JP2008246753A - Biaxially oriented polyester film for in-molding transfer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film for in-mold transfer which suppresses the occurrence of mold rust and is capable of minute printing. <P>SOLUTION: The biaxially oriented polyester film is obtained by a coextrusion method and contains an antistatic agent in an amount of 0.1-10 wt.% of a polyester which is contained in a layer composing at least one side of the film and composes the layer. The birefringent index (Δn) of the film is 0.040 or below. A coating layer is formed on at least one side of the film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a biaxially stretched polyester film for simultaneous molding and transfer that is useful as a support film for a simultaneously molded decorative sheet used for decorating resin molded products such as electric products and automobile parts.

  As a method for decorating a plastic molded product having a curved surface such as an electric appliance, a so-called in-mold molding method in which transfer printing is performed simultaneously with molding is widely used. The in-mold molding method uses a heat and pressure during plastic injection molding to create a transfer sheet in which a printing layer consisting of a release layer, ink layer, adhesive layer, etc. is laminated on a substrate film in advance. Transfer printing.

  If the support film of the transfer sheet is charged with static electricity, troubles such as beards in the pattern in the printing process and adhesion of dust in the process of manufacturing the transfer sheet will cause a problem of poor quality in the molded product.

Conventionally, in order to suppress static electricity of the support film, for example, a coating agent containing a cationic polymer as described in Patent Document 1 has been applied to the film surface. There is a problem that the quality of the molded product is deteriorated due to the occurrence of spot-like rust on the mold that can be in contact with the mold. The cause of the occurrence of rust is not always clear, but it is highly likely that the cause is a halogen element contained in the antistatic agent to be blended in order to give the coating layer an antistatic function.
JP 2006-187951 A

  This invention is made | formed in view of the said actual condition, The solution subject is suppressing generation | occurrence | production of mold rust and providing the biaxially stretched polyester film for shaping | molding simultaneous transfer which can perform fine printing.

  As a result of intensive studies, the present inventors have found that the above problem can be easily solved by using a polyester film having a specific configuration, and have completed the present invention.

  That is, the gist of the present invention is a laminated film obtained by a co-extrusion method, and at least 0.1 to 10% by weight of an antistatic agent with respect to the polyester constituting the layer in the layer constituting the surface of one side. The birefringence (Δn) of the film is 0.040 or less, and the film has a coating layer on at least one side of the film.

Hereinafter, the present invention will be described in detail.
The polyester in the present invention is an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, 1, 4 It is a polyester mainly composed of an ester with glycol such as monocyclohexanedimethanol. The polyester is obtained by directly polymerizing an aromatic dicarboxylic acid and a glycol, or by a transesterification reaction between an aromatic dicarboxylic acid dialkyl ester and a glycol, followed by polycondensation, or an aromatic dicarboxylic acid diglycol. It can also be obtained by a method such as polycondensation of an ester. Typical examples of the polyester include polyethylene terephthalate, polyethylene-2,6-mononaphthalenedicarboxylate (PEN), boribylene terephthalate, and the like. Such a polyester may be a homopolymer that is not copolymerized, and 40 mol% or less of the dicarboxylic acid component is a dicarboxylic acid component other than the main component, and 40 mol% or less of the diol component is a diol component other than the main component. It may be a certain copolyester or a mixture thereof.

  The film of the present invention is a coextruded laminated film, and has a coextruded layer containing an antistatic agent in the surface layer. Examples of the antistatic agent include the following compounds.

  Cationic compounds such as primary amine salts, tertiary amines, quaternary ammonium compounds, sulfurized oils, sulfated amide oils, sulfated ester oils, fatty alcohol sulfates, alkyl sulfates, fatty acid ethyl sulfones Acid salts, alkyl sulfonates, alkyl naphthalene sulfonates, alkyl benzene sulfonates, phosphate esters, and other anionic compounds, partial fatty acid esters of polyhydric alcohols, ethylene oxide adducts of fatty alcohols, fatty amines or Nonionic compounds such as fatty acid amide ethylene oxide adduct, alkylphenol ethylene oxide adduct, alkylnaphthol ethylene oxide adduct, polyethylene glycol, fatty acid ester of alkyldiethanolamine, carboxylic acid derivatives, imidazo Those such emissions derivatives of amphoteric systems. Of these, sodium alkyl sulfonate, sodium alkyl benzene sulfonate, lithium alkyl sulfonate, lithium alkyl benzene sulfonate and the like are preferable from the viewpoint of antistatic performance and transparency.

