| abstract |
To provide a fiber sheet having high strength, excellent dimensional stability, and heat stability. A fiber sheet containing polyethylene naphthalate fibers, wherein the polyethylene naphthalate fibers have a crystal volume of 550 to 1200 nm 3 obtained by X-ray wide-angle diffraction and a crystallinity of 30 to 60%. A fiber sheet characterized by that. Furthermore, the polyethylene naphthalate fiber contains 0.1 to 300 mmol% of phosphorus atoms with respect to the ethylene naphthalate unit, or the polyethylene naphthalate fiber contains a metal element, The metal element is at least one metal element selected from the group consisting of 4th to 5th period and 3-12 group metal element and Mg in the periodic table, and the melting point of the polyethylene naphthalate fiber is 285 to 315 ° C. It is preferable that [Selection figure] None |