JP7443072B2 - Base film for transfer film - Google Patents

Description

The present invention relates to a base film for a transfer film.

BACKGROUND ART In order to protect or decorate the surface of resin molded bodies such as home appliances and automobile interior parts, transfer layers including hard coat layers, decorative layers, etc. are transferred (Patent Documents 1 and 2).

Furthermore, in order to protect electronic circuits from electromagnetic waves, an electromagnetic shielding layer (electromagnetic shielding film) containing an insulating layer, a conductive layer, etc. is transferred onto a circuit board by hot pressing (Patent Documents 3 to 5). .

Japanese Patent Application Publication No. 2011-148103 Japanese Patent Application Publication No. 2015-214032 Patent No. 5796690 Patent No. 6014680 Patent No. 6426865

The transfer layer of the above-mentioned transfer film may be half-cut in advance to a specific size or shape depending on the type of adherend and required performance. Prior to this half-cut step, a protective film may be attached to the surface of the transfer film opposite to the surface on which the transfer layer is laminated, but the protective film may peel off during the half-cut step.

Therefore, an object of the present invention is to provide a base film for a transfer film that has improved adhesion between the base film used for the transfer film and a protective film.

The above object of the present invention was achieved by the following configuration.
[1] A base film for a transfer film for laminating a transfer layer on one side of the base film, comprising a polyester film and a urethane bond on the opposite side of the polyester film to the side on which the transfer layer is laminated. A base film for a transfer film, which has a back layer containing a resin.
[2] The base film for a transfer film according to [1], wherein the back layer contains a structure in which a melamine compound is crosslinked.
[3] The base film for a transfer film according to [1] or [2], wherein the surface of the polyester film on which the transfer layer is laminated has an arithmetic mean roughness Ra of 0.30 μm or more.
[4] The base film for a transfer film according to any one of [1] to [3], wherein the polyester film has a three-layer laminate structure consisting of layer A/layer B/layer A.
[5] A transfer film comprising a transfer layer laminated on the surface opposite to the surface having the back layer of the base film for transfer film according to any one of [1] to [4].

According to the present invention, it is possible to provide a base film for a transfer film that has good adhesion to a protective film.

The base film for a transfer film of the present invention is a base film for a transfer film for laminating a transfer layer on one side of the base film, comprising a polyester film and a side of the polyester film on which the transfer layer is laminated. It has a back layer containing a resin having urethane bonds on the opposite side.

The base film for a transfer film of the present invention is a base film used to obtain a transfer film, and a transfer layer is laminated on one surface of this base film to obtain a transfer film. The transfer layer of the transfer film is peeled off from the base film and transferred to the adherend. Hereinafter, the base film for transfer film may be referred to as "base film".

The base film of the present invention has a back layer containing a resin having a urethane bond on the opposite side to the side on which the transfer layer is laminated. Providing this back layer improves the adhesion between the base film and the protective film. Therefore, in the transfer film using the base film of the present invention, even during half-cutting, peeling of the protective film bonded in advance to the surface opposite to the transfer layer of the transfer film is suppressed. Further, since the back layer containing a resin having a urethane bond has excellent adhesion to the polyester film, the back layer is difficult to peel off from the polyester film during the manufacturing process or processing process of the base film.

[Back layer]
The back layer contains a resin having urethane bonds. A resin having a urethane bond can be obtained, for example, by reacting a compound containing a hydroxyl group with a compound containing an isocyanate group.

Examples of the method for making the back layer contain a resin having a urethane bond include the following embodiments.
(i) An embodiment in which a composition (thermosetting composition) containing a compound having a hydroxyl group and a compound having an isocyanate group is applied onto a polyester film, dried and heated,
(ii) An embodiment in which a composition (thermosetting composition) containing a compound having a hydroxyl group and a urethane bond and a compound having an isocyanate group is applied onto a polyester film, dried and heated,
(iii) an embodiment in which a composition containing a resin having a urethane bond is applied onto a polyester film and dried;
(iv) An embodiment in which two or more of the above (i) to (iii) are combined.

Among the above embodiments, the above embodiment (i) or (ii) is preferable from the viewpoint of increasing the adhesion between the base film and the protective film.

In the embodiment (i) or (ii) above, the composition (thermosetting composition) containing a compound having a hydroxyl group or a compound having a hydroxyl group and a urethane bond, and a compound having an isocyanate group is capable of absorbing energy such as heat. By providing a compound having a hydroxyl group or a compound having a hydroxyl group and a urethane bond, the hydroxyl group and the isocyanate group of the compound having an isocyanate group generate a urethane bond, thereby producing a resin having a urethane bond in the molecule.

The embodiment (i) above (thermosetting composition) will be explained in detail.

Examples of compounds having hydroxyl groups include acrylic polyols, polyether polyols, polyester polyols, polyolefin polyols, and polycarbonate polyols. These hydroxyl group-containing compounds may be used alone or in combination of two or more.

Acrylic polyol can be obtained, for example, by copolymerizing a (meth)acrylic monomer and a hydroxyl group-containing (meth)acrylic monomer. Here, "(meth)acrylic" is a general term for "acrylic" and "methacrylic". In the following description, "...(meth)acrylate" is a generic term for "...acrylate" and "...methacrylate."

