US 3663289 A
Planographic printing plates and continuous planographic printing forms having a flexible foundation supporting a planographic printing layer and process of making are disclosed. The flexible foundation is an opaque, thin sheet or continuous web or strip of synthetic thermoplastic polymer having uniformly rough, receptive surfaces, the foundation being selected from unicellular foamed film or normally-clear, normally-smooth film treated on both surfaces with volatile organic solvent having a dissolving power therefor. One surface of the film foundation is coated with a thin planographic layer.
Description (OCR text may contain errors)
United States Patent Newman [451 May 16, 1972  PROCESS OF PRODUCING A PLANOGRAPHIC PRINTING PLATE AND RESULTAN T ARTICLE  Inventor: Douglas A. Newman, Glen Cove, NY.
 Assignee: Columbia Ribbon and Carbon Manufacturing Co., Inc., Glen Cove, NY.
 Filed: Apr. 6, 1970  App1.N0.: 26,091
Related US. Application Data  Continuation-impart of Ser. No. 800,414, Feb. 19,
 U.S.Cl ..117/4,96/33,10l/401.1, 101/453, 101/460, 117/47 A, 117/68, 117/76 F,
117/138.8 R, l17/l38.8 UA,117/138.8 E
 1nt.Cl. ..B44d 1/14,B4ln H12  FieldofSearch ..117/76F,70R,l38.8UA,138.8R, 117/98 F, 47 A, 4; 101/453, 401.1, 460, 461, 462;
 References Cited UNITED STATES PATENTS 2,139,214 12/1938 Wahl ..l17/4X 2,384,657 9/1945 Tyler ..1 17/4 2,941,466 6/1960 Newman et al. ...l0l/46O 3,055,295 9/1962 Perkins 10 l /462 3,250,731 5/1966 Buhl et a1 ..264/53 3,256,810 6/1966 Ensink [01/461 3,311,497 3/1967 Park ..117/47 X 3,470,013 9/1969 Wagner 101/453 X Primary Examiner-William D. Martin Assistant ExaminerRalph l-lusack Attorney-lohnson & Kline [5 7] ABSTRACT 7 Claims, 3 Drawing Figures PATENTEDMAY 16 m2 ooonooe o oooloooooooooo ooo oooooooecoooooooo VOOOOOOO INVENTOR. flmgylas A. Mew/27am fi 7' '04QA/EY$ PROCESS OF PRODUCING A PLANOGRAPHIC PRINTING PLATE AND RESULTANT ARTICLE This application is a continuation-in-part of parent application Ser. No. 800,414, filed Feb. 19, 1969, now abandoned.
Planographic printing plates conventionally have a paper foundation supporting the planographic printing layer and are frequently used in multi-sheet continuous forms as one of the copy sheets imaged by means of a chain printer machine or other type printer. Images are printed on the copy sheets by means of a ribbon and/or interposed transfer sheets and the imaged copy sheets are then torn from the continuous strip and used for their intended purposes. The copy sheet which is a planographic printing plate is wetted with etching fluid, mounted on a planographic printing machine and duplicate copies are made therefrom.
In order to be useful for continuous forms use, the planographic web must be capable of being perforated to form pinengaging holes along both edges of the web for transport of the web through the printing machine and/or capable of being perforated with weakened tear lines separating successive plate lengths whereby each imaged plate can be torn from the web for use in the planographic printing machine. Even for conventional use, many planographic printing machines require that the plate have clamping holes or scalloped edges for clamping the plate on the printing cylinder.
Planographic printing plates, regardless of type, must have certain properties in order to function properly in the planographic printing process. They must be capable of accepting and retaining water on the unimaged areas of the planographic surface. lt is the function of the planographic layer to accept moisture but, since such layer must be porous in order to retain the oleophilic images applied thereto, the plate foundation must not absorb the water to any great extent.
