Printing Members And Methods For Graphic Composition

Abstract

Apparatus for a gravure-type printing process utilizing a composing member having a multicellular surface pattern, and a pick sheet coated on one side with a layer of polymer-containing, thermoplastic material. All of the cells of the composing sheet are initially filled with a solid material which is selectively removable from individual cells. The cell-fill material is specially formulated to exhibit a specific affinity for the thermoplastic coating on the pick sheet when the coating is activated through localized heating. Graphic representations that are infrared absorbent are recorded on the uncoated side of the pick sheet which is then exposed to infrared radiation while the coated side is held in close contact with the filled cellular surface of the composing member resulting in an adhesive attraction between the coating and the solid material in the cells beneath the indicia. Separation of the two elements removes the cell-fill material from only those cells which define imaged areas corresponding to the indicia to be reproduced. The empty cells are receptive to filling with an ink, while nonimaged areas of the sheet contain no printing cells, so that the composing member can then be used as a printing master. The pick sheet, carrying a discontinuous, raised image, comprising a multiplicity of uniformly distributed, discrete particles of solid material bonded to the thermoplastic coating, can be employed as a relief printing plate.

Description

SUMMARY OF THE INVENTION

This invention relates to materials and processes useful in the field of graphic arts. More particularly, it relates to a simplified gravure plate-making procedure, a method of composition for office duplication, and to printing plates of both intaglio and relief image type, which are produced thereby.

Presently used methods of duplicating typewritten copy in offices are through the use of transfer papers such as carbon paper, pressure-sensitive papers, spirit duplicating, mimeograph, offset duplicating, electrostatic duplication, thermography, diffusion transfer, dye-gelatin transfer, diazo duplication and photoelectric facsimile duplication.

Most, if not all, of such previously known processes have one or more rather serious disadvantages or deficiencies such as severe limitations on the number of copies obtainable, slow duplication speed, the necessity for handling chemicals such as highly colored transfer coatings or printing inks, the complexity of the duplicating process requiring skilled operators, high equipment cost, difficulties in correcting errors on plates or masters, and the necessity for the use of special copy papers.

Heretofore, the good quality of print obtainable and the simplicity of the printing operation has made the photogravure process attractive for duplication uses. However, the principles of gravure printing have never been adopted for shortrun duplication because of the great complexity and high cost of the photographic and etching processes necessary for producing intaglio printing plates or cylinders.

Accordingly, it is an object of the present invention to provide novel thermographic materials and methods which overcome many of the disadvantages of prior-art methods of office duplication and offer advantages heretofore available only in gravure printing processes and materials. More specific objects are to provide methods for composing intaglio images suitable for use in gravure printing and for producing printing reliefs suitable for use as letterpress printing plates and the like. A further object is to provide such methods which utilize economical materials in convenient process steps. Other objects, features, capabilities and advantages which are comprehended by the invention will be apparent from the description and claims which follow.

Briefly, the present invention includes a composing member comprising a support having a multicellular printing surface formed of uniformly distributed cells opening onto the surface and indicia-composing elements of solid material filling each of the cells, which elements are selectively removable from individual cells. A recording medium, termed herein a "picksheet," carrying the graphic representations to be reproduced is coupled with the composing member and the cellular material is removed from selected cells to define imaged areas in the cellular surface corresponding to indicia to be reproduced. The empty cells are receptive to filling with a gravure ink while nonimaged areas of the cellular surface contain no printing cells, so that the composing member can be used as a printing master. When provision is made to transfer the indicia-composing elements removed from the cellular surface to the surface of a stratum where such elements are bonded in orderly array, there is produced a relief printing member comprising a discontinuous raised image consisting of a multiplicity of spaced, minute protuberances uniformly distributed over the areas defined by the image.

BRIEF DESCRIPTION OF THE DRAWING

Objects and advantages of the present invention will become more apparent from a consideration of the following specification and claims, when taken in conjunction with the accompanying drawing, wherein:

FIG. 1 is a diagrammatic view of a composing unit showing a pick sheet coupled with a composing member to produce a composed printing plate in accordance with one embodiment of the present invention;

FIG. 2 is an enlarged fragmentary view of a portion of the printing plate of FIG. 1, showing the emptied cells inked for printing;

FIG. 3 is an enlarged, fragmentary, cross-sectional view of a printing plate taken along the line 3-3 of FIG. 2;

FIG. 4 is an enlarged cross-sectional view of a pick sheet taken along the line 4-4 of FIG. 1, showing the discontinuous raised image bonded to the coated side of the pick sheet opposite indicia placed on the recording surface of the sheet;

FIG. 5 is an enlarged fragmentary view of a portion of the raised image carried by the pick sheet shown in FIG. 1;

FIG. 6 is a side elevational view of a pick sheet coupled with a composing member during the process of composing indicia to be reproduced;

FIG. 7 is an enlarged plan view of a portion of the composing member shown in FIG. 1 after composition has been completed and the two sheets have been separated; and

FIG. 8 is an enlarged side elevational view of another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The Composing Member

Apparatus used in the practice of the present invention includes a composing member, which may be in the form of a sheet, cylinder, plate, belt, or the like, comprising a support having a multicellular printing surface formed of uniformly distributed cells opening onto the surface, and indicia-composing elements formed of solid material which fill each of the cells and which are selectively removable therefrom under the influence of localized treatment initiated by the application of external agents. By removing composing elements only from selected cells, imaged areas which correspond to indicia to be reproduced are formed in the cellular surface.

