US2825282A - Letterpress printing makeready - Google Patents

Description

' March 4, 1958 J. B. GERGEN ET AL LETTERPRESS PRINTING MAKEREADY Filed April 2, 1956 Aime/v26 I most popular.

United States Patent O 2,825,282 LETTERPRESS PRINTINGMAKEREADY James B. Gergen, West St. Paul, and Thomas G. Wartman, St. Paul, Minn., assignors to Minnesota Mining & Manufacturing Company, St. Paul, Minn, a corpora- Thisinvention relates to the art of makeready especially as related to letterpress printing, to novel makeready methods and constructions, and to novel sheet material applicable thereto.

This application is a continuation-in-part of our application filed August 25, 1954, Serial No. 452,206, now abandoned.

I In letterpress printing, including flat-bed as well as rotary press printing, anirnpression cylinder or platen is commonly used to press a' sheet, usually paper, against the inked face (e. g., figures, designs, type, pictures, etc.) of a printing form. The face or image of. the printing form (i. e., the surface of raised printing elements) is thereby printed upon the sheet.

Many different types or styles of apparatusmay be used inthis printing operation. Printing forms may be mounted so as to rest upon-wood, honeycomb, or other types of bases. Impression cylinders or platens may be wrapped with several layers of packing materials, such as papers, cloths, draw sheets, etc. A suitable, but not necessarily exact, pitch or printing line is maintained for the operation. In describing this invention, all illustrations are taken with respect to flat-bed press printing using an impression cylinder, but it is understood that the teachings herein are not limited to any particular style of apparatus and that equivalent printing apparatus is equally suitable to employ.

For highest quality letterpress printing, certain preliminary steps are required in readying the printing apparatus for operation. Makeready is a part of this procedure and, as used herein, involves selectively varying the thickness of packing on various areas of an impressioncylinder, and/or adjusting the height of, or packing beneath, various areas of the face on a printing form so that the impression pressure under which areas of the cylinder and areas of the face of the printing form coact during printing is selectively adjusted.

Prior art methods of makeready are extremely time consuming, costly, and, for the most part, do not readily give results comparable to the'high quality obtained by the practice of this invention. They frequently require the use of messy materials, e. g., sticky ink, various powdery materials, etc., and in addition, individually suffer various other defects.

Among printers, the oldest known method of makeready, viz., the use of paper cutouts, dollies, etc., is the It has also been used to compensate for pressirregular'ities. While the method is susceptible of producing excellent results, it is very time-consuming and results obtained are entirely dependent upon the skill and technique of the printer. 1

This invention to a large extent alleviates the burden and expense of makeready and provides a new method for accomplishing it expeditiously, accurately, economically and mechanically, all as will be evident as this description proceeds. By the practice of this invention, makeready is accomplished with a high degree of fidelity lCC and in a manner which permits a number of printing establishments required to print the same subject matter at various locations to duplicate easily the precise corrections necessary.

Further provided by this invention are convenient makeready sheet materials which mechanically expand in selective fashion when processed according to the teachings herein, which have desired strength and toughness in selectively expanded areas, and which may be stored in the unexpanded state under ordinary atmospheric conditions without loss of their desired physical properties. These new sheet materials require no meticulous cutting for makeready use and permit makeready to be accomplished expeditiously and free of messy components, such as pastes, powders, etc., as required in the prior art. We know of no makeready sheetmaterials of this type which were commercially available prior to our invention.

By utilizing the makeready teachings herein, prints may be made which have delicate shadings, dense solids and clean highlights. Such prints, obtainable after only a short makeready time, are especially desired by publishers of encyclopedias, art magazines, and the like, where makeready has become an extremely time-consuming process. The various makeready constructions hereof give to printing forms a longer press life than heretofore experienced.

In describing our invention, we choose to refer specifically to makeready for graphic arts printing forms, but it will be understood that our novel process and sheet materials are also suitable to employ in making ready,

or as makeready for, other printing forms. 7

Fundamentally, theoretical explanations aside, to provide appropriately corrected impression pressures for highest quality graphic arts printing, the relative thickness of packing over solid tone areas must, with respect to the thickness of packing over middletone areas, be increased. Additionally, however, the thickness of packing over the peripheral area of solid'tones generally should be less than that over central areas thereof, and further, the thick.- ness of packing over middletone areas having a very high density of dots or printing elements should be comparatively greater than that packing over middletone areas having a very low density of dots or printing elements. course, as evident from the above, the relative height of, or packing beneath, areas of solid tone may be raised-or increased relatively to areas of middletone to accomplish also a suitable correction for printing. Highlight or nonprinting areas of a printing form should receive least pressure in printing and therefore should generally have the least packing. 1

Variation of the thickness of packing on an impression cylinder involves overlay makeready. Corrective ma.- terial inserted beneath the mountingblock on which a printing form rests is underlay makeready; Interlay makeready involves placing corrective material beneath the printing form, e. g., an electrotype, but above the mounting block on which it rests. Adjusting the height of various areas on the face of a printing form may involve a bump-up process such as hereinafter described. According to our invention, a makeready sheet material having a flexible selectively-thermoexpansible layer which is resistant to compression in expanded condition, is inked or printed with the general likeness of a printing'form, exposed to radiant energy for diiferential sustained expansion, and finally, placed in registration with a printing form. The processed sheet material essentially provides the amount and kind of makeready correction needed to Figure 2 ,is a diagrammatic, section through a portion of a printing form and an impression cylinder wrapped with our makeready sheet.

Figure 3 is a diagrammatic section through a source of high-intensity radiant energy and a makeready sheet selectively expanded in part.

Figure, 4 is a diagrammatic section through a portion of a printing form and an impression cylinder having a selectively-expanded makeready sheet in registered overlay position.

Figure 5 is a diagrammatic exploded sectional view illustrating two squeeze rollers, two metal plates, and a laminate comprising a negative selectively expanded makeready sheet, a printing form, and a positive selectively. expanded makeready sheet l(here shown slightly outof register-L1.

Accordingto the preferred embodiment of our process, designated for brevity as the overlay process, the selectively-thermoexpansible. layer or side of. n r ayyp makeready Sheet non-absorptive of radiant energy, e. g., a sheet such as illustrated in Figure 1 comprising a carrier web 20. and a selectively-thermoexpansible layer 21, is first inked or printed upon with a radiant energy absorptive ink This may be accomplished in the manner illustrated in Figure 2. t Sheet: 22 with its heat-sensitive layer 21 outermost is fastened around impression cylinder 23 over several layers of packing 24, which provides adequate overall general impression pressure. Printing form 25, e. g., an electrotype, supported onmounting block 26, is inked and the wrapped impression cylinder rolled thereover. Desirably, the, position of the resulting printed sheet on cthe impression cylinder is now marked, suitably by. punching a few holesthrough the leading or front edge of the sheet and several layers of cylinder. packing, so as to facilitate its subsequent registration.

After. initial .printing, the makeready sheet is removed from the impression :cylinder and briefly exposed to uniform and intense radiant energy. Figure :3 illustrates one way for accomplishing suitable exposure. In this figure, sheet material 22 with inked layer 21 toward highintensity radiation source27 in elliptical reflector 28, is moved to the right, as indicated by the arrow, through narrow focused band 29 of radiant energy. In those areas to the right of band 29, the sheet is illustrated as selectively expanded according to the pattern of infrared absorption shown as inked thereon. Solid tone printed area 30is greatly expanded, while middletone printed areas 31 and 32 of proportionately less printing point densityare expanded only to a degree approximately commensurate with their tone. Unexpanded printed areas 33, to the left of the focused band or line 29 have-not yet been exposed. Non-printed areas 34are unexpanded.

