WO2019087017A1

WO2019087017A1 - Decorative film for hot stretch molding

Info

Publication number: WO2019087017A1
Application number: PCT/IB2018/058311
Authority: WO
Inventors: Tomotaka ARAKI
Original assignee: 3M Innovative Properties Company
Priority date: 2017-10-31
Filing date: 2018-10-24
Publication date: 2019-05-09
Also published as: JP2019081327A; EP3703942A1; CN111315568A

Abstract

A decorative film for hot stretch molding 1 including: a base film 12, a bonding layer 14, a metal layer 16, and a film protective layer 18 in this order, the bonding layer 14 containing a reaction product of a composition containing a polyurethane polyol, a polyisocyanate, and a silane coupling agent.

Description

DECORATIVE FILM FOR HOT STRETCH MOLDING

TECHNICAL FIELD

The present invention relates to a decorative film for hot stretch molding.

BACKGROUND ART

A decorative film having a multilayer structure including a metal layer on a surface of a resin has been used to, for example, to impart a metallic design to interior and exterior components of vehicles, interior materials for building materials, household electric appliances, and the like . JP 2010-126706 A discloses a metallic decorative film including a metal holding film layer in which a metal thin film is formed on a surface of a film layer formed from a resin composition and a thermoplastic resin.

SUMMARY OF THE INVENTION

For exterior components of vehicles and the like, specifications such as weather resistance are required. Especially, in recent years, exterior components of vehicles have more complex surface shape to enhance design. In decorating a surface of such a component with a decorative film, insert molding is expected. In insert molding, the decorative film needs to be highly stretched to conform to the surface shape while the decorative film is being heated; however, a conventional metallic decorative film fails to withstand such molding (hot stretch molding). When a conventional decorative film is forcibly used in the hot stretch molding, the film is delaminated.

The first aspect of the present invention is a decorative film for hot stretch molding including: a base film, a bonding layer, a metal layer, and a film protective layer in this order, the bonding layer containing a reaction product of a composition containing a polyurethane polyol, a polyisocyanate, and a silane coupling agent.

This decorative film for hot stretch molding has significantly excellent adhesive properties between layers, and even during hot stretch molding (even in a case where the decorative film is highly stretched during adhering), delamination that causes practical problems does not occur. The metal layer is typically formed by performing vapor deposition on a film protective layer. In this case, the thickness of the metal layer is relatively small, and problems are less likely to occur in the adhesive strength between the film protective layer and the metal layer. However, the metal layer and a base film are often adhered by using a bonding agent (bonding layer), delamination tends to occur in the interface between the metal layer and the bonding layer and in the interface between the bonding layer and the base film. Furthermore, depending on the type of the bonding layer, the bonding layer itself undergoes a cohesive failure, resulting in delamination. On the other hand, in the decorative film for hot stretch molding of the first aspect, the metal layer and the base film are firmly adhered by the bonding layer, and these layers conform together to a large deformation (high stretch) in a heated condition. As a result, delamination in the interface is less likely to occur, and cohesive failures in the bonding layer are also prevented.

The equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol may be 5 or greater, and the content of the silane coupling agent may be from 2 parts by mass to 12 parts by mass per 100 parts by mass of the polyurethane polyol.

These compositions provide even better adhesive properties between the metal layer and the bonding layer when the decorative film is highly stretched are achieved, and excellent water resistance of the decorative film.

The equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol may be from 5 to 9, and the content of the silane coupling agent may be from 2 parts by mass to 12 parts by mass per 100 parts by mass of the polyurethane polyol.

Thus, even better water resistance and adhesive properties between the metal layer and the bonding layer when the decorative film is highly stretched are achieved, and the metal layer is less likely to delaminate from the bonding layer even in a case where high-pressure washing is performed after the decorative film is adhered. Furthermore, even in a case where a force is applied to the decorative film in the lamination direction, the metal layer is less likely to delaminate from the bonding layer.

The equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol may be from 5 to 9, and the content of the silane coupling agent may be from 2 parts by mass to 9 parts by mass per 100 parts by mass of the polyurethane polyol.