Preferably, the multicellular printing surface is formed on a moldable support made of a solid nonmetallic material which is not deformable at temperatures used in practicing the invention, such as for example, a synthetic plastic. The material of the cellular surface must be tough, resistant to scratching or marring during processing operations and essentially chemically inert to other substances used in the composing or printing processes of the invention. Also this material should have a low coefficient of friction across its surface to facilitate the movement of a doctor blade thereacross. In addition, it must have a bonding affinity for the solid material filling each of the cells so that selected indicia-composing elements can be removed from the composing member while the remainder will remain firmly secured in the cellular surface during the operation of the invention.

Referring now to the drawing, and more particularly to FIG. 1, for purposes of illustration there is shown diagrammatically a composing unit for use in a thermographic process which comprises, in combination, a composing member 10 combined with an overlying pick sheet 40 to form an assembly in which the two elements utilized in the composing process are coupled together at a common edge 11. In this embodiment the composing member 10 is shown as a generally rectangular sheet of plastic having a multicellular surface 20 of individual cells each initially filled with a solid material 25. The assembly also includes a pick sheet 40 consisting of an original sheet 42 of paper or the like coated with a coating 45 of polymer-containing, thermoplastic material having a latent specific affinity for the solid material 25 filling the cells of the composing member. The two elements are assembled with the coating 45 of thermoplastic material operatively associated with the solid material in the filled cells 20, whereby infrared absorbent indicia 64 placed on the original sheet 42 can be heated preferentially to raise the temperature of the thermoplastic coating 45 to an active state in areas underlying the indicia, so that, upon separation of the original sheet 42 from the multicellular surface 20, solid material 25 from cells defining imaged areas 15 corresponding to indicia to be reproduced are selectively removed from the multicellular surface and are bonded as a raised image 15' to the coating 45 on the original sheet which is thereby adapted to function as a relief printing member and whereby said composing member is thereby adapted to function as an intaglio printing member.

Suitable plastic sheet is made from one or more of the following resins which may be modified with plasticizers or other modifying agents in accordance with conventional plastics technology:

1. acrylic resins, i.e. thermoplastic polymers or copolymers of acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile, e.g. polymethylmethacrylate.

2. cellulose resins, e.g. ethyl cellulose, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate.

3. polyolefins e.g. polyethylene, polypropylene and copolymers thereof.

4. polyamides formed by the polymerization of amino acids or by the condensation of polyamines with polycarboxylic acids, e.g. nylon.

5. polycarbonates which are resins produced by reacting polyphenols such as bisphenol A with phosgene, e.g. Lexan.

6. vinyl polymers and copolymers of vinyl acetate and vinyl chloride.

7. polystyrene

8. polyformaldehyde resins derived by the polymerization of anhydreous formaldehyde in a hydrocarbon solvent with the aid of an ionic catalyst.

Preferably, the composing member will be made from a synthetic plastic sheet material having a thickness of at least 0.003 inch. Advantageously, polypropylene or cellulose acetate sheet materials having a thickness in the range of about from 0.005 to about 0.040 inch will be employed. Utilizing a master matrix or mold of a screened cellular pattern, plates, cylinders or belts made from thin synthetic plastic sheet material can be prepared by continuous or even automated processes involving compression molding the overall cellular pattern of any predetermined screen size and depth into the plastic film or sheet surface. In accordance with the present invention the multicellular surface 20, contains in the range of from about 10,000 to about 160,000 individual cells per square inch uniformly distributed over the surface. As is more clearly shown in FIG. 3, all of the cells are substantially the same depth and have a depth in the range of about from 10 to 50 microns. Each of the cells are uniformly separated from each other by the cell walls 24 of the composing member with a separation in the range of about 2 to 20 microns. In a preferred embodiment all of the cells will have substantially the same shape and dimensions although it is understood that a pattern of variable-shaped cells can be utilized. The plastic sheet material having a multicellular printing surface is to all intents and purposes a gravure printing member which when all the cells are empty would print as a solid, overall color by virtue of the fact that all of the cells in the printing surface are receptive to filling with ink.

According to the invention, all of the cells forming a cellular printing surface on a composing member are filled with indicia-composing elements 25 of solid material which are selectively removable from individual cells under the influence of localized treatment initiated by the application of external agents. The composing elements must adhere to the inner cell wall surfaces under normal conditions of use of the composing member, but can be removed from selected cells under special conditions to create imaged areas 15 in the printing surface consisting of empty cells 26 which are than available for inking. In preferred embodiments, the composing elements 25 are adapted to withstand repeated exposure to a fluid ink and the wiping action of a doctor blade without dislodgment from the cells in which they are contained.

In broad scope, any solid material capable of meeting the above requirements can be utilized as a suitable cell-fill material in the fabrication of composing members in accordance with the present invention. Preferably, the material used to fill the cells is a viscous essentially nonvolatile organic fluid dispersion having a high solids content which can be knife coated over the multicellular surface and which is capable of being hardened after deposition in the cells. It should also be thixotropic so that it can hold a predetermined shape during the preparation of the composing member. It should have a hardening temperature below the distortion point of the material of the cellular surface in which it is to be cast and should maintain a stable viscosity over prolonged storage periods. After hardening the cell-fill material must be tough. Further it must exhibit minimum shrinking during hardening and thereafter be resistant to extraction of its components by the ink used in the ultimate printing operation and by the materials used to clean the printing surface. Suitable organic materials include meltable resins, fused plastisols, cross-linked thermoset polymers and mixtures of these. The preferred material in accordance with this invention is a fused vinyl plastisol.