Examples of the (meth)acrylic monomer include (meth)acrylic acid alkyl ester monomers. Examples of such compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, and tert-butyl (meth)acrylate. , lauryl (meth)acrylate, stearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, methylhexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, etc. .

Examples of hydroxyl group-containing (meth)acrylic monomers include hydroxyethyl (meth)acrylate, polyoxyethylene (meth)acrylate, polyoxypropylene (meth)acrylate, polycaprolactone-modified (meth)acrylate, and polycarbonate polyol-modified (meth)acrylate. Examples include acrylate, polyester polyol-modified (meth)acrylate, and the like.

Examples of acrylic polyols include DIC Corporation; (product name "Acridic (registered trademark)" series, etc.), Taisei Fine Chemical Co., Ltd. (product name "Acrit (registered trademark)" series, etc.), Nippon Shokubai Co., Ltd.; (trade name "Acryset (registered trademark)" series, etc.), Mitsui Chemicals, Inc.; (trade name "Takelac (registered trademark)" UA series), etc., and these products can be used.

Examples of polyether polyols include polyethylene glycol or triol, polypropylene glycol or triol, polybutylene glycol or triol, polytetramethylene glycol or triol, and addition polymers and block copolymers of these oxyalkylene compounds with different carbon numbers. can be mentioned. Examples of polyether polyols having such hydroxyl groups include Asahi Glass Co., Ltd. (product name "Excenol (registered trademark)" series, etc.) and Mitsui Chemicals Co., Ltd. (product name "Actocol (registered trademark)" series, etc.). These products can be used.

Examples of polyester polyols include aliphatic glycols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, decanediol, cyclohexanedimethanol, caprolactonediol, and succinic acid, adipic acid, and sebacic acid. , aliphatic polyester polyols reacted with aliphatic dibasic acids such as fumaric acid, suberic acid, azelaic acid, 1,10-decamethylene dicarboxylic acid, and cyclohexane dicarboxylic acid as essential raw materials, ethylene glycol, propylene glycol, Examples include aromatic polyester polyols in which an aliphatic glycol such as butanediol is reacted with an aromatic dibasic acid such as terephthalic acid, isophthalic acid, or naphthalene dicarboxylic acid as essential raw material components.

Examples of polyester polyols include DIC Corporation (product name "Polylite (registered trademark)" series, etc.), Kuraray Co., Ltd. (product name "Kuraray Polyol (registered trademark)" series, etc.), Takeda Pharmaceutical Co., Ltd. (product name These products can be used.

Polyolefin polyols include polymers and copolymers of diolefins having 4 to 12 carbon atoms such as butadiene and isoprene, and copolymers of diolefins having 4 to 12 carbon atoms and α-olefins having 2 to 22 carbon atoms. Among polymers, it is a compound containing hydroxyl groups. The method for containing a hydroxyl group is not particularly limited, but for example, there is a method of reacting a double bond of a structure derived from a diene monomer after copolymerization with hydrogen peroxide. Furthermore, the remaining double bonds may be hydrogenated to make them saturated aliphatic. Examples of polyolefin polyols containing such hydroxyl groups include Nippon Soda Co., Ltd. (product name "NISSO-PB (registered trademark)" G series, etc.), Idemitsu Kosan Co., Ltd. (product name "Poly bd (registered trademark)") ” series, ``Epol (registered trademark)'' series, etc.), and these products can be used.

As the polycarbonate polyol, for example, a polycarbonate polyol obtained using only dialkyl carbonate and 1,6-hexanediol can be used, but since it has lower crystallinity, 1,6-hexanediol and 1,6-hexanediol are used as the diol. It is preferable to use a polycarbonate polyol obtained by copolymerizing 1,4-butanediol, 1,5-pentanediol, or 1,4-cyclohexanedimethanol.

Examples of the polycarbonate polyol include copolymerized polycarbonate polyols such as Asahi Kasei Chemicals Co., Ltd. (product name "T5650J", "T5652", "T4671", "T4672", etc.), Ube Industries Co., Ltd. (product name "ETERNACLL (registered trademark), etc.)" )"UM series, etc.), and these products can be used.

As the compound having an isocyanate group, a polyisocyanate compound having two or more isocyanate groups in the molecule is preferably used.

Examples of the polyisocyanate compound include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), phenylene diisocyanate, and xylene diisocyanate. Diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), cyclohexane diisocyanate, lysine ester triisocyanate, undecane triisocyanate, hexamethylene triisocyanate, triphenylmethane triisocyanate, and polymers, derivatives, and modified products of these isocyanate compounds. , hydrogenated products, etc. Among these, aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, and their polymers, derivatives, and modified products are preferably used because yellowing of the back layer is less likely to occur.

Examples of the above polyisocyanate compounds include Mitsui Chemicals Co., Ltd. (product name "Takenate (registered trademark)" series, etc.), Japan Polyurethane Industries, Ltd. (product name "Coronate (registered trademark)" series, etc.), Asahi Kasei Chemicals Co., Ltd. (trade name "Duranate (registered trademark)" series, etc.) and DIC Corporation (trade name "Burnock (registered trademark)" series, etc.), and these products can be used.

The embodiment (ii) above (thermosetting composition) will be explained in detail.

