【発明の詳細な説明】
［産業上の利用分野］
本発明は、床材、壁材等の建材や家具材に用い
られる化粧板に関するものである。
［従来の技術］
従来、この種の化粧板としては、厚み１mm以上
の厚突板を台板合板に、厚突板の繊維方向が台板
合板の甲板の繊維方向と直交するように接着剤で
熱圧接着した化粧板、あるいは、突板を和紙、不
織布等の繊維状シートを介して台板合板に接着剤
で熱圧接着した化粧板などがあつた。
［発明が解決しようとする問題点］
上記従来の化粧板のサンプルをJAS規格（特殊
合板のJAS規格）の寒熱繰返し試験を適用してそ
のサンプルの耐クラツク性を試験した結果、１〜
２回の試験でクラツクの発生が認められた。これ
は、銘木単板製造時の裏割れが原因である場合、
銘木単板乾燥時の部分的な収縮ひずみ（部分的な
収縮率の差異が原因となるひずみ）等の内部ひず
みが原因である場合、基板の部分的応力集中（基
板に合板を使用した場合は、合板の導管部、放射
組織等引張応力の弱い部分に基板の動きが集中す
ること）が原因である場合などが考えられる。一
般に銘木単板が厚くなるにつれて基板の応力集中
が原因となるクラツクが多くなる。また、このク
ラツクの原因となるクラツクよりも裏割れ、内部
ひずみ等の銘木単板自体に発生するひずみが原因
となるひずみは、銘木単板厚みの２乗に比例して
大きくなるといわれている。そこで、本発明者は
銘木単板を多層構造にすれば一枚当りの銘木単板
の厚みを薄くでき、内部ひずみを極力少なくでき
るのではないかと考えた。
他方、銘木単板の裏面に和紙、不織布等の繊維
状シートを貼着してえられた化粧シートを合板表
面に熱圧着する化粧板の製造方法も既に開示され
ている。
しかしながら、緩衝材としての働きを有する上
記繊維状シートを銘木単板と合板の甲板との間に
介在させて、合板の収縮ひずみによつて銘木単板
がひずむのを緩和し、結果的に上記銘木単板のク
ラツクを防止しようという手段は十分なものでな
く、耐クラツク性に未だ問題が残つている。
［問題を解決するための手段］
本発明は上記事情に鑑みて、耐クラツク性を向
上させた化粧板を提供することを目的とするもの
であり、２枚以上の銘木単板をその繊維方向を揃
えて貼り合わせた積層化粧シートが基板表面に貼
着された化粧板において、表層の銘木単板と第２
層の銘木単板との間に繊維状シートが、その繊維
状シートの長繊維の配列方向が上記表層銘木単板
の繊維方向と直交するように介在していることを
特徴とする化粧板に係るものである。
なお、上記化粧板には下塗り塗装、上塗り塗装
等の塗装加工が施こされていてもよい。また、使
用される銘木単板はスライサーでスライスされた
単板でもロータリー単板でもどちらでもよい。ま
た、基板としては合板、パーテイクルボード、ハ
ードボード等のようなものでよく、繊維状シート
としては和紙、不織布が一般的である。
このような化粧板の製造方法としては、２枚の
銘木単板の間に繊維状シートを介在させて接着し
て積層化粧シートを予め製造し、この積層化粧シ
ートを基板表面に接着剤を介在させて熱圧接着さ
せてもよいし、基板表面に、順次銘木単板・繊維
状シート・銘木単板をそれぞれ接着剤を介在させ
て積層し、熱圧接着させてもよい。
［作用］
基板表面に銘木単板が貼着された化粧板は銘木
単板が厚い場合には銘木単板自体に発生するひず
みがクラツク発生の大きな原因となる。そこで銘
木単板を薄くしてその銘木単板を多層構造にする
ように貼り合わせ、さらに、表層の銘木単板と第
２層目の銘木単板との間に繊維状シートをその長
繊維の配列方向が表層銘木単板の繊維方向と直交
するように介在させると、クラツクの原因となる
ひずみは銘木単板厚みの２乗に比例して大きくな
るという現象を極力抑制することができる。した
がつて、クラツクの原因となる収縮ひずみを少な
くして耐クラツク性をいつそう大きく向上させる
こととなる。
［発明の効果］
従来の如く厚さ１mm以上の銘木単板を繊維状シ
ートを介在させて基板に貼着した化粧板では、そ
の表面の厚単板自体の収縮ひずみが大きく、クラ
ツクの緩衝材となつている繊維状シートの機能が
十分に果たされず、結果的に化粧板表面の耐クラ
ツク性は不十分であつたが、本発明の化粧板で
は、銘木単板を薄くしてその銘木単板を多層構造
にするように貼合させ、表層の銘木単板と第２層
目の銘木単板との間に繊維状シートをその長繊維
の配列方向が表層銘木単板の繊維方向と直交する
ように介在させるので、クラツク原因となるひず
みが銘木単板厚みの２乗に比例して大きくなると
いう現象を極力抑制することができ、耐クラツク
性をいつそう大きくさせる効果を奏する。
［実施例 １］
ナラ・ハーフロータリー単板（0.5m／ｍ厚）
に尿素・メラミン樹脂−酢酸ビニル系接着剤を60
〜80g／m2塗装後、不織布（330g／m2）を、上記
銘木単板の繊維方向と不織布の長繊維の配列方向
とが直交するように貼り合わせた。次に、この不
織布側に同じ接着剤を60〜80g／m2塗布しナラ・
ハーフロータリー単板（0.5mm厚）を載置し、熱
プレスを行なつて積層突板シートをえた。さら
に、この積層突板シートを酢酸ビニル・ウレタン
共重合樹脂接着剤を用いて合板（12mm厚）に熱プ
レスで接着した。その後、表面に透明なウレタン
塗装を施こし、所望の化粧板Ａをえた。
［比較例 １］
実施例１において、ナラ・ハーフロータリー単
板の繊維方向と不織布の長繊維の配列方向とが平
行になるようにした以外は実施例１と同様にして
化粧板Ｂを得た。
［比較例 ２］
ナラ・ハーフロータリー単板（１mm厚）を合板
（12mm厚）にその繊維方向と合板の甲板の繊維方
向とが直交するように尿素メラミン・酢酸ビニル
系接着剤を用いて熱プレスで接着した。これに透
明なウレタン塗装を施こし化粧板Ｃをえた。
［比較例 ３］
実施例１において、透明なウレタン塗装の代わ
りに透明なアミノアルキツド樹脂塗料を塗布する
以外は、実施例１と同様にして、化粧板Ｄを得
た。
［耐クラツク性試験］
以上、実施例１と比較例３つの計４つの製造方
法でえられた化粧板Ａ〜Ｄを各々５片ずつ用いて
JAS規格の寒熱繰返しＢ試験（80℃ドライヤーに
2Hr.→−20℃冷凍機に2Hr.の工程を２回繰返す）
を６回行ない、クラツクの判定を行なつた。判定
は５点法で（割れなし…５点、１〜３本の割れ…
４点、10本までの割れ…３点、20本までの割れ…
２点、20本を越える割れ…１点）で行なつた。そ
の結果を第１表に示す。
【表】DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a decorative board used for building materials such as flooring materials and wall materials, and furniture materials. [Prior art] Conventionally, this type of decorative board is made by attaching a thick veneer with a thickness of 1 mm or more to a plywood base plate and heating it with an adhesive so that the fiber direction of the thick veneer is perpendicular to the fiber direction of the deck of the base plywood. There were decorative boards that were pressure-bonded, or decorative boards that were heat-pressed and bonded a veneer to a base plywood with an adhesive through a fibrous sheet such as Japanese paper or non-woven fabric. [Problems to be solved by the invention] As a result of testing the crack resistance of the sample by applying the JAS standard (JAS standard for special plywood) cold and hot cycling test to the sample of the conventional decorative board mentioned above, it was found that the crack resistance of the sample was 1~
