US3676183A

US3676183A - Process for preparing high gloss photographic paper

Info

Publication number: US3676183A
Application number: US51358A
Authority: US
Inventors: Leonid G Garth
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1970-06-30
Filing date: 1970-06-30
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11

Abstract

PHOTOGRAPHIC PAPER BASE IS COATED WITH A MIXTURE OF GELATIN, BARIUM SULFATE AND A GELATIN HARDENER, DRIED, COATED WITH AN ALKALINE GELATIN SOLUTION, DRIED, SPRAYED WITH AN ALKALINE FORMALDEHYDE SOLUTION AND DRIED IN CONTACT WITH A HIGHLY POLISHED HEATER METAL DRUM TO OBTAIN A HIGH GLOSS FINISH.

Description

Patented July 11, 1972 PROCESS FOR PREPARING HIGH GLOSS PHOTOGRAPHIC PAPER Leonid G. Garth, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, NY. No Drawing. Filed June 30, 1970, Ser. No. 51,358 Int. Cl. B44d 1/44; G03c 1/30 US. Cl. 11764 R 2 Claims ABSTRACT OF THE DISCLOSURE Photographic paper base is coated with a mixture of gelatin, barium sulfate and a gelatin hardener, dried, coated with an alkaline gelatin solution, dried, sprayed with an alkaline formaldehyde solution and dried in contact with a highly polished heated metal drum to obtain a high gloss finish.

This invention relates to a process for the preparation of a photographic paper base having a high gloss surface.

It is well known in the art to prepare photographic paper base by applying a mixture of baryta (barium sulfate), gelatin and gelatin hardening agent such as formaldehyde to a paper surface followed by drying and calendering the paper to obtain a relatively high gloss finish on the baryta coated surface. A gelatin-silver halide emulsion layer, or layers, is coated on the surface and photographic prints are prepared by exposing and developing the emulsion layer, washing, drying, etc., as well known in the art. However, the resultant processed paper ordinarily must be ferrotyped, i.e. dried in contact with a smooth surface if the photographic prints are to have a very glossy surface.

I have discovered a process for preparing baryta coated photographic paper base which provides a permanent glossy surface to the paper and does not require the processed paper to be ferrotyped, i.e. the paper can be dried out of contact with a smooth surface and still obtain a glossy surface on the prints.

According to the process of the invention, ordinary photographic paper base in (a) coated with a gelatinbaryta layer preferably containing a gelatin hardener such as formaldehyde and dried. Thereafter, (b) an aqueous alkaline gelatin solution is coated onto the baryta layer and dried after which (c) the resultant gelatin coated surface is treated with an alkaline aqueous formaldehyde solution followed by drying the surface in contact with a smooth heated surface such as a metal drum. The resultant surface is then coated with one or more photographic emulsion layers and after exposure and processing of the element in a well known manner, it is found that the pictures obtained thereon have a very high gloss finish and it is not necessary to ferrotype the surface to obtain the desired degree of gloss.

A similar process is described by Swiss Pat. 387,433 wherein a pigment-adhesive coated paper is treated with aqueous formaldehyde solution followed by drying the coating in contact with a hot metal surafce. The patent does not suggest using the above steps (b) and (c) of the present invention which are necessary for production of a relatively permanent glossy surface. In step (b) of the present process, the pH of the alkaline gelatin solution should be about 10.5 to 12.0 for best results. The gelatin solution is coated so as to obtain about 1 to 6 grams gelatin, preferably 2 grams of gelatin per square meter of coating surface. In step (c) the formaldehyde solution should have a pH of about 11 to 12.5 or higher, preferably 11.5. A dilute aqueous formaldehyde solution of, for example, 4% formaldehyde can be used for this purpose. Sufiicient formaldehyde is used to obtain a glossy surface and yet not so little that the surface sticks to a heated metal surface when drying at a temperature of about C. for about 10 seconds. Higher or lower drying temperatures can be used With suitable adjustment of drying time, i.e. drying longer at lower temperatures.

The following example will serve to illustrate the invention.

EXAMPLE A paper stock comprising aluminum stearate sized paper fiber is coated with an aqueous mixture of gelatin and baryta containing 1 pound gelatin, 10 pounds barium sulfate, and formaldehyde hardener to obtain 20 grams of coating per square meter (dry weight). After drying, a second coating of an aqueous alkaline gelatin solution pH 10.5 is applied to the baryta coated paper surface to obtain 2 grams gelatin per square meter (dry weight) followed by drying. Thereafter, a 4% aqueous formaldehyde solution pH 11.5 is sprayed onto the coated surface which is then dried for nine seconds in contact with a polished metal drum heated to 190 F. The dried surface having a high gloss is then coated with a gelatinsilver halide emulsion layer and dried. The resultant lightsensitive photographic paper is exposed, developed, fixed, Washed and dried with the emulsion surface exposed to the air, i.e. without ferrotyping. As a result, the surface of the process prints has a very high gloss.

When the same process is carried out in the manner of the Swiss Pat. 387,443, but omitting the alkaline gelatin coating step, only a medium glossy surface is obtained on the prints.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

What I claim is:

1 A process for preparing a photographic paper base having a high gloss surface comprising (a) coating a paper sheet with an aqueous mixture of barium sulfate, gelatin and gelatin hardener and drying the coating,

(b) applying to the dried coating an aqueous alkaline gelatin solution and drying the resultant coating,

(0) treating the resultant coating with an alkaline aqueous solution of formaldehyde,

(d) and drying the resultant coating in contact with a highly polished heated surface.

2. The process of claim 1 wherein the aqueous gelatin solution has a pH of about 10.5 to 12.0 and is applied so as to obtain about 2 grams of gelatin per square meter of coating surface and the pH of the formaldehyde solution is about 11.0 to 12.5.

References Cited UNITED STATES PATENTS 2,756,150 7/1956 Griggs et al. W 117-34 2,121,205 6/l938 Lippert et al. ll7-34 2,780,560 2/1957 Hanley ll734 2,678,890 5/1954 Leighton 1l764 R 3,288,775 1 H1966 Anderau et a1 117-34 FOREIGN PATENTS 387,433 Switzerland lI7-34 1,438,244 France.

WILLIAM D. MARTIN, Primary Examiner W. R. TRENOR, Assistant Examiner US. Cl. X.R.

ll7--34, 81, I56; 96--lll