US3445268A - Laminar sheet material for making negative transparencies - Google Patents

Description

May 20, 1969 H. HEICHLINGER 3,445,268

LAMINAR SHEET MATERIAL FOR MAKING NEGATIVE TRANSPARENCIES Filed Oct. 26, 1964 Heinrich flez'c'fiinger United States Patent O LAMINAR SHEET MATERIAL FOR MAKING NEGATIVE TRANSPARENCIES Heinrich Heichlinger, Leonrodstrasse, Munich H, Germany Filed Oct. 26, 1964, Ser. No. 406,512

Claims priority, applicatiorlr Germany, Feb. 27, 1964,

Int. or. s44a 1/14; B41c 1/06 US. Cl. 11776 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the preparation of negative transparencies which may be employed as negative masters in offset printing, and particularly to a laminar sheet material from which such masters may be prepared by a simple mechanical process.

It has been common practice heretofore to produce offset printing masters by photographic methods even when the subject matter to be reproduced was typed matter set in a form. An imprint of the typed matter on white paper is usually photographed, and the photographic image is further processed to produce an offset printing master.

Those skilled in this art are aware of the need for a simpler procedure, and various solutions to the problem at hand have been proposed from time to time. They did not find common acceptance because of the need for a multiplicity of manipulative steps, the use of materials which were not rugged enough for being stored and handled in the manner customary in the printing trade, or both.

An object of the invention is the provision of a sheet material which can be converted to a negative transparency suitable for use in offset printing by a simple activating step and by contact with type matter and the like ap plied under moderate pressure.

Another object is the provision of sheet material for the purpose indicated which, when not activated, is capable of storage without deterioration in the form of tightly wound rolls and which is insensitive to rough handling.

Yet another object is the provision of sheet material from which negative transparencies can be made by contact with type matter and the like without preparatory operations which would involve the type matter.

With-these and other objects in view, the invention in one of its aspects provides a laminar sheet material whose base is a transparent carrier foil. The material further comprises a layer mainly consisting of a solventvapor activated adhesive which is normally nontacky, and also including coloring material which is at least partly opaque to at least a portion of the light spectrum, the term being understood to include the ultraviolet and infrared range. A separating layer is interposed between the foil and the adhesive layer and normally connects the same in parallel alignment. The separating layer prevents strong adhesion of the foil to the colored adhesive layer when the adhesive is activated.

Other features and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 shows sheet material of the invention in cross section on a greatly enlarged scale;

FIG. 2 shows the material of FIG. 1 arranged on a support, the view being in cross section and on a scale smaller than that of FIG. 1;

FIG. 3 illustrates apparatus for activating the sheet material of FIG. 1 in an elevational sectional view on a scale smaller than that of FIG. 2; and

FIG. 4 illustrates the preparation of a negative transparency from the sheet material of FIG. 1 when activated, the view corresponding to that of FIG. 1.

Referring now to the drawing in detail, and initially to FIG. 1, there is shown a laminar sheet material 1 whose base is a foil 2 of transparent terephthalate polyester material of the type sold under the registered trademark Mylar. The dimensional relationships of the several layers in the sheet material 1 may be read from the drawing, the carrier foil 2 having a thickness of 0.025- millimeter (one mil).

The top layer 3 of the sheet material consists mainly of a solvent-vapor activated adhesive which is colored brownish red by finely dispersed organic dyes. It has the following composition in parts by weight:

The central separating layer 4 which normally connects the foil 2 with the adhesive layer 3 has the following composition:

Parts Dextrin 8 Glycerol 20 Sodium lauryl sulfate 0.5

The sheet is prepared by first applying an aqueous solution of the ingredients of the separating layer 4 to the carrier foil 2, and by evaporating the water as far as possible. Traces of residual water do not significantly affect the weak adhesion between the readily frangible separating layer 4 and the foil 2, nor that between the separating layer and the adhesive layer 3.

The latter is applied by dissolving the ingredients listed above in a sufiicient minimum amount of toluene, and by coating the dried separating layer with the toluene solution. After removal of the toluene by evaporation, the top layer 3 is nontacky and adheres to the separating layer sufficiently well to permit handling of the finished sheet material. The sheet material, which is preferably prepared in the form of long strips, may be rolled, and stored or shipped in the rolled condition without deterioration.

Methods suitable for coating the carrier foil 2 with the aqueous solution which forms the separating layer 4, and for coating the dried separating layer with the toluene solution of the top layer ingredients are too well known to require detailed description. The coatings may be formed by casting, spraying, or brushing relatively dilute solutions of the ingredients on the substrate, or by applying more viscous solutions or dispersions by means of knife coating apparatus. The amounts of solvent to be added to the nonvolatile ingredients listed above will 3 readily be selected to fit the intended method of application.

When it is intended to prepare a transparency from the sheet material of the invention, the sheet 1 is secured to a suitable rigid support by means of tacks, staples or the like. FIG. 2 shows the sheet 1 attached to a wooden board 5, the fasteners employed having been omitted for the sake of clarity.

FIG. 3 shows apparatus for activating the adhesive in the top layer 3 of the sheet 1. The apparatus essentially consists of a flat closed box 6 equipped with narrow horizontal ledges 7 on two opposite internal walls. The board 5 is supported on the ledges 7 in such a manner that the attached sheet 1 spacedly faces the bottom of the box 6 which is covered with a layer of toluene 7'. The space 8 between the toluene layer and the sheet 1 is thus saturated with toluene vapors which are partly absorbed in the adhesive of the top layer 3 and activate the adhesive. When the layer 3 has become sufiiciently tacky, the board 5 with the attached sheet 1 is withdrawn from the box 6 through a non-illustrated opening normally closed by a cover, and is placed on a table with the sheet 1 facing upward.

