US2311047A - Lithographic plate and process of making the same - Google Patents

Description

Ffilb. 16, 1943. w T HAGELlN 2,311,047

LITHOGRAPHIC PLATE AND PROCESS OF MAKING THE SAME Filed Dec. 6, 1940 zz g f LITHOGRAC PLATE PROCESS OF G E SAME W T. Hagelin, Chicago, Ill.

Application December 6, 1940, Serial No. 368,753

15 Claims. (Cl. 41-415) This invention relates to a lithographic plate method of producing the same upon which a and a process of making the same. More parvery ink-receptive image may be impressed ticularly, this invention relates to a process of either by means of direct contact or by means producing a lithographic plate having a surface of photolithographic processes. that is very receptive to greasy films such as may A further object of this invention is the probe applied thereto by crayon, lead pencil, grease vision of a metal surface coating which is subink, and the like or by a suitable stylus through a stantially non-oxidizable even though exposed to tracing sheet such as carbon paper or a typethe atmosphere under conditions normally prowriter ribbon. moting oxidation.

A plate, to be useful in ordinary lithographic A still further object of this invention is the work, should be one that is treated in such a provision of a new etch solution which may be manner that the surface thereof is adapted readused for the treatment of lithographic plates. ily to receive a grease coating or film such as may Further additional objects will appear from be made through a typewriter ribbon or by penthe following description, the accompanying cil, crayon, or other drawing or tracing instrul5 drawing, and the appended claims. ment that is capable of depositing a greasy film In accordance with one embodiment of this on said surface when contacted therewith. The invention, a lithographic plate may be prepared character of the surface should be such that after from a metal sheet by subjecting one surface of desired markings have been produced thereon, the sheet to a graining treatment, and then subthe portions of the surface not coated with the jecting said surface to the action of an alkali markings or grease film may be subjected to a earth metal oxide and silica in the presence of treatment whereby those portions of the surface water. These compounds apparently react with will be rendered ink-repellent while the coated the metallic surface of the lithographic plate to portions remain very receptive to greasy subform a deposit or coating which is extremely restances such as lithographic ink. Consequently, ceptive to markings which may be impressed when the lithographic plate having an image imthereon by a grease-containing stylus such as pressed thereon is passed under a roller containa crayon or lead pencil, or which may be iming a grease ink, the ink will adhere only to that pressed thereon through ordinary carbon paper portion of the plate to which the grease film or or a typewriter ribbon. The deposit renders the markings have b pp and a reproduction surface of the metal treated very resistant to 01' t e markings y be transferred directly to oxidation and the treated plates may be stored the surface to be printed or to a cylinder having for long periods of time,

a rubber blanket which in turn transfers it to the The process of producing lithographic plates desired surface in accordance with the common of this invention may be continuous. In accordpmtlce. It is therefore important in the lithoance with one embodiment of this invention, a graphic art that lithographic plates have a surcontinuous thin metal strip is passed under a face which at one time is strongly receptive to revolving wire brush in order to remove foreign markings which may be produced by greasy mamaterial from one surface of the strip, and to t r als. ut w h surf s a so of s h a charimpart a desired grain thereto. The resulting deter that it y be treated to render it eas strip is then subjected to a scrubbing or brushrepellent except in those portions of the surface ing action in the presence of substantial quanto which the greasy film or markings have been titles of a mixture of lime, finely divided silica, applied. and water. During this scrubbing action a de- It is an object of this invention to provide an posit or coating forms on the surface of the i pr ved ith raph p at which is ap ble of metal sheet which is subsequently brushed and readily receiving a greasy film from any sort of washed with water and thoroughly dried. The a drawing instrument, stylus or stencil capable deposit or coating survives the subsequent washof depositing on said surface a grease-containing ing and drying operations and is of such a nature film in selected areas. that the surface of the resulting metal is very A further object of this invention is to provide receptive to grease markings imparted by cona continuous process of preparing a lithographic tact or to other images produced in accordance plate having the above indicated desirable charwith well known photolithographic processes. acteristics. The thus treated metal sheet may then be A further object of this invention is the promarked, scored, cut and packaged as desired.

