US2764085A - Masters for planographic printing - Google Patents

Description

p 1956 c. J. SHOEMAKER ET AL 2,764,085

MASTERS FOR PLANOGRAPHIC PRINTING Filed Jan. 10, 1952 I &

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IN V EN TORS ATTORNEYS.

United States Patent 2,764,085 MASTERS FOR PLANOGRAPHIC PRINTING Application January 10, 1952, Serial No. 265,896 8 Claims. (Cl. 101-149.2)

This invention relates to lithographic printing plates and to new and improved methods for producing an imaged plate thereof;

Lithographic printing depends for its operation upon unique properties occurring in lithographic surfaces which properties were first found to exist in certain stones and later developed in etched zinc and aluminum plates. More recently, lithographic surfaces have been provided on paper plates having sutficient flexibility for winding about a typewriter platen or the like to adapt the plate for use in otfice copy work. Such paper plates are fab ricated of parchmentized paper or by the build-up of suitable hydrophilic colloid coatings on the paper surfaces, as represented by the patents of Shepherd, No. 2,154,219; Simons, No. 2,156,100; Frost, No. 2,534,588; Worthen, No. 2,534,650; Van Dusen No. 2,542,784, and the like.

so as to be preferentially and rapidly wet out by water or other repellent solution. When the plate is imaged, a letter outline of ink receptive material is formed on the surface of the plate, as by direct inscription with a greasy or oily based composition or with chemical compounds capable of reacting with the material forming the lithothe original and then the chemically developed negative is the imaged portion would then be substantially wiped out. It is an object of this invention to provide a still different type of lithographic plate and it is a related object to provide a still different method for producing the imaged plate therefrom.

Another object of this invention is to produce a paper lithographic plate having a lithographic surface which is hydrophilic in character but becomes preferentially wet out by ink in areas subject to thermal reaction, and it is a related object to provide a method for producing same. These and other objects of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments are shown in the accompanying drawing in which Figure l is a sectional elevational view of an assembly 2,764,085 Patented Sept. 25, 1956 for producing an imaged lithographic plate in accordance with the practice of this invention;

Figure 2 is an imaged sectional elevational view of the arrangement of parts for producing the lithographic imaged plate in accordance with the process of Figure 1;

Figure 3 is a sectional elevational view corresponding to that of Figure 2 but illustrating the in a subsequent stage of the process;

Figure 4 is an enlarged sectional elevational view of the imaged plate produced in accordance with Figures 1-3; and

Figure 5 is a sectional elevational view of a different form 0 apparatus for plate film, paper, fabric or fiber board. If the base sheet is capable of water absorption, it is preferred to treat the base sheet with materials to introduce water repellency, especially if it is desirable to produce a large number of copies therefrom.

Water repellency may be introduced by the incorporation of suitable resinous materials, such as urea formaldehyde, melamine formaldehyde, phenol formaldehyde, or other coating compositions containing synthetic resins or rubbers, such as rubber hydrochloride, chlorinated rubber, butadiene-acrylonitrile copolymer, butadienestyrene copolymer, neoprene and the like, and combinations thereof with resins. Instead of incorporating resinous or rubbery substances as by coating, impregnating or the like, the desired water repellency may also be supplied by treatment of the base sheet with materials such as oils, varnishes, water repellent substances such as soaps, fatty acid amides, fatty acid cationic amines, and the like.

The base sheet in the form of be provided wit modified by the inclusion of finely divided inert fillers such as diatomaceous earth, silica, clay, barium sulphate, satin white, chalk and the like. The formulation and production of coated base sheets with the practice of this invention.

The base sheet may be treated as by coating or impregnation with a solution containing between 3-30 percent by weight of the Werner complex compound in which the acido group coordinated with the trivalent nuclear chromium atom contains from 1-8 carbon atoms and is preferably unsaturated between one or more carbon linkages, such for example as methacrylatochromic chloride or a complex chromic salt in which the acido group is derived from vinyl acetic acid, furfuracrylic acid and the like. Acido groups of saturated acids of low carbon length might also be used, such for example as the acido groups derived from acetic acid, propionic acid, butyric acid and the like.

