optical biaxially oriented polyester film according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a film having a functional coating layer formed on an optical biaxially oriented polyester film according to one embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to examples and drawings of the present invention. These examples are only provided by way of example to illustrate the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples. .

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

All percentages, parts, ratios, etc. are by weight, unless otherwise stated. Also, if an amount, concentration, or other value or parameter is given as one of a range, a preferred range, or a list of preferred upper and lower limits, this is any upper and lower limit or desired value and any lower limit, regardless of whether the ranges are disclosed separately. It should be understood that all ranges formed from any pair of range limits or preferred values are specifically disclosed.

When a range of numerical values is referred to herein, unless stated otherwise, that range is intended to include the endpoints and all integers and fractions within the range. It is intended that the scope of the invention not be limited to the specific values recited when defining a range.

As used herein, "comprise", "comprising", "include", "including", "containing", "~ The terms characterized by, "has", "having", or any other variation thereof, are intended to cover non-exclusive inclusions. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to only those elements, and may include other elements not explicitly listed or inherent to such a process, method, article, or apparatus. It might be. Also, unless explicitly stated to the contrary, "or" refers to a generic'or' and not to an exclusive'or'.

It should be readily understood that if the applicant has defined the invention or parts thereof in open terms such as "comprising", the description should also be interpreted as describing the invention using the term "consisting essentially of" unless otherwise specified. do.

1 is a schematic cross-sectional view of an optical biaxially oriented polyester film according to an embodiment of the present invention, and is a schematic cross-sectional view of an optical biaxially oriented polyester film including a primer layer after primary processing, and FIG. 2 is As a schematic cross-sectional view of a film having a functional coating layer formed on a biaxially oriented polyester film for optics according to an embodiment, it is a schematic cross-sectional view of an optical biaxially oriented polyester film having a functional coating layer formed after secondary processing.

First, a cross-sectional schematic view of an optical biaxially oriented polyester film according to a preferred embodiment of the present invention will be described in detail with reference to FIG. 1, which is an optical biaxially oriented polyester film according to an aspect of the present invention.

As can be seen from FIG. 1, which is a schematic cross-sectional view of an optical biaxially oriented polyester film according to a preferred embodiment of the present invention, the optical biaxially oriented polyester film according to one embodiment has at least one side of the base film 1 The primer layer 2 is included. 1 is an embodiment in which a primer layer is formed on one surface of a base film, and a film having a primer layer on both surfaces of a base film is also included in the scope of the present invention.

Optical biaxially oriented polyester film according to an aspect of the present invention is made of polyester and is optically biaxially comprising a base film stretched in at least one direction and a primer layer coated with a primer coating liquid on one or both sides of the base film. As an oriented polyester film, when the heat treatment is performed at 150° C. for 1 hour, the haze change amount before and after heat treatment is 1% or less, and the primer coating liquid contains acrylic resin and urethane resin having carboxyl groups and hydroxy groups, and carbodiimide or melamine compounds And, the adhesion between the primer layer and the coating layer of the acrylic resin, which is a UV-curable resin, is at least 95% after a moisture resistance test at 60°C and 90%RH for 96 hours.

The base film (1) according to one embodiment is a polyester obtained by polymerizing dicarboxylic acid and glycol, dried as necessary, then melted and supplied with a known extruder to supply a single layer or composite layer from a slit die. It is preferable that the film is heat-treated after biaxial stretching after producing a non-stretched sheet after being solidified by cooling, solidifying, and then contacting the casting drum by a method such as electrostatic application after extruding to a sheet state. The dicarboxylic acid used in the polyester resin is terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenyl carboxylic acid, diphenyl sulfone dicarboxylic acid, zephenoxyethane dicarboxylic acid, 5-sodium sulfone dicarboxylic acid , Aromatic dicarboxylic acids such as phthalic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid, and paraoxybenzoic acid Oxycarbonic acid, etc., glycols are aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentin glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, Alicyclic glycols, such as cyclohexane dimethanol, aromatic glycols, such as bisphenol A and bisphenol S, can be used.

In consideration of mechanical strength, weather resistance, chemical resistance and transparency, it is preferable to use terephthalic acid or naphthalenedicarboxylic acid as dicarboxylic acid and ethylene glycol as glycol. In addition, it is preferable to use an alkaline earth metal type, a metal compound, a manganese compound, a cobalt compound, an aluminum compound, an antimony compound, a titanium compound, or a germanium compound as a catalyst during polymerization. These kinds of dicarboxylic acids and glycols or catalysts may be used in combination of two or more kinds.

