KR20080097606A - Biaxially oriented multi-functional polyester laminated film for optical use - Google Patents

Abstract

A biaxially oriented polyester films for the optics is provided to ensure excellent adhesive property to a base after coating a primer layer of the biaxially oriented polyester film and have excellent adhesive force and optical characteristic in a post-manufacturing process. A biaxially oriented polyester films for the optics forms a primer layer as a polymer adhesive bilayer coated on at least one side of a biaxially oriented polyester film base with the thickness of 50~300micrometer. The coating solution forming the polymer primer layer comprises a copolymerized polyester-based resin, polyacryl-based resin and polyurethane-based resin containing a branched monomer as a compositional component, and silica particles or alumina-silica complex oxide particles with an average particle diameter of 50~300nm. The weight ratio of a copolymerized polyester-based resin, polyacryl-based resin and polyurethane-based resin is 1.0:1.0:1.0 ~ 5.0:5.0:5.0. The content of silica particle or alumina-silica complex oxide particle is 0.01~60 weight% of whole coating solution.

Description

Biaxially Oriented Polyester Film for Optics {BIAXIALLY ORIENTED MULTI-FUNCTIONAL POLYESTER LAMINATED FILM FOR OPTICAL USE}

1 is a cross-sectional view of an optical biaxially oriented polyester film according to the present invention.

The present invention relates to an optical biaxially oriented polyester film having excellent adhesiveness and transparency, and more particularly, a coating liquid used in a conventional primer layer has insufficient adhesive strength with a substrate or with a primer layer in a post-processing process. In order to solve the problem, by newly preparing a coating liquid (hereinafter also referred to as 'crude liquid') applied to the primer layer, after coating with the primer layer of the biaxially oriented polyester film, the adhesive force and The present invention relates to an optical biaxially oriented polyester film having excellent optical properties.

In general, biaxially stretched polyester films have excellent dimensional stability, thickness uniformity and optical transparency, so that they are widely used not only for display devices but also for various industrial materials.

When using such a biaxially stretched polyester film for optics, a primer layer generally forms a primer layer with co-polyester-type resin excellent in adhesiveness with a polyester film. However, when the copolyester-based resin is used alone, the adhesiveness with the polyester base film is sufficient, but when used after various post-processing treatments such as a prism lens, an antireflection layer, or a hard coating layer, the copolyester-based resin may be used. Insufficient In order to compensate for this, it is necessary to use an acrylic resin having easy adhesiveness or a polyurethane resin which is used in many fields requiring adhesiveness because it has excellent flexibility, rebound elasticity, abrasion resistance, and strong adhesiveness. A method of improving adhesion by coating a primer layer has been studied.

However, by forming a primer layer composed of a polyacrylic resin and a polyurethane resin, the adhesive strength with the outer layer such as the hard coat layer is improved, but the adhesive force with the polyester film as the base material is not sufficient, resulting in sufficient There was a problem that adhesiveness could not be obtained.

On the other hand, biaxially stretched polyester film used for optics is required to have excellent adhesive properties for prism lens processing, hard coat processing, AR processing, but it is difficult to develop because the resin form used by each post-processing company is different. In addition, the biaxially stretched polyester film used for such optics is required to have very few foreign matters included in the film which causes scratch resistance and optical defects, and such optical films require excellent transparency. do.

The present invention has been made to solve the above problems and to meet the conventional requirements, the object of the present invention is the primer layer used in the biaxially stretched polyester film, as well as sufficient easy adhesion with the substrate, the post-processing process It is to provide a biaxially oriented polyester film for optics which is excellent in properties such as easy adhesiveness and excellent optical properties.

In addition, the object of the present invention is to improve the product yield, and also the high rate of warfare, since it has excellent post-processing ability, such as conveyability of the film, in the heat treatment process during post-processing such as prism lens processing, hard coat processing, and AR processing. The haze value is to provide an optical biaxially oriented polyester film that can be used throughout various optical members because of its small properties.

The above and other objects and advantages of the present invention will become more apparent from the following description of the preferred embodiments with reference to the accompanying drawings.

