JP2004195741A - Laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated polyester film constituted by providing a coating layer having an excellent effect for preventing the precipitation of an oligomer on the opposite layer of an active energy cured resin layer, having high transparency, reduced in optical defect and excellent in productivity. <P>SOLUTION: The laminated polyester film is constituted by providing the active energy cured resin layer with a thickness of 3-15 μm on one surface of a biaxially stretched polyester film and providing a coating layer containing a silane coupling agent having an amino group on the opposite surface of the active energy cured resin layer. The amount of the oligomer in the surface of the film after 180°C/10 min treatment is not more than 3.0 mg/m<SP>2</SP>. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００５６】
比較例３
実施例１において、活性エネルギー線硬化樹脂層の硬化後の厚さを２．０μｍとした以外は実施例１と同様にして積層ポリエステルフィルムを得た。
【００５７】
比較例４
実施例１において、活性エネルギー線硬化樹脂層の硬化後の厚さを２０μｍとした以外は実施例１と同様にして積層ポリエステルフィルムを得た。
各実施例、比較例で得られたフィルムの評価結果をまとめて下記表２および３に示す。
【００５８】
【表２】

【００５９】
【表３】

【００６０】
【発明の効果】
本発明によれば、高温下でもフィルム表面に析出してくるオリゴマーが少なく、密着性に優れたハードコート層が形成された透明性の良い有用なフィルムを提供することができ、その工業的価値は高い。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laminated polyester film having a hard coat layer, in particular, by providing a coating layer for preventing the precipitation of oligomers on the opposite surface of the hard coat layer, the oligomer precipitation on the film surface is small, and high transparency is achieved. The present invention relates to a laminated polyester film having low optical defects, excellent scratch resistance, excellent surface hardness and the like.
[0002]
[Prior art]
A laminated film in which a hardened layer (hard coat layer) formed by active energy rays is formed on the surface of a biaxially stretched polyester film, has transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, gas barrier properties, and chemical resistance. It is used in many applications including packaging materials, electrical insulating materials, metal vapor deposition materials, plate making materials, magnetic recording materials, display materials, transfer materials, windowing materials, etc.
In particular, in recent years, the progress of electric and electronic information devices has been remarkable, and the methods of using polyester films in such applications have been diverse. For example, a membrane switch used in a wide range of fields, such as a calculator, a personal computer, a microcomputer, a PPC, a microwave oven, a sewing machine, and an electronic toy, and a transparent touch panel provided on the entire display unit such as a CRT and a flat display are mentioned as typical examples.
[0003]
In addition, as the uses of polyester films have diversified, the processing and use conditions of the films have also diversified. For example, if a polyester film is left at a high temperature of 100 ° C. or more, oligomers that have leached from the inside will precipitate on the film surface. There are various problems caused by processing or using a film under these conditions.
Conventionally, methods for preventing the precipitation of oligomers include reducing the amount of oligomers contained in the raw material by solid-phase polymerization and improving the hydrolysis resistance of the polyester film using a terminal blocking agent. However, under severer conditions, there are problems that the prevention of oligomer precipitation cannot be satisfied or the production cost becomes too high.
As described above, various coating films have been proposed for the purpose of modifying the surface of the polyester film. However, depending on the composition to be applied, there is a problem that the precipitation of oligomers is accelerated.
[0004]
[Patent Document 1] JP-A-2000-289168 [Patent Document 2] JP-A-2001-62960
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a problem to be solved is to provide a coating layer having an excellent oligomer deposition preventing effect on the opposite surface of an active energy ray-curable resin layer, thereby providing high transparency. Another object of the present invention is to provide a laminated polyester film having less optical defects and excellent productivity.
[0006]
[Means for Solving the Problems]
The present inventor has conducted intensive studies in view of the above circumstances, and as a result, has found that the above problem can be solved by laminating a specific coating layer on the opposite surface of the active energy ray-curable resin layer. It was completed.
