Hydrophilic-hydrophobic Photon-sensitive Medium

Abstract

A medium which is hydrophobic when unexposed, and hydrophilic when photon exposed is employed to produce discrete photon-developed areas. The medium comprises a solid dispersion in a film-forming binder of a photoconductive sensitive material such as zinc oxide, a sensitization enhancing material such as a copper salt and a hydrophobicity inducing agent such as a water repellent silicone, fluorocarbon material or a higher molecular weight organic acid such as stearic acid or linoleic acid. Exemplary processes of developing the photon exposed medium include application of aqueous liquids to form visible and/or transferable or relief images.

Description

BACKGROUND OF THE INVENTION

This invention is directed to employment of a medium to produce an image. The image is such that it is hydrophobic when unexposed and hydrophilic when exposed. The hydrophobicity-hydrophilicity difference is employed to produce a useful or visible image.

The prior art abounds in silver halide media and other actinically sensitive media whereby a visible image is obtained by photon exposing the media and suitably developing and fixing the media to produce a visible image. The silver halide media and the processes employing the silver halide media are not the only other processes beyond the present process wherein physicochemical amplification occurs in the media to permit rapid image development from a fairly weak photon source. However, most of these processes require a fairly long development time, or involve other complex processing.

Other types of photon sensitive media are fairly "slow" in that they do not employ physical or chemical multiplication and require a much larger photon exposure before a usable image can result therefrom. For instance, processes used in diazo printing, and the media used in photoresists, are not of the nature which incorporate amplification of exposure, and thus they require very long exposures to be useful. Thus, the silver halide process requires considerable development time, while the remaining processes require a considerable exposure time, so that none of the prior art processes are capable of quickly producing a usable image from a normal photon source.

Additionally, in regards to use of photosensitive materials as a master lithographic and other printing processes, most of the conventional photosensitive materials are negative-working in that they produce a reversal of tones whereby photon exposed areas print dark and the nonexposed areas print light. This requires the additional step in processing of preparing an intermediate negative in order to produce a final positive print. Also the conventional presensitized printing plates do not have any ability to print grey scale, but print black and white. This requires the additional complication of utilizing a halftone screen to reproduce grey scale.

Copending applications, Ser. No. 717,503, filed Apr. 1, 1968, and Ser. No. 721,773, filed Apr. 16, 1968, disclose a hydrophilic-hydrophobic, photon-sensitive medium containing a photosensitive compound, a sensitization enhancing agent and a hydrophobicity-inducing agent dispersed in film-forming binder. The particular hydrophobicity agents disclosed are water or water bearing materials such as aqueous formaldehyde solutions.

OBJECTS AND SUMMARY OF THE INVENTION

This invention is directed to the discovery of new classes of hydrophobicity-inducing agents useful in preparing a hydrophilic-hydrophobic photon-sensitive medium and particularly to water-repelling agents such as silicones, fluorocarbons or organic acids containing two to 24 carbon atoms. The invention is also directed to various processes utilizing aqueous liquids to form images on the photon-developed medium.

On selective exposure of the medium a hydrophilic image is formed supported and surrounded by hydrophobic nonimage or background areas. The materials may be dispersed in a film-forming binder to form a film which may be either self-supporting or may be supported upon a suitable substrate. A dispersion of the materials in the binder may be formulated by forming a liquid dispersion of the agents, materials and binder in a liquid, suitably a solvent for the film-forming binder. After thorough mixing, the film is formed as a self-supporting film or as a coated film and is permitted to dry. In such a state the medium is photosensitive and hydrophobic and is ready for further processing in accordance with the invention.

The invention will now become better understood by reference to the following detailed portion of the specification when considered in conjunction with the claims and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational view with a front housing cover removed of a photon exposure aqueous development imaging system employing the medium in a first process of this invention.

FIG. 2 is a schematic illustration of a lithographic printing process in accordance with the invention.

FIG. 3 is a schematic illustration of a deposition process in accordance with the invention; and

FIG. 4 is a schematic illustration of an etching process in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The hydrophilic, photon-sensitive medium in accordance with the invention, consists of a material which is sensitive to the impingement of photons, a metallic compound which is a sensitization-enhancing agent, a material which selectively renders the medium hydrophobic or hydrophilic in accordance with the photon exposure and a binder for forming a solid solution or dispersion of these ingredients in the form of a film. In some cases the strength of the binder is sufficient to form a self-supporting film and in other cases the film is supported on a substrate.

