JP7496675B2 - Decorative Film - Google Patents

Description

The present invention relates to a decorative film.

A traditional method for imparting design to a substrate (adherend) is to attach a decorative film to the substrate.

Furthermore, functional films having a specific function such as solar radiation shielding are applied to windows made of glass in buildings and windows made of glass in vehicles such as automobiles. Such functional films are required to have high adhesion (durability) to the window after application. For example, Patent Document 1 discloses an optical film pressure-sensitive adhesive composition and an optical film that satisfy high adhesion to the window after application even after being placed in a high-temperature environment. It is also disclosed that the weather resistance is improved and deterioration of properties over time due to light irradiation, etc. is suppressed by adding a light stabilizer to the optical film pressure-sensitive adhesive composition.

International Publication No. 2017/168869

When decorative films are exposed to high temperature environments (for example, environments exposed to direct sunlight), the thermal shrinkage of the decorative film can cause it to peel off from the substrate (adherend) such as a window, resulting in a loss of design.

Moreover, there are two types of window decoration: exterior application, where the decorative film is applied to the outside of the window, and interior application, where the decorative film is applied to the inside of the window. Interior application has the advantage of reducing construction costs, since there is no need to set up scaffolding, even on high-rise floors. However, because direct sunlight hits the adhesive layer of the decorative film through the window, the adhesive layer must have excellent weather resistance.

The present invention was made in consideration of the above-mentioned current situation, and aims to provide a decorative film with excellent weather resistance.

The present inventors have investigated the composition that forms the adhesive layer of a decorative film in which a polyvinyl chloride film layer, an adhesive layer, and a separator are laminated in this order as the constituent components of the decorative film. As a result, they have found that by using a specific adhesive and further including specific amounts of a hindered amine light stabilizer and an ultraviolet absorber in the adhesive layer, heat shrinkage is suppressed, and as a result, excellent weather resistance is obtained, thus completing the present invention.

The decorative film of the present invention is characterized in that a polyvinyl chloride film layer, an adhesive layer, and a separator are laminated in this order, and the adhesive layer is made of an adhesive composition containing an acrylic adhesive having a weight average molecular weight of 500,000 to 2,000,000, a hindered amine light stabilizer, and an ultraviolet absorber, the content of the hindered amine light stabilizer is 0.5 to 3.2 parts by weight per 100 parts by weight of the acrylic adhesive, the content of the ultraviolet absorber is 0.5 to 4.2 parts by weight per 100 parts by weight of the acrylic adhesive, and the total content of the hindered amine light stabilizer and the ultraviolet absorber is 2 parts by weight or more per 100 parts by weight of the acrylic adhesive.

The acrylic adhesive preferably contains a first acrylic adhesive having a weight average molecular weight of 1.5 million or more and a second acrylic adhesive having a weight average molecular weight of 1 million or less.

The compounding ratio of the first acrylic adhesive to the second acrylic adhesive is preferably 25:75 to 99:1.

The hindered amine light stabilizer is preferably at least one selected from the group consisting of N- _CH3 type, NO-alkyl type, and N-acyl type.

The above-mentioned UV absorber is preferably a benzotriazole-based UV absorber and/or a benzophenone-based UV absorber.

The decorative film of the present invention is preferably an inkjet media.

The decorative film of the present invention is preferably used on a transparent substrate.

The transparent substrate is preferably glass.

The decorative film of the present invention is preferably used for lining the inside of a transparent substrate.

The decorative film of the present invention can provide a decorative film with excellent weather resistance. Therefore, when attached to a substrate, the design is maintained for a long period of time, even in a high-temperature environment. Furthermore, when the decorative film of the present invention is attached to the inside of a transparent substrate such as a window, even when the adhesive layer of the decorative film is exposed to direct sunlight through a window or the like, no thermal shrinkage occurs and the design is maintained for a long period of time.

1 is a schematic cross-sectional view showing an example of a decorative film of the present invention.

(Decorative film)
The decorative film of the present invention is characterized in that a polyvinyl chloride film layer, a pressure-sensitive adhesive layer, and a separator are laminated in this order, the pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive having a weight-average molecular weight of 500,000 to 2,000,000, a hindered amine light stabilizer, and an ultraviolet absorber, the content of the hindered amine light stabilizer being 0.5 to 3.2 parts by weight relative to 100 parts by weight of the acrylic pressure-sensitive adhesive, the content of the ultraviolet absorber being 0.5 to 4.2 parts by weight relative to 100 parts by weight of the acrylic pressure-sensitive adhesive, and the total content of the hindered amine light stabilizer and the ultraviolet absorber being 2 parts by weight or more relative to 100 parts by weight of the acrylic pressure-sensitive adhesive.

In this specification, "film" is synonymous with "sheet," and no distinction is made between the two based on thickness.

In this specification, "X to Y" means "X or more and Y or less."