[0007]
That is, the gist of the present invention is that a biaxially stretched polyester film has an active energy ray-curable resin layer having a thickness of 3 to 15 μm on one surface and an amino group-containing silane cup on the opposite surface of the active energy ray-curable resin layer. A laminated polyester film having a coating layer containing a ring agent, wherein the amount of oligomer on the film surface after treatment at 180 ° C. for 10 minutes is 3.0 mg / m ² or less.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
The polyester constituting the polyester film of the present invention is a polyester obtained by polycondensation of a dicarboxylic acid component and a glycol component. As these dicarboxylic acid components, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid, etc. Examples of the glycol component include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, and the like.
[0009]
Typical examples of the polyester used in the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexane dimethylene terephthalate, and the like. May be used, and may contain other components and additives as necessary.
[0010]
The intrinsic viscosity of the polyester film of the present invention is generally in the range of 0.40 to 0.90, preferably 0.45 to 0.80, and more preferably 0.50 to 0.70. When the intrinsic viscosity is less than 0.40, the mechanical strength of the film tends to be weak, and when the intrinsic viscosity is more than 0.90, the melt viscosity becomes high, and a load is applied to the extruder or the production cost is increased. Or other problems may occur.
Conventionally, as a method for reducing oligomers in a film, a method is used in which the amount of oligomers in the polymer is reduced in advance by solid-phase polymerization to reduce the amount of oligomers in the final film. However, there is a problem that the intrinsic viscosity is increased and the cost is increased due to an increase in the number of steps. When the melting temperature is high or the residence time is long in the extruder in the film production process, the effect of reducing the oligomer may not be obtained.
[0011]
The polyester film of the present invention may contain particles for the purpose of imparting lubricity to facilitate handling. Examples of particles used for such purposes include silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and sulfide. Inorganic particles such as molybdenum, crosslinked polymer particles, organic particles such as calcium oxalate, and precipitated particles during the polyester production step can be used.
[0012]
The particle size and content of the particles to be used are selected according to the use and purpose of the film, but the average particle size is usually in the range of 0.005 to 5.0 μm, preferably 0.01 to 3.0 μm. is there. If the average particle size exceeds 5.0 μm, the surface roughness of the film may become too coarse, or the particles may easily fall off the film surface. If the average particle size is less than 0.005 μm, the surface roughness may be too small, and sufficient lubricity may not be obtained. The particle content is usually from 0.001 to 30.0% by weight, preferably from 0.01 to 10.0% by weight, based on the polyester. When the particle amount is large, the mechanical properties and transparency of the film tend to be impaired, and when it is small, the slipperiness tends to be poor.
[0013]
If necessary, additives may be added in addition to the above particles. Examples of such additives include an antistatic agent, a stabilizer, a lubricant, a crosslinking agent, an antiblocking agent, an antioxidant, a dye, a pigment, a light-blocking agent, and an ultraviolet absorber.
The polyester film in the present invention may have a multilayer structure as long as it satisfies the requirements of the present invention. In the case of a multilayer structure, a layer other than polyester may be included. Further, even if the coating layer is provided on only one side of the film, even if provided on both sides, it is naturally included in the concept of the present invention, provided that at least one side of the coating layer satisfies the requirements of the present invention. Good.
[0014]
In the present invention, a film having a content of oligomer (cyclic trimer) of usually 0.5 or more, preferably 0.6% by weight or more, more preferably 0.7% by weight or more is used. When the amount of the film (cyclic trimer) in the film is less than 0.5% by weight, the precipitation of the oligomer on the film surface due to the heat treatment is small, and the precipitation of the oligomer composed of the water-soluble organic silane compound used in the present invention is sealed. The merit of providing a layer to be reduced is reduced.
In order to reduce the amount of oligomers in the film to less than 0.5% by weight, it is necessary to reduce the amount of oligomers contained in the raw material polymer. The increase in the intrinsic viscosity increases the load on the extruder during the production of the film, and lowers the productivity.
[0015]
In the polyester film of the present invention, a polyester oligomer of the film surface in after heat treatment for 10 minutes at 180 ° C. The film is 3.0 mg / ^{m 2} or less, preferably 1.60 mg / ^{m 2} or less, more preferably 1.00mg / M ² or less. When the amount of the surface oligomer exceeds 3.0 mg / m ² , the use of the polyester film is limited, or the oligomer is generated in a large amount at a high temperature and becomes a foreign substance, which is not preferable.