In this exposure step, ink on the makeready sheet absorbs radiant energy, becomes heated, and in turn heats areas of the selectively-thermoexpansible layer of resinous material andpuffing agent adjacent thereto by conduction. These areas soften, the pulling agent in the sheet is activated inthe soft areas under conditions of heat, and the gas of the puffing agent produces bubbles in the softened areas causing themyto, swell. The thermoexpanded areas are then allowedto cool andgenerated gas remains entrapped. in the expandedareas of. the layer. Local areas of theprinted sheet which have a high ratio of inked surface, .i. e., solid or black tone areas, absorb a greater amountof radiant .energyand cause a greater amount of gas formation by thepuffing agent thanareas where this 'atiois small, e. g., middletone areas. Areas of the sheet not printed, i. e., highlight areas, do not absorb radiant energy or do so only to a slight. extent insufficient to effect expansion thereof. Theflresulting .sheet after exposure has .a thickness relief corresponding to the tone of the. printing form, being thickest in solid tone areas (and of greatestthickness in the center of such areas),thinnest '4 i a t in non-printing orhighlight areas, and of essentially graduated thickness between these extremes.

Conditions of radiant energy exposure are especially detailed in the disclosure set forth in connection with Example 1. It will be noted that exposure to intense radiation is brief to prevent char-ring of the selectivelythermoexpansible layer, and that intense and uniform radiation is necessary to achieve high and selective expansion of the heat-sensitive layer before any significant dissipation of heat has a chance to take place therethrough. While heat-sensitive, our expansible layers are poor conductors of heat.

After exposure, the sheet is returned to the impression cylinder and registered with the printing form, as for example by matching the punched holes in the underlying packing and the makereacly sheet. In an ideal overlay construction, the makeready sheet is placed beneath two or three layers of heavy packing paper (each layer being approximately 0.006 thick). The sheet preferably is not buried too deeply in the packing on the impression cylinder inasmuch as the tendency is then to upset desired registration. The outermost layer on an impression cylinder ready for printing suitably may be a printing blanket or the like, as is well known in the art. However, the makeready sheet itself may be used as the outer layer, if desired.

In Figure 4 a makeready sheet hereof 22 is illustrated in registered position beneath one layer (chosen for clarity of illustration) of packing 2411 upon impression cylinder 23. A layer of packing 24b is positioned beneath the makeready sheet. Selectively expanded areas 30, 31 and 32 of sheet 22 coact during printing with solid tone area 35 and middletone areas 36 and 37, respectively, of printing form 25, mounted on a suitable support 26. Apaper sheet 38 is illustrated receiving the inked image of the printing form.

Our complete overlay makcrcady process may be accomplished in as short a period as 10 minutes as compared to prior art processes requiring, in many cases, an hour or more. One of the largest expense factors about makeready, i. e., printing delays or press down-time, is therefore greatly reduced.

If desired, overlay-typc sheet'materials processed according to the foregoing may be registered for underlay or interlay makeready constructions. In such constructions, the carrier web side of the sheet is positioned next to the underside of the printing formior the mounting block), and the selectively expanded layer lowermost.

The following examples are illustrative but nonvlimitative of our invention. For convenient reference, the various characteristics of the sheet materials of Examples 1 through 7 are tabulated below in Table I. All of the sheet materials of Examples 1 through 7 were processed usingour overlay makeready process, and placed in registration beneath two layers of 6 mil (0.006) packing on an impression cylinder. Printing done on commercial appartus with such makeready constructions gave prints of exceptionally fine quality. Solid tones, were dense, highlights clean and middletones delicately shaded according to thedensity of printing elements, as desired.

EXAMPLE I 1 Parts by weight Cellulose acetate butyrate Polyvinyl acetate t 90 Plasticizer u 39 Solvent 500 Paste -c- 12.8

The cellulose acetate butyrate'was obtained under the trade name /2 Second Butyrate," which is a low viscosity but hard cellulose-derivative thermoplastic resin, having a melting range of approximately 284-338 F i, an intrinsic viscosity in acetone at 25 C. of approximately 0.66 to 0.86, a molecular weight of approximately 30,000. an

acetyl content between approximately 12 to 15 a butyryl content of 35 to 39%, a hydroxyl content of 0.5,to 1.2%, a free acidity content of approximately 0.03 maximum, and a maximum moisture content of approximately 3%.

The polyvinyl acetate was Vinylite AYAT, which has an approximate softening point of 187 F., an intrinsic viscosity in cyclohexanone at C. of 0.69, and a specific gravity of 1.18.

The plasticizer was Paraplex G-20, which is a 100% sebacic acid ester type polymeric plasticizer containing no modifying oil. The solvent was a mixture of 40 parts toluene,9 parts ethanol, and 1 part normal butanol.

The paste was made by milling the following consti tuents on a paint mill into a uniform blend:

, Parts Puffing agent 2 Plasticizer 2 Solvent 1 The puffing agent, Celogen, was p,p-oxy bis (benzene sulfonyl hyorazrde), which decomposes at raised temperaturesbeginning at approximately 266 F., releasing nitrogen gas. The plasticizer and solvent in the paste were the same as those constituents in the resinous mass of this example. 1

The components above, other than the paste, were stirred together until a smooth solution was obtained. To this solution was then added the paste and stirring continued until a uniform blend resulted. About 17 additional parts of solvent were then added to the mass to reduce its viscosity and the blend then coated on 42 pound Minniform paper (a bleached Kraft converting paper) marketed by the Minnesota and Ontario Paper Company. A wet coating thickness of approximately 20 mils (0.02) was employed. Some. impregnation ofjthe paper backing resulted. The coating was dried for approximately-one half hour at room temperature and then for approximately ten minutes at 160 F. and finally for approximately twenty minutes at 225 F. The steps employed to accomplish drying were for the purpose of removing as completely as possible all solvent and moisture from the coating. In addition the short heat conditioning treatment of approximately twenty minutes at 225 F. served to smooth and density the coating and thereby impart increased moisture resistivity to the, sheet. 1

The resulting sheet was inked with the pattern of a printing form using conventional oil base carbonfpigment printersink. The ink wet the smooth resinous surface uniformly and remained effectively distributed in the pattern of the face of the printing form employed. The inked sheet was then briefly subjected to uniform and intense radiant energy. l

The source of radiation employed was a tungsten linefilament lamp mounted lineally in a sealed quartz tube; however, equivalent sources may be used. At 230 volts the lamp had a capacity of 650 watts. The tube was mounted along the. axis of the internal forms of an elliptical reflector having a focal distance of 0.852inch. The other focal axis of'the reflector was in the open, i. e., outside the boundaries of the reflector. The inked makeready sheet was rapidly passed in front of the'reflector in the plane of the external focal axis, with the concentrated line of radiation thereby being focused on a narrow strip of the printed surface. The width of the line concentration of focused rays was approximately three-sixteenths of aninch. a Y

The temperature of the radiation source, as measured by an optical pyrometer, was 2460 Kelvin at an input of 300 volts giving 970 volt-amperes. Under these conditions the makeready sheet, resting on an insulating blanket, was passed twice below the light source at a speed of 80" per minute. IHad the sheet been passed beneath this source at a speed of approximately 20" per minute, charring of the sheet would have resulted.

In solid tone areas the sheet expanded to a total thickness of approximately 10.7 mils, 3.2 mils above areasof the sheet not expanded. Other areas, such as middletone areas and highlight areas, expanded to a degree commensurate with the darkness of their tone, nonprinting areas remaining unexpanded. For example, in a middletone area of 20% printing elements nonprinting or clear) the sheet expanded to approximately 8.1 mils, 0.6 mil above non-expanded areas. The processed sheet, in other words, presented a thickness relief corresponding to the tone of the printing form.