Figure 1 is a schematic cross-sectional view showing an example of the decorative film of the present invention. As shown in Figure 1, the decorative film 1 is formed by laminating a polyvinyl chloride film layer 2, an adhesive layer 3, and a separator 4. In this specification, "A and B are laminated" and "A and B are laminated" include cases where A and B are in contact with each other, as well as cases where another layer is disposed between A and B. By making the decorative film 1 have such a laminated structure, the color of the printed layer is easily visible even when the printed layer is present on the polyvinyl chloride film layer 2 side of the decorative film 1, and even when the printed layer is viewed from the adhesive layer side of the decorative film, the desired design can be easily obtained using the decorative film 1.

(Polyvinyl chloride film layer)
The polyvinyl chloride film layer 2 is a film layer made of a polyvinyl chloride resin. Since polyvinyl chloride films have good stretchability and are difficult to break, they can be easily attached to three-dimensional curved surfaces. In addition, since they have excellent printability and soften at a relatively low temperature (about 100°C), they are suitable as a support for decorative molding films. The polyvinyl chloride resin is not particularly limited, but can be obtained, for example, by adding a plasticizer to polyvinyl chloride. The polyvinyl chloride having a degree of polymerization of 800 to 1200 is preferably used.

The plasticizer may be one that is commonly used in the field of films, and examples of such plasticizers include phthalate diesters such as octyl phthalate (di-2-ethylhexyl phthalate), dibutyl phthalate, dinonyl phthalate, and diisononyl phthalate, aliphatic dibasic acid diesters such as dioctyl adipate and dioctyl sebacate, phosphate triesters such as tricresyl phosphate and trioctyl phosphate, epoxy-based plasticizers such as epoxidized soybean oil and epoxy resins, and polymer polyester plasticizers. The preferred lower limit of the amount of the plasticizer to be added relative to 100 parts by weight of the vinyl chloride is 10 parts by weight, and the preferred upper limit is 30 parts by weight.

The polyvinyl chloride resin may contain a heat stabilizer. As the heat stabilizer, those commonly used in the field of films can be used, and examples thereof include metal organic acid compounds containing lead (Pb), barium (Ba), zinc (Zn), calcium (Ca), tin (Sn), etc.

The preferred lower limit of the thickness of the polyvinyl chloride film layer 2 is 40 μm, the preferred upper limit is 200 μm, the more preferred lower limit is 50 μm, the more preferred upper limit is 150 μm, the even more preferred lower limit is 70 μm, and the even more preferred upper limit is 120 μm. If the thickness of the polyvinyl chloride film layer 2 is less than 40 μm, the inkjet ink may not be absorbed sufficiently, causing bleeding and impairing drawing properties. Also, if the thickness of the polyvinyl chloride film layer exceeds 200 μm, the flexibility of the film may be impaired, and workability may be deteriorated.

(Adhesive Layer)
The pressure-sensitive adhesive layer 3 is made of a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive having a weight-average molecular weight of 500,000 to 2,000,000 as a main agent, and further containing a hindered amine light stabilizer and an ultraviolet absorber. By using a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive having a specific weight-average molecular weight as a main agent, and specific amounts of a hindered amine light stabilizer and an ultraviolet absorber, the pressure-sensitive adhesive layer 3 has excellent weather resistance.

The acrylic adhesive has a weight-average molecular weight of 500,000 to 2,000,000. When the weight-average molecular weight of the acrylic adhesive is within the above range, it is advantageous in that sufficient adhesive strength can be exerted and dimensional stability is also excellent. On the other hand, when the weight-average molecular weight of the acrylic adhesive is less than 500,000, the dimensions may change due to the influence of high temperature environments or solvent ink. On the other hand, when the weight-average molecular weight of the acrylic adhesive is more than 2,000,000, it may be difficult to exert the desired adhesive strength.
The weight average molecular weight of the acrylic pressure-sensitive adhesive is preferably from 1,000,000 to 2,000,000, and more preferably from 1,300,000 to 1,800,000.

The acrylic adhesive preferably contains a first acrylic adhesive having a weight-average molecular weight of 1.5 million or more and a second acrylic adhesive having a weight-average molecular weight of 1 million or less. This is because containing multiple types of acrylic adhesives with different weight-average molecular weights makes it easier to adjust the adhesive properties of the acrylic adhesive.

The compounding ratio of the first acrylic pressure-sensitive adhesive to the second acrylic pressure-sensitive adhesive is preferably 25:75 to 99:1. This is because the weather resistance of the pressure-sensitive adhesive layer is improved when the weight-average molecular weight of the acrylic pressure-sensitive adhesive is 1,000,000 to 2,000,000.
The compounding ratio of the first acrylic pressure-sensitive adhesive to the second acrylic pressure-sensitive adhesive is more preferably from 25:75 to 80:20, further preferably from 25:75 to 70:30, and most preferably from 30:70 to 50:50.