Optical biaxially oriented polyester film according to the present invention for achieving the above object is a biaxially oriented polyester film substrate having a thickness of 50 ~ 300㎛ and a polymer easily adhesive layer applied to at least one side of the substrate, forming a primer layer An optical biaxially oriented polyester film, wherein the coating liquid for forming the polymer primer layer comprises co-polyester resins, polyacrylic resins, and polyurethane resins having branched monomers as components, and silica particles having an average particle diameter of 50 to 300 nm, or Including alumina-silica composite oxide particles, the weight ratio of the copolyester-based resin, the polyacrylic resin and the polyurethane-based resin is 1.0: 1.0: 1.0 ~ 5.0: 5.0: 5.0, the silica particles or alumina-silica The content of the composite oxide particles is characterized by being 0.01 to 60% by weight in the total coating liquid.

Preferably, the primer layer is characterized in that applied after uniaxial stretching of the biaxially oriented polyester film.

More preferably, the thickness of the primer layer is characterized in that 0.05 ~ 3.00㎛.

More preferably, the surface of the base film on which the primer layer is formed is characterized in that the total light transmittance is 91% or more, the haze value is 0.4 ~ 1.0%.

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

The biaxially oriented polyester film for optics which concerns on this invention relates to the biaxially oriented polyester film for optics excellent in the adhesiveness in a post-processing process. In the manufacturing process of the biaxially oriented polyester film, a co-polyester-based resin, a polyacrylic-based resin and a polyurethane-based resin is mixed to form a primer layer, and the adhesiveness of the primer layer performed during the manufacturing process is a poly After the coating process in the ester film and the post-processing, it is characterized in that it is a biaxially oriented polyester film excellent in adhesion. In other words, the biaxially oriented polyester laminated film according to the present invention, unlike the conventional biaxially oriented polyester laminated film, the base film has a function by providing not only easy adhesion with the substrate, but also excellent adhesion in the post-processing process. It is characterized in that it is a biaxially oriented polyester film which retains its optical properties or exhibits more excellent properties.

It is preferable that the copolyester type resin which forms the biaxially-oriented polyester film for optics which concerns on this invention contains a dicarboxylic acid component and the branched glycol component as a component. Examples of the branched glycol component include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2, 2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2- Di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, 2,2-di-n-hexyl-1,3-propanediol, and the like. have. It is preferable to contain the branched glycol component in the total glycol component in a ratio of 10 mol% or more, particularly preferably in a ratio of 20 mol% or more. This is because the adhesion with the biaxially oriented polyester film becomes insufficient at less than 10 mol%. In addition, the branched glycol component is preferably contained at a rate of 80 mol% or less in the total glycol component. It is because the melting point of a polyester film will become low when the glycol component branched in the whole glycol component exceeds 80 mol%.

As glycol components other than the said compound, ethylene glycol is the most preferable. As small amount, diethylene glycol, propylene glycol, butanediol, hexanediol or 1,4-cyclohexanedimethanol may be used.

As the dicarboxylic acid component contained in the copolyester-based resin as a constituent, terephthalic acid and isophthalic acid are most preferred. If small amount, other dicarboxylic acid, especially diphenylcarboxylic acid and aromatic dicarboxylic acid of 2, 6- naphthalenedicarboxylic acid, may be added and copolymerized.

In addition to the dicarboxylic acid component, in order to impart water dispersibility, it is preferable to use 5-sulfoisophthalic acid in the range of 1 to 10 mol%, for example, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfo Naphthalene isophthalic acid-2,7-dicarboxylic acid, 5- (4-sulfophenoxy) isophthalic acid, its salts, etc. are mentioned.

As a polyacrylic resin used for the primer layer of the biaxially-oriented polyester film for optics which concerns on this invention, 3 or more in 1 molecule, More preferably, 4 or more, More preferably, it is 5 or more (meth) acryl. A main component is a mixture consisting of at least one of monomers and prepolymers having a monooxy group and at least one of monomers having one or two ethylenically unsaturated double bonds in one molecule. More specific examples include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth Acrylate, dipentaerythritol hexa (meth) acrylate, trimetholpropane tri (meth) acrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane Prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, etc. can be used. These monomers and the prepolymer can be used 1 type or in mixture of 2 or more types. Especially the polyfunctional acrylate compound which has one or more hydroxyl groups among these is especially preferable because an adhesive of a base film can be improved when an epoxy type hardening | curing agent is used together.