Nearly all planographic printing plates have a paper foundation except in specialized fields such as photosensitive plates and thermographic plates. Paper is capable of being perforated and thus is the only material used for plates in the continuous forms field discussed supra. Paper, however, is normally highly absorbent of water and thus requires wet strength treatment and treatment of one or more interposed water barrier layers beneath the planographic printing layer to reduce the tendency of the paper foundation to absorb the water from the printing layer. Paper plates having such treatment still absorb water to a high degree and require continuous moistening during duplication.
Moreover such paper plates often have a tendency to curl rather than staying flat when the ambient conditions change and particularly when the ambient moisture or humidity level changes. They also have a tendency to change dimensions to a small but important degree with changes in the ambient conditions, particularly humidity. Such changes in flatness and dimensions are particularly important in certain applications such as when the plates are used in continuous forms with marginal perforations which must align with the web-transporting pins on the printing machine, and when the weakened tear line perforations which separate plate lengths must be in registration with similar perforations on the other sheets of the form such as the transfer sheet.
It is known to use waterresistant plastic film foundations in place of paper foundations to produce specialized plates which are photosensitive or transmissive of light or infrared radiation to a high degree. Such films are limited to these areas because of the difficulty of processing, coating, cutting, and handling plastic film and the poor receptivity and retentivity of plastic film for planographic printing layers. Also filmbase plates are not used in many applications including continuous forms because of the difficulty of cutting and perforating thin films or forming weakened severing lines thereon.
The present invention is concerned with providing planographic printing plates having foundations which comprise the advantageous properties of paper and plastic film foundations but which do not have the disadvantageous properties of either of these materials.
This and other objects and advantages of the present invention will be apparent to those skilled in the art in the light of the present description including the drawing in which:
FIGS. 1 and 2 are diagrammatic cross-sections, to an enlarged scale, of planographic printing plates according to different embodiments ofthe present invention, and
FIG. 3 is a plan view of a section of a perforated continuous form planographic printing plate according to another embodiment of the invention.
The novel planographic printing plates of the present invention comprise an opaque, thin, water-impervious foundation 1 of synthetic thermoplastic polymer having uniformly rough, receptive surfaces supporting directly or indirectly on one of said surfaces a planographic printing layer 3, as shown by P16. 1 of the drawing. The foundation according to the embodiment of the drawing comprises a foamed film which is extruded as such and is of the closed cell or unicellular type as opposed to the open cell or sponge type. Unicellular foam films are defined as those films having at least 50 percent of the cell content in the form of closed cells 4. Such films are opaque in appearance and have uniformly rough surfaces 5 which are porous and exceptionally receptive to and retentive of planographic coatings and imaging materials. The surfaces 5 of such films appear relatively smooth and continuous to the eye and are substantially impervious to water.
According to another important embodiment, the foundation comprises a thin, normally smooth, clear film of synthetic thermoplastic polymer which has been treated on both surfaces with a volatile organic solvent which softens or dissolves the polymer at the film surfaces to render the surfaces frosted and opaque in appearance. The treated surfaces are rendered uniformly rough and given a surface porosity whereby they are exceptionally receptive to and retentive of planographic coatings and imaging materials.
The specific composition of the planographic layer 3 of the present plates is not critical to the invention since the receptive film support provides advantages over the use of paper and conventional plastic film supports regardless of the nature of the planographic layer and whether it is electrostatic or sensitive to light of heat. Planographic layers having a hydrophilic-oleophilic balance are generally applied as aqueous dispersions containing a hydrophilic film-forming binder material, cross-linking agent to insolubilize the binder, filler, wetting agents, pH modifiers and other ingredients such as zinc oxide in electrostatic plates and photosensitive materials in photosensitive plates. The following US. patents are incorporated by reference insofar as the planographic compositions and coating procedures thereof are suitable for preparing plates according to the present invention in which the opaque, porous-surface-film support is used in place of prior-known supports: US. Pat. Nos. 2,534,650; 2,941,466; 3,055,295; 3,256,810; and 3,323,451.
