Plate-like composite material containing polytetrafluoroethylene and filler

A plate-like composite product, comprising:

• polytetrafluoroethylene;
• and
• a filler,
• wherein the polytetrafluoroethylene is fibrillated,
• wherein the filler contains porous inorganic fine particle aggregates each formed by aggregation of inorganic fine particles having an average primary particle diameter of from 5 nm to 200 nm,
• wherein the composite material has a porosity of 35% or more,
• wherein the composite material has a critical liquid-repellent tension determined by a wetting tension test of 34.0 mN/m or less,
• wherein, in the wetting tension test, a test object is immersed in each of test mixtures, which correspond to test mixtures described in JIS K 6768:1999 of Japan Industrial Standards, and which have wetting tensions at 23° C. of 22.6 mN/m, 25.4 mN/m, 27.3 mN/m, 30.0 mN/m, 31.0 mN/m, 32.0 mN/m, 33.0 mN/m, 34.0 mN/m, 35.0 mN/m, 36.0 mN/m, 37.0 mN/m, 38.0 mN/m, 39.0 mN/m, 40.0 mN/m, 41.0 mN/m, 42.0 mN/m, 43.0 mN/m, 44.0 mN/m, 45.0 mN/m, 46.0 mN/m, 48.0 mN/m, and 50.0 mN/m, at 25° C. for 1 minute to confirm whether or not each of the test mixtures permeates the test object, and a numerical value of a wetting tension of a test mixture having the smallest wetting tension out of the test mixtures that have not permeated the test object is determined to be a critical liquid-repellent tension of the test object, and
• wherein a surface of the filler is modified by a surface modifier having a hydrophobic group or by forming a fine structure on the surface of the filler.