[0016]
When the amount of the polyester oligomer on the film surface after the heat treatment exceeds the above range, in the process of manufacturing a touch panel or the like, the oligomer precipitated on the film surface when heat is applied, thereby deteriorating the transparency of the film or causing optical defects. Or a problem that occurs. In addition, when an overcoat layer is provided and used, there arises a problem that adhesion to the overcoat layer is reduced, or a processing apparatus is soiled and productivity is reduced.
In order to achieve the above object, in the present invention, a coating layer containing a silane coupling agent having an amino group is provided on the opposite surface of the active energy ray-curable resin layer as an oligomer precipitation preventing layer. When there is no coating layer containing a silane coupling agent having an amino group, a large amount of oligomer is deposited on the film surface by heat treatment, so that the deposited oligomer becomes coarse or haze value increases. Not preferred.
[0017]
The silane coupling agent has at least two types of functional groups having different reactivities in one molecule, and is generally a compound represented by YRSix ₃ . Here, Y is an organic functional group such as a vinyl group, an epoxy group, or an amino group, R is an alkylene group such as methylene, ethylene, propylene, and X is a hydrolyzing group such as methoxy and ethoxy and an alkyl group. In the silane coupling agent used in the present invention, it is essential that Y is an amino group. When Y is a vinyl group or an epoxy group, it is not preferable because it has no oligomer sealing effect. Specific compounds include, for example, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxy Silane and the like can be mentioned.
[0018]
Preferred silane coupling agent used in the present invention, a silane coupling agent, the general formula _{Y- (CH 2) 3 -Si- (} X) 3 ( wherein, X is a -OCH ₃ or -OCH ₂ CH ₃ And Y represents —NH ₂ or —NHCH ₂ CH ₂ NH ₂ ). A more preferred silane coupling agent is a compound represented by the general formula Z- (CH ₂ ) ₃ A compound represented by —Si— (X) ₃ (wherein, X represents —OCH ₃ or —OCH ₂ CH ₃ , and Z represents —NHCH ₂ CH ₂ NH ₂ ).
[0019]
The amount of the silane coupling agent having an amino group in the coating solution is preferably 10% by weight or more. If the amount of the silane coupling agent having an amino group in the coating solution is less than 10% by weight, the effect of preventing oligomer precipitation tends to be insufficient.
If necessary, a water-soluble or water-dispersible binder resin other than the above-mentioned silane coupling agent may be used in the oligomer precipitation preventing layer in the present invention. Examples of such a binder resin include polyvinyl alcohol, polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin and the like. Each of these may have a substantially composite structure in which the respective skeletal structures are copolymerized. Examples of the binder resin having a composite structure include acrylic resin-grafted polyester, acrylic resin-grafted polyurethane, vinyl resin-grafted polyester, and vinyl resin-grafted polyurethane. For the purpose of preventing the oligomer from being deposited on the film surface, which is one of the objects of the present invention, it is preferable to use polyvinyl alcohol among the above binders.
[0020]
The amount of the binder component is preferably not more than 50 parts by weight, more preferably not more than 30 parts by weight based on the coating layer.
Further, the coating layer of the film of the present invention may contain a crosslinking reactive compound as required. Examples of the crosslinking reactive compound include methylolated or alkylolated urea-based, melamine-based, guanamine-based, acrylamide-based, polyamide-based compounds, polyamines, epoxy compounds, oxazoline compounds, aziridine compounds, block isocyanate compounds, and silane cups. Ring agents, titanium coupling agents, zircon-aluminate coupling agents, metal chelates, organic acid anhydrides, organic peroxides, polyfunctional low molecular compounds such as heat or photoreactive vinyl compounds and photosensitive resins and It is selected from polymer compounds.