Thus, a decorative film having excellent appearance can be obtained as well as excellent adhesive properties between the metal layer and the bonding layer when the decorative film is highly stretched, excellent water resistance, and excellent adhesive properties between the metal layer and the bonding layer during the high-pressure washing are achieved, and the delamination of the metal layer when a force is applied in the lamination direction is suppressed.

The decorative film for hot stretch molding described above may have at least one of the features (1), (2), and (3) described below. That is, (1) in a case where the decorative film is uniaxially stretched at a degree of stretching of 189% or greater and subjected to heating and cooling, adhesion between the metal layer and the bonding layer is maintained. (2) In a case where cuts are formed in a shape of a cross on the decorative film and the decorative film is subjected to high-pressure washing test, delamination occurred between the metal layer and the bonding layer is 2 mm or less. (3) 180° peeling strength at 25 °C between the metal layer and the bonding layer is 15 N/25 mm or greater.

The second aspect of the present invention provides a decorative film for hot stretch molding including: a base film, a bonding layer, a metal layer, and a film protective layer in this order, wherein, in a case where the decorative film is uniaxially stretched at a degree of stretching of 189% or greater and subjected to heating and cooling, adhesion between the metal layer and the bonding layer being maintained. The procedure and condition of the evaluation are explained in "cooling/heating cycle test" described below.

The decorative film for hot stretch molding can have characteristics where, in a case where cuts are formed in a shape of a cross on the decorative film and the decorative film is subjected to high-pressure washing test, delamination occurred between the metal layer and the bonding layer is 2 mm or less and/or 180° peeling strength at 25°C between the metal layer and the bonding layer is 15 N/25 mm or greater. The procedure and condition of the evaluation are explained in "high-pressure washing test" described below.

According to the present invention, a decorative film for hot stretch molding having excellent adhesive properties between layers can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating an embodiment of the decorative film for hot stretch molding.

DESCRIPTION OF PREFERRED EMBODIMENTS

Detailed descriptions of the embodiments according to the present invention are given below with reference to the drawings. In the descriptions, the same reference symbols have been assigned to elements that are the same, and redundant descriptions thereof have been omitted. Furthermore, dimension ratio of each drawing is not necessarily identical with the actual dimension ratio.

FIG. 1 is a schematic cross-sectional view illustrating an embodiment of the decorative film for hot stretch molding. The decorative film for hot stretch molding 1 illustrated in FIG. 1 (hereinafter, also simply referred to as "decorative film 1") includes: a base film 12, a bonding layer 14, a metal layer 16, and a film protective layer 18 in this order. The thickness of the entire decorative film 1 may be from 200 to 1000 um.

The base film 12 has a function to support the sheet-like shape of the decorative film 1. The base film 12 is formed from, for example, a resin, and the resin that forms the base film 12 may be a thermoplastic resin. The resin may be a polyolefin resin such as polypropylene or polyethylene, an acrylonitrile-butadiene-styrene resin (ABS resin), an acrylonitrile-styrene-acrylate resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, polyethylene terephthalate (PET), acrylonitrile- ethylene-styrene resin (AES resin), or the like. One type of these resins may be used alone, or a mixture (as a blend or a copolymer) of two or more types of these resins may be used. The thickness of the base film 12 may be from 200 to 1000 μπι.

The metal layer 16 imparts metallic appearance when the decorative film 1 is adhered to a target object, such as an exterior component of a vehicle. The metal used in the metal layer 16 may be at least one type selected from the group consisting of indium, tin, chromium, aluminum, and silver, and is preferably indium from the perspectives of stretchability and corrosion resistance. The metal layer 16 is preferably formed by a vapor deposition method, such as a vacuum deposition method, a sputtering method, and an ion plating method. In this case, it is preferable to perform the vapor deposition for the film protective layer 18 and then laminate the film protective layer 18 and the base film 12 through the bonding layer 14. The thickness of the metal layer 16 may be approximately 1 μπι or less.

