to paper base material and represented by the following formula 1 is used r 1 r 2 n si or 3 3 u2212 n 1 in the formula 1 r 1 represents an alkyl amino group having primary amine at the terminal ends r 2 and r 3 respectively independently represent an alkyl group having 1 to 3 carbon atoms and n represents an integer of 0 or 1 concretely for aminosilane having three alkoxy groups in one molecule 3 aminopropyltrimethoxysilane 3 aminopropyltriethoxysilane n 2 aminoethyl 3 aminopropyltrimethoxysilane and others can be given and one type or two or more types of mixture of these can be used for aminosilane having two alkoxy groups in one molecule 3 aminopropylmethyldimethoxysilane 3 aminopropylmethyldietoxysilane n 2 aminoethyl 3 aminopropylmethyldimethoxysilane n 2 aminoethyl 3 aminopropylmethyldiethoxysilane and others can be given and one type or two or more types of mixture of these can be used only aminosilane having three alkoxy groups in one molecule n 0 may be also used or the mixture of aminosilane having three alkoxy groups in one molecule n 0 and aminosilane having two alkoxy groups in one molecule n 1 may be also used it is desirable that minosilane having three alkoxy groups in one molecule.