KR20220128756A - Optical polyester film and laminated film including the same - Google Patents

Abstract

Provided are an optical polyester film and a laminated film comprising the same. The optical polyester film comprises: a polyester base film; and a primer layer disposed on at least one surface of the base film, wherein the primer layer has a thickness of 4 x 10^-4 to 2 x 10^-3 relative to the total thickness of the optical polyester film and has a Young's modulus of 1000 MPa or less at 25 ℃. The optical polyester film can maintain transparency by preventing oligomer precipitation by heat treatment while having excellent adhesiveness.

Description

Optical polyester film and laminated film including the same

It relates to an optical polyester film and a laminated film comprising the same.

Polyester film has excellent dimensional stability, thickness uniformity, and optical transparency, so it has a very wide range of uses as not only display devices but also various industrial materials. Among them, an optical polyester film is a plastic film used for optics, and in more detail, is widely used as a component of a display device.

The optical polyester film can be used for various purposes by applying various resins through post-processing as a base film. At this time, the optical polyester film requires uniform adhesion to the resin applied by post-processing. In addition, in the optical polyester film, oligomer precipitation occurs from the film containing the thermoplastic resin used when heat treatment is performed during post-processing, and whitening or contamination occurs on the film surface.

Therefore, there is a demand for an optical polyester film capable of maintaining transparency by preventing oligomer precipitation by heat treatment while having excellent easy adhesion, and a laminated film including the same.

One aspect is to provide an optical polyester film capable of maintaining transparency by preventing oligomer precipitation by heat treatment while having excellent easily adhesive properties.

Another aspect is to provide a laminated film including the optical polyester film.

According to one aspect,

An optical polyester film comprising:

polyester base film; and

a primer layer disposed on at least one surface of the base film; and

The primer layer has a thickness of 4x10 ^-4 to 2x10 ^-3 compared to the overall thickness of the optical polyester film,

An optical polyester film having a Young's modulus of 1000 MPa or less at 25°C is provided.

A water contact angle with respect to the surface of the primer layer may be 55° to 70°.

The refractive index of the primer layer may be 1.50 to 1.51.

The primer layer includes an acrylic resin having a carboxyl group, a polyalkylene oxide-based resin, and a crosslinking agent,

The content of the acrylic resin and polyalkylene oxide-based resin having a carboxyl group may be 40 to 70% by weight based on 100% by weight of the entire primer layer,

The content of the crosslinking agent may be 30 to 50% by weight based on 100% by weight of the entire primer layer.

The weight ratio of the acrylic resin having the carboxyl group and the polyalkylene oxide-based resin may be 3:1 to 7:1.

The crosslinking agent may include at least one selected from a melamine-based compound, an isocyanate-based compound, or a carbodiimide-based compound.

The primer layer may include inorganic particles, organic particles, or a combination thereof.

The total light transmittance may be 94% or more.

Haze change amount (ΔHAZE) can be satisfied before and after heat treatment according to Equation 1:

[Equation 1]

△HAZE ≤ 1%

In the formula,

ΔHAZE may be a difference obtained by subtracting a haze value (%) measured before heat treatment from a haze value (%) measured after heat-treating the film at 150°C and leaving it to stand for 1 hour.

The polyester base film may be a biaxially oriented polyester base film.

According to another aspect,

A laminated film comprising the above-described optical polyester film, wherein a functional coating layer is further disposed on the primer layer of the optical polyester film is provided.

The functional coating layer may include a prism layer, an adhesive layer, a hard coating layer, a UV curing layer, a thermosetting layer, a printing layer, or a combination thereof.

The adhesive force (%) at room temperature according to the following formula 2 and the adhesion force (%) after standing for 96 hours under conditions of 60 °C and 90% relative humidity can be satisfied:

[Equation 2]

Adhesion (%) = a/A x 100 ≥ 95%

In the formula,

A is the total area in contact with the primer layer and the functional coating layer,

a is the area of the portion attached between the primer layer and the functional coating layer.

The optical polyester film according to an embodiment includes a polyester base film and a primer layer disposed on at least one surface of the base film, wherein the primer layer is 4x10 ^-4 to 2x10 compared to the total thickness of the optical polyester film It has a thickness of ^-3 and has a Young's modulus of 1000 MPa or less at 25°C. The optical polyester film can maintain transparency by preventing oligomer precipitation by heat treatment while having excellent easily adhesive properties.

1 is a cross-sectional view of an optical polyester film according to an embodiment.
2 is a cross-sectional view of a laminated film according to an exemplary embodiment.

Hereinafter, an optical polyester film and a laminated film including the same will be described in detail with reference to embodiments and drawings of the present invention. It will be apparent to those of ordinary skill in the art that these examples are only presented as examples to explain the present invention in more detail, and 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. Also, 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.

In the present specification, the term "included" means that other components may be further included, rather than excluding other components, unless otherwise stated.

As used herein, the term “combination of these” means a mixture or combination with one or more of the described components.

As used herein, the term “and/or” is meant to include any and all combinations of one or more of the related listed items. As used herein, the term “or” means “and/or”. The expression "at least one" or "one or more" in front of elements in the present specification does not mean that it can modify the entire list of elements and can modify individual elements of the description.

