JP4983119B2 - Biaxially stretched polyester film for in-mold molding - Google Patents

Description

  The present invention relates to a biaxially stretched polyester film for in-mold molding. More specifically, the present invention relates to a biaxially stretched polyester film for in-mold molding that is excellent in moldability, processability, gloss on the surface of a molded product after transfer, and handling properties.

  Biaxially oriented polyester film represented by polyethylene terephthalate (PET) film is used in a wide range of fields such as industrial materials, magnetic recording materials and packaging materials because of its excellent mechanical strength, thermal properties, humidity properties and many other excellent properties. in use.

  In general, a transfer foil is formed by sequentially laminating an easy-adhesion layer, a release layer, a printing layer, an adhesive layer, and the like on one surface (transfer surface) of a polyester film as a base material. As a transfer method of these transfer foils, a transfer device is used to transfer to a transfer object with a heating roll, or a so-called hot stamping method, or an adhesive layer is in contact with a mold resin of an injection molding machine or a blow molding machine. After setting the transfer material, injection molding or blowing of molding resin, transfer at the same time as molding, take out the molded product from the mold after cooling, generally known as so-called molding simultaneous transfer method represented by in-mold molding, etc. It has been. The in-mold molding method can be molded and transferred at the same time, so it is very useful for applying complex patterns, and is used for household appliances, automobile parts, kitchenware, cosmetic containers, toys and stationery. Widely used in plastic molded products.

  Further, in recent years, various demands for a base film used for in-mold molding have increased. For example, a polyester film for molding process excellent in deep drawing followability and laminating property using a copolyester (refer to Patent Document 1), and using a substantially single polyester component, it is difficult to develop with a copolyester. A biaxially stretched polyester film (see Patent Document 2) excellent in moldability that can retain chemical properties and the like has been proposed. Further, for the purpose of improving the workability of the molded film, a molding polyester film imparted with antistatic properties (see Patent Documents 3 and 4) has been proposed.

However, recently, there is a demand not only for formability and workability, but also for further improvement in order to improve production efficiency and achieve higher designability. For example, in forming a metal substitute, high smoothness is required on the transfer surface side of the forming film in order to express high gloss. In addition, since the handling property at the time of processing deteriorates due to high smoothness of the transfer surface, improvement is also demanded at the same time. Furthermore, in any of the patent documents exemplified above, there remains room for improvement with respect to film breakage during molding, transfer accuracy, mold contamination, and the like.
JP-A-6-218893 JP-A-9-141735 JP 2003-54143 A JP 2004-58648 A

  In view of such a situation, the present invention aims to improve such drawbacks and provide a biaxially stretched polyester film for in-mold molding that is excellent in moldability, processability, handling during processing, and high gloss. It is what.

In order to achieve this object, the biaxially stretched polyester film for in-mold molding of the present invention has the following constitution. That is, the biaxially stretched polyester film for in-mold molding of the present invention has at least two layers in which the root mean square roughness RMS of the transfer surface is less than 10 nm and the root mean square roughness RMS of the non-transfer surface is 10 nm or more and less than 100 nm. A biaxially stretched polyester film having the above polyester film layer, at least the plane orientation coefficient of the transfer surface is 0.15 or less, and the average value of the breaking elongation in the MD direction and TD direction of the film is 180% or more, 150 ° C. In-mold molding having an antistatic layer satisfying the following requirements (1) and (2) on the non-transfer surface: It is an axially stretched polyester film.
(1) Antistatic layer formed by coating layer containing polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative (2) Surface specific resistance of antistatic layer surface is 1 × 10 ¹³ Ω / □ or less

And the biaxially stretched polyester film for in-mold molding of this invention has the following preferable aspect.
(A) The antistatic layer contains polythiophene and / or a polythiophene derivative, and the surface specific resistance of the surface of the antistatic layer is 1 × 10 ¹⁰ Ω / □ or less.
(B) Having an easy-adhesion layer formed of a coating layer containing a polyester resin on the transfer surface.
(C) The amount of oligomer deposited on the non-transfer surface after heat-treating the polyester film at 180 ° C. for 30 minutes is 3.0 mg / m ² or less.
(D) The root mean square roughness RMS of the transfer surface is less than 7 nm.
(E) The average value of the elongation at break in the MD direction and the TD direction of the polyester film is 200% or more.
(F) When the polyester film is heated at 150 ° C. for 30 minutes, the thermal shrinkage rate in the TD direction of the film is 0.5% or less.
(G) A titanium compound is used as a polymerization catalyst for the polyester constituting the polyester film.
(H) The polyester film is a simultaneous biaxially stretched film.
(I) It is a transfer foil for in-mold molding using the biaxially stretched polyester film for in-mold molding.

  ADVANTAGE OF THE INVENTION According to this invention, the biaxially stretched polyester film for in-mold shaping | molding excellent in workability, handling property, the glossiness of a molded article surface, a moldability, a transfer precision, an oligomer precipitation prevention function, etc. can be created.

  Hereinafter, the biaxially stretched polyester film for in-mold molding of the present invention will be described in more detail. The polyester film which is the base material of the biaxially stretched polyester film for in-mold molding of the present invention is basically composed of polyester.

  The polyester used in the present invention is a polymer compound having an ester bond as the main bond chain of the main chain, and can be obtained by polycondensation of dicarboxylic acid and diol. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, diphenylcarboxylic acid, diphenylsulfone dicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic acid and other aromatic dicarboxylic acids, oxalic acid, and succinic acid. , Eicoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids, trimellitic acid, and pyromellitic acid, etc. A polyfunctional acid etc. can be mentioned. On the other hand, examples of the diol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol and triethylene glycol, aromatic glycols such as bisphenol A and bisphenol S, diethylene glycol, And polytetramethylene glycol.

  In the polyester, there are various additives such as antioxidants, heat stabilizers, weathering stabilizers, UV absorbers, organic lubricants, organic and inorganic particles, pigments, dyes, fillers, antistatic agents and nuclei. An agent or the like may be added as long as the effects of the present invention are not impaired.

  Further, when a titanium-based catalyst is used as a polyester polymerization catalyst, aggregates are reduced, which is a more preferable mode. Examples of the titanium-based polymerization catalyst include titanium alkoxides such as titanium tetrabutoxide and titanium tetraisopropoxide, composite oxides and titanium complexes whose main metal elements are titanium and silicon, and the obtained polyester. It is preferable to use 0.0005 to 0.15% by weight in terms of titanium atoms. The polyester thus obtained contains a titanium-based catalyst, and in some cases, the polymerization catalyst function may be deactivated.

  The thickness of the biaxially stretched polyester film for in-mold molding of the present invention is not particularly limited because it is appropriately selected according to the use for which the biaxially stretched polyester film for in-mold molding of the present invention is used. From the viewpoints of handling properties and productivity, the thickness is preferably 12 to 188 μm, and most preferably 30 to 100 μm.