Examples of the acrylic adhesive having a weight average molecular weight of 500,000 to 2,000,000 include acrylic acid ester polymers having a weight average molecular weight of 500,000 to 2,000,000.

Examples of the acrylic acid ester polymer include polymers obtained by copolymerizing (meth)acrylic monomers having no functional group, (meth)acrylic monomers having functional groups, and, if necessary, other monomers copolymerizable with these monomers.

The (meth)acrylic monomers not having the above-mentioned functional groups are not particularly limited, and examples thereof include alkyl esters of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, benzyl (meth)acrylate, phenylethyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate ester; and aryl esters of (meth)acrylic acid such as phenyl (meth)acrylate and methylphenyl (meth)acrylate.

The (meth)acrylic monomers having the above-mentioned functional groups (carboxyl group, hydroxyl group, amino group, amide group, methylol group, epoxy group, etc.) are not particularly limited, and examples thereof include carboxyl group-containing monomers such as (meth)acrylic acid, itaconic acid, crotonic acid, (anhydrous) maleic acid, and fumaric acid; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; amino group-containing monomers such as aminomethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and vinylpyridine; amide group-containing monomers such as (meth)acrylamide, N-methyl (meth)acrylamide, and N-ethyl (meth)acrylamide; amide group and methylol group-containing monomers such as N-methylol (meth)acrylamide and dimethylol (meth)acrylamide; and epoxy group-containing monomers such as glycidyl (meth)acrylate.

The copolymerizable other monomer is not particularly limited, and examples thereof include styrene-based monomers, vinyl-based monomers, etc. Examples of the styrene-based monomers include styrene; alkyl styrenes such as methylstyrene, dimethylstyrene, and trimethylstyrene; and halogenated styrenes such as fluorostyrene and chlorostyrene. Examples of the vinyl-based monomers include vinylpyrrolidone, divinylbenzene, vinyl acetate, acrylonitrile; and conjugated diene monomers such as butadiene and isoprene.
The above-mentioned monomers may be used alone or in combination of two or more kinds.

As the acrylic ester polymer, it is preferable to use one that contains butyl (meth)acrylate, octyl (meth)acrylate, phenylethyl (meth)acrylate, or phenoxyethyl (meth)acrylate as the (meth)acrylic monomer that does not have the functional group.

The weight average molecular weight (Mw) of the acrylic pressure-sensitive adhesive is a value measured in terms of polystyrene by gel permeation chromatography (GPC) under the following measurement conditions.
Device name: HLC-8120 (Tosoh Corporation)
Column: G7000HXL 7.8 mm ID x 30 cm 1 column, GMHXL 7.8 mm ID x 30 cm 2 columns, G2500HXL 7.8 mm ID x 30 cm 1 column (manufactured by Tosoh Corporation)
Sample concentration: diluted with tetrahydrofuran to 1.5 mg/ml Mobile phase solvent: tetrahydrofuran Flow rate: 1.0 ml/min
Column temperature: 40°C

Examples of the hindered amine light stabilizer include N-H type, N- _CH3 type, NO-alkyl type and N-acyl type hindered amine light stabilizers, and among them, at least one type selected from the group consisting of N- _CH3 type, NO-alkyl type and N-acyl type is preferable. This is because a hindered amine light stabilizer with low basicity has excellent processability and is easy to handle.
Moreover, the above hindered amine-based light stabilizer is more preferably an N- _CH3 type and/or an N-acyl type, and further preferably an N- _CH3 type.

The content of the hindered amine light stabilizer is 0.5 to 3.2 parts by weight per 100 parts by weight (solid content) of the acrylic adhesive. If the content is less than 0.5 parts by weight, the improvement in weather resistance by the hindered amine light stabilizer is insufficient. If the content exceeds 3.2 parts by weight, the transparency of the adhesive layer 3 decreases, and when the decorative film of the present invention is applied to the inside of a window, visibility from outside the window may decrease. The content of the hindered amine light stabilizer is preferably 1.0 to 4.0 parts by weight per 100 parts by weight (solid content) of the acrylic adhesive.

Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and triazine-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers and/or benzophenone-based ultraviolet absorbers are preferred. Benzotriazole-based ultraviolet absorbers and benzophenone-based ultraviolet absorbers are sufficiently compatible with acrylic adhesives, so that an adhesive layer 3 having good weather resistance can be obtained.
As the ultraviolet absorbing agent used in the present invention, a benzotriazole-based ultraviolet absorbing agent is more preferable because it has a high ultraviolet absorbing effect.