If a source intensity of radiation, i. e., infrared or equivalent, is too low during processing, insufficient expansion of the sheet results, or the sheet expands in a generally non-selective fashion. If a source intensity of radiation is too high, the makeready sheet hereof chars and loses its value as a corrective sheet in printing. For example, at a source temperature of 2310 Kelvin at 250 volts giving 720 volt-amperes, the printed sheet of this example was passed three times through the line focus of radiation at 60 inches per minute. 1 he resulting selectively expanded sheet was barely suitable for use in print} ing. Its pattern of expansion was not as accurate in relief as that pattern exhibited by the sheet expanded according to the preferred conditions of radiation hereinbefore set forth. At a filament temperature of 2700 K. at 375 volts giving 1350 volt-amperes, the sheet of this example was passed three times at a speed of inches per minute through the line focus of irradiated rays. Despite the rate at which the sheet was processed, expanded areas were charred. While solid tone areas of this sheet were expanded to approximately 4.5 mils above the 'surfaceof the sheet, they were charred and could not withstand any great printing pressures.

The sheet materials of Examples 2, 3 and 4 were processed using the preferred conditions of exposure set forth in this example.

The thermosetting resin employed was an epoxy condensation polymer of epichlorohydrin and bisphenol A commercially available under the designation BR- 18774, which consists of 100% solids having an epoxy equivalency of 180 210, and a viscosity at 25 C. of 10,000 to 15,000 cps. The solvent was a mixture of 40 parts toluene, 9 parts isopropyl alcohol and 1 part normal butyl alcohol.

The ingredients above were added to the solvent in the order listed and stirred until a uniform blend resulted. The blend was then knife-coated with an orifice of 0.025 inch upon 42 pound Minniform paper. The coating was air-dried at room temperature for approximately onehalf hour, oven-dried for approximately '20 minutes at F. and then'20 minutes at 225 F. The raised temperature of drying'advantageously served to condition the resinous coating so that it became less moisture sensitive and to efiect curing of the thermosetting resin.

We haveemployed a wide variety of puffing agents in makeready sheets such as set forth in the example. An intimate mixture of urea and biuret, which decomposes at approximately 300 F. releasing ammonia, has been employed. Potassium bisulfite has been employed. Even small quantities, e. g., on the order of 3% by weight, of

ammonium aluminum alum, which releases. its water of hydration at approximately 248 F., have been employed,

EXAMPLE 3 Parts by weight Polyvinyl butyral 100 Plasticizer of Example 1 2O Toluene -4 180 Isopropyl alcohol 120 Puffing agent of Example 1 6 The polyvinyl butyral employed here was obtained under the designation Butvar B76, which is produced by liydrolyzing polyvinyl acetate to polyvinyl alcohol and reacting the alcohol with butyraldehyde to give polyvinyl butyral. It has a softening point of 170 F., a hydroxyl content of approximately 13.0% (calculated aspolyvinyl alcohol) and a polyvinyl acetate content of approximately 2.5%.

The above ingredients were mixed together until a uniform blend resulted. This uniform blend was coated on 42 poundMinniform paper in a manner as set forth'in Example 2, the coating dried to a tack-free consistency at room temperature, and thenovendried for'approximately 20 minutes at 150 F. and 20 minutes at 225 F.

EXAMPLE 4 Parts by weight Hard polystyrene resin 35 Toluene 65 Pulfing agent of Example l 1 The hard polystyrene resin employed in this example was' an unmodified polystyrene sold under the trade name Styron 666. According to tests of the American Society for Testing Materials, it had a tensile strength of 6,000to 7,000 p. s. i. (ASTM D638 49T), an'elongation of 1.5 to 2.0% (ASTM D638-49T), a flexural strength of between 12,000 to 15,000 p. 's. 'i. (ASTM D790-49T), a heat distortion range of 168 to 175 F.", (ASTM D 648-45T), and a Rockwell hardness of M68- 80 (ASTM D785-48T). i

To the solvent, toluene, was added the polystyrene polymer in particle form and stirring continued until the polymer was uniformly dissolved therein. The puffing agent was crushed to a particle size of approximately 1 mil or less and dispersed, i. e., blended thoroughly in the solution by stirring. AWaring blendor may suitably be employed.

The resulting blend was coated, using anorifice 0.020" thick, upon.90 lb. fourdrinier paper commercially available under the trade name Sanfast. A heavy backing is necessarily used with the cxpansible resin-layer of this example inasmuch as the non-plasticized resin layer of this example exhibits a relatively hightende'ncy to cause curling when coated upon relatively thin light weight backings. After being applied to the heavy backing, the resin coat was air ried for approximately one-half hour at room temperature and then oven-dried for 20 minutes at 150 F., followed by 20 minutes at 225 F.

EXAMPLE.

Gram parts'by weight Vinyl. chloride-vinyl acetate copolymer- 1200 Plasticizer 4S0 Amyl. acetate 624 Volatile petroleum naphtha .J. 680 Puffing agent of Example 1 30 The vinyl chloride-vinyl acetate copolymer was an mgm. of KOI-I/gm. The naphtha used has a specific gravity (6 0,"F.=/60f F.) of 0.733 to 0.735..

All ingredients. above except the putting agent were added to a 2-gall on jar half filled with porcelain balls of approximately one-halfinch diameter. The jar was rolled for about 16 hours to thoroughly mill the contents, after which the pufiing agent was added and milling continued for an additional 2 /2 hours. Milling time and conditions may vary depending upon the type of container employed, the size of hard balls used, etc.

The organosol mixture thus prepared was knife coated at a thickness of mils upon a 3-mil thick brass foil, the surface of which had previously been roughened with sandpaper. The coating was dried for 2 minutes at 180 F. and fused for 5 minutes at 260 F., a temperature below the decomposition temperature of the.

pufiing agent.

The resulting sheet was printed and heated to approximately 180"F. as measured bya surfa'ce pyrometer at the metal surface. The heated sheet was then exposed to radiant energy using conditions of actual exposure slightly less severe than those set forth in'Example 1, resulting in the formation. of a high graduated relief pattern in the resinous layer. Preliminary heating of a heat-conductive metal-backed sheet to an ambient temper'ature above approximately Fjbut below the decomposition point of the pufling agent incorporated thereinis believed to reduce lateral dissipation or transfer of. heat in the backing during exposure to radi a nt energy, whereby erratic or poor expansion of the resinous layer of the sheetis avoided. i

EXAMPLE 6 A flexible non-woven fabric support 4 mils thick, formed by fusing randomly oriented fibers consisting of approximately 40% non-thermoplastic viscose (reget'r erated cellulose) fibers and approximately'60% thermoplastic cellulose acetate fibers, was impregnated with the organosol'resin dispersion of Example 5 using a 3 mil orifice. This impregnating coating was air-dried for a few minutes at room temperature, anda second coating knifed thereover using a 20 mil orifice. The'structure was then dried for 24 hours at room temperature.

The resinous layer of this sheet contained tiny discrete particles coherently held together. They could be crumbled from the sheet by rubbing the structure briskly, but under actual conditions in printing; did not flake, split, crack or become displaced. Using conditions of exposure to radiant energy set forth in Example 1, printed areas of the particulate layer, i. e'., those inked ar'e'as absorptive of radiant energy, selectively fused into a tough, continuous phase. Highlight areas or non-inked areas not absorptive of radiant energy remained in an unfused state. Decomposition of the pulling agent took place at a point slightly above the point at which the particulate resinous layer fused; therefore, generated gas remained entrapped within the layer giving the desired graduated relief. pattern.

Porous fabric backing members may be impregnated with any suitable material prior to coating. Makeready sheets having highly porous support. members impregnated as well as coated with our resinous masses may be inked upon either side and exposed to radiant energy to form an appropriate relief for makeready.