  In the present invention, it is necessary to achieve the object of the present invention that the root mean square roughness RMS of the transfer surface is less than 10 nm, preferably less than 7 nm. That is, by making the transfer surface highly smooth, the release layer, the protective layer, and the printing layer that are sequentially laminated on the transfer surface are also highly smooth, so the surface of the transferred object after transfer is also highly smooth, As a result, the glossiness of the molded product surface is increased. When the value of the root mean square roughness RMS exceeds 10 nm, a desired glossiness cannot be obtained. Moreover, the lower limit of the value of the root mean square roughness RMS is not particularly limited, but is preferably 1 nm or more from the viewpoint of film forming stability, slit property after film forming, film transportability during processing, and the like. Here, the root mean square roughness RMS is the root mean square of the difference Z (x) between the height direction of the roughness curved surface and the center surface of the roughness curved surface at the reference length lr. expressed.

  The method for achieving the above surface state is not particularly limited, but organic or / and inorganic particles having a specific particle size / size distribution are polyester film layers on the transfer surface side (hereinafter referred to as “A layer”). The method of making it contain in the polyester which comprises these, or the coating layer on A layer, etc. are mentioned.

  Examples of the organic particles include crosslinked polystyrene, crosslinked acrylic resin, melamine resin, and benzoguanamine resin. As the inorganic particles, for example, silica, colloidal silica, beaded silica, alumina, alumina sol, kaolin, talc, mica, clay, calcium carbonate, metal oxide (such as tin oxide) and the like are preferably used. These organic particles and inorganic particles are preferably spherical monodisperse particles. Moreover, as a particle | grain size, it is preferable that an average particle diameter is 0.001-6 micrometers, More preferably, it is 0.01-3 micrometers, Most preferably, it is 0.05-1.5 micrometers. In order to prevent the particles from falling off, the particles are preferably contained in the base polyester constituting the A layer.

  Although it does not specifically limit as content of this particle | grain, 0.0001-50 weight% with respect to the sum total of resin which forms A layer can be mentioned as a preferable range.

  In the present invention, the root mean square roughness RMS of the non-transfer surface is 10 nm or more and less than 100 nm, more preferably 12 nm or more and less than 50 nm. That is, by roughening the non-transfer surface, the slipping property at the time of roll handling and processing is improved and the handling property is improved. When the thickness is 100 nm or more, the transfer surface becomes rough and the transfer surface becomes rough. On the other hand, when the thickness is less than 10 nm, the slipping property is deteriorated and the handling property is inferior.

  The method for achieving the above surface state is not particularly limited, but organic or / and inorganic particles having a specific particle size / size distribution are referred to as a polyester film layer (hereinafter referred to as “B layer”) on the non-transfer surface side. And the like are included in the polyester constituting the composition or in the coating layer on the B layer.

  As the types and shapes of the organic particles and inorganic particles, the same ones as described above in the polyester constituting the A layer or in the coating layer on the A layer can be preferably exemplified. Moreover, as a particle | grain size, it is preferable that an average particle diameter is 0.001-6 micrometers, More preferably, it is 0.05-4 micrometers, Most preferably, it is 0.1-3.0 micrometers. In order to prevent the particles from falling off, the particles are preferably contained in the base polyester constituting the B layer.

  Although it does not specifically limit as content of this particle | grain, 0.0001-50 weight% with respect to the sum total of resin which forms B layer can be mentioned as a preferable range.

  The biaxially stretched polyester film for in-mold molding of the present invention is composed of at least two polyester film layers. As described above, in order to achieve the object of the present invention, it is necessary to design the transfer surface to be smooth and the non-transfer surface to be rough. In order to provide two surfaces having different roughnesses, the T-die composite It is common and economical to make a laminated film by a co-extrusion method using a die, and for an easy method. Here, the biaxially stretched polyester film for in-mold molding of the present invention has a two-layer structure of A / B layers, a three-layer structure of A / C / B layers, or an A / C / D ... / B layer. Any of the multi-layer configuration of three or more layers may be used. A multilayer configuration of three or more layers is a more preferable mode because the recovered raw material can be used for the inner layer and the cost can be reduced by reducing the thickness of the A layer and the B layer.

  The biaxially stretched polyester film for in-mold molding of the present invention needs to have at least a plane orientation coefficient of 0.15 or less on the transfer surface. Here, the plane orientation coefficient is defined as follows. “When the refractive index in the MD direction, TD direction, and thickness direction is nx, ny, and nz, respectively, the plane orientation coefficient fn = (nx + ny) / 2−nz”, the plane orientation coefficient is an index of moldability, and the transfer surface side When the plane orientation coefficient exceeds 0.15, the shape following property to the plastic surface is deteriorated and the moldability and transfer accuracy are inferior. The lower limit of the plane orientation coefficient is not particularly limited, but if the plane orientation coefficient is too low, the film-forming stability is lowered or the surface becomes sticky in the process, so that it is 0.12 or more. Is preferred. The method of setting the plane orientation coefficient to 0.15 or less is not particularly limited, but the longitudinal and lateral magnifications are set to about 3.0 to 3.4 times, respectively, and the heat treatment temperature after transverse stretching is about 200 to 220 ° C. A method of setting to can be preferably mentioned.

The biaxially stretched polyester film for in-mold molding of the present invention needs to have an average value of breaking elongation in the MD direction and TD direction of 180% or more, and preferably 200% or more. Here, the average value of the elongation at break is defined as follows. In the in-mold molding process, “average value of breaking elongation S = (S _MD + S _TD ) / 2 where S _{MD is} the breaking elongation in the MD direction and S _TD is the breaking elongation in the TD direction”. The foil deforms following the unevenness of the mold and merges with the molten plastic. Since plastic and metal molds have a three-dimensional structure, it is necessary to extend isotropically in all directions. If the average value of the breaking elongation in the MD and TD directions is 180% or less, the moldability is poor. There is a possibility that film breakage may occur during molding. The upper limit of the average value of elongation at break is not particularly limited, but if the elongation at break is too large, the film forming stability and the production cost are inferior, and heat shrinkage becomes large and the transfer accuracy is lowered. The following is preferable. A method for setting the average value of the breaking elongation to 180% or more is not particularly limited, but a method of setting the vertical and horizontal magnifications to about 3.0 to 3.4 times can be preferably mentioned.

  The biaxially stretched polyester film for in-mold molding of the present invention needs to have a thermal shrinkage rate in the TD direction of 0.8% when heated at 150 ° C. for 30 minutes, preferably 0.5% or less. This is because if thermal contraction in the TD direction occurs during processing, printing deviation occurs in the transfer process, and transfer accuracy decreases. When the thermal contraction rate in the TD direction exceeds 0.8%, the frequency of printing deviation increases. The lower limit of the heat shrinkage rate in the TD direction is not particularly limited, but if the heat shrinkage rate is too low, the film-forming stability is lowered, so 0.0% or more is preferable. The method for setting the thermal shrinkage rate in the TD direction to 0.8% or less is not particularly limited, but the heat treatment temperature after transverse stretching is set to about 170 to 220 ° C., and at the same time, relaxation treatment after transverse stretching is performed. A preferred method is about 1.0 to 6.0%.

  The biaxially stretched polyester film for in-mold molding of the present invention needs to have an antistatic layer formed of a coating film containing polystyrene sulfonic acid and / or a polystyrene sulfonic acid derivative on the non-transfer surface. That is, since the generation of static electricity can be suppressed by having the antistatic layer, there is an effect of reducing troubles due to dust adhesion or generation of whiskers during processing, and a dramatic improvement in yield can be expected.