In addition, particles may be added to the film raw material so that the film has functions such as running property, weather resistance, and heat resistance, but sufficient care is required in the amount of addition and material so as not to impair the transparency of the film. Therefore, it is desirable to add only a very small amount.

Moreover, as a stretching method of a film, a well-known technique, such as a method of biaxially stretching in the order of transverse stretching after longitudinal stretching, or a simultaneous biaxial stretching method of stretching both longitudinal and transverse directions at the same time, can be used. The preheating temperature and stretching temperature before stretching are 60 to 130°C, and the stretching ratio is 2.0 to 5.0 times. If necessary, heat treatment is performed at 140°C to 240°C after stretching.

In the present invention, a sequential biaxial stretching method in which a longitudinal stretching is followed by a transverse stretching is preferred.

The primer layer 2 according to an embodiment may be composed of an acrylic resin having a carboxyl group and a hydroxy group and a urethane resin and a thermosetting primer coating solution crosslinking with a carbodiimide or a melamine compound, whereby UV curing resin and good adhesion and Oligomer precipitation in the polyester film can be controlled.

The method of forming the primer layer is preferably performed in the step before the longitudinal stretching and before the transverse stretching in the biaxially stretched film forming process of the above-described film. In addition, any of several known coating methods such as bar coating method using meyer bar, gravure coating method, slit die coating method, comma coating method, etc. may be used, but the viscosity is low because a water-dispersed coating agent is used. In order to obtain excellent appearance, bar coating is preferred.

The primer layer of the biaxially oriented polyester film for optics according to the present invention can be cured through a UV curing system of 200 nm to 400 m and a UV curable resin formed on the primer layer through a primary thermal curing system, and then secondary post-processing. have. Here, the functional UV curable resin used in post-processing is generally selected as an acrylic resin. Accordingly, the acrylic resin and the urethane resin having a carboxyl group and a hydroxy group constituting the primer layer are covalently bonded to hydrogen bonds with an acrylic UV-curable resin that is positioned on the base film during post-processing, so that the adhesion can be improved more efficiently. Preferably, the optically biaxially oriented polyester film according to the present invention has an adhesive strength (adhesiveness) between a primer layer and a coating layer composed of an acrylic resin, which is a UV-curable resin, at 65° C., after 96 hours of moisture resistance test at 95° C. 95 % Or more.

In addition, precipitation of oligomers from the polyester film occurs in a high temperature environment such as a heating process during post-processing, thereby reducing transparency for optical use. The optically biaxially oriented polyester film according to the present invention has a carboxyl group and a hydroxyl group. By crosslinking the acrylic resin and the urethane resin with a carbodiimide or a melamine compound, oligomeric precipitation of the polyester film can be effectively suppressed in the primer layer coating film even in a high temperature environment, thereby maintaining transparency. Preferably, the optical biaxially oriented polyester film according to the present invention has a haze change amount of 1% or less before and after heat treatment when heat-treated at 150°C for 1 hour, and has excellent ease of adhesion to the polymer resin coating in post-processing. Have

In one embodiment according to the present invention, the primer layer is characterized by simultaneously applying an acrylic resin and a urethane resin having a carboxyl group and a hydroxy group as a binder resin.

At this time, the molar ratio of the carboxyl group and the hydroxy group is preferably 1:3 to 1:5. This is because, when the molar ratio is less than 1:5, the degree of crosslinking polymerization with a crosslinking agent may be lowered, whereas when the molar ratio exceeds 1:3, unreacted and excessively residual hydroxyl groups may decrease durability.

Acrylic resin is an acrylic polymer containing a structural unit derived from a carboxyl group-containing monomer and a hydroxy group (hydroxyl group)-containing monomer. The hydroxy group in the acrylic polymer is water-dispersible and reacts with a methylol group to form a crosslinked structure, thereby crosslinking the particles of the acrylic polymer, and finally reacting with a melamine crosslinking agent to crosslink particles of the acrylic polymer. In addition, among the acrylic polymers, a hydroxyl group that does not react with a melamine crosslinking agent can capture the hydrophilic oligomer deposited on the polyester film.

In addition, in the acrylic resin, the content rate of the sum of the content rate of the structural unit derived from the carboxyl group-containing monomer and the content rate of the structural unit derived from the hydroxy group-containing monomer is a predetermined range, and the content rate of the structural unit derived from the methylol group-containing monomer is a predetermined range. Therefore, the particle diameter of the acrylic polymer is easily reduced, and an easily adhesive layer having excellent transparency can be formed.