[0021]
The cross-linking reactive compound can improve the cohesiveness, surface hardness, scratch resistance, solvent resistance, and water resistance of the coating layer by mainly performing a cross-linking reaction with the functional group of the resin contained in the coating layer. . For example, when the functional group is a hydroxyl group, the crosslinking reactive compound is preferably a melamine-based compound, a blocked isocyanate compound, an organic acid anhydride, and the like. When the functional group is an organic acid and its anhydride, the crosslinking reactive compound Are preferably epoxy compounds, melamine compounds, oxazoline compounds, metal chelates, and the like. When the functional group is an amine, the crosslinking reactive compound is preferably an epoxy compound, and the resin contained in the coating layer has It is preferable to select and use those having high functional group and crosslinking reaction efficiency. The crosslinking reactive compound may be a low molecular weight compound or a high molecular polymer having a reactive functional group, as long as two or more reactive functional groups are contained in one molecule. The compounding amount of the crosslinking reactive compound is preferably not more than 50 parts by weight, more preferably not more than 30 parts by weight, particularly preferably not more than 15 parts by weight with respect to the coating layer.
[0022]
Further, the coating layer of the present invention may contain inert particles for improving the slipperiness of the coating layer, if necessary. The inert particles include inorganic inert particles and organic inert particles. Examples of the inorganic inert particles include silica sol, alumina sol, calcium carbonate, and titanium oxide. Examples of the organic inert particles include fine particles containing a homopolymer or a copolymer of a polystyrene resin, a polyacrylic resin, and a polyvinyl resin, and organic particles represented by crosslinked particles obtained by combining these with a crosslinkable component. These inert particles preferably have a softening temperature or a decomposition temperature of about 200 ° C. or higher, more preferably 250 ° C. or higher, and particularly preferably 300 ° C. or higher.
[0023]
The average particle size (d) of the inert particles is expressed by the following relationship: 1/3 ≦ d / L ≦ 3, and furthermore, 1/2 ≦ d / L ≦ 2, when the average film thickness of the coating layer is (L). It is preferable to select it to satisfy.
The coating layer of the present invention, if necessary, a surfactant, an antifoaming agent, a coating improver, a thickener, a low-molecular antistatic agent, an organic lubricant, an antioxidant, an ultraviolet absorber, a foaming agent, A small amount of additives such as dyes and pigments may be contained. These additives may be used alone or in combination of two or more as needed.
[0024]
The coating layer of the film of the present invention may be formed on only one side of the polyester film, or may be formed on both sides. In the case of forming on one side only, another type of coating layer may be formed on the opposite side, if necessary, to further impart other characteristics. The film before application may be subjected to a chemical treatment, an electric discharge treatment or the like in order to improve the applicability and adhesion of the application liquid to the film.
The thickness of the coating layer is preferably in the range of 0.01 to 2 μm, more preferably 0.03 to 0.5 μm, and particularly preferably 0.06 to 0.2 μm. When the thickness of the coating layer is less than 0.01 μm, a sufficient effect of preventing oligomer precipitation may not be obtained, and when it exceeds 2 μm, the blocking resistance tends to be insufficient.
[0025]
When the film of the present invention is used for optical purposes such as a touch panel, the haze value is preferably 3.0% or less, more preferably 2.0% or less. When the film haze exceeds 3.0%, it may not be preferable for optical use. Further, the change in the film haze due to the heat treatment at 180 ° C. for 10 minutes is preferably 2.0%, more preferably 1.5% or less. When the change in the haze of the film by heat treatment at 180 ° C. for 10 minutes exceeds 2.0%, the effect of the oligomer sealing layer tends to be small, and the oligomer is precipitated on the film surface by heat treatment in the manufacturing process, The precipitated oligomer may become coarse particles.
[0026]
As a method for producing the biaxially stretched polyester film, a known method can be employed. For example, a pre-dried polyester chip and necessary additives are mixed, put into a hopper into an extruder, melt-kneaded at a temperature of 200 to 300 ° C. by an extruder, extruded from a die into a sheet, and heated to about 70 ° C. or less. Quenched on a casting drum (rotary cooling drum) to obtain an unstretched sheet, and stretch the obtained sheet in the machine direction by 4 times or more, preferably 9 times or more in the longitudinal and transverse directions. A method of performing heat fixation at the temperature described above can be adopted.
