Patent Description:
In recent years, fiber reinforced resin molded articles have been widely proposed as a member of sporting goods, automobiles, ships, aircrafts, or the like that receive large impact or deformation stress, and are positively employed particularly in fields requiring light weight and high mechanical properties. For example, a carbon fiber reinforced resin molded article is produced by impregnating carbon fibers with a resin (hereinafter, also referred to as a "matrix resin") constituting a fiber impregnated resin such as a thermoplastic resin or a thermosetting resin and curing the resin as necessary. Since the carbon fiber reinforced resin molded article produced in this manner is reinforced with carbon fibers, the carbon fiber reinforced resin molded article has significantly improved physical properties and is a lightweight and tough member.

The above-described fiber reinforced resin molded article causes an unevenness on a surface of the fiber reinforced resin molded article, which reflects a texture or stitch of fabric, knitting, or the like, and it is difficult to obtain a smooth surface.

As a technique by which a fiber reinforced plastic member having a smooth surface can be obtained without impairing characteristics of the fiber reinforced plastic which is lightweight, for example, a fiber reinforced plastic member is disclosed, which includes the following constituent elements: [A] fiber reinforced plastic containing fabric or knitting of a reinforced fiber and a thermosetting resin; [B] a low elastic modulus surface layer having a tensile elastic modulus of <NUM> MPa to <NUM> MPa; and [C] a high elastic modulus surface layer having a tensile elastic modulus of <NUM> MPa to <NUM> MPa, in which the constituent element [C] is disposed via the constituent element [B] on at least one side of the constituent element [A] (see, for example, Patent Literature <NUM>).

Further, as a method of efficiently obtaining a thermoplastic carbon fiber composite material in which adhesion is good, a carbon fiber pattern can be concealed, and which has improved design, for example, a method for producing a thermoplastic carbon fiber composite material having a film is disclosed, which includes: <NUM>) a step of obtaining a molded article made of a thermoplastic carbon fiber composite material by using a mold whose surface temperature is <NUM> or higher and <NUM> or lower; and <NUM>) a film forming step of forming a film on a surface of the obtained molded article, in which <NUM>) the step of obtaining a molded article is hot press molding, and in <NUM>) the film forming step, in-mold coating paint added with an initiator is injected into a mold and cured, the initiator having a half-life at <NUM> of one second or more and <NUM> seconds or less (see, for example, Patent Literature <NUM>).

<CIT> discloses a glass fiber reinforced polypropylene resin sheet as a core layer was laminated on both sides of the core layer with a rubber polyester film laminate so that the rubber layer side of the rubber polyester film laminate was on the side of the core layer.

In the fiber reinforced resin molded article described in Patent Literature <NUM>, in order to conceal an uneven pattern such as a texture or stitch of fibers or color, it is necessary to perform painting repeatedly after undercoating. Further, since bubbles are easily mixed into the above-described uneven pattern and productivity is poor, there is a demand for further improvement of the method for producing a thermoplastic carbon fiber composite material described in Patent Literature <NUM>.

The present invention has been made in view of the above, and an object of the present invention is to provide a surface coating film excellent in image clarity when integrally molded with a fiber impregnated resin and a surface-coated fiber-reinforced resin molded article obtained by integrally molding the surface coating film and a fiber impregnated resin, and a method of producing the same.

Another object of the present invention is to provide a surface coating film having excellent glossiness when integrally molded with a fiber impregnated resin and a surface-coated fiber-reinforced resin molded article obtained by integrally molding the surface coating film with a fiber impregnated resin, and a method of producing the same.

As a result of intensive studies to solve the above problem, the present inventors have found that a surface coating film has an excellent image clarity even when the surface coating film is integrally molded with a fiber impregnated resin, the surface coating film including a base material film B having a specific thickness and an easily adhesive layer A provided on the base material film B, the base material film B including an easily molded layer b1 adjacent to easily adhesive layer A and a flat layer b2, in which storage modulus of each of the easily molded layer b1 and the flat layer b2 satisfies a specific relationship, and the easily adhesive layer A has a specific thickness.

That is, for solbving the above problem the present invention provides a surface coating film for integral molding with a fiber impregnated resin according to claim <NUM>, a surface-coated fiber-reinforced resin molded article according to claim <NUM>, and a method for producing a surface-coated fiber-reinforced resin molded article according to claim <NUM>.

According to an embodiment of the present invention, a surface coating film having excellent image clarity when integrally molded with a fiber impregnated resin and a surface-coated fiber-reinforced resin molded article obtained by integrally molding the surface coating film and a fiber impregnated resin, and a method of producing the same are provided.

According to another embodiment of the present invention, a surface coating film having excellent glossiness when integrally molded with a fiber impregnated resin and a surface-coated fiber-reinforced resin molded article obtained by integrally molding the surface coating film and a fiber impregnated resin, and a method of producing the same are provided.

<FIG> is a schematic diagram of a configuration of a surface-coated fiber-reinforced resin molded article which is an embodiment of the present invention.

Hereinafter, contents of the present invention will be described in detail. Description of constituent requirements to be described below may be made based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

In the present description, "to" indicating a numerical range is used in a sense including numerical values described before and after it as a lower limit value and an upper limit value.

In addition, in a description of a group (atom group) in the present description, a description not noting substituted or unsubstituted includes those having no substituent and those having a substituent. For example, an "alkyl group" includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

In the present description, "(meth)acryl" is a term used in a concept containing both acryl and methacryl, and "(meth)acryloyl" is a term used as a concept containing both acryloyl and methacryloyl.

A term "step" in the present description includes not only an independent step, and but also a step which cannot be clearly distinguished from other steps if the intended purpose of the step is achieved.

In the present invention, "mass%" and "weight%" are synonymous, and "part by mass" and "part by weight" are synonymous.

Unless otherwise specified, each component in a composition or each constituent unit in a polymer may be contained alone or in combination of two or more in the present invention.

Further, in the present invention, the amount of each component in the composition or each constituent unit in the polymer means a total amount of a plurality of corresponding substances present in the composition or a plurality of corresponding constituent units present in the polymer unless otherwise specified when there are a plurality of substances or constituent units corresponding to each component in the composition or each constituent unit in the polymer.

In the present invention, a combination of two or more preferable embodiments is a more preferable embodiment.

In the present description, "image clarity" can be evaluated by visually observing a surface of the surface coating film under a fluorescent lamp and distortion of a reflected image of a fluorescent lamp projected on the surface of the surface coating film in an integrally molded article of the fiber impregnated resin and the surface coating film. The more clearly details of a contour, a shape, or the like of the reflected image of the fluorescent lamp are projected, the better the image clarity is.

In the present description, "glossiness" can be evaluated by measuring a <NUM>° gloss value (hereinafter also referred to as "glossiness/<NUM>°") of the surface coating film surface in the integrally molded article of the fiber impregnated resin and the surface coating film. The higher the value of the glossiness/<NUM>°, the better the glossiness is.

Hereinafter, the surface coating film and a surface-coated fiber-reinforced resin molded article, and a method for producing the same according to the present invention will be described.

A surface coating film for integrally molding with a fiber impregnated resin according to the present invention includes.

As a result of intensive studies by the present inventors, it has been found that a surface coating film having excellent image clarity when integrally molded with the fiber impregnated resin (hereinafter, also simply referred to as "image clarity") can be obtained by adopting the above configuration. Further, it has been found that when the surface-coated fiber-reinforced resin molded article is molded using the surface coating film and a fiber impregnated resin to be described later, it is possible to obtain the surface-coated fiber-reinforced resin molded article which can be integrally molded with good productivity and can obtain design and surface planarization even without painting or the like.

A detailed mechanism by which the above effect can be obtained is unclear, but is presumed as follows.

When the fiber impregnated resin is subjected to surface processing, there is a concern that unevenness may occur on the surface due to curing shrinkage of a resin (matrix resin) constituting the fiber impregnated resin and/or a thermal expansion difference (hereinafter, also referred to as "sink mark of fiber impregnated resin") between the matrix resin and the fiber. Unevenness adjustment such as polishing, filling with putty, and application of surfacer is performed for processing of surface unevenness, and as surface finishing, an easily adhesive film, a rigid film, or the like are laminated for a design and to impart durability. In the integrally molded article with the fiber impregnated resin obtained by such a surface treatment, reflection at an interface between the fiber impregnated resin and the easily adhesive film remains, and a reflected image can be seen askew, so that improvement of image clarity is required.

The present inventors have found out that, when the easily molded layer b <NUM> constituting the base material film B has a storage modulus at <NUM> of a specific numerical value or more, the easily molded layer b <NUM> has appropriate flexibility and hardness, and has excellent adhesion to the easily adhesive layer A, and the surface coating film containing the easily molded layer b <NUM> and the easily adhesive layer A has image clarity.

