JP5317519B2 - In-mold transfer film - Google Patents

Description

In recent years, there is a tendency to differentiate the design of devices such as mobile phones and notebook computers. As this decoration method, adoption of simultaneous molding is increasing. As a method of simultaneous molding decoration, there are in-mold transfer, in-mold molding, and insert molding. Among these, the present invention relates to a transfer film used for in-mold transfer. Furthermore, it is related with the transfer film for in-mold which can print a pattern layer with a thermal transfer printer.

In-mold transfer is a technique in which a transfer film is fed into an injection mold and a molten resin is injected onto the adhesive side of the film to transfer a pattern simultaneously with molding using the melting temperature and injection pressure of the resin. The two processes of molding and decoration can be performed at once, and trimming after molding is unnecessary, and it is characterized by high productivity. Furthermore, conventionally, the gravure printing, silk screen printing, etc. have been used for printing the image layer on the transfer film for in-mold, but as a method that enables small lot printing due to design differentiation, the image can be printed with a thermal transfer printer. An in-mold transfer film that can be formed has been desired.

Depending on the use of the molded product decorated by in-mold transfer, there are some which require fastness such as scratch resistance and chemical resistance. In this case, a protective layer is provided on the transfer layer of the in-mold transfer film so that the protective layer is transferred to the surface of the molded product. In order to increase the robustness of the protective layer, it is necessary to form a protective layer containing a curable resin as a main component. However, if the protective layer is cured before performing in-mold transfer, the three-dimensional followability of the molded product tends to decrease. For this reason, it is necessary to harden the protective layer on the surface of the molded product after in-mold transfer, and an ionizing radiation curing type is suitable as the curing type resin. In the thermosetting type, the molded product is deformed by heat treatment by curing. However, if an in-mold transfer is performed in an uncured protective layer mainly composed of ionizing radiation curable resin on the transfer layer of the transfer film for in-mold, the resin injection gate of the mold is injected by the injection of the heating resin at the time of injection molding. There was a problem that the pattern layer flowed nearby. (Patent Document 1)
JP-A-6-155518

The present invention provides an in-mold transfer film that prevents a pattern layer printed by a thermal transfer printer from flowing during in-mold transfer, and can provide fastness such as scratch resistance and solvent resistance.

(1) A protective layer containing at least an ionizing radiation curable resin as a main component, a heat-resistant layer containing a thermosetting resin, an image receiving layer / adhesive layer , and a pattern layer printed by a thermal transfer printer are laminated in this order on the substrate. A transfer film for in-mold that uses a thermoplastic resin as a main component is used for the binder of the pattern layer .
(2) Furthermore, the in-mold transfer film according to the item (1), wherein the heat-resistant layer contains 30% by weight or more of polyisocyanate.
(3) Further, an intermediate adhesive layer mainly comprising a thermoplastic resin having a softening point of 50 to 130 ° C. is provided between the protective layer and the heat-resistant layer. Use a transfer film.

It is possible to provide an in-mold transfer film in which a pattern layer printed by a thermal transfer printer does not flow during in-mold transfer and can provide fastness such as scratch resistance and solvent resistance.

  The in-mold transfer film used in the present invention is obtained by laminating a protective layer containing at least an ionizing radiation curable resin as a main component, a heat-resistant layer containing a thermosetting resin, and an image receiving layer / adhesive layer in this order on a substrate. It is.

  Examples of the base material include polyethylene terephthalate and other polyester, polycarbonate, polyamide, polyimide, cellulose acetate, polyvinylidene chloride, polyvinyl chloride, polystyrene, fluororesin, polypropylene, polyethylene, ionomer plastic films, and glassine paper. In addition, there are papers such as condenser paper and paraffin paper, cellophane, etc., and composite films in which two or more of these are laminated can also be used. Furthermore, when considering transfer to a plastic molded product, it is preferable that the transfer film is thermally deformed so as to conform to the shape of the molded product, and a substrate that can be easily thermally deformed, such as an easily molded PET film or an acrylic film, is used. Good to use. Although the thickness of these base materials is suitably changed according to the material so that the strength and heat resistance are appropriate, it is usually preferably about 10 to 100 μm.