The film protective layer 18 protects the surface of the decorative film 1, especially the surface of the metal layer 16 side. The film protective layer 18 is preferably formed from a transparent material such that the metallic appearance of the metal layer 16 can be clearly and visually recognized. The film protective layer 18 may be formed from a resin and, for example, may be formed from at least one type selected from the group consisting of polyurethane resins, polyester resins, polyamide resins, polyimide resins, acrylic resins, epoxy resins, fluororesins, and silicone resins. The film protective layer 18 is preferably a polyurethane resin layer to further enhance stretchability, weather resistance, scratch resistance, and cost.

In a case where the film protective layer 18 contains a polyurethane resin, a curing agent may be used together with the polyurethane resin. The curing agent may be a carbodiimide-based compound, a melamine compound, an isocyanate-based compound, an oxazoline compound, an epoxy compound, or the like. The content of the curing agent may be from 0.1 equivalents to 2 equivalents relative to the functional group of the polyurethane resin.

The film protective layer 18 may further contain additives, such as thickeners, photostabilizers, UV absorbents, surface conditioners, thermal stabilizers, pigments, and catalysts, as other raw materials. The thickness of the film protective layer 18 may be from 5 to 100 μπι.

The bonding layer 14 is arranged in between the metal layer 16 and the base film 12 and has a function to adhere the metal layer 16 and the base film 12 each other. In an embodiment, the bonding layer 14 contains a reaction product of a composition (hereinafter, also referred to as

"adhesive composition") containing a polyurethane polyol, a polyisocyanate, and a coupling agent.

The polyurethane polyol is a compound having two or more hydroxy groups (OH groups) at terminals and, for example, can be obtained by allowing polyol and polyisocyanate to react. Examples of the polyol include aliphatic polyols, polyester polyols, polyether polyols, polycarbonate polyols, polyolefin polyols, polyacryl polyols, dimer diols, and the like. The polyol is preferably a polyester polyol. A commercially available polyurethane polyol may be used as the polyurethane polyol. For example, NIPPOLAN 3124, which is a polyester-based one-component solvent/dry solid type urethane (available from Tosoh Corporation), and the like can be used.

The polyisocyanate to be reacted with the polyurethane polyol is a compound having two or more isocyanate groups (NCO groups). The polyisocyanate may be any polyisocyanate selected from aromatic polyisocyanates, aliphatic polyisocyanate s, alicyclic polyisocyanates, and the like. The polyisocyanate may be an adduct of a polyisocyanate and a polyol and, for example, may be an adduct of tolylene diisocyanate and trimethylolpropane. As such an adduct, for example, a commercially available L45 (available from Soken Chemical & Engineering Co., Ltd.) can be used.

In the adhesive composition, the equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol (NCO groups/OH groups) is preferably 5 or greater, more preferably 8 or greater, and even more preferably 10 or greater.

Thus, viscoelasticity of the bonding layer 14 can be further enhanced, and thus the metal layer 16 is less likely to delaminate from the bonding layer 14. The equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol may be 22 or less.

One characteristic of the adhesive composition is that the adhesive composition contains a coupling agent. The coupling agent may be used in combination with the polyurethane polyol and the polyisocyanate. Thus, the bonding layer 14 may exhibit excellent adhesive strength and, furthermore, significant resistance to hot stretch molding. That is, even in a case where a force to induce a large deformation (large stretch) is applied under a heated condition by the hot stretch molding, excellent effect of exhibiting a greater conformability to deformation was observed. The coupling agent may be at least one type selected from the group consisting of silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, zirconate-based coupling agents, and zircoaluminate-based coupling agents, and is preferably a silane coupling agent to further enhance the adhesive properties between the metal layer 16 and the bonding layer 14.

