Functional film and method for producing functional film

Abstract

To provide a functional film which, when pasted on a substrate while heating the functional film under vacuum, pinholing due to solvent evaporation is hard to occur.SOLUTION: A functional film for coating a substrate satisfies the following formula (1) (where the functional film excludes one obtained by fabricating a plastic material): (W1-W2) / W1×100≤7.00 (1), wherein W1 is the mass of a functional film measuring 50 mm in length and 50 mm in width 23°C and W2 is the mass of the same film after heating at 0.2 kPa and 140°C for 2 hours.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a functional film and a method for producing the functional film, and more particularly to a functional film that has excellent appearance and does not produce popping when applied while being heated in a vacuum. [Background technology]

[0002] Currently, the most common method for protecting and decorating a substrate is to paint it with a paint, which forms a protective or decorative layer. On the other hand, a technique for attaching a film to the substrate has also been proposed as another method for protecting and decorating the substrate.

[0003] The technology of attaching a decorative molded body having a functional layer laminated on at least one side of a plastic film to a substrate is an alternative to painting, which is difficult to secure space for and requires complex process management, and can impart a design-oriented appearance to the target substrate, as well as surface texture and impact resistance (for example, JP 2015-044325 A and JP 2015-044326 A). A method of laminating a functional layer on a plastic film can be relatively easily produced by uniformly applying a coating material that will become the functional layer to the plastic film and drying it (for example, JP 2015-040318 A and JP 2019-214181 A). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-044325 A [Patent Document 2] JP 2015-044326 A [Patent Document 3] JP 2015-040318 A [Patent Document 4] JP 2019-214181 A Summary of the Invention [Problem to be solved by the invention]

[0005] In general, in the process of producing a functional film provided with a functional layer, shortening of the production time is required from the viewpoint of productivity, and after applying a coating material for forming a functional layer to a release film, it is necessary to form a functional layer under heating conditions in a short time. Therefore, there is often a trace amount of residual solvent inside the functional layer, and when the functional film is attached to a substrate by a heating and decompression process, the residual solvent evaporates, causing popping during molding, resulting in a problem of poor appearance.

[0006] Therefore, an object of the present invention is to provide a functional film that does not cause defects in appearance even when it is attached to any substrate while being heated in a vacuum. [Means for solving the problem]

[0007] As a result of intensive research into achieving the above-mentioned object, the inventors have found that by adjusting the difference between the mass of a functional film at 23°C and the mass of the functional film after heating at 0.2 kPa and 140°C for 2 hours to be small, it is possible to provide a functional film that is less likely to develop solvent-induced popping when attached to a substrate while heating under vacuum, and have thus completed the present invention.

[0008] Therefore, the functional film of the present invention is a functional film for covering a substrate, and is characterized in that it satisfies the following formula (1) (however, the functional film does not include those obtained by molding and processing a plastic material). (W1-W2) / W1×100≦7.00...Formula (1) Here, W1 is the mass of a functional film having a length of 50 mm and a width of 50 mm at 23°C, and W2 is the mass of a functional film having a length of 50 mm and a width of 50 mm after heating at 0.2 kPa and 140°C for 2 hours.

[0009] In another preferable embodiment of the functional film of the present invention, the functional film contains a pigment and a resin.

[0010] The method for producing a functional film of the present invention is a method for producing a functional film for covering a substrate, the functional film being produced by applying at least one type of coating composition containing an organic solvent to the surface of a release film, forming a functional layer, and then removing the release film, and is characterized in that the method for producing a functional film satisfies the following formula (2): (W1-W2) / W1×100≦7.00...Formula (2) Here, W1 is the mass of a functional film having a length of 50 mm and a width of 50 mm at 23°C, and W2 is the mass of a functional film having a length of 50 mm and a width of 50 mm after heating at 0.2 kPa and 140°C for 2 hours.

[0011] In another preferred embodiment of the method for producing a functional film of the present invention, the organic solvent contains 70% by mass or less of a solvent having a boiling point lower than 100° C.