For present purposes, a "plastisol" is defined as a paste dispersion of one or more resins in a suitable liquid plasticizer and optionally containing other ingredients such as stabilizers, fillers, wetting agents, gelling agents and the like. Resins employed include polyvinyl chloride or polyvinylidene chloride, or copolymers of these. Polyethylene possessing an extremely fine (approximately 1 micron) particle size is also suitable. The plasticizer at room temperature is a nonaqueous liquid that does not dissolve the resin. At an elevated temperature the resin undergoes solvation and goes into solid solution in the plasticizer. Obviously, any equivalent composition which meets the requirements of the present invention is to be included in this definition. Since plastisols become solid solutions at relatively moderate temperatures, fusing can be carried out uniformly by any suitable heating technique by which the temperature and time of fusing can be accurately ascertained and controlled.

In the present invention, a preferred primary resin for use in preparing a suitable plastisol is polyvinyl chloride (PVC) having a molecular weight of more than about 10,000, preferably soap free and finely divided having a particle size in the micron and submicron range. The term "polyvinyl chloride" as used herein is inclusive not only of polyvinyl chloride homopolymers of all types, but also of copolymers of vinyl chloride, such as copolymers of vinyl chloride and vinyl acetate, copolymers of vinyl chloride and vinylidene chloride, copolymers of vinyl chloride with maleic or fumaric acid esters, copolymers of vinyl chloride with styrene, and copolymers of vinyl chloride with acrylonitrile, as well as mixtures of polyvinyl chloride resins in a major proportion with a minor proportion of other synthetic resins conventionally used to modify vinyl dispersions, such as chlorinated polyethylene, or copolymers of acrylonitrile, butadiene and styrene.

The viscosity and flow characteristics of the plastisol are dependent upon the nature of the particular resin, the plasticizing or solvating efficiency of the plasticizers employed, the plasticizer concentrations, the quantity and type of fillers, and the stabilizer system used. Of all the components mentioned, the plasticizers appear to exert the largest influence on plastisol viscosity and flow behavior. It has now been found that the type and concentration of plasticizers employed can be selected to achieve optimum degrees of viscosity, thixotropy, cohesiveness and infrared radiation reflectance, while at the same time producing a fused plastisol having a specific bonding affinity for a specific thermoplastic material.

Plasticizers employed in plastisol formulations should have negligible volatility at the fusion temperature of the plastisol, favorable viscosity so that the other components can be added without affecting adversely the workability of the plastisol, and be a good solvent for the plastisol resin at fusion temperature, yet must provide viscosity stability for considerable periods at room temperature.

In accordance with the present invention the primary plasticizing component of the vinyl plastisols preferably consists essentially of a major proportion of a monomeric plasticizer pivoted from the class consisting of simple esters and mixtures thereof capable of solvating vinyl dispersions at a temperature which is less than 160.degree. C., in admixture with a minor but shrinkage-reducing proportion of a polymeric plasticizer.

Suitable monomeric plasticizers include citrate esters such as acetyl tributyl citrate; phthalate esters such as dioctyl, butyl benzyl, dibutoxyethyl, and diisodecyl phthalate; phosphate esters such as octyl diphenyl, tris (dichloropropyl), and cresyl diphenyl phosphate; adipate esters such as benzyl octyl adipate; azelate esters such as di-2-ethyl hexyl azelate; sebacate esters such as dibenzyl sebacate; dibenzoate esters such as dipropylene glycol and hydrogenated terphenyl dibenzoate. Suitable polymeric plasticizers include polyesters such as Harflex 340 and epoxidized oils such as Plastolein 9717 and Paraplex G-62.

Generally, the plastisol will contain from about 45 to about 80 parts by weight of the primary plasticizing component per hundred parts by weight of primary resin, depending upon the particular plasticizer, the particular resin and the particular properties desired in the final product.

Stabilizers, conventional fillers, thickening agents and surface active agents, if employed, can be used in minor quantities, in accordance with conventional procedures. Where any particular color is desired, pigments having a relatively high refractive index are preferred so as to provide opacity to the material filling the cells. Particles of pigment filler in amounts in the range of from about 1 to 15 weight percent also assist in providing hardness and cohesiveness after the plastisol has been fused.

Stabilizers in amounts up to about 1.5 weight percent can be used to prevent heat deterioration of the plastisol during processing Suitable stabilizers include metal salts of organic acids such as lead carbonate, barium-cadmium laurate and stearate, zinc laurate, zinc stearate, as well as organic tin compounds, epoxies, organic phosphites and chelators. Conventional thickening agents, such as, the colloidal silicas and aluminum silicates are generally employed to provide thixotropy and other necessary rheological characteristics to the composition prior to fusion. Preferably, from about 0.3 to 8 weight percent of thickening agent will be utilized.

Advantageously, about 0.3 to 3 weight percent of a suitable surface active agent will be incorporated into the plastisol composition. Such agents promote the particulate dispersion of resin and pigment in the liquid plasticizer phase by destroying the tendency of the small particles to cluster together. These surfactants also help to stabilize viscosity and by lowering the interfacial tension between plasticizer and air bubbles, aid in the removal of entrapped air from the plastisol. Because the surface characteristics of the various primary resins used in plastisol formulations are often quite different, it may be necessary in some instances to experiment with various anionic, cationic and nonionic surfactants in order to select the proper agent to obtain the optimum effect. However, the polyglycol ethers and esters of fatty acids have been found to be generally effective with any of the resins referred to above.