vision of a flexible lithographi Plate and a It will, or course, be recognized that any type lithographic art. If desired, a. thin metal sheet may be employed which has a. paper backing adhesively secured thereto. Thi paper backing is preferably waterproofed and secured to the sheet metal with a waterproof adhesive, so that subsequent contact of the resulting plate with water during treatment and during use will not cause separation of the paper and metal sheet. Also, while it is preferred to employ a mixture of water, lime and finely divided silica as the treating agent for the plate to form the desired grease-receptive deposit, it has been found that other alkali earth metal oxides may b substituted for the lime. Suitable substitutes are the oxides of barium, magnesium, and strontium. Under certain conditions, various silica-containing abrasives may be substituted for the silica, or other finely divided abrasives may be used. such as pumice, finely divided argillaceous materials and the like. I However, I prefer to use finely divided silica of a fineness sufilcient to pass a 250 mesh screen. It is the combination of the alkali earth metal oxide with silica and water which appears to produce the desired coating or deposit. Under certain conditions, a water-soluble blue dye may be incorporated with the treating mixture in order to impart a desirable whiteness to the coating on the resulting plate. Only traces of the blue dye may be used, a suitable one being a water-soluble dye known as benzoyl blue.

For a more complete understanding of this invention, reference will now be had to the drawing, wherein Figure 1 is a diagrammatic elevational view of an apparatus which may be used for a continuous process of producing a lithographic plate in accordance with one embodiment of this invention.

Fig. 2 is a greatly enlarged partial sectional view of a lithographic plate prepared in accordance with one embodiment of this invention, having the coating or deposit of ink-receptive material thereon.

Fig. 3 is similar to Fig. 2. but shows a product having a backing of waterproofed paper adhesively secured to the sheet.

Referring now more particularly to Fig. l, a roll ill of thin sheet metal is provided which is capable of being unrolled to advance a continuous strip of metal l2 over a table M of Monel metal, glass, or other corrosion-resistant material, by means of drawing rolls I 6. The sheet l2 may be a thin metal sheet of aluminum or zinc or other lithographic metal having a thickness of about liooo inch. Such a sheet is flexible and is, when treated, capable of being inserted into the carriage of an ordinary typewriter and positioned on the drum of an ordinary lithographic machine. If desired, the metal sheet l2 may be provided with a paper backing It, as indicated in Fig. 3. In such case, the metal sheet may have a thickness of about @5000 inch, and the backing a thickness of about $5000 inch. The backing is preferably waterproof paper, and adhered to the metal sheet l2 by means of a waterproof adhesive. It will be understood. of course, that the metal sheet or the metal sheet and paper backing may be of any desired thickness and I do not wish to limit myself to the particular asiaoav dimensions indicated above. The metal surface of the strip l2 has been, prior to the time that it is rolled into the roll 10, treated with a wire brush, in order to remove foreign matter from the surface of the metal and to provide a. suitable roughness or grain to the surfac of the strip to be treated.

The strip I 2 having the grained surface is pulled continuously from the roll I0 by means of the drawing rollers it under a spout 20 of a receptacle 22 having contained therein a mixture 24!, which is deposited on said strip. The mixture 26 preferably comprises about two parts by weight of calcium oxide, about two parts by weight of finely divided silica, and about eight parts by weight of water. A small amount of benzoyl blue may also be added thereto in order to provide a desired whiteness to the coated surface of the resulting product. The mixture 2% within the receptacle 22 is continuously stirred by a paddle 26 operated by means (not shown) through a belt 28. By this means, the ingredients in the mixture 24 are kept in uniform suspension and undesirable settling is prevented.

The mixture 24 is deposited through the spout 20 onto the grained surface of the metal sheet it which is continuously advanced under a doctor blade 30 serving evenly to distribut the mixture over the entire surface of the sheet. The thus covered sheet is then passed over the table It and under a plurality of oppositely rotating brushes 32 which serve to scrub the surfaces of the sheet in the presence of the mixture of lime, silica, and water, and to thoroughly contact the mixture with the grained surface of the sheet. The sheet I2 is then advanced under a squeegee it in order to remove excess quantities of the mixture, and then is advanced under a plurality of washing brushes 36 which also rotate in opposite directions and serve to remove all traces of excess quantities of silica and lime from the surface of the sheet. Water for the washing plurality of pipes 38 positioned thereabove. The

corrosion-resistant table Iii serves as a backing for the scrubbing brushes 32 and the washing brushes 36.