  The antistatic layer may be applied to the outer layer as a multilayer structure, or to an off-line coating method after film formation, but the antistatic layer is used to prevent environmental contamination and explosion resistance during film production. From the viewpoint of production cost, the coating layer is preferably formed by being stretched in at least one direction after the application of the aqueous coating liquid, and is preferably formed within the production process for biaxially orienting the polyester film. . In order to enable aqueous coating, it is essential to form an antistatic agent with a component having high water dispersibility. Polystyrene sulfonic acid and / or polystyrene sulfonic acid derivatives have extremely high water dispersibility and stretchability, and are a preferred embodiment as a component of the antistatic agent of the present invention. Although the timing of the stretching is not particularly limited, a method of biaxial stretching after applying an aqueous coating liquid, or a method of applying an aqueous coating liquid after longitudinal stretching and further lateral stretching is preferably used. As a coating method of the aqueous coating liquid, various coating methods such as reverse coating method, gravure coating method, rod coating method, bar coating method, die coating method and spray coating method can be preferably used. It is not limited.

  The molecular weight of the polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative used in the present invention is not particularly limited, but the weight average molecular weight is preferably 1,000 to 1,000,000, more preferably 5,000 from the viewpoint of the stability and conductivity of the coating material. ~ 150,000.

  The thickness of the antistatic layer in the present invention is usually preferably 10 to 1000 nm, more preferably 15 to 200 nm, and most preferably 30 to 100 nm. If the thickness of the antistatic layer is too thin, the antistatic function will be poor. On the other hand, when the thickness of the antistatic layer is too thick, the appearance is inferior, the antistatic layer falls off during the production process, and the production cost of the film is increased.

  In the antistatic layer of the present invention, for example, polyester resin, polyurethane resin, antioxidant, heat stabilizer, weather stabilizer, ultraviolet absorber, organic Lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, and nucleating agents may be blended. The lubricant and fine particles have the effect of improving the slipperiness of the film and facilitating handling. The average particle size of the lubricant and fine particles is preferably 50% to 500% of the thickness of the antistatic layer. If the average particle size is less than 50%, the slippery effect is insufficient, and if it exceeds 500%, the slippery agent and fine particles are likely to fall off. Moreover, the polyester resin mix | blended is anticipated the effect which improves adhesiveness with a base-material polyester film.

The surface specific resistance of the surface of the antistatic layer is preferably 1 × 10 ¹³ Ω / □ or less, more preferably 1 × 10 ¹¹ Ω / □ or less, and most preferably 1 × 10 ⁷ Ω / □ or less. . When the surface specific resistance exceeds 1 × 10 ¹³ Ω / □, the antistatic performance is inferior and it is difficult to improve troubles in the processing process. The lower limit value of the surface specific resistance is not particularly limited, but is preferably 1 × 10 ² Ω / □ or more from the viewpoint of production cost and film formation stability.

  In the biaxially stretched polyester film for in-mold molding of the present invention, in addition to polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative, the polyaniline-based conductive agent and tin oxide-based conductive material which are conjugated electronic conductors are added to the antistatic layer. More preferably, it contains an agent, polythiophene and / or polythiophene derivative. The conjugated electron conductor is preferable because its electronic conduction mechanism does not depend on moisture in the air, and therefore, the amount of change in antistatic performance due to humidity is very small, and further higher antistatic properties can be imparted. In particular, polythiophene and / or polythiophene derivatives are particularly preferred because they are excellent in transparency of the coating film, adhesion to the base polyester film, and coating appearance.

  Polythiophene and / or polythiophene derivatives are very difficult to disperse in water by themselves, and are easily dispersed in water or become water-based by polymerization in the presence of polystyrene sulfonic acid and / or polystyrene sulfonic acid derivatives. Furthermore, it is considered that the function as an acid also functions as a dopant for the polythiophene compound.

  The polythiophene and / or polythiophene derivative which is a conjugated electron conductor is obtained by, for example, reacting a compound represented by the following general formula (1) or the following general formula (2) in the presence of polystyrene sulfonic acid and / or a polystyrene sulfonic acid derivative. Can be obtained by polymerization.

  In the general formula (1), R1 and R2 each independently represent a hydrogen element, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group, for example, Methyl group, ethyl group, propyl group, isopropyl group, butyl group, cyclohexylene group and phenyl group. Moreover, in said General formula (2), n is an integer of 1-4.

  In the biaxially stretched polyester film for in-mold molding of the present invention, it is preferable to use a polythiophene derivative having the structural formula represented by the general formula (2). For example, in the general formula (2), n = 1 ( Methylene group), n = 2 (ethylene group) and n = 3 (propylene group) are preferred. Among them, particularly preferable is an ethylene group compound of n = 2, that is, poly-3,4-ethylenedioxythiophene. Examples of the polythiophene derivative include compounds in which functional groups are bonded to the 3rd and 4th positions of the thiophene ring. As described above, a compound in which an oxygen atom is bonded to the 3rd and 4th carbon atoms is preferable. For a compound having a structure in which a carbon atom or a hydrogen atom is directly bonded to the carbon atom, it may not be easy to make the coating liquid aqueous.

  Polystyrene sulfonic acid and / or polystyrene sulfonic acid derivatives have been found to be shifted to the acidic side due to the progress of the equilibrium reaction after neutralization, and this is considered to act as a dopant for the polythiophene compound.

  In the case of using polythiophene and / or polythiophene derivative in the present invention, it is more conductive that polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative is excessively present at a solid content weight ratio with respect to polythiophene and / or polythiophene derivative. In view of the above, the polythiophene and / or the polythiophene derivative is preferably 1 part by weight to 5 parts by weight, more preferably 1 part by weight to 3 parts by weight with respect to 1 part by weight of the polythiophene and / or polythiophene derivative. is there.

  Further, compositions comprising the above polythiophene and / or polythiophene derivatives and polystyrene sulfonic acid and / or polystyrene sulfonic acid derivatives are disclosed in, for example, JP-A-6-295016, JP-A-7-292081, and JP-A-1-135521. Although it can be produced by the methods described in Japanese Patent Laid-Open No. 2000-6324, European Patent EP 602731, and US Pat. No. 5,391,472, other methods may be used.

  For example, 3,4-ethylenedioxythiophene was obtained using an alkali metal salt of 3,4-dihydroxythiophene-2,5-dicarboxyester as a starting material, and potassium peroxodisulfate was added to a polystyrenesulfonic acid aqueous solution. And iron sulfate and 3,4-ethylenedioxythiophene obtained above are introduced and reacted to form a polythiophene such as poly (3,4-ethylenedioxythiophene) and a complex of polystyrene sulfonic acid and the like To obtain a composition.

  The antistatic treatment layer in the present invention preferably contains a composition comprising the above polythiophene and / or polythiophene derivative and polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative, and a crosslinking agent. As the crosslinking agent, for example, a melamine crosslinking agent, an epoxy crosslinking agent, an oxazoline crosslinking agent, an isocyanate crosslinking agent, and an acrylamide crosslinking agent can be used. The crosslinking agent is preferably a crosslinking agent having a molecular weight of 1000 or less, more preferably 800 or less, and still more preferably 600 or less. In particular, by using a water-soluble cross-linking agent having a molecular weight of 1000 or less, flexibility and fluidity in the stretching process are expressed, and the stretchable followability after drying of the mixture forming the laminated film is improved, and the coating film is cracked. The whitening phenomenon is suppressed and transparency is imparted. When the molecular weight is too large, the coating film is cracked during stretching after coating and drying, so that the transparency tends to decrease. The temperature at which the thermal loss rate of the epoxy-based crosslinking agent is 5% is preferably 230 ° C. or higher, more preferably 250 ° C. or higher, and particularly preferably 270 ° C. or higher. When the temperature at which the heat loss rate is 5% is less than 230 ° C., the epoxy component may be dispersed in the polyester film production process, particularly in the transverse stretching to heat treatment oven, thereby fouling the process.