The method of formulating the organic material used to fill the cells of the composing member, is in accordance with conventional practice. If a vinyl plastisol is utilized, a preferred method involves the use of a shear-type mixer having a cooling jacket to prevent excessive buildup of heat which might cause premature solidification of the plastisol. Generally the resin is added to the mixing apparatus first, after which a quantity of plasticizer is added slowly, with agitation. The filler and other modifying agents are generally disbursed in the remainder of the plasticizer and added to the mixture in that manner. The components are then mixed until the plastisol is homogeneous and a stable emulsion or dispersion formed. Alternatively, the entire amount of plasticizers can be combined with the resin and the additional fillers, stabilizers and the like can then be added as finely divided solids. Deaeration is accomplished in accordance with conventional practice through the application of vacuum on a thin layer of plastisol or on a larger scale by mastication of the mixture on a three-roll paint mill.

In accordance with this invention a semifluid plastisol composition is formulated to achieve optimum degrees of viscosity, thixotropy, cohesiveness and infrared radiation reflectance. The composition is doctored across the cellular surface of the plastic sheet 10 to fill each cell so that its meniscus is convex without coating the surfaces of the surrounding cell walls 24. Thereafter, the plate or cylinder with its plastisol filled cells is subjected to a temperature sufficient to permit fusion of the resin. The required fusion temperature will depend upon the particular components of the plastisol and the mass of material in each cell, but it is generally of the order of about 160.degree. C. or less. Exposure of the plastisol filled cells to the fusion temperature for a sufficient period of time results in plastisol fusion to a solid mass and a slight shrinkage of the plastisol in each cell so that its surface is plane with the surrounding cell wall surfaces. Generally a heating period of from about 1 to 5 minutes will be required depending upon the formulation and the temperature employed.

The Pick Sheet

The apparatus of the present invention also includes a recording medium which conveniently can be termed a pick sheet. In one embodiment of the invention the pick sheet is used with the composing member 10. As shown in FIGS. 1 and 4, the recording medium 40 comprises an original sheet 42 having an indicia-receiving surface 44. In accordance with the invention the back of the sheet carries a coating 45 of polymer-containing thermoplastic material having a latent specific affinity for specific indicia-composing elements 25 and is adapted to bond to the solid material of the composing elements when the thermoplastic material 45 is activated at selected sites under the influence of localized heat treatment. The original sheet 42 can be composed of any suitable heat-resistant, near-infrared nonabsorbing material such as for example a synthetic plastic film or a thin, lightweight paper capable of being coated on one side with a film of polymer-containing thermoplastic material.

The original sheet 42 shown in FIGS. 1 and 4 is a thin sheet of paper of sufficient density to provide heat transfer but having sufficient rigidity or stiffness that it will handle well in a typewriter. For example, it has been found that a well-calendered 11-pound paper is suitable, this paper being defined as one of which 500 17.times.22-inch sheets will weigh 11 pounds. In this example the thickness of the sheet generally will be of the order of 0.002 inch. Carbonizing tissue of the dense type can also be used in a sheet having a thickness of for example about 0.0016 or 0.0017 inch.

Preferably, the polymer-containing thermoplastic material 45 will be coated on one side of the recording medium 40 in a thickness in the range of from about 0.05 to about 2.0 mils and more preferably in the range of from about 0.1 to 1.0 mils. This thermoplastic material is formulated to have a latent specific affinity for the solid material 25 filling the cells of the composing member 10 and is adapted to bond thereto when heated to activated i.e. tacky, temperature. Generally, thermoplastic material having an activation temperature above 50.degree. C. will be employed. Broadly, any polymer-containing thermoplastic material having a specific bonding affinity at its tackifying temperature for the cell-fill material can be employed in accordance with this invention. Illustrative of suitable thermoplastic coating material is polyvinylacetate, cellulose acetate butyrate, homo and copolymers of polyvinyl and polyvinylidene chlorides, and ethyl cellulose.

A preferred thermoplastic resin is cellulose acetate butyrate which is a thermoplastic resin formed by the reaction of purified cellulose with acetic and butyric anhydrides in the presence of sulfuric acid as catalyst and glacial acetic acid as solvent. This resin is commercially available in the form of white flakes or granules readily convertible into a plastic film. The ratio of acetic and butyric components can be varied over a wide range to tailor desired physical properties. A preferred thermoplastic resin which can be utilized in accordance with the present invention, is a cellulose acetate butyrate having the following approximate composition:

combined cellulose residue 46 percent

free hydroxy in cellulose residue 0.7 percent

combined butyryl 48 percent

combined acetyl 6 percent

This material having a softening point in the range of from 165.degree.--175.degree. C. is marketed by Tennessee Eastman Corporation under the trademark EAB 500-1.

The resinous material of which the thermoplastic coating is formed may be modified with softeners, plasticizers or the like to provide for a softening point within the temperature range of 50.degree. to 200.degree. C. It will be understood that where the conditions for developing higher temperatures are achieved, the softening range of suitable thermoplastic material may be correspondingly broadened or moved upwards.