In the present specification, when it is stated that an element is disposed "on" or "above" another element, one element may be disposed directly on the other element, or the elements interposed between the elements are may exist. On the other hand, when an element is referred to as being disposed "directly on" or "directly on" another element, intervening elements may not be present.

In the present specification, "~-based resin (polymer)" is a broad concept including both "~ resin (polymer)" or/and "~ resin (polymer) derivative".

As used herein, the term “compound” is a broad concept that includes both single compounds, oligomers, and polymers.

Unless otherwise stated, all percentages, parts, ratios, etc. are by weight. Also, when an amount, concentration, or other value or parameter is given as any one of a range, a preferred range, or a list of upper and preferred upper limits and lower preferred limits, this means any upper range limit or preferred value and any lower limit, whether or not the range is separately disclosed. It is to 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 recited herein, unless otherwise stated, the 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 particular values recited when defining the ranges.

In general, a method of designing a resin layer using a resin having an acryloyl group, a resin layer having a styrene and acrylic acid structure, or / and an acrylic modified polyester for the purpose of suppressing oligomer precipitation on an optical polyester film is used have.

However, even if the resin having an acryloyl group or a resin layer having a styrene and acrylic acid structure is designed, the adhesive force with the polyester base film is sufficient, but the heat-resistant adhesion and moisture-resistant adhesion are reduced, and the water contact angle is high, so the prism processing layer, lens When post-processing including a functional coating layer such as a processing layer, an anti-reflection layer or a hard coating layer, easy adhesion is very poor.

Even if the resin layer is designed using the acrylic modified polyester, defects or cracks occur in the resin layer when curing the resin component having a low glass transition temperature in addition to the acrylic component having a glass transition temperature (T _g ) of a certain temperature or higher. It reduces the transparency of the laminated film. In addition, not only does a sufficient oligomer suppression effect not appear in the design of the resin layer, but also because the Young's modulus of the resin layer is too high, easy adhesion during post-processing may be reduced.

Therefore, for the optical polyester film used as the base film, it is required to maintain the transparency as the optical base material through uniform adhesion with the resin used in the post-processing and suppression of oligomer precipitation.

The inventor of the present invention intends to propose the following optical polyester film and a laminated film including the same by paying attention to this point.

1 is a cross-sectional view of an optical polyester film according to an embodiment.

Referring to FIG. 1 , in an optical polyester film 100 according to an embodiment, a polyester base film 1 and a primer layer 2 are arranged in this order.

An optical polyester film 100 according to an embodiment includes a polyester base film (1); and a primer layer (2) disposed on at least one surface of the base film (1), wherein the primer layer (2) is 4x10 ^-4 to 2x10 ^-3 compared to the total thickness of the optical polyester film 100 has a thickness of , and may have a Young's modulus of 1000 MPa or less at 25 °C.

The optical polyester film 100 can maintain transparency by preventing precipitation of oligomers by heat treatment while having excellent easily adhesive properties.

Hereinafter, a polyester base film (1), a primer layer (2), an optical polyester film (100), and a laminated film including the same will be described in detail.

[Polyester base film (1)]

The polyester base film 1 according to an embodiment may be manufactured as follows, but is not limited thereto.

Polyester obtained by polymerizing dicarboxylic acid and glycol is dried as necessary, then melted and supplied by a known extruder, and extruded from a slit die into a single-layer or multi-layer sheet state. Thereafter, the polyester in the sheet state is adhered to the casting drum by an electrostatic application or the like and solidified by cooling to prepare an unstretched sheet, and heat treatment after biaxial stretching to prepare the polyester base film 1 .

Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenyl carboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, 5-sodium sulfone dicarboxylic acid, and phthalic acid; aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, maleic acid, and fumaric acid; alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid; and oxycarboxylic acids such as paraoxybenzoic acid; and the like. Examples of the glycol include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentine glycol; polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol and polypropylene glycol; alicyclic glycols such as cyclohexane dimethanol; and aromatic glycols such as bisphenol A and bisphenol S; and the like.

In consideration of mechanical strength, weather resistance, chemical resistance, transparency, etc., terephthalic acid or naphthalenedicarboxylic acid as the dicarboxylic acid and ethylene glycol may be used as the glycol. In addition, alkaline earth metal compounds as catalysts during polymerization; metal compounds; and transition metal compounds such as manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, and germanium compounds; etc. can be used. Two or more types of dicarboxylic acids and glycols or catalysts may be used, respectively.

In addition, inorganic particles and/or organic particles may be added to the raw material of the polyester base film 1 so as to have functions such as running properties, weather resistance, and heat resistance, but may be added in a small amount within a range that does not impair the transparency of the film.

The polyester base film 1 may be a biaxially oriented polyester base film. As the biaxial stretching method, a known technique such as a sequential biaxial stretching method of stretching in the longitudinal direction and then sequentially stretching in the transverse direction or a simultaneous biaxial stretching method of stretching almost simultaneously in the longitudinal and transverse directions may be used. The preheating temperature and the stretching temperature before stretching may be 60 to 130° C., and the stretching ratio may be 2.0 to 5.0 times. If necessary, heat treatment may be performed at 140° C. to 240° C. after stretching. For example, the polyester base film 1 may use a sequential biaxial stretching method.