Examples of benzotriazole-based ultraviolet absorbers include 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)benzotriazole, 2-(2-hydroxy-3,5-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,5-dicumylphenyl)benzotriazole, 2,2' -methylenebis(4-tert-octyl-6-benzotriazolylphenol), polyethylene glycol ester of 2-(2-hydroxy-3-tert-butyl-5-carboxyphenyl)benzotriazole, 2-[2-hydroxy-3-(2-acryloyloxyethyl)-5-methylphenyl]benzotriazole, 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-butylphenyl]benzotriazole, 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-octylphenyl]benzotriazole, 2-[2-hydroxy-3-(2-methacryloyloxyethyl)-5-tert-butylphenyl]-5-chlorobenzotriazole, 2-[2-hydroxy-5-(2-methacryloyloxyethyl)- Examples of the benzotriazole-based ultraviolet absorbers include 2-[2-hydroxy-3-tert-butyl-5-(2-methacryloyloxyethyl)phenyl]benzotriazole, 2-[2-hydroxy-3-tert-amyl-5-(2-methacryloyloxyethyl)phenyl]benzotriazole, 2-[2-hydroxy-3-tert-butyl-5-(3-methacryloyloxypropyl)phenyl]-5-chlorobenzotriazole, 2-[2-hydroxy-4-(2-methacryloyloxymethyl)phenyl]benzotriazole, 2-[2-hydroxy-4-(3-methacryloyloxy-2-hydroxypropyl)phenyl]benzotriazole, and 2-[2-hydroxy-4-(3-methacryloyloxypropyl)phenyl]benzotriazole. These benzotriazole-based ultraviolet absorbers may be used alone or in combination of two or more.

Examples of benzophenone-based UV absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, and 5,5'-methylenebis(2-hydroxy-4-methoxybenzophenone). These benzophenone-based UV absorbers may be used alone or in combination of two or more.

The content of the ultraviolet absorber is 0.5 to 4.2 parts by weight per 100 parts by weight (solid content) of the acrylic adhesive. If the content is less than 0.5 parts by weight, the improvement in weather resistance by the ultraviolet absorber will be insufficient. If the content exceeds 4.2 parts by weight, the transparency of the adhesive layer 3 will decrease, and when the decorative film 1 of the present invention is applied to the inside of a window, visibility from outside the window may decrease. The content of the ultraviolet absorber is preferably 1.0 to 4.0 parts by weight per 100 parts by weight (solid content) of the acrylic adhesive.

The total content of the hindered amine light stabilizer and the ultraviolet absorber in the pressure-sensitive adhesive layer 3 is 2 parts by weight or more relative to 100 parts by weight (solid content) of the acrylic pressure-sensitive adhesive. If the total content of the hindered amine light stabilizer and the ultraviolet absorber is less than 2 parts by weight, sufficient weather resistance may not be obtained.
The total content of the hindered amine light stabilizer and the ultraviolet absorber in the pressure-sensitive adhesive layer 3 is preferably 3.5 parts by weight or more, more preferably 5 parts by weight or more, relative to 100 parts by weight (solid content) of the acrylic pressure-sensitive adhesive. The total content of the hindered amine light stabilizer and the ultraviolet absorber in the pressure-sensitive adhesive layer 3 is preferably 10 parts by weight or less, more preferably 8 parts by weight or less, relative to 100 parts by weight (solid content) of the acrylic pressure-sensitive adhesive. If the total content of the hindered amine light stabilizer and the ultraviolet absorber exceeds 10 parts by weight, the transparency of the pressure-sensitive adhesive layer 3 may decrease.

The adhesive composition may contain a curing agent. By containing a curing agent, the dimensional stability of the decorative film can be improved. The curing agent is not particularly limited, and examples thereof include isocyanate-based curing agents such as tolylene diisocyanate and hexamethylene diisocyanate, epoxy-based curing agents such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether and tetraglycidyl xylene diamine, metal chelating agents such as Al, Ni and Zn, and amino resin-based curing agents such as melamine compounds.

The above curing agent is preferably an epoxy-based curing agent such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, or tetraglycidyl xylene diamine.

The content of the curing agent is preferably 0.01 to 0.1 parts by weight (solid content) relative to 100 parts by weight (solid content) of the acrylic adhesive, and more preferably 0.025 to 0.04 parts by weight (solid content).
If the amount of the curing agent is less than 0.01 parts by weight (solid content), the dimensional stability and weather resistance may decrease and the mesh size may increase. If the amount of the curing agent is more than 0.1 parts by weight (solid content), the adhesive may become too elastic, which may cause the adhesive layer 3 to have poor adhesion to the substrate, leading to the risk of lifting or peeling.

The above adhesive composition may contain various additives such as stabilizers, plasticizers, softeners, fillers, tackifiers, dyes, pigments, and inorganic fillers, as necessary.

The thickness of the adhesive layer 3 is preferably 10 to 40 μm. If it is less than 10 μm, sufficient adhesion may not be obtained, while if it exceeds 40 μm, the initial adhesive strength becomes high, which may make re-application difficult. In addition, it is not economical because a large amount of adhesive composition is used. A more preferable lower limit of the thickness of the adhesive layer 3 is 15 μm, and a more preferable upper limit is 30 μm.