Suitable plasticizers, softeners and the like for specific resinous materials can be selected readily by those skilled in the art from the data available in the plastics and resins fields. For example, polyvinyl chloride and vinyl chloride-vinyl acetate copolymers can be plasticized with dibutyl phthalate, diamyl phthalate, dioctyl phthalate, dibutyl cellosolve phthalate, tricresyl phosphate and triglycol di-(2 ethyl hexanoate). Polyvinylidene chloride may be plasticized to the desired degree with any one of a number of plasticizers or combinations thereof such as polychloro biphenyl, dibenzyl ether, tricresyl phosphate, and the like. Acrylic acid ester polymers, such as butyl methacrylate, ethyl acrylate, methyl methacrylate and the like may be plasticized with dibutyl phthalate, dibutoxy ethyl phthalate, chlorinated biphenyl, tricresyl phosphate, and the like. Amounts up to about 30 percent by weight, based upon the weight of the resin, may be successfully used with the above resins to impart the desired results.

The polymer-containing thermoplastic material can be coated on a paper or plastic sheet using conventional coating methods. Generally, the thermoplastic resin will be applied to the sheet 42 in a solvent solution. Suitable solvents include methylethyl ketone, acetone, methyl, ethyl, and isopropyl alcohols, toluene, xylene, esters such as methyl, ethyl, and isopropyl formates and acetates, and the like, low boiling point chlorinated aliphatic solvents such as methylene chloride, trichloroethylene and the like and low-boiling glycol ethers. Generally the coating will be sufficient to increase the weight of an 11 pound paper by about 1 to 5 pounds.

METHOD OF OPERATION

The novel process of the instant invention is more fully illustrated by the following examples which are given for illustrative purposes only and are not to be construed as limiting in any way the scope of the present invention.

The basic unit of this gravure duplicating discovery is the composing member used for transferring the image. Initially, a base plate is prepared by etching or molding an overall cellular pattern into sheets of flexible material such as plastic, metal, impregnated paper, fabric, or the like. In this example a plastic base plate was prepared from a 10 mil sheet of nonoriented polypropylene, one surface of which had an overall cellular pattern consisting of 90,000 cells per square inch. In order to produce the cellular printing surface a 300-line gravure screen was photographically transferred to a rigid copper photoengraving plate and chemically etched to a depth of 25 microns. Cell walls having a thickness of 28 microns in the film positive were reduced by the etching to approximately 10 microns. The master plate was then used to produce a phenolic resin matrix by compression molding and the matrix in turn similarly was used to produce the molded cellular pattern in the polypropylene sheet.

Each of the cells of the multicellular surface was then filled with an indicia-composing element of solid material 25 which is selectably removable from individual cells. The solid material in this example was a fused plastisol especially formulated to impart the desired chemical and physical properties to the finished composing member. The essential constituents of a suitable plastisol formulation are given below: ##SPC1##

In this example, the auxiliary resins vinyl toluene copolymer and vinyl toluene acrylate copolymer were mixed with the octyl diphenyl phosphate plasticizer and dissolved at approximately 120.degree. C. After cooling, the polyester resin and the surface active agent were blended into the mixture. Thereafter, the polyvinylchloride resin was added with stirring and finally the titanium dioxide filler and the silica pigment thickening agent were blended into the mixture. The final mixture was ground on a three-roll mill to achieve optimum dispersion and to eliminate entrapped air.

The semifluid plastisol composition was then doctored across the cellular surface of the polypropylene sheet to fill each cell so that its meniscus was convex without coating the surfaces of the surrounding cell walls. This can be accomplished by using a beveled, stainless steel doctor blade designed so that the angle between the lower surface and the upper surface of the beveled portion of the blade is approximately 35.degree.. The lower surface of the doctor blade should be oriented at an angle of approximately 30.degree. to the cellular surface.

After all of the cells had been filled with the plastisol composition the composing member was heated to a temperature in the range of about 300.degree. to 380.degree. F. for about 1 to 5 minutes during which time the resin components were completely solvated and fused. When the filled plastic sheet was subsequently cooled, the quantities of plastisol had solidified and shrunk so that each had a substantially flat surface which was level with the surface of the sheet. In addition, each quantity of plastisol had good mechanical adherence to the depressed surfaces of the cell in which it was seated.

The composing member is converted into a printing plate for transferring an image simply by removing the solid material 25 from selected cells to define imaged areas 15 in the surface 20 corresponding to indicia 64 to be reproduced. The term "image" is used herein to designate any form of graphic representations, such as writing, lettering, pictures, designs, etc. Creation of such images by removal of selected indicia-composing elements can be accomplished in any desired manner so long as the composing elements which are left in place 25 are not disturbed and will continue to adhere to the walls of the cells in which they are contained under normal conditions of use of the composing member as a printing plate. Preferably of course, the composing elements which remain in the printing plate will be able to withstand repeated exposure to an ink and the wiping action of a doctor blade without dislodgment from the cell. Following composition, the composed printing plate can be secured by any suitable means in a flat bed press or curved over the plate cylinder of a rotary press and secured thereto by suitable fastening means. As previously mentioned, the flexibility of the printing member depends largely upon the material employed as the support.

In a preferred embodiment of the present invention the composing member described above is converted into a printing plate utilizing a recording medium 40 comprising an original sheet 42 coated on one side with a coating 45 of polymer-containing, thermoplastic material, which has a latent specific affinity for the solid material 25 filling the cells of the composing member and is adapted to bond thereto when the thermoplastic material is raised to its activated, i.e., bonding, temperature.