[0012] In another preferable embodiment of the method for producing a functional film of the present invention, the organic solvent contains 15 mass % or less of a solvent having a boiling point higher than 150° C. Effect of the Invention

[0013] According to the present invention, it is possible to provide a functional film that is less likely to develop popping due to solvent loss when the functional film is attached to a substrate while the substrate is heated under vacuum. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a schematic diagram showing an embodiment in which an adhesive layer is provided on the functional film of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing an embodiment in which an adhesive layer is provided on a substrate and then a functional film is attached to the adhesive surface. [Diagram 3] FIG. 2 is a schematic diagram showing an embodiment in which an adhesive layer is provided on one side of the functional film of the present invention, and then the adhesive surface is attached to a substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention relates to a functional film and a method for producing the functional film.

[0016] The functional film of the present invention is a film for imparting functionality to a substrate. The functionality means, for example, decoration, water repellency, hydrophilicity, weather resistance, etc. Here, decoration means providing a design to the substrate or imparting a texture different from that of the substrate. The design means a shape, pattern, color, or a combination of these. By imparting water repellency and hydrophilicity to the substrate, it is also possible to impart a stain prevention function.

[0017] In the present invention, the functional film satisfies the requirement of the following formula (1). (W1-W2) / W1×100≦7.00...Formula (1) Here, W1 is the mass of a functional film having a length of 50 mm and a width of 50 mm at 23°C, and W2 is the mass of a functional film having a length of 50 mm and a width of 50 mm after heating at 0.2 kPa and 140°C for 2 hours.

[0018] If the functional film is within the range of the above formula (1), when the functional film is heated under vacuum, the volatile components contained in the functional film are small, so that when the functional film is attached to a substrate, popping does not occur and the appearance is not impaired. On the other hand, if the value of formula (1) exceeds 7.00, when the functional film is heated under vacuum, the volatile components contained in the functional film tend to be generated in large amounts, so that when the functional film is attached to a substrate, popping occurs and the appearance is deteriorated.

[0019] In the present invention, the substrate means an object to which the functional film is applied. Suitable substrates to which the functional film of the present invention is applied include automobiles and automobile parts, electrical appliances, small items, interior goods, and the like.

[0020] Examples of the substrate include metal substrates such as iron, stainless steel, aluminum, copper, titanium, and alloys thereof; inorganic substrates other than metals such as cement, concrete, gypsum, calcium silicate, calcium carbonate, marble, artificial marble, glass, and ceramics; wood substrates; and plastic substrates such as epoxy resin, ABS resin, polycarbonate, polyvinyl chloride, polystyrene, acrylic resin, and in particular polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polypropylene (PP); and composite substrates that combine two or more of these substrates.

[0021] In the present invention, the substrate may have various shapes, for example, a two-dimensional substrate such as a film, sheet, or plate, or a three-dimensional substrate that is a complex three-dimensional object, etc. The surface of the substrate may be smooth or may have irregularities.

[0022] In the present invention, the functional film is composed of at least one functional layer, and does not include a film obtained by molding a plastic material. Here, a film obtained by molding a plastic material includes a film (molded film) obtained by molding a resin, such as a commercially available PET film, PC (polycarbonate) sheet, ABS sheet, etc.

[0023] The functional layer can be formed by a composition for forming a coating film. Examples of the composition for forming a coating film include paints and inks containing organic solvents. The functional layer may be a coating layer formed by painting a coating film or a printed layer formed by printing an ink, and this functional layer can be used as a functional film. Furthermore, a functional film may be formed by laminating a plurality of coating layers or a plurality of printed layers. A functional film may also be formed by laminating a coating layer and a printed layer, or a functional film may be formed by laminating a coating layer, a printed layer, and a coating layer in this order.

[0024] The functional layer preferably has a thickness of 10 to 250 μm or less. If the thickness is 250 μm or less, the amount of volatile components contained in the functional layer can be adjusted to be small, and if the thickness is 10 μm or more, the physical properties of the functional layer can be maintained. When the functional layer is composed of multiple layers, the numerical range of thickness described here refers to the total thickness of the functional layer.

[0025] The functional layer may be colored or transparent.

[0026] The functional layer usually contains a resin. The amount of the resin in the functional layer is preferably 10 to 100% by mass, and more preferably 20 to 95% by mass. When the functional layer is composed of multiple layers, the numerical range described here refers to the amount of the resin in each functional layer.

