Marking Film Field of the Invention The present invention relates to a marking film, in particular, to a marking film that can be easily adhered to an adhered object having a three-dimensional curved surface without being accompanied by film necking, and more particularly to such a marking film that does not cause problems in terms of environmental contamination. The marking film of the present invention is preferably of the type used as an exterior film since it does not cause remarkable strain of the film even when adhered to a three-dimensional curved surface such as that of a vehicle.

Background As is commonly known, various types of exterior films are adhered to the chassis of motorcycles and automobiles, etc. to enhance their aesthetic beauty and decorativeness.

These exterior films are normally composed of a base material and an adhesive layer coated onto one side of that base material. In addition, polyvinyl chloride is frequently used for the base material due to its high moldability, weather resistance, durability and economy. However, since polyvinyl chloride has problems including toxicity of the raw materials as well as the dioxins produced during its incineration. Consequently, there has been growing activity in recent years to discontinue the use of polyvinyl chloride, namely to use a safe film material for the base material to take the place of polyvinyl chloride.

Polyolefin resin materials, which are close to polyvinyl chloride in terms of price, have attracted attention as a new film material. In addition, among these resin materials, since polypropylene in particular has high strength comparable to polyvinyl chloride originating in its high crystallinity, it is coming to be widely used.

However, as a more recent trend, since the vehicle surfaces to which exterior films are adhered contain three-dimensional curved surfaces such as indentations and curves, it is not easy to adhere an external film having a polyolefin resin material for its base material to a surface having this type of complex shape. Film necking (phenomenon in which the film is constricted) occurs due to stretching of the film when adhering an exterior film, and when this film necking occurs, a portion of the exterior film is deformed resulting in the formation of lines that cause the product value to be lost.

Summary of the Invention The present invention provides a marking film that can be easily adhered to the surface of an adhered body having a three-dimensional curved surface without causing defects such as film necking. The present invention can also provide such a marking film that does not cause problems in terms of environmental contamination.

The present invention can further provide a marking film having superior strength, moldability, weather resistance, durability and economy.

In addition, the present invention can provide a marking film that is useful as an exterior film of motorcycles, automobiles and other vehicles.

A marking film, according to the present invention, comprises a base material of olefin resin and an adhesive layer coated on one side of the base material. The base material has a deformation index of at least 0.81 (here, the"deformation index"refers to that which is determined from a stress-strain curve of the base material, and is the value obtained by dividing the minimum stress X2 that initially appears after the yield point, by the yield point stress Xl).

Brief Description of the Drawings Fig. 1 is a cross-sectional view showing an example of the constitution of the marking film of the present invention.

Fig. 2 is a graph showing the manner of determining the deformation index of a marking film.

Fig. 3 is a cross-sectional view showing a metal plate containing an indentation that was used to evaluate matching relative to a three-dimensional curved surface.

Fig. 4 is a cross-sectional view showing examples of the use of metal plates containing indentations shown in Fig. 3 in their order of use.

Fig. 5 is a correlation diagram showing the relationship between the deformation index and three-dimensional curvature matching of marking films with respect to metal plate 1.

Fig. 6 is a correlation diagram showing the relationship between the deformation index and three-dimensional curvature matching of marking films with respect to metal plate 2.

Detailed Description As is described above, the marking film according to the present invention comprises at least: (1) a base material made of an olefin resin, and (2) an adhesive layer coated onto one side of the base material.

Moreover, a release paper is preferably provided on the side of the adhesive layer to protect the adhesive layer and improve handling ease. Fig. 1 schematically shows a marking film of the present invention having such a typical constitution, and marking film 10 is shown to have a base material of olefin resin 1, adhesive layer 2 coated on one side of that base material 1, and release paper 3 covering adhesive layer 2. A decorative pattern not shown is printed on base material 1.

The marking film of the present invention is a film-like member that is used by adhering to an adhered body, and particularly an adhered body having a three-dimensional curved surface, for the purpose of marking, decoration and so forth. Typical examples of this marking film include, but are not limited to, an automobile or other vehicle exterior film, signboard and so forth.

In the case of using as a vehicle exterior film, the marking film of the present invention can be used by adhering and fastening to the chassis or parts of a scooter, motorcycle, automobile, train or other vehicle.

As was previously described, the marking film of the present invention is composed by comprising at least a base material of olefin resin and an adhesive layer coated onto one side of that base material.

