US2184289A - Photographic and printing media - Google Patents

Description

Patented Dec. 26, 1939 PATENT OFFICE PHOTOGRAPHIO AND PRINTING MEDIA Charles Dangelmajer, Niagara Falls, N. Y., as-

signor to E. I. du Pont de Ncmours & Company,

Wilmington,

Del., a corporation of Delaware No Drawing. Application June 16, 1937, Serial No. 148,587

16 Claims.

This invention relates to photographic and printing media. More particularly, it relates to improved light-sensitive compositions and to films, printing surfaces and the like formed 5 therefrom, which are adapted to be used in a variety of photographic and printing processes.

Theinvention will be described with particular reference to photolithographic printing processes wherein the improved media of the invention possess exceptional utility.

The photolithographic processes now in general use involve printing from a photolithographic plate which comprises essentially a zinc or aluminum plate, on the surface of which the 15 design portions have been rendered receptive to the printing ink while the other portions are nonink-receptive. In the direct printing process, the plate is usually mounted upon a roller which is revolved in contact with two other roll- 20 ers. One of the latter wets the hydrophilic portions of the plate with an aqueous fountain solution; the other roller carries the oily printing ink and applies it to the hydrophobic surfaces of the plate which compose the design.

25 The inked plate is then contacted with the paper or other material to be printed. In the ofifset printing process, a similar procedure is employed except that the design is first transferred from the lithographic plate to a rubber roller, thence 30 from the latter to the surface to be printed.

The photolithographic plates used heretofore have usually consisted of a zinc or aluminum plate coated with albumen or gelatine, with which is incorporated a light-sensitive agent,

35 such as a dichromate, which is capable of cansing hardening of the albumen or gelatine upon exposure to light. To produce the image upon such a plate, it is exposed to ultra-violet light under a photographic negative until photo- 40 graphic hardening of the exposed portions of the light-sensitive film is effected; the plate is then developed by washing with warm water, to remove the soluble portions of the film. Generally, a so-called "developing ink is applied to the 45 plate prior to the washing operation in order to insure that the insoluble portions, which define the image to be printed, will be receptive to the oily printing inks used.

Recently it has been proposed to replace the 50 gelatine or albumen used heretofore as a basis for light-sensitive layers with polyvinyl alcohol. The latter material has the advantage that its properties can be controlled more precisely than those of natural products like gelatine and albu- 55 men; also polyvinyl alcohol films possess greater mechanical strength and durability than those formed from gelatine oralbumen. However, certain difliculties have been encountered in the practical utilization of polyvinyl alcohol films in photolithographic plates, one of the most'important of which is the fact that they tend to lose their properties of ink receptivity after relatively short periods of use. The loss of ink receptivity is especially pronounced when used polyvinyl alcohol plates are cleaned with 501- vents such as gasoline or turpentine. After such treatment it is usually impossible to restore the ink receptivity of the polyvinyl alcohol film.

It is, accordingly, an object of the present in-' vention to provide improved light-sensitive compositions adapted to be used for the production of printing surfaces and for general photographic purposes. It is a further object of the invention to provide printing mediav characterized by a high degree of ink-receptivity, durability and resistance to the action of water and acids. Other objects will be apparent from the ensuing description of the invention. I '1 ,j

The foregoing and related objects are] acco plished by the incorporation in polyvinyl Qal'c hol compositions utilized for preparlngpl'i I graphic plates and other printing and photographic media of organic sulfonyl compounds 'I have found that films formed from such compo: sitions possess an ink receptivity markedly superior to that of the usual polyvinyl alcohol films; that at the same time the new compositions have greater durability and resistance to the action of water, acids and fountain solutions"; and that, in general, the modified polyvinyl alcohol compositions of the invention are superior to unmodified polyvinyl alcohol for practically all printing and photographic purposes. 40

In accordance with the invention, compositions suitable for preparing light-sensitive coatings on photolithographic and other printing surfaces and for the preparation of light-sensitive emulsions on photographic films and plates may be prepared by dissolving or dispersing an organic sulfonyl compound, together with polyvinyl alcohol and a light-sensitizing agent, in water or other suitable solvent or, dispersing medium. The resultant solutions or dispersions may be applied to a suitable support, for example, in the case of lithographic plates, to'a zinc or aluminum plate, and the solvent removed by evaporation. the plate and its subsequent development and The production of the image on material which is usually obtained by the hy-- drolysis of polymerized vinyl esters, such as polyvinyl acetate. Polyvinyl alcohol can be made in a number of modifications of different degrees of polymerization, the degree of polymerization depending largely upon the extent to which the polyvinyl compound from which it is derived has been polymerized. All of these modifications of polyvinyl alcohol are, to some extent, soluble in water. The more highly polymerized forms are less soluble and produce solutions of higher viscosities for equal concentrations than the lower polymers. There are also a number of the socalled partial derivatives of polyvinyl alcohol in which some of the hydroxyl groups in the molecule are replaced by other radicals, such as ester, ether or acetal radicals. Such partial derivatives may be produced by the incomplete saponiflcation of vinyl esters or by the incomplete reaction of polyvinyl alcohol with acids, aldehydes or other compounds which react with hydroxyl groups. As would be expected, the properties of the partial derivatives of polyvinyl alcohol vary in accordance with the proportion of hydroxyl radicals that have been substituted for other groups. When the hydroxyl radicals substantiallypredominate, the partial derivatives show essentially the properties of polyvinyl alcohol and, like pure polyvinyl alcohol, are soluble in water as distinguished from the esters, acetals,