[0027]
The method of forming the coating layer on the surface of the biaxially stretched polyester film is not particularly limited, but a method of applying a coating liquid during the process of manufacturing the polyester film is preferably employed. Specifically, a method of applying and drying a coating solution on an unstretched sheet surface, a method of applying and drying a coating solution on a monoaxially stretched film surface, and a method of applying and drying a coating solution on a biaxially stretched film surface And the like. Among these, it is economical to apply a coating solution to the surface of an unstretched film or a uniaxially stretched film and then simultaneously dry-harden the coating layer in the process of performing a heat treatment on the film.
In addition, as a method for forming the coating layer, a method using some of the above-described coating methods in combination may be employed as necessary. Specifically, there is a method in which the first layer is applied to the surface of the unstretched sheet and dried, then stretched in a uniaxial direction, and then the second layer is applied and dried.
[0028]
As a method of applying the coating liquid on the surface of the polyester film, use of a reverse roll coater, a gravure coater, a rod coater, an air doctor coater, etc. described in "Coating method", written by Yuji Harasaki, Maki Shoten, 1979. Can be.
It is preferable that the coating liquid used in the present invention is usually adjusted with water as a main medium from the viewpoint of safety and hygiene. As long as water is the main medium, a small amount of organic solvent may be contained for the purpose of improving dispersion in water or improving film forming performance. When the organic solvent is used by mixing with water as a main medium, it is preferable to use the organic solvent within a range that dissolves in water. However, if it is a stable emulsion that does not separate when left for a long time, It may be used without dissolving in water. The organic solvent may be used alone, but may be used in combination of two or more if necessary, or may be used in combination of two or more as needed.
[0029]
The laminated polyester film of the present invention is characterized in that a biaxially stretched polyester film is provided with a hard coat layer composed of an active energy ray-curable resin layer.
In the present invention, as the curing component of the active energy ray-curable resin layer, unsaturated polyester resin, acrylic, addition polymerization, hybrid thiol / acryl, cationic polymerization, hybrid polymerization of cationic polymerization and radical polymerization, etc. Can be used. Among these, an acrylic curing component is preferred from the viewpoints of curability, scratch resistance, surface hardness, flexibility and durability.
The acrylic curing component contains an acrylic oligomer as an active energy ray polymerization component and a reactive diluent. And, if necessary, a photopolymerization initiator, a photosensitizer, and a modifier are contained.
[0030]
A typical example of the acrylic oligomer is an oligomer in which a reactive acryloyl group or methacryloyl group is bonded to an acrylic resin skeleton. Other acrylic oligomers include polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, polyether (meth) acrylate, silicone (meth) acrylate, polybutadiene (meth) acrylate, and the like. Further, an oligomer in which an acryloyl group or a methacryloyl group is bonded to a rigid skeleton such as melamine, isocyanuric acid, and cyclic phosphazene is exemplified.
[0031]
The reactive diluent functions as a solvent in the coating process as a medium for the coating agent, and itself has a group that reacts with a polyfunctional or monofunctional acrylic oligomer. It becomes. Specific examples of the reactive diluent 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, trimethylolpropane tri (meth) acrylate, ethylene glycol (meth) acrylate, propylene glycol di (meth) acrylate, (meth) acryloyloxypropyltriethoxysilane, (meth) acryloyl Oxypropyltrimethoxysilane and the like can be mentioned.
[0032]
Examples of the photopolymerization initiator include 2,2-ethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and p -Chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, 2-chlorothioxanthone, anthraquinone, phenyldisulphide, 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone and the like.
[0033]
Examples of the photosensitizer include tertiary amines such as triethylamine, triethanolamine and 2-dimethylaminoethanol, alkylphosphines such as triphenylphosphine, and thioethers such as β-thiodiglycol.
Examples of the modifier include a coating improver, an antifoaming agent, a thickener, an inorganic particle, an organic particle, a lubricant, an organic polymer, a dye, a pigment, and a stabilizer. These are used in a range that does not inhibit the reaction by the active energy ray, and can improve the properties of the active energy ray-curable resin layer according to the application. An organic solvent can be added to the composition of the active energy ray-curable resin layer for the purpose of improving workability during coating and controlling the coating thickness.