The substrate is a passive structure which does not enter into the activity of the photon-sensitive medium, except to act as a supporting structure, substrate or carrier. Therefore, the role of the substrate is entirely physical and mechanical as far as the practice of the invention is concerned. Suitable support substrates may be formed of almost any material and may partake of almost any geometry. Thus, paper, and especially paper in the form of a tape, may serve as suitable support substrate and is particularly desirable because of its flexibility. A number of synthetic polymer composition materials are also suitable. For example, the substrate may be formed of thermoplastic or thermosetting materials such as polyethylene, polypropylene or styrene polymers such as butadiene-styrene, polyesters such as polyethylene-terephthalate, acrylics such as methyl methacrylate, or cellulose derivatives such as cellulose acetate and the like.

Flexible substrates permit processing from continuous roll supplies and conformation of the finished and developed media to arcuate-shaped printing rolls and the like. However, rigid substrates can just as well be used for flat planographic printing, etching of printed circuit boards and the like. Rigid substrates can be formed of synthetic polymer composition materials, glass, metal, ceramic, refractory or impregnated woven sheets such as impregnated phenolic printed circuit boards and the like.

A satisfactory binder or matrix for forming the film of photosensitive media, according to the invention, may be any of the well known film-forming synthetic organic resins, particularly those formed of vinyl, diene monomers of their mixtures. The vinyl monomers may be ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl esters such as vinyl butyrate and preferably are vinyl aromatics such as styrene or vinyl toluene. The diene monomers may be C.sub.4 to C.sub.10 dienes such as butadiene, isoprene, methyl butadiene, dimethylbutadiene and the like. A typical binder of the styrene-butadiene type of copolymer which has been used successfully in the practice of the present invention, is one identified as "Pliolite S-7" (30 percent solids in toluene), manufactured by Goodyear Tire and Rubber Company, Chemical Division, Akron, Ohio. Other satisfactory matrix materials are polystyrene, chlorinated rubber, polyvinylidene chloride, polyvinyl butyral and the like.

A solid dispersion or solution of the active materials may be within the matrix or binder may be formed by any of the well-known techniques such as by adding a solution or dispersion of the materials to a solution or emulsion of binder particles, intimately mixing and then drying. Suitably, the binder is dissolved in a solvent to form a solution of reduced viscosity and the solid materials are added to the solution and dispersed therein. Any suitable solvent may be utilized to adjust the miscibility and spreadability of the dispersion. For styrene-butadiene resins such as Pliolite, the solvent may be an aromatic such as toluene or an ether such as dioxane. Other solvents for butadiene-styrene resins are chlorinated hydrocarbons and some ketones.

The solvent or dispersion may be cast onto a release surface to form a self supporting film or the material may be applied to the surface of a substrate, support or backing material by flow coating, dipping, spraying, doctor blade or other conventional coating operation. On removal of the solvent, the media is ready for further processing to form images by exposure and development.

The photosensitive material suitable for use in the practice of the present invention, appears to include materials which are classifiable as either photoconductive or photoemissive. The material is sensitive to the impingement of electrons, ions or photons. In general the photosensitive compounds are solids formed from one element to the left of Group IV of the Periodic Chart of the Elements compounded with another element from a group of the Periodic Chart to the right of Group IV. Preferably the photosensitive materials for use in recording media, according to the invention, are selected from compounds formed by elements of Group II such as zinc, calcium, cadmium and magnesium with elements of Group VI such as oxygen, sulfur and selenium.

More particularly, the sensitive materials for use in the recording media of the invention, include compounds such as the oxides of zinc, titanium, tantalum indium, magnesium, germanium, tin and bismuth as well as sulfides and selenides of calcium, zinc, cadmium, iron and indium. In addition to these, it has been found that such compounds as boron nitride, calcium tungstate, beryllium aluminide, lithium carbonate, zinc carbonate, cadmium niobate, lithium niobate, anthracene and certain phosphor compounds such as cesium-activated calcium-magnesium silicate may also be employed, as well as the mixtures of these compounds.

The sensitization-enhancing materials suitable for use in the practice of the invention are, in general, any of the metal compounds such as ionic salts or covalent bonded or coordination complexes thereof. The metal is suitably a Group I or IV element such as copper, bismuth, chromium, or silver. Typical inorganic salts are formed with inorganic anions such as halogen, oxygen, sulphate, sulfite, thiocyanate, sulfide, molybdate, sulfite and nitrate and the like. Salts of organic acids may also be utilized such as formic acid, alkanoic acids, aromatic acids, unsaturated aliphatic acids and hydroxy-substituted derivatives thereof. The acids may be the short chain acids containing one to nine carbon atoms but preferably are salts of the fatty acids containing 10 to 24 carbon atoms, whether saturated or unsaturated.

Coordination or chelate complexes may be formed with ligands such as acetylacetonate, bis-(ethyl aceto acetato), bis (1-phenyl-1, 3-butane dione), dimethyl dithiocarbamate, .beta.-naphthol sulfate and benzotriazole.