etc., which are soluble only in organic solvents. Accordingly, the term polyvinyl alcohol is used herein and in the appended claims to designate generically all of the foregoing modifications of polyvinyl alcohol including such partial. derivatives thereof as contain a sufllcient, number .of

unsubstituted hydroxyl groups as to render-the compounds soluble in water.

As the viscosity of a solution 'of polyvinyl alcohol of given concentration is a function of its degree of polymerization, I refer hereinto the various polymers in terms of viscosity. it is to be understood that all suchreferenc'es designatethe viscosity of a 4% aqueous solution of the polyvinyl alcohol at a temperature of 20 C.-

A wide range of polyvinyl alcohol polymers are adapted for use inthe compositions of the present invention. Thus, depending upon the particular purpose'for which the compositions are to be used, polyvinyl alcohol polymers having a viscosity of from-about 2 to about 'centipoises may be used. In general, the lower polymers are more sensitive to slight diflerences in light intensity, but are'somewhat less resistant to water than the higher polymers. The higher polymers form somewhat more durable printing surfaces. In certain cases it has been found desirable to utilize mixtures. of' high polymers and low polymers.

The sulfonyl compounds suitable 'for modify;

ing the characteristics of polyvinyl alcohol in accordance with the invention include'all organic compounds containing the characteristic sulfonyl (-SOz group. In the case of compounds; which are not normally water-soluble, it is advan- I tageous to utilize them in the form of their water-soluble salts, e. g., as ammonium oralkali metal salts. It is not necessary, however,- that the sulfonyl compounds be dissolved in the composition, as satisfactory results may also be obtained by forming dispersions of t e cids in the polyvinyl alcohol compositions. Sulfonyl compounds suitable for modifying the polyvinyl alcohol compositions, in accordance with the invention, include: organic sulfates, especial"! those formed by the reaction of sulfuric acid with higher aliphatic alcohols, such as hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, cetyl, octadecyl, and octadecenyl sulfates; sulfonic acids such as benzene sulfonic acid, orthanilic acid, metanilic acid. sulfanilic acid, phenol sulfonic acids, toluene sulfonic acids, toluidine sulfonic acids, naphthalene sulfonic acids, naphlimits, depending upon the purpose for which the composition is to be used and the result which it is desired to obtain. In general, the amount of sulfonyl compound may range from about 0.3% to 20% of the weight of the polyvinyl alcohol contained in the composition and will generally be within the limits of 1% to 8%.

The agents used torender the compositions light-sensitive may be any of those which have been used heretofore for similar purposes in gelatine or albumen films. For the preparation of photolithographic plates and for similar printing purposes, the preferred sensitizing agents are soluble chromium salts, such as, for example, ammonium dichromate or alkali metal dichromates. For the preparation of. photographic emulsions, silver-salts, especially silver halides,

light-sensitive dyes and other sensitizing agents such as are well known in the photographic art may be employed.

-' The following examples are illustrative of cer- 'tain specific embodiments of the invention:

Example 1 Afcomposition was prepared from the followingingre'dients: Parts by weight lPolyvinyl alcohol (a polymer having a viscosity of 22130 24 centipoises in 4% aqueous solution at 20 C) Ammonium dichromate lb-Naphthalene disulfonic acid 0.15 *Water 95.5

polyvinyl alcohol was dissolved in 50 parts of "water and tothis solution was added the naphthalene'disulfonic acid dissolved-in 3 parts of water. The ammonium dichromate, dissolved in the remainder of the water, was then added with stirring.

A zinc lithographic plate was coated with this solution, dried, and exposed to ultra-violet light under a photographic negative. plate was coated with developing ink and developed by washing with water at a temperature of -35 to 40 C. The developed print was then coated with the usual gum solution (an aqueous solution containing gum arabic with small amounts of phosphoric and gallic' acids). The plate was then ready for use in the lithographicprinting press.

The exposed iormly receptive to the lithographic ink and retains such ink receptivity after long periods of use, even after having been washed with turpentine, gasoline or other solvents. The film possesses water-resistance superior to that of films made from unmodified polyvinyl alcohol. If desired, however, the water-resistance may be still further increased by heating the developed plate to a temperature of 80-120 C. for a period of 5 minutes to one-half hour.

Example 2 Parts by weight Polyvinyl alcohol (same polymer as in Example 1) 3.0

2-Naphthlyamine-l-sulfonic acid 0.09

Ammonium dichromate 1.5 Water 95.5

The solution was prepared and applied to the lithographic plate in the same manner as in Example 1.