Further, by setting the ratio of the storage modulus of the easily molded layer b <NUM> to the storage modulus of the flat layer b2 to the range defined in the above formula <NUM> at <NUM>, the easily molded layer b <NUM> alleviates deformation of the matrix resin due to curing shrinkage or thermal expansion difference when integrally molded with the above fiber impregnated resin , and unevenness derived from the fiber impregnated resin due to deformation of the matrix resin is difficult to influence a surface shape of an outermost layer by having the flat layer b2, and as a result, it is inferred that the surface coating film according to the present invention has excellent image clarity.

Since the easily molded layer b <NUM> has a certain degree of hardness at normal temperature, it is considered that handling during integral molding is good and scratches (hereinafter also referred to as "damage") of the surface coating film are easily reduced. In addition, since the surface coating film according to the present invention includes the easily adhesive layer A, it is inferred that the easily molded layer b <NUM> and the matrix resin can be caused to firmly adhere to each other and image clarity is excellent.

Hereinafter, each configuration of the coating film according to the present invention will be described below.

The surface coating film according to the present invention includes the base material film B and the easily adhesive layer A provided on the base material film B, the base material film B including the easily molded layer b <NUM> adjacent to the easily adhesive layer A and the flat layer b2, in which the base material film B has a thickness of <NUM> to <NUM>.

The thickness of the base material film B is a total distance in the thickness direction of a multilayer including the easily molded layer b1 adjacent to the easily adhesive layer A, the flat layer b2, and the other layer (the oher layer b3 to be described later) except the easily molded layer b <NUM> and the flat layer b2 provided according to cases.

When the thickness of the base material film B is in a range of <NUM> to <NUM>, processability when integrally molded with a fiber impregnated resin to be described later is excellent, and flatness of the surface coating film is excellent when coated on a surface of a fiber impregnated resin to be described later.

From the above viewpoints, the thickness of the base material film B is preferably <NUM> or more, more preferably <NUM> or more, and even more preferably <NUM> or more. From the above viewpoints, the thickness of the base material film B is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, further more preferably <NUM> or less, particularly preferably <NUM> or less, and extremely preferably less than <NUM>.

The thickness of the base material film B can be determined from an image obtained by observing a cross section of the base material film B with a stereomicroscope and a scale.

In view of achieving both moldability and flatness in the integral molding, the base material film B is preferably a biaxially oriented film in which a molecular chain is oriented in two directions orthogonal to each other in the plane by stretching the film.

The base material film B used in the present invention includes the easily molded layer b1 adjacent to the easily adhesive layer A.

The easily molded layer b1 satisfies the following formula <NUM>. When the easily molded layer b1 satisfies the formula <NUM>, that is, when the storage modulus ELb1 of the easily molded layer b1 at <NUM> is <NUM> MPa or more, it is considered that the easily molded layer b1 has an appropriate softness, the moderate softness improves the adhesion to the easily adhesive layer A to be described later, and the softness and the adhesion are combined so that the surface coating film has excellent image clarity. In addition, when the easily molded layer b1 satisfies the formula <NUM>, handling during integral molding is good, and damage is easily reduced.

In view of excellent image clarity, the storage modulus ELb1 at <NUM> is preferably <NUM> MPa or more, preferably <NUM> MPa or more and less than <NUM> MPa, more preferably <NUM> MPa to <NUM> MPa, and even more preferably <NUM> MPa to <NUM> MPa.

The storage modulus ELb1 of the easily molded layer b <NUM> at <NUM> is measured using a dynamic viscoelasticity measurement device (product name: DMA8000, manufactured by PerkinElmer) while pulling the easily molded layer b1 in a MD direction with a tension jig at a frequency of <NUM> and raising temperature. From the measurement results, the storage modulus at <NUM> can be obtained.

In the present description, the "MD direction" means a machine direction of a film, that is, a longitudinal direction.

In view of image clarity, the easily molded layer b <NUM> preferably further satisfies the following formula <NUM>.

The storage modulus EHb1 of the easily molded layer b <NUM> at <NUM> can be obtained by the same method as the storage modulus ELb1 of the easily molded layer b1 at <NUM>.

In view of image clarity, the storage modulus EHb1 of the easily molded layer b1 at <NUM> is preferably <NUM> MPa to <NUM> MPa, and more preferably <NUM> MPa to <NUM> MPa.

The easily molded layer b1 and the flat layer b2 to be described later satisfy the following formula <NUM>. Since the easily molded layer b1 and the flat layer b2 satisfy the following formula <NUM>, the curing shrinkage and thermal expansion difference of the matrix resin are alleviated in the thickness direction at a processing temperature during the integral molding, and the image clarity is excellent.

In view of excellent image clarity, EHb2/EHb <NUM> is <NUM> or more, preferably <NUM> or more, more preferably <NUM> or more, and even more preferably <NUM> or more. In view of handling, EHb2/EHb1 is preferably <NUM> or less, more preferably <NUM> or less, and still more preferably <NUM> or less. In addition, in view of ensuring higher image clarity and moderate handleability, EHb2/EHb1 is preferably in a range of <NUM> to <NUM>. On the other hand, in view of ensuring high handleability while maintaining image clarity to some extent, EHb2/EHb1 is preferably in a range of <NUM> to <NUM>.

The storage modulus EHb2 of the flat layer b2 at <NUM> can be obtained by the same method as the storage modulus ELb <NUM> of the easily molded layer b <NUM> at <NUM>.

The easily molded layer b1 is preferably a layer containing a thermoplastic resin. As the layer containing a thermoplastic resin, a resin film made of a thermoplastic resin can be suitably used.

The thermoplastic resin used in the easily molded layer b1 may be used in one kind alone or in combination of two or more kinds thereof.

The thermoplastic resin is not particularly limited as long as it can be molded into a film or a sheet.

As the specific thermoplastic resin, those publicly known per se can be used, such as: polyolefin resins such as polyethylene, polypropylene, and poly(<NUM>-methyl pentene-<NUM>); cycloolefins such as a ring-opened metathesis polymer, an addition polymer, and an addition copolymer with other olefins of norbornenes; biodegradable polymers such as polylactic acid and polybutylene succinate; polyamide resins (including semi-aromatic polyamides) such as nylons <NUM>, <NUM>, <NUM>, and <NUM>; polymethyl methacrylate; polyvinyl chloride; polyvinylidene chloride; polyvinyl alcohol; polyvinyl butyral; ethylene vinyl acetate copolymer; polyacetal; polyglycolic acid; polystyrene; styrene copolymerized polymethyl methacrylate; polycarbonate; polyester resins such as polypropylene terephthalate, polyethylene terephthalate (PET), polyethylene isophthalate (IAPET), polybutylene terephthalate (PBT), and polyethylene-<NUM>,<NUM>-naphthalate (PEN); polyethersulfone; polyetherketone; modified polyphenylene ether; polyphenylene sulfide; polyetherimide; polyimide; polyarylate; a tetrafluoroethylene-hexafluoropropylene copolymer; polyvinylidene fluoride; and an acrylonitrile-butadiene-styrene copolymer.

Among these, since flatness is more easily revealed and transparency that contributes to glossiness is easily imparted when the surface of the fiber impregnated resin is coated, the thermoplastic resin is preferably at least one resin selected from the group consisting of a polymethyl methacrylate resin, a polycarbonate resin, and a polyester resin, and particularly more preferably a polyester resin since it is easy to provide flatness by stretching or the like.

These resins may be a homopolymer, a copolymer (copolymerization polymer), or a mixture of thermoplastic resins.

The thermoplastic resin may be, for example, a thermoplastic resin composition obtained by adding additives such as an antioxidant, an antistatic agent, a crystal nucleating agent, an inorganic particle, an organic particle, a viscosity-reducing agent, a heat stabilizer, a lubricant, an infrared absorber, an ultraviolet absorber, and a doping agent for adjusting a refractive index.

When the polyester resin is used as the thermoplastic resin, examples of the polyester resin preferably include a polyester resin obtained by polymerization of a monomer synthesized from: an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid or an ester-forming derivative thereof; and a diol or an ester-forming derivative thereof, and those known per se can be used.

The aromatic dicarboxylic acid is not particularly limited, and examples thereof include terephthalic acid, isophthalic acid, phthalic acid, <NUM>,<NUM>-naphthalene dicarboxylic acid, <NUM>,<NUM>-naphthalene dicarboxylic acid, <NUM>,<NUM>-naphthalene dicarboxylic acid, <NUM>,<NUM>'-diphenyl dicarboxylic acid, <NUM>,<NUM>'-diphenylsulfone dicarboxylic acid, <NUM>,<NUM>'-diphenyl dicarboxylic acid, <NUM>,<NUM>-furan dicarboxylic acid, and ester-forming derivatives thereof.

The aliphatic dicarboxylic acid is not particularly limited, and examples thereof include adipic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexane dicarboxylic acid, and ester-forming derivatives thereof.

Among these, the dicarboxylic acid used in the polyester resin is preferably an aromatic dicarboxylic acid, and more preferably terephthalic acid, isophthalic acid, <NUM>,<NUM>-naphthalene dicarboxylic acid, or ester-forming derivatives thereof since it is possible to have excellent heat resistance and flatness after integral molding.