  The content of the antistatic agent in the antistatic agent-containing coextruded layer of the film of the present invention is 0.1 to 10% by weight, preferably 0.1 to 5% by weight, based on the polyester constituting the coextruded layer. . When the amount of the antistatic agent is too small, a sufficient antistatic function cannot be exhibited. On the other hand, it is difficult to prepare a polyester raw material to which the antistatic agent is added in an amount exceeding 10% by weight.

  Moreover, it is preferable to provide the coextruded layer containing an antistatic agent on both surfaces of the film. Static electricity charged on the film is difficult to escape on one surface.

The surface resistivity of the film of the present invention is usually 1 × 10 ¹³ Ω / □ or less, preferably 1 × 10 ¹² 10Ω / □ or less. When the surface specific resistance exceeds 1 × 10 ¹³ Ω / □, the antistatic performance is inferior, and defects in the process may not be improved.

  The birefringence Δn of the film of the present invention is 0.040 or less, more preferably 0.030 or less, and still more preferably 0.020 or less. When Δn exceeds 0.040, the difference in strength between the film flow direction (vertical) and the width direction (horizontal) of the film becomes large, and the formability deteriorates.

  The surface roughness Ra of the film of the present invention is preferably 40 nm or less, more preferably 30 nm or less, and particularly preferably 20 nm or less. When Ra exceeds 40 nm, the surface roughness may be transferred to the printing layer, and the surface gloss of the molded product may be lost.

  In the present invention, the heat shrinkage rate for 5 minutes at 180 ° C. in the longitudinal and transverse directions of the film is usually 3.0% or less, more preferably 2.5% or less. When the thermal shrinkage rate exceeds 3.0%, it is not preferable because there is a tendency to cause printing distortion due to film shrinkage at the time of printing on a film or at the time of molding.

  In addition, the film of the present invention may contain additives such as wax, colorant, antioxidant, and ultraviolet absorber as necessary. In addition, inert particles having an average particle size of 0.1 μm or less may be contained as long as the surface roughness is not significantly affected.

  The film of the present invention has a coating layer on the surface in contact with the release layer of the printing layer. If there is no coating layer, the adhesiveness between the release layer of the printing layer and the support film is insufficient, and the release layer peels off from the support film in the transfer process and adheres to the molded product, thus reducing the appearance quality of the molded product. I might let you.

  This coating layer is composed mainly of a polymer and a crosslinking agent. The polymer comprises at least one of water-based polyurethane, water-based polyester, and water-based acrylic resin, and preferably has a glass transition temperature (Tg) of 0 ° C. or higher, more preferably 40 ° C. or higher, and more preferably polyester among polyurethanes. A polyurethane having a carboxylic acid residue, at least a part of which is made aqueous with an amine or ammonia. As the crosslinking agent, melamine-based, epoxy-based, or oxazoline-based resins are generally used, but melamine-based resins are preferable from the viewpoints of coating properties and durable adhesiveness.

  Moreover, it is preferable that the film of this invention has a coating layer which has antiblocking performance in the opposite surface of the above-mentioned coating layer. If there is no anti-blocking layer, the outermost adhesive layer of the printed layer and the surface of the support film may stick to each other in the step of producing a roll of the simultaneously molded decorative sheet by providing a printed layer on the support film. This anti-blocking coating layer is preferably composed mainly of a water-dispersible polyolefin resin and a crosslinking agent.

As polyolefin resin, the compound which has the compound as described in following (1)-(5) as a basic skeleton can be mentioned, for example.
(1) Waxes, resins, and rubber-like materials composed of homo- or copolymers of α-olefinic unsaturated hydrocarbons such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene. Examples of the corresponding compound include polyethylene, polypropylene, poly-1 monobutene, poly-4 monomethyl-1 monopentene, ethylene-propylene copolymer, ethylene-1 monobutene copolymer, propylene-1 monobutene copolymer. A polymer etc. are mentioned.
(2) A rubbery copolymer of two or more of the above α-olefins and a conjugated or non-conjugated diene. Applicable compounds include, for example, ethylene-propylene-budadiene copolymer, ethylene-propylene-dicyclopentadiene copolymer, ethylene-propylene-ethylidene norbornene copolymer, ethylene-propylene-1,5-hexadiene copolymer. And isobutene-isobrene copolymer.
(3) A copolymer of the above α-olefin and a conjugated or non-conjugated diene. Examples of the corresponding compound include an ethylene-butadiene copolymer and an ethylene-ethylidene norbornene copolymer.
(4) A copolymer of the above α-olefin (especially ethylene) and vinyl acetate and a complete or partially saponified product thereof.
(5) A graft polymer obtained by grafting the above conjugated or nonconjugated diene, vinyl acetate or the like onto the above-mentioned α-olefin homopolymer or copolymer, and a complete or partially saponified product thereof.

