JPH08197688A - Laminated film - Google Patents

Abstract

PURPOSE: To provide a laminated film useful for a release film excellent in the close adhesiveness of a coating film and a base film and the surface releasability of the coating film and reduced in the rear transfer of a coating film component. CONSTITUTION: A laminated film provided with a coating film is obtained by coating at least the single surface of a polyester film with an aq. coating soln. containing an emulsion or dispersion of a single fine particle consisting of 25-75wt.% of an acrylic resin and 75-25wt. of a silicone resin in the constitution within one particle and drying and stretching the coated film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film, and more particularly to a release film which has excellent adhesion between a coating film and a base film and releasability of the coating film surface and little back transfer of coating film components. It relates to a useful laminated film.

[0002]

Films made of polyester such as polyethylene terephthalate and polyethylene naphthalate are used for magnetic recording materials such as magnetic cards and magnetic tapes, and for general industry such as packaging materials, process materials, adhesive materials, photographic materials and graphic materials. Widely used for materials. However, when such a polyester film is used as, for example, a release film, it is difficult to put it into practical use if it is untreated, since the releasability for various resins and adhesives is insufficient. That is, it is difficult to use the polyester film as it is in an untreated state for a protective film of an adhesive tape, vinyl chloride, a process release film for polyurethane sol, and the like.

In order to solve such a problem, a method of laminating a releasable coating film on the surface of a polyester film is adopted, and many coating agents for applying the coating film have been developed. When the coating film is applied during the film forming process, an aqueous coating agent is usually used for environmental protection or disaster prevention. However, it is difficult to satisfy both the adhesiveness between the coating film and the base film and the releasability of the coating film with a release coating film using a conventional water-based coating agent. There is a problem that a part moves to the opposite surface of the film (hereinafter sometimes referred to as "back surface transferability"). For example, in the method using a laminated film coated with a silicone resin layer such as polydimethylsiloxane, the base film and the silicone resin layer are easily peeled off, and there is a practical defect. Further, in the method of using a coating film applied by using an aqueous coating liquid containing a composition in which a silicone resin and another binder resin are simply blended, the compatibility between the silicone resin and the binder resin is poor, so that the adhesiveness It is difficult to achieve both releasability,
The back surface transferability is also inferior. In addition, a method using an aqueous coating liquid containing a graft polymer whose main chain is composed of an acrylate compound and whose side chain is a silicone component (JP-A-3-99827).
No. 3) has a problem that a part of the silicone polymer as a side chain component is likely to remain as an unreacted component when the graft polymer is produced, and thus the unreacted silicone polymer in the coating film is easily transferred to the back surface.

[0004]

The object of the present invention is to solve the problems of the prior art and improve the releasability of the coating film surface and the back surface transferability while maintaining the adhesion to the base film. Another object of the present invention is to provide a laminated film having excellent adhesion to a silicone resin layer when laminating a silicone resin layer.

[0005]

In order to achieve such an object, the present invention has the following constitution. On at least one side of the polyester film, the composition of one particle is acrylic resin (A) 25 to 75% by weight, silicone resin (S) 75 to
A laminated film provided with a coating film prepared by applying an aqueous coating solution containing 25% by weight of a single fine particle emulsion or dispersion, drying and stretching.

The present invention will be described in detail below.

[Base Film] In the present invention, the base film is a polyester film, and the polyester constituting the film is a linear polyester composed of a dicarboxylic acid component and a glycol component.

Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, hexahydroterephthalic acid, 4,4'-diphenyldicarboxylic acid, adipic acid, sebacic acid and dodecanedicarboxylic acid. Among them, terephthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferable because they have excellent mechanical properties and thermal properties of the polyester film.

The glycol component is, for example, ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol. , 1,4-cyclohexanedimethanol, polyethylene glycol, polytetramethylene glycol, dipropylene glycol, triethylene glycol, bisphenol, and the like. In particular, ethylene glycol is used for the mechanical properties and thermal properties of the polyester film. It is preferable because it is excellent.