Exemplary sensitization-enhancing materials suitable for use in the practice of the present invention and especially with zinc oxide as the actinically active sensitive material are copper chloride, copper (II) acetylacetonate, bismuth trioxide, a mixture of cuprous chloride and the trimethylamine salt of tetracyanoquinomethane, cuprous chloride and copper (II) acetylacetonate, a mixture of copper formate and cuprous chloride, cupric sulfate, cupric chloride dihydrate, cupric bromide, cuprous sulfite, cupric thiocyanate, cuprous sulfide, cupric molybdate, cupric lactate, cupric formate, copper p-toluenesulfonate, cupric salicylate, cupric lineolate, cupric acetate, glycine cupric salt, cupric stearate, cupric oleate, cupric tartrate, cupric citrate, d,l-malic acid copper salt, cupric oxalate, bis-(ethyl acetoacetato) copper, bis-(1-phenyl 1, 3-butane-dione) copper, cupric dimethyl dithiocarbamate, cuprous sulphate-.beta.-naphthol, cuprous acetoacetonate, silver benzotriazole, silver nitrate, silver fluoride, silver oxide, and gallium (III) nitrate. The amount of sensitization-enhancing material incorporated in the film forming may be varied over wide ranges. Ratios of sensitization-enhancing agent to photosensitive material from 10.sup.-.sup.3 to 10.sup.-.sup.4 have given substantially equivalent results with no discernible differences.

The material which renders the photosensitive medium hydrophobic according to this invention is a water-proofing agent suitably a silicone, fluorocarbon or a higher molecular weight organic carboxylic acid.

A suitable hydrophobic silicone is an organosiloxane, typically a polydimethylsiloxane, which may be a liquid or solid polymer. An exemplary commercial available liquid material is G.E. "SR-82" silicone resin. Another form of hydrophobic silicone is a hydrophobic silicon dioxide aerosil obtained by reaction with a chlorosilane. The chlorine reacts with surface silanol groups to attach the silane to the silica particle. Typically, dimethyl chlorosilane attaches to silica to provide a carbon content of 0.8 to 0.9 percent per 100 m.sup.2 of product. An exemplary commercial product is (Degussa) "Aerosil R-972."

The water-repellent fluorocarbon material may be a liquid or solid polymer formed from tetrafluoroethylene, chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene fluoride or hexafluoropropylene. Fluorinated organic acid salts such as the copper salt of heptafluorobutyric acid, perfluorooctanoic acid, pentafluoro-propionic acid, p-fluorophenylacetic, 2-hydroxy-hexafluoro-isobutyric acid, trifluoroacetic, or 3-trifluoromethyl-3-hydroxybutyric acid, may also be utilized.

The organic acid may be a naphthenic acid. Commercial napthenic acid is a mixture of saturated cycloaliphatic acids, predominating in monocyclic, monocarboxylic acids containing a substantial percentage of materials having a carbon content from C.sub.6 to C.sub.8. The acids present in naphthenic acid typically have molecular weights in the range of 180 to 350. The organic acid may also be a saturated or unsaturated aliphatic acid having a carbon content from C.sub.10 to C.sub.24 preferably a fatty acid having a carbon content from C.sub.16 to C.sub.22 such as palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid.

The hydrophobicity agent is present in the range of 0.05 to 10 grams, preferably below 5 grams based on 100 grams of film forming solids. If the agent is utilized in the presence of another hydrophobicity agent such as the hydrated salts, fatty acid salts or water containing materials disclosed in copending application Ser. No. 883,086 filed Dec. 8, 1969, the normal amount of each material is reduced to a level to provide satisfactory but not excessive hydrophobicity.

The sensitive material, sensitization enhancing material are both usually in a finely comminuted form. The dry powder materials are mixed together with the hydrophobicity inducing material and with the desired binder and solvent, for example, toluene, suitably in an orbital ball mill, jar mill or vibratory mill until thorough dispersion of the ingredients is achieved. The mixture is then applied to a suitable substrate by conventional knife-coating equipment so as to form a film thereon having a wet thickness of 25-100 microns. For example, in general, the dry thickness of the film varies between 25 to 50 percent of the wet thickness. Upon drying the film is ready for use.

The selected hydrophilicity is utilized, in accordance with the invention, to provide aqueous developed images which are useful for selectively attracting water or water-bearing materials to the nucleated image or in the converse for rejecting hydrophobic materials from the aqueous developed areas. The aqueous developer may carry a solution or dispersion of dye or pigment so that when water is selectively adhered to the hydrophilic areas of the medium, the dye or pigment deposits thereon to form a visible image. When dry, the developed print is a positive reproduction of the original information design, indicia or the like. In the case of colloidal pigments suspended in water, the colloid is firmly attached to the surface in the hydrophilic exposed and developed areas so that it properly remains in place after the aqueous solution has evaporated. Of course, the hydrophobic areas repel the water so that there is no dye or pigment absorption or deposition.