Examples of the compound having a hydroxyl group and a urethane bond include urethane polyol, urethane-modified (meth)acrylic polyol, urethane-modified polyester polyol, urethane-modified polyether polyol, urethane-modified polyolefin polyol, and urethane-modified polycarbonate polyol. Here, "urethane-modified (meth)acrylic polyol" is a general term for "urethane-modified acrylic polyol" and "urethane-modified methacrylic polyol."

Urethane polyols can be obtained, for example, by reacting a polyisocyanate compound with a compound having at least two hydroxyl groups in one molecule in such a ratio that the hydroxyl groups are in excess of the isocyanate groups. Examples of the polyisocyanate compound used in this case include the polyisocyanate compounds described above. Moreover, examples of compounds having at least two hydroxyl groups in one molecule include polyhydric alcohols, polyester diols, polyethylene glycols, polypropylene glycols, polycarbonate diols, and the like.

Examples of the urethane-modified (meth)acrylic polyol include those obtained by modifying the above-mentioned acrylic polyol with the above-mentioned polyisocyanate.

Examples of the urethane-modified polyether polyol include those obtained by modifying the above-mentioned polyether polyol with the above-mentioned polyisocyanate compound.

Examples of the urethane-modified polyolefin polyol include those obtained by modifying the aforementioned polyolefin polyol with the aforementioned polyisocyanate compound.

Examples of the urethane-modified polycarbonate polyol include those obtained by modifying the above-mentioned polycarbonate polyol with the above-mentioned polyisocyanate compound.

Among the above, urethane-modified (meth)acrylic polyols are preferred. As the urethane-modified (meth)acrylic polyol, "Acrit (registered trademark)" 8UA-146, 8UA-239, 8UA-347A, and 8UA-540H manufactured by Taisei Fine Chemical Co., Ltd. can be used.

Among the above-mentioned urethane-modified (meth)acrylic polyols, those having an acrylic polymer as the main chain and a side chain containing a urethane polymer having a polycarbonate group at the end and/or a urethane oligomer having a polycarbonate group at the end are more preferred. Commercially available products of such compounds include the above-mentioned "Acrit (registered trademark)" 8UA-347A and 8UA-540H.

As the compound having an isocyanate group, the same compounds as in the above embodiment (i) can be used.

Examples of the resin having a urethane bond used in the embodiment (iii) above include urethane resins and urethane-modified (meth)acrylic resins. Examples of urethane resins include KL-593 (trade name, manufactured by Arakawa Chemical Industries, Ltd.); examples of urethane-modified (meth)acrylic resins include AD-170 (trade name, manufactured by Hitachi Chemical Co., Ltd.); and AD-170 (trade name, manufactured by Taisei Fine Chemicals, Ltd.). Examples include "Acrit (registered trademark)" 8UA-443.

In the base film for transfer film of the present invention, acrylic and rubber-based resins having urethane bonds are generally used for the slightly adhesive layer of the protective film to be bonded to the back layer. Preferred are urethane-modified acrylic polyols, polyester polyols, and acrylic polyols because they tend to improve the adhesiveness of the adhesive.

The content of the resin having a urethane bond in the back layer is preferably 15 to 90% by mass, more preferably 20 to 70% by mass, particularly preferably 30 to 60% by mass based on 100% by mass of the total solid content of the back layer. .

The back layer can be obtained, for example, by applying the above-described composition (coating liquid) onto a polyester film by a wet coating method, drying it, and, if necessary, curing it by heating. Examples of such wet coating methods include reverse coating, spray coating, bar coating, gravure coating, rod coating, die coating, spin coating, extrusion coating, and curtain coating.

Preferably, the composition is a thermosetting composition. That is, the back layer is preferably formed by applying a thermosetting composition onto a polyester film, drying it, and curing it by heating.

The conditions (heating temperature, time) for curing the thermosetting composition are not particularly limited, but the heating temperature is preferably 70°C or higher, more preferably 100°C or higher, and particularly preferably 150°C or higher. The upper limit is about 300°C. The heating time is preferably 3 to 400 seconds, more preferably 5 to 300 seconds, and particularly preferably 10 to 200 seconds.

The back layer preferably contains a structure crosslinked with a crosslinking agent from the viewpoint of increasing membrane strength. Examples of the crosslinking agent include melamine compounds, epoxy compounds, isocyanate compounds, oxazoline compounds, carbodiimide compounds, and the like. Among these, melamine compounds are preferred. That is, in the base film for a transfer film of the present invention, it is preferable that the back layer contains a structure in which a melamine compound is crosslinked.

Melamine compounds used as crosslinking agents are so-called melamine [1,3,5-triazine-2,4,6-triamine], in which amino groups are bonded to each of the three carbon atoms of the triazine ring. A general term for modified compounds, including those with multiple condensed triazine rings.

As for the type of modification, a methylolated melamine compound in which at least one hydrogen atom of three amino groups is methylolated is preferable, and further, the methylol group of the methylolated melamine compound is partially modified with a lower alcohol having 1 to 4 carbon atoms. Preferred are alkyl etherified melamine compounds which are fully etherified. In particular, partially etherified alkyl etherified melamine compounds are preferred.

Examples of the alcohol used for etherification include methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol.