The method for forming the adhesive layer 3 is not particularly limited, and any conventionally known method can be used, such as a method in which an adhesive composition is applied directly onto the separator 4 using a bar coater or the like, and then dried. In this case, the adhesive layer 3 formed on the separator 4 is bonded to the polyvinyl chloride film layer 2 to produce the decorative film 1. The decorative film is further processed as necessary, such as being cut and wound into a roll.

(separator)
The separator 4 may be one that is commonly used in the field of films. The separator 4 may be a release film or a release paper. Examples of the release film include resin films such as polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, and polypropylene that have been treated to be easily peeled. Examples of the release paper include paper such as fine paper or glassine paper that has been treated to be easily peeled. Examples of the easy peeling treatment include a method of coating the surface of the resin film or paper that comes into contact with the adhesive layer with a silicone-based, alkyd-based, or fluorine-based release agent. The separator 4 may be surface-treated only on the surface on the adhesive layer side. The thickness of the separator is preferably 12 to 200 μm, more preferably 25 to 150 μm.

The polyvinyl chloride film layer 2 may be printed on the surface opposite the adhesive layer 3. Printing on the polyvinyl chloride film layer 2 may be performed by, for example, inkjet printing, gravure printing, screen printing, rotary screen printing, flexographic printing, offset printing, electrostatic printing, etc. In addition, the polyvinyl chloride film layer may have fine irregularities on the surface opposite the adhesive layer by embossing or the like.

The polyvinyl chloride film layer 2 is preferably provided with a printed layer by inkjet printing on the surface opposite to the adhesive layer 3. That is, the decorative film 1 is preferably an inkjet medium. Generally, when a decorative film is inkjet printed, the solvent used in the inkjet penetrates the decorative film, deteriorating the dimensional stability of the decorative film and the heat resistance and weather resistance of the adhesive layer. However, the decorative film 1 exhibits sufficient dimensional stability, heat resistance and weather resistance even as an inkjet medium.

Specific examples of solvent-based inks used in inkjet printing include SS21 ink, ES3 ink (both manufactured by Mimaki Engineering Co., Ltd.), and Eco Sol MAX (manufactured by Roland).

The polyvinyl chloride film layer 2 may have a protective film layer on the side opposite to the adhesive layer 3. As the protective film, a film that is commonly used in the field of films can be used. Examples of the protective film include polyethylene terephthalate (PET) resins, polypropylene (PP) resins, polycarbonate resins, etc.

The manufacturing method of the decorative film is not particularly limited, but for example, the polyvinyl chloride film layer 2 can be formed by melt-kneading the polyvinyl chloride resin using a Banbury mixer or the like, and then calendering the mixture.

The decorative film 1 is attached to a substrate via the adhesive layer 3 after the separator 4 has been peeled off. The decorative film 1 is suitable for use on transparent substrates such as windows.

The decorative film 1 has excellent adhesive strength and dimensional stability at room temperature and high temperature, so that the decorative film 1 is unlikely to lift or peel off, not only when used at room temperature but also when used in an environment exceeding 65°C, for example.

The decorative film 1 may be applied, for example, by peeling off the separator 4 from the decorative film 1 and attaching it to the substrate via the adhesive layer 3. The decorative film 1 can be attached at room temperature, or may be attached while being heated with a dryer or the like. The decorative film 1 can also be attached to the substrate by hand or with a squeegee. The decorative film 1 may also be attached by a method commonly used in the technical field to which the present invention pertains (such as a lamination method).

The material of the transparent substrate is not particularly limited, and examples include glass, resins such as polycarbonate resins, acrylic resins, and styrene resins, and acrylonitrile-butadiene-styrene copolymers (ABS resins), with glass being preferred.

The substrate is not particularly limited, but examples thereof include vehicles such as bicycles, motorbikes, automobiles, buses, and trains; helmets; ships; aircraft such as airplanes and helicopters; household items such as furniture and home appliances; office supplies such as cabinets, desks, and personal computers; walls, floors, ceilings, roofs, pillars, signs, doors, and gates of buildings; or building materials at construction sites, or parts thereof. The decorative film is preferably used by interior application, and the substrate is preferably a transparent substrate. Examples of transparent substrates include transparent members and transparent parts used in building materials and vehicle materials, such as windows of buildings, windows of vehicles such as automobiles, buses, and trains; windows of aircraft such as airplanes and helicopters; display panels; and partition panels.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1
A polyvinyl chloride resin was obtained by adding 28 parts by weight of diisononyl phthalate as a plasticizer to 100 parts by weight of vinyl chloride resin having an average degree of polymerization of 800. The obtained polyvinyl chloride resin was melt-kneaded in a Banbury mixer, and then calendered to produce a polyvinyl chloride film layer. The thickness of the polyvinyl chloride film layer was 100 μm. Next, 100 parts by weight (solids) of an acrylic adhesive (SK1506A, manufactured by Soken Chemical Industries, Ltd.) having a weight average molecular weight of 640,000 as a main agent, 0.04 parts by weight (solids) of an epoxy curing agent (E-5C, manufactured by Soken Chemical Industries, Ltd.), 3.2 parts by weight of a hindered amine light stabilizer (hereinafter also referred to as HALS) (LA-52, manufactured by Soken Chemical Industries, Ltd.), and 2.1 parts by weight of a benzophenone ultraviolet absorber (ADEKA 1413, manufactured by ADEKA Corporation) (melting point 47-49°C, molecular weight 326) were added to prepare an adhesive composition. As a separator, a release paper laminated with polyethylene on both sides of a high-quality paper and coated with a silicone-based release agent was used, and the obtained adhesive composition was applied onto the separator using a comma coater so that the thickness of the adhesive layer after drying was 20 μm. Then, it was transferred to a polyvinyl chloride film layer to obtain the decorative film of Example 1.