Following the exposure and development in an aqueous media, tenaciously adsorbed water images are formed on the surface of the hydrophilic exposed areas. This water image will repel hydrophobic materials such as oil-based ink or molten wax. With the subsequent application of a hydrophobic lithographic ink, the ink will be repelled by the hydrophilic water developed image areas and will be retained by the hydrophobic background areas. A lithographic printing process results by transferring the ink image to a sheet of paper either directly or by means of an intermediate rubber blanket. The process of alternately water wetting and inking can be repeated to produce multiple prints on any conventional lithographic press.

If the hydrophobic compound is molten wax, on cooling and solidification of the wax, an in-depth wax image is formed which could be used as a gravure printing plate for an intaglio printing process, or alternatively, the wax image could be used as an etchant-resist for making a photoresist printed circuit board or the like.

In a variation of the development step in accordance with the invention, the photon activated nucleated surface is also selectively sensitive to the deposition of metallic vapor. When a metal is delivered to the surface in vapor form, the impinging vapor atoms will deposit selectively on the nucleation site because of the higher adsorption energy. On the unexposed areas, the reevaporation rate will nearly equal the incident rate and there will be no deposition while on the nucleation sites the reevaporation rate will be very low. The vaporous metal is preferably selected to have increased hydrophilicity and lyophobicity and is suitably zinc, cadmium or mercury. The vaporous metal coated media when wet with water exhibits increased resolution and better continuous-tone reproduction.

All of the aforementioned processes can be utilized with the water developed exposed hydrophilic image or with the metal vapor developed image. Vapor development in a vapor of a hydrophilic metal such as zinc, mercury or cadmium can contribute to resolution of the images.

In another variation of utilizing the hydrophilic properties of the exposed image, a photoresist may be directly produced by further developing the nucleated image with a material that forms a hard imagewise deposit. For example, potassium dichromate when applied to the nucleated image and "developed" by exposure to ultraviolet radiation, forms such a deposit. The hard and impermeable image will act as a resist when the material is dipped in a solvent that dissolves the binder for the sensitive layer thereby exposing the base material. The solvent etched assembly could be used directly as a printing plate or as a photoresist preliminary to chemical milling with an etchant suitable for the base material.

Referring now to FIG. 1, an aqueous developing imaging system employing the hydrophobic-hydrophilic media, according to the invention, is generally indicated as the device 10. The device 10 comprises a housing 12 which is preferably lighttight because of the photon-sensitive character of the medium employed therein. However, for purposes of illustration, the near side cover of the device 10 has been removed so that the interior can be seen. The housing 12 contains a first chamber 14 which functions as a storage chamber for the medium, and if desired, can include coating equipment for applying the medium to a substrate 28. The chamber 14 is connected to a second chamber 16 through light trap 18. Similarly, chamber 16 is connected to a chamber 19 through light trap 22. Then the medium leaves chamber 19 through a light trap 23 and enters a third chamber 20. The medium leaves the device 10 through a light trap 24.

Within chamber 14 a storage reel 26 furnishes a supply of substrate 28 which is lead under coater 30 containing a supply of media and around guide rolls 32 and 34 so that it can pass through light trap 18 into chamber 16. The coating is permitted to dry during passage around guide rolls 32 and 34 and if desired, a forced air dryer can be incorporated within chamber 14 facing the top surface of substrate 28, coated with the medium. Since the medium being applied to the substrate is photosensitive, the coating is carried out in chamber 14 which has a light level sufficiently low that exposure and activation of the media does not take place. It is again noted that the coating process need not be an integral part of the exposing and developing system. The substrate may be coated many months in advance of the actual use and a reel of coated presensitized media inserted into chamber 14 and wound onto the appropriate drive and guide rollers.

The coated and dried medium is now ready for exposure which occurs within the second chamber 10. In chamber 16 the medium is exposed by light source 36 which is powered by power supply 38. Light source 36 can be a suitable projector which projects an image upon the sensitive surface of the medium in which case the medium 38 is held stationary for an adequate length of time, during exposure. On the other hand, light source can be a suitable scanning light beam which scans transversely to the direction of motion of medium 38, in which case the advance of medium passed the transversely scanning light source can be at an appropriate rate to provide the necessary spacing longitudinally of the medium 38.

The light sensitivity of the media will depend on the composition thereof, but the coating given in Example 1 below, typically has an exposure range from unexposed to fully exposed over an exposure range of ultraviolet light from 10 ergs/cm..sup.2 to 1,000 ergs/cm..sup.2 . The medium is completely hydrophobic before exposure to the minimum value of light energy given above and is hydrophilic when subjected to the full exposure. At the intermediate levels of exposure, certain of the active sites are exposed and render particular areas at the sites hydrophilic so that the materials dissolved in water are carried by water to be deposited thereon. The intermediate range of exposure thus result in closely spaced hydrophobic and hydrophilic areas so that irregular or discontinuous images result.

