US2312852A

US2312852A - Light-sensitive element

Info

Publication number: US2312852A
Application number: US315412A
Authority: US
Inventors: Toland William Craig; Bassist Ellis
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-01-24
Filing date: 1940-01-24
Publication date: 1943-03-02
Anticipated expiration: 1960-03-02
Also published as: CA432735A; US2313848A

Description

March 2, 1943. w. c. TOLAND ETAL 2,312,852

LIGHT-SENSITIVE ELEMENT Filed Jan. 24, 1940 E29. 1 I V /'A Patented Mar. 2, 1943 William Craig Toland and Ellis Bassist, Brookline, Mass., assignors to William Craig Toland, Brookline, Mass., as trustee Application January 24, 1940, Serial No. 315,412

4 Claims.

This invention relates to light-sensitive elements and more especially to light-sensitive elements for use in connection with printing.

A chief object of the invention is to improve light-sensitive elements and to devise a novel light-sensitive product in which a light-sensitizing salt, such as a silver compound or other similar metal compound, is associated with a support suitable for comprising a planographic printing plate. A further object is a simpler, cheaper, and more eifective light-sensitive member. The invention also aims to indicate an improved method of preparing planographic printing plates and to present a plate having a novel combination of printing and non-printing portions.

Attainment of these and other objects will be readily understood from the following description when read in connection with the accompany drawing and the novel features will be more particularly pointed out in the appended claims. R.

In the accompanying drawing:

Fig. 1 isa diagrammatic view illustrating a. planographic printing plate support employed in forming the plate of the invention.

Fig. 2 is a diagrammatic view illustrating a coating step resorted to in carrying out the'invention.

Fig. 3 is still another diagrammatic view illustrating the step of coating a light-sensitive material on a plate construction similar to that shown in Fig. 2; and

Fig. 4 is still another diagrammatic view illustrating the coating indicated in Fig. 3 exposed and developed to comprise a printing plate.

In a co-pending application, Ser. No. 170,762, filed Oct. 25, 1937, means have been described and claimed for forming a planographic printing plate. Water retention is effected by the use of hydrophilic synthetic materials in the nonprinting portions of the plate and the hydrophilic materials may, if desired, be associated with supports of non-metallic character, such as those of paper or plastic materials. One example of a hydrophilic material described in the above indicated application, suitable for this purpose, is polyvinyl alcohol. Other vinyl compounds and other synthetic normally hydrophilic resins may be employed.

In the accompanying drawing, numeral I denotes a planographic printing plate base more particularly shown in Figure 1. Various materials may be employed to comprise the support I and a preferred material consists in a laminated paper and/or resin structure as described and claimed in our Patent No. 2,280,985 issued April 28, 1942.

Upon the support I is applied a film of a hydrophilic material 2, such as a vinyl compound, as described in the above referred to co-pending application Ser. No. 170,762, and as is further illustrated in Fig. 2 of the drawing. It is pointed out that the coated member shown in Fig. 2 comprises a workable planographic printing plate base presenting a water-receptive surface of ungrained and non-metallic character.

In accordance with the invention. a photosensitive emulsion is prepared and a coating 3 of the emulsion is applied directly over the hydrophilic layer 2, as has been illustrated in Fig. 3. The emulsion contains a highly light-sensitive agent which is adapted to maintaining its sensitivity for extended periods of time. As one example of a suitable emulsion, there may be cited a silver halide salt such as silver bromide, mixed with a colloid as a gelatin. The coating is allowed to dry and thereafter protected from exposure to light to comprise a light-sensitive ele-. ment which may be kept in darkness for extended periods and at any desired time exposed and developed to comprise a planographic printing plate.

There results a useful intermediate printing plate product which may be stored and shipped in an unexposed state, and which may be developed at any desired time with avoidance of the .many objections present in connection with developing a printing plate sensitized with achromic salt. It may be desired to employ other silver halides and other colloids mixed with them.

In accordance with the method of the invention, the use of gelatin for comprising the printing portions of a planographic plate is made,

practical by combining it with the metal salts noted and then effecting a bonded association with a planographic base in a manner not heretofore practical.

