JP7829066B2 - resin film - Google Patents

Description

This disclosure relates to resin films.

Conventionally, films have been applied to the surface of an object for decoration and protection. For example, Patent Document 1 discloses a resin composition for printing films containing, per 100 parts by mass of a vinyl chloride resin, (A) 0.001 to 1 part by mass of at least one benzotriazole compound represented by general formula (I) and/or (a-2) at least one salicylate amide compound represented by general formula (II), (B) 0.001 to 1 part by mass of a β-diketone compound, and (C) 0.001 to 1 part by mass of a phenolic antioxidant.

Japanese Patent Publication No. 2012-219244

Resin films can discolor when heated, and therefore require discoloration resistance to withstand high-temperature environments. Furthermore, some components of the resin film may volatilize in high-temperature environments. For example, if these volatilized substances adhere to glass, the cooled volatilized substances can cause fogging, which is the phenomenon known as clouding.

This invention has been made in view of the above-mentioned circumstances, and aims to provide a resin film that is resistant to discoloration even when left in a high-temperature environment for a long period of time, and in which the occurrence of fogging is suppressed.

(1) One embodiment of the present invention is a resin film comprising a thermoplastic resin, a polyester-based plasticizer, a β-diketone having an aromatic ring, and an ultraviolet absorber.

(2) In one embodiment of the present invention, in addition to the configuration of (1) above, the polyester plasticizer comprises an aliphatic ester compound or an alicyclic ester compound in the resin film.

(3) One embodiment of the present invention is a resin film in which, in addition to the configuration of (1) or (2) above, the polyester plasticizer comprises an adipic acid-based polyester compound.

(4) One embodiment of the present invention is a resin film in which, in addition to any of the configurations of (1) to (3) above, the number average molecular weight of the polyester plasticizer is 500 or more and 4000 or less.

(5) One embodiment of the present invention is a resin film in which, in addition to any of the configurations of (1) to (4) above, the number average molecular weight of the polyester plasticizer is 1600 or more and 3000 or less.

(6) One embodiment of the present invention is a resin film in which, in addition to any of the configurations of (1) to (5) above, the β-diketone having the aromatic ring contains an alkyl group having 7 or more carbon atoms.

(7) One embodiment of the present invention is a resin film in which, in addition to any of the configurations of (1) to (6) above, the β-diketone having the aromatic ring is stearoylbenzoylmethane.

(8) One embodiment of the present invention is a resin film comprising any of the configurations of (1) to (7) above, further comprising an epoxy compound.

(9) One embodiment of the present invention is a resin film in which, in addition to any of the configurations of (1) to (8) above, the thermoplastic resin is polyvinyl chloride.

(10) One embodiment of the present invention is a resin film in which, in addition to any of the configurations of (1) to (9) above, the weight reduction rate of the resin film after heating at 95°C for 24 hours relative to the weight of the resin film before heating is 1.5% or less.

(11) One embodiment of the present invention is a resin film in which, in addition to any of the above configurations (1) to (10), the resin film is an automotive decorative film.

According to the present invention, it is possible to provide a resin film that is less prone to discoloration even when left in a high-temperature environment for a long period of time, and in which the occurrence of fogging is suppressed.

Embodiments of the present invention will be described below. The present invention is not limited to the contents described in the following embodiments, and it is possible to make appropriate design changes within the scope of satisfying the configuration of the present invention.

The resin film according to this embodiment comprises a thermoplastic resin, a polyester-based plasticizer, a β-diketone having an aromatic ring, and an ultraviolet absorber. The resin film according to this embodiment has heat resistance to discoloration (hereinafter also referred to as heat discoloration resistance) and a low weight loss rate due to heating. A low weight loss rate of the resin film due to heating means that the volatilization of resin film components due to heating is suppressed, and thus the occurrence of fogging can be suppressed. The inventors have found that by including a β-diketone having an aromatic ring and an ultraviolet absorber, discoloration in high-temperature environments can be effectively suppressed. Furthermore, the inventors have conducted various studies on the cause of the weight loss due to heating and have found that it is caused by the volatilization of the plasticizer contained in the resin film, and that by using a polyester-based plasticizer, the weight loss of the resin film due to heating can be suppressed. Note that fogging can also be evaluated by methods in accordance with DIN 752901-A and B of the German Institute for Standardization (DIN).