After exposure, the medium 38 passes through light trap 22 into an optional third chamber 19. If desired, the exposed activated image areas of the media 38 can be coated with metal within this chamber, or, the metal coating may be accomplished simultaneously with exposure within chamber 16. As a result of the exposure to electrons, ions or photons, the surface of the media 38 is provided with a latent image comprising a number of nucleating sites in a pattern corresponding to the indicia to be reproduced. When metal vapor is applied to the surface of the exposed media, atoms or molecules from the vapor are selectively attracted to and retained by the nucleated areas comprising the latent image. Each atom in a nucleating site may capture as many as 10,000 atoms from the vapor. The necessary vapor is supplied from a source 25 usually associated with a controlled heater means 27. Generally the vaporous metal developer materials are metal, such as zinc, cadmium or mercury in bulk or powder form in a crucible or as a wire source. The metal vapor may also be supplied in the form of a reducible or thermally decomposible metal compound such as a metal carbonyl compound.

Metal vapor development takes place under the usual conditions governing the depositions of metal in vacuum. Thus, chamber 19 is placed under vacuum and the media 18 is spaced a distance from the vapor source 25 not more than the mean free path existing in the chamber at given conditions. Pressures in the ranges of 10.sup.-.sup.1 to 10.sup.-.sup.4 torr may be used for this purpose. Inert gases such as helium-argon may also be employed and introduced into the chamber to modify the velocity at which vapor molecules reach the surface, permitting a greater degree of control of image contrast.

After exposure and optionally after metal vapor development, the medium 38 passes through light trap 23 into aqueous development chamber 20 and from chamber 20 the medium 38 passes out of the device 10 through light trap 24. Within the chamber 20 the medium 38 passes around guide rolls 40, 42 and 44; during passage around guide roll 42 the medium is submerged within an aqueous bath 46 and the liquid is selectively deposited on the hydrophilic image areas. If the aqueous bath 46 carries dye or pigment, the coloring matter will be deposited on the hydrophilic image areas. The media 38 leaves chamber 20 with an aqueous developed image formed on the hydrophilic exposed areas, regardless of whether it has been developed with metallic vapor in chamber 19.

It should be understood that complete immersion in liquid is shown for purposes of illustration and that this is one of only many suitable methods for applying the developer. Other methods are easily as satisfactory and include surface application of the liquid from a revolving roller, spray application and other well-known means of solution application.

The aqueous developing time for this process is characteristically very short. The required time will vary as a function of the concentration of the hydrophobicity-inducing agent in the medium (being less for smaller concentrations thereof), as a function of the concentration of sensitization agent, being less for smaller concentrations thereof, as a function of ball milling time used to blend the ingredients (being less for longer ball-mill time), and as a function of developer temperature (being less for higher developer temperatures). Depending on the aforementioned variables, developing time may vary from 0.1 second up to 20 seconds. Typical developing times are from 0.5 to 5 seconds at 70.degree. F.

Following development, no further processing is required. However, to facilitate handling of the product, it may be desirable to use forced-air or radiant drying (or both) to dry the excess developer solution adhering on the surface of the medium.

As the medium comes out of light trap 24, it is ready for inspection and handling.

The following examples are intended to illustrate the preparation of the novel recording media of the invention, its exposure and development and not to restrict the scope thereof.

EXAMPLE I

A large number of coatings were made based on the same basic formula as follows:

Zinc Oxide (Photox 80l) 50-75 grams; Pliolite S-7 18 grams; Toluene 50-80 cc.; Methanol 4 cc.

Various sensitizers and hydrophobicity-inducing agents were then added to this basic formula and the ingredients combined in a 500 cc. gross-capacity aluminum oxide ball mill with 100 10 mm. diameter agate balls, and milled on a planetary ball mill for 45 minutes. The media was then coated to a wet thickness of 25 to 100 microns on a substrate of aluminized polyester film base or other suitable support. The resultant in coatings were tested for hydrophobicity. The addenda and results of the test coatings are given in Table I. (See next page).