The strip l2, after having been washed, is then passed under a cloth-covered wiping roll 39 and between the drawing rolls l6, which latter serve to pull the sheet l2 across the table It, and which also serve to squeeze excess quantities of water from the sheet l2, in case such sheet has a paper backing, as indicated in Fig. 3. The sheet I2 is then advanced through a drying chamber to, which is equipped with a plurality of drying lights 42 positioned above and below the sheets. The product here may be re-rolled if desired and may be subsequently marked, out and packaged as needed. However, as shown in the drawing, it is fed directly from the drying chamber 40 into a printing mechanism M, which prints, with water color ink, markings to serve as guide marks on the resulting product, and thereafter it is fed into a scoring device 46, and to the cutters it, which serve to cut the sheet to the desired lengths. The separate sheets may then be stacked and packaged in any desired manner.

It will, of course, be recognized that both surfaces of the strip I2 may be treated in accordance with this invention. It is, in such a case, necessary to subject both sides to a prior wire brushingbr graining operation before treating the product as herein disclosed. This double treatment may be applied to both sides of a metal sheet or to the exposed surfaces of two metal sheets adhered to each side of a waterproofed paper backing by a waterproof adhesive.

It has been discovered that a lithographic plate prepared in accordance with the process indicated above has many desirable properties which make it superior to lithographic plates which have heretofore been used in the art. It is very receptive to grease, and is consequently very useful for accurately reproducing grease markings which may be impressed thereupon. After desired markings have been impressed on the plate, either mechanically by a typewriter or other drawing instrument or by a photolithographic operation, the surfare of the plate may be wiped with a sponge containing a solution which is known in the lithographic art as an etch solution whereby those portions of the surface not containing the greasy material or photographic image are rendered ink-repellent. A particularly useful etch solution prepared in accordance with this invention has the following composition solution to about pH 3.8

This etch has properties which make it, superior to other etches of which I am aware.

After the plate has been treated with the etch solution, it may be mounted on the drum of a lithograph machine and a grease ink may be applied to the surface of the plate by means of a roll. The ink will adhere only to those portions to which the grease film or markings have been applied and the grease ink on these markings may then be transferred directly to the surface to be printed or to a cylinder having a rubber blanket which in turn transfers it to the surface to be printed. A fountain etch may be applied to the plate by means of a water roll on the lithograph machine in order to insure that the ink-repellent portions of the plate will retain their ink-repelling properties. In accordance with one embodiment of this invention, a suitable fountain etch is one which may be prepared by adding an equal quantity of glycerine (Y. D.) to the etch composition given above,

Plates prepared in accordance with this invention retain their accuracy of reproduction over long periods of time and may be used indefinitely. They are also very resistant to oxidation and the plates may be stored for long periods of time and re-used. This non-oxidizing coating imparted to the surface of the metal in accordance with this invention may be applied to other metal articles such as they be employed in structural work but, of course, it finds particular use in the preparation of lithographic plates as herein described.

An important feature of the present invention is the provision of a lithographic plate which has been treated with a mixture of water, an alkali earth metal oxide and silica. Any desired proportions may be used but I have discovered that best results are obtainable when about equal parts of the oxide and silica are used in admixture with a somewhat greater amount of water. This mixture when applied as indicated above forms a deposit or coating on the surface of the lithographic plate. This coating is indicated at 50 in Figs. 2 and 3. I do not understand what the true nature of this coating is, nor do I understand the nature of any physical or chemical reactions that may be involved in its formation. However, I do know that the use of the mixture indicated results in an improved lithographic plate which is much more receptive to grease images than are plates which have been prepared and cleaned with ordinary abrasives or chemical cleaning agents.