[0027] Examples of resins that can be used in the functional layer include acrylic resins, silicone resins, acrylic silicone resins, styrene-acrylic copolymer resins, polyester resins, fluororesins, rosin resins, petroleum resins, coumarone resins, phenolic resins, urethane resins, melamine resins, urea resins, epoxy resins, cellulose resins, xylene resins, alkyd resins, aliphatic hydrocarbon resins, butyral resins, maleic acid resins, fumaric acid resins, vinyl resins, amine resins, and ketimine resins, among which acrylic resins and cellulose resins are more preferred. The resins may be used alone or in combination of two or more.

[0028] The weight average molecular weight (Mw) of the resin usable in the functional layer is preferably 10,000 to 200,000, and more preferably 30,000 to 80,000. This makes it possible to provide a functional layer of a functional film that is less likely to develop popping due to solvent loss even when attached to a substrate while being heated.

[0029] In this specification, the weight average molecular weight of the resin is measured by gel permeation chromatography. value, and polystyrene is used as the standard material.

[0030] The functional layer may contain, as other components, appropriately as necessary, a pigment, a dispersant, an antioxidant, an anti-settling agent, an antifoaming agent, a silane coupling agent, an adhesion imparting agent, an anti-algae agent, an anti-fungal agent, a preservative, an insecticide, an antibacterial agent, an antiviral agent, an ultraviolet absorber, a radical scavenger, an antistatic agent, an electrical conductivity imparting agent, a surface conditioner, and the like.

[0031] Next, a method for producing the functional film for covering the substrate of the present invention will be described.

[0032] The method for producing a functional film of the present invention is characterized in that it satisfies the following formula (2): (W1-W2) / W1×100≦7.00...Formula (2) Here, W1 is the mass of a functional film having a length of 50 mm and a width of 50 mm at 23°C, and W2 is the mass of a functional film having a length of 50 mm and a width of 50 mm after heating at 0.2 kPa and 140°C for 2 hours.

[0033] If the functional film is within the range of formula (2) above, when the functional film is heated under vacuum, the volatile components contained in the functional film are small, so that when the functional film is attached to a substrate, popping does not occur and the appearance is not impaired. On the other hand, if the value of formula (1) exceeds 7.00, when the functional film is heated under vacuum, the volatile components contained in the functional film tend to be generated in large amounts, so that when the functional film is attached to a substrate, popping occurs and the appearance is deteriorated.

[0034] The value of the above formula (2) can be adjusted by appropriately adjusting the boiling point, content, etc. of the organic solvent blended in the coating-forming composition used to produce the functional film.

[0035] The release film used in the method for producing a functional film of the present invention may be, for example, a film made of polypropylene or the like.

[0036] The coating composition used in the method for producing a functional film of the present invention forms a functional layer, and for example, a paint or ink containing an organic solvent can be used. When it is desired to provide a plurality of functional layers, the functional layers may be laminated using a plurality of coating-forming compositions.

[0037] The composition for forming a coating film used in the method for producing a functional film of the present invention may be, for example, a paint or ink containing an organic solvent. The composition for forming a coating film usually contains a resin in addition to the organic solvent, and may also contain other components such as a pigment, a dispersant, an antioxidant, an antisettling agent, an antifoaming agent, a silane coupling agent, an adhesion imparting agent, an anti-algae agent, an anti-fungal agent, a preservative, an insecticide, an antibacterial agent, an antiviral agent, an ultraviolet absorbing agent, a radical scavenger, an antistatic agent, an electrical conductivity imparting agent, a surface conditioner, etc., as necessary.

[0038] The organic solvent used in the coating composition preferably contains 70% by mass or less, and more preferably 50% by mass or less, of the total solvent, that is, a solvent having a boiling point lower than 100° C. This improves the appearance before molding, such as unevenness, and as a result, leads to improved design and functionality of the functional film.

[0039] Examples of solvents with a boiling point of less than 100°C include ethyl acetate, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, 2-butanol, 2-methyl-2-propanol, diethyl ether, methyl propyl ether, dipropyl ether, diisopropyl ether, methyl-t-butyl ether, t-amyl methyl ether, divinyl ether, ethyl vinyl ether, allyl ether, n-heptane, n-hexane, cyclohexane, acetone, methyl ethyl ketone, triethylamine, diethylamine, and tetrahydrofuran. Among these, from the viewpoint of handling, ethyl acetate, methyl ethyl ketone, isopropyl alcohol, and 2-butanol are more preferable. Note that, the solvents with a boiling point of less than 100°C may be used alone or in combination of two or more.