[Primer layer (2)]

The primer layer 2 according to an embodiment may have a thickness of 4x10 ^-4 to 2x10 ^-3 compared to the overall thickness of the optical polyester film 100 . For example, the primer layer 2 may have a thickness of 1x10 ^-4 to 1x10 ^-3 compared to the overall thickness of the optical polyester film 100 . If the primer layer 2 has a thickness of less than 4x10 ^-4 compared to the total thickness of the optical polyester film 100, the oligomer trapping ability is lowered and the oligomer precipitation cannot be suppressed. If the thickness of the primer layer 2 is greater than 2x10 ^-4 compared to the total thickness of the optical polyester film 100, the degree of crosslinking with the crosslinking agent is insufficient, so that non-curing occurs, and a large number of unreacted crosslinking reactive groups are generated, thereby forming the resin layer. The appearance may be poor or the adhesion with the polyester base film 1 may become insufficient.

A water contact angle with respect to the surface of the primer layer 2 may be 55° to 70°.

The refractive index of the primer layer 2 may be 1.50 to 1.51. If the refractive index of the primer layer 2 is out of the above range, the uniformity of the total light transmittance may be weakened or an appearance defect may occur due to optical interference with the functional coating layer in post-processing.

The primer layer 2 may include an acrylic resin having a carboxyl group, a polyalkylene oxide-based resin, and a crosslinking agent.

The acrylic resin having a carboxy group is an acrylic polymer including a structural unit derived from a monomer containing a carboxy group. 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 monohydroxyethyl (meth) acrylate, fumaric acid monohydroxyethyl (meth) acrylate, phthalic acid monohydroxyethyl (meth) acrylate, 1,2-dicarboxycyclohexane monohydroxyethyl (meth) acrylic rate, (meth) acrylic acid dimer, and ω-carboxy polycaprolactone mono (meth) acrylate. The carboxyl group-containing monomer may be used alone or in the form of a compound.

The glass transition temperature (T _g ) of the acrylic resin having a carboxy group may be 40 to 80 ℃. If the glass transition temperature (T _g ) of the acrylic resin having a carboxyl group is less than 40° C., the oligomer precipitation inhibitory effect of the optical polyester film 100 may be reduced. If the glass transition temperature (T _g ) of the acrylic resin having a carboxy group is greater than 80 ° C., the adhesion with the polyester base film 1 is reduced or the primer layer in the film forming process during biaxial stretching of the polyester base film 1 Appearance defects such as cracks or stretch marks in (2) may occur.

The polyalkylene oxide-based resin may be at least one resin selected from an ethylene oxide resin, a propylene oxide resin, or a butylene oxide resin. The polyalkylene oxide resin may have a weight average molecular weight (Mw) of 100 to 10000 g/mol. For example, the polyalkylene oxide-based resin may be represented by the following Chemical Formula 1:

[Formula 1]

In the formula, n is an integer from 2 to 200.

If the weight average molecular weight of the polyalkylene oxide-based resin is less than 100 g/mol, the degree of crosslinking with the acrylic resin having a carboxy group is insufficient to cause non-curing, so that the appearance of the primer layer 2 is poor or the polyester substrate The adhesive force with the film 1 becomes insufficient. If the weight average molecular weight of the polyalkylene oxide-based resin is more than 10000 g/mol, a large number of unreacted cross-linking reactants are generated to reduce the adhesion with the polyester base film (1) or the polyester base film (1) During the biaxial stretching, appearance defects such as cracks or stretching marks of the primer layer 2 may occur in the film forming process.

The content of the acrylic resin and polyalkylene oxide-based resin having a carboxyl group may be 40 to 70% by weight based on 100% by weight of the entire primer layer. The weight ratio of the acrylic resin having the carboxyl group and the polyalkylene oxide-based resin may be 3:1 to 7:1.

If the acrylic resin and the polyalkylene oxide-based resin having the carboxyl group have the above content and weight ratio ranges, the Young's modulus at 25° C. of 1000 MPa or less and the water contact angle with respect to the surface of the primer layer 2 are 55° to 70°. maintain. In the optical polyester film 100, not only the appearance of the primer layer 2 in the film forming process during biaxial stretching of the polyester base film 1 is good, but also the primer layer 2 for the polyester base film 1 At room temperature, both adhesion and moisture resistance are improved. In addition, if the acrylic resin and the polyalkylene oxide-based resin having the carboxyl group exceed the above weight ratio range, even if the Young's modulus of 1000 MPa or less is maintained, oligomer precipitation cannot be prevented, and thus the transparency of the appearance cannot be maintained. If the acrylic resin and polyalkylene oxide-based resin having the carboxyl group are less than the above weight ratio range, the Young's modulus of 1000 MPa or more is maintained, and the adhesion strength after the adhesion and moisture resistance test is not improved, and the water contact angle exceeds 70 ° or more.

Therefore, the optical polyester film 100 prepared in the appropriate range of the above content can maintain transparency by preventing oligomer precipitation by heat treatment while having excellent easy-adhesiveness.

The crosslinking agent may include at least one selected from a melamine-based compound, an isocyanate-based compound, or a carbodiimide-based compound.

The melamine-based compound may be a compound obtained by dehydration condensation reaction of methyl alcohol, ethyl alcohol, isopropyl alcohol, etc. as a lower alcohol with a methylol melamine derivative obtained by condensing melamine and formaldehyde to form an etherified compound. If the melamine-based compound is included in the primer layer 2, oligomer precipitation from the primer layer 2 is suppressed, as well as adhesiveness with various inks or hard coat agents that can be used on the primer layer 2 Heat-and-moisture adhesiveness, flexibility, toughness, solvent resistance, etc. may be improved. Examples of the methylolated melamine derivative include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, or hexamethoxymethylol melamine.

