BASE PAPER FOR RELEASE PAPER, AND RELEASE PAPER

PROBLEM TO BE SOLVED: To provide: a base paper for a release paper for use in a pressure sensitive adhesive sheet, which suppresses occurrence of curling when forming the pressure sensitive adhesive sheet, and has satisfactory paper feed performance and paper alignment performance during a paper discharge in an electrophotographic printer; and the release paper.SOLUTION: A base paper for a release paper is capable of forming a pressure sensitive adhesive sheet for electrophotography by laminating a surface substrate, pressure sensitive adhesive, a release agent, a base coating agent, and the base paper for the release paper. A fiber orientation ratio of the base paper for the release paper to be measured by a supersonic propagation speed measuring device is 1.45-1.70, and a moisture content of paper is 4.5-7.5 mass%. A degree of elasticity of the base paper for the release paper in a width direction of paper to be measured by the supersonic propagation speed measuring device is not more than 4.50 GPa. 【課題】粘着シートを構成した場合に、カールの発生が抑制され、電子写真式プリンターでの給紙性や排紙時の紙揃え性が良好な粘着シート用の剥離紙用原紙および剥離紙を提供する。【解決手段】表面基材、粘着剤、剥離剤、下塗り剤、剥離紙用原紙を積層して電子写真用粘着シートを構成し得る剥離紙用原紙であって、前記剥離紙用原紙の超音波伝播速度測定器により測定される繊維配向比が１．４５〜１．７０であり、かつ紙水分が４．５〜７．５質量％である剥離紙用原紙である。また、剥離紙用原紙の超音波伝播速度測定器により測定される紙の横目方向の弾性率が４．５０ＧＰａ以下である剥離紙用原紙である。【選択図】なし