Werner complex compounds of the type used in the practice of this invention are soluble in water in fairly wide proportions and may be applied to the base sheet within the concentrations prescribed by any conventional means, such as spray coating, brush coating, wash coating, flow coating, by a dip squeeze process or the like. Upon drying at room temperature or preferably at elevated temperatures below 250 F, the Werner complex compound becomes insolubilized but remains water receptive to provide a desirable lithographic surface on the base sheet. While it is unnecessary to provide intermediate coats to achieve anchorage of the Werner complex compound, it is nevertheless possible to make use of intermediate anchor coats for the purpose of achieving greater adhesion and to increase the integrity and life of the lithograph plate.

It has been found that the base sheet having the Werner complex compound insolubilized thereon forms an excellent lithograph surface upon which an ink receptive image may be formed as by thermal reaction to convert the water receptive hydrophilic surface to a surface which repels water and is preferentially receptive to ink. A lithographic plate of the type described is particularly well adapted for use in a new and improved technique for the preparation of a lithographic printing plate directly from an original by positioning the plate with the lithographic surface in contact with the original and then directing radiations rich in infrared upon the original whereby the radiations are absorbed by the black letter outlines and converted into heat. The heat pattern'which develops almost immediately transfers by direct contact to the water receptive hydrophilic lithographic surface which is converted by the heat reaction to an ink reciptive water repellent image portion corresponding to the letter outlines of the original.

Light sources containing sufficient infra-red include light rays having a wave length ranging from 8,000 to 40,000 angstroms. Radiant energy capable of the phenomenon described may be found to exist in ordinary daylight and may be developed in sufficiently high intensities by light generating sources such as a flash bulb, a tungsten filament lamp, a carbon arc lamp, infrared ray lamp or the like. It has been found that the amount of heat developed depends chiefly upon the duration of exposure and the intensity of the usable radiant energy in the light beams directed onto the original. The amount of heat developed in the original also depends upon the depth of color and the character of the material of which the letter outlines are formed in the original.

The temperature which is required for the conversion of the hydrophilic water receptive Werner complex compound insolubilized to form the lithograph surface on the base sheet depends in part upon the complex compound and less upon the concentration thereof on the base sheet. It appears that temperatures in excess of 350 F. are capable of being developed when sufficient intensities of infra-red radiations are directed onto the original to effect the desired conversion of the hydrophilic insolubilized complex to a hydrophobic substance which is highly receptive to ink and water repellent. Although the majority of the radiations are reflected or otherwise dissipated by the light background of the original, some radiations are absorbed but in amounts insufficient to affect the heat pattern and cause undesirable reaction in the lithographic surface.

It has been found that best definition of the imaged faces of which enjoy plate and of the copy produced therefrom is achieved when the lithographic surface is arranged in direct contact with the original and that definition is greatly improved when sufficient heat is developed by the absorbed radiations in minimum time. if prolonged exposure is employed for the purpose of developing adequate heat to accomplish the desired thermal reaction, there is a tendency for the heat to become dissipated laterally and produce ragged letter outlines in the imaged plate and copy produced therefrom. in order to accomplish the desired instantaneous and concentrated exposure, devices such as a photographers flash lamp may be used. Instead, use may be made of devices in which the source of infra-red ray bearing light is energized by high intensity by a capacitor device similar to that generally used in industrial spot welding. Other devices for achieving the desired and short exposure consist of the use of a relatively long but thin source of infra-red radiation such as a hot wire or tungsten filament lamp and the use of suitable lenses therewith to focus the radiations onto the original. Such devices may be adapted to traverse the original at constant speed so that exposure of each lighting element is of substantially equal intensity throughout.