EXAMPLE .7

Gram parts by weight Vinyl chloride-vinyl acetate copolyrner of Example 5 .L 50

Adipyl dihydrazide has a melting point of about 350F., and at raised temperatures, i. e., temperatures near its melting point, is a highly effective curing agent for epoxy resins. it is inert in this resinous mixture at room'temperatures. Instead of adipyl dihydrazide, 2,4-toluene disulfonamide, malonyl dihydrazide, or other heat-activatible curing agents for epoxy resins may be employed. Malonyl dihydrazide acts not only as a curing agent for epoxy resins but also as a pufling agent.

The pufling agent used here, available under the name Celogen AZ, releases nitrogen gas on heat decomposition starting at about? 85 F.

The ingredients above were milled together using th method of compounding set forth for Example 5, and knife-coated upon a backing of the type used for Example 1 with a 17 mil orifice. The coating was dried for about 6 minutes at room temperature and fused at 275 F. for three minutes. The uncured epoxy resin in the coating served to plasticize the vinyl resin. I p

This makeready sheet was processed using conditions ofexposure only slightly less severe than those employed for the sheet of Example 1. During processing, the heat generated in selected areas absorptive of radiant energy was 'sufiicientto partially cure those areas of the sheet,

thereby enhancing their expanded strength. Other areas not absorptive of radiant energy, and not therefore heated, remained uncured. If desired the epoxy resin in such areas may be cured by a short heating step just below the temperature of decomposition of the pulling agent. In the following table various characteristics, as identified, of the foregoing makeready sheets are tabulated.

Table I Example 1 t 2 f 3 f 4 I 5 6 7 (1. Thickness of backingin mils (thousandths of an inch).

0. Total mil thickness of unexpanded dry sheet material.

0. Thickness of selectively thermoexpansible layer (ba).

it. Total thickness o sheet material in maximumly expanded areas, i. e.. solid tone areas. measured at room temperature after processing according to the teachings herein.

a. Differential in thickness between maximumly expanded areas and the initial thickness of the sheet or unexpanded areas (db).

f. Total mil thickness of processed sheet material in maximurnly expanded areas under a pressure of 250 p. s. l. for 15 seconds at room temperature.

a. Diflerential in thickness of processed sheet material between maxi murnly expanded areas under a pressure of 250 p. s. i. for 15 seconds at room (tfggerature and the initial thickness of the sheet or unexpandecl areas h. Weight percent of dissolved water in the unexpanded selectivelythttirmo ei pansible layer after conditioning for three days at 56% R. H. an 75 1. Weight percent of dissolved water in the unexpanded selectivelythedrriogei pansible layer after conditioning for three days at 93% R. H. an a In the foregoing examples we used solution or dispersion coating methods to fabricate our sheets; however, other methods such .as calendering, extruding, etc., may be used. The important requirement is that the resulting coat must be at least about 2 mils thick over the entire backing member or carrier web and should be of essentiallyuniform thickness. Any suitable method may be used to accomplish this result.

Small amounts of various inert fillers and materials, for example, aluminum powder, calcene, silica fines, bentonites, etc., may be'incorporated in a uniformly dispersed condition in the resinous layers of our sheets.

Our sheet materials may be characterized as essentially of uniform thickness and as flat-lying in that they remain substantially flat'and-resist curling, warping, etc., during. processing. Overlay-type sheets such as those of the foregoing examples are preferably not more than I under a pressure at least as high as approximately 250 v 10 I about 12 mils thick for the reason that more accurate control of the desiredpacking and of registration on an impression cylinder is possible with such sheets.

. The carrier web is dimensionally-stable or planarlystable in that it imparts planar stability, i. e., resistance to curling, warping, stretching, etc., to the makeready sheet. Registration of the sheet material after processing is thereby easily accomplished. In the most ideal sheet structures, the backing member is' between approximately 2 and 5 mils in thickness. Other flexible backings than those set forth in the examples may be employed. For example, non-fibrous films of glycol-terephthalate polymer v (Mylar), cellulose acetate, silk screens, various metal sheets or foils, various laminates of materials, impregnated materials, etc. are employable. At least one surfaceof the backing material is preferably of a sufficiently fibrous nature for anchorage of the selectively-thermoexpansible' resinous layer thereto; however, smooth surfaced backing sheetsmay be roughened to secure adhesion or bonding of the resinous layer thereto, as illustrated in Example 5, or an interposing layer of adhesive maybe used to firmly bond the backing and resinous layer together. i

Preferred overlay-type sheets hereof have backing members characterized as of low heat conductivity, particularly if compared to the conductivity. of metals, so that lateral diifusibility of heat through the backing support from limited localities thereof 'aifected by heat in adjacent portions of the adhered resinous layer during processing is minimized. ,We may, however, as in Example 5, employ thin flexible heat-conductive metal backing members. Metal backings. inherently possess desirable properties of strength and dimensional stability.

Backings are. preferablylight in color for the reason that manydark colored backings coated with translucent layers absorb infrared rays. We realize, however, that dark colored backings maybe used and a highly reflective or opaque resinous coating employed or a' different range of radiant energycmployed, to selectively expand the sheet according to selective absorption by a special inkfhaving absorptive powers for the particular rays employed. This we consider'an equivalent of our inven-' tion. i H 7 Likewise, although in the preferred embodiment our sheets are printed with inks having'high absorptivity for infrared rays, e. g., black ink, we may employ other inks having absorptive qualities for a different range of radiation than infrared rays and use resinous layers and backings which donot absorb these rays, or which do so only to a slight extent. This, also we consider an equivalent.

The resinous material in our, selectively thermoexpansible layer is usuallypolymeric and must be thermosoftenable as may be noted from the examples and illustrations hereof. Preferably, at least one hard hydrophobic thermoplastic polymeric material is employed in making up. the; layer Materials having a Shore D Durometer hardness above 40 are generally preferred,

but sucha hardnessvalue is somewhat misleading inasmuch as softer-materials whichare thermosetting or' curable to suitable hardness in processingmay be used. Resinswhich are thermosetting but temporarilythermoplastic,which areQthermoplastic and .vulcanizable, as well as others and .iriivariouscombinations-all are employable if in the; final coat after heat'softening, 'pufiing'and cooling, the selectively"expanded resinous layer is non brittle (particularly as compared to abietic acid or rosin) and possess'essufiicient hardness, resilient strength and toughness to resist'flattenin'g in use, e. g., to maintain approximately a '2 mil differential in thickness between (a) fuliyor maximumly expanded areas after 15 seconds p. "s. i. (lbs/in and (b) those areas of the sheet not expanded. Such conditions of time and pressure are believed to closely approximate those encountered under most actual printing conditions;

Also. employablei together inthe layer are resins. and other components which are incompatible, but which after drying, do not sublime or'migrate from the'layer.

A coating of non-. compatible resins and other components may be heated slightly to. improve the dry stability thereof. Preferred selectively .thermoexpansible layers have a uniform smooth fusedappearance, but, as illustrated in, Example ,6, our layers may be comprised of. aplurality of individual particles. 1

Preferably he dry thickness of the selectively thermo expansible layer inmakeready sheets especially designed for overlay use is between, approximately 2 and 7 mils u be as g satas 12 mils, or. gr ater, with satisfactory results. By dry we mean normally less than, about 3% vola o anic solvent by we h so as. to prevent ckin ots clsq she s nd so as to avo unnecessary s knsss siui'th la e u onsxpansion- A thi kness o at least 2 mils s ne ded it tel raduat d r ie p rns ar i he ormed- Thinner coa fail to xpan e ab an even los an q l'fit t e n Qur y rs generally contain small amounts of orgapiqusually pplymeric; plasticizers for their thermoplastic resipous components se the adva taswu planar s ab y, ed of tcadsa y to 9 a d rar aswsl as n some cases iiicreased moisture resistance, imparted to the resulting layer. Plasticizers, however, almost'invariably Somewhat l e na d St en h of a r sinous a er- Accordinglyjthe layer'of such sheets is generally at least about 3 mils thick, and usuallybetween 4 and] mils thick for best results in terms of maintaining suitable expanded thickn'essditferentials under psessure'l Layers greater than approximately 12' mils thick are generally undesirable ,becausee'xpanded areas are apt to bejdis placeable under compression, and desired high" differentials in thickness areapt to bereduced because of, the greater relative compressibility, of .such thick coats. This disadvantage of thick coats or layers may be corrected to some extent by incorporatingtherein suitable curing agents or thermosetting resins;