  As the ionizing radiation curable resin used for the protective layer, for example, a composition comprising a single polymer or a mixture of a prepolymer or a monomer having a radical polymerizable unsaturated group in the molecule can be used. Alternatively, a composition comprising a prepolymer or a monomer having a cationic polymerizable functional group can also be used as the ionizing radiation curable resin.

  Examples of the prepolymer having a radically polymerizable unsaturated group include polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, melamine (meth) acrylate, and triazine (meth) acrylate. (Meth) acrylate means acrylate or methacrylate. Examples of the monomer having a radical polymerizable unsaturated group include, as monofunctional monomers, methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like. In addition, as polyfunctional monomers, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethylene oxide tri (meth) acrylate, dipentaerythritol penta (meth) acrylate And dipentaerythritol hexa (meth) acrylate.

  A more preferable ionizing radiation curable resin is an ionizing radiation curable acrylic-silica hybrid resin. The acrylic-silica hybrid resin preferably has a silica component of 15 to 60% by weight, more preferably 20 to 30% by weight. Outside the above range, the film strength is lowered, and the function as a protective layer may be deteriorated.

  The acrylic-silica hybrid resin preferably has no tack at room temperature before curing. If there is no tack, so-called blocking, where the protective layer is applied and dried on the base material, once it is rolled up, the protective layer sticks to the opposite surface of the base material and peels off from the base material. Not only does the problem called “occurrence” hardly occur, but also in the case of further laminating a heat-resistant layer on the protective layer, there is an advantage that the film design is facilitated such as easy lamination. Moreover, it is preferable that Tg before hardening of this acrylic-silica hybrid resin is 30 degreeC or more. If it is less than 30 degreeC, there exists a tendency for tack to come out easily at normal temperature.

  Examples of the prepolymer having a cationic polymerizable functional group include prepolymers of bisphenol type epoxy resins, epoxy resins such as novolac type epoxy compounds, and vinyl ether resins such as fatty acid vinyl ethers and aromatic vinyl ethers.

  In addition to the ionizing radiation curable resin, a thermoplastic resin can be added. Examples of the thermoplastic resin include acrylic resins, cellulose resins, polyester resins, thermoplastic urethane resins, or vinyl resins such as vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, and butyral resins. One kind or a mixture of two or more kinds can be used. The acrylic resin has (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid-n-propyl, isopropyl (meth) acrylate, (meth) as the monomer. Acrylic acid-n-butyl, (meth) acrylic acid isobutyl, (meth) acrylic acid-n-amyl, (meth) acrylic acid-n-hexyl, (meth) acrylic acid-n-octyl, (meth) acrylic acid lauryl (Meth) acrylic acid alkyl ester such as (meth) acrylic acid-2-chloroethyl, (meth) acrylic acid alkyl halide such as 3-chloropropyl, (meth) acrylic acid-2-hydroxy (Meth) acrylic acid ester having a hydroxyl group such as ethyl, (meth) acrylic acid-2-hydroxypropyl, α-chloro ( A) Halogenated (meth) acrylic acid esters such as methyl acrylate, α-chloro (meth) ethyl acrylate, and α-alkyls having a hydroxyl group such as (meth) acrylic acid-1-chloro-2-hydroxyethyl (meth) ) A homopolymer or copolymer composed of one or more of (meth) acrylic monomers such as acrylate esters and glycidyl (meth) acrylate. In addition, (meth) acryl means acryl or methacryl.

  When the ionizing radiation curable resin is cured with ultraviolet rays or visible rays, a photopolymerization initiator is further added to the mixture. In the case of a resin system having a radically polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, and benzoin methyl ethers can be used alone or in combination as a photopolymerization initiator. In the case of a resin system having a cationic polymerizable functional group, an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, a benzoin sulfonic acid ester or the like is used alone or as a mixture as a photopolymerization initiator. be able to. The addition amount of these photopolymerization initiators is about 0.1 to 10 parts by weight with respect to 100 parts by weight of the ionizing radiation curable resin.

