Prepreg and method of manufacturing the prepreg

1. A method of producing a prepreg comprising:

impregnating a reinforced-fiber sheet with a matrix resin so as to have a continuous resin layer at least in an inside thereof

applying a protective film having an irregular surface to at least one surface of one side of the reinforced-fiber sheet impregnated with the matrix resin to form a sea-island structure comprising a resin-impregnated part where an impregnated resin substantially exists and a fiber part where an impregnated resin does not substantially exist on the at least one surface of the impregnated reinforced fiber sheet; and,

and keeping a temperature at 50 to 130° C. for 4 hours or more in a situation where the protective film is applied to the reinforced-fiber sheet and keeping the viscosity of an impregnated resin at 100 to 10000 Poise or less for 4 hours or more in a situation where the protective film is applied to the reinforced-fiber sheet to distinctly form a resin-impregnated part where an impregnated resin substantially exists and a fiber part where an impregnated resin does not substantially exist on the at least one surface of one side of the reinforced-fiber sheet impregnated with the matrix resin.

2. The method of producing the prepreg according to claim 1 , wherein only a convex portion of the irregular surface is brought into contact with the reinforced-fiber sheet impregnated with the matrix resin.

3. The method of producing the prepreg according to claim 1 , wherein the irregular surface of the protective film is formed of a number of independent convex portions.

4. The method of producing the prepreg according to claim 3 , wherein the irregular surface of the protective film is disposed with dispersing a number of convex portions uniformly on a surface of the film.

5. The method of producing the prepreg according to claim 4 wherein a center distance between the adjacent convex portions is 1 to 10 mm.

6. The method of producing the prepreg according to claim 3 wherein a center distance between the adjacent convex portions is 1 to 10 mm.

7. A method of producing a curable prepreg, comprising:

impregnating a reinforced-fiber sheet with a matrix resin so as to have a continuous resin layer at least in an inside thereof;

applying a protective film having an irregular surface to at least one surface of the impregnated reinforced fiber sheet to form a sea-island structure comprising a resin impregnated part where an impregnated resin substantially exists and a fiber part where an impregnated resin does not substantially exist on the at least one surface of the impregnated reinforced fiber sheet; and,

keeping the temperature of the protected impregnated reinforced-fiber sheet at 50 to 130° C. for 4 hours or more and keeping the viscosity of the matrix resin impregnated in the reinforced-fiber sheet at 100 to 10,000 Poise or less for 4 hours or more in a situation where the protective film is applied to the reinforced-fiber sheet so as to distinctly form a resin-impregnated part where an impregnated resin substantially exists and a fiber art where an impregnated resin does not substantially exist on the at least one surface of one side of the reinforced-fiber sheet impregnated with the matrix resin distinctly.

8. The method of producing the curable prepreg according to claim 7 , wherein only a convex portion of the irregular surface is brought into contact with the reinforced-fiber sheet impregnated with the matrix resin during the applying.

9. The method of producing the curable prepreg according to claim 7 , wherein the irregular surface of the protective film has a plurality of independent convex portions.

10. The method of producing the curable prepreg according to claim 9 , wherein the irregular surface of the protective film is disposed with dispersing a number of convex portions uniformly on a surface of the film.

11. The method of producing the curable prepreg according to claim 9 wherein a center distance between the adjacent convex portions is 1 to 10 mm.