Preferred examples of the polyester include polyethylene terephthalate and polyethylene-2,6-naphthalate. The polyethylene terephthalate or polyethylene-2,6-naphthalate may be a polyester obtained by copolymerizing the above-mentioned dicarboxylic acid component or glycol component, and the polyester may be a polyfunctional carboxylic acid component having a functionality of 3 or more or a polyol component. It may be a polyester copolymerized in a small amount in a linear range (for example, 5 mol% or less). Such a polyester can be produced by a conventional method, and it is preferable that the average molecular weight is 10,000 or more because the mechanical properties of the film will be good.

The above polyester may contain organic or inorganic fine particles as a lubricant, for example, in an amount of 0.001 to 5% by weight in order to improve the slipperiness of the film. Specific examples of such fine particles include calcium carbonate, calcium oxide, titanium oxide, graphite, kaolin, silica, alumina, silicon oxide, zinc oxide, carbon black, silicon carbide, tin oxide, acrylic resin particles, crosslinked polystyrene resin particles, melamine resin. Particles and crosslinked silicone resin particles can be preferably mentioned.

In addition to the above-mentioned fine particles, antistatic agents, antioxidants, organic lubricants, catalysts, colorants, pigments, optical brighteners, plasticizers, crosslinking agents, lubricants, ultraviolet absorbers, other resins, etc. are required. Can be added according to

The polyester film of the present invention is
It can be manufactured by a conventionally known method. For example, the polyester is melted and cast on a cooling drum to obtain an unstretched film, and then the unstretched film is stretched 2 to 7 times in the machine direction to form a uniaxially stretched film, and the uniaxially stretched film is coated with an aqueous coating solution. After that, a biaxially stretched laminated film can be obtained in which the film is applied while being dried and stretched 2 to 7 times in the transverse direction. The stretching temperature of the film may be a temperature of the second-order transition temperature (Tg) of the polyester of not less than -10 ° C, and the biaxially stretched laminated film may be further stretched in the machine direction and / or the transverse direction, if necessary. it can. The area stretching ratio of the biaxially stretched film is 8 times or more,
Further, it is desirable to set it to 9 times or more, and the upper limit of the area stretching ratio depends on the use of the film, but it is up to 35 times, especially 3 times.
It is preferably up to 0 times. The oriented crystallization can be completed by heat treatment after stretching. The thickness of the biaxially stretched film is preferably 1 to 300 μm.

[Single Fine Particles] In the present invention, the composition of one particle on at least one surface of the polyester film is 25 to 75% by weight of acrylic resin (A) and 75 to 25% by weight of silicone resin (S). An aqueous coating solution containing one fine particle emulsion or dispersion is applied, dried and stretched to form a coating film.

The single fine particles of the present invention are those in which the acrylic resin (A) and the silicone resin (S) are simultaneously present in one particle of fine particles present in the aqueous coating liquid, and are formed by simple blending. When one particle of fine particles present in the aqueous coating liquid is present, only fine particles of acrylic resin,
This is different from the presence of fine particles in which only the silicone resin is present. In a coating film made from fine particles simply by blending, the acrylic resin particles and silicone resin particles are separated during the coating film formation, so both components tend to have a non-uniform surface structure after the coating film formation, resulting in adhesion. And the releasability are partially non-uniform, and the components are easily transferred to the back surface. On the other hand, in the coating film according to the present invention, since the acrylic resin (A) and the silicone resin particles (B) are present in close proximity to each other during the coating film formation, both components have a uniform surface structure after the coating film formation. In addition, the adhesiveness and the releasability are uniform, and the components are difficult to be transferred on the back surface.

Such a single fine particle can be produced, for example, by the following method. For example, acrylic resin (A) and silicone resin (C) are combined with methyl ethyl ketone, ethanol, ethyl acetate, tetrahydrofuran, dioxane,
Acrylic resin (A) and silicone resin (S) are obtained by adding a solvent (water-containing non-solvent) which is dissolved in a solvent such as acetonitrile and which contains water or water and has low solubility of acrylic resin (A) and silicone resin (S). Can be prepared by depositing fine particles containing in a single particle and distilling off solvents other than water. Alternatively, it can be brought about by a method of adding an acrylic monomer to the emulsion of the silicone resin (S) and performing seed polymerization. It is also possible to add a silane coupling agent to the emulsion of acrylic resin (A) and coat the acrylic resin (A) particles with the silicone resin (S).