The carboxyl group-containing monomer used to form the acrylic resin is acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citraconic acid, cinnamic acid, 2-(meth)acryloyloxyethyl succinic acid, maleic acid Acid monohydroxy ethyl (meth) acrylate, fumaric acid monohydroxy ethyl (meth) acrylate, phthalic acid monohydroxy ethyl (meth) acrylate, 1,2-dicarboxycyclohexane monohydroxy ethyl (meth) acrylate , (Meth) acrylic dimer and ω-carboxy polycaprolactone mono (meth) acrylate, alone or in a mixture form.

In addition, the hydroxy group-containing monomer used for forming the acrylic resin has hydroxy groups such as N-methylol acrylamide having a hydroxyl group, alkyl (meth) acrylate, hydroxyethyl methacrylate, and polyalkylene glycol acrylate. Acrylate can be used. The acrylate having a hydroxy group may be used alone or in combination of two or more.

Urethane resins are prepared by the reaction of polyols and isocyanates. Examples of polyols include polyester polyols, polycarbonate polyols, polyether polyols, polyolefin polyols, and acrylic polyols, and these compounds may be used alone or in combination of two or more.

As a polyisocyanate compound used to obtain a polyurethane resin, xylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, triazine diisocyanate, etc. Aromatic diisocyanates, aliphatic diisocyanates having aromatic rings such as α,α,α',α'-tetramethyl xylylene diisocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexa And alicyclic diisocyanates such as aliphatic diisocyanates such as methylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and isopropylidene dicyclohexyl diisocyanate. . These may be used alone or in combination of two or more. Moreover, these polyisocyanate compounds may be a trimer, such as a dimer or an isocyanur ring, or a polymer of more than that.

As polyester polyols, polyhydric carboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, acrylic acid, etc.) or their acid anhydrides and Polyhydric alcohols (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1 ,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2-methyl- 2-propyl-1,3-propanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl- 2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1, What can be obtained from the reaction of 3-propanediol, cyclohexanediol, bishydroxymethylcyclohexane, dimethanol benzene, bishydroxyethoxybenzene, alkyldialkanolamine, lactonediol, triethylolpropane, etc., poly And those having derivative units of lactone compounds such as caprolactone.

In addition, the hydroxyl value of the acrylic resin and the urethane resin having a hydroxy group according to the present invention is preferably 10 to 300 mgKOH/g, respectively. When the hydroxyl group value is less than 10 mgKOH/g, the degree of crosslinking polymerization of the resin and the crosslinking agent may decrease, whereas when the hydroxyl group value exceeds 300 mgKOH/g, unreacted and excessively residual hydroxyl groups may degrade durability. Because there is.

The acrylic resin contained in the primer coating solution according to the present invention is preferably 20 to 35% by weight based on the total weight of the primer coating solution, and the urethane resin preferably contains 20 to 35% by weight based on the total weight of the primer coating solution, acrylic resin and urethane It is more preferable that the resin has a glass transition temperature (Tg) of 40 to 80°C. This can reduce the effect of inhibiting the oligomer precipitation of the polyester film when the content of the acrylic resin and the urethane resin is less than 20% by weight or the glass transition temperature is less than 40°C, and exceeds 35% by weight or the glass transition temperature exceeds 80°C. It is preferable to be in the above range because there is a possibility of cracking in the primer layer during the lowering of the adhesive strength and the film forming process of the biaxially oriented film.

The carbodiimide compound used in the primer coating liquid according to the present invention refers to having two or more carbodiimide groups in a molecule, for example, as disclosed in Japanese Patent Application Laid-Open Nos. Hei 10-316930 or Hei 11-140164 Likewise, it is produced using organic polyisocyanate, particularly preferably organic diisocyanate as the main synthetic raw material. These diisocyanates include hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, xylylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,12-diisocyanate dodecane, norbornane diisocyanate And 2,4-bis-(8-isocyanate octyl)-1,3-dioctylcyclobutane, 4,4`-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate and isophorone diisocyanate. One type or two or more types of diisocyanate are mentioned. It is preferable that the carbodiimide compound has a cyclohexane or benzene ring group in the molecular skeleton.