Examples of the isocyanate-based compound include aromatic diisocyanates such as xylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, methylenediphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and trizine diisocyanate; Aliphatic diisocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, etc. of aliphatic diisocyanates; and alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and isopropylidene dicyclohexyl diisocyanate. The isocyanate-based compound may be used alone or in combination of two or more. The isocyanate-based compound may be a dimer or a trimer such as an isocyanuric ring, or a polyisocyanate-based polymer that is a higher polymer.

In addition, the isocyanate-based compound requires a blocking agent capable of reacting with a functional group located at the end of the isocyanate group so as to be dispersed in water in the composition forming the primer layer (2). As the isocyanate-based compound, an isocyanate-based compound treated with a blocking agent in which a functional group located at the terminal of the isocyanate group is protected with a blocking agent is used. The blocking agent may be dissociated at 100 °C or higher. Examples of the blocking agent include phenol-based, alcohol-based, active methylene-based, acid amide-based, lactam-based, acid imide-based, imidazole-based, urea-based, oxime-based, or amine-based compounds. Specific examples of the blocking agent include phenolic compounds such as phenol, cresol, and ethylphenol; alcohol-based compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol; active methylene compounds such as dimethyl malonate and acetylacetone; mercaptan compounds such as butyl mercapdan and dodecyl mercaptan; acid amide compounds such as acetoanilide and acetate amide; lactam compounds such as caprolactam and valerolactam; acid imide compounds such as succinimide and maleic acid imide; oxime compounds such as acetaloxime, acetone oxime, and methyl ethyl ketoxime; amine compounds such as diphenylaniline, aniline and ethyleneimine; and sodium sulfite; and the like. Among them, the blocking agent may use an oxime-based compound.

The carbodiimide-based compound is a compound having two or more carbodiimide groups in the molecule. As disclosed in Japanese Patent Application Laid-Open No. Hei 10-316930 or Japanese Patent Laid-Open No. 11-140164, the carbodiimide-based compound is prepared using organic polyisocyanate, for example, organic diisocyanate as a main raw material. Examples of the organic diisocyanate include hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, xylylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,12-diisocyanate dodecane, norbornane. Diisocyanate, 2,4-bis-(8-isocyanate octyl)-1,3-dioctylcyclobutane, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, and isophorone diisocyanate and the like. The said organic diisocyanate can be used individually or in combination of 2 or more types.

The carboxyl group included in the acrylic resin has water dispersibility. The carboxyl group reacts with the methylol group to form a crosslinked structure, thereby crosslinking the inside of the acrylic resin particle. In addition, the acrylic resin having a carboxyl group is further reacted with at least one crosslinking agent selected from a melamine-based compound, an isocyanate-based compound, or a carbodiimide-based compound together with a polyalkylene oxide-based resin to adjoin the acrylic resin particles having the carboxyl group. crosslinked. The carboxyl group that does not react with the crosslinking agent may capture the hydrophilic oligomer in the optical polyester film 100 .

The molar ratio of the acrylic resin having a carboxyl group and the crosslinking agent in the primer layer 2 may be 1:0.2 to 1:2. When the molar ratio of the acrylic resin having a carboxyl group and the crosslinking agent in the primer layer 2 is within the above range, the optical polyester film 100 has excellent easy adhesion and prevents oligomer precipitation by heat treatment to improve transparency. can keep

The content of the crosslinking agent may be 30 to 50% by weight based on 100% by weight of the entire primer layer. If the content of the crosslinking agent is less than 30% by weight based on 100% by weight of the entire primer layer, the degree of crosslinking of the acrylic resin having a carboxyl group is insufficient, so that the oligomer precipitation inhibitory effect of the optical polyester film 100 is reduced. can If the content of the crosslinking agent is greater than 50% by weight based on 100% by weight of the total weight of the primer layer, the Young's modulus of the primer layer 2 is increased and a large number of unreacted crosslinking reactants are generated. Therefore, the adhesion of the primer layer 2 to the polyester base film 1 is reduced, and cracks may occur in the primer layer 2 during the biaxial stretching process of the polyester base film 1 and the appearance may be damaged. .

The primer layer 2 may include inorganic particles, organic particles, or a combination thereof. The particles improve functions such as running properties, weather resistance, and heat resistance of the optical polyester film 100 . The particles may or may not be added in a very small amount so as not to deteriorate the transparency of the optical polyester film 100 . The average particle diameter (D50) of the particles may be 1.0 μm or less, 0.5 μm or less, or 0.2 μm or less so as not to deteriorate the transparency of the optical polyester film 100 . When it is necessary to further enhance the slidability or the blocking effect, particles having an average particle diameter (D50) larger than the thickness of the primer layer 2 can be used in combination. Examples of the particles include inorganic particles such as silica, alumina, and metal oxide; or organic particles such as crosslinked polymer particles; and the like. As the particles, silica particles can be used from the viewpoint of dispersibility in the primer layer 2 or transparency of the obtained primer layer 2 .