The polyurethane-based resin used in the primer layer of the biaxially oriented polyester film for optics according to the present invention may be a solvent type, a solventless type or an aqueous various coating agent. For example, as resin containing a block type isocyanate group, the heat-reactive type water-soluble urethane resin which blocked the terminal isocyanate group by the hydrophilic group is mentioned. Examples of the blocking agent for the isocyanate group include phenols, lactams, oximes, alcohols and active methylene compounds containing sulfonic acid groups and bisulfites.

The surfactant forming the primer layer of the optical biaxially oriented polyester film according to the present invention can be used in a water-soluble coating liquid, and a known anionic or nonionic surfactant is used to increase the wettability of the base film and to uniformly apply the coating liquid. It is preferable to apply | coat to a base film using a required amount.

The primer layer of the biaxially oriented polyester film for optics according to the present invention is preferably formed by coating with a resin binder or the like after uniaxial stretching of the biaxially oriented polyester film. At this time, the thickness of the resin-coated layer is preferably 0.01 to 5.00 µm, more preferably 0.05 to 3.00 µm. When the thickness of the coating is thinner than 0.05 μm, the transparency becomes good but the adhesion decreases. When the coating thickness is larger than 3 μm, the adhesive property is excellent, but the transparency and the coating property are deteriorated, which is not preferable.

In addition, in the present invention, an additive may be used in the coating liquid to improve coating properties and functionality, and organic additives, inorganic particles, and antifoaming agents may be used as such additives. According to the biaxially oriented polyester film for optics according to the present invention, the water-soluble polymer primer layer may include inorganic particles having a relatively small difference in refractive index between the resins, thereby ensuring runability, and the average particle diameter of the inorganic particles used at this time is 30. If the particle size is less than ㎚, the microparticles not only help the running and scratch resistance of the sheet or film, but also do not affect the effect of the fine particles, and when the average particle diameter of the microparticles exceeds 500nm, there is a problem of haze. Is generated. The size of the inorganic particles according to the present invention has a particle size in the range of 30 ~ 500nm, more preferably 50 ~ 300nm, for example, it is preferable to use silica particles.

In the present invention, the surface of the base film on which the primer layer is formed is characterized in that the adhesive strength of 95% or more, total light transmittance of 91% or more, and haze of 0.4% to 1.0%.

Hereinafter, the present invention will be described in more detail with reference to various examples and comparative examples.

Example 1

The coating liquid for forming the primer layer in Example 1 is as follows.

Polyester resin is 75% water and 25% by weight polyester resin aqueous dispersion 2.0% by weight, polyacrylic resin is 58% by weight water and polyacrylic resin 42% by weight poly 1.0% by weight of acrylic resin water dispersion, 2.0% by weight of polyurethane resin water dispersion containing 77.5% by weight of polyurethane resin and 22.5% by weight of polyurethane resin, epoxy curing agent is 30% by weight of water and epoxy curing agent Is 0.7% by weight of the aqueous dispersion of hardener containing 70% by weight and 93.23% by weight of water, and the anionic surfactant is anionic surfactant aqueous dispersion 1.0 containing 90% by weight of water and 10% by weight of anionic surfactant. The weight percent and colloidal silica particles were added as 30% by weight of water and 0.07% by weight of an aqueous dispersion of colloidal silica particles containing 70% by weight of colloidal silica particles. It was.

In this embodiment, the polyethylene terephthalate resin pellets were dried under reduced pressure (1.3 hPa) at 135 ° C. for 6 hours, fed to an extruder, and then melt-extruded into a sheet at about 280 ° C. and maintained at a surface temperature of 20 ° C. It was quenched on a roll to obtain a casting film having a thickness of 1024 µm. Next, the cast film is heated to a heated roll group and an infrared heater at 100 ° C., and then stretched to a roll group having a circumferential speed with a draw ratio of 3.2 times in the longitudinal direction to obtain a uniaxially oriented PET film. Used. The coating liquid which forms the said primer layer was apply | coated to one side of the uniaxially-oriented PET film by the reverse roll method, and it dried. The coating amount (solid content weight) at this time was 0.08g / m <2>. Then, the film was gripped at the end with a clip, introduced into the hot air region, and dried. Thereafter, the film was stretched at a stretch ratio of 3.2 times in the transverse direction at 130 ° C, heat-set at 240 ° C, and laterally relaxed at 3 ° C at 200 ° C. Thus, a biaxially oriented polyester film for optics having a thickness of 100 µm was obtained.