  As the crosslinking agent, an epoxy-based crosslinking agent, particularly a water-soluble epoxy-based crosslinking agent is particularly preferable, and an antistatic layer excellent in transparency, antistatic property and coating film appearance can be formed. The type of the epoxy-based crosslinking agent is not particularly limited, and examples thereof include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether. Can be used. For example, an epoxy compound “Denacol” (registered trademark) manufactured by Nagase Chemtech Co., Ltd. (EX-611, EX-614, EX-512, EX-521, EX-412, EX-313, EX-810, EX-830, EX-850, etc.), diepoxy / polyepoxy compounds (SR-EG, SR-8EG, SR-GLG, etc.) manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., and epoxy crosslinking agent “EPICLON” manufactured by Dainippon Ink Industries, Ltd. ) EM-85-75W or CR-5L can be used preferably.

  The mixing ratio of the solid content of the composition comprising the polythiophene and / or polythiophene derivative and polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative to the solid content of the cross-linking agent is as follows: polythiophene and / or polythiophene derivative and polystyrene sulfonic acid and / or When the sum of the solid content of the composition comprising a polystyrene sulfonic acid derivative and the solid content of the crosslinking agent is 100 parts by weight, the solid content of the crosslinking agent is preferably 30 parts by weight to 90 parts by weight, more preferably 50 parts by weight to 85 parts by weight. When the solid content of the crosslinking agent is more than 90 parts by weight, the antistatic property is hardly exhibited. On the other hand, when the solid content of the crosslinking agent is less than 30 parts by weight, cracks are likely to occur in the antistatic layer, resulting in inferior transparency and difficulty in developing antistatic properties.

In the biaxially stretched polyester film for in-mold molding in the present invention, the amount of oligomer deposited on the non-transfer surface after heat treatment at 180 ° C. for 30 minutes is preferably 3.0 mg / m ² or less, more preferably 2.0 mg / m. ² or less, most preferably 1.0 mg / m ² or less. If the amount of oligomer precipitation on the non-transfer surface after heat treatment at 180 ° C. for 30 minutes exceeds 3.0 mg / m ² , the amount of oligomer adhering to the mold on the non-transfer surface side during molding increases, It is not preferable because it becomes a defect or the frequency of cleaning the mold increases and the production efficiency decreases. The lower limit of the oligomer precipitation amount is not particularly limited, but is preferably 0.4 mg / m ² or more from the viewpoint of production cost and film formation stability.

  In the present invention, the oligomer precipitation amount means that the polyester film is heat-treated in an oven at 180 ° C. for 30 minutes, the non-transfer surface of the polyester film is immersed in a dimethylformamide solvent for 3 minutes, and a polyethylene terephthalate cyclic oligomer (trimer purity) 89%) The amount of cyclic trimer obtained by measurement with high performance liquid chromatography (HPLC) using a standard solution. Measurement conditions will be described later.

  Moreover, it is although it does not specifically limit as a method of suppressing an oligomer precipitation amount, It is preferable to have a coating film layer containing a water-dispersible acrylic resin. This is because oligomer precipitation is easily blocked by the difference in surface energy between the acrylic resin coating layer and the film. Examples of the water-dispersible acrylic resin include acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylolacrylamide, N-butoxyacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, and 12 to 25 carbon atoms. Examples include, but are not limited to, copolymers of monomers such as alkyl acrylate having an alkyl group in the side chain. In these water-dispersed acrylic resins, the average emulsion particle size is preferably 50 to 200 nm, and it is preferable to use one having a distribution as uniform as possible. In order to impart higher oligomer precipitation preventing properties, it is preferable to add a component having an oligomer precipitation preventing function to the coating layer. Examples of the component having an oligomer precipitation preventing function include, but are not limited to, a long-chain alkyl acrylate, a fluorine acrylate, a silicone compound, and a polyolefin compound. Since these components have a larger surface energy difference from the film than the water-dispersed acrylic resin, higher oligomer precipitation preventing properties can be obtained.

  In this invention, it is preferable to have the easily bonding layer formed of the coating layer containing a polyester resin in the transfer surface. The film for in-mold molding expresses the function by laminating an easy adhesion layer, a release layer, a printing layer, etc. sequentially on the transfer surface side in the process, but the easy adhesion layer is formed in the film forming process of the base polyester film. Lamination is a preferable aspect from the viewpoint of manufacturing cost and processing time because the step of providing an easy-adhesion layer in the processing step can be omitted.

  As a method for imparting an easy-adhesion layer to the transfer surface, there are a method of kneading into an outer layer as a multilayer structure, a method of coating offline after film formation, etc., but an easy-adhesion layer is used to prevent environmental contamination during film production. From the viewpoint of explosion-proof property, production cost, etc., it is preferably a coating layer formed by being stretched in at least one direction after applying an aqueous coating liquid, and is formed within a production process in which a base polyester film is biaxially oriented. More preferably. Although the timing of the stretching is not particularly limited, a method of biaxial stretching after applying an aqueous coating liquid, or a method of applying an aqueous coating liquid after longitudinal stretching and further lateral stretching is preferably used. As a coating method of the aqueous coating liquid, various coating methods such as reverse coating method, gravure coating method, rod coating method, bar coating method, die coating method and spray coating method can be preferably used. It is not limited.

  10-2000 nm is preferable and, as for the thickness of an easily bonding layer, More preferably, it is 50-1000 nm. If the thickness of the easy-adhesion layer is too thin, adhesion to the release layer and solvent resistance may be insufficient, and if it is too thick, the slip resistance and blocking resistance when used as a film roll will deteriorate. There is a case.

  Moreover, it is preferable that an easily bonding layer contains a polyester resin. When a polyester resin is used for the easy-adhesion layer, interfacial peeling and scraping are less likely to occur because of its high affinity with the base polyester film, and the coating appearance is improved in the case of aqueous coating. Moreover, it is preferable that it is a polyester resin also from a viewpoint of manufacturing cost or the adhesive force with a mold release layer.

  In order to apply as an aqueous coating liquid, the polyester contained in the easy-adhesion layer is preferably a copolymerized polyester containing a compound containing a sulfonate group or a compound containing a carboxylate group as a copolymerization component. Examples of the compound containing a sulfonate group include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and alkali metal salts and alkaline earth metals thereof. Salts and ammonium salts can be used, but are not limited thereto. Examples of the compound containing a carboxylate group include trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 4-methylcyclohexene-1,2,3-tricarboxylic acid, trimesic acid, 1,2, 3,4-butanetetracarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3-cyclohexene-1,2-dicarboxylic acid, cyclopentanetetracarboxylic acid, 2,3,6,7-naphthalenetetra Carboxylic acid, 1,2,5,6-naphthalene tetracarboxylic acid, ethylene glycol bistrimellitate, 2,2 ', 3,3'-diphenyltetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid , Ethylenetetracarboxylic acid, etc., or alkali metal salts thereof, alkaline earth metal salts and ammonia And the like can be used unsalted, but is not limited thereto.