The structure of a single fine particle may be a uniform mixture of two kinds of resins, or may be a two-layer structure of a core layer and an outer shell layer. The two kinds of resins may have a crosslinked structure, and some of them may react with each other to be bonded.

The weight ratio of the acrylic resin (A) and the silicone resin (S) in the single fine particles is a value obtained by averaging the whole single fine particles constituting the coating film, and the acrylic resin (A) is 25 to 25%.
It is preferably 75% by weight, especially 30 to 70% by weight. When the weight ratio of the acrylic resin (A) is less than 25% by weight, the adhesion between the coating film and the base film is insufficient, and the releasability of the coating film exceeding 75% by weight is insufficient.

The size of a single fine particle is arbitrary, but 2n
It is preferably m to 5 μm, particularly 10 nm to 1 μm. If the particle size is less than 2 nm, the stability of the particle in the aqueous coating solution may be poor, and if it exceeds 5 μm, the surface of the coating film may be rough.

[Acrylic resin (A)] As the acrylic resin (A) constituting the single particle, methacrylic acid ester, acrylic acid ester, methacrylic acid, acrylic acid,
Acrylamide, methacrylamide, methylol acrylamide, methoxymethyl acrylamide, methacrylate, acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, vinyl acetate, vinyl ether
Use copolymers of tellurium, vinyl chloride, vinylidene chloride, maleic acid, maleic anhydride, maleimide, vinyl cinnamate, vinyl sulfonate, styrene, styrene sulfonate, unsaturated silane coupling agents, vinyl silane, etc. be able to. Further, the acrylic resin (A) preferably contains a hydrophilic group in the molecule in order to improve the dispersibility of single particles in the aqueous coating liquid. Examples of this hydrophilic group include a hydroxyl group, a sulfonate group, a carboxylic acid group, a carboxylate group, a methylol group, a methoxymethyl group, and an amide group.

The average molecular weight of this acrylic resin (A) is 2,000 to 1,000,000, and particularly 4,000 to 5
It is preferably 0,000. Average molecular weight is 2,
If it is less than 000, the adhesiveness between the coating film and the base film is insufficient, and if it exceeds 1,000,000, the adhesiveness between the coating film and the base film is also insufficient, and the releasability of the coating film is further insufficient. Become.

[Silicone resin (S)] Polydimethylsiloxane is mainly used as the silicone resin (S) which constitutes a single particle, and an alkoxy group, an oxirane group, a polyoxyalkylene group and a vinyl group are contained in the polymer structure. , Hydroxyl group, carboxyl group, carboxylate group, SiH
Modified polydimethylsiloxanes having groups, amino groups, isocyanate groups, etc. can be used. Particularly, a polymer having a functional group such as a hydroxyl group, a carboxyl group, an amino group, a SiH group or an isocyanate group at one end or both ends is preferable. Further, the silicone resin (S) preferably contains a hydrophilic group in the molecule in order to improve the dispersibility of the single particles in the aqueous coating liquid. Examples of this hydrophilic group include an alkoxy group, a hydroxyl group, an amino group, a carboxylate group, a polyoxyalkylene group, and a sulfonate group.
It is also possible to use a silicone-based macromer, which is a medium molecular weight polydimethylsiloxane having a reactive group at the molecular end. The average molecular weight of the silicone resin (S) is preferably 500 to 50,000, and particularly preferably 800 to 20,000. When the average molecular weight is less than 500, the releasability of the coating film is insufficient, and when it exceeds 50,000, the adhesion between the coating film and the base film is insufficient.

[Aqueous Coating Solution] In the present invention, the aqueous coating solution containing the above-mentioned single fine particles is used for coating a coating film on the base film. This aqueous coating solution is preferably used as an aqueous solution such as a single fine particle emulsion or dispersion. Here, an emulsion means a state in which an emulsifier molecule exists around a particle in a water solvent by forming a micelle by coordinating a hydrophobic group on the particle side and a hydrophilic group on the water solvent side. The term "john" refers to a state in which one particle in a water solvent is stably dispersed in the water solvent by the action of a hydrophilic group existing on the surface thereof.