These acid components may be used in one kind alone or in combination of two or more kinds thereof, and may be partially copolymerized with an oxyacid of hydroxybenzoic acid or the like.

Examples of the diol include ethylene glycol, <NUM>,<NUM>-propanediol, <NUM>,<NUM>-propanediol, neopentyl glycol, <NUM>,<NUM>-butanediol, <NUM>,<NUM>-butanediol, <NUM>,<NUM>-pentanediol, <NUM>,<NUM>-hexanediol, <NUM>,<NUM>-cyclohexane dimethanol, <NUM>,<NUM>-cyclohexane dimethanol, <NUM>,<NUM>-cyclohexane dimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, <NUM>,<NUM>-bis(<NUM>-hydroxy ethoxy phenyl) propane, isosorbide, spiroglycol, and ester-forming derivatives thereof.

Among these, the diol is preferably at least one diol selected from the group consisting of ethylene glycol, <NUM>,<NUM>-butanediol and <NUM>,<NUM>-butanediol, and ester-forming derivatives thereof since it is possible to have excellent heat resistance and flatness after integral molding.

These diol components may be used in one kind alone or in combination of two or more kinds thereof.

When the polyester resin is used as the thermoplastic resin, in view of achieving both moldability and flatness, the polyester resin is preferably a polyester resin having a constituent unit derived from at least one monomer selected from the group consisting of ethylene terephthalate, ethylene isophthalate, ethylene naphthalene dicarboxylate, butylene terephthalate, butylene naphthalene dicarboxylate, hexamethylene terephthalate, hexamethylene naphthalene dicarboxylate, <NUM>,<NUM>-cyclohexane dimethylene terephthalate, ethylene furanoate, and <NUM>,<NUM>-cyclohexane dimethylene naphthalene dicarboxylate, and more preferably a polyester resin having a constituent unit derived from at least one monomer selected from the group consisting of ethylene terephthalate, butylene terephthalate, and ethylene isophthalate.

The polyester resin is not limited to a homopolymer of the monomer, but may be a copolymer using two or more of the monomers or a mixture of two or more polyester resins.

In view of moldability during the integral molding and image clarity, the polyester resin is preferably a mixture of two or more polyester resins, more preferably a mixture containing at least two kinds selected from the group consisting of polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate, and further more preferably a mixture of polyethylene isophthalate and polybutylene terephthalate.

In view of excellent moldability during the integral molding, the polyester resin is preferably a polyester resin having a constituent unit derived from at least one selected from the group consisting of butylene terephthalate and ethylene isophthalate.

In particular, since moldability during the integral molding is excellent, it is particularly preferable that the polyester resin is obtained by copolymerizing <NUM> mol% or more of the constituent unit derived from butylene terephthalate and ethylene isophthalate and <NUM> mol% to <NUM> mol% of constituent units derived from monomers other than butylene terephthalate and ethylene isophthalate with respect to all constituent units constituting the polyester resin based on the number of moles.

A weight average molecular weight of the thermoplastic resin used in the easily molded layer b1 is preferably <NUM>,<NUM> to <NUM>,<NUM>, more preferably <NUM>,<NUM> to <NUM>,<NUM>.

The weight average molecular weight can be obtained by the following measurement method.

A thermoplastic resin sample is frozen and crushed, and <NUM> of the sample is dissolved overnight in <NUM> of a mixed solvent of hexafluoro isopropanol (HFIP) : chloroform = <NUM>: <NUM>, the solution is diluted with <NUM> of chloroform and then filtrated by a <NUM> membrane filter to obtain a measurement solution.

The measurement solution produced by the above method is measured with a gel permeation chromatography (GPC) analysis apparatus under the following conditions. The weight average molecular weight was calculated as a conversion value of standard polystyrene. Device name: model number: HLC-8320GPC manufactured by Tosoh Corporation.

The easily molded layer b1 may contain a colorant in addition to the thermoplastic resin. Examples of the colorant include a colorant used in a decorative layer to be described later.

A thickness of the easily molded layer b1 is preferably <NUM> or more, more preferably <NUM> or more, still more preferably <NUM> or more, even more preferably <NUM> or more, and particularly preferably <NUM> or more since it is easy to make a layer having sufficient hardness and strength. The thickness of the easily molded layer b1 is preferably <NUM> or less, more preferably <NUM> or less, still more preferably <NUM> or less, and even more preferably <NUM> or less since it is easy to make a layer having necessary softness.

The base material film B used in the present invention includes a flat layer b2, and the flat layer b2 satisfies the above formula <NUM>. The flat layer b2 is preferably a layer provided on the described easily molded layer b1, and more preferably a layer provided on the easily molded layer b1 and adjacent to the easily molded layer b1.

When the flat layer b2 is an outermost layer of the surface coating film, it may function as a protective layer.

The flat layer b2 is preferably a layer containing a thermoplastic resin in view of maintaining durability while expressing design of a texture.

The thermoplastic resin used in the flat layer b2 has the same meaning as the thermoplastic resin in the described easily molded layer b1.

Since flatness is more easily revealed and transparency that contributes to glossiness is easily imparted when the surface of the fiber impregnated resin is coated, the thermoplastic resin used in the flat layer b2 is preferably at least one resin selected from the group consisting of a polymethyl methacrylate resin, a polycarbonate resin, and a polyester resin, and particularly more preferably a polyester resin since it is easy to provide flatness by stretching or the like.

Specific examples of the polyester resin used in the flat layer b2 are the same as specific examples of the polyester resin used in the easily molded layer b1.

The polyester resin used in the flat layer b2 may be a homopolymer, a copolymer using two or more monomers, or a mixture of two or more polyester resins, but is preferably a homopolymer or a copolymer, and more preferably a homopolymer.

The homopolymer of the polyester resin is preferably polyethylene terephthalate (PET), polyethylene isophthalate (IAPET), polybutylene terephthalate (PBT), or polyethylene-<NUM>,<NUM>-naphthalate (PEN), and more preferably polyethylene terephthalate (PET) or polyethylene-<NUM>,<NUM>-naphthalate (PEN).

A thickness of the flat layer b2 is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, further more preferably <NUM> to <NUM>, still more preferably <NUM> to <NUM>, even more preferably <NUM> to <NUM>, particularly preferably <NUM> to <NUM>, and extremely preferably <NUM> <NUM>.

The thickness of the flat layer b2 can be determined from an image obtained by observing the cross section of the base material film B including the easily molded layer b1 and the flat layer b2 with a stereomicroscope and a scale.

If the thickness of the base material film B is in a range of <NUM> to <NUM>, the base material film B used in the present invention may have a layer (hereinafter, also referred to as "the other layer b3 ") other than the easily molded layer b1 and the flat layer b2, but preferably does not have the layer since it causes excess reflection to form an unnecessary interface in view of revealing image clarity.

When the base material film B used in the present invention includes the other layer b3, the other layer b3 may be a layer containing a resin other than the thermoplastic resin used in the easily molded layer b1 and the flat layer b2, and more preferably a layer containing an olefin resin or an acrylic resin.

The easily adhesive layer A of the surface coating film according to the present invention has a thickness of <NUM> to <NUM> (<NUM> to <NUM>). In the surface coating film, the easily adhesive layer A is a layer adjacent to the described easily molded layer b1.

When the thickness of the easily adhesive layer A is in the above range, the image clarity is excellent.

The thickness of the easily adhesive layer A is preferably <NUM> or more, more preferably <NUM> or more, and even more preferably <NUM> or more in view of image clarity and adhesion.

An upper limit of the thickness of the easily adhesive layer A is preferably <NUM> or less, more preferably <NUM> or less, and even more preferably <NUM> or less in view of coating thickness, spot reduction, and durability adhesion.

The thickness of the easily adhesive layer A can be calculated from an image and scale, the image obtained by: preparing a sample in which the surface coating film according to the present invention is embedded with an epoxy resin; producing an ultrathin section by using a microtome (product name: RM2255, manufactured by Leica Camera AG) after the sample is cured at normal temperature for one day; and observing a cross section of the ultrathin section with a TEM (transmission electron microscope).

The easily adhesive layer A preferably contains: a binder resin; a crosslinking agent (hereinafter, also referred to as a "specific crosslinking agent") having at least one functional group (hereinafter, also referred to as a "specific functional group") selected from the group consisting of an epoxy group, an oxazoline group, a melamine group, a silanol group, and an isocyanate group; and a cured product of the binder resin and the crosslinking agent. Here, the melamine group is not a formal chemical term, but here refers to a so-called melamine skeleton in which nitrogen atoms (which are not nitrogen atoms in a triazine ring) are to be bonded to each of three carbon atoms constituting the triazine ring represented by a <NUM>,<NUM>,<NUM>-triazine ring.

Since the easily adhesive layer A contains the binder resin, the specific crosslinking agent, and the cured product thereof, adhesion between a fiber impregnated resin to be described later and a fiber impregnated resin after integral molding is excellent.

In view of adhesion to the fiber impregnated resin, the specific functional group of the specific crosslinking agent preferably includes at least one functional group selected from the group consisting of an isocyanate group, a silanol group, a melamine group, an epoxy group, and an oxazoline group, and particularly preferably includes an epoxy group.