The dispersed, heat-sensitive, normally dormant, putting agent in the ,selectively-thermoexpansible' layer re mains therein in a storable, stable condition. It may, in fact, react with the resinous mass, cure it, or even'be a molecular component of a resin,:' so' long'" as'jit retains its requiredability toexpand the layer under conditions of heat. Finely pulverized," uniformly dispersedfparticles of a putting agent facilitate the formation of a large number of tiny bubbles of cavities in. the resinous layer, with a greatnumber of connecting columns of resin, all of which contributes to .the strength and resiliency of expanded areas, as well as to the formation of'wellregulated graduated reliefpatterns. v i

The amount of putting agent employed may vary depending: upon the relative ability of the agent to expand the sheet under, conditions of heat employed in processing. A resinous layer may contain as little, as approximately 1% by weight of a highly efficient puffing agent, e. g. Celogemi but may require up to approximately 30% by weight of a less efficient agent. Amounts in excess of approximately by weight are generally to be avoid ed inasmuch as certain weaknesses are :apt to develop within thegsheet. Howeveryan inetficient putfingagent which contributes to the strength of thesheet may be suitable to employ in high concentrations. Preferred puffing agents chemically decompose at raised temperatures to give otfja gas; however, materials. or puffing agents which act by vaporization on heating, as opposed to decomposition, whileinferior, maybe suitable to use.

The preferred temperature range at, which expansion, of r at-Smith make sv s e s cur is we l.

b v m t mper ure-a is be een app o im s y 150 F. and 3509, F.,.but may be as high as4 50 E, or of, even eonsiderably higher. Expansion at exceedingly was? low temperatures is generally unreliable and not controllable; on the other hand, expansion which does not occur until exceedingly high temperatures, i. e., those for example over about 450 or 500 F., are attained creates problems with respect to suitable exposure conditions for processing as well as with respect to obtaining suitable graduated relief patterns. l l

The temperature at which our resinous masses soften and the temperature at which a polling agent incorporated therein gives off gas should generally be within approximately the range of 75 F. of each other, although for some less critical combinations, a temperature difference as great as about F., or even greater, has been found useful. ,Generally, however, it has been found that if a pufiing agent generates gas at a temperature too far below that at which a resinous layer softens, control of expansion becomes difficult and desired graduated reliefpatterns are not easily obtained. If, on the other hand, the putting agent releases gas only at temperatures greatly above those at which the resinous material softens, dimculty arises with respect to maintaining the released gas within the softened resinous layer so as to expand the same. The faults of extremes are easily avoided if materials are selected with a view toward maintaining the activation temperature for the putfing agent reason ably close to the softening temperature of the resinous layer;

The selectively-thermoexpansible layer. of our sheets has a prolonged shelf life and may be characterized as hydmphobiclin thatit resists imbibition of water or mois ture to an extent that it does not contain sufiicient dissolved water, even after being stored under atmospheric conditions, to interfere greatly with thegaining of high, graduated, tough and sturdy relief patterns when it is. later exposed to radiant energy during processing'fas: taught herein. The foregoing definition for the required, hydrophobic nature of our heatexpansible layers, isfai' more accurate than quantitative figures on their maximum permissible moisture content; although, wheni us ing such a standard, the heat-expansiblc layer of our sheets does not contain, even when exposed for lengthy periods to especially adverse conditions of temperature and moisture, more dissolved water than from 0 upto 4% by weight. Expansible layers which contain more than about 4% Watcr'by weight give unreliable results in expansion and erratic relief patterns, frequently of greater thickness in middletone than solid tone areas, when made heat-sensitive and processed as taught herein. In Table I qualitative data as to the dissolved moisture content in the selectivelyethermoexpansible layers of the foregoing examples is set forth. Particulan note should btakcn of thoselow values obtained when the articles of the examples were stored under high humidity condi-.

tions such as might be encountered in summer months.

The surface of our selectively expansible layers may be characterized as lyophilic or organophilic in that it accepts conventional printing inks readily and is not deleteriously affected thereby, even though the printing inks contain oils and the like. The ink receptive nature of our selectively expansiblelayers may be appreciated when it is realized that, areas inked upon our sheets are not significantly altered in shape by such phenomenon as surface tension which may cause an inked area to pullup into globules. Instead the ink wets the resin surface and remains in position upon the sheet substantially, as it was originally applied. Cur, sheets; after. processing do not flake, split, crack, become pulverized, or exhibit cold flow under conditions of use. We believe that the selective and. proportionate resiliency, toughness, and strength of our. selectively ex.--

pended layers, including their ability to. resist. crushing and displacement as Well as flattening compressive forces such as are encountered in printing, i. e., presspoundingj? accounts in a large measure for the, especially,v fine.

13 printing results obtained when our sheets are employed as taught herein.

According to another embodiment of this invention, there is provided a novel process and also makeready sheet materials for bumping-up or distorting electrotypes, photoengravings and the like in a very accurate manner for appropriate impression pressure corrections in printing. In a bump-up plate treatment process, a positive paper cutout relief sheet with dark tones raised is registered under a printing form, e. g., an electrotype, and a negative paper cutout, i. e., one with highlight tones raised in relief, is registered over the electrotype. This laminate is then placed between rigid metal plates and the resulting laminate passed between squeeze rollers, which action deforms the electrotype, raising dark tones relatively to highlights. The so distorted electrotype is shaved smooth on its back surface before the negative sheet is removed, and thereafter, is mounted on a suitable base for printing.

Example 8 illustrates this specialized embodiment of our invention. As will be evident, the general characteristics of overlay sheets above set forth are also applicable 7 to sheets of this embodiment of our invention. The sheets of this embodiment, however, possess a greater strength in expanded areas.

EXAMPLE 8 Parts by weight Epoxy thermosetting resin of Example 2 6O 2,4-toluene disulfonamide (Epoxy curing agent) 8 N-(3 diethylaminopropyl) phthalimide salicylate (Activator for epoxy curing agent) 0.7 Vinyl chloride-vinyl acetate copolymer of Example 80 Amyl acetate 80 Naphtha of Example 5 60 p-Diphenyldiazonium fiuoborate (puffing agent) 4 For the positive sheet, the above ingredients were milled together to form a uniform dispersion by following the method of compounding set forth in Example 5.

For, the negative sheet, the same ingredients, quantities and process were used except that 2 parts by weight of activated carbon black (Carbolac #2") were added to the mixture about 1 /2 hours before milling was termi nated. Instead of using a pigment absorptive of radiant energy, we may use a radiation-absorbent backing or carrier web with a transparent coating and thereby attain an equivalent sheet.

Each dispersion was then knife-coated on a separate carrier web of the type used in Example 1 with 18 mil orifices. be used. The coatings were dried minutes at room temperature and 15 minutes at 150 F. 'The driedcoatings remained in an unfused state; however, the vinyl chloride-vinyl acetate copolymer particles in the dried layer were swelled by what appeared to be a plasticizing action on the part of the uncured epoxy resinin the coating, and the swelled resin particles seemed to be bonded to each other by the epoxy constituent in ,the layer. The dried sheet was about 8.5 mils thick, 3.5 mils of which was backing.