[0040] Of the organic solvents used in the coating composition, those with a boiling point higher than 150° C. preferably account for 15% by mass or less, and more preferably 10% by mass or less, of the total solvent. This not only prevents popping during molding, but also improves drying properties, resulting in improved design and functionality of the functional film.

[0041] Solvents with a boiling point of more than 150°C include 3-methoxy-1-butyl acetate, octanol, benzyl alcohol, diacetone, 3-methyl-3-methoxybutanol, γ-butyrolactone, cyclohexanone, 2-heptanone, 2,6-dimethyl-4-heptanone, dimethyl sulfoxide, N-methyl-2-pyrrolidone, ethyl ethoxypropionate, anisole, ethyl benzyl ether, cresyl methyl ether, diphenyl ether, dibenzyl ether, phenetole, butylphenyl ether, diethylbenzene, pentylbenzene, isopropylbenzene, cymene, mesitylene, ethylene glycol monobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monobutyl ether-4-( dimethylamino)benzoate, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol dibutyl ether, dipropylene glycol-n-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol methyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol butyl ether, tripropylene glycol-n-butyl ether, tripropylene glycol monomethyl ether, etc. may be mentioned. Commercially available organic solvents, for example, "IPZOL" and "IP Solvent" manufactured by Idemitsu Kosan Co., Ltd., "New Solvent", "New Sol DX", and "Cactus Solvent" manufactured by ENEOS Corporation, etc. may be used. Among them, from the viewpoint of handling, ethylene glycol monobutyl ether, 3-methoxy-1-butyl acetate, diethylene glycol dimethyl ether, and Ipzol 150 are more preferable. The solvent having a boiling point of more than 150° C. may be used alone or in combination of two or more.

[0042] As a method for coating or printing the coating composition for forming the functional layer, a conventionally known coating or printing method can be used.

[0043] Examples of methods for applying the coating composition include dipping and application methods using a coater such as a bar coater, die coater, roll coater, comma coater, knife coater, or gravure coater.

[0044] Examples of the printing method for the coating composition include inkjet (IJ) printing, gravure printing, flexographic printing, and design spray.

[0045] An adhesive layer can be provided on the surface of the functional film in order to attach the substrate to the functional film. In this case, the functional film can be attached to the substrate via the adhesive layer.

[0046] The adhesive layer is a layer composed of an adhesive. The adhesive layer and the adhesive may be called a pressure-sensitive adhesive layer and a pressure-sensitive adhesive, respectively. Examples of the adhesive include a urethane adhesive, an acrylic adhesive, an epoxy adhesive, and a rubber adhesive, and among these, an acrylic adhesive is preferred.

[0047] The functional film of the present invention has a functional layer 1 .

[0048] Also, an adhesive layer 2 may be provided on the functional layer 1. In that case, the structure will be as shown in FIG.

[0049] Next, a method for applying the functional film of the present invention to a substrate will be described.

[0050] Methods for applying the functional film of the present invention to a substrate (more specifically, methods for attaching the functional film of the present invention to a substrate) include a method of providing an adhesive layer 2 on a substrate and then attaching a functional film to the adhesive surface, and a method of providing an adhesive layer 2 on one side of a functional film and then attaching the adhesive surface to a substrate. In these cases, the structures are as shown in Figs. 2 and 3, respectively.

[0051] The adhesive used to provide an adhesive layer on the functional film or substrate can be any of the adhesives described above.

[0052] The temperature when the functional film of the present invention is applied to a substrate (more specifically, when the functional film of the present invention is attached to a substrate) is, for example, 80°C to 140°C.