The melamine compound used in the primer coating solution according to the present invention is not particularly limited, but from the viewpoint of hydrophilization, methyl alcohol, ethyl alcohol, isopropyl alcohol as a lower alcohol in the methirolated melamine derivative obtained by condensation of melamine and formaldehyde Etherified compounds etc. are preferred by dehydrating and condensing, etc., and when the resin layer of the present invention is installed on a thermoplastic resin film to form a laminated film, not only the effect of suppressing the oligomer of the resin layer, but also with various inks and hard coat agents, etc. Adhesiveness and moisture-heat adhesiveness, flexibility, toughness, and solvent resistance are high, and can be preferably used. Examples of the methirolated melamine derivatives include monomethyrol melamine, dimethyrol melamine, trimethyrol melamine, tetramethyrol melamine, pentamethyrol melamine, and hexamethoxymethylol melamine.

The carbodiimide or melamine compound contained in the primer coating solution according to the present invention is preferably 30 to 60% by weight based on the total weight of the primer coating solution. If the composition ratio of the carbodiimide or melamine compound is less than 30% by weight, the polymer crosslinking degree is insufficient, and thus the effect of suppressing the oligomer precipitation of the polyester film may be reduced. And it is preferable to fall within the above range because there is a possibility of cracking in the primer layer or damage to the appearance of the product during the film forming process of the biaxially oriented film.

In addition, it is most preferable that the primer coating solution includes a carbodiimide compound and a melamine compound at the same time. In this case, since the adhesive strength and the haze change amount before and after the heat treatment are the best, after the excellent adhesion and moisture resistance test, the optimized physical properties in a high temperature and humidity environment are improved. Because it can.

Further, in order to have functions such as running property, weather resistance, and heat resistance of the film, particles may be added to the film raw material, but sufficient attention must be paid to the amount and material of the film so as not to impair the transparency of the film. The added amount is preferably a very small amount, more preferably not added. From the viewpoint of the running property of the film, it is preferable to assist by adding particles of the primer layer.

It is preferable that the primer coating liquid according to the present invention contains organic or inorganic nanoparticles. This is to prevent scratching of the base film during the process.

The average particle diameter of the nanoparticles is usually 1.0 μm or less, preferably 50 nm to 500 nm, from the viewpoint of transparency of the film. Moreover, when it is necessary to further improve the slipperiness and the blocking improvement effect, it is preferable to use particles having an average particle diameter larger than the film thickness of the primer layer. Examples of the particles to be used include inorganic particles such as silica, alumina, and metal oxide, and organic particles such as crosslinked polymer particles. Particularly, silica particles are suitable from the viewpoint of dispersibility to the primer layer and transparency of the resulting coating film.

In addition, it is preferable that the nanoparticles contain 0.01 to 8% by weight based on the total weight of the primer coating solution.

In addition, in the range that does not impair the gist of the present invention, an antifoaming agent, a coating agent improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, a pigment, etc. may be used in combination to form a primer layer, if necessary. good.

In the coating process of the primer coating solution according to the present invention, it is preferable to prepare a polyester film including a primer layer by applying a coating solution adjusted to a solid content concentration of 0.1 to 50% by weight on a polyester film.

Moreover, in the range which does not impair the gist of the present invention, an organic solvent may be contained in the coating liquid for the purpose of improving dispersibility with water, improving film formability, and the like. One type of organic solvent may be used, or two or more types may be appropriately used.

The thickness of the primer layer after drying according to the present invention is usually 0.002 to 1.0 μm, preferably 0.005 to 0.5 μm, and more preferably 0.01 to 0.2 μm. This is because when the film thickness is out of the above range, adhesion, coating appearance, and blocking characteristics deteriorate. In addition, the primer layer in the present invention has excellent adhesive strength even when the film thickness is small.

In addition, the optical biaxially oriented polyester film according to the present invention is basically applied to the field of transparent optical film, so that the total light transmittance of the surface of the base film on which the primer layer is formed is 80% or more, and the haze value is preferably 0.4 to 2.4%. .

Hereinafter, the configuration of the present invention and its effects will be described in more detail through examples and comparative examples. However, this example is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

The components used in Examples and Comparative Examples of the present invention are as follows, and may be respectively named by their abbreviated names.

(A1) acrylic resin

The composition ratio was composed of 2 mol of N-methylol acrylamide, 67.5 mol of methyl methacrylate, 14.5 mol of ethyl acrylate, 16 mol of 2-hydroxyethyl methacrylate, and 2.9 mol of acrylic acid. While maintaining at 60°C, emulsion polymerization was performed with an aqueous solution of ammonium persulfate and an aqueous solution of sodium metabisulfite, and the OH Value of 100 mgKOH/g was maintained, and the glass transition temperature (Tg) was set to 60°C. Thereafter, the obtained emulsion polymerization product was aged at 60° C. for 2 hours, cooled to room temperature, and then adjusted to pH 9.0 with an appropriate amount of aqueous ammonia solution to prepare a desired aqueous polyacrylic dispersion.