If necessary, the primer layer 2 may use an antifoaming agent, an applicability improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, a pigment, and the like.

As the composition for forming the primer layer 2, a composition having a concentration of 0.1 to 15% by weight may be used. The composition for forming the primer layer 2 may be applied on the polyester base film 1 using a known coating method such as bar coating, gravure coating, slit die coating, comma coating, and the like. For example, as a coating method of the composition for forming the primer layer 2, a water-dispersed composition may be used, and thus a bar coating may be used to obtain an excellent appearance in a low viscosity state. The composition for forming the primer layer 2 may contain an organic solvent in the composition for the purpose of improving water dispersibility and film formability. The organic solvent may be used alone or in combination of two or more.

The primer layer (2) is positioned on the polyester base film (1) uniaxially stretched at least. The method of forming the primer layer (2) may be carried out in a step before stretching in the transverse direction after stretching in the longitudinal direction during the biaxial stretching film forming process of the polyester base film (1). For example, the primer layer 2 may be formed by applying the composition for forming the primer layer 2 to one surface of the polyester base film 1 uniaxially stretched in the longitudinal direction with a coater and drying.

[Optical polyester film (100)]

The optical polyester film 100 according to an embodiment may have a total light transmittance of 94% or more.

The optical polyester film 100 according to an embodiment may satisfy the haze change amount (ΔHAZE) before and after heat treatment according to Equation 1 below:

[Equation 1]

△HAZE ≤ 1%

In the formula,

ΔHAZE may be a difference obtained by subtracting a haze value (%) measured before heat treatment from a haze value (%) measured after heat-treating the film at 150°C and leaving it to stand for 1 hour.

[Laminated Film]

The laminated film according to another embodiment includes the above-described optical polyester film 100 , and a functional coating layer may be further disposed on the primer layer 2 of the optical polyester film 100 .

2 is a cross-sectional view of a laminated film according to an exemplary embodiment.

Referring to FIG. 2 , in the laminated film 200 , a polyester base film 11 , a primer layer 12 , and a functional coating layer 13 are arranged in this order.

The functional coating layer 13 may include a prism layer, an adhesive layer, a hard coating layer, a UV curing layer, a thermosetting layer, a printing layer, or a combination thereof.

For example, the functional coating layer 13 may be a UV curing layer. The functional coating layer 13 may be formed through a UV curing resin positioned on the primer layer 12 and a UV curing system of 200 nm to 400 m. As an example of the UV-curable resin, an acrylic resin may be used. The laminated film 200 may improve adhesion with the acrylic UV-curable resin positioned on the primer layer 12 by hydrogen bonding and covalent bonding. By adjusting the Young's modulus of the primer layer 12, the physical adhesion to the UV curing layer may be improved. In addition, in order to form the functional coating layer 13 on the polyester base film 1, precipitation of oligomers may occur from the polyester base film 1 in a high temperature environment such as a heating process, thereby reducing transparency. The optical polyester film 100 according to an embodiment can effectively suppress oligomer precipitation in the primer layer 2 by forming the primer layer 2 on the polyester base film 1 .

The adhesive force (%) at room temperature according to the following formula 2 and the adhesion force (%) after standing for 96 hours under conditions of 60 °C and 90% relative humidity can be satisfied:

[Equation 2]

Adhesion (%) = a/A x 100 ≥ 95%

In the formula,

A is the total area in contact with the primer layer and the functional coating layer,

a is the area of the portion attached between the primer layer and the functional coating layer.

Hereinafter, the configuration of the present invention and its effects will be described in more detail through Examples and Comparative Examples. However, these examples are for describing the present invention in detail, and the scope of the present invention is not limited to these examples.

[Example]

(Optical polyester film)

Example 1: Optical polyester film

(Composition for forming a primer layer)

In order to prepare a composition for forming a primer layer, the component (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C1) an isocyanate compound treated with a blocking agent were prepared as follows.

(A) 3 mol of N-methylol acrylamide, 59.5 mol of ethyl acrylate, 12.5 mol of n-butyl acrylate, 10 mol of methyl methacrylate, and 15 mol of acrylic acid were added to obtain a mixture. While maintaining the mixture at 60° C., emulsion polymerization was carried out with an aqueous solution of ammonium persulfate and an aqueous solution of meta-sodium bisulfite to obtain an emulsion polymer. The emulsion polymer was maintained at an acid value of 45 to 55 mOH/g or less and had a glass transition temperature (T _g ) of 60°C. Then, the emulsion polymer was aged at 80° C. for 2 hours, cooled to room temperature, and then adjusted to pH 9.0 using an aqueous ammonia solution to obtain an aqueous polyacrylic dispersion.

(B) polyalkylene oxide resin represented by the following formula (1)

[Formula 1]

In the formula, n is 40.

(C1) Hexamethylene diisocyanate compound blocked with sodium sulfite (H-3, Jeil Industrial Co.)

The component (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C1) an isocyanate compound treated with a blocking agent were mixed in a weight ratio of 45:9:46 to obtain a composition for forming a primer layer.