The number of functional groups of the specific crosslinking agent is preferably two or more in view of improving film-forming properties and the adhesion to the fiber impregnated resin when the easily adhesive layer A is coated onto the base material film B and increasing a curing rate. When the curing rate is decreased, a ratio of a tetrafunctional crosslinking agent to the specific crosslinking agent is preferably reduced.

Examples of the crosslinking agent having an isocyanate group include <NUM>,<NUM>-tolylene diisocyanate, <NUM>,<NUM>-tolylene diisocyanate, hydrogenated tolylene diisocyanate, <NUM>,<NUM>-xylylene diisocyanate, <NUM>,<NUM>-xylylene diisocyanate, hexamethylene diisocyanate, diphenylmethane-<NUM>,<NUM>-diisocyanate, isophorone diisocyanate, <NUM>,<NUM>-bis(isocyanato methyl) cyclohexane, tetramethyl xylylene diisocyanate, <NUM>,<NUM>-naphthalene diisocyanate, triphenylmethane triisocyanate, and an adduct of these polyisocyanate compounds and a polyol compound such as trimethylolpropane and a biuret or an isocyanurate of these polyisocyanate compounds.

Among these, hexamethylene diisocyanate is preferable in view of hardness of the cured product and paint dispersibility.

Examples of the crosslinking agent having a silanol group include a silane coupling agent represented by a general formula YRSiX<NUM>. Here, Y is an organic functional group such as a vinyl group, an epoxy group, an amino group, or a mercapto group; R is an alkylene group such as a methylene group, an ethylene group, or a propylene group; and X is a hydrolyzable group such as a methoxy group or an ethoxy group, or an alkyl group (at least one X in the molecule is a hydrolyzable group). The Y part is particularly preferably an epoxy group. Specific examples of a preferable silane coupling agent include γ-glycidoxy propyl trimethoxy silane, γ-glycidoxy propyl methyl dimethoxy silane, and γ-glycidoxy propyl methyl diethoxy silane. In addition, an organic metal compound containing metals such as zirconium, titanium, and aluminum is preferably classified into alkoxides, chelates, and acylates. Specific examples thereof include, but are not limited to zirconium tetraacetylacetonate, zirconium acetate, titanium acetylacetonate, triethanolamine titanate, and titanium lactate.

The compound having a melamine group preferably includes: a methylol melamine derivative obtained by condensing melamine and formaldehyde; a compound etherified by reacting a lower alcohol such as methyl alcohol, ethyl alcohol, or isopropyl alcohol with the methylol melamine derivative; and a mixture thereof. Examples of the methylol melamine derivative include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine.

Examples of the crosslinking agent containing an epoxy group include bisphenol A - epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, <NUM>,<NUM>-hexanediol diglycidyl ether, trimethylol propane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, and diglycerol polyglycidyl ether.

Among these, glycerol polyglycidyl ether or sorbitol polyglycidyl ether is preferable in view of the hardness of the cured product and the paint dispersibility.

As the crosslinking agent having an oxazoline group, a polymer having an oxazoline group is preferable. Such a polymer can be produced by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with the other monomer. Examples of the addition polymerizable oxazoline group-containing monomer include <NUM>-vinyl-<NUM>-oxazoline, <NUM>-vinyl-<NUM>-methyl-<NUM>-oxazoline, <NUM>-vinyl-<NUM>-methyl-<NUM>-oxazoline, <NUM>-isopropenyl-<NUM>-oxazoline, <NUM>-isopropenyl-<NUM>-methyl-<NUM>-oxazoline, and <NUM>-isopropenyl-<NUM>-ethyl-<NUM>-oxazoline, and one of them or a mixture of two or more thereof can be used. Among these, <NUM>-isopropenyl-<NUM>-oxazoline is easy to use industrially and suitable, and is preferably copolymerized at a proportion where a content of the oxazoline group in the polymer is <NUM> mmol/g to <NUM> mmol/g in view of adhesion. The other monomer is not limited as long as it is a monomer copolymerizable with the addition polymerizable oxazoline group-containing monomer, examples thereof include: (meth)acrylic esters such as an alkyl acrylate and an alkyl methacrylate (an alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a <NUM>-ethylhexyl group, and a cyclohexyl group); unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid, and salts thereof (such as sodium salt, potassium salt, ammonium salt, and tertiary amine salt); unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated amides such as acryl amide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N,N-dialkyl acrylamide, and N,N-dialkyl methacrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a <NUM>-ethylhexyl group, a cyclohexyl group, or the like); vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; and α,β-unsaturated aromatic monomers such as styrene and α-methyl styrene, and one or two or more monomers thereof can be used.

A publicly known binder resin per se can be used as long as it can crosslink with the specific crosslinking agent and is excellent in adhesion with the described base material film B or a fiber impregnated resin to be described later.

As the binder resin, one kind may be used alone, or two or more kinds may be used in combination.

Examples of the binder resin include a polyurethane resin, a copolymer resin of vinyl chloride/vinyl acetate, a copolymer resin of vinyl chloride/vinyl acetate/acryl, a copolymer of acrylic resin/acrylonitrile resin/acrylamide resin, chlorinated polypropylene resin, acrylic resin, polyester resin, polyamide resin, butyral resin, polystyrene resin, nitrocellulose resin, cellulose acetate resin, and silicone resin.

Since a molding temperature preferably reaches about <NUM> in the integral molding, the binder resin is preferably a resin designed to have a glass transition temperature of lower than <NUM>, and more preferably contains at least one resin selected from the group consisting of an acrylic resin and a polyester resin having a glass transition temperature of lower than <NUM>.

In the present description, the glass transition temperature of the binder resin means a value measured using differential scanning calorimetry (DSC), and can be obtained, for example, by the following measurement method.

A dispersion of the binder resin is taken out to a Petri dish and dried in an oven to produce a binder resin dry solid film. <NUM> of the obtained dry solid film is sampled. Using differential scanning calorimetry (DSC) (product name: Q100 manufactured by TA Instruments), the sample is heated to <NUM> at a temperature rise speed of <NUM>/min and is held for <NUM> minutes, and then rapidly cooled. After a sample temperature returns to room temperature, measurement is performed at the temperature rise speed of <NUM>/min again. During the measurement, an intermediate point at which shift of a baseline to an endothermic side is observed is calculated as the glass transition temperature.

The easily adhesive layer A is preferably a layer formed by coating an easily adhesive layer forming application liquid containing the binder resin and the specific crosslinking agent onto the base material film B, and more preferably a layer formed by coating (hereinafter, may be referred to as "in-line coating") the easily adhesive layer forming application liquid on the base material film B in a film production step of the base material film B. In particular, the easily adhesive layer A formed by being coated on the base material film B and stretched once or more as a laminate with the base material film B is preferable.

As a method for producing the surface coating film, the easily adhesive layer A is preferably formed by coating during any one of steps or between the steps until all stretchings to be performed on the unstretched base material film B are completed.

The specific crosslinking agent contained in the easily adhesive layer forming application liquid is preferably used in a dispersed state in a solvent or water.

When the specific crosslinking agent is dispersed in a solvent, examples of the solvent include solvents such as methyl ethyl ketone, butyl acetate, and toluene, which are generally used as the solvent.

When the easily adhesive layer A is formed by applying the easily adhesive layer forming application liquid in film production of the base material film B, since a film producing apparatus of the base material film B is an open system, the specific crosslinking agent is particularly preferably used in dispersed state in water.

The easily adhesive layer forming application liquid may contain a component publicly known as an application liquid such as a surfactant, and an additive such as a filler for slidability, an ultraviolet inhibitor, or an antioxidant may be added in a range in which the effects of the present invention can be obtained.

Examples of the filler include: inorganic fillers such as metal hydroxides, metal oxides, carbonates, sulfates, and clay minerals; and organic fillers such as particles including a crosslinking polymer and particles including a heat resistant polymer.

When the easily adhesive layer forming application liquid contains a filler, the filler is preferably an inorganic filler, and more preferably alumina, silica, or mica.

An average particle diameter of the filler is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>.

When the easily adhesive layer forming application liquid contains a filler, a content of the filler is preferably <NUM> mass% to <NUM> mass%, and more preferably <NUM> mass% to <NUM> mass% with respect to the total mass of the easily adhesive layer forming application liquid.

The easily adhesive layer forming application liquid may contain a colorant used in a decorative layer to be described later.

The colorant has the same meaning as the colorant used in the decorative layer to be described later, and preferable embodiments are also the same.

When the easily adhesive layer forming application liquid contains a colorant, a content of the colorant is preferably <NUM> mass% to <NUM> mass%, and more preferably <NUM> mass% to <NUM> mass% with respect to the total mass of the easily adhesive layer forming application liquid.

Coating of the easily adhesive layer forming application liquid is not particularly limited, and the easily adhesive layer forming application liquid can be coated using publicly known coating facilities such as a roll coater, a gravure coater, a micro gravure coater, a bar coater, a die coater, and a dip coater and publicly known coating methods. Among these, as the coating method, a roll coater is preferably used by a reverse method in order to form a desired thickness uniformly and conveniently.