The dry positive sheet was inked with an impression of the electrotype to be bumped. Black ink pigmented with carbon-black was employed. The negativesh'eet was inked also with an impression of the electrotype but Other backings as discussed hereinbefore may in this case a radiation reflecting or non-absorbing ink was used. Silver ink having a reflective silver or aluminum pigment is satisfactory. Each sheet was then exposed to brief, intense and uniform radiation. Suitably, conditions only slightly less severe than those described in Example 1 are employed. The processed sheets of this example in max'imumly expanded areas were 14.5 mils thick, 3.5 mils of which was backing, and these areas supported pressures of about 100 p. s. i. for 15 seconds remaining at least about 5 mils above areas not expanded. No oven curing was necessary to achieve such strength 14 I r in the selectively expanded layers of this example, but an oven curing step may be used if desired.

The p-diphenyldiazoniurn fiuoborate functioned during exposure of this sheet not only as a pulling agent but also as a curing agent for the epoxy resin in those selected areas heated. Other such agents are p-aminodiphenyldiazonium fiuoborate, p-toluene diazonium fluoborate, etc.

Referring now to Figure 5 for illustration, the positive sheet 39, inked with radiant energy absorptive ink 40 and 41, increased in thickness in those areas, the greatest increase taking place in solid tone area 40. The negative sheet 42, inked withradiant energy reflective ink 43 and 44, increased in thickness in non-inked areas 45 and 46, and exhibited the greatest increase in area 45 on which no reflective ink was printed. The hard and tough cured sheets were each in relief form; however, the relief of the negative sheet 42 was the reverse of that of the positive sheet 39. The positive sheet 39 was then registered underneath the electrotype 47, and the negative sheet 42 registered above the electrotype. This laminate was then placed between rigid metal plates 53 and 54 and the resulting laminate passed between squeeze rollers 48 and 49. By this process, the electrotype was distorted, i. e., bumped, in extremely accurate detail. Solid tone area 50 was raised relatively to highlight areas 51. Likewise middletone area 52 was raised relatively to highlight areas 51 but was not raised to the same relative degree that the solid tone area was raised. The electrotype was, in other words, given a relief distortion. The positive sheet was then removed, the back of the electrotype was leveled, i. e., shaved smooth, and the negative sheet removed. Prints made using this treated electrotype in suitable well-known printing arrangement were of the exceptionally fine quality aforediscussed.

The resistance to moisture imbition of the sheet materials of this example is as follows: In a test for 3 days at 56% R. H. and 75 F., as well as in a test for 3 days at 93% R. H. and F., the selectively thermoexpansible layers in each case contained less than 0.5% by weight dissolved water.

Great strength is required in the expanded portions of these positive and negative sheets. The strength of the expanded areas, usually cured, is sufficient to support at least 1,000 p. s. i. for 15 seconds and still remain at least more than 2 mils and generally at least approximately 5 mils above the unexpanded portions of the sheet. These sheets therefore, are the more unusual when it is realized that such strength is gained in vesicular expanded portions. While these sheets may also be used as overlaytype makeready sheets, they frequently possess more than the desired strength for usual overlay makeready requirements.

Our negative sheets, i. e., sheets hereof which are absorptive of radiant energy and are processed using refiective inks to mask out areas not to be expanded, may be used also in a bump-up process without the positive sheet, if desired. In such a process, the negative sheet is printed with the pattern of the electrotype using a reflective ink, and thereafter, it is exposed to radiation, as herein taught, and registered over the electrotype. Next, pressure is applied over all points or areas of the back surface of the electrotype to distort it toward and according to the relief of the negative sheet. The back surface of the bumped up electrotype is then shaved smooth and the resulting corrected electrotype is ready for printing.

In another embodiment of our invention, both sides of a carrier web are coated with a selectively-thermoexpansible layer. To selectively expand both sides of such a sheet, the following procedure may be followed:

A smooth-outer cover, preferably with a hard glazed surface, is first .wrapped around an impression cylinder' and printed upon. A double-coated makeready sheet then is wrapped around the impression cylinder over the aforementioned printed outer cover and the outside surface of the makeready sheet printed upon. During the second printing step, the mirror image of the printing form is printed by offset upon the side of the makeready sheet in contact with the originally printed glazed wrapping. Each side of the makeready sheet is then exposed to radiant energy to expand the same, and the expanded sheet placed in registration as desired.

A novel method for gaining registration of overlay makeready using relatively thin translucent sheets such as the one of Example 1 hereof, is as follows: A plain sheet of paper is wrapped around an impression cylinder, printed with an impression of a printing form, marked for subsequent registration, and removed from the cylinder. The translucent makeready sheet is. then printed with an impression of the printing form,'exposed to radiant energy, adhesively securedover the previously printed sheet of paper in registration with theprint thereon, and. the whole structure registered on-the impression cylinder, using the.

indicia markings on the plain sheet ofpaper.

For linotype printing, it is sometimes desired to increase the packing thickness over certain lines so as to obtain appropriate ink transfer to paper being printed. When using our makeready sheet material non-absorptive of radiant energy to accomplish this, one first marks or shades various selected areas of the sheet material with radiant energy absorptive ink or pencil according. to the desiderata for increased thickness over various lines or areas of a linotype printing'form. Suitably, markings or shadings of differentinfrared-absorptive qualities may be made by using various pencils, inks, crayons, etc., each with different infrared-absorptive qualities, or-by applying black ink or the likein various shades or density over various lines or areas -of our sheet material. The 'somarked sheet is then exposed and expands selectively accordingto the infrared absorptivity-of the marked areas.

'It is then'registered appropriately so as tocooperate with a linotype form in printing.

Makeready sheets hereof may also be used in making novel sandwich printing form constructions. One such construction is that gained by registering a selectively expanded makeready sheet, e. g., a positive-type or overlay-type makeready sheet as above set forth, beneath an electrotype, or the like, and adhesively bondingthe two together. The back side of the electrotype-may be shaved down so that the electrotype itself is extremely thin. A thin sheet of metal of-uniform thickness may be adhesively secured to the bottom side of the'structure, i. e., beneath the selectively thermoexpandedlayer of the registered makeready sheet, to contribute to the strength of the whole structure, if desired. Another sandwich type construction results if an electrotype, or the like, which suitably may be shaved thin, is pressed into a coating of a .heat-hardenable, resinous adhesive on auniformmetal backingby using a negative type makeready sheet, as above described, in register over the electrotype. The negative sheet, selectively expanded in highlight areas, will deform the thin electrotype' into thc adhesive layer when pressure is appliedthereover. The heat-hardenable resinous adhesive may substantially simultaneously be activated to hold the plate in deformed condition. v

A selectively thermoexpansible layer, as well as the backing, for our makeready sheets may be formedfrom a wide variety of materials. Because newpolymeric hydrophobic resinousmaterials and new puflingor blowing agents are continually being developed and marketed, it is impossible to catalogue all components useful in a heatsensitive layer. Further such a catalogue by specific chemical-names would be misleading in that .our invention relating to sheet materialsdoes not lie in any specific ;to use new materials which may become available, it will 15 .be a simple expedient, after studying the foregoing, to make routine tests and to utilize available knowledge in the light of this specification to determine whether the new materials are suitable. Good judgment will necessarily be exercised but it is safe to assume that no one will wishto make and process a useless sheet material or will be misled by the foregoing into making and processing worthless articles using new materials and ingredients which may become available.

We are aware ofprior art patents teaching sheet mate- 'rials which are light-sensitive or photosensitive and are useful in making photographic-type images. These patcats are unrelated to makeready for letterpress printing. In general, it may be noted that the sheet materials of these patents have thin hydrophilic, even water-soluble, layers which are not'designed to give high, graduated, tough and sturdy relief patterns upon exposure to radiant energy as taught herein.