  In order to dissolve or disperse the above-described polyolefin or the like in water and stabilize the aggregation so as not to occur, a carboxylic acid group, a sulfonic acid group, an amino group, It is preferable to introduce a vinyl compound having a hydrophilic group such as a polyether, an alkylolamide group or a salt thereof. In particular, a saw press or a self-emulsifying type polyolefin dispersed or dissolved in water by introducing a vinyl compound having a hydrophilic group is preferred.

  A conventionally known surfactant can be used in combination, and a method in which a hydrophilic polymer such as a water-soluble polyester is allowed to coexist at the time of dispersion is also effective.

  Examples of the crosslinking agent used in the present invention include melamine-based, epoxy-based, amide-based, acrylamide-based compounds, polyisocyanates, block polyisocyanates, carbodiimide compounds, and the like. Examples of the melamine-based crosslinking agent include methoxymethylated melamine and butoxymethylated melamine which are alkylol or alkoxyalkylolated melamine compounds, and those obtained by co-condensing urea or the like with a part of melamine can also be used. Examples of the epoxy-based crosslinking agent include compounds having an epoxy group having a water solubility or a water solubilization rate of 50% or more.

  Moreover, an antifoamer, a coating property improving agent, a thickener, a disinfectant, inorganic particles, and organic particles can be added to the coating layer as necessary.

  As a method for applying the coating agent, for example, a reverse roll coater, a gravure coater, a rod coater, an air doctor coat as shown in Yuji Harasaki, Tsuji Shoten, published in 1979, “Coating Method”. Or other coating devices can be used. The coating layer may be formed only on one side of the polyester film or on both sides. When it is formed only on one side, an application layer different from the above-mentioned application layer can be formed on the opposite side as necessary to give other characteristics. In addition, in order to improve the applicability | paintability to the film of a coating agent and adhesiveness, you may perform a chemical process and an electrical discharge process to a film before application | coating. Moreover, in order to further improve the surface characteristics, a discharge treatment may be performed after the coating layer is formed.

  The thickness of the coating layer is usually in the range of 0.01 to 0.5 μm, preferably 0.02 to 0.3 μm, as the final dry thickness. When the thickness of the coating layer is less than 0.01 μm, the adhesion and antiblocking properties may be inferior. On the other hand, the thickness of the coating layer is O.D. When it exceeds 5 μm, the stability of the coating solution is lowered, and coating unevenness may occur.

  The thickness of the film of this invention is 10-200 micrometers normally, Preferably it is 10-100 micrometers, More preferably, it is 10-75 micrometers.

  Next, although the manufacturing method of the film of this invention is demonstrated concretely, as long as the structural requirements of this invention are satisfied, it is not specifically limited to the following illustrations.

When the film of the present invention is produced, the dried polyester is supplied to an extruder and heated to a temperature equal to or higher than the melting point of each polyester to be melted. Subsequently, it extrudes from a T die as a molten sheet. Subsequently, the molten sheet is rapidly cooled to below the glass transition temperature on a rotary cooling drum to obtain an amorphous unstretched film. At this time, in order to improve the flatness of the unstretched film, the adhesion between the unstretched film and the rotating cooling drum may be improved by an electrostatic application adhesion method, a liquid application adhesion method, or the like. And a uniaxially stretched film is obtained by extending | stretching an unstretched film in the longitudinal direction (longitudinal stretching) using a roll stretching machine. The stretching temperature at this time is stretched in a temperature range of minus 10 ° C. to plus 40 ° C. of the glass transition temperature (Tg) of the raw material resin. The draw ratio is preferably 2.5 to 7.0 times, more preferably 3.0 to 6.0 times. Furthermore, longitudinal stretching may be performed in only one stage, or may be performed in two or more stages. Next, an aqueous coating agent is applied by a coater to provide an easy adhesion layer. Thereafter, the biaxially stretched film is obtained by stretching the uniaxially stretched film in the width direction (lateral stretching) using a tenter stretching machine. The stretching temperature at this time is stretched in a temperature range of + 50 ° C. from the glass transition temperature (Tg) of the raw material resin. The draw ratio is preferably 2.5 to 7.0 times, more preferably 3.5 to 6.0 times. Further, the transverse stretching may be performed only in one stage, or may be performed in two or more stages. Moreover, you may perform simultaneous biaxial stretching which performs vertical and horizontal simultaneously. And a laminated film is manufactured by heat-processing a biaxially stretched film. The heat processing temperature at this time is 130-250 degreeC. When the biaxially stretched film is heat-treated, the biaxially stretched film may be relaxed within 20%.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of metal mold | die rust can be suppressed and the biaxially stretched polyester film for shaping | molding simultaneous transfer which can perform fine printing can be provided, The industrial value is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement methods and terms used in the examples and the present invention are defined as follows.