  The polyester contained in the easy-adhesion layer is preferably a copolymerized polyester containing diethylene glycol as a copolymerization component. By making this component into a copolymerization component, the solvent resistance of the easy-adhesion layer especially with respect to alcohol can be improved, and the affinity with the base polyester film can be improved. As other copolymerization components, known dicarboxylic acids and diols can be used. Examples thereof include, but are not limited to, the dicarboxylic acids and diols described above. Moreover, the compound containing an above described sulfonate group and the compound containing a carboxylate group can also be included as a copolymerization component. The range of the preferable glass transition point of this copolyester is 0-60 degreeC, More preferably, it is 10-45 degreeC.

  The content of the copolymerized polyester containing diethylene glycol as a copolymerization component is preferably 10 to 60% by weight, more preferably 20 to 50% by weight, based on the total amount of resins forming the easy-adhesion layer. If the content is too small, the solvent resistance and the adhesive strength with the base polyester film may be inferior. If the content is too large, the blocking resistance may be inferior when used as a film roll.

  The resin other than the copolyester having a copolymer component of diethylene glycol that forms the easy-adhesion layer is not particularly limited as long as the effects of the present invention are not impaired, but other polyester resins, acrylic resins, A urethane resin, an epoxy resin, a silicone resin, a urea resin, a phenol resin, and the like can be exemplified. Among them, other polyester resins can be preferably exemplified.

  Further, in the easy-adhesion layer in the present invention, for example, an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic lubricant, a pigment, and a dye are within the range where the effects of the present invention are not impaired. Organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, and the like may be blended.

  The transfer foil for in-mold molding using the biaxially stretched polyester film for in-mold molding of the present invention may be in any form as long as it is a transfer foil used for in-mold molding. It is preferable that the transfer foil has a release layer, a protective layer, a printing layer, a vapor deposition layer, and an adhesive layer on top, and is suitably used for decorating plastic parts such as mobile phones, automobile parts, and home appliances. In this case, it is more preferable that the release layer is formed of a melamine resin component and the protective layer is formed of an acrylic resin component having hard coat properties.

  The polyester film constituting the biaxially stretched polyester film for in-mold molding of the present invention needs to be a biaxially oriented film. A biaxially oriented polyester film is formed by stretching an unstretched polyester sheet or film in the MD and TD directions in a so-called biaxial direction, and is a pattern of biaxial orientation by wide-angle X-ray diffraction. Is shown. By biaxial stretching, mechanical strength, dimensional stability, chemical resistance, etc., which are difficult with an unstretched film, can be expressed. The biaxial stretching method may be either the sequential biaxial stretching method or the simultaneous biaxial stretching method. However, in the case of simultaneous biaxial stretching, the smooth film surface is hardly scratched, and the on-line coating is performed at a low speed. There are advantages such as being able to.

[Characteristic measurement method and effect evaluation method]
The characteristic measurement method and effect evaluation method in the present invention are as follows.

(1) root mean square roughness RMS
Using a non-contact optical interference type three-dimensional surface roughness meter (manufactured by ZYGO, New View 200), arbitrary five points were measured under the following conditions, and the average value was obtained.
・ Number of pixels 320 × 240 pixels ・ Scanning speed 2 μm / second ・ Magnification 20 times ・ Measurement area 0.352 mm × 0.264 mm
・ Correction Cylinder correction ・ Cutoff wavelength 0.44mm, 4.4μm
-Filter trimming ON
・ Filter type FFT FIXED
・ Filter Band Reject
-FDA Res High.

(2) Plane orientation coefficient fn
The measurement was performed using the transfer surface. The transfer surface of the sample was wiped with ethanol and acetone in advance to remove the easy-adhesion coating layer. The apparatus uses an Abbe refractometer NAR-4T (manufactured by Atago Co., Ltd.), a sodium D line (wavelength 589 nm) as a light source, and methylene iodide as a mount solution, and refractive indexes in the MD, TD, and thickness directions. (Respectively nx, ny, nz) were obtained. The surface distribution coefficient fn was obtained by calculating fn = (nx + ny) / 2−nz.

(3) Elongation at break Using a tensile tester (TENSILON / UTM-4-100 manufactured by TOYO BALDWIN CO. LTD), the elongation at break S _MD in the MD direction with a tensile speed of 300 mm / min, a width of 10 mm, and a test length of 100 mm, TD direction of the elongation at break _{S TD} was measured, respectively. The average value S of the elongation at break in the MD direction and the TD direction of the film was determined as S = (S _MD + S _TD ) / 2.

(4) Thermal shrinkage rate JIS-C2151 (1990) 16. Measured based on dimensional change.

(5) Surface specific resistance After leaving a film sample under measurement conditions (temperature 25 ° C., relative humidity 65%) for 24 hours, a digital ultrahigh resistance / microammeter R8340A (manufactured by Advantest Co., Ltd.) was used under the atmosphere. Measurement was performed after applying for 10 seconds at an applied voltage of 100V.

(6) Determination of oligomer precipitation amount The polyester film was heat-treated in an oven at 180 ° C. for 30 minutes. Thereafter, with the non-transfer surface facing outside, a film was affixed to a 50 mm × 50 mm surface of a 50 mm × 50 mm × 30 mm cuboid aluminum jig, and the end was bent and fixed along the jig. The jig was immersed in a dimethylformamide solvent for 3 minutes with the film side down to a depth of 5 mm to extract surface precipitated oligomers.

  Next, as a standard solution, 11.2 mg of a polyethylene terephthalate cyclic oligomer (trimer purity 89%) was placed in a 100 mL volumetric flask and mixed with 1,1,1,3,3,3-hexafluoro-2-propanol / chloroform solvent. (= 1/1) After dissolving in 2 mL, the standard stock solution (trimer concentration 100 μg / mL) was diluted to 100 mL with chloroform. This solution was sequentially diluted with dimethylformamide to prepare standard solutions having trimer concentrations of 10 μg / mL, 1 μg / mL, and 0.1 μg / mL.

The surface oligomer extraction solvent and the standard solution were analyzed by high performance liquid chromatography (HPLC) under the following conditions, the amount of cyclic trimer was measured, and the amount of oligomer precipitation was determined.
Equipment: Shimadzu LC-10A
Column: Inertsil ODS-3
Mobile phase: acetonitrile / water = 70/30
Flow rate: 1.5 mL / min Detector: UV 242 nm
Injection volume: 10 μL.

(7) Handleability, glossiness of molded product surface, processability, moldability, transfer accuracy, mold stains Gravure coating method using a mixture of butylated urea melamine resin and paratoluenesulfonic acid on the transfer surface side of the polyester film And then cured at a temperature of 80 ° C. to form a release layer. Next, a release layer is formed on the release layer by gravure coating using an acrylic resin, and a metallic layer (containing 20% aluminum pigment) with vinyl resin ink is used as a pattern layer on the release layer. A black character pattern (containing 15% carbon black) is formed by gravure printing, then washed with hot water at 40 ° C. and dried, and finally an acrylic resin adhesive layer is formed by a gravure coating method to obtain a transfer material. It was.

