Protective Film for Exterior Decoration of Vehicles Field of the Invention This invention relates to an exterior decoration technology for vehicles, in particular, to a protective film for exterior decoration of vehicles such as, for example, automobiles, aircraft and watercraft that can satisfy both decoration function and protection function and, more particularly, to an exterior decoration film for automobiles that accomplishes at least one of does not invite a problem of environmental pollution, can follow complicated concave, convex or concavo-convex shapes of side surfaces of the vehicles and can be easily bonded.

Background of the Invention An exterior decoration technology of vehicles such as automobiles generally uses electrostatic painting that applies color paints to specific areas of a vehicle body to improve decorativeness. To further improve this decoration performance, two-color or two-tone painting is often employed, too. Besides the improvement of decoration performance, painting of color paints has also a rust-proofing function of protecting a steel sheet constituting the car body from rust. However, since a film obtained by such painting is extremely thin, flying pebble often damages the film during driving of the automobile and rust develops in many cases from that portion. This problem is particularly remarkable on the side surfaces of the car body and portions below the side surfaces.

To prevent the occurrence of such rust, it has been customary to apply anti- chipping painting to the side surfaces of the car body which flying pebbles are likely to hit, by use of a vinyl chloride type sol, or to bond a urethane type protective tape (see for example: Japanese Unexamined Patent Publication (Kokai) No. 59-135276, Japanese Unexamined Patent Publication (Kokai) No. 62-266177, Japanese Unexamined Patent Publication (Kokai) No. 3-205150 and Japanese Unexamined Patent Publication (Kokai) No. 4-126570. ). However, the vinyl chloride sol used for antichipping painting unavoidably involves the environmental problem such as scatter of an organic solvent used for painting and the generation of detrimental substances such as dioxine created upon burning of steel sheets for recycling. The method of bonding the urethane type protective tape is free from the environmental problem and the problem of performance.

However, a thick tape having a thickness of from about 150 to 300 llm must be bonded to acquire the intended protection function. Therefore, the cost of production becomes higher and this method is not industrially feasible. Moreover, additional painting and bonding of the protective tape besides painting of the color paints unavoidably invite the increase of the number of production steps and the rise of the production cost.

Summary of the Invention In an effort to solve one or more of the problems described above or other problems, the present invention aims at providing a protective film for exterior decoration of vehicles (e. g. , automobiles, etc. ) that can satisfy both a decoration function (e. g., improvement of appearance and decorativeness) and a protection function (e. g., improvement of chipping resistance and rust-proofness) but does not invite or significantly reduces the problem of environmental pollution.

The present invention can provide a protective film for exterior decoration of vehicles (e. g. , automobiles, etc. ) that can follow complicated concave, convex or concavo- convex shapes of side surfaces of automobiles and can be bonded easily to such surfaces.

The present invention can also provide a protective film for exterior decoration of vehicles (e. g. , automobiles, etc. ) that can be used to accomplish one or more of the following: substitute two-tone color painting of the prior art, exhibit an equivalent decoration effect and be easily handled.

In one aspect of the present invention, there is provided a protective film for exterior decoration of vehicles (e. g. , automobiles, etc. ), which comprises a film-like substrate formed of an olefin type elastomer and an adhesive layer applied to a side of the substrate to be bonded to an article (e. g. , a body of a vehicle), and in which a thickness of the substrate is in the range of from about 250 to about 1, 000 llm ; and an elastic modules of the substrate is in the range of from about 55 to about 65 MPa when the thickness of the substrate is in the range of from about 250 pm to less than about 300 J, m, or the elastic modulus of the substrate is in the range of from about 45 to about 65 MPa when the thickness of the substrate is in the range of from about 300 to about 1,000 jjm or about 300 llm or more.

Brief Description of the Drawings Fig. 1 is a sectional view showing one layer construction of a protective film for exterior decoration of automobiles according to the invention.

Fig. 2 is a sectional view showing another layer construction of a protective film for exterior decoration of automobiles according to the invention.