(1) Birefringence (Δn)
An Atago appe refractometer was used. Methylene iodide is mounted, the sample film is closely attached to the prism so that the measurement surface faces down, and the refractive index in the longitudinal direction, the width direction, and the thickness direction (Nx, respectively) using a monochromatic light sodium D line (589 nm) as a light source. Ny, Nz). The birefringence Δn of each layer is obtained from the obtained value by the following formula.
Δn = Nx−Ny

(2) Surface resistivity 16600A, which is a concentric electrode with a 50 mm diameter inner electrode and a 70 mm diameter outer electrode manufactured by Yokogawa Hewlett Packard, was placed on the sample in an atmosphere of 23 ° C. and 50% RH, and a voltage of 100 V was applied. Then, the surface resistivity of the sample is measured with 4329A, a high resistance meter manufactured by the same company.

(3) Surface roughness Ra
Measurement is performed according to JIS-B-0601-1982 using a surface roughness measuring machine (SE-3F) manufactured by Kosaka Laboratory. However, the cut-off value is 80 μm and the measurement length is 2.5 mm.

(4) 180 ° C. film shrinkage rate Using a hot air circulating furnace (manufactured by Taiba Seisakusho), a film of 25 μm thickness in a tension-free state was heat-treated in an atmosphere of 180 ° C. for 5 minutes, The length before and after the heat treatment is measured, calculated by the following formula, and expressed as an average value for every five samples.
Thermal contraction rate (%) = (L ₀ −L ₁ ) × 100 / L ₀
(In the above formula, L ₀ represents the sample length (mm) before heat treatment, and L ₁ represents the sample length (mm) after heat treatment)
Note, L ₀ may be less than L ₁ (when the film expands) the value of the thermal shrinkage - expressed in (negative).

(4) Adhesiveness to the release layer An organic solvent solution in which melamine resin is dissolved is applied to the release layer forming surface of the film, a release layer with a dry thickness of 1 μm is formed, and placed on a mold by hot pressing. Observe the condition of the mold release layer. The judgment criteria are as follows.
○: No peeling Δ: The peeled area is 10% or less ×: peeling exceeding 10%

(5) Formability Using a mold having a length of 10 cm, a width of 10 cm, and a maximum depth of 1.5 cm, the film was called and molded inside the mold by vacuum and compressed air, and then molded by injecting a heated resin. . The moldability of the film was evaluated as follows according to the frequency of film breakage during molding.
○: No film breakage △: Film breakage sometimes occurs at one or two places, which may cause trouble during long time operation ×: Film breakage occurs frequently and cannot be used (6) Halogen element in coating layer The Kα intensity of the halogen element was measured by a FP method (Fundamental Parameter Method) using a fluorescent X-ray measurement apparatus (model “XRF-1500” manufactured by Shimadzu Corporation).
○: No Kα intensity peak for halogen element ×: Kα intensity peak for halogen element

Next, the polyester raw material used for an Example is demonstrated.
・ Polyester a
It is a polyethylene terephthalate resin having an intrinsic viscosity of 0.65 and a melting point of 253 ° C. synthesized by a conventional polycondensation.

・ Polyester b
This is a polyethylene terephthalate resin synthesized by a conventional polycondensation and containing 0.9% by weight of amorphous silica having an average particle size of 2.5 μm and an intrinsic viscosity of 0.66 and a melting point of 253 ° C.

・ Polyester c
This is a polyethylene terephthalate resin synthesized by a conventional polycondensation and having an intrinsic viscosity of 0.62 and a melting point of 253 ° C. containing 0.25% by weight of organic particles having an average particle size of 0.37 μm.