It is seen from the Table that best results are achieved with linoleic acid present in an amount of 1 to 2 grams or with the silane treated silica material. The media according to the examples can be exposed with approximately 300 ergs/cm..sup.2 of 3625 A., ultraviolet radiation. Development can then consist of a one second surface application of a water suspension of colloidal graphite or suitable dyes. A graphite developer can be prepared by dispersing 83 grams of Acheson Colloids "Aquadag --------------------------------------------------------------------------- TABLE I

Tape Sensitization Agent Hydrophobicity Resulting Composition Agent(s) __________________________________________________________________________ 1a Copper Stearic Acid Fair acetylacetonate (0.25g.) (0.10g.) 1b Copper Stearic Acid Fair acetylacetonate (0.50 g.) (0.1 g.) 2a Copper Napthenic Acid Poor acetylacetonate (0.5 g.) (0.1 g.) 2b Copper Napthenic Acid Poor acetylacetonate (1.0 g.) (0.10 g.) 3a Copper Linoleic Acid Fair acetylacetonate (0.25 g.) (0.10 g.) 3b Copper Linoleic Acid Fair acetylacetonate (0.50 g.) (0.10 g.) 3c Copper Linoleic Acid Good acetylacetonate (1.0 (0.10 g.) 3d Copper Linoleic Acid Good acetylacetonate (2.0 g.) (0.10 g.) 4 Cuprous Chloride Aerosil R-972 Good (0.10 g.) (0.30 g.) 5 Cuprous Chloride Formalin (8 ml. Good (0.10 g.) and Aerosil R-972 (0.3 g.) 6 Cuprous Chloride G.E. SR-82 Fair (0.10 g.) Silicone Resin (1.0 g.) __________________________________________________________________________

(22 percent solids in water)" in 1 liter of deionized water. The alkalinity of the developer can be adjusted with ammonia or acetic acid to produce a pH between 8 and 11. The higher pH produces more rapid but less selective development.

The exposed sheet can also be developed by immersion for 1-20 seconds in tap water or preferably in a lithographic fountain solution. Referring now to FIG. 2, a length 60 of the medium 28 developed, in accordance with FIG. 1, is removed and cut to printing plate size. The plate 60 is applied to a printing roller 62. Tank 64 contains fountain solution 66 such as Addressograph-Multigraph (AM) Multilith "Repelex" fountain solution (concentrate diluted 1:30 with deionized water). Tank 68 contains an oil-based printing ink 70 such as Von Son Holland "Quickset Printing Ink" or AM "MLS Series Multilith Ink." Rollers 72 and 74 apply the respective fountain solution 66 and ink 70 to the surface of the printing plate 60.

A source of paper 75 from roll 76 passes around guide roll 78 and is pressed against the surface of the printing plate 60 by means of press roll 80 and then passes by guide roll 82 before being rewound on takeup roller 84. On each revolution of the printing roller 62 the fountain solution 66 will selectively adhere to the exposed hydrophilic areas of the plate 60 and therefore the subsequently applied ink 70 will be rejected by these areas to provide a clear and sharp background for the finished prints. The ink accepted by the nonexposed areas is transferred to the paper 75 passed in contact with the printing plate 60.

Multilith prints made from a hydrophilic-hydrophobic medium, according to the invention, exhibit greatly improved contrast and lack of ink pickup in the background areas. A press run is capable of producing several hundred clear legible copies with good resolving power. Furthermore, the Multilith-produced prints do not show the characteristic fill-in of circular shapes such as the center of the letter "o" and "e" which is typical of aqueous development by dipping. This is attributable to the printing press breaking the bubbles by pressure of the rollers.

In the case of media subjected to vacuum-development with metal vapor such as zinc in chamber 19 of FIG. 1, the copies produced are somewhat sharper and exhibit a degree of direct halftone reproduction without the use of halftone screens.

A further process utilizing the aqueous developed media, prepared in FIG. 1 is illustrated in FIG. 3. In this process a hardenable oleophilic compound is applied to the aqueous developed exposed medium. The oleophilic material hardens to form an impermeable image having a relief image corresponding to the exposed portions of the medium. Referring now to the drawings, the exposed medium 28 enters chamber 20 whereas it passes around guide roll 42; it is aqueous developed within the water bath 46.

The developed media 28 then passes through light trap 24 into lighttight chamber 90. The media passes around guide rolls 91, 92 and 94 within chamber 90. As the medium passes around roll 92, it is submerged within a liquid oleophilic compound such as hot wax 96. The wax is repelled by the olephobic water-adsorbed exposed image areas, but it builds up upon the unexposed portions of the sensitive medium on web 28. The hard wax is cooled by any convenient means such as by cooling immersion roller 92 so that a solid wax image is built up upon the unexposed areas. The medium leaves chamber 90 through a trap 98.

The medium having the built up image prepared in accordance with the last figure can be utilized as a gravure printing plate to produce copies. A water-base ink when applied to such a plate will adhere to the relieved hydrophilic areas, but will be repelled by the built-up wax areas. Furthermore, since the image areas are depressed, the ink can be wiped off the raised nonimage areas. After wipeoff the ink can be transferred by pressing the plate against a transfer sheet such as paper. The gravure printing plate can be repeatedly reinked with gravure ink and printed against paper. In such a case a portion of the web corresponding to the pattern to be printed in multiple copies is severed from the web and inserted in a press as a printing plate for producing multiple copies.