In the marking film of the present invention, in addition to the olefin resin used for the base material being able to impart high strength to the marking film, it also prevents the occurrence of film necking even when the film is stretched. The inventor of the present invention has found that the combination of these superior characteristics is derived from a deformation index determined from a stress-strain curve of the base material. Namely, the base material composed of an olefin resin is required to have a <BR> <BR> deformation index of at least 0. 81. Here, "deformation index", in the case of being used in the specification of the present application, is determined from the stress-strain curve of the base material, and refers to the value obtained by dividing the minimum stress X2 that initially appears after the yield point by the yield point stress Xi. Namely, as shown in the

attached drawing of Fig. 2, in the case of plotting the stress-strain curve I of a certain specific film, when the minimum stress that appears after the yield point relative to the yield point stress Xi is taken to be X2, the ratio Y of both (= X2/Xl) can be referred to as the deformation index. Furthermore, the deformation index of the base material is more preferably at least 0.86. If the deformation index of the base material is less than 0.81, film necking ends up occurring when the marking film is adhered.

In addition, the olefin resin used as the base material includes numerous olefin resins widely used in the fields of marking films and other film products. Examples of olefin resins preferable for carrying out the present invention include, but are not limited to, polypropylene (PP), polyethylene (PE), ethylene/propylene copolymer, ionomer, EAA (ethylene-acrylic acid copolymer), EEA (ethylene-ethyl acrylate copolymer) and EVA (ethylene-vinyl acetate copolymer).

The base material is normally composed of only one of the above olefin resins. In addition, the base material is preferably molded by blending a rubber component, and preferably a rubber-based resin, into these olefin resins according to a different method.

Preferable examples of a blended rubber component include thermoplastic olefins (TPO).

Typical examples of TPO include a blend of PP and a rubber component such as EPDM (ethylene/propylene/diene monomer copolymer). This is because the blending in of a rubber component is able to impart rubber-like behavior to base materials having high strength.

The base material of olefin resin may be transparent, semi-transparent or opaque according to the purpose of use of the marking film. In addition, colorants such as phthalocyanine blue pigment, azo red pigment, aluminum black or mica powder may also be contained for the purpose of improving appearance and decorativeness. Moreover, other additives such as ultraviolet absorber may also be contained. In addition, a decorative pattern and so forth may be printed or transferred to the surface of the base material.

Although a base material like that described above can be used at various thicknesses according to the purpose of use of the marking film and so forth, the thickness is normally within the range of about 5 to 500 um, and preferably within the range of about 30 to 300 um. If the thickness of the base material is less than 5 um, the handling ease of the film decreases and decorative effects originating in the thickness are unable to

be adequately demonstrated. Conversely, if the thickness of the base material exceeds 500 ßm, since the overall thickness of the film increases, a decrease in workability cannot be avoided. Furthermore, although the base material is normally used in the form of a single layer, a multi-layer structure consisting of two or more layers may also be employed as necessary.

Although the base material may be used as is as a component of the marking film, it may also have an ink layer, clear layer or other additional layer on its surface, namely the surface on the opposite side of the adhesive layer, and particularly preferably has an ink layer composed of urethane resin. The urethane resin used here is preferably a single- liquid type of non-yellowing urethane resin. This urethane resin is particularly useful with respect to being able to impart weather resistance and scratch resistance to the marking film.

The ink layer and clear layer may be transparent, semi-transparent or opaque according to the purpose of use of the film in the same manner as the above base material.

In addition, the ink layer may also contain various types of colorants such as phthalocyanine blue pigment, azo red pigment, aluminum black or mica powder for the purpose of improving appearance and decorativeness. Moreover, other additives such as ultraviolet absorbers, photostabilizers and luster adjusters may also be added. Ultraviolet absorbers and photostabilizers function to effectively prevent deterioration when the exterior film and its underlying parts are exposed to sunlight, while luster adjusters function to control the surface luster of the exterior film.

An adhesive layer is coated onto one side of the base material in the marking film of the present invention. Examples of substances from which the adhesive layer used here is formed include, but are not limited to, pressure-sensitive adhesives (PSA) such as polyacrylate, tackifying rubber, tackifying synthetic rubber, ethylene vinyl acetate and silicone.

The thickness of the adhesive layer can be changed over a wide range corresponding to numerous factors including the composition of the adhesive, type of adhered object and thickness of the base material. In general, the thickness of the adhesive layer is within the range of about 10 to 50 gm, and preferably within the range of about 25 to 40 Rm.

