US2789500A

US2789500A - Process of making a printing member

Info

Publication number: US2789500A
Application number: US373945A
Authority: US
Inventors: Reilly Frank Eugene
Original assignee: Electrographic Corp
Current assignee: Electrographic Corp
Priority date: 1953-08-13
Filing date: 1953-08-13
Publication date: 1957-04-23
Anticipated expiration: 1974-04-23

Description

April 23, 1957 F. E. REILLY PROCESS OF MAKING A PRINTING MEMBER Filed Aug. 13. 1953 FRANK E. RE/LLY A ff@ A TTORNEYS United States Patent O PROCESS F MAKING A PRINTING MEMBER Frank Eugene Reilly, Chicago, Ill., assignor to Electrographic Corporation, New York, N. Y., a corporation of Delaware Application August 13, 1953, Serial No. 373,945

Claims. (Cl. 101-401.1)

The present invention relates to a novel and improved process of making printing members, especially arcuate printing members for high speed rotary printing.

The present invention has for its object the provision of a novel and improved process for the rapid and economical manufacture of letterpress printing members of high quality comprising a thin plastic printing plate and a thicker metal backing member or support, the whole having good strength and being especially useful for use in the making of rotary printing members. A further object is the provision of a process by which a printing plate formed of relatively light weight thermoset resin may be mounted on a curved metal base economically to provide a printing plate of high quality, good wearing quality and in which the mounting or backing of the plate may be carried out with conventional stereotyping equipment. Still another object is the provision of a novel and improved process by which a printing plate of thermoset plastic may be backed by casting a curved mass of molten metal against the back of the printing plate, while the printing plate is in a curved condition, thereby avoiding the necessity of laminating the printing plate to a preformed metal base member, which has been an exacting and time consuming operation.

In general, and in accordance with the process of the present invention, there is provided a relatively thin, somewhat flexible printing plate which is formed of a thermoset plastic or resin and has good resistance to relatively high temperatures for a least short periods of time. This plate is preferably provided with a relatively smooth back and is of uniform thickness in its printing areas. Such a plate is initial-ly curved to the approximate curvature desired, usually under heat and pressure, and is then provided on its rear face with an adhesive layer of a heat sensitive adhesive. The adhesive may be applied as a liquid and dried or may be formed as a 'dry adhesive sheet which is secured to the rear face of the plate and extends thereover.

The curved, adhesively backed plate is then positioned in a curved casting box of the desired curvature, which may conveniently be a vacuum stereotype casting box. The face of the plate is preferably held firmly to the desired curvature by suction applied to the face of the plate, and while so held, molten metal, such as stereotype metal, is run into the box to ll the box at the back of the plate, to melt the adhesive and to bond with the back ofthe plate as the metal congeals.

. The plate is then removed from the box, is bevelled on its edges and cylindrically shaved on its interior, or otherwise finished to give it its proper and desired dimensions, thereby preparing it to go on the press.

Of the drawings:

Figure 1 is a fragmentary sectional view of a printing plate for use in the present invention, with an adhesive attached to its back and with a protective layer.

Figure 2 isa fragmentary'sectional view of the plate after it has been bent to the desired curvature.

Figure 3 is a sectional view of a vacuum stereotype ICC and pressure into a mold of the printing plate to be reproduced.

Preferably, there is provided a sheet of fabric 16, such as a coarse weave muslin cloth previously saturated with a thermosetting resin varnish, such as a phenol formalde hyde resin varnish. The varnish impregnated cloth is sprayed on one side with a dispersion of an unfilled phenol formaldehyde thermosetting resin in alcohol and toluol until a coating has been built up which is from .015 to .030 thick after which the liquid is largely evaporated. Then the other side of the fabric is similarly sprayed with a similar dispersion, to form a layer 14, producing a plate which is relatively thin and is usually between 0.030 and 0.075" thick.