Examples of the thermoplastic resins mentioned above include polyvinyl chloride, polyethylene resins, polypropylene resins, and acrylonitrile-butadiene-styrene copolymer (ABS resin). Among these, polyvinyl chloride is preferred as the thermoplastic resin because it has high transparency, good elongation, conforms to the surface shape of the adherend, and is resistant to breakage. The polyvinyl chloride content of the resin film relative to the total resin components is preferably 50% by mass or more, and more preferably 90% by mass or more.

Examples of the polyvinyl chloride mentioned above include a homopolymer of vinyl chloride and a copolymer of vinyl chloride with other monomers copolymerizable with vinyl chloride. Examples of the other copolymerizable monomers include vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene, and styrene; alkyl esters of (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, and methyl (meth)acrylate; diesters of maleic acid such as dibutyl maleate and diethyl maleate; diesters of fumaric acid such as dibutyl fumarate and diethyl fumarate; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinylidene chloride and vinyl bromide; and vinyl ethers such as methyl vinyl ether and ethyl vinyl ether. These may be used individually or in combination of two or more. In this specification, "(meth)acrylic acid" refers to "at least one of acrylic acid and methacrylic acid."

The content of the other copolymerizable monomers in the above copolymer is usually 50% by mass or less, preferably 10% by mass or less. Among the polyvinyl chlorides, a homopolymer of vinyl chloride is preferred due to its excellent dimensional stability.

The average degree of polymerization of the polyvinyl chloride is preferably 800 to 1300. In this invention, the average degree of polymerization of polyvinyl chloride refers to the average degree of polymerization measured in accordance with JIS K 6721:1977 "Test Method for Vinyl Chloride Resins". If the average degree of polymerization exceeds 1300, the elongation of the polyvinyl chloride film may be insufficient. From the viewpoint of obtaining a highly transparent polyvinyl chloride film, an average degree of polymerization of 1100 or less is more preferable.

The resin film according to this embodiment contains a polyester-based plasticizer. Compared to phthalate-based plasticizers, polyester-based plasticizers have a higher molecular weight and are less susceptible to thermal decomposition. Therefore, they are less volatile than phthalate-based plasticizers in high-temperature environments, which reduces the weight loss rate of the resin film and suppresses the occurrence of fogging. Furthermore, polyester-based plasticizers have superior water absorption whitening resistance and heat resistance compared to trimellitic acid-based plasticizers.

As the above polyester-based plasticizer, plasticizers containing aliphatic ester compounds and alicyclic ester compounds are preferred. As the above aliphatic ester compound (acyclic aliphatic ester), plasticizers containing adipic acid-based polyester compounds such as adipic acid esters and polyesters in which adipic acid and polyalcohol are bonded are suitably used. Specific examples of aliphatic ester compounds include ADEKA's ADEKA Sizer (registered trademark) PN-7535, PN-7230, PN-7160, PN-9302, and Shin Nippon Rika Co., Ltd.'s Green Sizer BZ-100. As the above alicyclic ester compound, for example, cyclohexane-based carboxylic acid esters are suitably used. Specific examples of alicyclic ester compounds include BASF's HEXAMOLL (registered trademark) DINCH. HEXAMOLL DINCH is a plasticizer containing di-isononyl-cyclohexane-dicarboxylate. These may be used individually or in combination of two or more. In particular, the polyester-based plasticizer is more preferably one that contains an aliphatic ester compound, as this makes it less likely to cause water absorption and whitening.