In detail, the method of preparation of a planographic printing plate consists in exposing with a photographic negative a light-sensitized plate support such as that above described and illustrated in Fig. 3. Exposure of the silver salt provides a latent image which may be developed in a developer such as hydroquinone, metal catechol and the like. fixed in a non-hardening fixing bath of conventional nature, and the resulting silver image in the gelatin is thereafter converted by treatment with ammonium bichromate to silver chromate. The colloid containing the unexposed light-sen- The print can then be sitive salts is finally washed away in warm water or by some other suitable method, leaving a photographicimage l firmly embedded in gelatin which is hardened thereby and anchored on to the hydrophilic base.

Washing away is halted at the surface of the hydrophilic material which immediately leaves water-receptive portions and slightly upstanding grease-receptive printing portions. It will be seen that there is efiected a novel step of hardening a silver salt in gelatin and at the same time the gelatin is firmly anchored to the base of hydrophilic material, with the hydrophilic material cooperating to embed the gelatin intimately therein.

The hydrophilic support/provides a bond for securing the gelatin not possible with supports such as metal or glass, which greatly increases the ability of the gelatin to comprise the printing portions of a planographic printing plate and withstand press operation.

The exposure can be quickly effected with a simple incandescent lamp in place of extended exposure to actinic light as is necessarywith chromic salts. This is important in connection with the speed of preparation and size of plate which may be obtained. Other procedures for washing or developing unexposed portions of colloid and halide salt away may be resorted to in place of the warm water cited, and similarly various developing, fixing, and bleaching agents may be resorted to in place of the specific ones set forth. It may further be desired to employ a translucent support for receiving the hydrophilic coating and emulsion as for instance supports of translucent resins or translucent papers. This further increases the utility of the lightsensitive element.

Several other advantages are obtained from the light-sensitive printing element and process of development set forth. The apparatus for exposure is greatly simplified. The coating of the printing plate support with a silver salt does not have to be effected while the salt is freshly prepared and as a result web coating operations may be resorted to which greatly facilitate and cheapen any such coating operations.

It will be seen that a novel printing member has been provided and a highly desirable combination efiected of a light-sensitive film with a hydrophilic film. Various savings in time, equipment and handling are thereby effected.

While there has been described a preferred embodiment of the invention, including specific materials and procedures, it should be understood that various other materials than those noted may be resorted to in keeping with the scope of the invention as defined by the appended claims.

Having described our invention, we claim:

1. As an article of manufacture a light-sensitive element comprising a support, said support presenting thereon a film of hydrophilic polyvinyl alcohol, a water-soluble colloid layer disposed over said film. said colloid having contained therein a silver halide light-senstive salt.

2. A light-sensitive element for use in preparing a planographic printing plate comprising a base member, a layer of a hydrophilic polyvinyl alcohol on said base, the hydrophilic polyvinyl alcohol being-adapted to receive moisture and comprise non-printing portions of a planographic printing plate, a coating of a photosensitive emulsion of gelatin and a silver halide superimposed on the layer of polyvinyl alcohol, said layer of polyvinyl alcohol having incorporated therein small amounts of the photosensitive emulsion.

3. A an article of manufacture a light-sensitive element for use in preparing a planographic printing plate, said light-sensitive element including a base, a layer of a hydrophilic polyvinyl alcohol overlying said base, a photosensitive emulsion of gelatin and a silver halide coated over said hydrophilic alcohol, the gelatin and silver halide being impregnated in the hydro-- philic alcohol, thereby to bond the photosensitive emulsion to the polyvinyl alcohol.

4. As an article of manufacture a lightsensitive element for use in preparing a planographic printing plate, said light-sensitive element including a base, a layer of a hydrophilic polyvinyl alcohol overlying said base, a coating of a photosensitive emulsion of gelatin and a silver halide superimposed on the polyvinyl alcohol layer, underlying portions of the coating of photosensitive emulsion extending into the polyvinyl alcohol layer.

' WILLIAM CRAIG TOLAND.

ELLIS BASSIST.