・ Polyester d
This is a product obtained by kneading sodium dodecylbenzenesulfonate into a polyethylene terephthalate resin having an intrinsic viscosity of 0.68 and a melting point of 253 ° C. synthesized by a conventional polycondensation and containing 1.5% by weight.

・ Water-based coating agent 1
The aqueous coating agent is a mixture in which the following compounds (a), (b), (c) and (d) are mixed at a weight ratio of 47/20/30/3.
(A): Polyester obtained by reacting terephthalic acid / isophthalic acid / 5 monosodium sulfoisophthalic acid / ethylene glycol / 1.4 monobutanediol / diethylene glycol in a molar ratio of 28/20/2/35/10/5, respectively Water dispersion (b): Polymer water dispersion obtained by polymerizing methyl methacrylate / ethyl acrylate / acrylonitrile / N-methylol methacrylamide in a molar ratio of 45/45/5/5 (emulsifier: anionic surfactant) )
(C): Melamine-based crosslinking agent (hexamethoxymethylmelamine)
(D): An aqueous dispersion of silicon oxide having an average particle size of 0.06 μm

・ Water-based coating agent 2
The aqueous coating agent is a mixture in which the following compounds (a ′), (b ′), and (c ′) are mixed at a weight ratio of 65/5/30.
(A ′): polydiallyldimethylammonium chloride (b ′): partially saponified polyvinyl alcohol (degree of saponification: about 88 mol%)
(C ′): Methoxymethylol melamine (Beckamine J1001 manufactured by Omemoto Ink Co., Ltd.)

Example 1:
A mixture of 80% by weight of polyester d and 20% by weight of polyester b is fed to a vented twin-screw extruder (forming a surface layer), and 100% by weight of polyester a is another twin-screw extruder with vent (middle layer) After being melted at a melting temperature of 280 ° C., the molten polymer from each extruder was merged with a feed block through a gear pump and a filter, and was drawn on a casting drum through a die to obtain an unstretched film of two types and three layers. . The unstretched film thus obtained was fed into a longitudinal stretching roll and first stretched 3.5 times at a film temperature of 83 ° C., and then an easy-adhesive aqueous coating agent 1 was applied to one side, led to a tenter and transversely at 95 ° C. The film was stretched 4.0 times to obtain a biaxially oriented film. Next, the obtained biaxially oriented film was guided to a heat setting zone and heat-treated at 220 ° C. to obtain a polyester film having a thickness described in Table 1.

Example 2:
A film was obtained in the same manner as in Example 1 except that polyester c was used instead of polyester b.

Comparative Example 1:
A film was obtained in the same manner as in Example 1 except that the aqueous coating agent 1 was not applied on one side.

Comparative Example 2:
A film was obtained in the same manner as in Example 1 except that polyester a was used in place of polyester d and antistatic water-based coating agent 2 was used.

Comparative Example 3:
A mixture of 90% by weight of polyester a and 10% by weight of polyester b is fed to a twin screw extruder with a vent and melted at a melting temperature of 280 ° C., and then the molten polymer is drawn through a die through a die to a casting drum through a gear pump and a filter. An unstretched film was obtained. The unstretched film thus obtained was fed into a longitudinal stretching roll, first stretched 1.1 times at a film temperature of 83 ° C., then led to a tenter and stretched 4.0 times in the transverse direction at 95 ° C. to obtain a biaxially oriented film. It was. Next, the obtained biaxially oriented film was guided to a heat setting zone and heat-treated at 220 ° C. to obtain a polyester film having a thickness described in Table 1.

The obtained results are summarized in Table 1 below.
In Examples 1 and 2, the film is excellent in the release layer and adhesive antistatic effect, and is less likely to cause rusting of the mold. On the other hand, Comparative Example 1 is inferior in easy adhesion to the acrylic resin release layer because there is no easy adhesion coating layer. Since the comparative example 2 uses the antistatic coating layer containing a halogen ion, rust may generate | occur | produce in a metal mold | die. Comparative Example 3 had a large birefringence and was inferior in moldability.

  The film of the present invention can be suitably used as a support film for a simultaneously molded decorative sheet used for decorating resin molded products such as electric products and automobile parts.

Claims (1)

A laminated film obtained by a coextrusion method, containing at least 0.1 to 10% by weight of an antistatic agent relative to the polyester constituting the layer in the layer constituting the surface on one side, and the birefringence of the film A biaxially stretched polyester film for molding simultaneous transfer, characterized in that the rate (Δn) is 0.040 or less and the coating layer is provided on at least one side of the film.