(A2) acrylic resin

The composition ratio was composed of 2 mol of N-methylol acrylamide, 67.5 mol of methyl methacrylate, 9.5 mol of ethyl acrylate, 16 mol of 2-hydroxyethyl methacrylate, and 7.9 mol of acrylic acid. While maintaining at 60°C, emulsion polymerization was performed with an aqueous solution of ammonium persulfate and an aqueous solution of sodium metabisulfite, and the OH Value of 100 mgKOH/g was maintained, and the glass transition temperature (Tg) was 90°C. Thereafter, the obtained emulsion polymerization product was aged at 60° C. for 2 hours, cooled to room temperature, and then adjusted to pH 9.0 with an appropriate amount of aqueous ammonia solution to prepare a desired aqueous polyacrylic dispersion.

(A3) Acrylic resin

The composition ratio was composed of 2 mol of N-methylol acrylamide and 67.5 mol of ethyl acrylate, 16.5 mol of n-butyl acrylate, 10 mol of methyl methacrylate, and 4 mol of acrylic acid. While maintaining at 60°C, emulsion polymerization was performed with an aqueous solution of ammonium persulfate and an aqueous solution of sodium metabisulfite, and the OH value of 5 mgKOH/g or less was maintained, and the glass transition temperature (Tg) was set to 60°C. Thereafter, the obtained emulsion polymerization product was aged at 60° C. for 2 hours, cooled to room temperature, and then adjusted to pH 9.0 with an appropriate amount of aqueous ammonia solution to prepare a desired aqueous polyacrylic dispersion.

(A4) Acrylic resin

The composition ratio was composed of 2 mol of N-methylol acrylamide and 59.5 mol of ethyl acrylate, 14.5 mol of n-butyl acrylate, 10 mol of methyl methacrylate, and 14 mol of acrylic acid. While maintaining at 60°C, emulsion polymerization was performed with an aqueous solution of ammonium persulfate and an aqueous solution of sodium metabisulfite, maintaining an OH value of 5 mgKOH/g or less, and having a glass transition temperature (Tg) of 90°C. Thereafter, the obtained emulsion polymerization product was aged at 60° C. for 2 hours, cooled to room temperature, and then adjusted to pH 9.0 with an appropriate amount of aqueous ammonia solution to prepare a desired aqueous polyacrylic dispersion.

(B1) Urethane resin

The composition ratio was obtained by polymerization using 25 mol of adipic acid and 25 mol of terephthalic acid, 25 mol of ethylene glycol, 25 mol of neopentyl glycol, and 8 mol of trimethylolpropane to obtain a polyol having an OH Value of 100 mgKOH/g, and then 250 g of the polyol and dimethylol propionic acid ( DMPA) 35g, isoprene diisocyanate (IPDI) 89g was reacted under 0.5wt% of catalytic dibutyltin dilaurate (DBTDL) by a general prepolymer mixing method to obtain a prepolymer having an isocyanate terminal and a glass transition temperature of 60°C. Triethylamine (TEA) was quantitatively added as a neutralizing material, and an aqueous dispersion was obtained by high-speed stirring. Here, 10 g of ethylenediamine was added to expand the chain to prepare a desired aqueous dispersion of polyurethane.

(B2) Urethane resin

The composition ratio is 25 mol of adipic acid, 35 mol of terephthalic acid, 25 mol of ethylene glycol, and 35 mol of neopentyl glycol to obtain a polyol having an OH Value of 5 mgKOH/g or less, and then 250 g of the polyol and 35 g of dimethylol propionic acid (DMPA), iso 89 g of prodiisocyanate (IPDI) was reacted under 0.5 wt% of catalytic dibutyltin dilaurate (DBTDL) by a general prepolymer mixing method to obtain a prepolymer having an isocyanate terminal and a glass transition temperature of 90°C. After quantitatively adding TEA as a neutralizing material, an aqueous dispersion was obtained by high-speed stirring. Here, 10 g of ethylenediamine was added to expand the chain to prepare a desired aqueous dispersion of polyurethane.

OH Value measurement and glass transition temperature measurement for the components of (A1), (A2), (A3), (A4), (B1), and (B2) described above were performed as follows.