[0034]
The active energy ray-curable resin layer is formed by applying the curing resin composition to the surface of the coating layer and then irradiating with an active energy ray to cross-link and cure. As the active energy rays, ultraviolet rays, visible rays, electron beams, X-rays, α-rays, β-rays, and γ-rays can be used. Irradiation with active energy rays is usually performed from the coating layer side, but may be performed from the film surface side in order to enhance the adhesion to the film. May be provided.
[0035]
The thickness of the active energy ray-curable resin layer is in the range of 3 to 15 μm, preferably 5 to 10 μm. If the thickness of the cured resin layer is less than 3 μm, the surface hardness may be insufficient. If the thickness exceeds 15 μm, the cured resin layer may have a large curing shrinkage and the film may curl toward the cured resin layer. There is.
When the active energy ray-curable resin is used on one side, curling of the film is caused by curing shrinkage of the active energy ray-curable resin. In the present invention, the curl value is preferably 15 mm or less, more preferably 10 mm or less. If the curl value exceeds 15 mm, the yield may deteriorate in the manufacturing process or the product may be unfavorable.
[0036]
In the present invention, the surface hardness on the cured resin layer side is usually 2H or more, preferably 3H or more. If it is less than 2H, the scratch resistance may be insufficient.
In the present invention, in order to improve the adhesion of the active energy ray-curable resin layer to the base film, the film may be subjected to a chemical treatment or a discharge treatment, preferably between the film and the active energy ray-curable resin layer. Is provided with an easy adhesion layer. Further, an intermediate layer such as an antistatic layer may be provided as necessary. As a method for providing such an easy-adhesion layer or another intermediate layer, a coextrusion method or a coating method may be employed.
[0037]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In addition, the measuring method and definition of various physical properties and characteristics in the present invention are as follows. In Examples and Comparative Examples, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.
[0038]
(1) Measurement of Intrinsic Viscosity of Polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester were removed was precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added. Dissolved and measured at 30 ° C.
[0039]
(2) average particle size _{(d 50)}
The particle size was measured by a sedimentation method based on Stokes' resistance law using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation.
[0040]
(3) Oligomer (cyclic trimer) content in polyethylene terephthalate After a predetermined amount of polyethylene terephthalate is dissolved in o-chlorophenol, reprecipitated with tetrahydrofuran and filtered to remove linear polyethylene terephthalate, and then The obtained filtrate was supplied to liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer (cyclic trimer) contained in polyethylene terephthalate, and this value was divided by the amount of polyethylene terephthalate used in the measurement to obtain polyethylene. The amount of oligomer (cyclic trimer) contained in terephthalate.
The amount of oligomer (cyclic trimer) determined by liquid chromatography was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method).
The standard sample was prepared by accurately weighing oligomers (cyclic trimers) collected in advance and dissolving them in accurately weighed DMF (dimethylformamide). The concentration of the standard sample is preferably in the range of 0.001 mg / ml to 0.50 mg / ml.
The conditions of the liquid chromatograph were as follows.
Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: MCI GEL ODS 1HU manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm
[0041]
(4) The amount of oligomer on the film surface after the heat treatment The polyester film was left in an oven at 180 ° C. for 10 minutes in a nitrogen atmosphere to perform the heat treatment. A 5 cm square sample is cut out of the polyester film after the heat treatment (the sample area of the cut out 5 cm square is 50 cm ₂ for both sides), 4 ml of DMF is placed in a suitable container (such as a petri dish), and the 5 cm square is placed in the container. Put the sample. At this time, both sides of the sample were immersed in DMF and treated for 3 minutes to dissolve the oligomer precipitated on the film surface by the heat treatment. Next, after standing for 3 minutes, the DMF was collected, supplied to a liquid chromatography (Shimadzu LC-7A) to determine the amount of oligomer in DMF, and this value was divided by the area of the film contacted with DMF to obtain the amount of oligomer on the film surface. (Mg / m ² ). The amount of oligomer in DMF was determined from the peak area ratio between the standard sample peak area and the measurement sample peak area (absolute calibration curve method).
The standard sample was prepared by accurately weighing oligomers (cyclic trimers) fractionated in advance and dissolving in accurately weighed DMF. The concentration of the standard sample is preferably in the range of 0.001 mg / ml to 0.01 mg / ml.