Detailed Description of Inventive Embodiments The present invention will hereafter be described in detail with reference to specific applications with automobiles. It is understood, however that the present invention is not necessarily intended to be so limited.

The protective film for exterior decoration of automobiles according to the invention can be advantageously carried out in various embodiments.

Bonded articles or adherends to which the protective film of the invention is to be bonded are not particularly limited, and include various types of automobiles for which the decoration function and the protection function of the protective film are required.

Generally, the protective film of the invention can be appropriately applied to the car bodies of automobiles such as buses and passenger cars. The protective film of the invention can exhibit its excellent functions when bonded to the side surfaces of the passenger car, the lower portions of the side surfaces, and portions having roll-up shapes such as door corners, and so forth. Needless to say, the protective film of the invention can be used not only for the protection of the car body and exterior decoration components but also as a substitute of paints. Its typical example is two-tone color painting. Further, since flying pebbles are likely to hit a cowl panel (windshield fitted to frame) of bicycles and scooters, the protective film of the invention can be used advantageously.

The protective film for exterior decoration of automobiles according to the invention comprises at least a film-like substrate formed of an olefin type elastomer and an adhesive layer applied to a substrate on its bonded article side. An additional layer or layers that are conventionally used in the field of exterior decoration films may be arbitrarily added.

Fig. 1 is a sectional view that shows a protective film for exterior decoration of automobiles according to one preferred embodiment of the invention. The protective film 10 shown in the drawing has a film-like substrate 1 and an adhesive layer 8 applied to the

film-like substrate 1 on the side of a bonded article (not shown). A primer layer 2 is sandwiched between the substrate 1 and the adhesive layer 8 to secure excellent adhesion between them. Peel paper (release liner) 9 protects the adhesive layer 8 to retain adhesiveness from the production of the protective film to its use and to improve handling property of the protective film.

The film-like substrate used for the protective film according to the invention has a thickness within the range of 250 to 1,000 um and has a specific elastic modulus, described below, so as to impart a protection function of a desired level to the protective film and to let it follow complicated concave, convex or concavo-convex shapes of the side surfaces of the automobile.

(1) The elastic modulus of the substrate is within the range of 55 to 65 MPa when the thickness of the substrate is greater than 250 um and less than 300 am.

(2) The elastic modulus of the substrate is within the range of 45 to 65 MPa when the thickness of the substrate is 300 jjm or more.

The thickness of the film-like substrate is generally within the range of 200 to 800 (mi as described above. When the thickness of the substrate is smaller than 250 um, chipping resistance equal to that of conventional urethane films cannot be secured. When the thickness of the substrate exceeds 1,000 jjm, the protective film becomes so thick that it cannot satisfy the requirement for appearance and decoration performance, and the handling property drops, too. The thickness of the substrate is preferably within the range of 250 to 400 um and is further preferably within the range of 250 to 300 um.

In the practice of the invention, the material of the film-like substrate is not particularly limited so long as the requirement for the elastic modulus described above is satisfied, but is preferably a polymer alloy. Further preferred among the polymer alloys are thermoplastic olefins generally called TPO (thermoplastic polyolefin) and TPE (thermoplastic elastomers). The polymer alloy suitable for the substrate is an alloy of an olefin type elastomer, e. g. an olefin such as polypropylene, and a rubber component such as EPDM (ethylene-propylene-diene terpolymer), styrene or SBS (styrene-butadiene- styrene block copolymer). The olefin type elastomer that is particularly preferred is the alloy of polypropylene and EPDM. When the blend amount of the rubber component and the thickness of the substrate are suitably controlled in these polymer alloys, it becomes possible to obtain a protective film having high chipping resistance and follow-up property

to the three-dimensional curve surfaces. The substrate formed of such a polymer alloy has suitable stiffness and can be therefore bonded more easily to the bonded article than the conventional urethane films.

The film-like substrate may be colorless, translucent or opaque, and an optimum form can be selected in accordance with the intended application of the protective film.

