| 摘要 |
PURPOSE: To form a main coat which is homegeneous in a thickness direction by a method wherein polyimide resin varnish of which logarithmic viscosity is within a specific range is used in order to form a main coat when a plurality of layers of polyimide laminate are applied to a required base material by using varnish by a cast method. CONSTITUTION: When a composite board 10 wherein a plurality of layers of polyimide resin laminate is provided to a base material 1 by a cast method is manufactured, high viscous polyimide resin varnish of 1.0-4.0dl/g logarithmic viscosity, preferably 1.2-3.0dl/g is used to form a main coat 3. The logarithmic viscosity is shown by a value calculated by formula: logarithmic viscosity = log (η/η0 )/C, wherein,ηis viscosity measured at 36 deg.C of a solution wherein 0.5g of polyamic acid is dissolved in 100ml of solvent, N,N-dimethylacetamide.η0 is viscosity measured at 35 deg.C of the solvent. C is concentration of polymer solution expressed by (g) of polyamic acid in 100ml of the solvent. |