A commercially available melamine compound can be used as a crosslinking agent. Commercially available products include, for example, "Super Beckamine (registered trademark)" J-820-60, J-821-60, J-1090-65, J-110-60, J-J manufactured by DIC Corporation. -117-60, J-127-60, J-166-60B, J-105-60, G840, G821, Mitsui Chemicals' "Yuban (registered trademark)" 20SB, 20SE60, 21R, 22R, 122, 125, 128, 220, 225, 228, 28-60, 2020, 60R, 62, 62E, 360, 165, 166- 60, 169, 2061, “Sumimar (registered trademark)” by Sumitomo Chemical Co., Ltd. M-100, M-40S, M-55, M-66B, “Cymel (registered trademark)” by Nippon Cytec Industries "303, 325, 327, 350, 370, 235, 202, 238, 254, 272, 1130, Sanwa Chemical Co., Ltd.'s "Nikalac (registered trademark)" MS17, Examples include MX15, MX430, MX600, Vansemin SM-975 and SM-960 from Harima Kasei Co., Ltd., and Melan (registered trademark) 265 and 2650L from Hitachi Chemical Co., Ltd.

Examples of the epoxy compound include ethylene glycol diglycidyl ether, glycerol polyglycidyl ether, and polybutadiene diglycidyl ether.

Examples of oxazoline compounds include 2,2'-bis(2-oxazoline), 2,2'-ethylene-bis(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis Examples include compounds having an oxazoline group such as (2-oxazoline) and bis(2-oxazolinylcyclohexane) sulfide, and oxazoline group-containing polymers.

Examples of carbodiimide compounds include p-phenylene-bis(2,6-xylylcarbodiimide), tetramethylene-bis(t-butylcarbodiimide), and cyclohexane-1,4-bis(methylene-t-butylcarbodiimide). Examples include a compound having a carbodiimide group and polycarbodiimide, which is a polymer having a carbodiimide group.

The content of the crosslinking agent in the back layer is preferably 10 to 70% by weight, more preferably 20 to 60% by weight, particularly preferably 30 to 50% by weight based on 100% by weight of the total solid content of the back layer.

The back layer preferably contains an acid catalyst in combination with the above-mentioned crosslinking agent from the viewpoint of increasing membrane strength. Examples of the acid catalyst include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and p-toluenesulfonic acid.

When containing an acid catalyst, the content of the acid catalyst is preferably in the range of 1 to 20 parts by mass, more preferably in the range of 2 to 15 parts by mass, and more preferably in the range of 3 to 10 parts by mass, based on 100 parts by mass of the crosslinking agent. A range of is particularly preferred.

The thickness of the back layer is preferably 0.3 μm or more, more preferably 0.5 μm or more, and particularly preferably 1.0 μm or more from the viewpoint of improving the adhesiveness between the base film and the protective film. Furthermore, if the thickness of the back layer becomes too large, the base film will tend to curl, so the thickness is preferably 5.0 μm or less, more preferably 4.0 μm or less, and particularly preferably 3.0 μm or less.

[Polyester film]
The polyester constituting the polyester film is a general term for polymer compounds having ester bonds as the main bonds in the main chain. A polyester resin can usually be obtained by subjecting a dicarboxylic acid or a derivative thereof to a polycondensation reaction with a glycol or a derivative thereof.

Examples of dicarboxylic acids or derivatives thereof include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfonedicarboxylic acid, and the like. Aromatic dicarboxylic acids, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, aliphatic dicarboxylic acids such as fumaric acid, alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, paraoxybenzoic acid Oxycarboxylic acids such as and derivatives thereof can be mentioned. More specifically, dicarboxylic acid derivatives include dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, dimethyl 2,6-naphthalene dicarboxylate, dimethyl isophthalate, dimethyl adipate, diethyl maleate, Esterified products such as dimethyl dimerate can be mentioned.

Among the above, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and esterified products thereof are preferably used from the viewpoint of heat resistance and handleability. In particular, it is preferable to use at least terephthalic acid.

Examples of glycols or derivatives thereof include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1 , 6-hexanediol, aliphatic dihydroxy compounds such as neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, alicyclic compounds such as 1,4-cyclohexanedimethanol, spiroglycol, etc. Examples include dihydroxy compounds, aromatic dihydroxy compounds such as bisphenol A and bisphenol S, and derivatives thereof.

Among the above, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, polypropylene glycol, Polytetramethylene glycol is preferably used. In particular, it is preferable to use at least ethylene glycol.

The surface of the polyester film on which the transfer layer is laminated preferably has fine irregularities formed thereon from the viewpoint of imparting a matte appearance to the transfer layer. By forming the fine irregularities, the fine irregularities are transferred to the surface of the transfer layer laminated on that surface, and as a result, the transfer layer can be given a matte appearance. The degree of fine unevenness of the polyester film can be expressed by the arithmetic mean roughness Ra. That is, the arithmetic mean roughness Ra of the surface of the polyester film on which the transfer layer is laminated is preferably 0.30 μm or more, more preferably 0.35 μm or more, more preferably 0.40 μm or more, and particularly preferably 0.45 μm or more. . Further, from the viewpoint that the coating properties and peelability of the transfer layer tend to be good, the arithmetic mean roughness Ra is preferably 1.00 μm or less, more preferably 0.90 μm or less, and particularly preferably 0.80 μm or less.