1. Check the OH value (hydroxyl value)

15 g of the sample to be measured for the above-mentioned (A1), (A2), (A3), (A4), (B1), (B2) was placed in a beaker, and 3 drops of the phenolphthalein indicator were added, followed by 0.1 N potassium hydroxide ( It was titrated with KOH) and added until colorless to light pink. After the color changed, the input amount was checked, and the acid value was first calculated by the following Equation 1.

(Equation 1)

Acid value (mgKOH/g) = 56.11 N (B-C)/S

N: Normal concentration of 0.1 N KOH aqueous solution

B: volume of the titrant consumed in the blank test (ml)

C: volume of titrant consumed in this test (ml)

S: Weight of the sample (g)

After that, the acetylation reagent was reacted with OH according to the method of ASTM E222-10, and the excess acid was titrated with 0.1N potassium hydroxide (KOH) to calculate the hydroxyl value by calculating with Equation 2 below.

(Equation 2)

Hydroxyl value (mgKOH/g) = 56.11 N (B-C)/S + acid value

N: Normal concentration of 0.1N KOH aqueous solution

B: volume of the titrant consumed in the blank test (ml)

C: volume of titrant consumed in this test (ml)

S: Weight of the sample (g)

2. Check the glass transition temperature

It was measured by DCS (Differential Scanning Calorimetry) of TA. The measurement temperature range was -30°C to 200°C twice scanned at 10°C per minute, and the measured glass transition temperature was measured for the glass transition temperature during the second scan.

Other components of the compounds used in Examples and Comparative Examples of the present invention are as follows.

(C1) Carbodiimide-based compound

A polycarbodiimide compound containing a cyclohexane structure having a carbodiimide equivalent of 430 g/mol

(C2) Melamine-based compound

Hexamethoxymethylol melamine

(C3) oxazoline-based compounds

Polymer-based dispersion of oxazoline

(Nippon Shokubai Co., Ltd. Epocross (registered trademark) WS-500)

(D1) particles

Silica sol with an average particle size of 0.1㎛

[Examples 1 to 3]

The method of manufacturing the polyester film used as the base film for applying the primer coating solution in the present invention is as follows.

First, the polyethylene terephthalate resin pellet was dried under reduced pressure (1.3 hPa) at 135° C. for 6 hours, then fed to an extruder, melt-extruded onto a sheet at about 280° C., and on a metal roll maintained at a surface temperature of 20° C. It was rapidly cooled to obtain a casting film with a thickness of 1024 µm.

Next, the casting film is heated to a heated roll group and an infrared heater at 100° C., and then stretched at a draw ratio of 3.2 times in the longitudinal direction to a roll group with a main speed difference to obtain a uniaxially oriented PET film and use it as a substrate. Did. Subsequently, the film was gripped at the end with a clip, introduced into a hot air area, and dried. Thereafter, the film was stretched at a stretching ratio of 3.2 times in the transverse direction at 130°C, heat-set at 240°C, and then transversely relaxed at 200°C by 3%. Thus, a biaxially oriented polyester film for optics having a thickness of 100 µm was prepared.

During the manufacturing process of the polyester base film, after applying a 3.2 times stretching ratio in the longitudinal direction, a coating solution forming a primer layer is coated with a reverse roll method so that the solid content weight is 0.08 g/m 2 on one side of the uniaxially oriented PET film. It was additionally inserted and the composition of the coating liquid is shown in Table 1 below.

In addition, each component was adjusted in an equal ratio as shown in Table 1 below, and was summarized as an abbreviated name as described above, and the total molecular weight in all examples was adjusted to be 10,000 g/mol or less.

In addition, the final thickness after drying of the primer layer to which the coating solution was applied is 0.1 μm.

division Components of primer layer Weight ratio Example 1 A1 / B1 / C1 / D1 30/30/40 / 0.05 Example 2 A1 / B1 / C2 / D1 30/30/40 / 0.05 Example 3 A1 / B1 / C1 / C2 / D1 30/30/20/20 / 0.05

[Comparative Example 1]

A biaxially oriented polyester film for optics was prepared in the same manner as in Example 1, except that the primer layer was not formed.