Examples of a method of drying or curing the easily adhesive layer forming application liquid include a method of heat treatment at <NUM> to <NUM>. The easily adhesive layer A is preferably a layer formed by drying and curing the easily adhesive layer forming application liquid by heat treatment, and more preferably a layer formed by heat treatment at <NUM> to <NUM>.

In a case where the easily adhesive layer forming application liquid is coated by the in-line coating, when a temperature of heat treatment at the time of biaxial stretching is in the above range, curing can be performed while moderately leaving unreacted specific functional groups in the specific crosslinking agent, so that the adhesion between the fiber impregnated resin and the easily adhesive layer A can be improved in the step of integral molding, and a defective appearance during integral molding can also be controlled by reducing thermal contraction of the base material film B.

From the above viewpoints, the heat treatment temperature is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and even more preferably <NUM> to <NUM>.

Before the in-line coating, a surface treatment such as a corona treatment, a flame treatment, or a plasma treatment may be applied to the base material film B as necessary. Heat treatment time can be set as appropriate to be preferably <NUM> second to <NUM> seconds, and more preferably <NUM> second to <NUM> seconds.

Further, the heat treatment may be performed by relaxing the base material film B in a longitudinal direction and/or a width direction.

A refractive index of the easily adhesive layer A at a wavelength of <NUM> is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM> in view of image clarity.

The refractive index of the easily adhesive layer A can be obtained by measuring a refractive index of the obtained resin dry solid film at a wavelength of <NUM> after a prepared water dispersed paint is dried in an oven of <NUM> for one day to remove moisture by using a laser refractive index measurement device (product name: Metricon Model <NUM> prism coupler, manufactured by Metricon Japan).

The surface coating film may further have a layer other than the easily molded layer b <NUM>, the flat layer b2, and the easily adhesive layer A (hereinafter also referred to as a "functional layer"). When the surface coating film has a functional layer, the functional layer is preferably formed opposite to the easily adhesive layer A in the surface coating film, and more preferably formed on a surface of the flat layer b2 opposite to the easily adhesive layer A in the surface coating film.

Examples of the functional layer include a decorative layer, a clear pearl layer, and a hard coat layer.

A component constituting the decorative layer is not particularly limited, examples thereof include a binder resin, a pigment, a dye, and further as necessary, an extender pigment, a solvent, a stabilizer, a plasticizer, a catalyst, and a curing agent, and these compounds can be appropriately mixed to form the decorative layer.

The pigment is not particularly limited as a colorant, and examples thereof include: inorganic pigments such as carbon black (ink), iron black, white pigments such as titanium white (titanium dioxide) and antimony white, chrome yellow, titanium yellow, red iron oxide, cadmium red, ultramarine blue, and cobalt blue; organic pigments or dyes such as quinacridone red, isoindolinone yellow, and phthalocyanine blue; metal pigments including scaly foil pieces of brass or the like; titanium dioxide coated mica; and pearl gloss pigments including scaly foil pieces of basic lead carbonate or the like.

The binder resin used for mixing coloring materials preferably has moldability.

As an embodiment of a method for producing the base material film B and the surface coating according to the present invention, an example in which a biaxially stretched polyester film is used as the base material film B will be described below.

As described above, the base material film B is preferably biaxially stretched, namely a biaxially oriented film. By biaxially stretching the base material film B, improvement of chemical resistance or durability can be anticipated, and strength as a film can be imparted.

A base resin (polyester resin in this example) which is a main component of each layer constituting the base material film B is not particularly limited as long as the easily molded layer b <NUM> and the flat layer b2 satisfy the above formula <NUM> and formula <NUM> relating to the storage modulus, and for example, may be obtained by purchasing a commercially available resin raw material and polycondensing the resin raw material by a publicly known method.

As a means for making the easily molded layer b1 and the flat layer b2 satisfy the above formula <NUM> and formula <NUM> relating to the storage modulus, information on the storage modulus of the resin may be obtained from academic literatures or a database relating to physical properties of the resin, and configuration or components of each layer may be determined with reference to the information. Of course, the storage modulus of a film produced by obtaining each resin or the storage modulus of a laminated body thereof may be actually measured, or physical properties of the film may be simulated by a computer, and the configuration or components of each layer may be determined based on the information. The physical properties of the surface coating film obtained by performing trial manufacture based on the above information may be measured, and if there is a point not preferable, adjustment or the like of materials or conditions (changing the copolymer composition or additives of the resin and layer thickness, or the like) may be repeated several times to obtain a surface coating film in which the easily molded layer b1 and the flat layer b2 satisfy the formula <NUM> and the formula <NUM>.

A preparation step includes a step of drying a resin serving as the raw material.

The drying method is not particularly limited, but, for example, drying is preferably performed at <NUM> for about <NUM> hours in a nitrogen atmosphere, a vacuum atmosphere, or the like. A drying temperature and drying time are not particularly limited as long as a moisture content in the polyester resin is preferably <NUM> ppm or less.

When melt extrusion is performed using a vented twin screw extruder, the preparation step of drying the raw material resin may be omitted.

In the melt extrusion step, the polyester resin raw material obtained in the preparation step is put into an extruder and melt kneaded in a cylinder.

The method for producing the base material film B preferably includes a step (film production step) of removing foreign matters from the molten polyester resin through a filter, leveling an extrusion amount of the molten polyester resin using a gear pump, and ejecting the molten polyester resin through a T die into a sheet form on a cooling drum to form a film.

At this time, the molten polyester resin may be extruded in a single layer, or may be extruded in multiple layers. The melt extruded molten polyester resin is preferably cooled and solidified on a support and formed into a sheet shape.

In the film production step, the polyester resin melt extruded in the melt extrusion step can be cooled to produce a film of a polyester resin sheet (base material film B). In the film production step, by for example, a method of electrostatic application using a wire shaped electrode or a tape shaped electrode, a casting method of providing a water film between a casting drum and the extruded polymer sheet, a method of adjusting a casting drum temperature within a range from a glass transition point of polyester to the glass transition point - <NUM> to stick the extruded polymer to the casting drum, or a method that combines a plurality of these methods, the sheet shaped polymer may adhere to the casting drum and be cooled and solidified to obtain an unstretched polyester resin film (base material film).

Among these casting methods, the electrostatic application method is preferable in view of productivity and planarity of the polyester resin.

A formation step of the easily adhesive layer A is preferably performed during any one of steps or between the steps until all stretchings to be performed on the unstretched base material film B are completed.

A step of forming the easily adhesive layer A exemplifies a step of forming the easily adhesive layer A by coating (in-line coating) the described easily adhesive layer forming application liquid to the base material film B having a temperature suitable for coating at the end of or after the film production step of the base material film B.

A coating method of the easily adhesive layer forming application liquid and the heat treatment conditions or the like are described above, which may also be applied to formation of the other layer of the surface coating film.

In a stretching step, examples of a method of stretching the unstretched polyester film obtained in the melt extrusion step include a sequential biaxial stretching method in which the unstretched polyester film is stretched in the longitudinal direction and then stretched in the width direction or the unstretched polyester film is stretched in the width direction and then stretched in the longitudinal direction, or a simultaneous biaxial stretching method in which the unstretched polyester film is stretched in the longitudinal direction and the width direction almost simultaneously, which can be appropriately selected.

A stretch ratio varies depending on the type of resin, but stretch is performed in the width direction and the longitudinal direction at preferably <NUM> times to <NUM> times, more preferably <NUM> times to <NUM> times, and further more preferably <NUM> times to <NUM> times.

An area magnification is preferably <NUM> times to <NUM> times in view of film formation stability, and more preferably <NUM> times to <NUM> times when the film uses polyethylene terephthalate (PET).

A stretching speed is desirably <NUM>,<NUM>%/min to <NUM>,<NUM>%/min in an extending direction of the width direction and the longitudinal direction.

A stretching temperature may be employed preferably within the glass transition temperature or higher to the glass transition temperature + <NUM> or lower, and more preferably within the glass transition temperature + <NUM> to the glass transition temperature + <NUM>. For example, it is preferable that the stretching temperature is <NUM> to <NUM> when the polyethylene terephthalate film is stretched, particularly preferably a stretching temperature in the longitudinal direction is <NUM> to <NUM> and a stretching temperature in the width direction is <NUM> to <NUM>.

The stretching may be performed a plurality of times in each direction.

A stretching method can apply a publicly known and used method, and for example, a roll stretching method or a stretching method of guiding the film to a tenter and transporting the film while gripping both ends of the film with clips can be used.

In order to impart flatness and dimensional stability, the biaxially stretched surface coating film is more preferably subjected to a heat treatment at the stretching temperature or higher and a melting point or lower in the tenter.

In order to prevent orientation distribution in the width direction, the biaxially stretched surface coating film is preferably relaxed in the longitudinal direction instantaneously immediately before and/or immediately after entering a heat treatment zone.