In order to form fine irregularities on the surface of a polyester film, it is preferable that the polyester film has a two- or three-layer laminate structure and particles are contained in the outermost layer.

An example of a polyester film having a two-layer laminate structure is a layer A/layer B structure. In this configuration, it is preferable that the A layer contains particles in order to form fine irregularities on the surface of the A layer. In this case, a transfer layer is laminated on the surface of layer A.

Examples of the polyester film having a three-layer laminated structure include A layer/B layer/A layer or A layer/B layer/C layer. In these laminated structures, it is preferable that the layer A contains particles in order to form fine irregularities on the surface of the layer A. Then, a transfer layer is laminated on the surface of layer A. In the case of A layer/B layer/A layer, a transfer layer is laminated on the surface of one of the A layers.

In the two-layer laminated structure and the three-layer laminated structure described above, this means that the A layer, B layer, and C layer all have different compositions.

This means that the A layers on both sides in the laminated structure of A layer/B layer/A layer have at least the same composition. Furthermore, it is preferable that the A layers on both sides have substantially the same thickness. Here, the fact that the thicknesses of the A layers on both sides are substantially the same means that the ratio of the difference in thickness between the two A layers to the average thickness of the two A layers is 10% or less.

In the laminated structure of layer A/layer B/layer C, layer C may or may not contain particles.

Preferably, layer B does not contain particles. Here, particles refer to particles having an average particle diameter of 1 μm or more. That is, it is preferable that layer B does not contain particles having an average particle diameter of 1 μm or more. On the other hand, the B layer can contain a pigment having an average particle diameter of less than 1 μm, such as titanium dioxide and barium sulfate, for adjusting the color tone of the polyester film.

From the viewpoint of suppressing curling of the base film and the transfer film, it is preferable that the polyester film has a three-layer laminated structure. In addition, from the viewpoint of productivity, in the base film for transfer film of the present invention, it is more preferable that the polyester film has a three-layer laminate structure consisting of layer A/layer B/layer A, and in particular, the layer A on both sides. It is particularly preferred that the thicknesses are substantially the same.

Here, examples of particles that can be contained in the A layer include inorganic particles and organic particles. Examples of the inorganic particles include wet or dry silica, colloidal silica, aluminum silicate, calcium carbonate, calcium phosphate, and aluminum oxide. Examples of the organic particles include particles containing styrene, silicone, acrylic acids, methacrylic acids, polyesters, divinyl compounds, and the like as constituent components. These particles may be used alone or in combination of two or more.

Among the above particles, inorganic particles such as wet or dry silica, colloidal silica, and aluminum silicate, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene, and the like as constituent components are preferred. In particular, wet or dry silica, colloidal silica, and aluminum silicate are particularly preferably used from the viewpoint of efficiently forming fine irregularities on the surface of layer A.

The average particle diameter of the particles contained in layer A is preferably 1 to 10 μm, more preferably 2 to 8 μm, and particularly preferably 3 to 7 μm.

The content of particles in layer A is preferably 1 to 10% by weight, more preferably 2 to 8% by weight, particularly preferably 3 to 7% by weight based on 100% by weight of the total solid content of layer A.

The thickness of the polyester film is preferably 20 μm or more, more preferably 30 μm or more, and particularly preferably 40 μm. Moreover, from the viewpoint of processability, the thickness of the polyester film is preferably 150 μm or less, more preferably 100 μm or less, and particularly preferably 80 μm or less.

The thickness of layer A is preferably 1 to 10 μm, more preferably 2 to 8 μm, and 3 to 7 μm is particularly preferred.

The thickness of the C layer is preferably 1 to 10 μm, more preferably 2 to 8 μm, and particularly preferably 3 to 7 μm. The thickness of layer B is appropriately set depending on the total thickness of the polyester film.

In the two-layer laminated structure and the three-layer laminated structure described above, it is preferable that the A layer contains a polybutylene terephthalate resin from the viewpoint of improving the releasability between the A layer and the transfer layer. Among the above polybutylene terephthalate resins, copolymers of polybutylene terephthalate and polyether are more preferred. Furthermore, a copolymer using polytetramethylene glycol as the polyether is preferable.

Examples of the copolymer of polybutylene terephthalate and polytetramethylene glycol include product numbers 2751, 3046, 4047, 4767, and 7247 of Hytrel (registered trademark) manufactured by DuPont-Toray Co., Ltd. are commercially available and can be used.

The content of the polybutylene terephthalate resin in layer A is preferably 5 to 35% by weight, more preferably 8 to 30% by weight, particularly preferably 10 to 25% by weight based on 100% by weight of the total solid content of layer A.

A polyester film can be manufactured, for example, by supplying a polyester resin to a single screw extruder and melt-extruding it. The temperature of the polyester resin is controlled at 265°C to 295°C, and then foreign matter is removed through a filter or gear pump, and the amount of extrusion is balanced.Then, the resin is discharged into a sheet from a T-die onto a cooling drum, where it is cooled and solidified. An unstretched film can be obtained. At this time, it is preferable to employ an electrostatic application method in which the cooling drum and the polyester resin sheet are brought into close contact with each other by static electricity using electrodes to which a high voltage is applied.