The conditions of the liquid chromatograph were the same as those described in the above section (3).
[0042]
(5) Pencil hardness In accordance with JIS K5400 (1990), pencils of various hardnesses are applied to the surface of the cured resin layer at an angle of 45 ° to give a scratch under a load of 1 kg. The surface hardness was used.
[0043]
(6) A sample having a curl value of 100 mm × 100 mm was placed on a flat surface with the concave surface facing upward, the height of the four corners jumped was measured, and the average value was taken as the curl value.
[0044]
(7) Film haze According to JIS-K6714, the turbidity of the film was measured with a spectroscopic turbidimeter NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd.
[0045]
(8) Change in Haze Value Due to Heat Treatment The film haze of each of the film before the heat treatment and the film after the heat treatment was measured, and the change in the haze value due to the heat treatment was determined by the following equation.
Film haze value after heat treatment-Film haze value before heat treatment = change in haze value
(9) Polymerization step of productivity raw material Judgment was made as follows from the production cost in the film film formation step and the like.
：: There is no problem in the manufacturing process and manufacturing conditions, and the productivity is high.
Δ: Manufacturing process, manufacturing conditions, and the like are somewhat limited, and productivity is slightly low.
X: Production process and film forming conditions are limited, and productivity is poor.
[0047]
(10) Appropriateness for optical applications From the characteristics such as haze and coating film strength after heat treatment, the suitability for optical applications such as touch panels was determined based on the following three rank criteria.
：: Low haze value, sufficient coating strength, suitable for optical applications, and high productivity. △: Slight problem with haze value, coating strength, or productivity, but no practical problem x: Haze value Not suitable for optical applications due to problems such as coating film strength, productivity, etc.
In Examples and Comparative Examples, binder resins and the like used for forming the oligomer precipitation preventing layer are as follows.
[0049]
[Example of compound]
Silane coupling agent (A): N-β (aminoethyl) γ-aminopropyltrimethoxysilane silane coupling agent (B): N-β (aminoethyl) γ-aminopropyltriethoxysilane silane coupling agent (C ): Γ-aminopropyltrimethoxysilane silane coupling agent (D): N-phenyl-γ-aminopropyltrimethoxysilane silane coupling agent (E): γ-glycidoxypropyltriethoxysilane The silane coupling agent (E) was difficult to dissolve in pure water, and the concentration was adjusted using 2% acetic acid water as a diluent. Concentrations of other silane coupling agents were adjusted using pure water as a diluent.
PVA resin: Polyvinyl alcohol polyurethane aqueous dispersion A having a degree of saponification of 88 mol% and a degree of polymerization of 500: Hydran AP-40 manufactured by Dainippon Chemical Industries, Ltd.
Polyester aqueous dispersion B: Finetex ES-670 manufactured by Dainippon Chemical Co., Ltd.
[0050]
[Adjustment of coating liquid-1]
A coating solution containing 90% by weight of the silane coupling agent (A) and 10% by weight of the PVA-based resin was prepared. The solid content concentration of the coating solution was 2% by weight.
[0051]
[Preparation of coating liquid-2]
A coating solution containing 80% by weight of the polyurethane aqueous dispersion A and 20% by weight of the polyester aqueous dispersion B was prepared. The coating solution had a solid concentration of 2% by weight.
[0052]
[Method for producing polyester (I)]
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.09 parts by weight of magnesium acetate tetrahydrate is placed in a reactor as a catalyst, the reaction start temperature is set to 150 ° C., and methanol is gradually distilled off. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After 0.04 parts of ethyl acid phosphate was added to the reaction mixture, 0.05 parts of silica particles dispersed in ethylene glycol having an average particle diameter of 1.6 μm and 0.04 parts of antimony trioxide were added to obtain 4 parts. A time polycondensation reaction was performed. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from the normal pressure, and finally was 0.3 mmHg. After 4 hours from the start of the reaction, the reaction was stopped, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (I) was 0.65, and the content of the oligomer (cyclic trimer) was 1.01% by weight.
[Production method of polyester (II)]
Polyester (I) was subjected to solid phase polymerization to obtain polyester (II). The intrinsic viscosity of the obtained polyester (II) was 0.86, and the content of the oligomer (cyclic trimer) was 0.32% by weight.