The following examples for manufacture of a lithographic plate in accordance with the practice of this invention and the imaging thereof directly from an original will now be described by way of illustration, but not by way of limitation.

Example 1 A sheet or web of 60 pound wet strength kraft paper is coated on one or both sides, as by means of a roller coater, spray coater, or by a brush coater with a 10 percent water solution of methacrylato chromic chloride. When air dried to insolubilize the methacrylato chromic chloride, the sheet or web is cut into plates the surlithographic properties.

Example 2 A highly calendered sheet of paper is coated on one side with a 5 percent solution of acrylato chromic chloride and dried at a temperature of about F. The sheet is coated a second time with the same composition followed by a similar drying step to insolubilize the complex and form a water receptive hydrophilic lithograph surface.

Example3 A thin film of aluminum laminated onto a paper base is coated as by a spray coater or brush coater with a 7 percent solution of furfuryl acrylic chromic chloride and allowed to dry at a temperature slightly above atmospheric conditions to insolubilize the complex on the metal surface. The complex appears strongly to anchor to the metal surface by reason of the coordination between the trivalent nuclear chromium atom and the groupings which predominate on the aluminum surface. Instead of aluminum, other metallic films or plate may be used, such as zinc, tin, copper or the like, or the aluminum plate may be replaced by film's or sheets of plastic such as polyvinyl chloride, polyvinylidine chloride,

polymethyl methacrylate, polyvinyl butyral, polyvinyl alcohol, and the like.

Example 4 A plate embodying features of this invention may be prepared by application of a 20 percent solution of methacrylato chromic chlorid onto a hydrophilic colloid surface by the method described and claimed in one of the previously described issued patents of Mullen, Frost or Van Dusen, with or without the steps of insolubilizing the hydrophilic colloid as by the addition of salts in the case of casein or by the addition of acids in the case of cellulose ethers or esters and with or without the steps of desensitizing the plate by application of silicate or other wash coat.

In the manufacture of an imaged plate, the lithographic plate prepared aspreviously described is positioned with the coated side 11 in surface contact with an original 12 of which copies are desired. Radiations 13 rich in infra-red are directed onto the original by means of an incandescent lamp 14 adapted slowly to traverse the original and provided With a reflector 15 to direct the rays downwardly onto the original. The radiations directed onto the original are absorbed by the black letter outlines 16 in the original and converted into heat while imaged portion 18 which repels water and is preferentially receptive to ink.

It is preferred to arrange the original with the printed side uppermost, as illustrated in Figure 5, but when the plate directly from an original in the manner described, the original 12 and plate 10 are adapted to be positioned between a substantially rigid support 19 and a glass plate 20 through which the radiations may be directed.

By way of further modification, an imaging device embodying the concepts described and claimed herein may comprise a housing 21 having a number of infrared ray bearings lamps 22 therein with reflectors 23 arranged to direct the radiations upwardly through a glass cover plate or a hot point.

It will be apparent by way of further modification that the Werner complex compound of the type described and claimed herein may be used to form a lithograph surface having the described characteristics wherein instead of the manufacture of lithograph plates, as set forth in the In such instances relinates, manner described in the prior art patents.

It will be understood that numerous changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. An imaged lithograph plate comprising a base atom is unsaturated and contains from 1-8 carbon atoms and which in the imaged portion has been thermally reacted at a temperature in excess of 350 F. to form :a hydrophilic ink receptive portion in the surface while the unreacted portion of the surface remains hydrophilic in character and water receptive.

2. A lithograph plate comprising a base sheet having a continuous surface, a hydrophilic colloid layer on said base sheet and a coating on said layer containing an insolubilized Werner complex compound. in which the acido group coordinated with the trivalent nuclear chromium atom contains less than 8 carbon atoms and which in the imaged portion has been thermally reacted at a temperature in excess of 350 F. to form a hydrophobic, ink receptive portion in the surface while the remainder of the surface is hydrophilic in character and water receptive.

