KR20080064278A - Biaxially oriented polyester laminated film for optical use - Google Patents

Abstract

A biaxially-oriented polyester film is provided to allow a primer layer of the biaxially-oriented polyester film to be easily bonded to or released from a base layer. A biaxially-oriented polyester film has a thickness of 50 to 300mum, and a polymer primer layer is formed on at least one surface of the biaxially-oriented polyester film. The polymer primer layer includes co-polymeric polyester resin, polyacryl-based resin and a silica grain having an average grain size of 50 to 300nm or an alumina-silica composite oxide grain. A weight ratio of the co-polymeric polyester resin to the polyacryl-based resin is 90:10 to 10:90. The content of the silica grain or the alumina-silica composite oxide grain is 0.01 to 60 weight percent.

Description

Biaxially Oriented Polyester Film for Optics {BIAXIALLY ORIENTED 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 preparing a new crude liquid to be applied to the primer layer, after coating with the primer layer of the biaxially oriented polyester film, biaxially oriented polyester for optics excellent in adhesion and optical properties even in the adhesion and post-processing process with the substrate It is about a film.

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 adhesion 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 is used. Insufficient In order to compensate for this, a method of improving the adhesive strength by coating a primer layer using an acrylic or urethane resin having easy adhesiveness when preparing polyester is being studied.

However, by forming a primer layer made of 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 adhesiveness with the outer layer. There was a problem not to lose.

On the other hand, biaxially stretched polyester films used for optics are required to have excellent adhesion for post-processing prism lens processing, hard coat processing, and AR processing, and are included in films that cause scratch resistance and optical defects. It is desired that very few foreign matters are required, and such transparency for optical films is also required.

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.

The biaxially oriented polyester film for optics according to the present invention for achieving the above object is based on a biaxially oriented polyester film having a thickness of 50 to 300 μm, and a primer layer is formed on at least one side of the base as a polymer adhesive layer. An optical film, wherein the polymer primer layer comprises a copolymerized polyester resin, a polyacrylic resin, and silica particles or an alumina-silica composite oxide particle having an average particle diameter of 50 to 300 nm, wherein the copolymer primer comprises The weight ratio of the ester resin and the polyacrylic resin is 90:10 to 10:90, the content of the silica particles or alumina-silica composite oxide particles is 0.01 to 60% by weight, and the surface of the base film on which the primer layer is formed It is characterized by the total light transmittance of 92% or more and the haze value of 0.4 to 0.8%.

Preferably, the primer layer is characterized in that it is 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㎛.

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 according to the present invention relates to a biaxially oriented polyester film having excellent adhesion in a post-processing process. It characterized in that the primer layer is formed by mixing the copolyester-based resin and the polyacrylic resin in the manufacturing process of the biaxially oriented polyester film, and the easy-adhesiveness of the primer layer carried out during the manufacturing process and the post-processing polyester film It is a biaxially-oriented polyester film which is excellent also in easily adhesive property, even after the coating process in. 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.

The copolyester-based resin forming the biaxially oriented polyester film according to the present invention preferably comprises a dicarboxylic acid component and a branched glycol component as constituents. Branched glycol components include, for example, 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. . It is preferable to contain the branched glycol component at a rate of 10 mol% or more in the total glycol component, particularly preferably at least 20 mol%. Moreover, it is preferable to contain the branched glycol component in a ratio of 80 mol% or less in the total glycol component. If it is less than 10 mol%, there exists a tendency for adhesiveness with a biaxially-oriented polyester film to become inadequate.

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-type resin used for the primer layer of the easily bonding film for optics of this invention, 3 or more in 1 molecule, More preferably, 4 or more, More preferably, 5 or more (meth) acryloyloxy groups The main component is a mixture consisting of at least one of monomers and prepolymers having one or more 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 and the like 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 surfactant forming the primer layer of the biaxially oriented polyester film according to the present invention can be used in a water-soluble coating liquid, and the required amount of 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.

In the present invention, the primer layer is formed by applying with a resin binder or the like on the film after the primary stretching. 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. If the thickness of the coating is thinner than 0.05㎛ the transparency is good but the adhesion is poor, if the thickness is more than 3㎛ excellent adhesion properties, but the transparency and coating properties are not preferred because it is poor. Also preferably, the primer layer is applied after uniaxial stretching of the biaxially oriented polyester film.