Cracks were observed in two tests. If this is caused by cracks on the back during manufacture of the precious wood veneer,
If the cause is internal strain such as partial shrinkage strain when drying a precious wood veneer (strain caused by differences in local shrinkage rates), local stress concentration in the board (if plywood is used as the board) , movement of the board is concentrated in areas with weak tensile stress, such as conduit parts of plywood, radial tissue, etc.). In general, as the thickness of the wood veneer increases, the number of cracks caused by stress concentration on the board increases. Furthermore, it is said that the strain caused by the strain generated in the precious wood veneer itself, such as back cracking and internal strain, increases in proportion to the square of the thickness of the precious wood veneer, rather than the crack that causes this crack. Therefore, the present inventor thought that if the precious wood veneer was made into a multilayer structure, the thickness of each precious wood veneer could be made thinner, and the internal strain could be minimized. On the other hand, a method for producing a decorative board has also been disclosed in which a decorative sheet obtained by pasting a fibrous sheet such as Japanese paper or nonwoven fabric on the back side of a precious wood veneer is thermocompression bonded to the surface of the plywood. However, by interposing the above-mentioned fibrous sheet, which acts as a buffer material, between the precious wood veneer and the plywood deck, the distortion of the precious wood veneer due to the shrinkage strain of the plywood is alleviated, and as a result, the above-mentioned Measures to prevent cracks in precious wood veneers are not sufficient, and problems with crack resistance still remain. [Means for Solving the Problem] In view of the above circumstances, the present invention aims to provide a decorative board with improved crack resistance, in which two or more precious wood veneers are aligned in the fiber direction. In a decorative board in which a laminated decorative sheet is attached to the surface of the substrate, the top layer of precious wood veneer and the second
A decorative board characterized in that a fibrous sheet is interposed between the layer of precious wood veneer so that the arrangement direction of the long fibers of the fibrous sheet is perpendicular to the fiber direction of the surface layer precious wood veneer. This is related. Note that the above-mentioned decorative board may be subjected to painting processing such as undercoating and topcoating. Furthermore, the precious wood veneer used may be either a veneer sliced with a slicer or a rotary veneer. Further, the substrate may be made of plywood, particle board, hardboard, etc., and the fibrous sheet is generally Japanese paper or nonwoven fabric. A method for producing such a decorative board is to pre-produce a laminated decorative sheet by interposing and adhering two veneers of precious wood with a fibrous sheet, and then applying this laminated decorative sheet to the surface of the substrate with an adhesive. It may be bonded by heat and pressure, or a veneer of precious wood, a fibrous sheet, and a veneer of precious wood may be sequentially laminated on the surface of the substrate with an adhesive interposed therebetween and bonded by heat and pressure. [Function] If the decorative board has a precious wood veneer stuck to the surface of the board and the precious wood veneer is thick, the strain generated in the precious wood veneer itself is a major cause of cracks. Therefore, we thinned the precious wood veneer and bonded the precious wood veneers together to form a multilayer structure, and then placed a fibrous sheet between the