Example 3 Parts by weight Polyvinyl alcohol (same polymer as in Example 1) 3.0

Saccharim 0.15 Ammonium dichromate 1.5 Water 95.5

ample 1) 3.0

Sodium dodecyl sulfate 0.06 Ammonium dichromate 1.5 Water 95.5

The solution was prepared and applied to the lithographic plate in the same manner as in Example 1.

In certain instances the polyvinyl alcohol compositions of the invention can be combined with compositions used heretofore as a basis for lightsensitive films, such as albumen, gelatine, glue, gum arabic and the like. For special applications, dyes, pigments and filling agents of various kinds may be added to the compositions.

While the invention has been described primarily from the standpoint of the production of improved photolithcgraphic plates, it is to be understood that the utility of the compositions of the invention is not restricted to photolithography or similar processes. They may be used advantageously in substantially all printing and photographic arts wherein gelatine or albumen compositions have been used heretofore. They are suitable for both positive and negative printing processes, whether the films be utilized as inkreceptive printing surfaces or as etching masks. The compositions may be used advantageously for coating paper or fabrics to produce carbon tissues such as are commonly utilized in intaglio 5 printing and in certain types of photographc finishing. Another application of the compositions is in the photographic production of mesh stencils of the type where a photosensitive mater'al is utilized as a mask for the non-design portions of the stencil. The compositions of the invention may also be utilized as emulsion coatings for photographic films and plates, both posit've and negative.

Printing plates prepared from the compositions of the invention are characterized by improved qualities of ink receptivity, and by the retention of such ink receptivity even after long continued use and after treatment with solvents. They are also considerably more resistant both to water and to acids than films prepared from unmodified 5 polyvinyl alcohol and are characterized by greater durability and superior printing qualities.

It is to be understood that the invent'on is not restricted to any of the specific embodiments described hereinabove but includes all such varia- 10 tions, modifications and equivalents as fall within the scope of the appended claims.

I claim:

1. A l ght sensitive layer comprising polyvinyl alcohol, a material adapted to photochemically 15 harden said polyvinyl alcohol and 0.3% to 20% of an organic sulfonyl compound.

2. A light sensitive layer comprising polyvinyl alcohol, 0.3% to 20% of an organic sulfonyl compound and a water soluble dichromate in light sensitizing amount.

3. A light sensitive layer comprising polyvinyl alcohol, 0.3% to 20% of a water soluble salt of an organic sulfonyl compound and a material adapted to photochemically harden said polyvinyl alcohol.

4. A composition comprising polyvinyl alcohol, 0.3% to 20% of 1.5-naphthalene disulfonic acid and a material adapted to photochemically harden said polyvinyl alcohol. 30

5. A composition comprising polyvinyl alcohol, 0.3% to 20% of 1,5-naphthalene disulfon c acid and a water soluble dichromate in light sensitizing amount.

6. A composition comprising polyvinyl alcohol, 35 0.3% to 20% of a salt of dodecyl sulfate and a light sensitizing agent.

'7. A composition comprising polyvinyl alcohol, 0.3% to 20% of a salt of dodecyl sulfate and a water soluble dichromate in light sensitizing 40 amount.

8. A printing device having on its printing surfaces ink receptive design port ons, said ink receptive portions comprising photochemically hardened polyvinyl alcohol and 0.3% to 20% of 5 an organic sulfonyl compound.

9. A printing device having on its printing surfaces ink receptive design portions, said ink receptive portions comprising photochemically hardened polyvinyl alcohol and 0.3% to 20% of 50 1,5-naphthalene disulfonic acid.

10. A printing device having on its printing surfaces ink receptive design portions, said ink receptive portions comprising photochemically hardened polyvinyl alcohol and 0.3% to 20% of 66 a salt of dodecyl sulfate.

11. A method of producing a photographic or printing device which comprises forming a film comprising polyvinyl alcohol, a material adapted to photochemically harden said polyvinyl alcohol, and 0.3% to 20% of an organic sulfonyl compound, and selectively exposing said film to light.

12. A method of producing a photographic or printing device which comprises formng a film comprising polyvinyl alcohol, a material adapted to photochemically harden said polyvinyl alcohol, and 0.3% to 20% of an organic sulfonyl compound, selectively exposing said film to light and developing the exposed film to remove non-exposed por- 70 tions thereof.

13. A method of producing a photographic or printing device which comprises forming a film comprising polyvinyl alcohol, a material adapted to photochemically harden said polyvinyl alcohol, 75

to photochemically harden said polyvinyl alcohol, and 0.3% to 20% of a salt of dodecyl sulfate, and selectively exposing said film to light.

16. A method of producing a photographic or printing device which comprises forming a film comprising polyvinyl alcohol, a material adapted to photochemically harden said polyvinyl alcohol, and 0.3% to 20 %**,of a salt of dodecyl sulfate, selectively exposing said film to light and developing the exposed film to remove non-exposed portions 10 thereof.

- CHARLES DANGELMAJER.