If the number-average molecular weight of the plasticizer is small, when an adhesive layer is laminated onto the resin film, the plasticizer is more likely to migrate to the adhesive layer, which can lead to a decrease in adhesive strength when the resin film is stored for a long period of time. From the viewpoint of suppressing shrinkage of the resin film, it is preferable that the number-average molecular weight of the plasticizer be large, for example, 500 or more is preferable, 1000 or more is more preferable, and 2000 or more is even preferable. The upper limit of the number-average molecular weight of the plasticizer may be, for example, 4000. If the number-average molecular weight of the plasticizer exceeds 4000, the polyvinyl chloride film may become hard, making it difficult to mold it along the shape of the substrate during molding.

The number-average molecular weight of the above polyester-based plasticizer is preferably 500 or more and 4000 or less, and more preferably 1600 or more and 3000 or less.

The number-average molecular weight Mn of the above plasticizer is measured by GPC (gel permeation chromatography). The measurement conditions are as follows:
Device name: HLC-8120 (manufactured by Tosoh Corporation)
Columns: G7000HXL 7.8mm ID x 30cm (1 piece), GMHXL 7.8mm ID x 30cm (2 pieces), G2500HXL 7.8mm ID x 30cm (1 piece) (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

The content of the plasticizer may be 5 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the thermoplastic resin. If the content is less than 5 parts by mass, discoloration due to heating may occur easily, and the resin film may become too hard. If the content exceeds 80 parts by mass, fogging may occur. A more preferable lower limit for the content is 10 parts by mass, a more preferable upper limit is 60 parts by mass, an even more preferable upper limit is 50 parts by mass, and an even more preferable upper limit is 30 parts by mass. In this specification, when the thermoplastic resin is polyvinyl chloride, "per 100 parts by mass of thermoplastic resin" which is the standard for the content of each component shall be read as "per 100 parts by mass of polyvinyl chloride."

The above polyester-based plasticizer preferably does not contain a plasticizer having a benzene ring. Examples of plasticizers having a benzene ring include phthalate-based plasticizers such as di-2-ethylhexyl phthalate (DOP), dibutyl phthalate, dinonyl phthalate, diisononyl phthalate (DINP), bis(2-ethylhexyl) terephthalate (DOTP), and trimellitic acid-based plasticizers. The content of the above plasticizer having a benzene ring is preferably less than 5 parts by mass per 100 parts by mass of thermoplastic resin, and it is more preferable that the above plasticizer having a benzene ring is not included.

The resin film according to this embodiment contains a β-diketone having an aromatic ring. Including the β-diketone suppresses discoloration due to heating. If the β-diketone is not included, the resin composition will become discolored during melt mixing. A β-diketone is a compound having two ketone groups linked by one carbon atom, and a β-diketone having an aromatic ring refers to one in which at least one of the two ketone groups has an aromatic ring.

In the above-mentioned β-diketone having an aromatic ring, it is preferable that either _R1 or _R2 ( _R1 and _R2 are the same or different and represent hydrocarbon groups) is an aromatic ring in the compound represented by the following chemical formula (1). Furthermore, in the above-mentioned β-diketone having an aromatic ring, it is more preferable that the other of _R1 and _R2 is an alkyl group in the compound represented by the following chemical formula (1). By using a β-diketone having an aromatic ring and an alkyl group, the heat discoloration resistance can be further improved compared to when using a β-diketone without an alkyl group.

The above-mentioned β-diketone having an aromatic ring is more preferably such that, as shown in the following chemical formula (2), in the compound represented by the above chemical formula (1), one of _R1 and _R2 is a benzyl group and the other is an alkyl group. That is, the above-mentioned β-diketone having an aromatic ring is more preferably an alkaloylbenzoylmethane. The above-mentioned alkaloylbenzoylmethane can improve the heat discoloration resistance of the resin film more than dibenzoylmethane in which both _R1 and _R2 are benzyl groups in the compound represented by the above chemical formula (1).