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 present invention, the water-soluble polymer primer layer may include inorganic particles having a relatively small difference in refractive index with the resin, thereby ensuring runability, and when the average particle diameter of the inorganic particles used is less than 30 nm, the fine particles may be Not only do not help the running and scratch resistance in the film, but also does not give the effect of the fine particles, and when the average particle diameter of the fine particles exceeds 500nm causes a problem that haze. 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 90% or more, total light transmittance of 92% or more, and haze of 0.4% to 0.8%.

 EXAMPLE

The manufacturing method of the biaxially-oriented polyester laminated | multilayer film which concerns on this invention is demonstrated. First, a polyester laminated film (hereinafter abbreviated as 'PET') will be described as an example of the base film, but the present invention is not limited thereto. Specific examples thereof may be a film made of polyester, polyolefin, polyamide, polyphenylene sulfide, acetate, polycarbonate, acrylic resin, or the like. Among them, a film made of a thermoplastic resin excellent in transparency, mechanical strength, dimensional stability and the like is particularly preferable.

After drying the PET pallet containing 0.2 wt% of silica particles having an average particle diameter of 0.3 μm in vacuum at about 180 ° C. for about 2 hours to sufficiently remove moisture, the PET pallet was fed to an extruder and melt-extruded at a temperature of 230 to 300 ° C., followed by T It is molded into a sheet shape from the female mold. The sheet-like article thus obtained is cooled and fixed on a mirrored cooling drum to obtain an unstretched sheet. At this time, it is preferable to use the electrostatic application method for the purpose of improving the adhesiveness with a cast drum. Then, 2 to 5 times extending | stretching is performed in the longitudinal direction of the roll which heated the obtained unstretched film at 70-120 degreeC. Longitudinal stretching is preferably a condition that lowers the crystal orientation and promotes thermal crystallization, and a method of stretching while heating with a radiant heater at the time of stretching is preferable.

Subsequently, the weight ratio of the copolyester resin (A) and the polyacrylic resin (B) is 90:10 to 10:90 on the surface or both surfaces of the film uniaxially stretched in this manner, and the average particle diameter is 50 to 300 nm. The content of phosphorus silica particles is 0.01 to 60% by weight, and it can be used as a water-soluble coating liquid as a surfactant, and it is necessary to use a known amount of anionic or nonionic surfactant in order to increase the wettability of the base film and to uniformly apply the coating liquid. It is preferable to apply | coat to a film.

Thereafter, both ends of the film are gripped with clips, leading to the tenter. After preheating in the tenter, the film is stretched about 2 to 5 times in the width direction. Heat-treatment (approximately, glass transition temperature to melting point temperature of resin, 200 to 245 in case of PET) to complete the crystallization of the base film and curing of the coating film while further performing 3-10% of the lamination film stretched in the width direction. ℃). As the heat required for thermosetting used in the present invention, the air or inert gas, which has been heated to a temperature of at least 140 ° C. using a steam heater, an electric heater, an infrared heater or a far infrared heater, or the like, is sprayed onto the substrate and the coating film using a slit nozzle. The heat applied by contacting is enumerated, and heat by air heated to 200 ° C or higher is preferred, and heat by nitrogen heated to 200 ° C or higher is more preferable since the curing rate is high.

 Example 1

The coating liquid for forming the primer layer in Example 1 is 12.0% by weight of a polyester resin 25% aqueous dispersion, 4.8% by weight of a 42% polyacrylic resin, an epoxy-based curing agent 0.7% by weight of a resin having a solid content of 70% by weight and water 77.43 It was prepared by mixing the weight%, adding 5.0% by weight of 10% aqueous solution of anionic surfactant and 0.07% by weight of 70% aqueous colloidal silica particles.

In the present 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 melt-extruded into a sheet at about 280 ° C. and maintained at a surface temperature of 20 ° C. It was quenched on a metal 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, biaxially oriented for optical after preparing a crude liquid in the same manner as in Example 1, except that the thickness of the casting film was 1280 µm and the film thickness was 125 µm after the film formation. A polyester film was obtained.

Example 3

In the film formation of the biaxially oriented polyester film of Example 1, after the preparation of the crude liquid in the same manner as in Example 1, except that the thickness of the cast film is 1925 µm and the film thickness is 188 µm, the biaxial orientation for optics A polyester film was obtained.

Comparative Example 1

The coating liquid was mixed with 14.8% by weight of a 25% aqueous polyester resin dispersion, 0.7% by weight of a resin having a solid content of 70% by weight, and 77.43% by weight of water, and anionic surfactant was 5.0% by weight in a 10% aqueous solution. The colloidal silica particles were added with 0.07% by weight of a 70% aqueous solution to prepare 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 100 μm.