After the heat treatment, the biaxially stretched surface coating film is uniformly annealed, cooled to room temperature, and then wound up.

The relaxation treatment may be performed as necessary in the longitudinal direction and/or the width direction at the time of the heat treatment to the annealing.

In the surface coating film according to the present invention obtained by the production method, elongation at <NUM> is preferably <NUM>% or more in the film production direction and the width direction. An upper limit of the elongation at <NUM> is not particularly limited, and is preferably as high as possible.

When the elongation at <NUM> of the surface coating film is <NUM>% or more in the film production direction and the width direction, the surface coating film can follow a shape of a fiber reinforced resin to be described later.

The surface coating film increases a tensile stress when expanded. Since the tensile stress of the surface coating film is resistance force against a molding force at the time of integral molding with the fiber reinforced resin, the tensile stress is preferably low. On the other hand, when the tensile stress is too low, a protrusion or the like of the base material shape is excessively stretched, which easily cause defects such as thickness unevenness.

In view of smoothness, the tensile stress at <NUM> of the surface coating film is preferably <NUM> MPa to <NUM> MPa, and more preferably <NUM> MPa to <NUM> MPa.

The tensile stress of the surface coating film preferably tends to monotonically increase with expansion. The "monotonically increase with expansion" means that, when the elongation is a horizontal axis and the stress is a vertical axis, a region of the elongation where an increase in the tensile stress is <NUM> or negative in a stage until break, that is, a region of the elongation where a gradient is zero or less in a stage until break is <NUM>% or less of the elongation at break, and further <NUM>% or less of the elongation at break.

In the surface coating film according to the present invention, as a result obtained by the above production method, an absolute value Δχ of a thermal contraction difference when thermal contraction in the film production direction at <NUM> is χMD and thermal contraction in the width direction is χTD preferably satisfies the following formula (<NUM>).

When Δχ is <NUM> or less, the thermal contraction difference of the base material film B is small, and the appearance after the integral molding can be kept good. If a lower limit of Δχ dares to be provided, Δχ is preferably <NUM> or more, more preferably <NUM> or more, still more preferably <NUM> or more, even more preferably <NUM> or more, and particularly preferably <NUM> or more in that it is easy to satisfy the lower limit even in production on an industrial scale.

The surface coating film according to the present invention preferably has a total light transmittance of <NUM>% or more with respect to visible light.

Since the total light transmittance is <NUM>% or more, when, for example, carbon fibers are contained as the fiber reinforced resin, the texture of the carbon fibers can be expressed as design. When a decorative layer or the like is provided, the design of the decorative layer can be revealed more effectively. The total light transmittance is more preferably <NUM>% or more, and still more preferably <NUM>% or more.

The surface-coated fiber-reinforced resin molded article according to the present invention (hereinafter, also referred to as a "fiber reinforced resin molded article") is a molded article in which the surface coating film and the fiber impregnated resin are integrally molded.

The fiber impregnated resin includes a fiber and a resin (hereinafter, also referred to as a "matrix resin"), in which a part or all of an interior of the fiber is impregnated with the matrix resin and the fiber and the matrix resin are integrated.

The matrix resin contained in the fiber impregnated resin may be a thermosetting resin or a thermoplastic resin, but is preferably a thermosetting resin.

When the matrix resin is a thermoplastic resin, the thermoplastic resin is not particularly limited, and examples thereof include polyolefins (such as polyethylene, polypropylene, polybutylene, and polystyrene), polyamides (such as nylon <NUM>, nylon <NUM>, nylon <NUM>, nylon <NUM>, nylon <NUM>, and semi-aromatic nylon), polyimide, polyamide-imide, polycarbonate, polyesters (such as polyethylene terephthalate, polybutylene terephthalate, and polypropylene terephthalate), polyphenylene sulfide, polysulfoxide, polytetrafluoroethylene, acrylonitrile butadiene styrene copolymer, polyacetal, polyether, polyether ether ketone, polyoxymethylene, and thermoplastic epoxy resin. The thermoplastic resin may be a derivative of the above thermoplastic resin, a copolymer of the above thermoplastic resin, or a mixture thereof.

When the matrix resin is a thermoplastic resin, a molding temperature (Ts) at the time of integrally molding the surface coating film and the fiber impregnated resin is preferably lower than a softening point (Tn) of the resin contained in the base material film B, more preferably satisfies a relationship of Tn ≤ Ts - <NUM>, and still more preferably satisfies a relationship of Tn ≤ Ts - <NUM>.

When the matrix resin is a thermosetting resin, the thermosetting resin is not particularly limited, and examples thereof include a thermosetting epoxy resin, an unsaturated polyester resin, a vinyl ester resin, a phenol resin, a melamine resin, a polyurethane resin, a silicone resin, a maleimide resin, a cyanate ester resin, and a resin obtained by pre-polymerizing the maleimide resin and the cyanate ester resin. A mixture of these resins may be used.

When the article is applied to the fiber reinforced composite material, the thermosetting resin is preferably an epoxy resin in view of excellent heat resistance, elastic modulus, and chemical resistance.

When the matrix resin is a thermosetting resin, curing time at <NUM> is preferably <NUM> minutes or less as the curing rate of the thermosetting resin. In terms of shortening the curing time and improving moldability, the thermosetting resin is preferably an epoxy resin in which the curing time at <NUM> is <NUM> minutes or less as the curing rate.

When the matrix resin is a thermosetting resin, a glass transition temperature of the thermosetting resin is preferably <NUM> or higher, more preferably <NUM> or higher, and even more preferably <NUM> or higher. When the glass transition temperature of the thermosetting resin is <NUM> or higher, even in a case where an ambient temperature is <NUM> or higher during use of a surface coated laminate, the cured product of the thermosetting resin is difficult to get in a rubber state, so that smoothness of the surface of the surface coating film is easily kept.

The glass transition temperature of the thermosetting resin can be obtained by, for example, the same method as that of the glass transition temperature of the described binder resin.

A rate of content (RC) of the matrix resin is preferably <NUM> mass% to <NUM> mass%, more preferably <NUM> mass% to <NUM> mass%, and still more preferably <NUM> mass% to <NUM> mass% based on a total mass of the fiber impregnated resin.

When the rate of content of the matrix resin is <NUM> mass% or more, a void or the like is difficult to occur in a molded article to be obtained, and mechanical properties or the like are easily imparted. When the rate of content of the resin is <NUM> mass% or less, a reinforcing effect by the fiber can be obtained, and mechanical properties or the like can be imparted.

Here, the rate of content (RC) of the matrix resin is obtained by immersing the fiber impregnated resin in sulfuric acid and eluting the matrix resin impregnated in the fiber impregnated resin. Specifically, the rate of content (RC) of the matrix resin is obtained by the following method.

First, the fiber impregnated resin is cut into <NUM> × <NUM> to produce a test piece, and a mass thereof is measured. Next, the test piece of the fiber impregnated resin is immersed in sulfuric acid and boiled as necessary. Thus, the resin impregnated in the fiber impregnated resin is decomposed and eluted in the sulfuric acid. Thereafter, the remaining fibers are filtered and washed with water, and then dried to measure a mass of the fibers. The rate of content of the matrix resin can be calculated from a mass change before and after the decomposition operation by sulfuric acid.

The fibers contained in the fiber impregnated resin are not particularly limited, and examples thereof include glass fibers, carbon fibers, aramid fibers, boron fibers, alumina fibers, basalt fibers, and silicon carbide fibers. These fibers may be used in one kind alone or in combination of two or more kinds thereof. In view of obtaining a lighter and more durable molded article, the fiber impregnated resin preferably contains carbon fibers.

The shape of the fiber contained in the fiber impregnated resin is preferably a sheet shaped fiber (fiber reinforced sheet). The fiber reinforced sheet is not particularly limited, and examples thereof include a sheet in which a plurality of fibers are aligned in one direction, a bidirectional fabric such as plain weave or twill weave, a multiaxial fabric, a nonwoven fabric, a mat, a knit, a braid, and a paper made of a reinforced fiber.

A content of the fiber contained in the fiber impregnated resin is preferably <NUM> mass% to <NUM> mass% with respect to the total mass of the fiber impregnated resin. Since the content of the fiber is <NUM> mass% or more with respect to the mass of the fiber impregnated resin, mechanical properties of the obtained surface coated laminate can be improved. When the content of the fiber is <NUM> mass% or less, it is possible to reduce a decrease in fluidity at the time of molding and to sufficiently impregnate the fiber with a resin component of the fiber impregnated resin, and as a result, the mechanical properties can be improved.

When the content of the fiber is in the above range, smoothness of the surface coating film or the surface coated laminate can be improved, and an appearance of a laminated sheet can be further improved.

When the fiber reinforced sheet is a multiaxial fabric, preferable examples of the multiaxial fabric include [+<NUM>/-<NUM>], [-<NUM>/+<NUM>], [<NUM>/<NUM>], [<NUM>/+<NUM>/-<NUM>], [<NUM>/-<NUM>/+<NUM>], and [<NUM>/+<NUM>/<NUM>/-<NUM>].

