Lithographic printing plate
AssigneeAllied Paper Incorporated
InventorMichael J. Shaw
Life of this patent
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Abstract
The desirable attributes of both a barrier coat and a face coat and elimination of a coating step are obtained in manufacture of a lithographic printing plate having a paper base and a lithographic printing surface thereon, wherein said surface comprises a coating of positively charged colloidal silica and insolubilized hydrophilic polymer, by including in said coating non-flocculating pigment and resinous binder that is cationic or nonionic or mixed cationic and nonionic.
Claims12
In a lithographic printing plate having a paper base and a lithographic printing surface thereon comprising a face coating of positively charged colloidal silica and insolubilized hydrophilic polymer, in the ratio by weight of about two parts silica:one part polymer to about six parts silica:one part polymer, the improvement for reduction or elimination of a barrier coat on said base which comprises including in the face coating from about 10% to about 60% by weight of a fine particle size pigment which is non-flocculating and about 5% to about 30% by weight of a resinous binder which is cationic, nonionic or mixed cationic and nonionic, the hydrophilic polymer comprising about 5% to about 25% of the face coating and the positively charged colloidal silica comprising about 10% to about 70% by weight of the face coating, said weight percents being based on the dried lithographic printing surface coating free of volatiles.
A method of making a lithographic printing plate which comprises forming an aqueous coating composition comprising an insolubilized hydrophilic polymer, a positively charged colloidal silica, a fine particle size pigment which is nonflocculating, and a resinous binder which is cationic, nonionic or mixed cationic and nonionic, the coating composition having the following approximate proportions by weight:
- positively charged colloidal silica:
- about 10-70%
- insolubilized hydrophilic polymer:
- about 5-25%
- non-flocculating pigment:
- about 10-60%
- resinous binder:
- about 5-30% the ratio of colloidal silica to insolubilized hydrophilic polymer being in the range of about 2:1 to about 6:1;
- applying said coating composition to a paper base;
- and drying the coating composition on said paper base.
A method of making a lithographic printing plate which comprises forming an aqueous coating composition comprising an insolubilized hydrophilic polymer, a positively charged colloidal silica, a fine particle size pigment which is non-flocculating, and a resinous binder which is cationic, nonionic or mixed cationic and nonionic, the coating composition having the following approximate proportions by weight:
- positively charged colloidal silica:
- about 30-50%
- insolubilized hydrophilic polymer:
- about 10-20%
- non-flocculating pigment:
- about 30-50%
- resinous binder:
- about 10-20% the ratio of colloidal silica to insolubilized hydrophilic polymer being in the range of about 3:1 to about 5:1;
- applying said coating composition to a paper base;
- and drying the coating composition on said paper base.
Dependencies are inferred from the claim text.