[0053] The means for applying the functional film of the present invention to a substrate (more specifically, the means for attaching the functional film of the present invention to a substrate) is not particularly limited, and examples thereof include vacuum forming, overlay vacuum forming, hand attachment, blow molding, insert molding, and in-mold molding. When performing the vacuum molding method or the overlay vacuum molding method, the degree of vacuum is preferably set to 0.1 kPa to 50 kPa. EXAMPLES

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0055] (Paint preparation) The paints No. 1 to 20 used in Examples 1 to 16 and Comparative Examples 1 to 4 were mixed in the mixing ratios shown in Tables 1 to 3 and dispersed by a known method to prepare the paints. The materials used are as follows. <Resin (shown as solid content in the table)> Acrylic resin A: solid content 50% by mass, acid value 2.0 mgKOH / g, hydroxyl value 0 mgKOH / g, manufactured by DIC, Acrydic A-141 Acrylic resin B: solid content 45% by mass, acid value 8.0 mgKOH / g, hydroxyl value 0 mgKOH / g, manufactured by DIC, Acrydic LA-9005 Acrylic resin C: solid content 40% by mass, acid value 1.0 mgKOH / g, hydroxyl value 0 mgKOH / g, manufactured by DIC, Acrydic WDL-787 Cellulose resin A: solid content 70% by mass, nitrogen content 12%, number average molecular weight 76,000, manufactured by Nobel NC Co., Ltd., nitrocellulose DHX30-50 Cellulose resin B: Solid content 70% by mass, nitrogen content 12%, TNC, TR1 / 16 Cellulose resin C: solid content 100% by mass, number average molecular weight 30,000, manufactured by Eastman Chemical Japan, CAB-551-0.2 <Additives (shown as solid content in the table)> Polyethylene wax dispersion: solid content 16% by mass, manufactured by Gifu Shellac Co., Ltd., HIGH FLAT T-16P-2H <Pigments (shown as solid content in the table)> Aluminum dispersion: Solid content 55% by mass, average particle size 18 μm, aspect ratio 90, resin-coated aluminum dispersed in mixed solvent X described below, manufactured by Toyo Aluminum Co., Ltd., aluminum paste FZC5620 Pearl pigment: 100% solids, average particle size 5-30μm, Merck, Xirallic T60-10 WNT Crystal Silver <Solvent> EA: Ethyl acetate, molecular weight 88.11, boiling point 77℃ MEK: Methyl ethyl ketone, molecular weight 72.11, boiling point 80℃ IPOH: Isopropyl alcohol, molecular weight 60.10, boiling point 82℃ IBOH: Isobutyl alcohol, molecular weight 74.12, boiling point 107℃ ·TL: Toluene, molecular weight 92, boiling point 111℃ ·MIBK: Methyl isobutyl ketone, molecular weight 100.16, boiling point 116℃ IBA: Isobutyl acetate, molecular weight 116.16, boiling point 117℃ ·BOH: n-butanol, molecular weight 74.12, boiling point 117℃ PM: Propylene glycol monomethyl ether, molecular weight 90.13, boiling point 121°C ·BA: Butyl acetate, molecular weight 116.16, boiling point 126℃ XL: Xylene, molecular weight 106.17, boiling point 138℃ ·CCB: Ethylene glycol monobutyl ether, molecular weight 118.18, boiling point 171℃ MCA: 3-methoxy-1-butyl acetate, molecular weight 146.19, boiling point 171°C SL150: Ipzol 150, boiling point 180℃, manufactured by Idemitsu Kosan Co., Ltd. · Mixed solvent X: Mixed solution of mineral spirits, nonane, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, and cumene. Boiling point 150°C or higher (all components)

[0056] (Example 1: Preparation of Functional Films A and B) A polypropylene plate of 297 mm × 210 mm × 2 mm was coated with the paint No. 1 by air spray so that the film thickness when dried (hereinafter, referred to as the dry film thickness) was 15 μm, and then dried at 80° C. for 20 minutes and peeled off to produce functional film A. A PP plate of 50 mm × 50 mm × 2 mm was coated with the paint No. 1 by air spray so that the film thickness when dried was 15 μm, and then dried at 80° C. for 20 minutes and peeled off to produce functional film B. Here, functional film A was used to attach to an article as described later, and functional film B was used to evaluate the weight change rate as described later.

[0057] (Example of manufacturing an article by molding functional film A) After bonding Nitto Denko's "No. 5015" as an adhesive layer to one surface of functional film A, the pressure was reduced to 0.2 kPa using a vacuum molding device (product name NGF-0709-S, manufactured by Fuse Vacuum Co., Ltd.), and the functional film A with the adhesive layer was heated to 140°C using a near-infrared lamp, and molded and pressed onto a PP molded substrate of 200 mm x 100 mm x 40 mm to obtain an article.