The <NUM>, ±<NUM>, and <NUM> represents a lamination angle of each layer constituting the multiaxial fabric, and indicate that a fiber axial direction of the reinforced fiber aligned in one direction is <NUM>°, ±<NUM>°, and <NUM>° respectively with respect to a length direction of the fabric. The lamination angle is not limited to these angles, and can be any angle.

A basis weight of the multiaxial fabric is preferably <NUM>/m<NUM> to <NUM>/m<NUM>, more preferably <NUM>/m<NUM> to <NUM>/m<NUM> per sheet.

When the fiber reinforced sheet is a bidirectional fabric, examples of the bidirectional fabric include publicly known fabrics such as plain weave, sateen weave, and twill weave.

A basis weight of the bidirectional fabric is preferably <NUM>/m<NUM> to <NUM>/m<NUM>, and more preferably <NUM>/m<NUM> to <NUM>/m<NUM> per sheet.

When the fiber reinforced sheet is a mat or a made paper, a number average fiber length of the fibers is preferably <NUM> to <NUM>. More preferably, the number average fiber length of the fibers is <NUM> to <NUM>.

By setting the number average fiber length of the fibers to <NUM> or more, a reinforcing effect by the fiber can be improved. On the other hand, by setting the number average fiber length of the reinforced fibers to <NUM> or less, it is possible to reduce spring back of the surface coating film and to further improve the smoothness of the surface coating film, and it is possible to reduce occurrence of cracks (fissures) or cavities inside the surface coating film.

As a method for measuring the number average fiber length of the fibers contained in the fiber impregnated resin, the number average fiber length can be confirmed by a method (burning off method) of: performing a heat treatment in a temperature range in which fibers are not oxidized and reduced to burn off the resin component (matrix resin) only of the fiber impregnated resin and separate the fiber from the resin component; then randomly selecting <NUM> fibers by observation with an optical microscope; measuring lengths of the selected fibers up to <NUM>; and calculating a number average value thereof to obtain the number average fiber length. The burning off method can also be applied to a case where there is no solvent for dissolving the matrix resin.

The surface-coated fiber-reinforced resin molded article (fiber reinforced resin molded article) can be produced by connecting the easily adhesive layer A in the surface coating film according to the present invention with the fiber impregnated resin and integrally molding the surface coating film and the fiber impregnated resin.

An embodiment of the method for producing the fiber reinforced resin molded article according to the present invention includes a step (integral molding step) of connecting the easily adhesive layer A in the surface coating film with the fiber impregnated resin and integrally molding the surface coating film and the fiber impregnated resin.

Hereinafter, preferable embodiments of each step of the method for producing the fiber reinforced resin molded article according to the present invention and the fiber reinforced resin molded article according to the present invention will be described in order.

In the method for producing the fiber reinforced resin molded article, a method for producing the described surface coating film may be further included as a step.

Each step of the method for producing the surface coating film is as described above, and the preferable embodiments of each step of the method for producing the surface coating film in the method for producing the fiber reinforced resin molded article have the same meaning as those of each step of the method for producing the surface coating film.

A step included in the method for producing a fiber reinforced resin molded article according to the present invention is a step of integrally molding the fiber impregnated resin and the surface coating film according to the present invention, preferably a step of integrally molding the fiber impregnated resin and the surface coating film by heat and pressure molding.

In the integral molding by heat and pressure molding, when a thermosetting resin such as an epoxy resin is used as the matrix resin of the fiber impregnated resin, the matrix resin can be cured at the same time as the integral molding. When the thermoplastic resin is used as the matrix resin of the fiber impregnated resin, the integral molding can be performed while softening the matrix resin, and thus production efficiency is excellent.

The heat and pressure molding method is not particularly limited, and can employ a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, or the like, but the press molding method is preferable in view of enhancing adhesion with the matrix resin at the same time as the integral molding.

A molding temperature (or curing time) in the heat and pressure molding method may be appropriately selected depending on the selected matrix resin, and for example, when the epoxy resin composition is used as the matrix resin, a temperature of generally <NUM> to <NUM> is preferable in view of fast curability though depending on the type of a curing agent contained in the composition.

A molding pressure in the press molding method varies depending on the thickness or the like of the fiber impregnated resin, but is preferably a pressure of <NUM> MPa to <NUM> MPa in general. Since heat can be sufficiently conveyed to the inside of the fiber impregnated resin and the resin contained in the fiber impregnated resin can be sufficiently cured when the pressure is <NUM> MPa to <NUM> Mpa, occurrence of warpage is reduced, and a surface appearance is also excellent.

The integral molding step is preferably a step of integrally molding the fiber impregnated resin at <NUM> for <NUM> minutes or less.

When the curing conditions are at <NUM> and for <NUM> minutes or less, time until the curing ends can be shortened, and the moldability can be further improved.

Hereinafter, the present invention will be described in more detail by Examples, but the present invention is not limited thereto. Each value in this Example was obtained by the following method.

The easily adhesive layer forming application liquid was prepared by mixing a specific crosslinking agent and a binder resin at a ratio shown in Table <NUM>. In the easily adhesive layer forming application liquid, a main binder resin dispersion paint and an additive paint such as a curing agent dispersion paint were added to ion exchange water, and stirred and dispersed to obtain a water dispersion paint. The easily adhesive layer forming application liquid was prepared so that a surfactant was further added as necessary and a total in solid contents was <NUM>%, and stirred and dispersed so that a solid content concentration of the easily adhesive layer forming application liquid was <NUM>%.

Further, the easily adhesive layer forming application liquid was supplied by a pump and passed through a filter to remove foreign matter, and then stored in an application liquid pan, which was used in production of the surface coating film.

The binder resin contained in the easily adhesive layer forming application liquid is as follows.

An acrylic resin copolymer obtained by performing an addition condensation reaction of <NUM> mol% of methyl methacrylate, <NUM> mol% of ethyl acrylate, <NUM> mol% of acrylonitrile, and <NUM> mol% of N-methylol acrylamide.

The weight average molecular weight is <NUM>,<NUM>. The weight average molecular weight was measured by the described method. The weight average molecular weight was measured in the same manner below.

An acrylic resin copolymer obtained by performing an addition condensation reaction of <NUM> mol% of methyl methacrylate, <NUM> mol% of ethyl acrylate, and <NUM> mol% of N-methylol acrylamide.

A polyester resin in which a polyester resin <NUM> and a polyester resin <NUM> composed of the following copolymerization components are blended at a mass ratio of <NUM>:<NUM>. The weight average molecular weight is <NUM>,<NUM>.

Polyester resin <NUM>: a polyester resin obtained by synthesis using <NUM> mol% of terephthalic acid as a carboxylic acid component and <NUM> mol% of ethylene glycol as a glycol component. The weight average molecular weight is <NUM>,<NUM>.

Polyester resin <NUM>: a polyester resin obtained by synthesis using <NUM> mol% of naphthalenedicarboxylic acid and <NUM> mol% of isophthalic acid as a carboxylic acid component and <NUM> mol% of ethylene glycol as a glycol component. The weight average molecular weight is <NUM>,<NUM>.

A resin composition obtained by blending the following polyester resin <NUM> and the above acrylic A at a mass ratio of <NUM>:<NUM>.

Polyester resin <NUM>: a resin obtained by synthesis using: terephthalic acid as a carboxylic acid component; and a glycol component containing ethylene glycol and diethylene glycol at a molar ratio of <NUM>: <NUM>.

The weight average molecular weight is <NUM>,<NUM>.

Terephthalic acid and ethylene glycol were polymerized to obtain a polyester P1.

Further, a carboxylic acid component of terephthalic acid and isophthalic acid (terephthalic acid : isophthalic acid = <NUM>:<NUM> [molar ratio]) and ethylene glycol were polymerized to obtain a polyester P2. A polyester Q was obtained by polymerization using terephthalic acid as a carboxylic acid component and butylene glycol as a glycol component.

Further, a treatment in which agglomerated silica particles (manufactured by Fuji Silysia Chemical Ltd. ) having an average particle diameter of <NUM> were contained in the polyester P2 on the order of ppm was performed by a publicly known method to obtain a polyester R.

The polyesters P2, Q, and R prepared above were dried at <NUM> for <NUM> hours to remove moisture, then supplied to a hopper so that polyester P2/polyester Q/polyester R = <NUM>/<NUM>/<NUM> in a weight ratio to be chip mixed, and then melt extruded into a sheet shape from an extruder set to <NUM> by using a die.

When melt extrusion was performed into a sheet shape, the polyester P1 was merged from a die by using a feed block, and a layer (the flat layer b2) containing the polyester P1 was laminated on a layer (easily molded layer b1) containing the polyesters P2, Q, and R, and the two layers were extruded so that a thickness ratio of the easily molded layer b1 to the flat layer b2 was <NUM>:<NUM>, and immediately cooled by a casting drum at <NUM> to obtain a cast film (base material film B).