What is claimed is as follows:

1. A fiexible, flat-lying, unitary sheet material of essentially uniform thickness adapted for makeready in letterpress printing by aprocess involving differential sas tained expansion, said sheet material comprising a flexible, planarly-stable, carrier web, and, on at least one side thereof, a flexible, selectively-thermoexpansible, ink-receptive, hydrophobic layer comprising a hydrophobic, at least temporarily thermosoftenable, resinous material and, uniformly distributed therethrough, a normally-dormant, heat-sensitive, pufiing'agent activatible at a temperature well above normal room temperature to expand said layer under conditions of heat, said puffing agent being present in an amount sufficient to provide on rapid and complete heat-activation of said layer an increase of at least 2 mils in the thickness thereof, and said layer being hardenable in expanded condition to an extent sufficient to support pressures at least on the order of 250 p. s. i. for about 15 seconds while maintaining areas of maximum expansion at least approximately 2 mils greater than the initial thickness thereof.

2. The article of claim 1 in which the selectively-thermoexpansible layer contains a thermosetting resin.

3. The article of claim 2 in which the selectivelythermoexpansible layer contains a curing agent for said thermosetting resin.

4. The article of claim 1 in which the selectively thermoexpansible layer is at least about 3 mils thick and contains an organic plasticizer.

5. The article of claim 1 in which the selectivelythermoexpansible layer contains a material absorptive of radiant energy.

6. A flexible, flat-lying unitary sheet material of essentially uniform thickness adapted for makeready in letterpress printing by a process involving differential sustained expansion, said sheet material comprising a flexible, planarly-stable, carrier web, and, on at least one side thereof, a flexible, selectively-thermoexpansible, ink-receptive, hydrophobic layer at least 2 mils thick and comprising a hydrophobic thermoplastic resin, a thermosetting resin and, uniformly distributed through said resins, a normallydormant, heat'sensitive, puffing agent activatible at a temperature well above normal room temperature to expand said layer under conditions of heat, said pulfing agent being present in an amount suflicient to provide on rapid and complete heat-activation of said layer an increase of at least'2 mils in the thickness thereof, and said layer being hardenable in expanded condition to an extent sufficient to support pressures at least on the order of 250 p. s. i. for 15 seconds while maintaining areas of maximum expansion at least approximately 2 mils above the initial thickness thereof.

7. The article of claim 6 in which the selectively- -thermoexpansible layer contains a curingagent for the thermoset-ting resin.

8. A flexible, fiat-lying, unitary sheet material of essentially mniform thickness adapted for makeready in 17 letterpress printing, said sheet material being characterized by an ability to expand in selected areas to present a relief according to a pattern inked thereon with ink highly absorptive of radiant energy, said sheet being sufficiently less absorptive of said radiant energy so that, upon exposure of said sheet after inking to brief, intense, and uniform radiant energy only those portions inked will expand commensurately with the amount of inking placed thereon to present a relief pattern thickest in solidly inked areas and thinnest in non-inked areas, and of graduated thickness in other areas approximately according to the density of ink thereon, said sheet comprising: a

flexible, planarly-stable, carrier web of low heat conductivity, and a flexible, selectively-thermoexpansible, inkreceptive, hydrophobic layer on at least one side of said carrier web, said layer being at least 2 mils thick and comprising a hydrophobic thermoplastic resin, a thermosetting resin and, uniformly distributed through said resins, a normally-dormant, heat-sensitive, puffing agent activatible at a temperature well above normal room temperature to expand said layer under conditions of heat, said putting agent being present in an amount sufficient to provide on rapid and complete heat-activation of said layer an increase of at least 2 mils in the thickness thereof, and said layer being hardenable in expanded condition to an extent suflicient to support pressures at least on the order of 250 p. s. i. for 15 seconds while maintaining areas of maximum expansion at least approximately 2 mils above the initial thickness thereof.

9. The article of claim 8 in which the selectivelythermoexpansible layer contains a curing agent for the thermosetting resin.

. 10. A fiexile, flat-lying, unitary sheet material of essentiaily uniform thickness adapted for makeready in letterpress printing by a process involving differential sustained expansion, said sheet material comprising a flexible, planarly-stable, carrier Web, and, on each side thereof, a flexible, selectively-thermoexpansible, ink-receptive, hydrophobic layer comprising a hydrophobic, at least temporarily thermosoft'enable, resinous material and, uniformly distributed therethrough, a normallydormant, heat-sensitive, puffing agent actiyatible at a temperature well-above normal room temperature to expand said layer under conditions of heat.

11. In a process of makeready for letterpress printing, the step of briefly exposing a makeready sheet comprising a flexible, selectively-thermoexpansible layer, and having a differentially radiation-absorptive makeready pattern thereon, to uniform and intense radiant energy differentially absorptive by elements of said pattern to provide a heat pattern sufficient to expand said layer selectively.

12. In a process of makeready for letterpress printing, the step of briefly exposing a makeready sheet nonabsorptive of radiant energy comprising a flexible, selectively-thermoexpansible layer, andhave a makeready pattern thereon of radiant energy absorptive elements, to uniform and intense radiant energy suflicient to expand the layer in selected areas in heat-conductive association with the radiant energy absorptive elements.

13. In a process of makeready for letterpress printing, the step of briefly exposing a makeready sheet absorptive of radiant energy comprising a flexible, selectively-thermoexpansible layer, and having a makeready pattern thereon of radiant energy reflective elements, to uniform and intense radiant energy sufiicient to expand said layer in selected areas absorptive of radiant energy.

14. A process of makeready for letterpress printing including the steps of inking a diiferentially radiation-absorptive pattern upon a makeready sheet comprising a flexible, ink-receptive, selectively-thermoexpansible layer, and briefly exposing said inked makeready sheet to uniform and intense radiant energy differentially absorptive by elements of said pattern to provide a heat patern sufficient to expand said layer selectively.

15. A process of makeready for letterpress printing comprising (1) inking a differentially radiation-absorptive pattern upon a makeready sheet comprising a uniform, flexible carrier web of low heat conductivity, and, firmly bonded thereto, an ink-receptive, heat-sensitive, coating of uniform thickness comprising a thermosoftening, resinous material containing, uniformly distributed therethrough, a heat-sensitive, pufiing agent, and (2) briefly exposing said inked sheet to uniform and intense radiant energy differentially absorptive by elements of said pattern to provide a heat pattern suflicient to selectively expand said sheet, said expanded sheet possessing sufficient strength and toughness in fully expanded areas to maintain at least a thickness variation of approximately 2 mils under a pressure at least as high as approximately 250 p. s. i.

16. A process of makeready for letterpress printing comprising (1) inking a pattern with a radiant energy absorptive ink upon a makeready sheet substantially nonabsorptive of radiant energy and comprising a thermosoftenable resinous material having a heat-sensitive puffing agent uniformly distributed therein, and (2) briefly exposing the inked pattern of said makeready sheet to uniform and intense radiant energy suflicient to heat and expand said sheet in selected areas in heat conductive association with said radiant energy absorptive ink.

17. A process of makeready for letterpress printing comprising (1) inking a pattern with radiant energy reflective ink upon a makeready sheet absorptive of radiant energy and comprising a thermosoftenable resinous material having a heat-sensitive pufling agent uniformly distributed therein, and (2) briefly exposing the inked makeready sheet to uniform and intense radiant energy sufficient to heat and expand said sheet in selected areas absorptive of radiant energy.

18. A process of makeready for letterpress printing comprising (1) inking a makeready pattern upon a flexible, selectively-thermoexpansible layer of a makeready sheet to provide differential radiation absorptivity, said layer containing a resinous material and a pufiing agent, (2) raising said inked makeready sheet to an ambient temperature above room temperature but below the activation temperature for said puifiing agent, and then, (3) briefly exposing said inked layer to uniform and intense radiant energy differentially absorptive by elements of said pattern to provide a heat pattern sufiicientto expand said layer selectively.