(Examples 2 to 4)
The decorative films according to Examples 2 to 4 were obtained in the same manner as in Example 1, except that the contents of the acrylic adhesive having a weight-average molecular weight of 640,000 (SK1506A, manufactured by Soken Chemical Industries, Ltd.) and the acrylic adhesive having a weight-average molecular weight of 2,000,000 (SK2006HE, manufactured by Soken Chemical Industries, Ltd.) were changed to the contents shown in Table 1 below so that the average molecular weight of the main acrylic adhesive (100 parts by weight) would be the weight-average molecular weight shown in Table 1 below.

(Comparative Examples 1 to 5)
The decorative films according to Comparative Examples 1 to 5 were obtained in the same manner as in Example 1, except that the type of the acrylic adhesive (100 parts by weight) as the main component and the content of the curing agent were changed to those shown in Table 2 below, and the hindered amine light stabilizer (HALS) and the ultraviolet absorber (UVA) were not used.
SK1435 shown in Table 2 is an acrylic adhesive (manufactured by Soken Chemical Industries, Ltd.) having a weight average molecular weight of 500,000.

(Examples 5 to 11 and Comparative Example 6)
The type of ultraviolet absorber (UVA) used in Example 3 was changed to a benzotriazole-based ultraviolet absorber (LA-29 manufactured by ADEKA Corporation) (melting point 102-106°C, molecular weight 323), the content of HALS and the content of the benzotriazole-based ultraviolet absorber were changed to the contents shown in Table 3 below, and the content of the curing agent was changed to the content shown in Table 3 below. Except for this, the decorative films according to Examples 5 to 11 and Comparative Example 6 were obtained in the same manner as in Example 3.

(Examples 12 and 13)
Decorative films according to Examples 12 and 13 were obtained in the same manner as in Example 3, except that the content of HALS (LA-52) used in Example 3 was changed to the content shown in Table 4 below.

(Examples 14 and 15)
The decorative films according to Examples 14 and 15 were obtained in the same manner as in Example 3, except that the type of HALS used in Example 3 was changed from LA-52 (N- _CH3 type) to LA-81 (manufactured by ADEKA Corporation) (NO-alkyl type), and the content of HALS was changed to the content shown in Table 4 below.

(Evaluation of decorative films)
The decorative films obtained in the Examples and Comparative Examples were evaluated for (1) weather resistance, (2) dimensional stability, and (3) adhesion (initial, accelerated condition, and after printing) by the following methods. The evaluation results are shown in Tables 1 to 4 below.

(1) Weather Resistance Cross-Cut Test On the surface of the polyvinyl chloride film layer of each of the decorative films according to the obtained Examples and Comparative Examples opposite to the adhesive layer, a solid print was performed twice with 100% CMYK and 400% ink ejection amount using an inkjet printer ("JV33" manufactured by Mimaki Engineering Co., Ltd.) and a solvent-based ink ("SS21" manufactured by Mimaki Engineering Co., Ltd.), and the print layer was formed by drying for 2 hours. Next, a top film (PVC adhesive sheet) was laminated on the surface on which the print layer was formed, and then the separator of the decorative film on which the print layer and the top film were laminated was peeled off and attached to a glass plate. Then, the sample on the glass plate was cut into a 50 mm square. Next, a cross cut of 40 mm in length and width was made in the center of the sample to obtain samples according to the Examples and Comparative Examples.

A metal weather test (accelerated weather resistance test) was conducted on the adhesive surfaces of the samples of the examples and comparative examples through a glass plate under the following conditions.

(Test condition)
Metal weather tester: Horizontal metalling weather meter (M6t) manufactured by Suga Test Instruments Co., Ltd. Irradiance (kW/m ² ) (300-400 nm): 120
BPT(℃):53
Humidity: 50%
Test cycle: 24 hours of continuous irradiation

The above treatment constitutes one cycle, and metal weather tests were carried out for 48 hours, 96 hours, and 144 hours on each sample of the examples and comparative examples. Note that the 144-hour test was not carried out on some samples. After the test, the mesh size of each sample was measured. The measurement results are shown in Tables 1 to 4.

