US3269308A - Dilatant plastic printing plate - Google Patents

Description

United States Patent M 3,269,308 DILATANT PLASTIC PRINTING PLATE Daniel L. Goffredo, 104 Main St., Riverton, NJ. N0 Drawing. Filed Mar. 27, 1963, Ser. No. 271,834 2 Claims. (Cl. 101-395) This invention is for a new composition and method for making duplicate printing plates with unique printing properties.

Printing plates have been made of hard materials like wood, lead (type metal), zinc, magnesium and various hard plastics. Printing plates have been made of soft resilient materials like the various rubbers. The harder materials give a sharper printing impression, but do not conform to the irregularities in the printing couple. By printing couple is meant that area of a printing press where ink is transferred from the printing plate to the paper. The soft resilient materials do not give as sharp a printing impression as the hard materials but do conform to irregularities in the printing couple. As is obvious from the comparison of hard and soft printing plates, they both have advantages. The hard plate is advantageous for quality Work. The soft plate is advantageous for conformity when there are irregularities in the printing couple.

The modern letterpress printing industry has been demandin-g a higher speed of printing productivity. In order to accomplish this high speed of productivity, the industry has been shifting from flat printing plates to curved printing plates. Many problems are encountered in making curved plates of hard materials such as type metal, zinc and magnesium engravings, electrotypes, and the various hard plastics. It is difiicult to curve these materials to conform exactly to the printing couple. Much time is spent in makeready in order to obtain a good uniform contact along the printing couple. However, when finally made ready for printing, the hard type of printing plate gives the best type of reproduction. Because of this problem in making curved plates of hard materials, the printing industry has turned to flexible rubber printing plates. This need has been so acute that a whole new rub-ber printing plate industry has recently grown up, called flexographic printing. The flexible rubber plate fulfills the need for a plate that is easily curved to fit the printing cylinder. It, also, readily conforms to irregularities in the printing couple because of the compressibility of rubber. However, it has one serious drawback, it is limited to the coarser types of reproduction. The compressive nature of the rubber causes distortion of the printing image. This is less objectionable when printing lines, but is very objectionable when printing halftones, especially in color printing.

It is the principal object of this invention to provide a composition and method of making duplicate printing plates with unique physical properties. This new printing plate is neither hard nor soft in the sense described of the conventional printing plates. This new printing plate material is dilatant. D-ilatancy is best defined as system that exhibits a higher degree of resistance to deformation at higher speed loading than it does to low speed loading. dilatant printing plate has the flexible properties of the rubber printing plate but gives greater resistance to compression at high rates of sheer, i.e. at high printing speeds. Also, compression lowers the highs and centrifugal force tends to raise the low spots. The advantage of this new printing plate now become obvious in that a higher quality printing job can be done because the finer character of type and halftone dots are not readily compressed and distorted. In essence, it is a flexible printing plate that offers a semi-hard print-ing surface. This dilatant printing plate gives the printer the answer to a long standing problem called makeready,

Patented August 30, 1966 because this printing plate can conform to irregularities in the printing couple but still offer resistance to distortion while printing.

I have found that certain plastics can be formulated to give dilatant printing plates by the addition of certain plasticizers. This dilatant plasticizing effect can be achieved by adding an excess of curing agent, chlorinated biphenyl, chlorinated polyphenyls or other plasticizers that give a colloidal type of solution. These plastics can be selected from the thermosetting or thermoplastic groups. Examples of specific plastics are epoxy, polyurethane, polyester, acrylic, vinyl, styrene-butadiene and polyethylene. These plastics can be formulated as liquids to pour over the printing form to be reproduced in order to make the matrix or duplicate printing plate. Heat may be used to cure the plastic resin. Also, the plastic composition can be formulated as a paste-like or solid composition but then heat or/and pressure would be required tomold against the form to be reproduced. This composition and method allows the making of dilatant duplicate plates out of any printing form, such as engravings, type-metal compositions and the such. This composition and method allows the modern letterpress industry to convert any flat printing form into a new and unique form that is easily curvable and readily conformable to the irregularities in the printing couple.

More specifically I will describe my invention in terms of an epoxy resin.

