US2319944A - Method of making printing members - Google Patents

Description

May -25, 9 J. J; ORMOND I 2,319,944

METHbD OF MAKING PIQINTING MEMBERS Filed June 30, 1941 Patented May 25, 1943 METHOD OF MAKING PRINTING MEMBERS John J. Orniond, Boston, Mass., assignor of twothirds to Joseph D. Ramsey, Boston, Mass.

Application June 30, 1941, Serial No. 400,424

6 Claims.

This invention relates to methods of engraving and more especially to methods of etching rolls to form intaglio printing members.

A chief object of the invention is to improve methods of engraving and to devise an improved etching procedure with a view to reducing the occurrence of undercutting. Another object of the invention is to provide a method of varying or controlling the depth of etching carried out at different points on a roll surface. A further object is to provide a cheap, fast, efficient and simple method of etching.

The nature of the invention and its objects will be more fully understood from the following description of the drawing and discussion relating thereto.

In the accompanying drawing:

Fig. 1 is a perspective view diagrammatically illustrating the method of the invention.

Fig. 2 is another perspective View illustrating a printing roll as etched by the method illustrated in Fig. 1; and

Fig. 3 is a fragmentary detail View in cross section.

Referring in detail to the drawing, Fig. 1 diagrammatically illustrates a method of etching in accordance with the invention, in which an intaglio printing roll of the type employed in textile printing is prepared. It is intended that various other types of printing members, as relief printing rolls, relief printing plates and the like, may be prepared by the method of the invention.

Numeral 1 refers to a roll of copper of the type generally employed in making textile printing rolls and adapted to be etched by an etching reagent such as iron perchloride.

In accordance with the method of the invention, printing plates are prepared in the form of the design or subject matter desired to be etched on the surface of the roll I. This may be carried out by usual photo-engraving procedures or in various other ways. The plates are then inked with a special ink of acid-resisting character, and the ink is collected upon an offset printing member from the surfaces of the plates.

Thereafter the offset printing member applies the acid-resisting material 2 in selective amounts over the surface of the roll I, to provide the design outline 3, and lines 4 of acid-resisting material which are adapted to permit etching of ground lines within the outline 3..

The acid-resisting material employed may, for example, consist of a relatively light or thin asphaltum which is moderately acid-resistant. This coating 2 is allowed to dry thoroughly. The roll is then rotated in a tank containing hot liquid gelatin, to take on a coating of the gelatin which, upon cooling, provides a solid blanket 5 entirely surrounding the roll and superimposed over the coating of asphalt resist material 2. The gelatin is preferably of a thick consistency as applied on the roll to quickly form a relatively thick layer over the resist material.

While thus covered by acid-resisting material and gelatin blanket 5, the roll is immersed in a tank containing an etching reagent, as iron perchloride. The acid reagent is absorbed in the gelatin blanket 5 and passes through it to attack those parts of the surface of the roll I, which are not covered by the acid-resisting material 2. The acid reagent may also be satisfactorily applied by spraying or coating and such operations may be further resorted to, to apply additional amounts of acid after a first immersion treatment. Etching is continued for a suitable period and the coating of acid resist 2 and blanket 5 are dissolved away in suitable solvents, leaving an etched design outline 6 and etched ground lines 1, as illustrated in Fig. 2.

An important feature of the procedure noted is the use of the blanket of gelatin overlying the acid-resisting material. This blanket afiords a very desirable control of etching both in respect to the intensity of the bite and the direction of the bite. In the usual etching operations, difliculty is experienced from the tendency of acid reagents to etch sideways as well as inwardly, thereby undercutting those portions which it is desired to have appear in the finished printing plate. Such undercutting in the case of intaglio 2 rolls especially is less desirable. The use of the gelatin blanket minimizes the occurrence of undercutting by providing for the etching reagent being held directly against a surface to be etched with less etching reagent being in contact with the sides of partially etched or relieved portions of a roll surface.

Another feature of the invention is the use of relatively lighter acid-resisting materials made possible by the use of the gelatin blanket. Relatively heavy asphaltum is customarily employed to withstand the action of an acid reagent such as perchloride of iron in those areas of the printing member in which no etching is to occur. This asphaltum is of a relatively high viscosity and is difficult to apply, especially by mechanical printing means such as printing plates. Modifying the action of acid reagents by superimposing a gelatin blanket over resist material particularly makes possible the use of an acid resist such as thin asphaltum which is much more readily handled. This is particularly an advantage in offsetting acid-resist material to provide both bare metal outlines and spaced-apart etched lines for forming ground lines within the outline. Both the olfsetting operation and the control of the etching provide faster preparation of a printfor example absorbent resin materials, colloids such as gum arabic, glue and the like, and other substances may be resorted to. Modification in the method of applying the blanket may also be resorted to. For example, I may desire to print or otherwise apply in selective amounts an acidresist material over a sheet or film of gelatin, or other substance which is properly absorptive with respect to acid reagents. The film or sheet may then be wrapped around the surface of a roll which is to be etched, and the roll may be sub jected to the action of an acid reagent in some suitable manner as above outlined.