  The obtained transfer material is vacuum-molded in a mold at a mold temperature of 220 ° C. in a mold of 50 mm × 50 mm and a maximum depth of 8 mm in an atmosphere of a temperature of 25 ° C. and a relative humidity of 30%, and then clamped. Thereafter, simultaneous molding and transfer processing was performed under an injection pressure condition of 25 MPa using acrylic resin as a molding resin.

(A) Handling property Frequency at which winding defects such as winding misalignment and defective winding appearance occur at a winding length of 10,000 m in each winding process from the start of processing a polyester film to obtaining a transfer material by the method described above. Was measured, and the handling property was judged according to the following criteria. Less than 3 times pass.

(B) Glossiness of surface of molded product The surface glossiness of 60 ° reflection in Japanese Industrial Standard (JIS) Z-8741 (2004) was measured for the obtained molded product. When the surface glossiness of the molded product was GF and the surface glossiness of the standard metal sample was GM, the following judgment was followed. Δ or more is acceptable.

○ GF ≧ GM
△ GM-20 ≦ GF <GM
X GF <GM-20.

(C) Workability The workability was determined according to the following judgment. Δ or more is acceptable.

  ○ The percentage of defective products due to dust adhesion, whiskers, etc. is less than 0.1%.

  △ The percentage of defective products due to dust adhesion, whiskers, etc. is less than 1%.

  × The percentage of defective products due to dust adhesion, whiskers, etc. is 1% or more.

(D) Formability The formability was determined according to the following judgment. Δ or more is acceptable.

○ Film breakage during vacuum forming is less than 0.1% Δ Film breakage during vacuum forming is less than 1% × Film breakage during vacuum forming is 1% or more.

(E) Transfer accuracy The transfer accuracy was determined according to the following judgment. Δ or more is acceptable.

○ Deformation due to distortion and misalignment after molding transfer is less than 0.1% △ Defect due to misalignment and pattern after molding transfer is less than 1% × Defect due to distortion and misalignment after molding transfer is 1% or more .

(F) Mold Dirt Mold dirt was determined based on the following criteria by comparing the standard sample with the film described in Comparative Example 1 having no antistatic layer on the non-transfer surface.

○ The number of transfers until the mold begins to become dirty is 5 times or more of the standard sample. △ The number of transfers until the mold starts to become dirty is 3 to 5 times the standard sample. × The number of transfers until the mold starts to become dirty is the standard sample. Less than 3 times.

(8) Adhesion between easy-adhesion layer and release layer A mixture of butylated urea melamine resin and para-toluenesulfonic acid is applied to the transfer surface (easily-adhesive surface) side of the polyester film by gravure coating, and the temperature is increased to 80 ° C The release layer was formed and air-dried at room temperature for 1 day. The sample was cut into a grid with a cutter knife, and a cellophane tape was applied, 90 ° positive peeling was performed, the peeling state was evaluated in three stages, and the following judgment was followed. Δ or more is acceptable.

  ○ A release layer of 75% or more remains.

  Δ 50% or more and less than 75% release layer remains.

  X A release layer remains less than 50%.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

Example 1
Using the extruder (A), the extruder (B), the extruder (C), and a composite film-forming apparatus having a T-die composite die, a three-layer laminated polyester film comprising the following A layer, B layer, and C layer; did. The laminated structure is A / C / B.

First, the resin forming the A layer will be described. A slurry of 45 kg of ethylene glycol per 100 kg of high-purity terephthalic acid was charged in an esterification reaction tank in which about 123 kg of bis (hydroxyethyl) terephthalate was previously charged and maintained at a temperature of 250 ° C. and a pressure of 1.2 × 10 ⁵ Pa for 4 hours. The esterification reaction was carried out over an additional hour after the supply was completed, and the esterification reaction product was transferred to a polycondensation tank. Subsequently, 0.01 parts by weight of ethyl diethylphosphonoacetate was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, and 0.04 parts by weight of magnesium acetate tetrahydrate was further added as a polymerization catalyst. Antimony trioxide (manufactured by Sumitomo Metal Mining Co., Ltd.) was added to the obtained polyester so as to be 400 ppm in terms of antimony atoms. Furthermore, as an additive, calcium carbonate having an average particle size of 0.3 μm was added so as to be 0.1% by weight with respect to the polyester. Thereafter, while stirring the low polymer at 30 rpm, the reaction system was heated from 250 ° C. to 285 ° C. over 60 minutes and the pressure was reduced to 40 Pa. The time to reach the final pressure was 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen, returned to normal pressure, the polycondensation reaction was stopped, discharged into cold water at a temperature of 20 ° C. in a strand, and immediately cut to obtain polyester pellets. . The time from the start of decompression to the arrival of the predetermined stirring torque was 3 hours.

Next, the resin forming the B layer will be described. A slurry of 45 kg of ethylene glycol per 100 kg of high-purity terephthalic acid was charged in an esterification reaction tank in which about 123 kg of bis (hydroxyethyl) terephthalate was previously charged and maintained at a temperature of 250 ° C. and a pressure of 1.2 × 10 ⁵ Pa for 4 hours. The esterification reaction was carried out over an additional hour after the supply was completed, and the esterification reaction product was transferred to a polycondensation tank. Subsequently, 0.01 parts by weight of ethyl diethylphosphonoacetate was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, and 0.04 parts by weight of magnesium acetate tetrahydrate was further added as a polymerization catalyst. Antimony trioxide (manufactured by Sumitomo Metal Mining Co., Ltd.) was added to the obtained polyester so as to be 400 ppm in terms of antimony atoms. Further, as an additive, silicon dioxide having an average particle diameter of 2.1 μm was added so as to be 0.10% by weight with respect to the polyester. Thereafter, while stirring the low polymer at 30 rpm, the reaction system was heated from 250 ° C. to 285 ° C. over 60 minutes and the pressure was reduced to 40 Pa. The time to reach the final pressure was 60 minutes. When the predetermined stirring torque was reached, the reaction system was purged with nitrogen, returned to normal pressure, the polycondensation reaction was stopped, discharged into cold water at a temperature of 20 ° C. in a strand, and immediately cut to obtain polyester pellets. . The time from the start of decompression to the arrival of the predetermined stirring torque was 3 hours.

  Next, the resin forming the C layer will be described. For layer C, the recovered raw material recovered by recovering the film-forming edge portion, the core portion, and the like generated during film formation was used. The film forming edge part, the core part, and the like generated in the process of forming the raw material of the B layer as a single film were pulverized into several mm square by a crusher. The pulverized film piece was pressed and heated using a granulator and pelletized to obtain a cylindrical regenerated pellet having a length of 15 mm and a diameter of 6 mm.

  These polyester pellets forming the A layer, the B layer, and the C layer are each vacuum dried to a moisture content of 20 ppm, and then supplied to the extruder (A), the extruder (B), and the extruder (C), respectively. Were melted at 280 ° C., filtered through an 8 μm cut stainless steel fiber sintered filter (FSS), and then introduced into a T-die composite die. After merging to form an A / C / B layer structure in the die, it was coextruded into a sheet and cooled and solidified by an electrostatic contact method using a cooling drum having a surface temperature of 25 ° C. . The unstretched polyester film thus obtained was heated to a temperature of 114 ° C. and then longitudinally stretched 3.2 times in the MD direction at a temperature of 108 ° C. to obtain a uniaxially stretched film. Both surfaces of this uniaxially stretched film are subjected to corona discharge treatment in the air to a surface tension of 50 mN / m or more, and an easy-adhesion layer coating solution having the following composition is applied to the A layer (transfer surface) side, and then the B layer An antistatic layer coating solution having the following composition was applied to the (non-transfer surface side) side.