19. A process of makeready for letterpress printing comprising 1) placing a makeready pattern on a flexible, selectively-thermoexpansible layer containing a resinous material and a pufiing agent to provide differential radiation absorptivity, (2) briefly exposing said layer to uniform and intense radiant energy to provide, according to said makeready pattern, a heat pattern sufficient to expand said layer selectively, and '(3) registering said 'selectively expanded layer with a printing form.

20. A process of makeready for letterpress printing comprising (1) inking a printing form makeready pattern reflective of radiant energy upon a flexible, ink-receptive, selectively-thermoexpansible layer absorptive of radiant energy, said layer containing a resinous material, a material absorptive of radiant energy and a pufling agent, (2) briefly exposing said inked layer to uniform and intense radiant energy suflicient to heat and expand said layer in selected areas which absorb radiant energy, said layer being formed so as to be sufliciently hard and tough in selectively expanded areas to maintain .maximumly expanded areas at least 2 mils greater than the initial thickness thereof while under a pressure on the order of 1000 p. s. i. for about 15 seconds, (3) registering said selectively expanded layer over the printing surface of said printing form, and (4) applying pressure. over areas of the back of said printing form so as t'o t9 i accord ng to. the relief; of said-registe ed sel tixe y exp nded ma ere dy shee A Process of. k dy r e e press printing eoma s ns (L). k ng a Pa r a pr n ing form with radiant nergy. abs rptive. ink up n. a p ti makere dy sheet substan ly onbsor tive of radiant energy an comprising an ink-receptive, selectively-.thermoexpansible layer. qant inin the m so tening ha denable resinous materi ls a sh ng agent, (2.) nk g pattern of hep im ns form wit r ian energy r tive ink up n a esa ivefm kere yshe t' f a o st u on. su h. as descr be in. s p (1.1 b co t n ng a r di n energy absorpti m t r al n. uni orm; e teond e ive ass iationtherewith, (3) brieflyv exposing each sheet to uniformand intense radiant energy suflicient to. selectively expand the layers thereof in areas affected by heat, generated, from absorbed radiant energy, said selectivelyexpanded layers being formed, so as to be sufligiently har and. t gh. o'maiatain maa mum y xp nded ar as at least 2 mi s g t h n. the initial hickn ss hereof hile under a pressure on, he or er of .0.0 1?..$.. i. fo about 1 5seoonds, (4.) registering said selectively-expanded positive sheet below said printing form and; said selectively-expanded negative. sheet above said printing form, and, (5,), applying pressure over, all areas of said, laminate so as to; distort said printing form by raising solid tone areas and. depressing highlight areas.

22. A flexible, flat-lying, unitary sheet material of essentially. uniform thickness; adapted for makercady in letterpress printingby a processinvolving diiferential sustained expansion, said sheet material comprising, aflexible, planarly-stable, carrier web, and, on at least one. side he eo a flexib e e et e y-the m xn ns bl inkeFeP Y hydropho c yer a e st 2 mi e thick and comprising a hydrophobic, at, least temporarily thermosoftenable, tough, resinous material and, uniformly dis tributedtherethrough, a multitude of finepartijcles of a normally-dormant, heat-sensitive, pufiing agent activatible'at a temperature well above normal room temperature to produce a gas as .a result of'chemical decomposition and; thereby expand said layer under conditions of'heat, said puffing agent being present in an amount sufiicient to provide on rapid and: complete heat activation of said layer-an increase of atleast 2 mils in the thickness thereof,

and said layer being hardenable in expanded condition. to an extent to support pressures at least on the order of-250p. s; i. for about 1-5 seconds while maintaining areas of maximum expansion at least approximately 2 milsgreater than the initial thickness thereof. I

23. A flexible, fiat-lying, unitary sheet material: of essentially uniform thickness adapted; for makeready in letterpress printing by -a processinvolving differential sustainedexpansion, saidsheet material comprisinga flexible,

plamrly-stable, carrier web, and, on at least one side thereof, a flexible, selectively-thermoexpansible, .inloreceptive, hydrophobic, at least: temporarily-thermosoftenable layer at-least 2' mils. thickand comprising a hydrophobic thermoplastic resin, a thermosetting resin, aheata t a b e atin ag nt f r; said thermosettingn; un o mly d r uted hr u h said; ay r, a multitude of fine particles of a normally-dormant, heat-sensitive, puffing agent activatibleatatemperature well above. normal room mperature t p odu a ses as a result: of chemical decomposition. and. thereby e p a d layer under eondi ions of. bean. said putfing agent being, present in an amount suliieient. to provide. on rapid and complete heat activation .of said layer an increase of at l'east 2 mils in the thickness, thereof, and said layer being hardenablc in expanded conditionI to an extent to support pressures at, east on the order of 250 p. s. i. for about 15 seconds while, mainta ning areas of maximum expansion at least approximately 2 mils greater than the initial thickness thereof.

24. The sheet material of claim 23 wherein the heatsensitive pufling agent is activated to produce a gas within approximately 150 F, of the thermosoftening tempera ture of the selectively-thermoexpansible layer.

it a 25. The sheet material of claim 24 wherein the carrier web is of low heat conductivity.

26;. The sheet material of claim 23 wherein the selectively-.thermoexpansible layer contains. a material which absorbs radiant energy, said sheet material being further eharaetgerized in that its layer is hardenable in expanded condition toan extentto support pressures at least on the order of H p. s. i. for about 15 seconds while maintaining areas of maximum expansion at least approximately 2 mile, greater than the initial thickness thereof.

27. A flexible, flat-lying, unitary sheet material of essentially uniform thickness adapted for makeready in letterpress printing by a process involving dificrential sustainedexpansion, said sheet material comprising a flexible, planarly-stable, carrier web at least about 2 mils. thick and of low heat conductivity, and, on at least one side thereof, a flexible, selectively-thermoexpansible, inkreceptive, hydrophobic, at least temporarily thermosoftenable layer haying a uniform surface. characteristic, said layer beingat least 2 mils thick and comprising a hydrophobic thermoplastic resin, a thermosetting resin, 0. heatactiyatible curing agent for said thermo-setting resin, and, uniformly distributed through said layer, a multitude of fine particles of a normally-dormant, heat-sensitive, puffing agent activatible at a temperature well above normal room temperature, and within approximately F. of the thermosoftening temperature, of said layer, to pro duce a gas as a result of chemical decomposition and thereby cause, expansion of said layer under conditions of heat, said puffing agent being present in an amount sufficient to provide on rapidand complete heat activation of said layer an, increase of at least 2 mils in the thickness thereof, and said. layer being hardenable in ex panded conditionto anextent to support pressures at least on t he order of 250 p. s. i. for about 15 seconds while maintaining areas ofmaximum expansion at least approxi mately 2 mil's g reater than the initial thickness thereof.

28. The sheet material of claim 27 wherein the puffing agent is present in an amount between about 1 and 10 percent by weight of; the selectively-thermoexpansible. layer.

29; The, sheet material of claim 28 wherein the selectively-thermoexpansible layer contains a material which absorbs radiant energy, said sheet, material being further characterizedin; that itslayer is hardenable in expanded condition to an extent to support pressures at least on the order; of 1000 p. s. i. for about 15 secondswhile maintaining areas of maximum expansion at least approximately 2' mils greater than the initial thickness thereof.

No references cited.

U. S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,825,282 James BF er en et al. March 4, 1958 It is hereby certified that error appears .in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 13, line 73, for "100 p. s. i." read 1000 p. s. i. column 14, line 36, for "imbition' read imbibition column 17; line 33, for hileicile" read flexible line 56, for "have" read having ---e; line '74, for "pattern" read pattern Signed and sealed this 27th day of 1958.

(SEAL) Attest: KARL HO AXLINE ROBERT'C. WATSON Attesting Officer Comnissioner of Patents

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