The polyester film is preferably biaxially stretched from the viewpoint of heat resistance and dimensional stability. A biaxially stretched film can be obtained by a method of sequentially stretching an unstretched film in the longitudinal direction and the width direction, or a method of stretching an unstretched film in the longitudinal direction and the width direction almost simultaneously.

In the above stretching method, the stretching ratio in the longitudinal direction is preferably 2.8 to 3.4 times, more preferably 2.9 to 3.3 times. The stretching temperature in the longitudinal direction is preferably 70 to 100°C. The stretching ratio in the width direction is preferably 2.8 to 3.8 times, more preferably 3.0 to 3.6 times. The stretching temperature in the width direction is preferably 80 to 150°C.

Furthermore, it is preferable to perform heat treatment after biaxial stretching. This heat treatment is preferably carried out in an oven for 1 to 30 seconds while shrinking for a fixed length or sequentially. In this heat treatment step, it is preferable to set the temperature increase conditions in stages from the first half of the process, and it is preferable that the temperature in the first half of the heat treatment is -30 to -15°C higher than the temperature in the second half of the heat treatment, and the temperature in the second half of the heat treatment is 140 to 245 °C. .

The side of the polyester film on which the transfer layer is laminated is coated with a known release agent, such as a silicone release agent, a fluorine release agent, or a long-chain alkyl release agent, in order to improve releasability from the transfer layer. A mold release layer containing a mold agent and an olefin mold release agent can be provided. However, if a release layer is provided, problems such as a decrease in productivity and migration of a release component to the transfer layer may occur, so it is preferable not to provide a release layer. That is, in the base film for transfer film of the present invention, it is preferable that the transfer layer is directly laminated on the polyester film.

As mentioned above, by containing a polybutylene terephthalate resin in the outermost layer (for example, layer A) of the polyester film, the releasability from the transfer layer is improved, so it is not necessarily necessary to provide a release layer.

[Base film]
The base film of the present invention has a back layer on the side opposite to the side on which the transfer layer of the polyester film is laminated. As described above, when the polyester film has a two-layer laminated structure of layer A/layer B, the back layer is disposed on the surface of layer B. When the polyester film has a three-layer laminated structure of A layer/B layer/A layer, a back layer is disposed on one of the A layer surfaces. When the polyester film has a three-layer laminated structure of A layer/B layer/C layer, the back layer is arranged on the surface of the C layer. In particular, in the case of a three-layer laminated structure of layer A/layer B/layer A, the effect of the present invention (adhesion with the protective film) becomes remarkable.

In other words, if the polyester film has a three-layer laminated structure of layer A/layer B/layer A, and the arithmetic mean roughness Ra of the surface of layer A is 0.30 μm or more, or layer A contains polybutylene terephthalate resin. However, by providing a back layer on such a polyester film and using it as the base film of the present invention, the adhesiveness between the base film and the protective film can be improved. becomes good.

As the protective film bonded to the surface of the back layer of the base film, a polyester film or a polyolefin film provided with a slight adhesive layer on one side is generally used. Examples of such protective films include "PanaProtect (registered trademark)" manufactured by Panac Corporation and "Toretec (registered trademark)" manufactured by Toray Film Kako Co., Ltd.

The adhesion force between the base film and the protective film is, for example, preferably 0.15 N/50 mm or more, more preferably 0.20 N/50 mm or more, and particularly preferably 0.25 N/50 mm or more. The upper limit is about 1.0N/50mm.

[Application example]
The base film of the present invention is used for manufacturing a transfer film by laminating a transfer layer on one surface thereof. That is, in the transfer film of the present invention, a transfer layer is laminated on the surface opposite to the surface having the back layer of the base film for transfer film of the present invention. Examples of the transfer layer include a hard coat layer, a matte layer, a decorative layer, a protective layer, an insulating layer, a metal layer, a conductive layer, a hiding layer, an adhesive layer, and a conductive adhesive layer. These transfer layers may be a single layer or may have a laminated structure of two or more layers.

The transfer film to which the base film of the present invention is applied is suitable for producing electromagnetic shielding films for circuit boards such as flexible printed wiring boards. Electromagnetic shielding films are usually composed of an insulating layer, a metal layer, a conductive adhesive layer, and the like. It is preferable that the insulating layer serves as both a hard coat layer and a matte layer.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited only to these Examples.

[Measurement method and evaluation method]
(1) Measurement of arithmetic mean roughness Ra of polyester film It was measured using a surface roughness measuring machine ("Surf Test SJ-400" manufactured by Mitutoyo Co., Ltd.) in accordance with JIS B0601 (2001).
<Measurement conditions>
・Stylus tip radius: 2μm
・Measurement force: 0.75mN
・Cutoff value; λc=0.8mm
・Measurement speed: 0.5mm/sec ・Measurement length: 4mm
(2) Evaluation of adhesion between the base film and the protective film Cut the base film into a piece of 50 mm wide x 70 mm long, and attach the protective film (Toray ``Toretech (registered trademark)'' 7332) manufactured by Film Kako Co., Ltd. was stacked so that the adhesive sides faced each other, and was bonded together by moving it back and forth once while pressing with a rubber roller weighing 5 kg. A sample for measurement was prepared by leaving it for a certain period of time. For this measurement sample, the peeling force was measured when the protective film side was peeled off at 180° at a speed of 300 mm/min using a tensile tester (product number "EZ-SX" manufactured by Shimadzu Corporation).