<Easily adhesive layer coating solution>
A polyester-based easy-adhesion coating liquid α1 was prepared by the following method. A copolymer polyester resin (glass transition) comprising 70 mol% terephthalic acid as an acid component, 23 mol% isophthalic acid and 7 mol% 5-sodiumsulfoisophthalic acid, and 70 mol% ethylene glycol and 30 mol% diethylene glycol as diol components (A point: 55 ° C.) and an aqueous solution prepared by mixing “Bekkamin” (registered trademark) APM manufactured by Dainippon Ink & Chemicals, Inc. as a melamine cross-linking agent to a solid content ratio of 95: 5. It was said.

<Antistatic layer coating solution>
An aqueous solution in which the following antistatic layer coating liquid A1, antistatic layer coating liquid B1 and antistatic layer coating liquid C1 were mixed at an active ingredient ratio of 20 parts by weight / 80 parts by weight / 20 parts by weight was used.
・ Antistatic coating liquid A1
An aqueous coating solution (“Denatron” (R) 5002RZ, manufactured by Nagase ChemteX Corporation) in which a composite of polyethylene dioxythiophene / polystyrene sulfonic acid and a polyester resin were dispersed in water was used.
・ Antistatic layer coating solution B1
An aqueous solution in which a polyglycerol polyglycidyl ether type epoxy crosslinking agent (“Denacol” (R) EX-512 manufactured by Nagase ChemteX Corporation) was dissolved in water was used.
・ Antistatic layer coating liquid C1
An aqueous solution in which a long-chain alkyl acrylate having the following copolymer composition was dissolved in water containing 10% by weight of isopropyl alcohol and 5% by weight of butyl cellosolve was used.

(Copolymerization component)
Methacrylic acid 40 parts by weight Stearyl methacrylate 60 parts by weight N-methylol acrylamide 2 parts by weight Anionic reactive emulsifier 2 parts by weight Anionic reactive emulsifier includes “Eleminol” (registered trademark) JS-2 (Sanyo Chemical Industries ( Product).

  While holding both ends of the uniaxially stretched laminated polyester film applied to both sides with clips, the tenter is led to a preheating zone at a temperature of 110 ° C. in the tenter, and continuously at a heating zone at a temperature of 115 ° C. perpendicular to the MD direction. The film was stretched 3.2 times in the direction (TD direction). Subsequently, a heat treatment at a temperature of 228 ° C. is performed in a heat treatment zone in the tenter, and further a relaxation treatment is performed in a 2.4% TD direction at a temperature of 213 ° C., and then 2.6% TD at a temperature of 170 ° C. 3 layers of A layer / C layer / B layer with thicknesses of 4/30/4 (μm) respectively. A biaxially stretched polyester film for in-mold molding having a total thickness of 38 μm and a width of 4.2 m was obtained. The results are shown in the table. As shown in Tables 2 and 3, good workability, handling property, gloss of the surface of the molded product, moldability, transfer accuracy, and mold soiling were shown.

(Examples 2 to 4)
The following antistatic layer coating solution and easy adhesion layer coating solution were used. In other respects, a biaxially stretched polyester film for in-mold molding was obtained according to Example 1 except that the conditions shown in Tables 1, 2, and 3 were used.
・ Antistatic coating solution D1
An aqueous dispersion in which particles of an acrylic resin (glass transition point 40 ° C.) having the following copolymer composition were dispersed in water was used.
(Copolymerization component)
Methyl methacrylate 65 mol%
Ethyl acrylate 35 mol%
Acrylic acid 1 mol%
N-methylolacrylamide 2 mol%
・ Antistatic coating liquid E1
An aqueous solution in which polystyrene sulfonate ammonium salt (weight average molecular weight: 10,000) was dissolved in water was used.
-Easy adhesive layer coating liquid α2
A polyester-based easy-adhesion coating liquid α2 was prepared by the following method. (1) fluorinated surfactant, (2) copolymer polyester (glass) having a copolymer composition of terephthalic acid / 5-sodium sulfoisophthalic acid // ethylene glycol (molar ratio 87.5 / 12.5 // 100) (Transition point 40 ° C.), (3) copolymer polyester having a copolymer composition of isophthalic acid / 5-sodium sulfoisophthalic acid // ethylene glycol / diethylene glycol (molar ratio 93/7 // 10/90) (glass transition point 18 (2) / (3) is mixed to a solid content weight ratio of 70/30, diluted with water to a solid content concentration of 4% by weight, and (1) is applied. An aqueous coating solution added at 0.0003% by weight with respect to the whole solution was used.

  In Examples 2 to 4, a T-die composite die was used to form a two-layer laminated polyester film. Moreover, in Example 2, the polyester pellet which added the titanium element so that it might become 5 ppm with respect to the polyester from which the ethylene glycol solution of the citrate chelate titanium compound prepared as follows was used as a polymerization catalyst was used. The resulting polyester pellets had an intrinsic viscosity of 0.63 dl / g, a carboxyl end group content of 42 equivalents / ton, a glass transition temperature (Tg) of 78 ° C., and a cyclic trimer content of 1.1% by weight.

(Method for synthesizing citric acid chelate titanium compound)
In a 1 L flask equipped with a stirrer, a condenser, and a thermometer, 132.5 g (0.63 mol) of citric acid monohydrate was dissolved per 92.8 g of hot water. To this stirred solution, 72.0 g (0.25 mol) of titanium tetraisopropoxide was added from a dropping funnel. The mixture was heated to reflux for 1 hour to produce a cloudy solution from which the isopropanol / water mixture was distilled under vacuum. The product was cooled to a temperature of 20 ° C. and to the stirred solution was added 94.86 g (0.76 mol) NaOH 32 wt / wt% aqueous solution via a dropping funnel. The resulting product was filtered and then mixed with 125.54 g (2 mol) of ethylene glycol and heated under vacuum to remove isopropanol / water to give a slightly cloudy, pale yellow product (Ti content 3.85% by weight) was obtained.

  In Example 4, a film was formed using the simultaneous biaxial stretching method, and a copolymerized polyester obtained by copolymerizing 17.5% by weight of isophthalic acid was used as a polyester raw material. The results are shown in Table 1, Table 2, and Table 3. As is clear from the table, the following results were obtained.

  Example 2: Since a titanium-based polymerization catalyst was used, there was little internal foreign matter and the appearance was good. Since the transfer surface and the non-transfer surface were rough, the handling property was good. The glossiness was slightly inferior, but was at a usable level. Although the elongation at break was slightly low, the moldability was slightly inferior, but it was at a usable level. Workability was slightly inferior due to high surface resistivity, but it was at a usable level.

  Example 3: Since the RMS of the non-transfer surface was low, the handling property was slightly inferior, but it was at a usable level. Further, since the heat shrinkage rate was the upper limit, the transfer accuracy was slightly inferior, but was at a usable level. Moreover, although the oligomer precipitation amount was slightly high and the mold contamination was somewhat large, it was at a usable level.