(Optical polyester film)

The polyethylene terephthalate resin pellets were dried under reduced pressure at 135° C. for 6 hours at a pressure of 1.3 hPa, and then supplied to an extruder. The polyethylene terephthalate resin pellets dried under reduced pressure in an extruder were melt-extruded into a sheet at about 280° C., and quenched and solidified on a metal roll maintained at a surface temperature of 20° C. to obtain a casting film having a thickness of 1024 μm. Then, the uniaxially oriented polyethylene terephthalate (PET) film was heated by heating the casting film at 100° C. with a heated roll group and an infrared heater, and stretching it at a 3.2 times draw ratio in the longitudinal direction using a roll having a difference in peripheral speed. got it On one side of the uniaxially oriented PET film, the composition for forming the primer layer was applied with a reverse roll coater so that the solids weight was 0.08 g/m 2 , and the uniaxially oriented PET film coated with the primer layer was clipped to the end. It was held in the air, and it was introduced into a hot air area and dried. Then, the dried uniaxially oriented PET film was stretched at a stretch ratio of 3.2 times in the transverse direction at 130° C., heat-set at 240° C., and then relieved transversely at 200° C. of 3% to have a thickness of 100 μm. An ester film was prepared. The thickness of the primer layer was 1x10 ^-3 compared to the overall thickness of the optically biaxially oriented polyester film.

Example 2: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C2) polycarbodiimide compound comprising a cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol (V- 02, NISHINBO) was mixed in a weight ratio of 45:9:46 to obtain a composition for forming a primer layer, to prepare an optically biaxially oriented polyester film in the same manner as in Example 1.

Example 3: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C3) hexamethoxymethylol melamine compound (MW22, SANWA CHEMICAL) in a weight ratio of 45:9:46 An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing.

Example 4: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C1) isocyanate compound treated with a blocking agent, and (C2) cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing the polycarbodiimide compound containing the polycarbodiimide compound in a weight ratio of 45:9:23:23.

Example 5: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C2) polycarbodiimide compound comprising a cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol, and (C3) ) An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing the hexamethoxymethylol melamine compound in a weight ratio of 45:9:23:23. .

Example 6: Optical polyester film

(A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C1) isocyanate compound treated with blocking agent, and (C3) hexamethoxymethylol melamine compound in the composition for forming a primer layer 45:9:23 An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing at a weight ratio of :23.

Comparative Example 1: Optical polyester film

An optically biaxially oriented polyester film composed of only a polyester base film without a primer layer was prepared.

Comparative Example 2: Optical polyester film

The same method as in Example 1, except that (A) polyacrylic aqueous dispersion and (C1) an isocyanate compound treated with a blocking agent were mixed in a composition for forming a primer layer in a weight ratio of 54:46 to obtain a composition for forming a primer layer to prepare an optically biaxially oriented polyester film.

Comparative Example 3: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion and (C2) a polycarbodiimide compound having a cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol are mixed in a weight ratio of 54:46 to form a primer layer Except for obtaining the composition, an optically biaxially oriented polyester film was prepared in the same manner as in Example 1.

Comparative Example 4: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion and (C3) hexamethoxymethylol melamine compound were mixed in a weight ratio of 54:46 to obtain a composition for forming a primer layer, except that a composition for forming a primer layer was obtained as in Example 1 An optically biaxially oriented polyester film was prepared by the method.

Comparative Example 5: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C1) an isocyanate compound treated with a blocking agent were mixed in a weight ratio of 51:3:46 to prepare a composition for forming a primer layer Except for that obtained, an optically biaxially oriented polyester film was prepared in the same manner as in Example 1.

Comparative Example 6: Optical polyester film

51: (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C2) polycarbodiimide compound comprising a cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol in the composition for forming a primer layer: An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing in a weight ratio of 3:46.

Comparative Example 7: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C3) hexamethoxymethylol melamine compound are mixed in a weight ratio of 51:3:46 to form a primer layer Except for obtaining an optical biaxially oriented polyester film was prepared in the same manner as in Example 1.

Comparative Example 8: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C1) an isocyanate compound treated with a blocking agent were mixed in a weight ratio of 72:9:19 to prepare a composition for forming a primer layer Except for that obtained, an optically biaxially oriented polyester film was prepared in the same manner as in Example 1.

Comparative Example 9: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C1) an isocyanate compound treated with a blocking agent were mixed in a weight ratio of 26:9:65 to prepare a composition for forming a primer layer Except for that obtained, an optically biaxially oriented polyester film was prepared in the same manner as in Example 1.

Comparative Example 10: Optical polyester film

72: (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C2) polycarbodiimide compound comprising a cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol in the composition for forming a primer layer: An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing in a weight ratio of 9:19.

Comparative Example 11: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C2) polycarbodiimide compound containing a cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol 26: An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing in a weight ratio of 9:65.

Comparative Example 12: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C3) hexamethoxymethylol melamine compound are mixed in a weight ratio of 72:9:19 to form a primer layer. Except for obtaining an optical biaxially oriented polyester film was prepared in the same manner as in Example 1.

Comparative Example 13: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, and (C3) hexamethoxymethylol melamine compound are mixed in a weight ratio of 26:9:65 to form a primer layer Except for obtaining an optical biaxially oriented polyester film was prepared in the same manner as in Example 1.

Comparative Example 14: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C1) isocyanate compound treated with a blocking agent, and (C2) cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing the polycarbodiimide compound containing the polycarbodiimide compound in a weight ratio of 72:9:9.5:9.5.