The marking film of the present invention may also have a primer layer. The primer layer can be provided at a layer thickness of about 0.1 to 10 um between the base material and adhesive layer. In addition, the primer layer can also be provided at a layer thickness of about 0.1 to 10 um between the base material and ink layer.

The marking film of the present invention is preferably provided with release paper on the side of the adhesive layer to protect the adhesive layer and improve the handling ease of the marking film. The release paper used here may be that which is typically used in the fields of adhesive tape and so forth, and is not limited to a specific material.

Preferable examples of release paper used in the present invention include those composed of paper or plastic materials such as polyethylene, polypropylene, polyester and cellulose acetate, as well as paper and other materials covered or laminated with these types of plastic materials. Although this release paper may be used as is, it is preferably used after release characteristics have been improved by silicon treatment or another method of treatment. In addition, although the thickness of the release paper can be changed arbitrarily, it is normally within the range of about 25 to 500 um, and preferably within the range of about 50 to 200 um.

Examples The following provides a detailed explanation of the present invention with reference to its examples. Furthermore, it should be understood that the present invention is not limited by the following examples.

Base material films were obtained by extrusion molding the following resin materials with a single-screw extrusion molding machine (Brabender) equipped with a die (Plasti-Corder) in the drive unit. Furthermore, some of the base materials were extrusion molded by blending the following raw materials as shown in the following Table 1. The total thickness was adjusted to 100 jim for all of the base materials.

Raw Material Supplier E-2900H Idemitsu Petrochemical Co.

W151 Sumitomo Chemical Co.

FLX80E3 Sumitomo Chemical Co.

H1052 Asahi Kasei Kabushikikaisha

Next, each of the base materials was guided into a corona treater (output: 1.0 kw) at a speed of 10 m/min. to perform coronal discharge treatment on one side of the base material.

Next, an acrylic pressure-sensitive adhesive (PSA) was coated onto one side of a silicone-treated polyester film used as release paper (trade name:"Crisper" (registered trademark) K2372", Toyobo) with a bar coater to a film thickness after drying of about 0.03 mm, followed by heating and drying. The monomer composition of the acrylic pressure-sensitive adhesive was butyl acrylate/acrylic acid = 90/10.

Continuing, the coronal discharge treated side of the base material and the adhesive layer after heating and drying of the release paper were laminated to produce the target marking films as described in the following Table 1.

Evaluation Testing Samples of each of the marking films produced in the manner described above were evaluated using the testing methods described below for deformation index (from a stress-strain curve), elasticity and three-dimensional curvature matching.

Measurement of Deformation Index: The marking films were cut into strips measuring 15 mm wide x 100 cm long either in the lengthwise direction (MD) or widthwise direction (TD) as described in the following Table 1. The stress-strain curve of each sample was measured using a tensile tester (trade name:"UCT-100", Orientech). The measurement conditions consisted of a distance between chucks of 50 mm and measuring speed of 200 mm/min.

Stress-strain curves as previously explained with reference to Fig. 2 were obtained for each sample. Accordingly, the ratio (X2/Xi) of minimum stress X2 to yield point stress Xi was measured to determine the deformation index Y shown in the following Table 1.

Furthermore, the portion between Xi and X2 in the curves is the portion at which film necking occurs.

Three-Dimensional Curvature Matching: In order to evaluate the extent to which the marking film is able to match a three- dimensional curvature, two types of metal plates 11 having a semi-cylindrical indentation

(pseudo three-dimensional curvature) 12 in their centers were prepared as shown in Fig. 3.

In metal plate 1, the diameter (a) of the indentation was 16 mm and the circumference b was 18 mm. In metal plate 2, the diameter (a) was 34 mm and the circumference (b) was 40 mm. Furthermore, since both indentations 12 had an extremely three-dimensional curvature, if the marking film was able to adhere to these indentations without being accompanied by film necking, the marking film was allowed to be used.

The marking film was cut into strips measuring 25 mm wide x 100 cm long. Each marking film 10 was adhered to the surface of metal plate 11 so as to cover indentation 12 as shown in Fig. 4 (A), after which it was adhered to the inner surface of indentation 12 while being pressed on by plastic squeegee 13. Ideally, as shown in Fig. 4 (B), marking film 10 is in a state in which it is stretched uniformly and tightly adhered to the inner surface of indentation 12 without being accompanied by defects such as film necking.