  Furthermore, you may add various additives as needed. Examples of these additives include extender pigments (fillers) such as calcium carbonate and barium sulfate powders, lubricants made of powders such as alumina and silica, lubricants such as waxes, colorants, and UV absorbers. is there.

  As the ionizing radiation, electromagnetic waves or charged particles having energy capable of cross-linking molecules in the ionizing radiation curable resin are used. Usually used are ultraviolet rays or electron beams, but in addition, visible light, X-rays, ion rays and the like can also be used. As the ultraviolet light source, a light source such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc lamp, a black light, a metal halide lamp or the like is used. As a wavelength of ultraviolet rays, a wavelength range of 190 to 380 nm is mainly used. As the electron beam source, various electron beam accelerators such as a cockcroft Walton type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, a high frequency type, etc. are used, preferably 100 to 1000 keV, preferably That irradiates electrons having energy of 100 to 300 keV is used.

  The thickness of the protective layer can be appropriately adjusted according to the requirements of the abrasion resistance and chemical resistance of the molded product to which the pattern is transferred, and 3 to 20 μm is appropriate. More preferably, it is in the range of 4 to 15 μm.

  The heat-resistant layer contains a thermosetting resin. Furthermore, it is preferable to use a mixture of a thermosetting resin and a thermoplastic resin as a main component, and it is preferable to use polyisocyanate as the thermosetting resin. It is preferable to use polyisocyanate in the range of 30 to 90% by weight for the heat-resistant layer. A reaction cured product of a thermoplastic resin having a reactive group and a polyisocyanate may be used, or a mixture of a thermoplastic resin having no reactive group and a polyisocyanate may be used. In a mixture of a thermoplastic resin having a reactive group and a polyisocyanate, if the heat-resistant layer is all a cured layer, the followability to the three-dimensional shape of the molded product is inferior during in-mold transfer, and cracks may occur. The heat-resistant layer preferably contains a part of a thermoplastic resin having no reactive group. The content of the thermoplastic resin having no reactive group in the heat-resistant layer is preferably in the range of 20 to 90% by weight. More preferably, it is in the range of 30 to 70% by weight.

  Examples of the thermoplastic resin include epoxy resins, acrylic resins, cellulose resins, polyester resins, thermoplastic urethane resins, modified olefin resins such as chlorinated polyethylene and chlorinated polypropylene, or vinyl acetate. One or a mixture of two or more vinyl resins such as a resin, vinyl chloride-vinyl acetate copolymer, butyral resin can be used. The acrylic resin has (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, (meth) acrylic acid-n-propyl, isopropyl (meth) acrylate, (meth) as the monomer. Acrylic acid-n-butyl, (meth) acrylic acid isobutyl, (meth) acrylic acid-n-amyl, (meth) acrylic acid-n-hexyl, (meth) acrylic acid-n-octyl, (meth) acrylic acid lauryl (Meth) acrylic acid alkyl ester such as (meth) acrylic acid-2-chloroethyl, (meth) acrylic acid alkyl halide such as 3-chloropropyl, (meth) acrylic acid-2-hydroxy (Meth) acrylic acid ester having a hydroxyl group such as ethyl, (meth) acrylic acid-2-hydroxypropyl, α-chloro ( A) Halogenated (meth) acrylic acid esters such as methyl acrylate, α-chloro (meth) ethyl acrylate, and α-alkyls having a hydroxyl group such as (meth) acrylic acid-1-chloro-2-hydroxyethyl (meth) ) A homopolymer or copolymer composed of one or more of (meth) acrylic monomers such as acrylate esters and glycidyl (meth) acrylate.

  The thickness of the heat resistant layer is preferably 0.3 to 5.0 μm. More preferably, it is in the range of 0.5 to 2.0 μm. If it is 0.3 μm or less, it is difficult to prevent the printed pattern layer from flowing during in-mold transfer. If it is 5.0 μm or more, moldability tends to be impaired.