The above-mentioned β-diketone having an aromatic ring preferably contains an alkyl group having 7 or more carbon atoms. The presence of an alkyl group having 7 or more carbon atoms in the above-mentioned β-diketone having an aromatic ring improves compatibility with polyester plasticizers and allows for uniform dispersion when mixing resin composition materials. Therefore, discoloration in high-temperature environments caused by localized material distribution can be more effectively suppressed. The number of carbon atoms in the alkyl group is more preferably 10 or more, and even more preferably 16 or more. The upper limit of the number of carbon atoms in the alkyl group is, for example, 25.

The above-mentioned β-diketone having an aromatic ring is more preferably stearoylbenzoylmethane represented by the following chemical formula (3) (where R ₁ in the above chemical formula (2) represents an alkyl group with 17 carbon atoms).

The content of the β-diketone having the aromatic ring described above is preferably 0.01 parts by mass or more and 2.0 parts by mass or less, more preferably 0.1 parts by mass or more and 1.0 part by mass or less, and even more preferably 0.4 parts by mass or more and 0.8 parts by mass or less, per 100 parts by mass of thermoplastic resin.

The above resin film contains an ultraviolet absorber. By containing an ultraviolet absorber, the above resin film can suppress discoloration caused by heating. Furthermore, since the ultraviolet absorber has the effect of suppressing photodegradation of the resin components by absorbing ultraviolet rays that hit the surface of the resin film, discoloration caused by ultraviolet irradiation can also be suppressed.

Examples of UV absorbers include benzotriazole-based UV absorbers, benzophenone-based UV absorbers, and triazine-based UV absorbers. Examples of benzotriazole-based UV absorbers include ADEKA STAB LA-29, LA-24, LA-31RG, LA-32, and LA-36 manufactured by ADEKA Corporation. Examples of benzophenone-based UV absorbers include ADEKA STAB 1413 manufactured by ADEKA Corporation. Examples of triazine-based UV absorbers include ADEKA STAB LA-46 and LA-F70 manufactured by ADEKA Corporation, and Tinuvin 1600 manufactured by BASF Japan. In particular, since polyvinyl chloride is easily photodegraded, the above UV absorbers can be suitably used when the resin film is a polyvinyl chloride film. These may be used individually or in combination of two or more types.

The amount of the UV absorber is preferably 0.5 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of thermoplastic resin. If the amount is less than 0.5 parts by mass, discoloration due to heat may not be sufficiently suppressed. If the amount exceeds 3.0 parts by mass, the UV absorber may migrate to the surface of the resin film and bleed out. If bleed-out occurs, fogging may occur, which may reduce the transparency of the resin film. Also, if an adhesive layer is laminated to the resin film, the adhesive properties of the adhesive layer may decrease. The amount of the UV absorber is more preferably 1 part by mass or more, and more preferably 1.5 parts by mass or more.

The resin film may contain a hindered amine light stabilizer. A hindered amine light stabilizer is a compound that contains a hindered amine in its structure and suppresses the degradation of films, etc., by trapping radicals generated by light irradiation such as ultraviolet light. The above hindered amine light stabilizer may contain a compound having a structure in which a hydrogen group, an alkyl group, or an alkoxyl group is bonded to the nitrogen atom of a piperidine ring. Furthermore, it is preferable that the above hindered amine light stabilizer contains a compound having a structure in which an alkoxyl group is bonded to the nitrogen atom of a piperidine ring. Examples of hindered amine light stabilizers include ADEKA STABU LA-52, LA-81, LA-77Y, LA-63P, LA-72 manufactured by ADEKA Corporation, and "Tinuvin 123" manufactured by BASF Japan.

The content of the above-mentioned hindered amine-based light stabilizer is, for example, 0.1 parts by mass or more and 2 parts by mass or less per 100 parts by mass of thermoplastic resin. If the content exceeds 2 parts by mass, there is a risk of bleed-out. A more preferable lower limit for the content of the above-mentioned hindered amine-based light stabilizer is 0.2 parts by mass, and a more preferable upper limit is 1 part by mass.