To improve appearance and decoration performance, however, the substrate is preferably colored either wholly or partially and has a decoration function. The substrate can be advantageously colored by, for example, blending a suitable colorant, e. g. a phthalocyanine blue pigment, an azo red pigment, aluminum flake or mica powder, during the preparation of the substrate. Besides the colorant, the substrate may further contain other additives such as a UV absorbing agent.

The adhesive layer can be formed to an arbitrary thickness by use of a variety of adhesives. Examples of pressure-sensitive adhesives that can be suitably used in the practice of the invention include polyacrylate, tackifying rubber, tackifying synthetic rubber, ethylene vinyl acetate and silicone, though these examples are not restrictive.

The adhesive layer can be used at an arbitrary thickness. The thickness of the adhesive layer is generally within the range of about 30 to 60 p. m and is preferably within the range of about 40 to 45 m. Note that the adhesive layer may be used outside the range of thickness described above so long as the desired bonding strength can be secured and adverse influences are not exerted on the operation of the invention.

The protective film for exterior decoration of automobiles according to the invention preferably has peel paper on the side of the adhesive layer to protect the adhesive layer and to improve handling property of the protective film. Peel paper may be the one that is generally used in the field of adhesive tapes, and is not limited to specific members. Peel paper is formed of paper or plastic materials such as polyethylene, polypropylene, polyester or cellulose acetate, or paper or other materials that are covered with such a plastic material or is laminated with the plastic material. This peel paper may be used either as such or is used after it is subjected to silicone treatment or other treatment to improve peel performance. The thickness of peel paper can be arbitrarily changed but is generally within the range of about 25 to 500 go and is further preferably within the range of about 50 to 200 jum.

In the protective film shown in the drawing, a primer layer is sandwiched between the substrate and the adhesive layer to improve the bonding strength between them. The primer layer can be formed by applying a urethane type resin to a predetermined thickness as has been practiced generally in the production of adhesive films. The thickness of the primer layer is generally within the range of about 0.5 to 10 pm. Surface treatment such as corona discharge treatment may be applied to the surface (adhesive layer-forming surface) of the substrate in place of, or prior to, the formation of the primer layer.

In the protective film according to the invention, the substrate itself may have the decoration function as described above. It is recommended, however, to dispose an additional layer or layers on the substrate of the protective film to obtain a further decoration function and other additional functions (for example, weatherability and durability). Examples of suitable additional layers are a color layer and a clear layer, though they are not restrictive. These layers may be used either alone or in combination of two or more layers.

Fig. 2 shows a protective film for exterior decoration of automobiles according to another preferred embodiment of the invention. The protective film 10 has the primer layer 2, the adhesive layer 8 and peel paper 9 arranged below the substrate 1 in the same order as in Fig. 1. The protective film 10 further has a color layer 4 and a clear layer 5 on its surface in this order. A primer layer 3 that is the same as, or different from, the primer layer 2 is also sandwiched between the substrate 1 and the color layer 4 to improve the bonding strength.

The color layer can be formed by use of a method that is generally employed in the field of decorative films. The color layer can be advantageously formed by, for example, blending suitable amounts of colorants, etc, with the resin material, and applying the mixture to a predetermined thickness. The thickness of the color layer can be changed in a broad range, but is generally within the range of about 5 to 30 jjm and is preferably within the range of about 5 to 10 lem.

The clear layer is preferably formed of a urethane resin. The urethane resin used herein is preferably a two-part type urethane resin. This urethane resin is advantageous particularly because it can impart weatherability and scratch resistance to the film.

The clear layer, too, may be transparent, translucent or opaque in accordance with the object of use of the film in the same way as in the case of the substrate. The clear

layer may contain additives such as a UV absorbing agent, a gloss-regulating agent, and so forth. The UV absorbing agent has the function of effectively preventing degradation of the protective film and the car body and the components below the protective film while they are exposed to solar rays. The gloss-regulating agent imparts excellent gloss to the surface of the protective film and improves decoration performance.

