Adhesive tapes made with planar papers have been known as a tape comprising a resinous-substance-impregnated planar paper as a backing and an adhesive layer on the paper. Such adhesive tapes are required to be adhered to an adherend surface favorably without being accompanied by any lift and separation, but with consistently conforming to the curved surface area and/or the rough surface area in such adherend surface, when the adhesive tapes are used as a paint masking or a masking for curing a rough surface, in fixing electronic component parts or in any other application.
In recent years, in the automotive industry where the recent mode of automotives frequently employs curved shapes, the adhesive tapes for paint masking used in the production process of the automotives are further required not only to have a good conformability to the curved surfaces to be adhered but also to provide a clear painting line left in a portion of a painted surface.
Conventional planar papers for adhesive tapes as the backings have been mainly made of natural pulps having celluloses as a base component, such as wood pulps, hemp pulps, linter pulps and the like. In addition, in some cases, synthetic fibers are used in order to improve elongation or strength characteristics required for tapes. In such cases, polyester fibers or polyolefinic fibers are found to be a candidate as the synthetic fibers (for example, see Patent Document 1). However, these fibers are incompatible to resins which are used for impregnation into the papers, and sometimes adversely affect the obtained tape characteristics.
On the other hand, in view of affinity to resins, polyvinyl alcohol fibers have been favorably used because of their good compatibility to the resins (for example, see Patent Documents 2 and 3). The polyvinyl alcohol fibers have an improved affinity to resins, and thereby the elongation and strength characteristics of the adhesive tapes are improved by using the polyvinyl alcohol fibers. However, the conventional polyvinyl alcohol fibers cannot impart enough elongation to the adhesive tapes. Thus, even if the adhesive tapes comprising such polyvinyl alcohol fibers have conformability to gently curved lines, the adhesive tapes cannot sufficiently conform to a non-gentle curved line required in the production process of the automotives.
Further, there have been known that some crepe papers with crinkle texture are used for adhesive tapes, and that the obtained adhesive tapes have a good conformability to adherend surfaces. For example, some crepe papers having a high elongation characteristic and made from natural pulps having cellulose as a base component, for example, wood pulps, hemp pulps, or linter pulps, or a mixture of the above-mentioned natural pulps and synthetic fibers have been developed (for example, see Patent Documents 4 and 5). The adhesive tapes made with such crepe paper as the backing surely satisfies the conformability to adherend surfaces, however, wrinkles of the crepe paper cause blur of the painting, and it is impossible to obtain clear painting lines.
On the other hand, in the case where tapes are required only to provide clear painting lines after removing the adhesive tape from the painted surface, some conventional adhesive tapes are useful which comprise a resinous-substance-impregnated planar paper made from natural pulps with the addition of synthetic fibers. However, such adhesive tapes have low elongation and deteriorate in the conformable feature, and therefore they have been inapplicable to curved lines.
Further, some adhesive tapes made with a plastic film as the backing have been also examined, but they have not been easy to cut by hand because of their high tear strength. Such tapes need to cut by manually pulling them against cutting tools such as blades, and it is assumed that all of these tapes deteriorate in handleability.    Patent Document 1: Japanese Laid-open Patent Publication No. 3-137292    Patent Document 2: Japanese Laid-open Patent Publication No. 7-80367    Patent Document 3: Japanese Laid-open Patent Publication No. 2004-036028    Patent Document 4: Japanese Laid-open Patent Publication No. 2002-012839    Patent Document 5: Japanese Laid-open Patent Publication No. 2002-327399