<Evaluation of adhesion>
A: Peeling force is 0.25 N/50 mm or more B: Peeling force is 0.15 N/50 mm or more and less than 0.25 N/50 mm C: Peeling force is less than 0.15 N/50 mm.

(3) Evaluation of adhesion between polyester film and back layer Apply rubber adhesive tape (Nichiban Co., Ltd. "Cello Tape (registered trademark)" No. 405 (industrial use)) to the back layer surface of the base film using finger pressure. After strongly bonding, the adhesive tape side was rapidly peeled off at an angle of 175°, and the state of detachment of the back layer was visually confirmed. The adhesive area between the back layer and the adhesive tape was 25 mm wide x 200 mm long.
A: Not peeled off at all B: Partially peeled off C: The entire surface peeled off.

(4) Measurement of the average particle diameter of particles contained in the polyester film The cross section of the polyester film was observed with an electron microscope, and from the photograph of the cross section, the maximum length of each of 30 randomly selected particles was measured. The average value of these values was defined as the average particle diameter of the particles.

[Example 1]
<Preparation of polyester resin used for manufacturing polyester film>
<Polyester resin a>
Polymerization was carried out from terephthalic acid and ethylene glycol using antimony trioxide as a catalyst in a conventional manner to obtain a polyester resin with an intrinsic viscosity of 0.65.

<Polyester resin b>
A polyethylene terephthalate particle master having an intrinsic viscosity of 0.65 was prepared by containing aggregated silica particles having an average particle diameter of 3.5 μm at a particle concentration of 20% by mass in the above polyester resin a.

<Polyester resin c>
As a copolymer of polybutylene terephthalate and polytetramethylene glycol, "Hytrel (registered trademark)" 7247 manufactured by DuPont-Toray Co., Ltd. was used.

<Polyester resin d>
A polyethylene terephthalate particle master having an intrinsic viscosity of 0.6 was prepared by containing 50% by mass of anatase type titanium dioxide in the polyester resin a.

<Manufacture of polyester film 1>
Using the following A-layer resin composition and B-layer resin composition, a polyester film having a three-layer laminated structure consisting of A layer/B layer/A layer was manufactured in the following manner.

A layer resin composition: Contains 58% by mass of polyester resin a, 25% by mass of polyester resin b, and 17% by mass of polyester resin c.

B layer resin composition: Contains 80% by mass of polyester resin a, 17% by mass of polyester resin c, and 3% by mass of polyester resin d.

The raw materials for layer A and layer B were each supplied to separate single screw extruders with an oxygen concentration of 0.2% by volume, and melted at a cylinder temperature of 270°C for layer A and 270°C for layer B. After the A layer and the B layer were combined, the short tube temperature was set at 275° C., the die temperature was set at 280° C., and the resin was discharged in a sheet form from a T-die onto a cooling drum whose temperature was controlled at 25° C. at a resin temperature of 280° C. At that time, electrostatic charge was applied using a wire-shaped electrode with a diameter of 0.1 mm, and the unstretched sheet was obtained by closely contacting the cooling drum. Next, before stretching in the longitudinal direction, the film temperature was raised with a heating roll, and the film was stretched 3.1 times in the longitudinal direction at a stretching temperature of 85°C, and immediately cooled with a metal roll whose temperature was controlled at 40°C. Thereafter, it was stretched 3.5 times in the width direction using a tenter-type horizontal stretching machine at a temperature of 110°C in the first half of stretching, a temperature of 125°C in the middle of stretching, and a temperature of 140°C in the latter half of stretching, and then heat-treated at 220°C in the first half and heat-treated in the second half in the tenter. After heat treatment at 240°C, heat treatment was performed at an annealing temperature of 170°C while relaxing 5% in the width direction to obtain a biaxially stretched polyester film with a total thickness of 50 μm. The thicknesses of layer A/layer B/layer A were 5 μm/40 μm/5 μm. The arithmetic mean roughness Ra of the surface of layer A was 0.55 μm on both surfaces.

<Lamination of back layer>
On one side of the polyester film 1 produced above, the following back layer coating liquid p1 (thermosetting composition) was applied using a gravure coater, and dried and heated at 170°C for 30 seconds to coat the back layer. A base film was obtained. The thickness of the back layer was 1.8 μm.

<Coating liquid p1>
・Urethane-modified acrylic polyol: 10 parts by mass of “Acrit (registered trademark)” 8UA-540H manufactured by Taisei Fine Chemical Co., Ltd. in terms of solid content ・Polyisocyanate compound: Hexamethylene diisocyanate (“Takenate” manufactured by Mitsui Chemicals, Inc.) 4.7 parts by mass of “D-160N” (registered trademark)
・Crosslinking agent: 10 parts by mass of melamine compound (“Yuban” 28-60 by Mitsui Chemicals, Inc.) in terms of solid content ・Acid catalyst: p-toluenesulfonic acid (“TAYCACURE” AC-707 by Teika Co., Ltd.) 0.7 parts by mass in terms of solid content / solvent; mixed solvent (toluene: methyl ethyl ketone: isopropyl alcohol: cyclohexanone = 40:40:10:10 (mass ratio)) was prepared so that the solid content concentration was 20 mass%. .