Example 2

In the film formation of the biaxially oriented polyester film of Example 1, after the coating solution was prepared in the same manner as in Example 1 except that the thickness of the cast film was 1280 μm and the film thickness was 125 μm, the optical biaxially An oriented polyester film was obtained.

Example 3

In the film formation of the biaxially oriented polyester film of Example 1, after the coating solution was prepared in the same manner as in Example 1 except that the thickness of the cast film was 1925 µm and the film thickness was 188 µm, the optical biaxially An oriented polyester film was obtained.

Example 4

The coating liquid was 2.0 weight% of 25 weight% of aqueous dispersion of polyester resin, 2.0 weight% of 42 weight% of polyacrylic resin, 1.0 weight% of 22.5 weight% of polyurethane resin, and 70 weight% of epoxy curing agent. 0.7% by weight of the dispersion and 93.23% by weight of water were mixed, and 1.0% by weight of the 10% by weight aqueous dispersion for the anionic surfactant and 0.07% by weight of the 70% by weight aqueous dispersion of the colloidal silica particles were used as the coating liquid.

A biaxially oriented polyester film for optics was obtained in the same manner as in Example 1 except that the thickness of the biaxially oriented polyester film was 100 μm.

Example 5

In the film formation of the biaxially oriented polyester film of Example 1, after the coating solution was prepared in the same manner as in Example 4 except that the thickness of the cast film was 1280 μm and the film thickness was 125 μm, the optical biaxially An oriented polyester film was obtained.

Example 6

In the film formation of the biaxially oriented polyester film of Example 1, after the coating solution was prepared in the same manner as in Example 4 except that the thickness of the cast film was 1925 µm and the film thickness was 188 µm, the optical biaxially An oriented polyester film was obtained.

Example 7

The coating liquid was 25% by weight of polyester resin 1.0% by weight of aqueous dispersion, 42% by weight of polyacrylic resin, 2.0% by weight of aqueous dispersion, and 22.5% by weight of polyurethane resin. After preparing the coating liquid in the same manner as in Example 1, except that 2.0 wt% of the aqueous dispersion was added, the optical biaxially oriented polyester having a film thickness of 100 μm after film formation of the biaxially oriented polyester film of Example 2 A film was obtained.

Example 8

In the film formation of the biaxially oriented polyester film of Example 1, after the coating solution was prepared in the same manner as in Example 7, except that the thickness of the casting film was 1280 μm and the film thickness was 125 μm, the optical biaxially An oriented polyester film was obtained.

Example 9

In the film formation of the biaxially oriented polyester film of Example 1, after the coating solution was prepared in the same manner as in Example 7, except that the thickness of the cast film was 1925 µm and the film thickness was 188 µm, the optical biaxially An oriented polyester film was obtained.

Comparative Example 1

The coating liquid was mixed 5.0 wt% of the 42% by weight aqueous dispersion of polyacrylic resin, 0.7 wt% of the 70 wt% aqueous dispersion, and 93.23 wt% of the water-based epoxy curing agent, and 10 wt% aqueous dispersion of the anionic surfactant. 1.0 wt% and colloidal silica particles were added with 0.07 wt% of a 70 wt% aqueous dispersion to obtain a coating liquid.

A biaxially oriented polyester film for optics was obtained in the same manner as in Example 1 except that the thickness of the biaxially oriented polyester film was 188 μm.

Comparative Example 2

The coating liquid was prepared by preparing a coating liquid in the same manner as in Comparative Example 1 except that the coating liquid was prepared by using a polyester resin 25 wt% aqueous dispersion as 5.0 wt%, and then the film was formed in the film formation of the biaxially oriented polyester film of Example 1 The biaxially oriented polyester film for optics whose thickness of a post film is 188 micrometers was obtained.