In a subsequent longitudinal stretching step, the obtained cast film was stretched to <NUM> times at <NUM> to obtain a uniaxial film. The easily adhesive layer forming application liquid prepared above was applied to a surface of the layer (the easily molded layer b1) containing the polyester P2 in the uniaxial film by a roll coater so that a film thickness of the easily adhesive layer A has a thickness shown in Table <NUM>, then guided to a stenter step, and a coating film was dried to form the easily adhesive layer A.

The obtained uniaxial film was stretched so that transverse stretching was <NUM> times at <NUM>, relaxed <NUM>% in the width direction while being treated at <NUM> in a crystallization zone to reduce thermal contraction to produce the surface coating film which is a biaxially stretched film having a thickness of <NUM>, and wound into a roll shape.

Thermal contraction of the surface coating film at <NUM>, the storage moduli at each temperature of the easily molded layer b1 and the flat layer b2, the thickness of the easily adhesive layer A, and presence or absence of an epoxy group and an oxazoline group in the easily adhesive layer A are measured by a method to be described below, and the results are described in Table <NUM>.

Thermal contraction of the surface coating film in Table <NUM> at <NUM> in the film production direction (MD direction) and the width direction (TD direction) was measured by the following method.

The base material film B was cut into <NUM> × <NUM> and used as an evaluation sample. Gauge points at <NUM> intervals were noted in the film production direction (MD direction) and the width direction (TD direction) of the evaluation sample, and then a heat treatment was performed in an oven at <NUM> for <NUM> minutes. After the heat treatment, the evaluation sample was cooled to room temperature, a length between the gauge points after the heat treatment was subtracted from a length between the gauge points before the heat treatment, and the difference was divided by the dimension before the heat treatment to obtain a thermal contraction rate (%).

The thickness of the easily adhesive layer A in Table <NUM> was measured by the following method.

A small piece was sampled from the surface coating film, embedded and cured with an epoxy resin, then an ultrathin section was produced using a microtome, and a cross section thereof was observed with a transmission electron microscope (TEM). The thickness of the easily adhesive layer A was calculated from the obtained image and scale. A measurement of another layer of the surface coating film and collection of an analysis sample from another layer of the surface coating film can also be performed according to the procedure described above.

The content of the functional groups was confirmed using H-NMR on the ultrathin section obtained by the production method for measuring the thickness of the easily adhesive layer A.

The storage modulus ELb1 of the easily molded layer b1 at <NUM> and a frequency of <NUM> was measured using a dynamic viscoelasticity measurement device (product name: DMA8000, manufactured by PerkinElmer) while pulling the easily molded layer b1 in the MD direction with a tension jig.

In measurement of the storage elastic modulus ELb1, a storage modulus of the easily molded layer b1 was measured in the same manner as the measurement of the storage modulus ELb1, except that a measurement temperature was <NUM>.

In measurement of the storage modulus ELb1, a storage modulus of the flat layer b2 at <NUM> was measured in the same manner as measurement of the storage modulus EHb1, except that the flat layer b2 was used instead of the easily molded layer b1.

Five sheets of fiber impregnated resin (carbon fiber reinforced prepreg composed of epoxy resin, Tenax (registered trademark) W-<NUM>/Q-<NUM>, manufactured by Teijin Limited) were laminated to produce a laminate of the fiber impregnated resin. The surface coating film obtained above and the laminate of the fiber impregnated resin overlapped so that the easily adhesive layer A of the surface coating film and the laminate are in contact with each other, then integral molding was performed by press molding at a molding temperature of <NUM>, and an integrally molded article of the carbon fiber reinforced resin was obtained at curing time of <NUM> minutes.

The obtained integrally molded article (hereinafter, also simply referred to as "integral molded article") of the carbon fiber reinforced resin was used to perform the following evaluation. The results were shown in Table <NUM>.

The surface of the surface coating film of the integrally molded article obtained above was cut to a depth reaching the base material film B to provide a grid shaped scratch of <NUM> squares. A polyester adhesive tape (product name: No. 31B, manufactured by Nitto Denko Corporation) was attached so as to cover the whole grid shaped scratches, and the adhesive tape was peeled off. The surface of the surface coating film after peeling was observed with an optical microscope (<NUM> times), the number of peelings and coating film cracks was measured, and adhesion to the fiber reinforced resin was evaluated by the following criteria. The results were shown in Table <NUM>.

The obtained integrally molded article was visually observed under a fluorescent lamp (manufactured by Panasonic Corporation, <NUM>-wavelength neutral white, FHF24SEN <NUM> W). When reflection of the fluorescent lamp was visually confirmed, distortion of a fluorescent lamp image projected on the surface of the surface coating film of the integrally molded article was observed to perform evaluation of the image clarity based on the following evaluation criteria. The distortion of the fluorescent lamp image was observed in specular reflection, and an observation angle is an angle from a horizontal plane.

A <NUM>° gloss value (glossiness) of the surface of the surface coating film of the integrally molded article was measured using a handy gloss meter (product name: PG-IIM, manufactured by Nippon Denshoku Industries Co. The larger the measured value, the better the glossiness is.

Total light transmittance (unit: %) of the surface coating film was measured using a Haze measuring instrument (NDH-<NUM>) manufactured by Nippon Denshoku Industries, Ltd. , in accordance with total light transmittance JIS K7361 to read average light transmittance at <NUM> to <NUM>.

Surface coating films were produced in the same manner as in Example <NUM> except that composition and thickness of Example <NUM> were changed to those shown in Table <NUM> or Table <NUM>, and integrally molded articles of a carbon fiber reinforced resin were obtained by press molding. The obtained integrally molded articles were evaluated separately in the same manner as in Example <NUM>. In all Examples except for Example <NUM>, the total light transmittance of the surface coating film was <NUM>% or more.

MD in Table <NUM> and Table <NUM> means the longitudinal direction, and TD in Table <NUM> and Table <NUM> means the width direction. Abbreviations in Table <NUM> and Table <NUM> are as follows.

Compounds used in production of the surface coating films of Table <NUM> and Table <NUM> are shown below.

Silica: manufactured by Nissan Chemical Corporation, trade name: "ST-OL".

W-<NUM>/Q-<NUM>: carbon fiber reinforced prepreg including epoxy resin, product name: fabric prepreg "Tenax" (registered trademark) W-<NUM>/Q-<NUM>, manufactured by Toho Tenax Co.

Fiber basis weight: <NUM>/m<NUM>, resin content rate: <NUM> mass%, curing time at <NUM>: <NUM> minutes.

The specific crosslinking agent contained in the easily adhesive layer forming application liquid used during formation of the easily adhesive layer A is as follows.

Crosslinking agent containing epoxy group as functional group: a crosslinking agent containing a bifunctional epoxy group (trade name "DENACOL EX-<NUM> ", manufactured by Nagase ChemteX Corporation) and a crosslinking agent containing a tetrafunctional epoxy group (trade name: "TETRAD-X", manufactured by Mitsubishi Gas Chemical Company, Inc. ) were mixed at a ratio of <NUM>:<NUM> and used.

Crosslinking agent having oxazoline group as functional group: trade name "Epocros (registered trademark) WS-<NUM>", manufactured by Nippon Shokubai Co.

From the results described in Table <NUM> and Table <NUM>, the fiber reinforced resin molded article according to the present invention has excellent image clarity as compared with the fiber reinforced resin molded article of Comparative Examples. The fiber reinforced resin molded article according to the present invention has excellent adhesion.

It can be said that the surface coating film according to the present invention is an epoch making technique capable of finishing painting at the same time as integral molding with the fiber reinforced resin, and is industrially useful not only in sports equipment, automobiles, ships, and aircrafts but also in other applications.

Claim 1:
A surface coating film for integral molding with a fiber impregnated resin, the film comprising:
a base material film B; and
an easily adhesive layer A provided on the base material film B, the base material film B including
an easily molded layer b1 adjacent to the easily adhesive layer A and
a flat layer b2, wherein
the easily adhesive layer A has a thickness of <NUM> to <NUM>, wherein the thickness of the easily adhesive layer A is calculated from an image and scale, the image being obtained by preparing a sample in which the surface coating film according to the present invention is embedded with an epoxy resin; producing an ultrathin section by using a microtome after the sample is cured at normal temperature for one day; and observing a cross section of the ultrathin section with a TEM (transmission electron microscope);
the base material film B has a thickness of <NUM> to <NUM>; and
the easily molded layer b1 and the flat layer b2 satisfy each of the following formula <NUM> and formula <NUM>: <MAT> <MAT>
wherein the storage modulus ELb1 of the easily molded layer b1 was measured at <NUM> and a frequency of <NUM> using a dynamic viscoelasticity measurement device while pulling the easily molded layer b1 in the MD direction with a tension jig,
wherein the storage modulus EHb1 of the easily molded layer b1 was measured in the same manner as the measurement of the storage modulus ELb1, except that a measurement temperature was <NUM>, and
wherein the storage modulus EHb2 of the easily molded layer b1 was measured in the same manner as the measurement of the storage modulus EHb1, except that the flat layer b2 was used instead of the easily molded layer b1.