The silane coupling agent may be a functional silane coupling agent having a functional group or may be a silane coupling agent having no functional group. The silane coupling agent is preferably a functional silane coupling agent and, specifically, may be an epoxy functional silane coupling agent, such as 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4- epoxycyclohexyl)ethyltrimethoxysilane, 5,6-epoxyhexyltriethoxysilane, 3- glycidoxypropyltriethoxysilane, and 3-glycidoxypropyltrimethoxysilane; a mercapto functional silane coupling agent, such as 3-mercaptopropyltrimethoxysilane and 3- mercaptopropyltriethoxysilane; an amino functional silane coupling agent, such as N- methylaminopropyltrimethoxysilane, 4-aminobutyltriethoxysilane, N-(2-aminoethyl)-3- aminopropyl-trimethoxysilane, (aminoethylaminomethyl)p-phenethyltrimethoxysilane, N-(2- aminoethyl)-3-aminopropyltriethoxysilane; an ureide functional silane coupling agent; an isocyanate functional silane coupling agent; an isocyanurate functional silane coupling agent; and the like. One type of the silane coupling agent may be used, or a mixture of two or more types of the silane coupling agents may be used.

The content of the silane coupling agent in the adhesive composition is preferably 2 parts by mass or greater, more preferably 4 parts by mass or greater, and even more preferably 8 parts by mass or greater, per 100 parts by mass of the polyurethane polyol. Thus, adhesive properties between the metal layer 16 and the adhesive properties 14 can be further enhanced, and the metal layer 16 is less likely to delaminate from the bonding layer 14 even in a case where the decorative film 1 is highly stretched. The content of the silane coupling agent may be 35 parts by mass or less per 100 parts by mass of the polyurethane polyol. Thus, excellent appearance can be achieved while the surface of the decorative film 1 is not whitened and no crack-like line appears.

In the bonding layer 14, physical properties of the decorative film 1 can be further enhanced by allowing an adhesive composition, in which the contents of the polyurethane polyol, the polyisocyanate, and the silane coupling agent described above are adjusted to the prescribed amounts described below, to react.

The equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol is preferably 5 or greater, and the content of the silane coupling agent is preferably from 2 parts by mass to 12 parts by mass per 100 parts by mass of the polyurethane polyol. Thus, in a case where the decorative film 1 is highly stretched in a horizontal direction, the adhesive properties between the metal layer 16 and the bonding layer 14 is easily maintained, and delamination of the metal layer 16 from the bonding layer 14 can be suppressed. Furthermore, in a case where the highly stretched decorative film 1 is heated or cooled, the adhesive properties between the metal layer 16 and the bonding layer 14 is likely to be maintained. Furthermore, water resistance of the decorative film 1 can be also enhanced.

The equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol is more preferably from 5 to 9, and the content of the silane coupling agent is more preferably from 2 parts by mass to 12 parts by mass per 100 parts by mass of the polyurethane polyol. Thus, in addition to the effects described above, even in a case where a force is applied between the metal layer 16 and the bonding layer 14 in a perpendicular direction when these layers are seen from a lamination direction, the adhesive properties between the metal layer 16 and the bonding layer 14 is likely to be maintained, and delamination of the metal layer 16 from the bonding layer 14 can be suppressed. In addition, even in a case where a component to which the decorative film 1 is adhered is subjected to high-pressure washing, the adhesive properties between the metal layer 16 and the bonding layer 14 is likely to be maintained, and the metal layer 16 is less likely to delaminate from the bonding layer 14.

The equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol is more preferably from 5 to 9, and the content of the silane coupling agent is even more preferably from 2 parts by mass to 9 parts by mass per 100 parts by mass of the polyurethane polyol. Thus, in addition to the effects described above, a decorative film 1 having superior appearance can be obtained.

The adhesive composition constituting the bonding layer 14 may further contain a thickener, a surface conditioner, a thermal stabilizer, a catalyst, or the like as another raw material.

For example, the decorative film 1 can be obtained by adhering, by thermocompression bonding, a material formed by coating a solution containing raw materials of the adhesive composition on a main surface of a base film 12 and then hot-air drying the coating to form a bonding layer 14, and a material formed by vapor deposition of a metal layer 16 on a film protective layer 18. At this time, the bonding layer 14 and the metal layer 16 are bonded to each other.

The decorative film 1 obtained as described above is particularly suitably used for hot stretch molding and can be particularly suitably used for decoration of exterior components of vehicles and the like. The hot stretch molding is, for example, a method in which a heated decorative film is highly stretched and molded, to mold the decorative film in a manner that the decorative film conforms to a mold, during production of an exterior component of a vehicle to which a decorative film is adhered by insert molding. The hot stretch molding includes molding methods, such as vacuum molding, air- pressure molding, press molding, and blow molding. In particular, vacuum molding and air-pressure molding are used for stretching of a decorative film in insert molding, and these are collectively called vacuum/air-pressure molding. Note that hot stretch molding does not include coextrusion molding and injection molding.