It should be noted that the wax image can be used as an etchant resist. In such a case the substrate should be an etchable material such as a film of metal or a film of metal laminated to an inert support, suitably a polyester such as "Mylar." The etchant can be any suitable solvent for the etchable substrate which does not attack the layer and may be an acid or alkali material oxidizing agent or reducing agent. The etching process may again be operated on the severed sheets of media in a batch type of operation rather than the continuous operations that have been illustrated.

A process which yields a photoresist directly from the photon exposed media of FIG. 1 without the need for forming a relief image is illustrated in FIG. 4. The photon exposed media 28 passes through light trap 23 into lighttight chamber 20. The aqueous media 46, in this case, contains a compound that forms a hard impermeable deposit upon the hydrophilic exposed areas. An aqueous solution of potassium dichromate is suitable for this use. The dichromate-treated media leaves chamber 20 through light trap 24 and enters chamber 102.

Within chamber 102 the treated media is exposed overall to ultraviolet radiation from a high intensity ultraviolet lamp 103 which acts to cross-link, polymerize or otherwise harden the dichromate coated, exposed areas. The treated media leaves the chamber 102 through light trap 104 and enters chamber 106. Within chamber 106 the media passes around guide rolls 108, 110 and 112. The roll 110 is at least partially immersed within a bath 114 which contains a solvent for the media. The solvent dissolves the film-forming binder of the photosensitive coated film 28 so that the web beneath the unexposed areas is removed to expose the underlying portions of the web substrate. A suitable solvent for the film forming binder is toluene.

As the web 28 leaves chamber 106 through light trap 115, the originally photon unexposed areas of the web are unprotected while the photon exposed areas are protected both by a layer of the sensitive material and a layer of the hard impermeable deposited material. The web 28 may then be delivered to a tank 116 containing a bath of etchant 118. The web passes over rollers 120, 122 and 124. Roller 122 is again partially submerged within the bath 118 and as the web passes over this roller the etchant removes material from the unprotected areas of the tape corresponding to the photon unexposed areas. This process can be used for preparing printing plates or in processes of chemical milling. Again the process may be carried out in a step-by-step batch basis on separate sheets of material prepared on rigid substrates.

This invention having been described in its preferred embodiments, it is clear that it is susceptible to numerous modifications and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claims.

Claims

What is claimed is:

1. A hydrophilic-hydrophobic, photon-sensitive medium comprising:

a film-forming binder in which is substantially uniformly dispersed:

a photon-sensitive material selected from the group consisting of oxides of zinc, titanium, tantalum, indium, magnesium, germanium, tin and bismuth, sulfides and selenides of calcium, zinc, cadmium, iron and indium, boron nitride, calcium tungstate, beryllium aluminide, lithium carbonate, zinc carbonate, cadmium niobate, lithium niobate, anthracene and cesium-activated calcium-magnesium silicate and mixtures thereof;

a sensitization enhancing material selected from the group consisting of copper chloride, copper (II) acetylacetonate, bismuth trioxide, a mixture of cuprous chloride and the trimethylamine salt of tetracyanoquino-methane, cuprous chloride and copper (II) acetylacetonate, a mixture of copper formate and cuprous chloride, cupric sulfate, cupric chloride dihydrate, cupric bromide, cuprous sulfite, cupric thiocyanate, cuprous sulfide, cupric molybdate, cupric lactate, cupric formate, copper p-toluene sulfonate, cupric salicylate, cupric lineolate, cupric acetate, glycine cupric salt, cupric stearate, cupric oleate, cupric tartrate, cupric citrate, d,l-malic acid copper salt, cupric oxalate, bis-(ethyl acetoacetato) copper, bis-(1-phenyl 1, 3-butane-dione) copper, cupric dimethyl dithiocarbamate, cuprous sulfate-.beta.-napthol, cuprous acetoacetonate, silver benzotriazole, silver nitrate, silver fluoride, silver oxide, and gallium (III) nitrate; and

a hydrophobicity-inducing agent selected from the group consisting of a liquid or solid polymer formed from tetrafluoroethylene, chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene fluoride or hexafluoropropylene; fluorinated organic acid salts including the copper salts of heptafluorobutyric acid, perfluorooctanoic acid, pentafluoropropionic acid, p-fluorophenylacetic, 2-hydroxy-hexafluoroisobutyric acid, trifluoroacetic, or 3-trifluoromethyl-3-hydroxybutyric acid; a saturated or unsaturated aliphatic acid having a carbon content from C.sub.10 to C.sub.24, a fatty acid having a carbon content from C.sub.16 to C.sub.22 including palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid, napthenic acid; polydimethyl siloxane, silane modified silica, copper salt of fluorinated alkanoic acid; a polymer of tetrafluoroethylene, chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene fluoride or hexafluoropropylene.