The plate of this invention is extremely finegrained and is capable of transferring an extremely accurate image. Markings of lead pencil, crayon and grease ink on the plate are accurately reproducible and are readily distinguishable one from the others on the surface printed with the plate of this invention. The markings on the plate can be erased in case corrections are desired while the markings are being applied thereto. Erasures may be made by a stiff glass fiber brush or by means of a suitable solvent, such as a mixture of equal parts of trichlorethylene and acetic acid. The erasures are indistinguishable in the reproduction and fresh markings may be applied to the plate over the erasures.

While particular embodiments of this invention are shown above, it will be understood, of course, that the invention is not to be limited thereto, since many modifications may be made, and it is contemplated, therefore, by the appended claims, to cover any such modifications as fall within the true spirit and scope of this invention.

I claim:

1. A process of preparing a lithographic plate which comprises imparting a grain to one surface of a metal sheet, treating said surface with a mixture of an alkali earth metal oxide, silica and water, washing said mixture therefrom, and drying the resulting product, whereby said surface has been rendered strongly receptive to impressed greasy markings.

2. A process of preparing a lithographic plate which comprises imparting a grain to one surface of said plate, Scrubbing said surface in the presence of a mixture of lime, finely divided silica and water, washing said mixture from said surface, and drying the plate, whereby said surface has been rendered strongly receptive to impressed greasy markings.

3. A process of treating the surface of a metal plate to render it strongly receptive to impressed greasy markings comprising imparting a grain to said surface, brushing said surface in the presence of a mixture of lime, finely divided silica and water, then washing said mixture from said plate, and drying the same.

4. A process of treating the surface of a metal plate to render it strongly receptive to impressed greasy markings comprising the steps of wirebrushing said surface to impart a grain thereto, depositing a mixture of lime, silica and water on said surface, brushing said surface in the presence of said mixture with a plurality of oppositely rotating brushes, washing and brushing salidt mixture from said surface, and drying the p a e.

5. A process of treating the surface of a metal strip to render it strongly receptive to impressed greasy markings comprising imparting a grain to said surface, continuously advancing said strip, depositing a mixture of lime, silica and water on said surface, brushing said surface in the presence of said mixture as the strip continuously is advanced, then washing said mixture from said surface, drying the same, and cutting the strip into predetermined lengths.

6. The process of claim 5 in which said strip is continuously marked and scored prior to cutting. '7. An etch solution for treating the surfaces of lithographic plates comprising water, glycerine, mono-ammonium phosphate, ammonium sulfate and phosphoric acid.

8. A process of preparing a lithographic plate which comprises treating the surface of said'plate with a mixture of an alkaline earth metal oxide, finely divided silica and water whereby a grease receptive coating is formed thereon, applying desired grease markings to said surface, and treating said surface with an etch to render greaserepellent those portions of the surface not covered with the markings, said etch comprising an aqueous solution of glycerine, mono-ammonium phosphate, ammonium sulfate, and phosphoric acid, whereby to form a fine-grained plate capab'e of transferring an extremely accurate image of said grease markings.

9. A process of preparing a lithographic plate which comprises imparting a grain to one surface of a metal sheet, treating said surface with a mixture of an alkali earth metal oxide, a finely divided abrasive and water, washing said mixture therefrom, and drying the resulting product, whereby said surface has been rendered strongly receptive to impressed greasy markings.

10. A lithographic plate comprising a thin flexible metal sheet having the normal lithographic surface thereof grained and treated with a mixture of an alkaline earth metal oxide, a finely divided abrasive, and water to provide a greasereceptive coating thereon.

11. The lithographic plate recited in claim 10 wherein said abrasive comprises silica.

12. The lithographic plate recited in claim 10 wherein said alkaline earth metal oxide comprises lime.

13. The lithographic plate recited in claim 10 wherein said sheet comprises aluminum.

14. The lithographic plate recited in claim 10 wherein a sheet of waterproofed paper backing is adhesively secured to the opposite surface of said metal sheet.

15. A lithographic plate comprising a thin flexible aluminum sheet having the normal lithographic surface thereof grained and abraded with a mixture of lime, finely divided silica, and water to provide a grease-receptive coating thereon.

WILLIAM T. HAGELIN.

Images