The clear layer can be used at a variety of thickness depending on the application of the protective film. Generally, however, the thickness is within the range of about 1 to 50 urn and is preferably within the range of about 5 to 20 um. When the thickness of the clear layer is smaller than 1 J. m, the clear layer fails to impart sufficient weatherability and scratch resistance to the protective film. When the thickness exceeds 50 p. m, the clear layer cannot remarkably improve such functions any more.

The protective film for exterior decoration of automobiles according to the invention can be produced in accordance with various methods generally employed for forming films. For example, the starting materials of the substrate are blended in an arbitrary proportion, and the resulting blend is kneaded and calender-molded into a film form. Next, surface treatment is applied by corona discharge to both surfaces of the resulting film-like substrate, and a primer is further applied to the surface to form a primer layer. On the other hand, the adhesive is applied to peel paper, separately prepared, at a predetermined thickness to form the adhesive layer. This peel paper is superposed with one of the surfaces of the substrate and is bonded through the adhesive layer. The color layer and the clear layer are serially printed by screen-printing on the exposed surface (surface opposite to the adhesive layer) of the substrate, and are dried. In this way is obtained the protective film for exterior decoration of automobiles as shown in Fig. 2.

Examples Next, the invention will be explained in detail with reference to examples thereof.

It is to be understood that the invention is in no way limited to these examples.

Production of film-like substrate Thirteen (13) kinds of substrates listed below were produced to use them as the substrate of each protective film. In the substrates 1 to 9, an olefin type elastomer "Milastomer 7030N" (trade name, EPDM-rich elastomer, a product of Mitsui Chemicals Inc. ) and"MilastomerTM 9020N" (PP-rich elastomer, trade name) were kneaded in the

following proportions and were extrusion-molded to form films. In substrates 10 to 12, an olefin type elastomer "MilastomerTM 9020was alone extruded to form films. For the reference, a substrate 13 was produced to simulate a conventional urethane film, and the film was formed of a urethane resin "MorthaneTM PN3429-218" (trade name, a product of Morton). Elastic Substrate Modulus Thickness No. Blend Proportion (MPa) (Rm) 1 7030N : 9020N=25: 75 37 200 27030N : 9020N=25: 75 37 250 3 703ON : 9020N=25: 75 42 300 4 703ON : 9020N=20: 80 51 200 57030N : 9020N=20: 80 45 250 6 7030N : 9020N=20: 80 45 300 7 703ON : 9020N=10: 90 56 200 8 703ON : 9020N=10: 90 46 250 97030N : 9020N=10 : 90 50 300 10 9020N=100 59 200 11 9020N=100 58 250 12 9020N=100 63 300 13 Urethane resin 22 150

Production of protective film Protective films 1 to 13 having the laminate structures shown in Fig. 2 were produced in the following way by use of the substrates 1 to 13 prepared as described above.

The film-like substrate was guided to a corona treating apparatus (output: 1.0 KW) at a rate of 10 m/min, and corona discharge treatment was conducted for both surfaces of the substrate. Next, a primer coating solution of a urethane type was applied to both corona discharge treatment surfaces of the substrate by use of a gravure coater, and was

heated and dried inside a hot window oven. A primer layer having a thickness of about 5 pm after drying was obtained.

Separately, peel paper ("Crisper K2327", a product of Toyobo) was prepared, and an acrylic type pressure-sensitive adhesive (isooctyl acrylate: acrylic acid = 90: 10) was applied to one of its surfaces by using a bar coater and was then heated and dried inside a hot wind oven. An adhesive layer having a thickness of about 45 jjm after drying was obtained.

Next, the substrate and peel paper were bonded to each other by use of a laminator in such a fashion that the primer layer of the substrate and the adhesive layer of peel paper came into close contact with each other. There was thus obtained a film having a good bonded surface and free from air entrapment.

Subsequently, a color pattern was printed by silk-screen to the exposed primer layer of the bonded film, and was heated and dried inside the hot wind oven. Black ink ("FL545", trade name, a product of Sumitomo 3M Ltd. ), transparent ink ("FL510", trade name, a product of Sumitomo 3M Ltd. ) and metallic ink ("Albaste", trade name, a product of Toyo Aluminum) were used as the printing ink. A color layer having a thickness of about 10 ßm after drying was obtained.