[Comparative Examples 2 to 19]

An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that the primer layer was composed of a coating solution having the components and contents shown in Table 2 below.

division Components of primer layer Weight ratio Comparative Example 1 - - Comparative Example 2 A2 / B2 / C1 / D1 30/30/40 / 0.05 Comparative Example 3 A2 / B2 / C2 / D1 30/30/40 / 0.05 Comparative Example 4 A2 / B2 / C3 / D1 30/30/40 / 0.05 Comparative Example 5 A2 / B2 / C1 / C2 / D1 30/30/20/20 / 0.05 Comparative Example 6 A2 / B2 / C2 / C3 / D1 30/30/20/20 / 0.05 Comparative Example 7 A2 / B2 / C1 / C3 / D1 30/30/20/20 / 0.05 Comparative Example 8 A3 / B2 / C1 / D1 30/30/40 / 0.05 Comparative Example 9 A3/B2/C2/D1 30/30/40 / 0.05 Comparative Example 10 A3 / B2 / C3 / D1 30/30/40 / 0.05 Comparative Example 11 A3 / B2 / C1 / C2 / D1 30/30/20/20 / 0.05 Comparative Example 12 A3 / B2 / C2 / C3 / D1 30/30/20/20 / 0.05 Comparative Example 13 A3 / B2 / C1 / C3 / D1 30/30/20/20 / 0.05 Comparative Example 14 A4 / B2 / C1 / D1 30/30/40 / 0.05 Comparative Example 15 A4 / B2 / C2 / D1 30/30/40 / 0.05 Comparative Example 16 A4 / B2 / C3 / D1 30/30/40 / 0.05 Comparative Example 17 A4 / B2 / C1 / C2 / D1 30/30/20/20 / 0.05 Comparative Example 18 A4 / B2 / C2 / C3 / D1 30/30/20/20 / 0.05 Comparative Example 19 A4 / B2 / C1 / C3 / D1 30/30/20/20 / 0.05

[Comparative Examples 20-22]

An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that the primer layer was composed of a coating solution having the components and contents shown in Table 3 below.

division Components of primer layer Weight ratio Comparative Example 20 A1 / B1 / C3 / D1 30/30/40 / 0.05 Comparative Example 21 A1 / B1 / C2 / C3 / D1 30/30/20/20 / 0.05 Comparative Example 22 A1 / B1 / C1 / C3 / D1 30/30/20/20 / 0.05

Using the optical biaxially oriented polyester film according to Examples 1 to 3 and Comparative Examples 1 to 22, physical properties were measured through the following experimental examples and the results are shown in Table 4 below.

[Experimental Example]

1. Haze confirmation before and after heat treatment and calculation of change amount

For the films prepared in Examples and Comparative Examples, haze was measured using a HAZE meter manufactured by NIPPON DENSHOKU.

After measuring Haze, the sample was taken out at 150° C. for 1 hour using an electric dryer, and the haze was re-measured using a HAZE meter manufactured by NIPPON DENSHOKU. When physical properties were measured after heat treatment, the amount of change before and after heat treatment was calculated. The average of the measured values of 10 identical samples was calculated.

2. Measurement of adhesion after room temperature adhesion and moisture resistance test

The adhesive strength between the primer layers was measured in a room temperature and humidity atmosphere. After applying the acrylic UV cured resin to the surface where the primer layer is adhered by using #20 wire bar, make a cutting line on the primer layer coated film with a cutter, and cut 1 mm x 1 mm squares into a 10 x 10 matrix. Was placed. Cellophane tape (No. 405, manufactured by NICHIBAN; width: 24 mm) was attached to the film having a cutting line, and the tape was rubbed and strongly attached to the film using velvet, and then the tape was removed vertically. The area of the primer layer remaining on the coating layer was visually observed, and adhesiveness (adhesion) was calculated by the following equation (3).

(Equation 3)

In addition, evaluation of adhesion after the moisture resistance test after 96 hours under 60°C and 90% RH was also performed in the same manner as above.

division Haze change amount before and after heat treatment (ΔHaze) Adhesion at room temperature
(%) Adhesion after moisture resistance test
(%) Example 1 0.8 100 95 Example 2 1.0 100 97 Example 3 0.5 100 98 Comparative Example 1 14.5 0 0 Comparative Example 2 0.9 70 50 Comparative Example 3 0.8 65 65 Comparative Example 4 3.6 65 65 Comparative Example 5 0.4 75 65 Comparative Example 6 1.9 70 70 Comparative Example 7 1.9 70 70 Comparative Example 8 2.6 95 95 Comparative Example 9 1.9 90 90 Comparative Example 10 3.1 95 95 Comparative Example 11 2.1 90 90 Comparative Example 12 2.8 95 90 Comparative Example 13 3.3 95 95 Comparative Example 14 9.6 70 50 Comparative Example 15 6.1 50 20 Comparative Example 16 8.5 5 0 Comparative Example 17 7.5 50 40 Comparative Example 18 6.9 30 20 Comparative Example 19 10.7 20 20 Comparative Example 20 3.0 80 75 Comparative Example 21 1.8 90 75 Comparative Example 22 2.0 90 80