The above resin film preferably further contains an epoxy compound. By incorporating an epoxy compound into the resin film, the processability of the resin film (suppression of thermal degradation and decomposition under high-temperature conditions during film processing) can be improved. Examples of the epoxy compound include epoxidized soybean oil and epoxy group-containing acrylic resins. A specific example of epoxidized soybean oil is ADEKA Sizer O-130P manufactured by ADEKA Corporation. Specific examples of epoxy group-containing acrylic resins include Metabren (registered trademark) P-1901 manufactured by Mitsubishi Chemical Corporation and Marproof (registered trademark) G-0150M manufactured by NOF Corporation.

The content of the epoxy compound is preferably 0.5 parts by mass or more and 6 parts by mass or less, more preferably 1 part by mass or more and 4 parts by mass or less, and even more preferably 1 part by mass or more and 2 parts by mass or less, per 100 parts by mass of the thermoplastic resin.

The above resin film may further contain stabilizers. Halogen-containing resins such as polyvinyl chloride are prone to thermal decomposition due to dehalogenation during melt mixing and film formation; therefore, heat stabilizers are sometimes added to suppress deterioration during the processing steps. Additives that suppress deterioration and decomposition during the mixing of resin compositions or film formation are also called stabilizers, and additives that specifically suppress thermal decomposition are also called heat stabilizers. By suppressing thermal decomposition during the processing steps, discoloration can be suppressed.

Examples of the above-mentioned heat stabilizers include those containing phosphite esters, Ba-Zn-based heat stabilizers, hydrotalcite, and zinc stearate. These heat stabilizers may be used individually or in combination of two or more types.

The above resin film may contain antioxidants, plate-out inhibitors, etc., as needed.

The content of the above-mentioned heat stabilizer is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 2 parts by mass or more and 7 parts by mass or less, per 100 parts by mass of thermoplastic resin. It is even more preferably 3 parts by mass or more and 4 parts by mass or less.

The thickness of the resin film is, for example, 50 μm or more and 300 μm or less. If the thickness is less than 50 μm, the strength may be insufficient and sufficient durability may not be obtained. If the thickness exceeds 300 μm, it may become too stiff and difficult to adhere to the substrate. The preferred lower limit of the thickness is 60 μm, and the preferred upper limit is 160 μm.

In the embodiment, the weight loss rate of the resin film after heating at 95°C for 24 hours relative to the weight of the resin film before heating is preferably 1.5% or less. If the weight loss rate of the resin film exceeds 1.5%, there will be a large amount of volatile matter in the high-temperature environment, making fogging more likely. The weight loss rate of the resin film is more preferably 1.2% or less, even more preferably 1.0% or less, and particularly preferably 0.8%.

Specifically, the weight loss rate of the above resin film is calculated by preparing a test piece by cutting the resin film into a 10 cm x 10 cm section, placing the test piece in a constant temperature oven (forced-air oven) (manufactured by Kusumoto Kasei Co., Ltd., ETAC HS260) set to 95°C, removing it after 24 hours, and calculating the weight loss rate (%) using the following formula.
Weight loss = Weight before heating (g) - Weight after heating (g)
Weight loss rate (%) = (Amount of weight loss / Weight before heating) × 100

The resin film according to this embodiment is a resin film in which discoloration due to heat is suppressed. The resin film according to this embodiment preferably has a degree of discoloration ΔE of 4.5 or less, more preferably 3.0 or less, and even more preferably 1.5 or less after heating at 95°C for 500 hours. If the degree of discoloration ΔE after heating at 95°C for 500 hours exceeds 4.5, it can be determined that the heat resistance to discoloration is significantly poor.

The above discoloration degree ΔE can be measured by the following method. First, measure L*, a*, and b* in the L*a*b* color system of the resin film before heating. A colorimeter (SE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) can be used to measure L*, a*, and b*. Then, place the resin film in a constant temperature oven (blow-air oven) (ETAC HS260, manufactured by Kusumoto Kasei Co., Ltd.) set to 95°C and measure L*, a*, and b* after 500 hours. Define ΔL* as the value obtained by subtracting L* before heating from L* after heating, Δa* as the value obtained by subtracting a* before heating from a* after heating, and Δb* as the value obtained by subtracting b* before heating from b* after heating. ΔE is calculated by taking the square root of the sum of the squares of ΔL*, Δa*, and Δb* (see formula below).