[0058] (Examples 2 to 16, Comparative Examples 1 to 4) In Examples 2 to 16 and Comparative Examples 1 to 4, functional films A and B were prepared in the same manner as in Example 1.

[0059] The obtained functional films A and functional films B of Examples 1 to 16 and Comparative Examples 1 to 4 were evaluated according to the following test methods.

[0060] (Evaluation method) <Appearance evaluation of functional film A before molding> The surface irregularities of the functional film A prepared as described above were visually evaluated. (Judgment criteria) 1: No surface irregularities whatsoever. 2: There is slight unevenness on the surface. 3: There is slight unevenness on the surface. 4: Surface irregularities are clearly visible. 5: Severe surface irregularities. In this evaluation, items rated as "1" or "2" are deemed to have favorable pre-molding appearance.

[0061] <Evaluation of drying property of functional film A> The functional film A prepared as described above was evaluated for dryness to touch based on "JIS K 5600-1-1:1999" general test method for paints. (Evaluation Criteria) ○: When you lightly touch the center of the coating surface with your fingertip, your fingertip does not get dirty. ×: When the center of the coating surface is lightly touched with a fingertip, the fingertip becomes dirty.

[0062] <Post-molding appearance evaluation 1 of functional film A (evaluate the presence or absence of cracks in the functional film layer)> The surface of the article obtained by attaching the functional film A was visually evaluated for the presence or absence of cracks. The evaluation criteria are as follows. (Evaluation Criteria) ◯: No cracks were observed in the functional film layer for substrates with unevenness or curved surfaces. ×: Cracks were observed in the functional film layer. -: Poor drying to the touch, making it impossible to perform moldability tests

[0063] <Post-molding appearance evaluation 2 of functional film A (evaluate the presence or absence of coating defects (pockmarks) in the functional film layer)> The surface of the article obtained by attaching the functional film A was visually evaluated for the presence or absence of coating defects (poppings). The evaluation criteria are as follows: (Evaluation Criteria) ○: No armpits are visible at all. ×: Armpits are found in more than 10% of the total area. -: Poor drying to the touch, making it impossible to perform moldability tests

[0064] <Weight change rate measurement of functional film B> Functional film B was heated at 0.2 kPa and 140° C. for 2 hours. The mass at 23° C. before heating was W1, and the mass after heating was W2, and the weight change rate was measured according to the following formula (1) (however, the functional film does not include those obtained by molding a plastic material). Weight change rate (%) = (W1 - W2) / W1 × 100 Equation (1)

[0065] When the weight change rate at 0.2 kPa was small, a good appearance could be obtained when the functional film was attached to the substrate while heating under vacuum. On the other hand, when the weight change rate (%) of the above formula (1) exceeded 7.00%, popping due to the solvent occurred, and an excellent appearance could not be obtained.

[0066] [Table 1]

[0067]

Table 2

[0068]

Table 3

Claims

1. A functional film for covering a substrate, characterized in that the functional film satisfies the following formula (1) (however, the functional film does not include films obtained by molding a plastic material): (W1-W2) / W1×100≦7.00...Formula (1) Here, W1 is the mass of a functional film having a length of 50 mm and a width of 50 mm at 23° C., and W2 is the mass of a functional film having a length of 50 mm and a width of 50 mm after heating at 0.2 kPa and 140° C. for 2 hours.

2. The functional film according to claim 1 , comprising a pigment and a resin.

3. A method for producing a functional film for covering a substrate, the method being characterized in that the functional film is produced by applying or printing at least one type of coating composition containing an organic solvent onto the surface of a release film, forming a functional layer, and then removing the release film, and the method satisfies the following formula (2): (W1-W2) / W1×100≦7.00...Formula (2) Here, W1 is the mass of a functional film having a length of 50 mm and a width of 50 mm at 23° C., and W2 is the mass of a functional film having a length of 50 mm and a width of 50 mm after heating at 0.2 kPa and 140° C. for 2 hours.

4. The method for producing a functional film according to claim 3 , wherein the organic solvent contains 70% by mass or less of a solvent having a boiling point lower than 100° C.

5. The method for producing a functional film according to claim 3 or 4, wherein the organic solvent contains 15 mass % or less of a solvent having a boiling point higher than 150° C.

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