[Example 2]
A base film was produced in the same manner as in Example 1, except for changing to the following coating liquid p2 (thermosetting composition).

<Coating liquid p2>
・Polyester polyol: 10 parts by mass of “Polyester (registered trademark)” TP-235S20TM manufactured by Mitsubishi Chemical Corporation in terms of solid content ・Polyisocyanate compound: diphenylmethane diisocyanate (“Takenate (registered trademark)” manufactured by Mitsui Chemicals, Inc.) )"D-103H) 4.7 parts by mass of crosslinking agent; 10 parts by mass of melamine compound ("Yuban" 28-60 by Mitsui Chemicals, Inc.) in terms of solid content; acid catalyst; p-toluenesulfonic acid ( "TAYCACURE" AC-707) by TAYCA Co., Ltd. was mixed with 0.7 parts by mass in terms of solid content, solvent; mixed solvent (toluene: methyl ethyl ketone: isopropyl alcohol: cyclohexanone = 40:40:10:10 (mass ratio)). The concentration was adjusted to 20% by mass.

[Example 3]
A base film was produced in the same manner as in Example 1, except for changing to the following coating liquid p3 (thermosetting composition).

<Coating liquid p3>
・Acrylic polyol: 10 parts by mass of “Takelac (registered trademark)” UA-702 manufactured by Mitsui Chemicals, Inc. in terms of solid content ・Polyisocyanate compound: 4 parts of tolylene diisocyanate (Coronate L manufactured by Nippon Polyurethane Industries, Ltd.) .7 parts by mass / Crosslinking agent: 10 parts by mass of melamine compound ("Yuban" 28-60, manufactured by Mitsui Chemicals, Inc.) in terms of solid content. - Acid catalyst: p-toluenesulfonic acid ("TAYCACURE", manufactured by Teika Co., Ltd.) AC-707) in terms of solid content, 0.7 parts by mass / solvent; mixed solvent (toluene: methyl ethyl ketone: isopropyl alcohol: cyclohexanone = 40:40:10:10 (mass ratio), the solid content concentration becomes 20 mass %) Prepared as follows.

[Comparative example 1]
The polyester film 1 was used as a base film without providing a back layer on the polyester film 1.

[Comparative example 2]
A base film was produced in the same manner as in Example 1, except for changing to the following coating liquid p4 (thermosetting composition).

<Coating liquid p4>
・Polyester polyol: 10 parts by mass of “Polyester (registered trademark)” TP-235S20TM manufactured by Mitsubishi Chemical Corporation in terms of solid content ・Crosslinking agent: Melamine compound (“Yuban” 28-60 of Mitsui Chemicals, Inc.) 10 parts by mass in terms of solid content / acid catalyst; 0.7 parts by mass in terms of solid content of p-toluenesulfonic acid (TAYCACURE AC-707 by Teika Co., Ltd.); solvent; mixed solvent (toluene: methyl ethyl ketone: It was prepared by using isopropyl alcohol:cyclohexanone=40:40:10:10 (mass ratio) so that the solid content concentration was 20% by mass.

[Comparative example 3]
A base film was produced in the same manner as in Example 1, except for changing to the following coating liquid p5 (thermosetting composition).

<Coating liquid p5>
・Acrylic polyol: 10 parts by mass of “Takelac (registered trademark)” UA-702 manufactured by Mitsui Chemicals, Inc. in terms of solid content ・Crosslinking agent: Melamine compound (“Yuban” 28-60 of Mitsui Chemicals, Inc.) 10 parts by mass in terms of solid content / Acid catalyst; 0.7 parts by mass in terms of solid content of p-toluenesulfonic acid (TAYCACURE AC-707 by Teika Co., Ltd.) Solvent; Mixed solvent (toluene: methyl ethyl ketone: isopropyl) Alcohol: cyclohexanone = 40:40:10:10 (mass ratio) and the solid content concentration was adjusted to 20% by mass.

[evaluation]
The base films of Examples and Comparative Examples produced above were evaluated according to the measurement method and evaluation method described above. The results are shown in Table 1.

Claims (6)

A base film for a transfer film for laminating a transfer layer on one side of the base film, comprising a polyester film and a resin having a urethane bond on the opposite side of the polyester film to the side on which the transfer layer is laminated. having a back layer containing;
A base film for a transfer film, wherein the surface of the polyester film on which the transfer layer is laminated has an arithmetic mean roughness Ra of 0.30 μm or more . A base film for a transfer film for laminating a transfer layer on one side of the base film, comprising a polyester film and a resin having a urethane bond on the opposite side of the polyester film to the side on which the transfer layer is laminated. having a back layer containing;
A base film for a transfer film, wherein the polyester film has a three-layer laminated structure consisting of layer A/layer B/layer A. The base film for a transfer film according to claim 1 or 2 , wherein the back layer contains a structure in which a melamine compound is crosslinked. The base film for a transfer film according to claim 2 or 3 , wherein the surface of the polyester film on which the transfer layer is laminated has an arithmetic mean roughness Ra of 0.30 μm or more. The base film for a transfer film according to claim 3 or 4 , wherein the polyester film has a three-layer laminated structure consisting of layer A/layer B/layer A. A transfer film comprising a transfer layer laminated on the surface opposite to the surface having the back layer of the base film for transfer film according to any one of claims 1 to 5 .