Comparative Example 15: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C1) isocyanate compound treated with a blocking agent, and (C2) cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing the polycarbodiimide compound containing the polycarbodiimide compound in a weight ratio of 26:9:32.5:32.5.

Comparative Example 16: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C2) polycarbodiimide compound comprising a cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol, and (C3) ) An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing the hexamethoxymethylol melamine compound in a weight ratio of 72:9:9.5:9.5. .

Comparative Example 17: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C2) polycarbodiimide compound comprising a cyclohexane structure having a carbodiimide equivalent weight of 420 g/mol, and (C3) ) An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing the hexamethoxymethylol melamine compound in a weight ratio of 26:9:32.5:32.5. .

Comparative Example 18: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C1) isocyanate compound treated with blocking agent, and (C3) hexamethoxymethylol melamine compound 72:9:9.5 An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing at a weight ratio of :9.5.

Comparative Example 19: Optical polyester film

In the composition for forming a primer layer, (A) polyacrylic aqueous dispersion, (B) polyalkylene oxide resin, (C1) isocyanate compound treated with blocking agent, and (C3) hexamethoxymethylol melamine compound 26:9:32.5 An optically biaxially oriented polyester film was prepared in the same manner as in Example 1, except that a composition for forming a primer layer was obtained by mixing at a weight ratio of :32.5.

Evaluation Example 1: Physical property evaluation

The physical properties of each of the optically biaxially oriented polyester films prepared in Examples 1 to 6 and Comparative Examples 1 to 19 were evaluated as follows. The results are shown in Table 1 below.

(1) Young's Modulus

For each optical biaxially oriented polyester film, the Young's Modulus was measured using the nanoindentation method according to ISO 14577 standard.

Using Helmut's FISCHERSCOPE HM2000, the tip of the nanoindenter was pressed for 5 seconds from the surface of the primer layer of the film to a depth of 50 nm in the press-in mode at 25 ° C., and then lifted for 5 seconds to measure the Young's modulus. At this time, the indentation rod force was 0.4 mN and the indentation speed was maintained at 10 nm/s for 5 seconds.

(2) Water contact angle

1 μL of water was dropped on the primer layer surface of each optical biaxially oriented polyester film, and the contact angle was measured after 3 seconds. The water contact angle was measured using a contact angle meter (Kyowa Interface Science, DropMaster 100) and a solid-liquid interface analyzer (and DropMaster 300, manufactured by Interface Science, Inc.) according to the θ/2 method.

(3) Haze change before and after heat treatment (ΔHAZE)

For each optical biaxially oriented polyester film, a haze value was measured using a NIPPON DENSHOKU company, a HAZE measuring device. Thereafter, the film was put into an electric dryer, heat treated at 150° C., left to stand for 1 hour, and then the haze value was measured with the haze meter. At this time, the difference by subtracting the haze value (%) measured before the heat treatment from the haze value (%) measured after heat treatment at 150° C.

(4) Adhesive strength after testing for adhesion and moisture resistance at room temperature

An acrylic UV curing resin (UV-7640B, made in Japan) was applied to the surface of the primer layer of each optically biaxially oriented polyester film using a wire bar. For the film, a cut line was made by placing a 1 mm x 1 mm square frame in a 10 x 10 mm ² matrix. A cellophane tape (NICHIBAN, No. 405, width: 24 mm) was attached to the film on which the cut line was made (that is, the total area of the film is 10 x 10 mm ² ), and the attached cellophane tape was rubbed using velvet. Then, the cellophane tape was peeled off in a vertical direction. By observing the area of the part attached between the primer layer and the functional coating layer in the film, the adhesion (%) at room temperature was obtained according to Equation 2. In the same manner, the adhesive force (%) after standing for 96 hours under conditions of 60°C and 90% relative humidity was also obtained.

[Equation 2]

Adhesion (%) = a/A x 100 ≥ 95%

A is the total area in contact with the primer layer and the functional coating layer,

a is the area of the portion attached between the primer layer and the functional coating layer.

(5) refractive index of the primer layer

Samples were prepared by cutting into a size of 50 mmХ50 mm at an arbitrary analysis point of the primer layer of each optically biaxially oriented polyester film. Using an ellipsometer-M-2000 D for an arbitrary part on the sample, set the corner between the normal of the film plane and the incident light to be 60° and the reflected intensity of the measured reflected light to be 0.20 or more, and set it to 10 in the standard measurement mode. It was measured twice to measure the refractive index of the primer layer.

(6) total light transmittance of the film

For each optical biaxially oriented polyester film, the total light transmittance was measured using NIPPON DENSHOKU, HAZE measuring device according to JIS K 7361-1:1997.