The foamed-film foundations suitable for use according to one embodiment of this invention are extruded under pressure in conventional manner from foam-forming compositions comprising a synthetic thermoplastic resin, a blowing agent and, preferably, a nucleating agent. Fillers and colorants may be included as desired. The composition is generally extruded in the form of an expanded tube which is then flattened, trimmed, cut into sheet or web dimensions and separated.
The preferred resin is polystyrene which is commercially available in the form of expandable polystrene pellets which contain the blowing agent and other ingredients which assist to expand the melted polymer internally. However a variety of other resins may be used including acrylic polymers and copolymers, butadiene copolymers, hydrocarbon polymers such as polyethylene and polypropylene, polymers and copolymers of styrene derivatives, and the like. The following United States patents are incorporated by reference insofar as they relate to expandable resin compositions and the production of foamed films suitable for use according to the present invention: US. Pat Nos. 3,121,760; 3,248,462; 3,250,731; and 3,287,477.
The foamed films suitable for use herein are unicellular, i.e., have at least 50 percent of their cell content closed, are light in weight in that they contain at least about 10 percent of their volume in the form of gas within the cells and have a thickness of from about 1 mil up to 10 mils and preferably from about 3 to 6 mils.
The following examples are given by way of illustration and should not be considered limitative.
A web of expanded polystyrene is produced according to Example 1 of US. Pat. No. 3,248,462 and has a thickness of about 4 mils (0.004 inch). The web is light in weight in that over half of its thickness comprises gas trapped within the cell structure. The web is also opaque white in appearance due to the cell structure. Referring to the present drawing, the foamed film 1 comprises an expanded matrix 2 of the polystyrene binder containing a multiplicity of closed cells 4. The surfaces 5 of the film are rougher and substantially less smooth than a cast, homogeneous film although the surfaces appear relatively smooth to the naked eye.
The web is converted into a planographic printing plate by applying the planographic layer directly thereto or by first applying a hydrophilic underlayer. The underlayer is most important in cases where the plate must be correctable. If erasures are made on the planographic layer, a portion of the layer may be eroded and therefore it is important to have a hydrophilic layer beneath. Such layers are well known in the planographic plate art.
According to the embodiment of FIG. 1 of the drawing, the following planographic composition is applied directly to the surface of the foamed film in a weight of 8 pounds per ream (3,300 sq. ft.) and dried in conventional manner.
lngredients Parts by Weight Polyvinyl alcohol 2.0
Syton (40% aqueous colloidal silica) 12.0 Glyoxal (40% aqueous solution) 0.5 Clay 16,0 Alum aqueous solution) 10.0 Zinc acetate 4.0 Acetic acid (25% aqueous solution) 0.2 Water 55.3
The dried planographic layer 3 firmly anchors to the relatively rough surface 5 of the foundation and resists picking or peeling therefrom during flexing and use.
According to the embodiment of FIG. 2, the foamed-film foundation is first coated with the following hydrophilic composition in a weight of about 4 pounds per ream and dried in conventional manner.
The dried undercoating 6 is hydrophilic and the planographic layer 7 is applied thereover in the manner discussed supra in connection with the plate of FIG. 1.
The coated webs having the structure shown by either FIG. I or H0. 2 can then be cut into sheet lengths for use in conventional manner or may be perforated in conventional manner for use as a continuous strip or for collation into a multi-sheet continuous form. FIG. 3 of the drawing illustrates a continuous strip 8 of plate according to this invention and shows the planographic surface 9, marginal feed perforations l0 and weakened tear perforations 11 for separating sheet lengths.