In the decorative film 1, the adhesion between the bonding layer and the metal layer is maintained even in a case where the decorative film is uniaxially stretched and subjected to heating and cooling. This function can be confirmed by, for example, the following test (details are described below). First, the decorative film 1 is stretched to a prescribed degree of stretching. On the stretched decorative film 1, a slit is formed by using a utility knife or the like such that the slit reaches to the base film 12 from the film protective layer 18 side. Then the stretched decorative film 1 is kept being heated (e.g. 80°C for 240 minutes) and kept being cooled (e.g. - 40°C for 240 minutes), and this cycle is repeated for approximately 10 times.

In the decorative film 1 of the present embodiment, the maximum degree of stretching that does not cause delamination of the metal layer 16 from the bonding layer 14 during this test is preferably 189% (indicating that the decorative film is stretched by 89% compared to prior to the test) or greater, and more preferably 195% or greater. Thus, the decorative film 1 can have excellent adhesive properties even in the condition where the decorative film 1 is hot stretched upon adhesion and, furthermore, can have excellent adhesive properties between the metal layer 16 and the bonding layer 14 even in a case where the decorative film 1 is exposed to the condition where heating and cooling are repeated after adhesion.

Furthermore, the decorative film 1 maintains the adhesion between the metal layer 16 and the bonding layer 14 even in a case where the decorative film 1 is subjected to high-pressure washing. This function can be confirmed by the following test (details are described below). First, on the decorative film 1, two slits are formed by using a utility knife or the like in a shape of a cross such that the slits reach to the base film 12 from the film protective layer 18 side (hereinafter, these slits are referred to as "cross-cut"). To the portion where the cross-cut has been formed, for example, high-pressure washing is performed by injecting water using the following conditions: injection temperature: 70°C; injection rate: 10.5 L/min; and injection pressure: from 8 to 10 MPa. After the high-pressure washing, the portion where the cross-cut has been formed is examined for delamination of the metal layer 16 from the bonding layer 14.

When this test is performed, the delamination of the portion where the cross-cut has been formed in the decorative film 1 of the present embodiment is preferably 2 mm or less, more preferably 1 mm or less, and even more preferably 0.4 mm or less. Thus, the decorative film 1 can have excellent adhesive properties between the metal layer 16 and the bonding layer 14 even in a case where the decorative film 1 is subjected to high-pressure washing after adhesion.

Furthermore, even in a case where a peeling force is applied to the decorative film 1 in the lamination direction, the metal layer 16 is less likely to delaminate from the bonding layer 14. This function can be confirmed by determining the peeling strength, i.e. 180° peeling strength performed according to the 180° peeling test (stipulated in JIS Z 0237). Conditions of the 180° peeling test include, for example, 25 mm width, the peeling rate of 300 mm/min, and the measurement temperature of 25°C.

In the decorative film 1 of the present embodiment, the 180° peeling strength is preferably 13 N/25 mm or greater, and more preferably 15 N/25 mm or greater, when the metal layer 16 is peeled off from the bonding layer 14 during the 180° peeling test. Thus, the decorative film 1 can have excellent adhesive properties between the metal layer 16 and the bonding layer 14 even in a case where a peeling force is applied in the lamination direction during and after the adhering of the decorative film 1.

Furthermore, even in a case where the decorative film 1 is immersed in water, the metal layer

16 is less likely to delaminate from the bonding layer 14. This function can be confirmed by the following test (details are described below). First, the decorative film 1 is heated to, for example, 120°C and then brought back to room temperature (e.g. 23°C). This decorative film 1 is immersed in water at 40°C, then, a slit is formed by using a utility knife or the like such that the slit reaches to the base film 12 from the film protective layer 18 side. At this time, the portion where the slit has been formed is examined for delamination of the metal layer 16 from the bonding layer 14.