Comparative Example 2

After the crude liquid was prepared in the same manner as in Comparative Example 1, in the film formation of the biaxially oriented polyester film of Example 2, the thickness of the casting film was 1280 μm, and the film thickness of the biaxially oriented polyester was 125 μm after the film formation. A film was obtained.

Comparative Example 3

After the crude liquid was prepared in the same manner as in Comparative Example 1, in the film formation of the biaxially oriented polyester film of Example 3, the thickness of the casting film was 1925 µm, and the film thickness of the biaxially oriented polyester was 188 µm after the film formation. A film was obtained.

[Comparative Example 4]

The coating liquid was mixed with 16.8% by weight of a polyacrylic resin, 16.8% by weight, and the epoxy-based curing agent was mixed with 0.7% by weight of a resin having a solid content of 70% by weight, and 77.43% by water, and the anionic surfactant was 5.0% by weight in a 10% aqueous solution and a colloid. For the silica particles, 0.07% by weight of a 70% aqueous solution was added to form a coating solution. 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.

[Comparative Example 5]

After preparing the crude liquid in the same manner as in Comparative Example 4, in the film formation of the biaxially oriented polyester film of Example 2, the thickness of the casting film was 1280 μm, and the optical biaxially oriented polyester having a film thickness of 125 μm after film formation. A film was obtained.

Comparative Example 6

After preparing the crude liquid in the same manner as in Comparative Example 4, in the film formation of the biaxially oriented polyester film of Example 3, the thickness of the casting film was 1925 μm, and the film thickness of the biaxially oriented polyester was 188 μm after film formation. A film was obtained.

 Experimental Example 1

The light transmittance (%) of the films prepared in Examples 1 to 3 and Comparative Examples 1 to 6 was measured. The difference between the haze value of the untreated film after measuring the haze value of the scattered light to incident light in% value using a C-light source with a haze meter (model NDH-1001 of Japan Densoku Kogyo Co., Ltd.). Indicated. The smaller the deviation of the haze, the better the transparency of the film.

Experimental Example 2

The adhesion between the substrate and the primer layer of the film prepared in Examples 1 to 3 and Comparative Examples 1 to 6 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. The cellophane tape (No. 405, width of NICHIBAN: 24 mm) is attached to the film with the cutting line, and the tape is rubbed with an eraser to strongly adhere to the film. Then remove the tape 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 3 and Comparative Examples 1 to 6 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

Item Base film thickness (㎛) Type of coating liquid Coating amount (g / ㎡) Haze value (%) Total light transmittance (%) Adhesive to the substrate Adhesiveness in post processing Example 1 100 Polyester polyacrylic 0.08 0.62 93.1 O O Example 2 125 Polyester polyacrylic 0.08 0.71 92.7 O O Example 3 188 Polyester polyacrylic 0.08 0.79 92.2 O O Comparative Example 1 100 Polyester 0.08 0.83 92.8 O X Comparative Example 2 125 Polyester 0.08 0.90 92.6 O X Comparative Example 3 188 Polyester 0.08 1.18 91.9 O X Comparative Example 4 100 Polyacrylic 0.08 0.48 92.6 X O Comparative Example 5 125 Polyacrylic 0.08 0.59 93.2 X O Comparative Example 6 188 Polyacrylic 0.08 0.94 93.0 X O

As can be seen in Table 1, it can be seen that the embodiments according to the present invention have not only sufficient adhesiveness with the substrate as compared with the comparative examples, but also excellent properties such as easy adhesiveness required in the post-processing process. .

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 (3)

As an optical film which used the biaxially-oriented polyester film of thickness 50-300 micrometers as a base material, and formed the primer layer in at least one surface of the said base material as a polymer easily bonding layer, The polymer primer layer comprises a copolyester resin and a polyacrylic resin having a branched monomer as a component, and silica particles or alumina-silica composite oxide particles having an average particle diameter of 50 to 300 nm, wherein the copolyester resin and the polyacryl-based The weight ratio of the resin is 90:10 to 10:90, the content of the silica particles or alumina-silica composite oxide particles is 0.01 to 60% by weight, The surface of the base film on which the primer layer is formed has a total light transmittance of 92% or more, and a haze value of 0.4 to 0.8%, 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 characterized in that 0.05 ~ 3.00㎛, biaxially oriented polyester film.

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