(Lightfastness Evaluation Criteria)
If the opening size in the weather resistance cross-cut test was 0.6 mm or less in both the machine direction and the width direction after 48 hours and 96 hours of metal weather testing, the weather resistance was evaluated as "good". If the opening size was more than 0.6 mm and less than 1 mm in either the machine direction or the width direction after 48 hours and/or 96 hours of metal weather testing, the weather resistance was evaluated as "good". If the opening size was more than 1 mm in both the machine direction and the width direction after 48 hours and/or 96 hours of metal weather testing, the weather resistance was evaluated as "good".

(2) Dimensional stability test Next, on the surface of the polyvinyl chloride film layer of each of the obtained decorative films according to the examples and comparative examples opposite to the adhesive layer, solid printing was performed twice with 100% CMYK and 400% ink ejection amount using an inkjet printer ("JV33" manufactured by Mimaki Engineering Co., Ltd.) and a solvent-based ink ("SS21" manufactured by Mimaki Engineering Co., Ltd.), and the printed layer was formed by drying for 2 hours. Next, a top film (PVC adhesive sheet) was laminated on the surface on which the printed layer was formed, and then the separator of the decorative film on which the printed layer and the top film were laminated was peeled off and attached to a glass plate and an aluminum plate, respectively. Then, the decorative film on the glass plate and the aluminum plate was cut into 150 mm squares, which were used as samples. Next, a cross cut of 100 mm length and width was made in the center of the sample, and dimensional stability cross-cut test samples according to Examples 1 to 15 and Comparative Example 6 were obtained.

The obtained dimensional stability cross-cut test samples were heated in an oven at 65°C for 48 hours, and the amount of opening was measured after removal. The measurement results are shown in Tables 1, 3, and 4.

(Dimensional Stability Evaluation Criteria)
When the opening amount in the dimensional stability cross-cut test was 0.5 mm or less in the machine direction and width direction, the dimensional stability was evaluated as "good". When the opening amount was more than 0.5 mm and less than 0.8 mm in the machine direction and/or width direction, the dimensional stability was evaluated as "good". When the opening amount was 0.8 mm or more in the machine direction or width direction, the dimensional stability was evaluated as "poor".

(3) Adhesion test (initial adhesion)
The decorative films obtained in Examples 3 and 5 to 15 and Comparative Example 6 were cut into test pieces with a length of 180 mm and a width of 25 mm. The separator was peeled off from each test piece, and the test pieces were attached to a glass plate with a length of 125 mm and a width of 50 mm using a 2 kg pressure roller. After leaving each test piece at room temperature (temperature 23±2°C) and humidity of 50% for 24 hours, a 180° peel test was performed according to a method conforming to JIS Z 0237, and the adhesive strength was measured (under the condition of a peel speed of 300/min). The average value of the measurement results obtained by performing the measurement twice is taken as the initial adhesive strength, and is shown in Tables 3 and 4 below.

(Adhesive strength over time to glass plate)
Each of the decorative films according to Examples 3 and 5 to 15 and Comparative Example 6 was cut into a length of 180 mm and a width of 25 mm to prepare a test piece. The separator was peeled off from each test piece, and the test piece was attached to a glass plate with a length of 125 mm and a width of 50 mm using a 2 kg pressure roller. The glass plate with the test piece attached was then placed in a 60°C oven for 168 hours and removed. After 24 hours of returning to room temperature, a 180° peel test was performed according to the method in accordance with JIS Z 0237, and the adhesive strength was measured (peel speed: 300/min). The average value of the measurement results obtained by performing the measurement twice is shown in Tables 3 and 4 below as the adhesive strength of the glass plate attachment over time.

(Adhesive strength with separator over time)
Each of the decorative films according to Examples 3 and 5 to 15 and Comparative Example 6 was cut into a length of 180 mm and a width of 25 mm to prepare a test piece. The test piece was then placed in a 60°C oven for 168 hours and removed. After the test piece was returned to room temperature, it was attached to a glass plate with a length of 125 mm and a width of 50 mm using a 2 kg pressure roller. After 24 hours, a 180° peel test was performed according to a method conforming to JIS Z 0237, and the adhesive strength was measured (peeling speed: 300/min). The average value of the measurement results obtained by performing the measurement twice is shown in Tables 3 and 4 below as the adhesive strength with a separator over time.

(Adhesive Strength Evaluation Criteria)
When each of the measured adhesive strengths (initial adhesive strength, adhesive strength after attachment to a glass plate over time, adhesive strength with a separator over time) (N/25 mm) was 12 or more, the adhesive strength was evaluated as "good", when any one of them was less than 8, the adhesive strength was evaluated as "poor", and in all other cases the adhesive strength was evaluated as "good".