Accordingly, in order to evaluate the three-dimensional curvature matching of each marking film, the manner in which the film stretched after adhering was observed visually, and the appearance of necking was classified to one of the following five classes.

Class 1: Entire film stretched uniformly and necking was not observed.

Class 2: Film edges were slightly distorted Class 3: Film width was narrower at some locations and necking was discernible.

Class 4: Film constriction was clearly able to be recognized.

Class 5: A borderline appeared between parts of the film that were stretched and those that were not.

Namely, those films that were classified as either class 1 or class 2 were considered to satisfy the requirements of the present invention.

Evaluation results were obtained for metal plates 1 and 2 as summarized in Table 1 below.

Table 1 Curvature Curvature Sample matching matching cutting Deformation relative to metal relative to metal Sample direction index Y plate 1 (class) plate 2 (class) E-2900H Lengthwise 0.79 2 3 (MD) E-2900H Widthwise 0.82 2 4 (TD) FLX80E3: Lengthwise 0.8 2 2 H1052 = 9 : 1 (MD) FLX80E3: Widthwise 0.9 1 2 H1052 = 9 : 1 (TD) FLX80E3: Lengthwise 0.83 1 2 H1052 = 9 : 1 (MD) FLX80E3: Widthwise 0.89 1 2 H1052 = 9 : 1 (TD) W151 Lengthwise 0.68 5 5 (MD) W151 Widthwise 0.71 5 5 (TD) FLX80E3 Lengthwise 0.68 4 5 (MD) FLX80E3 Widthwise 0.71 4 5 (TD) FLX80E3: Lengthwise 0. 74. 3 4 H1052 = 9 : 1 (MD) FLX80E3 : Widthwise 0.74 3 5 H1052 = 9 : 1 (TD) FLX80E3: Lengthwise 0.81 4 4 H1052 = 9 : 1 (MD) FLX80E3 : Widthwise 0.8 3 4 H1052 = 9 : 1 (TD) FLX80E3: Lengthwise 0. 79 3 3 H1052 = 9 : 1 (MD) FLX80E3 : Widthwise 0.84 3 4 H1052 = 9 : 1 (TD)

The marking films produced in the examples had mean elongation percentages of 12.5% and 17.6% for metal plates 1 and 2, respectively. However, since the load that is applied to the marking films when they are adhered is normally 10% or less, those films that are able to match the shape of the indentation of metal plate 1 do not present problems in-practical terms. However, in consideration of the increasing diversity and complexity of shapes in the future, it is more desirable to also be able to match the shape of the extreme indentation of metal plate 2. It would be no exaggeration to say that being able to

match the shape of metal plate 2 would enable the marking film to be compatible with a wide range of types of curved surfaces.

When graphs were plotted of the relationship between deformation index and three-dimensional curvature matching based on the evaluation results described in Table 1, the correlation diagrams shown in Fig. 5 (for metal plate 1) and Fig. 6 (for metal plate 2) were obtained. Moreover, the following equations were obtained when the respective correlations were determined with a linear function from the least square method.

For metal plate 1: Deformation index Yl =-0.043 (Xi (l)) +0. 90 (Equation 1) For metal plate 2: Deformation index Y2 =-0.046 (Xi (2)) +0.95 (Equation 2) Here, since the practically allowed curvature matching class when adhering the marking film to an adhered object having a three-dimensional curved surface is class 1 or class 2 as previously mentioned, the deformation indices of marking film able to be advantageously adhered to the three-dimensional curved surfaces are as indicated below.

Metal plate 1: 0.81 or more (according to Equation 1) Metal plate 2: 0.86 or more (according to Equation 2) In summary, a marking film that is able to match an adhered object having a three- dimensional curved surface has a deformation index as determined from its stress-strain curve of preferably 0. 81 or more, and more preferably, 0. 86 or more.

As has been explained above, according to the present invention, as a result of attempting to eliminate the use of polyvinyl chloride, a marking film is able to be provided that not only is able to avoid problems of environmental contamination, but is also able to be easily adhered to an adhered object having a three-dimensional curved surface without causing the problem of film necking when the film is adhered. In addition, since the marking film of the present invention has superior characteristics such as superior strength, moldability, weather resistance, durability and economy, it is suitable for use as an automobile exterior film.