FIG. 4 shows the position of the sheet at this stage of the process, but the board 5 and other supporting structure have been omitted. FIG. 4 also shows a type 9. In preparing a negative transparency, a form of which only the type 9 is visible in the drawing, is brought down on the top layer 3 of the supported sheet 1 with sufficient pressure to cause adhesion of the contacted portion 10 of the activated layer 3 to the type matter. When the form is then moved upwardly away from the nonillnstrated table, it takes the conforming portion 10 of the top layer 3 with it. There is formed a sharply defined opening in the mechanically weak, colored adhesive layer 3.

The activating small amounts of toluene are permitted to evaporate from the perforated adhesive layer 3, whereupon the sheet 1 may be separated from the board 5 and constitutes a negative transparency in which the type matter of the form is represented by fully transparent openings in the colored adhesive layer which itself transmits only brownish red light. Proper positioning of the transparency on an illuminated planning table is greatly facilitated by the fact that even those portions of the sheet which are substantially opaque to actinic light rays are transparent to the non-actinic red part of the spectrum.

As shown in FIG. 4, the very thin, transparent, and frangible separating layer 4 is being retained on the carrier foil 2 when the corresponding portion 10 of the adhesive layer is being lifted by the type 9. Such a behavior of the separating layer is often observed, but is not necessary for proper use of the laminar sheet material. Depending on the pressure with which the type 9 is impressed on the activated sheet 1, the entire portion of the separating layer corresponding to the lifted top layer portion 10 or fragments thereof may adhere to the removed portion 10 without materially aifecting the result achieved.

Vapor-activated adhesive compositions are well known in themselves, and it will be understood that compositions other than that described for the purpose of the disclosure may be employed. Separating media which have the necessary minimal adhesion to the adhesive layer and to a transparent foil base are known and available for use with the known adhesive compositions other than the one described. The polyester material of the carrier foil may be replaced by polystyrene, polycarbonates, cellulose esters, and similar organic polymers that are commercially available in the form of transparent sheets or foils.

The separating layer of the composition indicated is equally applicable to such other carrier materials, but better results with other adhesive compositions may be achieved when the dextrin is supplemented or replaced by such known water soluble or water dispersible materials 4 as gelatin, gum arabic, or soap. The glycerol may similarly be replaced by other plasticizers or dehydrating agents.

Resins which may replace the pine rosin in the adhesive composition include gum Damar, gum Elemi, gum Copal, polyvinyl ethers and esters, polyisobutylene, and acrylic resins, and those familiar with the formulation of adhesive compositions will readily substitute numerous other suitable materials.

The coloring matter incorporated in the adhesive may be chosen in accordance with the process in which the laminar sheet is to be employed. A combination of red and brown dyes in the adhesive layer is impervious to the portion of the spectrum which makes chromate-sensitized gelatin or glue insoluble in water. Other colors may be chosen for printing processes employing other sensitized material. Pigments may replace the soluble dyes in preparing sheet materials which are at least partly transparent to a portion of the light spectrum. The use of sufficient amounts of pigments results in sheets which are normally fully opaque. Carbon black is preferred where maximum contrast between the transparent and opaque portions of the negative is desired.

Xylene and the halogenated hydrocarbons commonly employed as dry cleaning solvents may replace the toluene layer 7' when the adhesive composition is based on pine rosin, but vapors of other solvents will be chosen with some compositions that consist largely of other resins. It is not necessary that the solvent vapors be compatible with or soluble in all ingredients of the adhesive composition to achieve the desired plasticizing or softening effect, and the solvent employed in the activating treatment may therefore be different from that employed in the coating process. Ethanol, for example, does not soften the rubber and paraffin in the composition described in detail hereinabove, but it is sufiiciently soluble in the rosin, the ethyl cellulose, and the camphor to permit its successful use as an activating vapor.

The amount of solvent vapor absorbed by the adhesive layer is readily judged by the tackiness of the sheet surface, which in turn is best determined by touch. The sharpness of the perforations produced in the finished negative transparency is related to the proper softening of the adhesive layer, and the tackiness of the activated sheet which produces the sharpest negatives is readily determined by trial for any particular material that is to be reproduced.

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention, and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. A laminar sheet material for making negative transparencies comprising, in combination:

(a) a transparent carrier foil;

(b) a layer consisting essentially of an adhesive composition capable of being activated by solvent vapor, but being normally nontacky, and of coloring material at least partly opaque to at least a portion of the light spectrum; and

(c) a transparent separating layer interposed between said carrier foil and the adhesive layer, said separating layer connecting said foil and said adhesive layer in parallel alignment, and preventing adhesion of said foil to said layer when said adhesive composition is activated by solvent vapor.

2. A material as set forth in claim 1, wherein the adhesive layer is substantially transparent to a portion of said spectrum and substantially opaque to the remainder of said spectrum.

3. A sheet material as set forth in claim 1, wherein said separating layer is continuous and consists of franester.

References Cited UNITED STATES PATENTS Hruska 117-63 X Magid 117-92 Newman 282-28 Newman et al. 117-36 McKnight et al. 117-36.7

Marx et al. 117-10 Dalton 117-36.7 Millar et a1. 117-72 Brown et al. 117-72 Chollar 101-4012 Potteiger 101-4012 WILLIAM D. MARTIN, Primary Examiner.

B. D. PIANALTO, Assistant Examiner.

US. Cl. X.R.

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