One method for manufacturing a resin film is to mix (melt-knead) the materials while heating them using a Banbury mixer or the like to obtain a resin composition, and then to form a film using the resin composition. While conventionally known molding methods such as calendering, extrusion, and injection molding can be used for this film formation, calendering is preferred because it allows for the production of thin films with excellent thickness accuracy.

A laminated film obtained by laminating a resin film according to this embodiment with other layers is also one embodiment of the present invention. Examples of other layers include an adhesive layer, a design layer, a primer layer, and the like.

The adhesive layer described above is not particularly limited as long as it has adhesive properties (pressure-sensitive adhesion), and examples include those containing adhesives such as acrylic adhesives, rubber adhesives, and silicone adhesives. Among these, acrylic adhesives are preferably used because they have excellent transparency, tackiness, processability, heat aging resistance, and weather resistance, and are relatively inexpensive. The thickness of the adhesive layer is not particularly limited, but is preferably 10 to 60 μm, and more preferably 20 to 50 μm.

When the adhesive layer is laminated onto the resin film, the design layer may be positioned on the opposite side of the resin film from the adhesive layer.

The above design layer may be a printed layer, and can be applied by, for example, inkjet printing, gravure printing, screen printing, rotary screen printing, flexographic printing, offset printing, electrostatic printing, etc. Alternatively, a colored film or the like may be attached.

The laminated film described above can be used by attaching it to a substrate. The resin film according to this embodiment is preferably a decorative film that imparts a design to the substrate. Examples of the substrate material include resins such as polycarbonate resins, acrylic resins, and styrene resins; acrylonitrile-butadiene-styrene copolymers (ABS resins); metals such as iron, copper, and aluminum; and alloys. Examples of the substrate include decorative panels (wall coverings), interior doors, closet and kitchen doors, furniture, flooring and other interior materials, and interior materials for vehicles such as cars. Examples of interior materials for vehicles such as cars include instrument panels and drink holders. The interior of a car tends to become hot in the summer and is a narrow, enclosed space, making it an environment where fogging is likely to occur. When the car windows fog up due to fogging, the user's view is obstructed, which may impair driving. The resin film according to this embodiment has excellent heat discoloration resistance and fogging resistance, making it suitable for use as an automotive decorative film for interior materials of vehicles such as cars.

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

The components other than β-diketone used in the following examples and comparative examples are shown in Table 1 below.

(Example 1)
Each component was added to 100 parts by mass of polyvinyl chloride in the proportions shown in Table 2 below to obtain a polyvinyl chloride resin composition. In Example 1, stearoylbenzoylmethane was used as the β-diketone. The obtained polyvinyl chloride resin composition was melt-kneaded at 180°C for 10 minutes using a twin-screw roller, and then calendered to form a sheet to produce the polyvinyl chloride film of Example 1.

(Examples 2-7, Comparative Example 1)
As shown in Table 2, polyvinyl chloride films for Examples 2-7 and Comparative Example 1 were prepared in the same manner as in Example 1, except that the composition of each component was changed.

<Evaluation of heat resistance and discoloration>
For each example and comparative example, three test pieces were prepared by cutting PVC film (thickness 90 μm) into 10 cm x 10 cm sections, and the L*, a*, and b* values in the L*a*b* color system were measured for each test piece. A colorimeter (SE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used as the measuring device. For each example and comparative example, the average values of L*, a*, and b* measured in the three test pieces were taken as the L*, a*, and b* values before heating (0 hours) for each example and comparative example.