  In order to improve the adhesion between the heat-resistant layer and the protective layer, an intermediate adhesive layer may be appropriately provided between the two layers. As the intermediate adhesive layer, a thermoplastic resin having a softening point of 50 to 130 ° C. can be used. When the softening point is less than the above range, storage stability is applied. If it exceeds the above range, the adhesion tends to decrease. Examples of the thermoplastic resin include epoxy resins, acrylic resins, cellulose resins, polyester resins, thermoplastic urethane resins, modified olefin resins such as chlorinated polyethylene and chlorinated polypropylene, or vinyl acetate. One or a mixture of two or more vinyl resins such as a resin, vinyl chloride-vinyl acetate copolymer, butyral resin can be used.

  The thickness of the intermediate adhesive layer is preferably 0.1 to 5.0 μm. More preferably, it is in the range of 0.3 to 1.0 μm. If the thickness is less than the above range, the adhesion tends to decrease. If the above range is exceeded, the strength will decrease.

  A thermoplastic resin is used as the image receiving layer / adhesive layer. Examples of the thermoplastic resin include epoxy resins, acrylic resins, cellulose resins, polyester resins, thermoplastic urethane resins, modified olefin resins such as chlorinated polyethylene and chlorinated polypropylene, or vinyl acetate. One or a mixture of two or more vinyl resins such as a resin, vinyl chloride-vinyl acetate copolymer, butyral resin can be used. Moreover, it is particularly preferable to use an acrylic-modified polyester urethane resin.

  Various fillers can be added to prevent blocking and tack. Examples thereof include fluororesin-based particles, melamine resin particles, silicon-based particles, talc, kaolin, magnesium carbonate, potassium carbonate, titanium oxide, silica, starch and the like.

  The thickness of the image receiving layer / adhesive layer is preferably 0.1 to 5.0 μm. More preferably, it is set as the range of 0.1-1.0 micrometer. If it is less than the above range, image receiving property and adhesiveness cannot be obtained. If it exceeds the above range, the heat resistance tends to decrease.

  Additives such as a film-forming aid, a coating solution stabilizer, a leveling agent, and an antifoaming agent can be added to each layer. Each layer can be formed by dissolving a constituent material in an appropriate solvent to form a coating solution, and applying and drying the substrate on a substrate by various coating methods. The thermosetting resin in the heat-resistant layer is heated and cured at the time of coating and drying.

  The thermal transfer sheet is one in which at least a heat-meltable colored ink layer is provided on a substrate. As the substrate, a PET film having a thickness of 1 to 10 μm is suitably used. The colored ink layer is composed of a colorant and mainly a binder. The binder is selected from thermoplastic resins and waxes. In order to make the pattern layer difficult to flow during in-mold transfer, the binder contains a thermoplastic resin as a main component. The ratio of the thermoplastic resin in the binder is preferably 50 to 90% by weight. The thickness of the colored ink layer is about 0.2 to 3 μm. Preferably, it is set as the range of 0.4-1.0 micrometer. When the thickness is less than the above range, the color density is difficult to be obtained. If the range is exceeded, the pattern layer tends to flow during the insert transfer. In particular, the thickness of each colored ink layer in the case of forming a full color pattern layer by superimposing and transferring by using three or more colored ink layers such as yellow, magenta, and cyan as the colored ink layer is 0.2 to The range is 2.0 μm. The method for providing the colored ink layer on the substrate may be formed by a method conventionally used in the field of thermal transfer recording media.

Example 1
1. Preparation of heat transfer sheet On the back surface of 4.5 μm thick heat-treated PET film, yellow, magenta and cyan pigments are dispersed in a vinyl chloride / vinyl acetate copolymer resin together with a solvent to give three colored inks, A gravure coat was applied at a coating thickness of 0.5 μm to prepare three color thermal transfer sheets.

2. Preparation of transfer film for in-mold The following protective layer coating solution 1 was applied to the surface of a PET film having a thickness of 38 μm with a bar coater so that the dry thickness was 5 μm. Subsequently, the following heat-resistant layer coating solution 1 was coated on the protective layer with a bar coater so that the dry thickness was 2 μm, and the following image-receiving layer / adhesive layer coating solution was further formed thereon. 1 was applied with a bar coater so that the dry thickness was 0.1 μm, and an in-mold transfer film 1 was prepared.
Furthermore, full-color painting was performed on the image receiving layer / adhesive layer surface of the transfer film 1 for in-mold using the thermal transfer sheet and the thermal transfer printer (head resolution: 600 dpi).