Comparative Example 3

After the coating liquid was prepared by preparing the coating liquid in the same manner as in Comparative Example 1, except that the coating liquid was prepared by using a polyurethane resin 22.5 wt% aqueous dispersion as 5.0 wt%, and then forming a film of the biaxially oriented polyester film of Example 1 The biaxially oriented polyester film for optics whose thickness of film is 188 micrometers was obtained.

Experimental Example 1

Coating appearance of the films prepared in Examples 1 to 9 and Comparative Examples 1 to 3 were measured. Using fluorescent light and three wavelengths of light, the coating state of the prepared coating solution was measured by visually dividing the phase into upper, middle and lower parts.

Experimental Example 2

The adhesion between the substrate and the primer layer of the films prepared in Examples 1 to 9 and Comparative Examples 1 to 3 was measured. An acrylate adhesive test sample is applied to the surface to which the primer layer is attached using a # 4 wire bar, and dried at 150 ° C. for 30 seconds in a drying oven. Then, a cutting line is made on the film coated with the primer layer by a cutter to place 2 mm × 2 mm squares in a 10 × 10 matrix. The cut lines are made deep enough to reach the substrate film through the adhesive layer. A cellophane tape (No. 405, made by NICHIBAN; width: 24 mm) is attached to the film with a cutting line, and the tape is rubbed with an eraser to strongly adhere to the film, and then the tape is removed vertically. The area of the primer layer remaining in the adhesive layer was visually observed, and the adhesive force was calculated by the following equation.

The symbol "o" in Table 1 represents 90% or more, and "x" represents less than 90%.

Experimental Example 3

The optical properties of the coating solution used in the films prepared in Examples 1 to 9 and Comparative Examples 1 to 3 were measured. Optical properties were measured by dividing the combat rate and Hz using methods commonly used in the art.

The results according to Experimental Examples 1 to 3 are shown in Table 1 below.

TABLE 1

The mixing ratio in Table 1 shows the mixing ratio of the polyacrylic resin, the polyester resin and the polyurethane resin.

As can be seen in Table 1, the examples according to the present invention are excellent in the appearance, such as the coating appearance, sufficient adhesiveness with the base material, compared to the comparative examples, excellent in the properties such as easy adhesion required in the post-processing process Can be.

According to the biaxially oriented polyester film for optics according to the present invention, the primer layer used in the biaxially stretched polyester film is excellent in not only sufficient adhesiveness with the substrate but also properties such as easy adhesiveness required in the post-processing process, The optical characteristic is excellent effect.

In addition, the present invention can increase the product yield because it is excellent in the post-processing ability such as the conveyability of the film in the heat treatment step during post-processing such as prism lens processing, hard coat processing, AR processing and the like.

In addition, the present invention can be used throughout the various optical members because of its high combat rate and low haze value. In particular, the optical film includes a prism sheet base film, a backlight base film, and a hard coat, which are used in LCDs. There is an effect such as useful as a protective film or the like in the base film for processing and AR film and CRT.

Claims (4)

As a biaxially oriented polyester film base material having a thickness of 50 to 300 μm and a polymer easily adhesive layer applied to at least one side of the base material, as a biaxially oriented polyester film for optics in which a primer layer is formed, The coating liquid for forming the polymer primer layer may include copolyester-based resins, polyacrylic resins, and polyurethane-based resins having branched monomers as components, and silica particles or alumina-silica composite oxide particles having an average particle diameter of 50 to 300 nm. , The weight ratio of the copolymer polyester resin, the polyacrylic resin and the polyurethane resin is 1.0: 1.0: 1.0 ~ 5.0: 5.0: 5.0, the content of the silica particles or alumina-silica composite oxide particles in the total coating liquid It is 0.01 to 60 weight%, The biaxially-oriented polyester film for optics. The method of claim 1, The primer layer is applied after uniaxial stretching of the biaxially oriented polyester film, biaxially oriented polyester film for optics. The method of claim 1, The thickness of the primer layer is 0.05 ~ 3.00㎛, Biaxially oriented polyester film for optics. The method according to any one of claims 1 to 3, The biaxially oriented polyester film for optics, wherein the surface of the base film on which the primer layer is formed has a total light transmittance of 91% or more and a haze value of 0.4 to 1.0%.

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