Each test specimen was placed in a constant temperature oven (forced-air oven) (manufactured by Kusumoto Kasei Co., Ltd., ETAC HS260) set to 95°C, and L*, a*, and b* were measured after 100 hours, 200 hours, 300 hours, 400 hours, and 500 hours. For each example and comparative example, the average values of L*, a*, and b* measured from three test specimens were used as the L*, a*, and b* values at each elapsed time for each example and comparative example. The values obtained by subtracting the L*, a*, and b* (average values) before heating (0 hours) from the L*, a*, and b* (average values) after the predetermined time for each example and comparative example were expressed as ΔL*, Δa*, and Δb*, respectively. Furthermore, ΔE was calculated from ΔL*, Δa*, and Δb* using the following formula. The results are shown in Tables 3 and 4 below. If the above ΔE after 500 hours is 1.5 or less, it can be judged that the heat discoloration resistance is very good. On the other hand, if the above ΔE exceeds 4.5, it can be determined that the heat resistance to discoloration is significantly poor.

<Measurement of weight loss rate due to heating>
For each example and comparative example, a test piece was prepared by cutting a PVC film (thickness 90 μm) to 10 cm x 10 cm, and the weight of each test piece was measured (weight before heating). Each test piece was placed in a constant temperature oven (forced-air oven) (manufactured by Kusumoto Kasei Co., Ltd., ETAC HS260) set to 95°C, removed after 24 hours, and the weight of each test piece was measured (weight after heating). The weight loss rate (%) for each example and comparative example was calculated using the following formula, and the results are shown in Table 5 below.
Weight loss = Weight before heating (g) - Weight after heating (g)
Weight loss rate (%) = (Amount of weight loss / Weight before heating) × 100

The smaller the above weight reduction rate, the less volatile matter is judged to be released in high-temperature environments, and if the above weight reduction rate is 1.5% or less, the fogging that is a concern with automotive decorative films can be reduced.

The formulations shown in Table 2, the ΔE results after 500 hours, and the weight loss rate due to heating are summarized in Table 6 below.

Table 6 shows that Examples 1 to 7, which used polyester-based plasticizers, exhibited low weight loss after heating, indicating suppressed plasticizer volatilization. On the other hand, Comparative Example 1, which used phthalate-based plasticizers, showed a weight loss of over 1.5% after heating, indicating that plasticizer volatilization was more likely to occur.

Claims (11)

A resin film comprising polyvinyl chloride, a polyester-based plasticizer, a β-diketone having an aromatic ring, and an ultraviolet absorber,
The content of the polyester-based plasticizer is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the polyvinyl chloride.
The aforementioned ultraviolet absorber does not include any β-diketone having an aromatic ring.
The aforementioned resin film is a resin film that satisfies at least one of the following (1), (2), and (3) .
(1) The resin film further comprises an epoxy compound.
(2) The weight reduction rate of the resin film after heating at 95°C for 24 hours relative to the weight of the resin film before heating is 1.5% or less.
(3) The resin film is an automotive decorative film. The resin film according to claim 1, wherein the content of the ultraviolet absorber is 0.5 parts by mass or more per 100 parts by mass of the polyvinyl chloride. The resin film according to claim 1, wherein the ultraviolet absorber comprises at least one selected from the group consisting of benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and triazine-based ultraviolet absorbers. The resin film according to claim 1, wherein the UV absorber comprises a benzotriazole-based UV absorber. The resin film according to claim 1, wherein the content of the β-diketone having the aromatic ring is 0.4 parts by mass or more per 100 parts by mass of the polyvinyl chloride. The resin film according to claim 1, wherein the polyester-based plasticizer comprises an aliphatic ester compound or an alicyclic ester compound. The resin film according to claim 1, wherein the polyester-based plasticizer comprises an adipic acid-based polyester compound. The resin film according to claim 1, wherein the number-average molecular weight of the polyester-based plasticizer is 500 or more and 4000 or less. The resin film according to claim 1, wherein the number-average molecular weight of the polyester-based plasticizer is 1600 or more and 3000 or less. The resin film according to claim 1, wherein the β-diketone having the aromatic ring contains an alkyl group having 7 or more carbon atoms. The resin film according to claim 1, wherein the β-diketone having the aromatic ring is stearoylbenzoylmethane.