A suitable recording medium is fabricated in accordance with the following procedure. A well-calendered, 11-pound paper in which each sheet was approximately 2 mils thick was coated with a solvent solution of the cellulose acetate-butyrate resin previously described. The coating solution was formulated by mixing 25 weight percent of cellulose acetate-butyrate with 25 weight percent of heptane and 50 weight percent of ethyl acetate. Solutions of the above composition together with from about 10 to 30 weight percent (based upon the weight of the thermoplastic resin) of dibutyl phthalate have been successfully employed to produce suitable coatings in accordance with the present invention. The coatings were applied by conventional techniques including reverse roll, knife overroll, or the air knife process. The dried coatings were nonblocking and nontacky at ambient temperatures but exhibited a specific adhesive attraction to the plastisol cell-fill material at elevated temperatures while exhibiting essentially no attraction for the material of the composing member.

The thermoplastic resin coated recording medium produced according to the method outlined above can then be used to image a suitable composing member in the following manner. The indicia or copy 64 to be reproduced is typed, written or printed on the uncoated side 44 of the recording medium 40 using graphic representations that are infrared absorbent. In this embodiment the ribbon, printing ink or writing material composition must contain a substantial amount of carbon, metallic pigment or other infrared absorbing substance. The printed recording medium, from which it is desired to produce a master sheet, is then placed coated side down over a plastisol-filled gravure plate or cylinder so that the thermoplastic coating 45 of the original sheet is in contact with the plastisol filled cells 20 of the gravure plate or cylinder. The printed surface 44 of the assembled composing unit 60 is then subjected to infrared radiation 62 in the manner exemplified by FIG. 6 of the drawing.

Radiant energy capable of the phenomenon of heat generation upon absorption in the materials comprising the representations 64 placed on the recording medium can be derived from the light sources rich in infrared which includes sources producing rays having a wave length in the range of from about 7,500 to 30,000 angstroms. These are above the visible range but below the extreme end of the infrared range. Radiant energy capable of the phenomenon of the type described may be found in the rays of the sun and therefore exists in ordinary daylight. However, they can only be developed in sufficiently high concentration by infrared sources such as a tungsten filament in a glass bulb or quartz tube operating at 3,000.degree.--4,000.degree. F. Most advantageously, an infrared source producing radiation in the range of from about 10,000 to 20,000 angstroms will be utilized. The amount of heat developed depends chiefly upon the duration of exposure and the intensity of the usable radiant energy of the infrared-emitting source. It also depends upon the depth and character of the material in which it is formed. In this example, preferably the two components, the composing member 10 and the recording medium 40, will be held in close contact with each other as for example by the use of pressure, such as can be supplied by the use of a roller and a tightly tensioned, infrared transparent belt or tape. A satisfactory source of radiation and pressure is a conventional thermo-type copier.

After an exposure time of from about 2 to 10 seconds the composing unit 60 is removed and the two components separated at which time it will be seen that the plastisol component 25 of each composing member cell, which was directly under an infrared-absorbent character 64 on the surface 44 of the recording medium 40, has been removed and is now adhering tightly to the coated side of the recording medium 40. As is shown in FIG. 1, the indicia facing the infrared source have been copied as direct-reading images 15 in the multicellular surface of the composing member 10. At the same time, as best illustrated in FIGS. 4 and 5, the indicia facing the infrared source have been copied in reverse on the coated side of the recording medium in the form of a discontinuous raised image 15' comprising a multiplicity of minute protuberances 46 uniformly distributed over the areas defined by the image.

In the above example, the infrared radiation does not generate heat until it is absorbed by the representations 64 on the indicia receiving surface 44 of the original sheet 42. Therefore, if the infrared radiation is directed onto the original sheet which is in surface contact with the plastisol-filled cells of the composing member 10, the radiation is absorbed by the representations of the original sheet and converted into heat only in the indicia. The heat generated by the absorbed radiation in the indicia penetrates the recording medium to the underlying layer of thermoplastic material 45 which is heated to its bonding temperature in areas corresponding to the indicia areas of the top surface of the recording medium. The cells in the printing surface of the composing member which define the imaged areas to be reproduced are now empty and receptive to filling with a gravure ink while the nonimaged areas of the composing member effectively contain no printing cells. The composed member can then be mounted in a gravure offset press or duplicator or the like designed to flood the cell surface with ink, doctor the surface to remove all excess ink from nonprinting areas, transfer the ink image to a rubber or other transfer roll, and then transfer the ink image to a sheet or web of copy paper. FIG. 2 illustrates diagrammatically, such a printing plate in which the empty cells have been filled with ink 27 in preparation for printing.

Following separation of the two components, the recording medium used to remove cell-fill material from selected cells of the composing member can be used directly as a relief printing plate. In this case the printing plate comprises a multiplicity of discrete, indicia-composing elements of preselected shape 46, bonded to the surface of a suitable substrate to define a discontinuous, raised image 15', corresponding to indicia 64 recorded on the record face 44 of the sheet. This sheet alone or carried on a suitable support can be used with a transfer member of the carbon ribbon or carbon paper type to produce direct reading copies of the indicia recorded on the upper surface of the sheet. Further, the relief printing member can be attached to a suitable support and be inked for use as a marking stamp or the like. A particular advantage of producing a relief printing member in accordance with the above process is that it is possible by this method to obtain a level printing surface of essentially uniform caliber.

A polypropylene printing plate produced in the manner described above has been used to produce high-quality copies using a nonvolatile, nondrying ink comprising hexylene glycol containing from about 2 to 10 percent of maleic anhydride rosin condensate resin (Arochem 404 made by Archer-Daniels-Midland Corporation). This resin is water insoluable but because of its high acid number is quite polar. Further it is highly soluble in glycol which is itself water soluble and somewhat hydroscopic. The ink is stable on an applicator felt but will precipitate the resin on absorption of moisture from the paper.