EXAMPLE I A liquid composition to produce a dilatant plate Parts by weight Liquid epoxy resin 2 457 Chlorinated biphenyl 395 Curing agent 148 A molded newspaper mat was coated with a polyvinyl alcohol release agent and dried. The mat was held fiat on a vacuum table and surrounded with a dam. The liquid plastic composition was poured onto the mat and confined within the area of the dam. The liquid plastic was poured to the depth required of the printing plate. The mat and liquid plastic were heated to F. Within 15 minutes the liquid plastic cured and was lifted from the mat. The plastic was found to be an excellent reproduction of the mat. It was, also, flexible and could easily be wrapped on a printing cylinder. On printing, the small dots and fine lines printed faithfully, they printed like a hard metal surface. The printing plate was found to be dilatant.

EXAMPLE II A liquid composition to produce a dilatant plate Parts by weight A newspaper mat was coated with a polyvinyl alcohol release agent. The mat was then molded. The mat was held down on a vacuum table and surrounded with a dam. The liquid plastic composition was poured onto the mat and confined with the area of the dam. The liquid plastic was poured to the depth required in the printing plate. The mat and plastic were allowed to cure at room temperature overnight. The next morning the plastic was lifted from the mat and it was found to be a harder dilatant printing plate than Example I.

Whereas, -I have specifically described by invention in terms of a liquid epoxy composition, this should not limit the scope of my invention. Dilatant plastic printing plates can be prepared from liquid or semi liquid com- References 1 Defining dilatant property:

Handbook of Fluid Dynamics (7-4) by Victor L. Streeter, Editopin-Chief, McGraw-Hill Book Co., New York, 196 1.

The International Dictionary of Physics & Electronics (page 240) D. Van Nostrand C0,, Inc, Princeton, N. J 1956.

2 An epichlorohydr-in bis-phenol A derived liquid epoxy resin with an assay approximately of 190 grams of resin per gram mole oxirane oxygen.

Curing agent consists of 30 parts by Weight bisphenol A and 100 parts by weight N-hydroxyethyl diethylene triamine.

I claim as my invention:

1. A printing plate with relief indicia; the printing surface is of a dilat-ant composition which yields under slow shear forces but resists high rates of shear; the surface composition, also, has the property of returning to its initial configuration when distorted out of such configuration by pressure, when the pressure is removed; and the composition is readily bendable and will conform to the printing drum with minimum makeready time while being self supporting and always returning to its initial configuration, after the distorting force is removed.

2. The printing plate according to claim 1, wherein the dilatant composition comprises an epoxy resin.

References Cited by the Examiner UNITED STATES PATENTS 2,302,037 11/1942 Kollek 101 395 2,517,701 8/1950 Oettinger 18-56 2,571,397 10/1951 Wells 1s 5s 2,775,572 112/1956. Fisk 26045.5 3,055,297 9/1962 Leeds 101--40 1.1 X 3,145,654 8/1964- Johnson etal 101 401.1

FOREIGN PATENTS 713,990 8/1954 Great Britain.

DAVID KLEIN, Primary Examiner.

WILLIAM B. PENN, Examiner.

R. H. BERN'EIKE, HERMAN STRNISHA,

Assist/mt Examiners.

Claims (1)

1. A PRINTING PLATE WITH RELIEF INDICIA; THE PRINTING SURFACE IS OF A DILATANT COMPOSITION WHICH YIELDS UNDER SLOW SHEAR FORCES BUT RESISTS HIGH RATES OF SHEAR; THE SURFACE COMPOSITION, ALSO HAS THE PROPERTY OF RETURNING TO ITS INITIAL CONFIGURATION WHEN DISTORTED OUT OF SUCH COMFIGURATION BY PRESSURE, WHEN THE PRESSURE IS REMOVED; AND THE COMPOSITION IS READILY BENDABLE AND WILL CONFORM TO THE PRINTING DRUM WITH MINIMUM MAKEREADY TIME WHILE BEING SELF SUPPORTING AND ALWAYS RETURNING TO ITS INITIAL CONFIGURATION, AFTER THE DISTORTING FORCE IS REMOVED.