Other binder resins may be added to the aqueous coating liquid for the purpose of adjusting the adhesion between the coating film and the base film. Examples of other binder resins include polyester resins, polyurethane resins, water-soluble acrylic resins, epoxy resins, vinyl resins, acrylic modified polyester resins, polyether resins, cellulosic resins, and water-soluble silicone resins. Further, in addition to the above components, a filler, a surfactant, an antioxidant, an antistatic agent, a colorant, a pigment, a fluorescent whitening agent, a plasticizer, a crosslinking agent, a lubricant, an ultraviolet absorber, etc. are added to the aqueous coating liquid. can do.

The ratio of single fine particles to all solid components in the aqueous coating liquid is preferably 50 to 100% by weight. If this ratio is less than 50% by weight, the releasability of the coating film and the adhesiveness with the silicone resin layer when further laminated with the coating film are insufficient.

The aqueous coating liquid usually has a solid content concentration of 1 to 30% by weight, and is preferably used in an amount of 2 to 20% by weight in order to improve the drying property and coatability of the aqueous coating liquid.
The aqueous coating solution may contain a small amount of organic solvent.

[Coating of coating film] In the present invention, a coating film is coated on at least one side of a polyester film by applying the above-mentioned aqueous coating liquid, followed by heat drying and stretching. As the method, any known coating method can be applied, for example, a gravure coating method, a reverse roll coating method, a die coating method, a kiss coating method, a reverse kiss coating method, an offset gravure coating method, a Meyer bar coating method, a roll brush method, a spray. The coating method, the air knife coating method, the impregnation method, the curtain coating method and the like can be applied alone or in combination. The wet coating amount of the aqueous coating liquid is 1 to 1 m ² of the running film.
20 g, especially 2 to 12 g is preferred. When the coating amount is within this range, the aqueous coating liquid is easily dried and coating spots are less likely to occur, which is preferable.

The polyester film to which the aqueous coating solution is applied in the present invention is, for example, an unstretched film obtained by heat-melting polyester to form a film as it is; an unstretched film in a longitudinal direction (longitudinal direction) or a lateral direction (width direction). A uniaxially stretched film which has been stretched in one of the two directions; a biaxially stretched film which is obtained by sequentially stretching a uniaxially stretched film in the longitudinal direction or the transverse direction in the transverse direction or in the longitudinal direction (further stretchable), or an unstretched film in the longitudinal direction. And a biaxially stretched film which is simultaneously stretched in two transverse directions (which can be further stretched);
A biaxially stretched heat-treated film in which the biaxially stretched film is heat-set and / or heat-relaxed (further stretchable) can be mentioned.

The thickness of the polyester film is preferably 10 to 1000 μm for the unstretched film, 2 to 500 μm for the uniaxially stretched film, and 1 to 300 μm for the biaxially stretched film and the biaxially stretched heat-treated film.

The aqueous coating solution is applied to a stretchable film of the above polyester films, for example, a uniaxially stretched film, particularly a uniaxially stretched film in the machine direction, and dried and stretched to obtain a film having strong adhesion. And is preferable because the laminated film can be produced efficiently. For example, polyester is heat-melted, extruded into a sheet and cooled to obtain an unstretched film, and the unstretched film is stretched in the machine direction to form a uniaxially stretched film, and then an aqueous coating solution is applied and dried to obtain a transverse direction. The film is stretched, and if necessary, re-stretched in the longitudinal and transverse directions and then heat-treated to form a laminated film having a coating film applied thereon.

The thickness of the applied coating film is 0.005 to 3 μm.
m, particularly 0.015 to 1 μm is preferable. If the thickness of the coating film is less than 0.005 μm, the releasability may be insufficient, and if it exceeds 1 μm, the coating film may be easily scraped, which is not preferable.

[Drying and Stretching Conditions] After applying the aqueous coating liquid in the present invention, the drying temperature is preferably 70 to 130 ° C. because the coating liquid can be dried quickly. The heating for this drying can also serve as the heating during the process of stretching the polyester film. The stretching temperature of the polyester film may be 80 to 170 ° C, and the heat treatment temperature may be 170 to 260 ° C.