[Production method of polyester (III)]
Polyester (I) was subjected to solid phase polymerization for a longer time than the polymerization time at the time of production of polyester (II) to obtain polyester (III). The intrinsic viscosity of the obtained polyester (III) was 0.79, and the content of the oligomer (cyclic trimer) was 0.50% by weight.
[0053]
Example 1
[Production of film]
The polyester (I) obtained by the method for producing a polyester is dried at 180 ° C. for 4 hours in an inert gas atmosphere, melt-extruded at 290 ° C. by a melt extruder, and the surface temperature is adjusted using an electrostatic contact method. It was cooled and solidified on a cooling roll set at 40 ° C. to obtain an unstretched sheet. Next, after stretching 3.5 times in the longitudinal direction at 83 ° C., coating solution-1 and coating solution-2 are applied to the surface of each of the longitudinally stretched films, and stretched 3.2 times in the transverse direction at 110 ° C. Furthermore, heat treatment was performed at 220 ° C. to obtain a 125 μm-thick laminated polyester film having a 0.05 μm-thick coating layer on both sides.
The intrinsic viscosity of the obtained film was 0.60, and the content of the oligomer (cyclic trimer) was 1.12% by weight.
Next, an active energy ray-curable resin is applied to the coating surface of the obtained film with the coating liquid-2 so that the thickness after curing becomes 8 μm, and the irradiation distance is 100 mm using a high-pressure mercury lamp having an energy of 120 W / cm. For about 10 seconds.
As the active energy ray-curable resin, a composition comprising 77 parts of Nippon Kayaku's KAYARAD DPHA, 18 parts of Nippon Kayaku's KAYARAD R-128H, and 5 parts of Ciba Geigy's IRGACURE 651 was used.
[0054]
Examples 2 to 4 and Comparative Examples 1 and 2
A film was obtained in the same manner as in Example 1, except that the composition of the coating solution-1 was changed as shown in Table 1 below.
[0055]
[Table 1]

[0056]
Comparative Example 3
A laminated polyester film was obtained in the same manner as in Example 1 except that the thickness of the active energy ray-curable resin layer after curing was 2.0 μm.
[0057]
Comparative Example 4
A laminated polyester film was obtained in the same manner as in Example 1, except that the thickness of the active energy ray-curable resin layer after curing was changed to 20 μm.
The evaluation results of the films obtained in each of the examples and comparative examples are summarized in Tables 2 and 3 below.
[0058]
[Table 2]

[0059]
[Table 3]

[0060]
【The invention's effect】
According to the present invention, it is possible to provide a useful film having good transparency on which a hard coat layer having excellent adhesion is formed, with a small amount of oligomers precipitated on the film surface even at a high temperature. Is expensive.

Claims (5)

One side of the biaxially stretched polyester film has an active energy ray-curable resin layer having a thickness of 3 to 15 μm, and on the opposite side of the active energy ray-curable resin layer, a coating layer containing a silane coupling agent having an amino group. A laminated polyester film, wherein the amount of oligomer on the film surface after treatment at 180 ° C. for 10 minutes is 3.0 mg / m ² or less. Silane coupling agent of the general formula _{Y- (CH 2) 3 -Si- (} X) 3 ( wherein, X represents an -OCH ₃ or -OCH ₂ CH _3, Y is, -NH ₂ or -NHCH _2. The laminated polyester film according to claim 1, wherein the compound is represented by the formula: ₂ CH ₂ NH ₂ ). Silane coupling agent of the general formula _{Z- (CH 2) 3 -Si- (} X) 3 ( wherein, X represents an -OCH ₃ or -OCH ₂ CH3, Z is, -NHCH ₂ CH ₂ NH ₂ The laminated polyester film according to claim 1, which is a compound represented by the following formula: The laminated polyester film according to any one of claims 1 to 3, wherein the film haze is 3.0% or less, and the increase in the film haze after heat treatment at 180 ° C for 10 minutes is 2.0% or less. . The laminated polyester film according to claim 1, wherein the oligomer (cyclic trimer) content of the film is 0.5% by weight or more.