It will be understood that various modifications in the methods of fabrication and in the structure and use of the composing and the printing members may be affected by the application of knowledge familiar to those skilled in the pertinent arts without departing from the spirit and scope of the invention. For example, advantageous results can be obtained by employing a magnetic material to fill the cells of the composing member. Further, as shown in FIG. 8, relief printing plates 80 of the type described herein can be produced by bonding to the activated areas of the recording medium discrete particles 82 of solid material having essentially the same dimensions, such as for example nonfriable particles having a diameter in the range of from about 10 to 80 microns. Suitable particles are for example, ceramic or glass beads of suitable dimensions which can be applied to the tacky areas of the recording medium. Another aspect of the invention involves the utilization of indicia-composing elements having a liquid-filled synthetic resin structure comprising a porous resin base and liquids expressible therefrom under pressure or the use of micro capsules containing ink. In another embodiment of the present invention suitable printing plates can be prepared utilizing a plastic sheet having a multicellular surface prepared in the manner described above in which only selected cells are filled with solid material and the unfilled cells define imaged areas in the printing surface. Such printing plates can be prepared, for example, by the use of masking techniques in which selected cells are masked so that these will remain empty when the plastisol is doctored across the multicellular surface. A number of such modifications have been mentioned above, and others will surely occur as aforesaid in adapting the teachings of the present invention to specific printing applications.

Claims

What we claim is:

1. A composing member for use in a process for transferring an image of indicia to be reproduced, comprising

a support having a multicellular nonmetallic printing surface formed of uniformly distributed cells opening onto said surface,

each of said cells being filled completely with a composing element of solid material substantially nonabsorbing of near-infrared radiation having a wave length in the range of from 7,500 to 30,000 Angstroms,

said composing elements being adapted to withstand repeated exposure to fluid ink and the wiping action of a doctor blade, but being selectively removable intact from individual cells under the influence of localized heat treatment initiated by the application of near-infrared radiation,

whereby said composing elements can be removed from selected cells to define imaged areas in said surface corresponding to indicia to be reproduced.

2. The method of making a printing plate for reproducing indicia, comprising,

providing a support having a multicellular nonmetallic printing surface formed on uniformly distributed cells opening onto said surface,

filling each of said cells completely with a composing element of solid material which is capable of withstanding repeated exposure to a fluid ink and the wiping action of a doctor blade, but which is selectively removable intact from individual cells under the influence of localized treatment initiated by the application of external agents, and

removing composing elements intact from selected cells to define imaged area corresponding to indicia to be reproduced whereby the emptied cells are accessible for inking.

3. The method of making a printing plate for reproducing indicia comprising, providing a support having a multicellular nonmetallic printing surface formed of uniformly distributed cells opening onto said surface, each of said cells being filled completely with a composing element of solid material which is capable of withstanding repeated exposure to fluid ink and the wiping action of a doctor blade, but which is selectively removable intact from an individual cell under the influence of localized treatment initiated by the application of external agents, bonding selected composing elements to a layer of thermoplastic material which, when heated to an activated temperature, has a specific adhesive affinity for said elements and removing said bonded composing elements from selected cells to define imaged areas corresponding to indicia to be reproduced, whereby the cells thus emptied are accessible for inking.

4. The method of making a printing plate for reproducing indicia comprising, providing a support having a multicellular nonmetallic printing surface formed of uniformly distributed cells opening onto said surface, each of said cells being filled with a composing element of solid material which is capable of withstanding repeated exposure to a fluid ink and the wiping action of a doctor blade, but which is selectively removable from individual cells under the influence of localized treatment initiated by the application of external agents, providing a layer of thermoplastic material which when heated to an activated temperature has a specific affinity for said composing elements, raising selected areas of said layer of thermoplastic material to an activated temperature by localized heat treatment initiated by the application of infrared radiation, bonding composing elements from selected cells to said layer of thermoplastic material, and removing composing elements from said selected cells to define imaged areas corresponding to indicia to be reproduced, whereby the cells thus emptied are accessible for inking.

5. The method of making a relief printing member, which comprises, providing a composing member comprising a nonmetallic support having a multicellular composing surface formed of substantially uniformly distributed cells opening onto said surface, each of said cells being completely filled with an indicia-composing element of solid material substantially nonabsorbing of near-infrared radiation having a wave length in the range of from 7,500 to 30,000 Angstroms which is selectively removable intact from individual cells, providing a stream of polymer-containing thermoplastic material, and bonding an array of composing elements from selected cells of said composing member to the surface of said stratum to form a discontinuous raised image consisting of a multiplicity of spaced, minute, protuberances uniformly distributed over the areas defined by said image.

6. A method in accordance with claim 5, wherein each of said cells is filled with a solid material having a specific bonding affinity for a thermoplastic material under the influence of localized heat treatment initiated by the application of infrared radiation.

7. The method of making a relief printing member, which comprises

providing a composing member comprising a support having a multicellular composing surface formed of substantially uniformly distributed cells opening onto said surface,

filling selected cells with indicia-composing elements of solid material which are removable from said cells under the influence of localized treatment, to form an arrayment of indicia-composing elements defining an image to be printed,

providing a stratum, transferring said arrayment from the filled cells to the surface of the stratum, and simultaneously

bonding each individual element to said stratum to form a discontinuous raised image consisting of a multiplicity of spaced, minute protuberances uniformly distributed over the area defined by said image.

