1. Field of the Invention
The present invention relates to a pressure-sensitive adhesive tape. More specifically, the invention relates to a pressure-sensitive adhesive tape having an excellent bubble-escaping property without using any PVC (polyvinyl chloride) film. The pressure-sensitive adhesive tape of the invention is in particular useful as a painting-alternate member excellent in design property which is desired particularly in the automobile industry and the house building material industry or as a tape or film for decoration or labeling.
2. Description of the Related Art
In general, surface-protecting pressure-sensitive adhesive tapes, pressure-sensitive adhesive tapes for decoration, and painting-alternate tapes for automobiles or houses are desired to have a relatively large sticking-area and a designed external appearance. For this reason, main currents in recent years are pressure-sensitive adhesive tapes wherein their peeling sheet (separator) is subjected to unevenness-forming working so as to have a continuous-groove structure and then this worked face is transcribed to a pressure-sensitive adhesive layer. Such pressure-sensitive adhesive tapes make it possible to cause fluids such as air and liquid to go off (or escape) through their distribution channels by the groove structure of their pressure-sensitive adhesive layer face. Thus, bubbles of the air or pools of the liquid are not easily generated.
As means in connection with the above, for example, the following have been suggested hitherto: a pressure-sensitive adhesive work sheet having a pressure-sensitive adhesive layer wherein a large number of independent small convex regions are arranged in the form of scattered points (see, for example, Registered Japanese Utility Models No. 2503717 and No. 2587198); an easily-sticking pressure-sensitive adhesive sheet having, in its pressure-sensitive adhesive layer face, distribution channels for air (see, for example, Japanese Patent Application Laid-Open (JP-A-) No. 63-223081); a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer wherein grooves are made between convex regions and adjacent convex regions (see, for example, JP-A No. 11-209704); an article with a pressure-sensitive adhesive which has a pressure-sensitive adhesive layer having a surface with fine structures of a small pitch size (see, for example, JP-A No. 2002-544364); a pressure-sensitive adhesive sheet the plastic deformation of which is controlled by the storage elastic modulus of an adhesive (see, for example, JP-A No. 2003-342533); and so on.
However, in almost all of practicable embodiments of these pressure-sensitive adhesive tapes, a PVC (polyvinyl chloride) film is used, and an adherend to which the film is stuck is exposed to a high temperature of 40 to 80° C. in particular immediately after the sticking, or is subjected to various kinds of heat hysteresis by the use thereof outdoors over a long term in many cases. Since the PVC film is excellent in workability, heat resistance, flexibility, solvent resistance, the film is widely used in members for building, automobiles, and housing. However, the PVC film depends largely on environment temperature; therefore, when this film is thin (100 μm), the film cannot keep the elasticity thereof in the step wherein the film is subjected to the heat hysteresis (for example, in an environment of 50° C. or higher temperature) so as to result in a drawback that the film is plastically deformed. It has been therefore become evident that when a groove structure remains in the above-mentioned pressure-sensitive adhesive layer or air bubbles are somewhat present between the grooves and an adherend and in this case the layer is subjected to heat hysteresis, the following problems are caused: the PVC film is plasticized so that the groove structure makes its appearance on the surface of the film; the film, the stress of which is not being kept, which results from expansion of the volume with a rise in the temperature of the remaining air bubbles, gets longer so that the external appearance thereof is damaged; and other problems. Additionally, many makers tend to restrict or abolish the use of PVC since PVC generates dioxins when PVC is incompletely burned at low temperature.
Furthermore, for example, about the article with the pressure-sensitive adhesive (see, for example, the JP-A No. 2002-544364), which has a pressure-sensitive adhesive layer having a surface with fine structures of a small pitch size, precise working is necessary when the article is produced. Thus, problems are caused from the viewpoint of the maintenance of the stability of such articles or costs. About the pressure-sensitive adhesive sheet the elastic deformation of which is controlled by the storage elastic modulus of the adhesive therein (see, for example, JP-A No. 2003-342533), the performance of the adhesive may not be appropriately obtained in accordance with the kind of an adherend to be used in some cases.