Solvent-treated film foundations may be employed in place of the foamed foundation of the examples recited hereinbefore. Such films are produced by providing conventional thin,
clear films of synthetic thermoplastic polymer, treating the surfaces with volatile solvent to cause surface dissolution of the films, and then evaporating the solvent to provide films which are opaque in appearance and having uniformly rough surfaces which are porous and receptive. The film and solvent should be selected so that the solvent is not such an active solvent for the film that the internal strength of the film is destroyed. Solvent action must be limited to the film surface so that only surface porosity is produced and rupture of the film is prevented. Dilute solvent solutions may be used and/or the duration of exposure of the film to the solvent may be restricted to produce the desired results. This latter result may be accomplished by immersing the solvent-treated film into a non-solvent at the desired time to instantaneously stop the solvent action. For instance a smooth, thin, clear film of polystyrene film, such as Dow Trycite, may be immersed into a solvent bath comprising a 5 percent solution of acetone in water for a period of 1 second and then immediately immersing the treated film in Water to stop the solvent action and produce an opaque polystyrene film having the desired surface porosity.
Such solvent-treated films are found to have the appearance, feel, and cutting properties of paper while retaining the flexibility, strength, and impervious nature of plastic film. They can be marked, coated, cut, perforated, and punched as easily as paper and thus function perfectly according to the present invention.
Because of the receptivity of the present film supports for coatings, the present plates are particularly well adapted for the application of a pressure-sensitive transfer layer to the surface thereof opposite the planographic surface. Reference is made to my US. Pat. No. 3,274,928 relating to such bifunctional plates. The application of a conventional copying layer is particularly useful when the present plates are used in multisheet forms whereby a carbon copy or duplicate planographic printing plate is produced simultaneously with the imaging of the instant plate. The presence of the carbon transfer layer on the back of the plate avoids the necessity of interposing a separate carbon paper in the form. The reduced thickness and also the pressure-deformability of the present plate foundations makes it possible to produce sharper and clearer images on the plate surface and on the underlying copy sheet or sheets.
Plates in sheet or continuous strip form produced according to the present invention have excellent dimensional stability. They are flat and resist curling under the effects of changes in the ambient conditions such as increases or decreases in humidity. They do not absorb moisture and therefore the plates neither shrink nor expand to any important extent under the effects of changes in humidity and/or temperature. Therefore any perforations made in such plates such as for purposes of transporting continuous strips thereof or for tearing such strips into sheet lengths or for mounting such plates on a planographic printing drum remain accurate in position under varying atmospheric conditions.
Variations and modifications may be made within the scope of the claims and portions of the improvements may be used without others.
1. The process of producing a planographic printing plate which comprises the steps of:
a. treating both surfaces of a normally clear, normally smooth synthetic thermoplastic film foundation with a volatile organic solvent having a dissolving power for said film to render said surfaces opaque and uniformly rough,
b. treating both surfaces of said solvent-treated film with a liquid which does not have dissolving power for said film to stop the solvent action of said organic solvent,
c. applying to one of the rough surfaces of said film a thin layer of an aqueous planographic composition comprising a hydrophilic binder material, and
d. drying said layer to form a thin planographic layer having a hydrophilic-oleophilic balance.
2. A planographic priming plate produced according to the process of claim 1.
3. The process of claim 1 in which an aqueous composition comprising a hydrophilic binder material is applied directly to the rough surface of the film and dried to form a thin hydrophilic undercoating, and the aqueous planographic composition is applied over said undercoating.
4. A planographic printing plate produced according to the process ofclaim 3.
5. The process of claim 1 in which the foundation is a continuous web and the coated web is cut into strip lengths and perforated to form a continuous planographic printing strip 6. A planographic printing plate which is dimensionally stable and moisture-impervious comprising a thin, flexible synthetic thermoplastic film foundation having uniformly rough opaque surfaces, said film being a unicellular foamed film having at least 50 percent of the cell content in the form of closed cells, one surface of said film foundation supporting a thin planographic layer having a hydrophilic-oleophilic balance.
7. A planographic printing plate according to claim 6 in which the foundation comprises expanded polystyrene.