[Release Film] The laminated film of the present invention can be used as a release film for releasing a process or protecting an adhesive. Incidentally, the release film for the step release is a film used in the step of producing a resin sheet such as a vinyl chloride sheet or a polyurethane sheet. For example, an aqueous liquid such as vinyl chloride or polyurethane sol is used on the surface of the release film. It is a film used for obtaining a vinyl chloride sheet, a polyurethane sheet or the like by coating the composition on a mold release film and heating and drying to form a resin sheet on the mold release film, and then peeling the mold release film. Further, the release film for protecting the pressure-sensitive adhesive is a film used for protecting the surface of a pressure-sensitive adhesive tape or the like having a pressure-sensitive adhesive layer as a surface layer, and when the pressure-sensitive adhesive tape or the like is used, the release film is used. Peel off and use.

[Silicone resin layer] In the present invention,
In order to obtain a laminated film having further excellent releasing property, a releasing layer containing a silicone resin can be further provided on the coating film. A polydimethylsiloxane polymer obtained by addition polymerization or condensation polymerization is used as the silicone resin, and the silicone resin (S) can be used. In particular, a silicone-acrylic copolymer is preferably used in order to improve the adhesion between the release layer and the coating film.

[0035]

EXAMPLES The present invention will be described in more detail with reference to examples. Each characteristic value was measured by the following method.

1. Releasability A vinyl chloride sol is applied to the coated surface of the polyester film, and after drying, a cellophane tape is attached to support the vinyl chloride layer to improve the peeling force when peeling the coating surface and the vinyl chloride layer. It is measured and shown in g / 62 mm width.

2. Adhesion to base film Two laminated polyester films are laminated so that the coated surface and the non-coated surface face each other, and 135 g / 2 cm
After repeatedly rubbing under the load of ² , the state of the coating film surface is observed and the following ranking is performed. A: Almost no change in the coating film surface .... Good adhesion. B: Slightly scraped coating surface..Slightly good adhesion. C: Slightly scraped coating surface.

3. Backside transferability The coated and uncoated surfaces of the polyester film are placed on top of each other and a load of 6 kg / cm ² is applied, and after holding for 5 hours, an adhesive tape is applied to the uncoated surface of the film and peeled off. The strength (Pa) was measured. Further, the peel strength (P ₀ ) was similarly measured in the case where the polyester film non-coated surfaces were superposed on each other. Then, the back surface transfer degree (T) was obtained from the values of P ₀ and Pa by the following formula, and the back surface transferability was evaluated according to the following criteria.

[0039]

## EQU1 ## T = [(P ₀ −Pa) / P ₀ ] × 100 A: T ≦ 15 …… good rear transferability B: 15 <T ≦ 30 …… somewhat good rear transfer C: T> 30 … Bad transferability

[Example 1] Polyethylene-2,6-naphthalenedicarboxylate having an intrinsic viscosity of 0.64 was melted and cast on a cooling drum, and then stretched 3.1 times in the machine direction to obtain a uniaxially stretched film. did. On one side of this uniaxially stretched film, methyl methacrylate (59 mol%), methyl acrylate (13 mol%), ethyl acrylate (13
Mol%), potassium acrylate (4 mol%) and glycidyl methacrylate (11 mol%) copolymer (A-1;
A composition comprising 51 parts by weight of an average molecular weight of 39,850) and 49 parts by weight of a hydroxyl group-containing polydimethylsiloxane having a hydroxyl value of 63 (S-1; average molecular weight of 9,930) is dissolved in a tetrahydrofuran / acetonitrile mixed solvent to prepare water / ethanol. Single fine particles obtained by adding a mixture to precipitate fine particles containing an acrylic resin and a silicone resin in a single particle and then distilling off the solvents (B-1; average particle size in water 286 nm, In the particle size distribution chart, the peak is single) 78% by weight (solid content), and the average particle size 54 nm is 7% by weight of silicon oxide.
And polyoxyethylene nonylphenyl ether 15
A 4% by weight aqueous coating solution of a composition of 1% by weight was applied with a kiss roll coater. Then, the coated film was dried at 105 ° C., stretched 4.9 times in the transverse direction, and further heat treated at 217 ° C. to form a laminated film having a thickness of 42 μm. The coating thickness of this film was 0.03 μm. The characteristics of this laminated film are shown in Table 1.