2. The medium according to claim 1 in which the hydrophobicity agent is selected from the group consisting of napthenic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, polydimethyl siloxane, a silane modified silica, copper salt of fluorinated alhanoic acid and a polymer of tetrafluorethylene, chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene fluoride or hexafluoropropylene.

3. The process of preparing an image corresponding to a photon exposure comprising the steps of:

photon-exposing a selective area of the photon-sensitive, hydrophobic medium of claim 1 to render the medium hydrophilic in the exposed areas; and

treating the sensitive medium with a material to produce a physical representation of the photon-exposed area.

4. The process of preparing an image corresponding to a photon exposure comprising the steps of:

photon-exposing a selective area of a photon-sensitive, hydrophobic medium to render the medium hydrophilic in the exposed areas, the sensitive medium comprising a substantially uniform solid dispersion in an organic film-forming binder of a photon-sensitive material, a sensitization-enhancing material and a hydrophobicity-inducing agent selected from the group consisting of a liquid or solid polymer formed from tetrafluoroethylene, chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene fluoride or hexafluoropropylene; fluorinated organic acid salts including the copper salts of heptafluorobutyric acid, perfluorooctanoic acid, pentafluoropropionic acid, p-fluorphenylacetic, 2-hydroxy-hexafluoroisobutyric acid, trifluoroacetic, or 3-trifluoromethyl-3-hydroxybutyric acid; a saturated or unsaturated aliphatic acid having a carbon content from C.sub.10 to C.sub.24, a fatty acid having a carbon content from C.sub.16 to C.sub.22 including palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid, napthenic acid; polydimethyl siloxane, silane modified silica, copper salt of fluorinated alkanoic acid; a polymer of tetrafluoroethylene, chlorotrifluoroethylene, fluorinated ethylene-propylene, vinylidene fluoride or hexafluoropropylene; and

treating the sensitive medium with a source of vaporous metal to the photon exposed medium and depositing said metal selectively on aid exposed hydrophilic area.

5. The process of preparing an image in accordance with claim 4 wherein the sensitization-enhancing material is selected from the group consisting of copper chloride, copper (II) acetylacetonate, bismuth trioxide, a mixture of cuprous chloride and the trimethylamine salt of tetracyanoquinomethane, cuprous chloride and copper (II) acetylacetonate, a mixture of copper formate and cuprous chloride, cupric sulfate, cupric chloride dihydrate, cupric bromide, cuprous sulfite, cupric thiocyanate, cuprous sulfide, cupric molybdate, cupric lactate, cupric formate, copper p-toluene sulfonate, cupric salicylate, cupric lineolate, cupric acetate, glycine cupric salt, cupric stearate, cupric oleate, cupric tartrate, cupric citrate, d,l-malic acid copper salt, cupric oxalate, bis-(ethyl acetoacetato) copper, bis-(1phenyl 1, 3-butane-dione) copper, cupric dimethyl dithiocarbamate, cuprous sulphate-.beta.-naphthol, cuprous acetoacetonate, silver benzotriazole, silver nitrate, silver fluoride, silver oxide, and gallium (III) nitrate.

6. The process of preparing an image in accordance with claim 3 wherein the preparing step includes coating the sensitive material on an etchable metal; and

the treating step comprises treating the sensitive material with an aqueous metal etchant.

7. The process of preparing an image in accordance with claim 6 wherein the treating step of treating the sensitive material with an aqueous metal etchant is followed by a solvent step wherein the etched metal is treated with a solvent which dissolves the sensitive medium from the metal backing.

8. The process of preparing an image in accordance with claim 3 wherein the treating of the sensitive material to form a water film on the hydrophilic, exposed areas is followed by the steps of:

treating the sensitive medium with an oil base ink so that the oil base ink is positioned on the hydrophobic areas of the sensitive medium and is rejected by the adsorbed water covered exposed hydrophilic areas of the sensitive medium; and

imprinting the ink upon a base by pressing the sensitive medium having oil base ink on the hydrophobic areas thereof against the base.

9. The process of preparing an image in accordance with claim 3 wherein the treating step comprises:

placing ink upon the sensitive medium in accordance with the pattern determined by the hydrophilic and hydrophobic areas of the sensitive medium.

10. The process of preparing an image in accordance with claim 9 wherein the selective placement of ink comprises the steps of:

forming a water film on the hydrophilic areas of the sensitive medium;

forming a built-up wax layer on the hydrophobic areas of the sensitive medium;

filling the hydrophilic areas between the built-up wax with gravure ink; and

printing a base by pressing the medium against the base to be printed.