In the decorative film 1 of the present embodiment, when this test is performed, the number of squares where the metal layer 16 delaminated from the bonding layer 14 is preferably 1 or less, and more preferably 0, per 100 squares. Thus, the water resistance of the decorative film 1 can be enhanced.

The decorative film 1 described above may have various modified examples. For example, another layer (primer layer or the like) may be provided between the base film 12 and the bonding layer 14, or another layer (gravure-printed layer or the like) may be provided between the metal layer 16 and the film protective layer 18. Furthermore, each layer may have a multilayer structure formed from a plurality of layers . EXAMPLES

The present invention will be described specifically below using examples, but the present invention is not intended to be limited to these examples.

Example 1

First, 100 parts by mass of polyester-based polyurethane polyol (NIPPOLAN 3124, available from Tosoh Corporation), 10 parts by mass of adduct of tolylene diisocyanate and trimethylpropane (L45, available from Soken Chemical & Engineering Co., Ltd.) as a

polyisocyanate, 1.07 parts by mass of 3-glycidoxypropyltrimethoxysilane (KBM-403, available from Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent, 40 parts by mass of ethyl acetate, and 0.02 parts by mass of dibutyltin dilaurate (DBTDL, available from Wako Pure Chemical Industries, Ltd.) were mixed to produce an adhesive solution. This adhesive solution was coated on a surface of the film that was formed from ABS resin and that had the thickness of 350 μιη as a base film, and hot-air dried to form a bonding layer having the thickness of 20 μιη on the base film. At this time, the equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol was 2.69.

Thereafter, 84.30 parts by mass of water-based polyurethane (UW 5002, available from Ube Industries, Ltd.), 7.54 parts by mass of carbodiimide-based waterborne curing agent (V-02, available from Nisshinbo Chemical Inc.), 0.81 parts by mass of urethane-based thickener (RM8W, available from Rohm & Haas), 0.51 parts by mass of surface conditioner (D604, available from Nissin Chemical Co., Ltd.), 5.28 parts by mass of ethanol (available from Kanto Chemical Co., Inc.), 0.58 parts by mass of hindered amine-based photostabilizer (Tinuvin 292, available from BASF Japan Ltd.), and 0.98 parts by mass of benzotriazole-based photostabilizer (Tinuvin 1130, available from BASF Japan Ltd.) were mixed to produce a solution. This solution was coated on a PET film having the thickness of 50 μιη and hot-air dried to form a film protective layer having the thickness of 30 um on the PET film. Thereafter, the face of the film protective layer opposite to the PET film was subjected to corona discharge treatment at the output of 2.5 kW and the treatment rate of 42 m/min. Thereafter, indium was vacuum-deposited on the surface of the film protective layer, and a metal layer having the thickness of 1 um or less was formed on the face of the film protective layer opposite to the PET film.

The laminate having the base film and the bonding layer, and the laminate having the PET film, the film protective layer, and the metal layer were subjected to thermocompression bonding at 50°C while the bonding layer and the metal layer are in contact, to form one laminate. By peeling off the PET film from the obtained laminate, a decorative film having the base film, the bonding layer, the metal layer, and the film protective layer in this order was produced.

Examples 2 to 24 and Comparative Examples 1 to 3

Decorative films were produced by the same method as in Example 1 except for modifying the equivalent ratio of the isocyanate groups of the polyisocyanate to the hydroxy groups of the polyurethane polyol (NCO groups/OH groups) and the content of the silane coupling agent per 100 parts by mass of the polyurethane polyol according to the description in Table 1 for the raw materials of the bonding layer.