As can be seen in Table 4, when comparing the films of Examples 1 to 3 according to the present invention with the films of Comparative Examples 1 to 22, acrylic (A1) and urethane (B1) having a carboxyl group and a hydroxy group as primer components are used. The applied example had a lower haze change amount before and after the heat treatment under the same conditions than the comparative example, and both the adhesion at room temperature and the moisture resistance test were excellent. In particular, when looking at the results of Example 3 in which the carbodiimide compound (C1) and the melamine compound (C2) were applied at the same time, it can be seen that the adhesive strength and the change in haze before and after heat treatment are the best compared to other examples. As shown in Example 3, when applying acrylic (A1) and urethane (B1) having a carboxyl group and a hydroxy group, and using a carbodiimide and a melamine compound at the same time, it can be confirmed that it has optimized properties in a high temperature and humidity environment.

On the other hand, as in the measurement results of the properties of the film according to the comparative example, after the adhesive strength and moisture resistance test, the adhesive strength and the film according to the comparative examples 2 to 19 are relatively good compared to the film of the comparative example 1 without the primer layer, but compared to the examples It was confirmed that the adhesion was relatively weak, and in particular, it was affected by the glass transition temperature. On the other hand, the reduction in OH-Value also tended to deteriorate the haze change after heat treatment.

In addition, it can be seen that the films of Comparative Examples 20, 21, and 22 using or combining the oxazoline compound (C3) had deteriorated adhesive strength and haze change amount before and after heat treatment.

As described above, according to the present invention, a polyester film for laminating optics is applied with a two-type binder system to improve the post-processing layer and adhesion, and a polyester film at high temperature with an efficient cross-linking effect by applying the two-crosslinking agent system It is possible to improve the effect of inhibiting the precipitation of oligomers. Because of this, it is easy to have uniform adhesion and heat resistance in a high-temperature process after processing of a functional optical coating such as a substrate and a prism, adhesion, or hard coating. It is possible to prevent clouding or whitening, and it is possible to achieve high quality by securing product productivity and reducing defect rates.

In this specification, only a few examples of various embodiments performed by the present inventors are described, but the technical spirit of the present invention is not limited to or limited thereto, and can be variously implemented by a person skilled in the art.

1: Polyester base film
2: Primer layer
3: Functional coating layer (2nd UV post-processing)

Claims (10)

A base film made of polyester and stretched in at least one direction,
As an optical biaxially oriented polyester film comprising a primer layer coated with a primer coating liquid on one or both sides of the base film,
When heat treated at 150° C. for 1 hour, the haze change amount before and after heat treatment is 1% or less,
The primer coating solution includes an acrylic resin and a urethane resin having a carboxyl group and a hydroxy group and a carbodiimide or melamine compound,
The glass transition temperature of the acrylic resin and the urethane resin having the carboxyl group and the hydroxy group is 40 to 80°C, respectively, and the hydroxyl group values of the acrylic resin and the urethane resin are 10 to 300 mgKOH/g, respectively.
The adhesiveness between the primer layer and the coating layer of an acrylic resin, which is a UV-curable resin, is a biaxially oriented polyester film for optics, characterized in that it is 95% or more after a moisture resistance test for 96 hours at 60°C and 90%RH. According to claim 1,
The acrylic resin contains 20 to 35% by weight based on the total weight of the primer coating solution,
The urethane resin is a biaxially oriented polyester film for optics, characterized in that it comprises 20 to 35% by weight based on the total weight of the primer coating solution. delete According to claim 1,
The molar ratio of the carboxyl group and the hydroxy group is 1:3 to 1:5 optical biaxially oriented polyester film, characterized in that. delete According to claim 1,
The carbodiimide compound is an optical biaxially oriented polyester film, characterized by having a cyclohexane or benzene ring group in the molecular skeleton. According to claim 1,
The carbodiimide or melamine compound is biaxially oriented polyester film for optics, characterized in that it contains 30 to 60% by weight based on the total weight of the primer coating solution. According to claim 1,
The primer coating solution is an optical biaxially oriented polyester film comprising a carbodiimide compound and a melamine compound at the same time. According to claim 1,
The primer coating liquid is biaxially oriented polyester film for optics, characterized in that it comprises organic or inorganic nanoparticles. The method of claim 9,
The nanoparticles have an average particle diameter of 50 nm to 500 nm, and the optical film for biaxially oriented polyester, characterized in that it contains 0.01 to 8% by weight based on the total weight of the primer coating solution.

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