division Young's modulus
(MPa) water contact angle
(°) △HAZE
(%) Adhesion at room temperature
(%) moisture resistance
test
after
Adhesion (%) primer layer
refractive index of total light transmittance
(%) Example 1 824 57 0.4 99 100 1.502 94.5 Example 2 752 62 0.5 95 97 1.502 94.6 Example 3 963 65 0.2 99 97 1.501 94.4 Example 4 765 60 0.3 100 100 1.504 94.7 Example 5 811 65 0.4 99 95 1.508 94.5 Example 6 898 63 0.2 99 95 1.508 94.7 Comparative Example 1 6099 72 8.9 0 0 1.642 88.2 Comparative Example 2 1128 68 0.2 66 50 1.501 94.2 Comparative Example 3 1080 68 0.3 70 65 1.503 94.9 Comparative Example 4 1170 69 0.3 50 40 1.503 94.5 Comparative Example 5 1092 65 0.3 65 60 1.502 94.2 Comparative Example 6 1052 64 0.5 70 60 1.503 94.3 Comparative Example 7 1154 66 0.4 60 60 1.503 94.3 Comparative Example 8 1291 65 0.2 70 60 1.502 94.5 Comparative Example 9 1105 56 2.0 68 60 1.521 92.2 Comparative Example 10 1266 61 0.3 70 60 1.502 94.5 Comparative Example 11 1156 63 2.2 70 65 1.520 92.6 Comparative Example 12 1341 65 0.2 65 40 1.505 94.2 Comparative Example 13 1203 67 1.8 60 40 1.522 92.3 Comparative Example 14 1206 62 0.1 55 55 1.503 94.2 Comparative Example 15 1129 61 1.6 60 50 1.522 92.6 Comparative Example 16 1289 61 0.2 65 60 1.502 94.6 Comparative Example 17 1192 65 1.9 55 45 1.519 93.0 Comparative Example 18 1287 64 0.2 50 45 1.503 94.6 Comparative Example 19 1269 64 1.7 40 40 1.526 92.1

Referring to Table 1, the optical polyester film prepared in Examples 1 to 6 has a Young's modulus of 963 MPa or less at 25° C. and a water contact angle with respect to the primer layer surface is 57° to 65°, The refractive index of the primer layer was 1.50 to 1.51. The optical polyester film prepared by Examples 1 to 6 had a haze change amount (ΔHAZE) of 0.5% or less before and after heat treatment as compared to the optical polyester film prepared by Comparative Examples 1 to 19, and at room temperature After the adhesion and moisture resistance tests, both the adhesion force was 95% or more, and the total light transmittance was 94.4% or more. Among them, the optical polyester film prepared in Example 4 (a cyclohexane structure having an isocyanate compound treated with a (C1) blocking agent in a composition for forming a primer layer, and (C2) a carbodiimide equivalent weight of 420 g/mol) polycarbodiimide compound) was 100% in both adhesion and moisture resistance tests at room temperature, and the total light transmittance was 94.7%, which was very good.

From this, it can be confirmed that the optical polyester films prepared in Examples 1 to 6 maintain transparency by preventing oligomer precipitation by heat treatment while having excellent easily adhesive properties.

1, 11: polyester base film,
2, 12: primer layer,
13: functional coating layer, 100: optical polyester film
200: laminated film

Claims (13)

An optical polyester film comprising:
polyester base film; and
a primer layer disposed on at least one surface of the base film; and
The primer layer has a thickness of 4x10 ^-4 to 2x10 ^-3 compared to the overall thickness of the optical polyester film,
An optical polyester film having a Young's modulus of 1000 MPa or less at 25 °C. According to claim 1,
A water contact angle of 55° to 70° with respect to the surface of the primer layer, an optical polyester film. According to claim 1,
The refractive index of the primer layer is 1.50 to 1.51, an optical polyester film. According to claim 1,
The primer layer includes an acrylic resin having a carboxyl group, a polyalkylene oxide-based resin, and a crosslinking agent,
The content of the acrylic resin and polyalkylene oxide-based resin having a carboxy group is 40 to 70% by weight based on 100% by weight of the entire primer layer,
The content of the crosslinking agent is 30 to 50% by weight based on 100% by weight of the entire primer layer, an optical polyester film. 5. The method of claim 4,
The weight ratio of the acrylic resin having the carboxyl group and the polyalkylene oxide-based resin is 3:1 to 7:1, an optical polyester film. 5. The method of claim 4,
The optical polyester film, wherein the crosslinking agent comprises at least one selected from a melamine-based compound, an isocyanate-based compound, or a carbodiimide-based compound. According to claim 1,
The primer layer is an optical polyester film comprising inorganic particles, organic particles, or a combination thereof. According to claim 1,
A polyester film for optics having a total light transmittance of 94% or more. According to claim 1,
An optical polyester film that satisfies the haze change amount (ΔHAZE) before and after heat treatment according to Formula 1 below:
[Equation 1]
△HAZE ≤ 1%
In the formula,
ΔHAZE is the difference by subtracting the haze value (%) measured before heat treatment from the haze value (%) measured after heat-treating the film at 150°C and leaving it for 1 hour. According to claim 1,
The polyester base film is a biaxially stretched polyester base film, an optical polyester film. A laminated film comprising the optical polyester film according to any one of claims 1 to 10, wherein a functional coating layer is further disposed on the primer layer of the optical polyester film. 12. The method of claim 11,
Wherein the functional coating layer comprises a prism layer, an adhesive layer, a hard coating layer, a UV curing layer, a thermosetting layer, a printing layer, or a combination thereof. According to claim 1,
An optical polyester film that satisfies the adhesion (%) at room temperature according to the following formula 2 and the adhesion (%) after being left for 96 hours under conditions of 60°C and 90% relative humidity:
[Equation 2]
Adhesion (%) = a/A x 100 ≥ 95%
In the formula,
A is the total area in contact with the primer layer and the functional coating layer,
a is the area of the portion attached between the primer layer and the functional coating layer.

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