8. The method of making a relief printing member, which comprises

providing a recording medium having opposed record and printing faces,

said printing face having thereon a coating of polymer-containing thermoplastic material which is solid below 40.degree.C.,

recording on said record face graphic representations that are infrared absorbent,

applying to the surface of said printing face, at least in areas opposite the graphic representations on said record face, a monolayer of discrete particles of solid material each having essentially the same dimensions and shape, and

subjecting the recording medium to infrared radiation for a period of time sufficient to bond said particles to said thermoplastic coating and form a discontinuous raised image corresponding to the graphic representations of the opposed record face.

9. A method in accordance with claim 8, wherein said recording medium comprises a web, one face of which is coated with a film-forming thermoplastic material.

10. A method in accordance with claim 8, wherein said recording medium comprises an original sheet of thin, lightweight paper.

11. A method in accordance with claim 8, wherein said recording medium comprises a heat-transmitting synthetic polymeric film.

12. A composing unit for use in a thermographic process comprising, in combination,

a support having a multicellular printing surface formed of uniformly distributed cells opening onto said surface,

indicia-composing elements of solid near-infrared transmitting material filling each of said cells,

each of said elements being adapted to withstand repeated exposure to a fluid ink and the wiping action of a doctor blade without dislodgment from said cells, but each being selectively removable intact from individual cells under the influence of localized treatment,

a heat transfer original sheet having an indicia-receiving surface,

a substantially infrared transparent coating on the back of said sheet comprising a polymer-containing thermoplastic material having a latent specific affinity for the solid material filling said cells

said support and said original sheet being assembled with said coating of thermoplastic material operatively associated with said indicia-composing elements in said cells,

whereby infrared-absorbent indicia placed on said original sheet can be heated preferentially to raise the temperature of the thermoplastic material to an active state in areas directly underlying said indicia, so that, upon separation of the original sheet from the multicellular surface, composing elements from cells defining imaged areas corresponding to the indicia to be reproduced are selectively removed from the multicellular surface and are bonded to the coating on said original sheet which is thereby adapted to function as a relief printing member and whereby said support is thereby adapted to function as an intaglio printing member.

13. The composing unit of claim 12, wherein the solid material of said composing elements is a composition having a specified bonding affinity for a heat-softened thermoplastic material.

14. The composing unit of claim 2, wherein the solid material of said composing elements is a meltable resin.

15. The composing unit of claim 12, wherein the solid material of said composing elements is a fused plastisol.

16. The composing unit of claim 12, wherein the solid material of said composing elements is a cross-linked thermoset polymer.

17. The composing unit of claim 12, wherein the solid material of said composing elements consists of a mixture of thermoplastic and thermosetting materials.

18. The composing unit of claim 12, wherein said support is formed of a synthetic plastic.

19. The composing unit of claim 12, wherein said support is a polypropylene sheet.

20. The composing member of claim 12, wherein said multicellular surface contains in the range of from 10,000 to 160,000 individual cells per square inch substantially uniformly distributed over said surface, all said cells being of substantially the same depth and having a depth in the range of from about 10 to 50 microns, and wherein said cells are substantially uniformly separated from each other by the cell walls of the composing member with a separation in the range of from about 2 to 20 microns.

21. The composing member of claim 12, wherein all of the cells have substantially the same shape and dimensions.

22. The composing unit of claim 12, wherein said original sheet comprises a sheet of thin, lightweight paper coated on one side with a film-forming, polymer-containing, thermoplastic material.

23. The composing unit of claim 12, wherein said original sheet comprises a heat-resistant, near-infrared-transmitting, synthetic polymeric film coated on one side with a coating of film-forming, polymer-containing, thermoplastic material.

24. The composing unit of claim 12, wherein said coating has a thickness in the range of about 0.05 to 2.0 mils.

25. The composing unit of claim 12, wherein said thermoplastic material has an activation temperature above 50.degree. C.

26. The method of composing indicia to be reproduced, comprising,

providing a composing member comprising a support including a cellular printing surface formed of a multiplicity of uniformly distributed cells opening onto said surface, each of said cells being filled with an indicia-composing element of solid near-infrared-transmitting material which is capable of withstanding repeated exposure to a fluid ink and the wiping action of a doctor blade, but which is selectively removable intact from individual cells under the influence of localized treatment,

providing an original sheet having an indicia-receiving surface, the back of said sheet being provided with a coating of a polymer-containing, thermoplastic material,

said coating being adapted to bond, in areas underlying indicia placed upon said receiving surface, to the exposed surface of indicia composing elements filling the cells of the composing member, when the coated surface of the original sheet is placed in contact with the cellular printing surface of the composing member under the influence of localized heat and pressure,

recording indicia on the receiving surface of said original sheet to produce graphic representations highly absorptive of infrared rays,

superposing the indicia-bearing original sheet and the composing member,

exposing the superposed original sheet and composing member to infrared radiation to activate said coating in areas underlying said indicia, and

separating the original sheet from the composing member to thereby remove composing elements from selected cells defining imaged areas corresponding to the indicia to be reproduced, whereby said composing member is adapted to function as an intaglio printing member and said original sheet is adapted to function as a relief printing member.

27. A method in accordance with claim 26, wherein said indicia-bearing original sheet is exposed to an infrared source producing radiation in the range of from about 10,000 to 20,000 angstroms.