After the formation of the color layer, a clear layer was formed in the same way as the formation of the color layer. Printing ink was a clear paint ("GA-3", trade name, a product of Sumitomo 3M Ltd. ). A clear layer having a thickness of about 10 jjm after drying was obtained, and production of the protective film was completed.

All the protective films thus produced (referred to as"protective films 1 to 13" corresponding to the number of substrates) had sufficient appearance and were free from variation of coloring.

Evaluation test Chipping resistance and film bondability were evaluated for the protective films 1 to 13 by the following testing methods, respectively.

Chipping resistance: Each protective film was cut into 50 mm x 50 mm to prepare a test piece, and the test piece was bonded to a melamine-painted plate. The painted plate was put into a refrigerator and was cooled to-30°C. The chipping resistance test was conducted under

the following condition by use of gravel chipping tester"JA-400" (a product of Suga Test Instrument Inc. ). gravel: No. 6 gravel (basalt) gravel weight: 500 g air pressure: 4 kg/cm2 After the test was completed, the test piece was peeled from the melamine-painted plate and the existence/absence of chipping scratch on the surface of the painted plate was checked with eye. The test result summarized in the following Table 1 was obtained.

Film bondability (Film applicability) : Each protective film was bonded to a corner (roll-up portion) of a door of a passenger car and bondability was functionally judged. Also, the occurrence of appearance defect such as crease was inspected with eye, and the protective film was evaluated by the sum of both of them (1 to 6). An evaluation standard was as follows: 6: superexcellent 5: excellent 4: good 3: fair 2: inferior 1: failure When the protective films had points of 4 to 6, they could be quickly bonded without causing the appearance defect such as crease. At the point 3, the occurrence of crease was observed to some extents, but the protective films were permissible as a whole.

Table 1 No. of Film Bondability protective film Chipping Resistance (observation) 1 granularly scattered scratches were observed on a 5 painted surface 2 granularly scattered scratches were observed on a 5 painted surface 3 granularly scattered scratches were observed on a painted surface 4 granularly scattered scratches were observed on a painted surface 5 granularly scattered scratches were observed on a 5 painted surface 6 good (no scratch was observed) 4 7 granularly scattered scratches were observed on a 5 painted surface granularly scattered scratches were observed on a 5 painted surface 9 good (no scratch was observed) 4 granularly scattered scratches were observed on a painted surface 11 good (no scratch was observed) 5 12 good (no scratch was observed) 4 13 good (no scratch was observed) 3

It could be concluded from the test results tabulated in Table 1 that excellent chipping resistance could be obtained when: Elastic modulus of the substrate was at least 45 MPa and the thickness of the substrate was at least 300 tm ; and Elastic modulus of the substrate was at least 55 MPa and the thickness of the substrate was at least 250 um.

It could be also understood that the protective films prepared by the examples of the invention had better film bondability than the conventional urethane films.

Incidentally, when the thickness of the substrate became greater than 300 J. m, the protective substrate of the invention exhibited greater strength and became more difficult to bond, though such a substrate was not tabulated in Table 1 because no problem occurred in practice in using the substrate.

It could thus be concluded that in order to simultaneously satisfy chipping resistance and bondability, the elastic modulus be within the range of 55 to 65 MPa when

the thickness of the substrate was from 250 llm to less than 300 urn, or the elastic modulus be from 45 to 65 MPa when the thickness of the substrate was 300 nm or more.

As explained above, the invention can provide a protective film for exterior decoration of automobiles that can satisfy both decoration function (for example, improvement of appearance and decoration performance) and protection function (for example, chipping resistance and improvement of rust-proofness) and does not invite the problem of environmental pollution.

The invention can further provide a protective film for exterior decoration of automobiles that can substitute conventional two-tone color paints, can exhibit an equivalent decoration effect, and can be easily handled.