After the liquid of the

dispersion layers

12 and 14 and the varnish have been substantially evaporated and the coated fabric is substantially or fully dried, the thermoset resin is subjected to heat and pressure with the face of one of the

layers

12 or 14 in contact with a mold of the printing plate to be reproduced. The amount of heat and pressure will 'depend upon the nature of the resin employed, but with a phenol-formaldehyde thermosetting resin, the pressure is usually from about 200 to 400 p. s. i.-

set, the back of the plate is sanded or ground to roughen` its surface and to remove any unevenness which may have resulted from the molding operation. The roughening of the back 0f the plate increases the strength of the adhesive bond which is to be established between the plate and its backing member.

In case a ilat plate is to be made into a flat printing member, the back of the plate is provided with an adhesive layer 20 which is adapted to bond with the metal to be cast. Such a layer may be sprayed or brushed on the back of layer 12, or may be applied as a solid sheet about 0.003 thick. Among the adhesives which may be used are adhesives such as a solution of polychloroprene (neoprene) in toluol, a dispersion of a polymide, such as a low molecular Weight nylon, in methyl alcohol containing about 7% phenol, or less preferably phenol formaldehyde varnish, a solution of an epoxy resin, or other adhesives which will bond by heat with the thermoset resin of the plate 10 and with the metal of the backing and which are not destroyed by being heated to the temperature of the backing metal as cast.

The layer of adhesive 20 is preferably covered with a sheet of thin tin or lead foil 21, which is pressed to the adhesive layer prior to its being fully dried and adheres thereto. The plate 10, adhesive layer and thin sheet of tin or lead, usually about 0.001" or 0.002" thick, are then heated for a period of a few minutes at a temperature of from 250 to 350 F. to thoroughly dry the adhesive and to remove any volatile ingredients from either th adhesive or the body of the plate 10. f

This heating is preferably carried out by heating the curved saddle or supporting member, and a conventional ,l mat scorcher may conveniently be usedI for this purpose.

When the heating has been completed, the plate assumes 3 a geriet-ally cylindrical shape approximating the desired curvations of the finished plate.

The metal foil sheet 21 also serves during the heating operation to keep the plate from becoming bonded t the support on which the plate is heated.

The curved plate with its adhesive and foil Vlayers 2 0 and 21 is then inserted in a vacuum stereotype casting box with the face 18 of the plate against the curved concave face of -cope 22 and is retained therein by the ller'pieces 32 at the ends of the box. The box has the desired `curvature of the printing member to be produced andthe space lbetween the cope and the drag 28 is equal o'rvslightly greater than the desired thickness vof the printingme'mbcr comprising the printing plate and cast backing metal.

t The `face `ot the printing plate is then subjected to suction through the suction .ports 24 Aformed in the concave face of the cope communicating with the suction connection 26, and the plate is thereby drawn accurately tothe curvature of the 'cope and firmly held during the metal casting operation.

Molten metal, such as stereotype metal, electrotype backing metal, lower melting alloys, or other suitable meta-1 alloys. Lead alloys melting from 400 to 500 F. are preferred, but alloys of much lower melting points may be used. Where stereotype metal is used, it is preferably cast at a temperature ranging from 550 to 600 and suicient metal is poured to lill the space 30 between the back of the plate 10 and the convex surface of the :drag 28, suction being .maintained through the connection 26 and ports 24 until the metal 34 has congeal'ed. The drag 28 is preferably water cooled, as usual, not vonly to speed up the whole operation, but also to `reduce the time during which the plastic plate 10 and adhesive 20 are heated to a relatively high temperature.

The :molten metal initially melts the foil backing 21 and also causes the adhesive to become tacky so that a firm bond is established as the metal congeals.

The casting box is then opened, the iller pieces moved out of the way and the printing member may then be removed from the casting box.

Figure 4 illustrates a fragmentary portion of a curved printing plate in accordance with the present invention as it appearsafter the finishing operation with its cylindrically curved interior or concave surface shaved to form a smooth surface, and with its edges bevelled to tit the plate clamps with which the plate is to be secured to lthe 'cylinder of the printing press. In this finished form, the adhesive layer has been melted and bonds the plastic plate 10 to the metal backing 34, and the foil sheet 21 has been alloyed with the surface of the metal back 34 to be integral therewith.