(Adhesive strength after printing)
On the surface of the polyvinyl chloride film layer of each of the decorative films according to Examples 3 and 12 to 15 opposite to the adhesive layer, a solid print was performed twice with 100% CMYK and 400% ink ejection amount using an inkjet printer ("JV33" manufactured by Mimaki Engineering Co., Ltd.) and a solvent-based ink ("SS21" manufactured by Mimaki Engineering Co., Ltd.), and the print layer was formed by drying for 2 hours. Next, a top film (PVC adhesive sheet) was laminated on the surface on which the print layer was formed, to obtain each sample having a print layer. Each of the samples according to Examples 3 and 12 to 15 was cut into a length of 180 mm and a width of 25 mm to prepare a test piece. The separator was peeled off from each test piece, and the test piece was attached to a glass plate of length 125 mm and width 50 mm using a 2 kg pressure roller. After leaving each sample at room temperature (23±2° C.) and 50% humidity for 24 hours, a 180° peel test was performed according to JIS Z 0237 to measure the adhesive strength (under the condition of a peel speed of 300/min). The average value of the measurement results obtained by performing the measurement twice is shown in Table 4 below as the adhesive strength after printing.

(Adhesive strength evaluation criteria for decorative film after printing)
When each measured adhesive strength (N/25 mm) was 5 or more, the adhesive strength was evaluated as "good", when it was 3 or more but less than 5, the adhesive strength was evaluated as "good", and when it was less than 3, the adhesive strength was evaluated as "poor".

From the results of the examples and comparative examples, it was found that the adhesive composition of the decorative film contains an acrylic adhesive with a weight average molecular weight of 500,000 to 2,000,000, a hindered amine light stabilizer, and an ultraviolet absorber, the content of the hindered amine light stabilizer is 0.5 to 3.2 parts by weight per 100 parts by weight (solid content) of the acrylic adhesive, the content of the ultraviolet absorber is 0.5 to 4.2 parts by weight per 100 parts by weight (solid content) of the acrylic adhesive, and the total content of the hindered amine light stabilizer and the ultraviolet absorber is 2 parts by weight or more per 100 parts by weight (solid content) of the acrylic adhesive, thereby obtaining a decorative film that has excellent adhesion and dimensional stability as well as excellent weather resistance even in an environment where the adhesive layer is exposed to direct sunlight through a transparent substrate.

1: Decorative film 2: Polyvinyl chloride film layer 3: Adhesive layer 4: Separator

Claims (11)

A decorative film in which a polyvinyl chloride film layer, a pressure-sensitive adhesive layer, and a separator are laminated in this order,
The decorative film is an inkjet medium,
the pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive having a weight-average molecular weight of 1,000,000 to 2,000,000 (however, when the acrylic pressure-sensitive adhesive is a mixture of a plurality of acrylic pressure-sensitive adhesives, the weight-average molecular weight refers to the weight-average molecular weight of the mixture) , a hindered amine light stabilizer, and an ultraviolet absorber;
The content of the hindered amine light stabilizer is 0.5 to 3.2 parts by weight based on 100 parts by weight of the acrylic pressure-sensitive adhesive,
The content of the ultraviolet absorbing agent is 0.5 to 4.2 parts by weight based on 100 parts by weight of the acrylic adhesive,
A decorative film, characterized in that a total content of the hindered amine-based light stabilizer and the ultraviolet absorbing agent is 2 parts by weight or more per 100 parts by weight of the acrylic pressure-sensitive adhesive. The decorative film according to claim 1, characterized in that the acrylic adhesive contains a first acrylic adhesive having a weight average molecular weight of 1.5 million or more and a second acrylic adhesive having a weight average molecular weight of 1 million or less. The decorative film according to claim 2, characterized in that the compounding ratio of the first acrylic adhesive to the second acrylic adhesive is 25:75 to 99:1. The decorative film according to any one of claims 1 to 3, wherein the hindered amine-based light stabilizer is at least one selected from the group consisting of N- _CH3 type, NO-alkyl type, and N-acyl type. The decorative film according to any one of claims 1 to 4, characterized in that the UV absorbent is a benzotriazole-based UV absorbent and/or a benzophenone-based UV absorbent. The decorative film according to any one of claims 1 to 5 , which is used on a transparent substrate. The decorative film according to claim 6 , wherein the transparent substrate is glass. 8. The decorative film according to claim 6 , which is used as an inner lining for the transparent substrate. The decorative film according to any one of claims 1 to 8 , characterized in that the weight average molecular weight of the acrylic adhesive is 1.3 million to 1.8 million. The decorative film according to any one of claims 1 to 9 , characterized in that the total content of the hindered amine-based light stabilizer and the ultraviolet absorbing agent is 2 parts by weight or more and 8 parts by weight or less per 100 parts by weight of the acrylic adhesive. The decorative film according to any one of claims 1 to 10 , wherein the pressure-sensitive adhesive composition contains an epoxy-based curing agent.

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