Deep-colored fibers and a process for manufacturing the same

A deep-colored fiber having on its surface a film coating of a resin mixture comprising at least two kinds of resins that are incompatible with each other and are in phase-separated condition in said film coating, said two kinds of resins being different in solvent-solubility and wherein, on at least a part of the surface of the film coating, pits and/or recesses and projections are formed by elution of at least one kind of resin that is higher in solvent-solubility.

A deep-colored fiber having its surface coated with a film coating essentially of a mechanical blend of at least two different kinds of synthetic resins A and B, said resins A and B being incompatible with each other and existing as separate phases in said film, both of said resins A and B being substantially transparent, film-forming resins which are dispersible in water and miscible with each other, the amount of said film being from 0.2 to 15 % by weight, based on the weight of the fiber, the weight ratio of (resin A/resin B) in said film being in the range of from (90/10) to (10/90,) said resin A having an index of refraction n.sub.A in the range of from 1.35 to 1.50, said resin B having an index of refraction n.sub.B in the range of 1.40 to 1.60, and wherein n.sub.B is higher than n.sub.A, n.sub.A is lower than the index of refraction n.sub.O of the fiber and resin A has a lower affinity for the fiber than resin B.

A deep-colored fiber having its surface coated with a pitted resinous coating obtained by treating (1) a film coating consisting essentially of a mechanical blend of at least one synthetic resin A and a material B, which material B is selected from the group consisting of water-soluble macromolecular materials and organic solvent-soluble synthetic resins, with (2) a solvent effective to dissolve material B to form pits in said film coating, said resin A and material B being incompatible with each other and existing as separate phases in said film coating, said resin A being a substantially transparent, film-forming resin, the ratio of the solvent solubilities of resin A/resin B being from (1/2) to (1/10,)said resin A being lower in refractive index than material B, the amount of said film coating being from 0.2 to 10 % by weight, based on the weight of said fiber, the weight ratio of (resin A/material B) in said film coating being in the range of from (80/20) to (50/50,) the ratio of the sum of the areas of the pits in said pitted coating to the surface area of said pitted coating being from (5/100) to (50/100,) the number of pits per unit area of said pitted coating being from 1 to 30 pits/.mu.m.sup.2, said pits having acute angled edges and being undercut when viewed in cross-section.

A deep-colored fiber having its surface coated with a pitted resinous film coating obtained by treating (1) a film layer consisting essentially of a mechanical blend of at least two different kinds of synthetic resins A and B, with (2) plasma etching effective to form pits in said film layer, said resins A and B being incompatible with each other and existing as separate phases in said film layer, the ratio of the etching ratio of (resin B/resin A) being at least 1.5, said resin A being a transparent, film-forming resin and having a lower index of refraction than resin B, the amount of said film layer being from 0.2 to 10% by weight, based on the weight of said fiber, the weight ratio of (resin A/resin B) being in the range of from (90/10) to (30/70,) said pits having acute angled edges and being undercut when viewed in cross-section.