surface layer of the precious wood veneer and the second layer of the precious wood veneer. By interposing the fibers so that the arrangement direction is perpendicular to the fiber direction of the surface precious wood veneer, it is possible to suppress as much as possible the phenomenon that the strain that causes cracks increases in proportion to the square of the thickness of the precious wood veneer. Therefore, the shrinkage strain that causes cracks can be reduced and the crack resistance can be greatly improved. [Effect of the invention] In conventional decorative boards in which precious wood veneers with a thickness of 1 mm or more are attached to a substrate with a fibrous sheet interposed, the shrinkage strain of the thick veneer itself on the surface is large, making it difficult to use as a cushioning material. However, in the decorative laminate of the present invention, the veneer made of precious wood is made thinner, and the crack resistance of the surface of the decorative laminate is insufficient. The boards are laminated to form a multilayer structure, and a fibrous sheet is placed between the surface layer of precious wood veneer and the second layer of precious wood veneer, the direction of arrangement of the long fibers being perpendicular to the fiber direction of the surface layer of precious wood veneer. Since it is interposed in such a manner, it is possible to suppress as much as possible the phenomenon that the strain that causes cracks increases in proportion to the square of the thickness of the precious wood veneer, and has the effect of greatly increasing the crack resistance. [Example 1] Oak half rotary veneer (0.5m/m thickness)
60% of urea/melamine resin-vinyl acetate adhesive
~80 g/m 2 After painting, a non-woven fabric (330 g/m 2 ) was attached so that the fiber direction of the precious wood veneer and the arrangement direction of the long fibers of the non-woven fabric were perpendicular to each other. Next, apply 60 to 80 g/m 2 of the same adhesive to the nonwoven fabric side and
A half rotary veneer (0.5 mm thick) was placed and heat pressed to obtain a laminated veneer sheet. Furthermore, this laminated veneer sheet was bonded to plywood (12 mm thick) by hot press using a vinyl acetate/urethane copolymer resin adhesive. Thereafter, a transparent urethane coating was applied to the surface to obtain the desired decorative board A. [Comparative Example 1] Decorative board B was obtained in the same manner as in Example 1, except that the fiber direction of the oak half-rotary veneer and the arrangement direction of the long fibers of the nonwoven fabric were made parallel to each other. . [Comparative Example 2] Oak half-rotary veneer (1 mm thick) was heated to plywood (12 mm thick) using a urea-melamine/vinyl acetate adhesive so that the fiber direction of the plywood was perpendicular to the fiber direction of the plywood deck. It was attached using a press. A transparent urethane coating was applied to this to obtain decorative board C. [Comparative Example 3] Decorative board D was obtained in the same manner as in Example 1, except that a transparent aminoalkyd resin paint was applied instead of the transparent urethane paint. [Crack resistance test] As described above, five pieces each of decorative laminates A to D obtained by a total of four manufacturing methods, Example 1 and three comparative examples, were used.
JAS standard cold/heat cyclic B test (80℃ dryer)
2Hr.→Repeat the 2Hr. process twice in a -20℃ refrigerator)
was repeated 6 times to determine if it was cracked. Judgment is based on a 5-point system (no cracks...5 points, 1-3 cracks...
4 points, cracks up to 10 lines... 3 points, cracks up to 20 lines...
2 points, more than 20 cracks...1 point). The results are shown in Table 1. 【table】