Coating liquid for protective layer 1
70 parts by weight of UV curable acrylic-silica hybrid resin (solid content 30%, silica component 23%, Tg 45 ° C., weight average molecular weight 20,000)
1.0 parts by weight of photoinitiator (Darocur 1173, manufactured by Ciba Specialty Chemicals)
MEK 30 parts by weight

Coating solution for heat-resistant layer 1
15 parts by weight of acrylic resin (molecular weight 300,000 Tg 105 ° C.)
10 parts by weight of polyisocyanate (Takenate D-204, solid content 50%, manufactured by Takeda Pharmaceutical)
MEK 75 parts by weight

Coating solution for image-receiving layer / adhesive layer 1
15 parts by weight of polyester resin (molecular weight 30,000, Tg 68 ° C.)
MEK 45 parts by weight Toluene 40 parts by weight

(Example 2)
In the production of the in-mold transfer film of Example 1, an intermediate adhesive layer was applied between the protective layer and the heat-resistant layer by applying the following intermediate adhesive layer coating solution 1 with a bar coater so that the dry thickness was 0.5 μm. An in-mold transfer film 2 was produced in the same manner as in Example 1 except that it was provided by processing.
Intermediate adhesive layer coating solution 1
50 parts by weight of acrylic-modified polyester urethane resin (Samprene IB582, solid content 42%, softening point 120 ° C., manufactured by Sanyo Chemical)
Toluene 40 parts by weight IPA 10 parts by weight

(Comparative Example 1)
In-mold transfer film 3 was similarly prepared except that the heat-resistant layer coating solution of Example 1 was coated with a bar coater so that the dry thickness was 2 μm with the following heat-resistant layer coating solution 2. Was made.
Heat-resistant layer coating solution 2
15 parts by weight of acrylic resin (molecular weight 300,000, Tg 105 ° C.)
MEK 45 parts by weight Toluene 40 parts by weight

The painted in-mold transfer film obtained as described above was put into an in-mold molding die, injected with acrylic resin, and simultaneously decorated by in-mold transfer, and decorated. A molded product was created. Subsequently, the protective layer was cured by irradiating UV light with an integrated light amount of 200 mj / cm ² with a conveyor-type UV irradiation device (CS30 manufactured by GS).

Evaluation method (1) Pattern flow in the vicinity of the molded resin injection gate ○: No flow, Δ: Slight flow is observed, X: Flow (2) Foil cut property ○: Foil cut property is good, Δ: Plane peeling tendency, X: Large exfoliation of the surface (3) One drop of water, ethanol, MEK, and toluene is dropped on each of the water / solvent resistant sample, and the state of the sample is observed after 30 minutes.
◯: No change, Δ: Slightly eroded, X: Completely eroded (4) The scratch-resistant sample is rubbed 10 times with steel wool (Bonster # 0000) loaded with a load of 250 g / cm ² .
○: No change, Δ: Some scratches, ×: Large scratches (5) Adhesive cross-cut test: According to JIS K5400.

The above evaluation results are shown in Table 1.
Table 1

Claims (3)

A protective layer containing at least an ionizing radiation curable resin as a main component, a heat-resistant layer containing a thermosetting resin, an image receiving layer / adhesive layer , and a pattern layer printed by a thermal transfer printer are laminated in this order on the substrate . A transfer film for in-mold , wherein the binder of the pattern layer is mainly composed of a thermoplastic resin. The in-mold transfer film according to claim 1, wherein the heat-resistant layer contains 30% by weight or more of polyisocyanate. The transfer film for in-mold according to claim 1, wherein an intermediate adhesive layer mainly comprising a thermoplastic resin having a softening point of 50 to 130 ° C. is provided between the protective layer and the heat-resistant layer.