This procedure especially affords the advantage of applying acid-resisting material from an offset member to a fiat sheet,v which may be conveniently held in register with an offset member employed to print the acid-resisting material. Other advantages may also be provided by this procedure.

The method of applying resist on a sheet or film may be further modified by employing a sheet or layer of light-sensitive character. The acid-resisting material is applied as outlined on the light-sensitive gelatin, which may thereafter be exposed to light through a negative which will provide for hardening at predetermined points throughout the gelatin sheet. The exposed sheet containing relatively soft portions, and including the acid-resisting material, may then be applied around the surface of a roll to be etched.

The hardened portions will present material which is more resistant to penetration by an acid reagent than unexposed portions-thereof, with the result that a variation in the etching action of the acid reagent is obtained. Acid will pass through the unexposed portions of the gelatin faster than in the exposed portions, and relatively deeper bites may be obtained at selected points, as governed by the acid-resistin material occurring below the gelatin layer or blanket. The procedure of selectively hardening gelatin may also be practiced in connection with a blanket or coating of sensitized gelatin which has been applied around the surface of a roll in a liquid state. and thereafter allowed to harden.

It should be noted that inetching rolls for textile printing, a common requirement is to provide an outline of designs of one depth of etch, and to provide within the design a plurality of ground lines of a different depth of etch. The ground lines help to provide proper weight of color when the roll prints with a light printing material such as a dye. The method just above outlined of controllin the depth of etch by relatively hard and relatively soft blanket portions, is particularly suitable for allowing relatively deep etching to occur at bare metal roll surfaces correspond ing to the outline of the design, while etching relatively shallow ground lines within the outline, and avoiding a separate etching operation with the etched outline filled in as is conventionally done.

Variation in etching may b further obtained by using relatively thick and relatively thin gelatin portions over the acid-resisting material. This may be done by applying additional amounts of gelatin over a coating already applied in selected areas, with the relatively thicker gelatin portions thus obtained actin to slow up passage of acid reagents therethrough, as compared with the relatively thinner portions of the blanket. Various other changes may be resorted to.

It will be seen that the method of the invention provides an efficient means of engraving, charac terized by avoidance of undercutting, greaterv various other changes and modifications may be resorted to, in keeping with the spirit of the invention as defined by the appended claims.

I claim:

1. That improvement in methods of engraving which comprises ofiseting selective amounts of asphaltum over the surface of a printing member, then coating the roll with an acidabsorbent colloidal material and then etching the roll, the coated colloidal material being uniformly absorptive, throughout all points in its surface, with respect to an etchin reagent.

2. That improvement'in methods of engraving which comprises applying acid-resistmaterial on the surface of a printing roll, then coating gelatin overthe acid-resisting material, and then etching, while the gelatin is uniformly absorptive, at all points therein, with respect to an etching reagent. v

3. That improvement in methods of making printing rolls which comprises offsetting on a roll to be etched acid-resist material in accordance with the outline of a design, said acid resist material being of a thin consistency adapted to offsetting from a transfer blanket, then applying gelatin over the roll and resist material, and then etching the roll with iron perchloride while'the gelatin coating, ,at'all points therein, is in a uniformly absorptive state with respect to the iron perchloride.

4. That improvement in methods of making textile printing rolls which comprises applying on a copper roll surface acid-resist material in amounts suitable to, form an outline of a design desired'to be etched on the roll, the, applying additional resist material within the said outline in the form of spaced-apart lines adapted to constitute a ground, coating the roll and resist material with hot gelatin, drying the gelatin and etching the gelatin-coated roll with iron perchlo-= ride while the gelatin coating, at all points, is in a state of uniform absorptivity with respect to the iron perchloride.

5. That improvement in. methods of engraving printing members which comprises applying acid-resist material on a sheet of acid-absorbent colloidal material, then mounting the sheet on the surface of saidprinting member to be etched, and then etching theprinting member while the colloidal material at all points is held uniformly absorptive with respect to an acid etching reagent.

6. That improvement in methods of engraving which comprises. providing a resist material of sufliciently thin consistency to permit its being offset from a transfer blanket to the surface of a printing member, offsetting selective amounts of the resist material on the surface of the printing member, applying a .colloidal coating over the printing member and the selective amounts of resist material,. said colloidal material, at allpoints, being of a uniformly limited absorptive characterwith respectto etohing'reagents, said coating further being effective in combining with the resist material to prevent, for a limited period of time, an etching reagent from attacking the surface of the printing member in those areas coveredby the resistmaterial..

- Jon N J; oRMoNn.

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