[Examples 2 to 8 and Comparative Examples 1 to 3] Properties of a laminated film obtained in the same manner as in Example 1 except that the composition of the coating liquid and the coating film thickness were changed as shown in Table 1. Is shown in Table 1.

[0042]

[Table 1]

In the solid content composition of the coating liquid in Table 1, [B-
1], [B-2], [B-3], [S-4], [S-
5] and [A-2] are fine particles having the following compositions, respectively.

[B-1]: Methyl methacrylate (59 mol%), methyl acrylate (13 mol%), ethyl acrylate (13 mol%), potassium acrylate (4 mol%) and glycidyl methacrylate (11). Mol%) copolymer (A-1; average molecular weight 39,850) 51 parts by weight and hydroxyl group-containing polydimethylsiloxane having a hydroxyl value of 63 (S-1; average molecular weight 9,930) 49 parts by weight. Dissolve in tetrahydrofuran / acetonitrile mixed solvent, add water / ethanol mixture to precipitate as fine particles containing acrylic resin and silicone resin in one particle, and then distill off the solvents to obtain single fine particles (in water The average particle size of the single fine particles of 286 nm, the peak is single in the particle size distribution chart).

[B-2]: 47 parts by weight of the copolymer of A-1 and 53 parts by weight of a carboxyl group- and epoxy group-containing polydimethylsiloxane having an acid value of 52 and an epoxy value of 986 (S-2; average molecular weight 8,540). % By using the same method as in Example 1 to form single fine particles,
Single fine particles obtained by adjusting H to 7 with an alkali (average particle diameter of single fine particles in water is 245 nm, peak is single in particle size distribution chart).

[B-3]: 54 parts by weight of the copolymer of A-1 and 46 parts by weight of a carboxyl group- and epoxy group-containing polydimethylsiloxane having an acid value of 45 and an epoxy value of 843 (S-3; average molecular weight 9,670). Part of the composition was made into single fine particles by the same method as in Example 1, and the water solvent P was added.
Single fine particles obtained by adjusting H to 7 with an alkali (average particle diameter of single fine particles in water is 266 nm, peak is single in particle size distribution chart).

[S-4]: Carboxyl group- and epoxy group-containing polydimethylsiloxane (average molecular weight: 9,460) having an acid value of 54 and an epoxy value of 954 (average molecular weight: 9,460) was formed into fine particles by the same method as in Example 1, and then a water solvent was used. Fine particles obtained by adjusting pH to 7 with alkali (average particle diameter of single fine particles in water is 266 nm, peak is single in particle size distribution chart).

[A-2]: Methyl methacrylate (61 mol%), ethyl acrylate (14 mol%), butyl acrylate (10 mol%), potassium acrylate (3 mol%) and glycidyl methacrylate (12). (Mol%) copolymer (average molecular weight: 45,850) was made into fine particles by the same method as in Example 1 (average particle size in water: 233 nm). [S-5]: Polydimethylsiloxane containing a carboxyl group and an epoxy group having an acid value of 42 and an epoxy value of 922 (average molecular weight: 8,530) was made into fine particles by the same method as in Example 1, and then the pH of the aqueous solvent was adjusted to 7 Fine particles obtained by adjusting with an alkali (average particle diameter in water: 273 nm).

[0049]

In the present invention, since an aqueous coating liquid containing an acrylic resin and a silicone resin in a single fine particle is used, the acrylic resin component and the silicone resin component constituting the coating film become uniform, and the coating film It is possible to obtain a laminated film which is excellent in adhesion to the base film and release property of the coating film and which is useful for process materials, release materials and the like.

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Claims (3)

[Claims] 1. A single fine particle emulsion or dispersion in which the composition of one particle is composed of 25 to 75% by weight of an acrylic resin (A) and 75 to 25% by weight of a silicone resin (S) on at least one side of a polyester film. A laminated film provided with a coating film formed by applying an aqueous coating solution containing the composition, drying and stretching. 2. The laminated film according to claim 1, which is used as a release film for releasing a process or protecting an adhesive. 3. The laminated film according to claim 1, which is used for a release film in which a release layer containing a silicone resin is further provided on the coating film.