3. In a method of producing an imaged lithograph plate directly from an original formed of infrared ray absorbing-heat generating material with. a lithograph master having a continuous hydrophilic, water receptive surface containing an insolubilized Werner complex compound in which the acido group coordinated with the trivalent nuclear chromium atom contains l-8 carbon atoms and which upon thermal treatment at temperatures in excess of 350 F. converts the heated portions of the surface to a hydrophobic, ink receptive imaged portion, comprising the steps of positioning the lithograph master with the coated side in surface contact with the original, directing a sufficient quantity of radiations rich in infrared onto the original to generate a heat pattern corresponding to the original for transfer to the master for thermal reaction to convert the heated portion of the hydrophilic surface containing the insolubilized Werner complex compound into a hydrophobic, ink receptive imaged portion.

4. In a method of producing an imaged lithograph plate directly from an original formed of infrared ray absorbing-heat generating material with a lithograph master having a hydrophilic, Water receptive surface with a coating of an insolubilized Werner complex compound which becomes hydrophobic to form an ink receptive image in the surface upon thermal reaction, comprising the steps of positioning the lithograph master with the coated side in surface contact with the original, directing a suflicient quantity of radiations rich in infrared onto the original to generate a heat pattern corresponding to the original having a temperature in excess of 350 F. for transfer to the master for thermal reaction to convert the heated portion of the hydrophilic surface containing the insolubilized Werner complex compound into a hydrophobic, ink receptive imaged portion.

5. A lithographic plate comprising a base sheet in the form of a metal plate the surface of which has been treated to provide a hydrophilic, water receptive, ink repellent surface, and a Werner complex compound in which the acido group coordinated with the trivalent nuclear chromium atom contains less than 8 carbon atoms and an unsaturated carbon to carbon linkage and which is insolubilized as a coating on the treated surface of the metal plate to provide a surface which may be converted into a hydrophobic and ink receptive imaging material upon thermal treatment in the imaged areas at a ternperature in excess of 350 F.

6. A lithographic plate consisting of a base sheet the surface of which has been treated ink receptive imaging material upon thermal treatment in the imaged areas at a temperature in excess of 350 F.

7 7. A lithographic plate as claimed in claim 6 in which the hydrophilic, Water receptive, ink repellent surface on the base sheet comprises a hydrophilic colloid coating.

8. A lithographic plate as claimed in claim 6 in which 2231045 Wood 1941 the Werner complex compound is present as an ingredient 5 22471040 Her 1942 in the hydrophilic colloid coating. F 6161 Her 1944 2,381,752 Iler Aug. 7, 1945 2,524,803 Iler Oct. 10, 1950 2,544,666 Goebel et a1 Mar. 31, 1951 10 2,549,220 McLaren Apr. 17, 1951 2,611,718 Steinman Sept. 23, 1952 2,662,835 Reid Dec. 15, 1953 8 References Cited in the file of this patent UNITED STATES PATENTS w Be f

Claims (1)

1. AN IMAGED LITHOGRAPH PLATE COMPRISING A BASE SHEET HAVING A CONTINUOUS SURFACE, A COATING ON SAID BASE SHEET HAVING AN ISOLUBILIZED WERNER COMPLEX COMPOUND DISTRIBUTED THROUGHOUT THE COATING AND IN WHICH THE ACIDO GROUP COORDINATED WITH THE TRIVALENT NUCLEAR CHROMIUM ATOM IS UNSATURATED AND CONTAINS FROM 1-8 CARBON ATOMS AND WHICH IN THE IMAGED PORTION HAS BEEN THERMALLY A HYDROPHILIC INK RECEPTIVE PORTION IN THE SURFACE WHILE THE UNREACTED PORTION OF THE SURFACE REMAINS HYDROPHILIC IN CHARACTER AND WATER RECEPTIVE.

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