  Example 4: Since the film was formed using the simultaneous biaxial stretching method, scratches due to the roll were reduced, and the appearance was good. In addition, since a copolyester was used, moldability that could improve the plane orientation coefficient and the elongation at break was obtained. Since the RMS of the transfer surface was small, the handling property was slightly inferior, but it was a level with no practical problem.

(Comparative Examples 1-5)
A biaxially stretched film for in-mold molding was obtained according to Example 1 except that the following antistatic layer coating solution and easy-adhesion layer coating solution were used, and the conditions shown in Tables 1 and 2 were used. .
・ Antistatic coating liquid F1
Polydiallyldimethylammonium chloride (average molecular weight: about 30000) was used.
・ Antistatic layer coating liquid G1
A melamine cross-linking agent, “Beccamin” (registered trademark) J101, manufactured by Dainippon Ink & Chemicals, Inc. was used.
・ Antistatic layer coating liquid C2
An aqueous solution in which a long-chain alkyl acrylate having the following copolymer composition was dissolved in water containing 10% by weight of isopropyl alcohol and 5% by weight of butyl cellosolve was used.

(Copolymerization component)
Methacrylic acid 40 parts by weight Behenyl methacrylate 60 parts by weight N-methylol acrylamide 2 parts by weight Anionic reactive emulsifier 2 parts by weight Anionic reactive emulsifier is “ELEMINOL” (registered trademark) JS-2 (Sanyo Chemical Industries, Ltd.) Made).
・ Easily adhesive layer coating solution β1
An acrylic easy-adhesion coating solution β1 was prepared by the following method. An aqueous solution in which the modified acrylic emulsion resin and the oxazoline crosslinking agent “Epocross WS500” (registered trademark) (manufactured by Nippon Shokubai Co., Ltd.) were mixed at an active ingredient ratio of 100 parts by weight / 10 parts by weight was used.
・ Easily adhesive layer coating solution β2
A polyurethane-based easy-adhesive coating solution β2 was prepared by the following method. A coating agent obtained by adding 6 parts by weight of a melamine-based crosslinking agent to 100 parts by weight of a self-emulsifiable polyurethane polyurea resin was used.

  In Comparative Examples 1 and 2, a single layer T die die was used to form a single film. In Comparative Example 5, the same copolymerized polyester as in Example 4 was used. The results are shown in Tables 1 and 2. As is clear from the table, the following results were obtained.

  Comparative Example 1: Although the glossiness of the surface of the molded article was good because the film was formed only with a layer having a smooth surface, the desired effect was obtained because the surface orientation coefficient, elongation at break, antistatic property and oligomer precipitation preventing property were inferior. It was not obtained.

  Comparative Example 2: Since the film was formed only with the layer having a rough surface, the glossiness of the surface of the molded product was inferior although the handling property was good. Further, since the surface orientation coefficient, elongation at break, antistatic property, and oligomer precipitation preventing property were inferior, desired effects could not be obtained. Moreover, since the total thickness was a little as 10 μm, troubles such as wrinkles occurred during molding.

  Comparative Example 3: Although the transfer surface was rough, the handling property was good, but the glossiness of the surface of the molded product was inferior. Further, the antistatic property was inferior and the workability was not achieved. Further, since there was no easy-adhesion layer, the adhesion with the release layer was very weak.

  Comparative Example 4: Since the non-transfer surface was smooth, the handling property was inferior. Moreover, the thermal shrinkage rate was large, and the transfer accuracy was not achieved. Moreover, since the easily bonding layer was an acrylic layer, it was inferior in adhesiveness with a mold release layer.

  Comparative Example 5: The non-transfer surface was very rough, and the roughness affected the transfer surface, resulting in a rough transfer surface. Moreover, the plane orientation coefficient was large, and the film-forming stability was inferior and tearing occurred. Moreover, the thermal shrinkage rate was large, and the transfer accuracy was not achieved. Moreover, since the total thickness was a little as 250 μm, the processing in the roll state was somewhat difficult.

  The biaxially stretched polyester film for in-mold molding of the present invention is excellent in handling property, moldability, charging, etc., particularly in in-mold molding applications for mobile phone parts that require high designability and high moldability. Prevention property, easy adhesion property, oligomer precipitation prevention property, and surface smoothness can improve problems in each process, and can significantly improve productivity and product quality, and are useful.

Claims (9)

Biaxial stretching for transfer foil having at least two polyester film layers, wherein the root mean square roughness RMS of the transfer surface is less than 7 nm and the root mean square roughness RMS of the non-transfer surface is 10 nm or more and 51.3 nm or less. It is a polyester film, and at least the plane orientation coefficient of the transfer surface is 0.15 or less, the average value of the elongation at break in the MD direction and the TD direction of the film is 180% or more,
The thermal shrinkage in the TD direction of the film when heated at 150 ° C. for 30 minutes is 0.8% or less,
Further possess an antistatic layer satisfying the requirements of the following to the non-transfer surface (1) and (2), the root-mean-square roughness RMS is for Der Ru-mold molding transfer foil those obtained by the following method Biaxially stretched polyester film.
(1) Antistatic layer formed by a coating layer containing polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative (2) Surface specific resistance of antistatic layer surface is 1 × 10 ¹³ Ω / □ or less
[Measuring method of root mean square roughness RMS]
Using a non-contact optical interference type three-dimensional surface roughness meter (manufactured by ZYGO, New View 200), any five points are measured under the following conditions, and the average value is obtained.
・ Number of pixels 320 × 240 pixels
・ Scanning speed 2μm / sec
・ Magnification 20 times
・ Measurement area 0.352mm × 0.264mm
・ Cylinder correction
・ Cutoff wavelength 0.44mm, 4.4μm
-Filter trimming ON
・ Filter type FFT FIXED
・ Filter Band Reject
-FDA Res High. The biaxially stretched polyester film for in-mold molding according to claim 1, wherein the antistatic layer contains polythiophene and / or a polythiophene derivative, and the surface specific resistance of the surface of the antistatic layer is 1 × 10 ¹⁰ Ω / □ or less. The biaxially stretched polyester film for in-mold molding according to claim 1 or 2, wherein the transfer surface has an easy adhesion layer formed by a coating layer containing a polyester resin. The biaxially stretched polyester film for in-mold molding according to any one of claims 1 to 3, wherein an oligomer precipitation amount on the non-transfer surface after heat treatment at 180 ° C for 30 minutes is 3.0 mg / m ² or less. The biaxially stretched polyester film for in-mold molding according to any one of claims 1 to 5, wherein an average value of breaking elongation in the MD direction and TD direction of the film is 200% or more. The biaxially stretched polyester film for in-mold molding according to any one of claims 1 to 5 , wherein the heat shrinkage rate in the TD direction of the film when heated at 150 ° C for 30 minutes is 0.5% or less. The biaxially stretched polyester film for in-mold molding according to any one of claims 1 to 6 , wherein a titanium-based compound is used as a polymerization catalyst for the polyester constituting the polyester film. The biaxially stretched polyester film for in-mold molding according to any one of claims 1 to 7 , wherein the polyester film is a simultaneous biaxially stretched film. The transfer foil for in-mold shaping | molding using the biaxially stretched polyester film for in-mold shaping | molding in any one of Claims 1-8 .