1. Field of the Invention
The present invention relates to a wood board, a surface-decorated wood board, and a manufacturing method therefor, and in particular relates to wood boards, in which the surface of an oriented strand board in a laminated wood board, in which an oriented strand board is laminated to a strand board, has improved smoothness, and improved resistance to water and moisture, as well as to a manufacturing method therefor, and additionally, to a surface-decorated wood board which employs this wood board.
2. Background Art
In recent years, the felling of forests has been restricted, and it has become difficult to obtain lumber resources, and in connection therewith, the supply of plywood and the like which consumes large amounts of lumber resources has become uncertain, and furthermore, the price thereof has tended to rise, so that a substitute product has been in demand. From this point of view, oriented strand boards which can be produced from waste materials and which, moreover, possess strength which is comparable to that of plywood produced from coniferous trees or broadleaf trees, have attracted attention.
Oriented strand boards, which may be abbreviated to "OSB", are wood boards in which thin wooden strands having a thickness within a range of 0.2.about.2 mm are arranged in essentially a single direction, are collected so that the direction of the ligneous fibers thereof is essentially identical, and these are then molded into an integral structure by means of a binder such a s a phenol resin or the like; such boards have come to be employed as roofs, walls, floors, or foundation materials for dwellings.
However, such oriented strand boards are produced by collecting comparatively thick wooden strands, generally having a thickness of 0.8 mm, so that the surface irregularities thereof are severe, and furthermore, the characteristic wooden strand pattern appears, and it is generally difficult to employ such boards as surface layer materials. Furthermore, even if a decorative veneer or a decorative polyvinyl chloride sheet or the like is applied to the surface of such an oriented strand board as a decorative material, large irregularities are present in the surface, so that spaces are formed in the cavities thereof and adhesion is insufficient, and furthermore, the texture appears in the surface of the decorative material, so that various procedures are necessary, such as the smoothing of the surface by sanding, before such an application. Furthermore, even if such procedures are carried out, if the surface decorative material is thin, the wooden strand pattern will be visible through the surface, so that there are problems in that the design thereof is adversely affected. In addition, oriented strand boards generally tend to absorb moisture easily, so that in atmospheres of high humidity, when the oriented strand board absorbs moisture, the dimensional differences between the oriented strand board and the surface decorative material become large, and there is a danger that twisting, peeling, or the like will occur, and furthermore, the surface irregularities may be increased.
For this reason, conventionally, a three-layered structure was employed using an oriented strand board as a core layer, and laminating, for example, medium fiber board having superior surface smoothness to both surfaces thereof. Therefore, even though the oriented strand board was advantageous in terms of the resources consumed, the surface irregularities and the wooden strand pattern thereof hindered the broader use of such oriented strand boards.