Table 1

The stretchability of each of the decorative films of Examples and Comparative Examples was evaluated based on the following procedure and condition. The test with these procedure and condition is referred to as "cooling/heating cycle test". First, the decorative film was uniaxially stretched by a machine for the Three-dimensional Overlay Method (hereinafter, also referred to as "TOM"). That is, the decorative film and an article having a three-dimensional shape were prepared, and the decorative film and the article having the three-dimensional shape were placed in a vacuum chamber in an inner part of a heating device. At this time, the inner space of the vacuum chamber was separated into two by the decorative film, and the article was placed in one of the separated inner space. Thereafter, the decorative film was heated by the heating device, and the decorative film was brought into contact with the article while the atmosphere in the inner space where the article was placed was reduced, to apply the decorative film to the article. After the decorative film was uniaxially stretched by this method, a slit having the length of 2 cm was formed on the decorative film by using a utility knife. At this time, the slit was formed from the film protective layer side in a manner that the slit reached a part of the base film. The film on which the slit was formed was heated to 80°C and the relative humidity of 80% over 60 minutes, and this state was maintained for 240 minutes. Thereafter, the film was cooled to -40°C over 120 minutes. At this time, the air moisture was controlled so that the relative humidity is approximately 30%: however, the air moisture was not controlled in the temperature region lower than 0°C. Then, after the film was maintained in the condition at -40°C for 240 minutes, the film was heated to 23°C over 60 minutes. At this time, the air moisture was controlled so that the relative humidity at 0°C is 30%. When this heating-cooling cycle was repeated for 10 cycles, presence or absence of delamination of the metal layer 16 from the bonding layer 14 was examined. The maximum value of the degree of stretching of the decorative film in the case where the metal layer did not delaminate from the bonding layer is shown in Table 2.

The durability to high-pressure washing of each of the decorative films of Examples and

Comparative Examples was evaluated based on the following procedure and condition. The test with these procedure and condition is referred to as "high-pressure washing test". First, two slits having the length of 6 cm were formed on the decorative film in a shape of a cross and used as a cross-cut. The cross-cut was formed from the film protective layer side in a manner that the slits reached a part of the base film. For one of the slits of the potion where the cross-cut was formed, water was injected under the conditions of the injection temperature of 70°C, the injection flow rate of 10.5 L/min, the injection pressure of 9 ± 0.5 MPa, and the high-pressure washing was performed for 20 seconds. At this point, the distance from the tip of the washing nozzle to the decorative film was 15 cm, and the injection angle was 45°. Next, the same was performed for the other slit. After the high-pressure washing of the both slits, in the portion where the cross-cut was formed, delamination of the metal layer from the bonding layer was examined. The size of the delamination of the metal layer from the bonding layer in the portion where the cross-cut was formed is shown in Table 2.

For the strength of the bonding layer of each of the decorative films of Examples and Comparative Examples, 180° peeling test in accordance with JIS Z 0237 was performed in the conditions of 25 mm width, 300 mm/min, and the measurement temperature of 25°C. The 180° peeling strength at this time is shown in Table 2. For each of Comparative Examples 1 to 3, the peeling strength at the interface between the metal layer and the bonding layer is shown. For each of Examples 1 to 24, the peeling strength at the interface between the metal layer and the protective film layer is shown. That is, in Examples 1 to 24, the strength between the metal layer and the protective film layer is smaller than the strength between the metal layer and the bonding layer.

The durability of each of the decorative films of Examples and Comparative Examples was evaluated based on the following procedure and condition. The test with these procedure and condition is referred to as "water resistance test". First, the decorative film was heated to 120°C by the heating device used in the TOM. Then, the heating operation was stopped and the decorative film was brought down to room temperature (e.g. 23°C). This decorative film was immersed in water at 40°C for 240 hours, and then 30 minutes after the decorative film was taken out from the water, 100 squares of slits were formed by using a utility knife in a grid pattern having 2 mm pitch. The slits were formed from the film protective layer side in a manner that the slits reached a part of the base film. To the portion where the grid-patterned slits were formed, a piece of tape (CT-24S, Nichiban Co., Ltd.) was adhered onto the grid- patterned slits. This tape was then vigorously peeled off at the angle of 45°, and the number of squares of the metal layer delaminated from the bonding layer in the grid-patterned squares was checked. The number of the delaminated squares is shown in Table 2.

The appearance of each of the decorative films of Examples and Comparative Examples was evaluated. For each of the decorative films, presence or absence of a whitened portion or a crack-like line on the surface was visually observed. The case where the appearance was excellent without any whitening or crack -like line was evaluated as "+". The case where slight whitening or crack-like line was observed was evaluated as "±". The case where whitening or crack-like line was observed was evaluated as The results are shown in Table 2.