Suchplates can be prepared in much less time than is required for laminating 'a plastic plate to a metal or other base member, the face of the printing plate is never subjected to heavy or damaging pressure, extremely thin plastic plates may be used and the cost of the plastic material usedv is thereby greatly reduced while the metal of the backing can be remelted and reused. Additional savings are possible, as the printing plate 10 with its adhesive and

foil layers

20 and 21 are very light and may be shipped economically, and are ready to be backed up at the place of use by conventional stereotyping operations. The face of the printing member is also truly cylindrical regardless of any uuevenness in the thickness of the printing plate 10 as the face is held to a true cylind`r`ica`l 'shape while the metal backing 34 is cast therea'gainst.

VAmong the thermosetting, synthetic resin materials which may be used for the printing plate 10 are the phenol-formaldehyde resins, the urea-formaldehyde, resocinol-'formaldehydq melamineform'aldehyde, glycenylephthalate, diallyl phthalate, and `furan resins, all of which "are used in a .partially uncured-state. Thesere'sins are preferably unfilled, but moderate amounts of heatresistant llers, such as nely ,ground asbestos or mica may be used if desired.

Where such resins are used as a dispersion, rather than as a solid sheet, they may be suspended in a volatile solvent such as toluene, or in a petroleum fraction such as naphtha, and are then brushed or sprayed on the surface of the fabric reinforcing layer 16.

The adhesive layer :may be formed of any of the thermally-sensitive adhesives such as a solution or dispersion of polychlo'rop'rene, a phenol-modified polymide,

an acrylonitrile-butadiene rubber, an acrylonitrile-butadiene rubber-phenol formaldehyde resin mixture, a phenolic elastomer, a phenolacetal resin, or an Aepoxy resin dissolved or suspended in an appropriate solvent, such as benzene, toluene, xylene, methyl-ethyl ketone, methyl amyl ketone, a volatile alcohol or a chlorinated hydrocarbon. Preferably, however, the adhesive is applied as a thin sheet (about 0.003 thick) of the adhesive, applied to the back of the 'printing plate 10 after which it is covered with the metal foil 21, vheated land pressed until the solvent has evaporated.

Where lower melting point metals are used for the backing 34, the adhesive need not be chosen so carefully, and other lheat sensitive adhesives may be used.

What l 'claim is:

l. The process 'of making a printing member which comprises fo'r-'ming a thin printing plate from a thermosetting plastic material-having good resistance to relatively high temperature for atleast short periods of time, providing'a heatsensitive adhesive on the back side thereof, said adhesive ybeing 'able to withstand the temperature of molten backing metal, contacting the adhesive with a mass of molten metal and-allowing the molten metal to congeal in lcontact with the adhesive and the back o f the plate whereby-the cast metal 'backing is adhesively secured to the back of the plate and rapid cooling of the cast metal whereby degradation of the plastic is prevented.

2. A process as claimed in claim l in which the printing plate is initially curved, and is held in lits ual curved position by suction while the backing metal is cast.

3. A process as claimed in claim 2 in which the adhesive is applied to the back of the printing plate as a thin sheet of adhesive material which is free of components volatile at the temperature of casting.

4. A process as claimed in claim 1 in which the adh'e'sive is 'applied to the back of the printing plate as a thin sheet of adhesive material which is free of components volatile at the temperature of casting.

'5. The process of making a cyiindrically curved printing member which comprises providing va thin, reinforced llexible printing plate formed of a thermoset plastic having good resistance to relatively high temperature for at least short periods of time, securing a sheet of heat sensitive adhesive to the back side of said plate, said `adhesive being able to Withstand'thetemperature of molten backing metal, holding the plate by suction against a cylindrically curved surface,contactin`g the adhesive With a mass of molten metal'and allowing the molten metal to congeal in Contact with the adhesive and the back of the plate whereby the cast'metal backing is adhesively secured tothe lback of the plate; and rapidly cooling the metal of the cast back to -prevent degradation of the thermoset plastic plate, the adhesive being substantially Yfree `of ingredients which are volatile at the ftemperatures of casting.

References Cited `in the tileV of this patent UNITED STATES PATENTS 1,139,259 Cottrell May 11,1915 1,377,509 Novot'ny May 10, 19'2'1 1,377,517 ANlvtny M'ay V10,1921 2,162,825 'Richards June'20, '193'9 2,558,269 Reilly June 26, v-1951 it. l