Table 2

High-pressure Water

Cooling/heating 180° Peeling

washing test resistance

cycle test (degree strength Appearance

(delamination (number of

of stretching, %) (N/25 mm)

amount, mm) delamination)

Example 1 189 0 15.8 0 +

Example 2 189 0 16.5 0 +

Example 3 207 0 16.1 0 +

Example 4 189 0 16.1 0 -

Example 5 207 1.5 14.2 0 +

Example 6 219 0.5 15.9 0 +

Example 7 211 0 15.4 0 +

Example 8 240 0 17.1 0 -

Example 9 195 0 18.1 0 -

Example 10 211 8 16.2 0 +

Example 11 228 3.5 15.7 0 +

Example 12 228 1 16.1 0 +

Example 13 228 1.5 16.9 0 +

Example 14 195 0 16.5 0 -

Example 15 215 0 13.8 0 -

Example 16 195 1.5 14.5 0 -

Example 17 195 1 13.9 0 +

Example 18 195 4.5 13.7 0 +

Example 19 195 5.5 11.8 0 +

Example 20 195 2 12.9 0 ±

Example 21 215 7 10.5 0 +

Example 22 215 7.5 12.5 0 +

Example 23 195 9 13.1 0 +

Example 24 195 2.5 15.2 0 +

Comparative

<165 0 12.0 100 + Example 1

Comparative

<165 7 10.4 100 + Example 2

Comparative

<165 9 4.9 100 + Example 3

Claims

What is claimed is:

1. A decorative film for hot stretch molding comprising: a base film, a bonding layer, a metal layer, and a film protective layer in this order; the bonding layer containing a reaction product of a composition containing a polyurethane polyol, a polyisocyanate, and a silane coupling agent.

2. The decorative film according to claim 1, wherein an equivalent ratio of isocyanate groups of the polyisocyanate to hydroxy groups of the polyurethane polyol is 5 or greater, and a content of the silane coupling agent is from 2 parts by mass to 12 parts by mass per 100 parts by mass of the polyurethane polyol.

3. The decorative film according to claim 1 , wherein an equivalent ratio of isocyanate groups of the polyisocyanate to hydroxy groups of the polyurethane polyol is from 5 to 9, and a content of the silane coupling agent is from 2 parts by mass to 12 parts by mass per 100 parts by mass of the polyurethane polyol.

4. The decorative film according to claim 1, wherein an equivalent ratio of isocyanate groups of the polyisocyanate to hydroxy groups of the polyurethane polyol is from 5 to 9, and a content of the silane coupling agent is from 2 parts by mass to 9 parts by mass per 100 parts by mass of the polyurethane polyol.

5. The decorative film for hot stretch molding according to any one of claims 1 to 4, wherein, in a case where the decorative film is uniaxially stretched at a degree of stretching of 189% or greater and subjected to heating and cooling, adhesion between the metal layer and the bonding layer is maintained.

6. The decorative film according to any one of claims 1 to 5, wherein, in a case where cuts are formed in a shape of a cross on the decorative film and the decorative film is subjected to high-pressure washing test, delamination occurred between the metal layer and the bonding layer is 2 mm or less.

7. The decorative film according to any one of claims 1 to 6, wherein 180° peeling strength at 25°C between the metal layer and the bonding layer is 15 N/25 mm or greater.

8. A decorative film for hot stretch molding comprising: a base film, a bonding layer, a metal layer, and a film protective layer in this order; wherein, in a case where the decorative film is uniaxially stretched at a degree of stretching of 189% or greater and subjected to heating and cooling, adhesion between the metal layer and the bonding layer is maintained.

9. The decorative film according to claim 8, wherein, in a case where cuts are formed in a shape of a cross on the decorative film and the decorative film is subjected to high-pressure washing test, delamination occurred between the metal layer and the bonding layer is 2 mm or less.

10. The decorative film according to claim 8 or 9, wherein 180° peeling strength at 25°C between the metal layer and the bonding layer is 15 N/25 mm or greater.