US3736142A - Nucleation-recording medium comprising a photoconductor,a nucleation-enhancing metal salt,and a phthalocyanine dye former - Google Patents

Abstract

THE FILM-FORMING BINDER TO PROMOTE IMAGEWISE FORMATION OF OPTICALLY DENSE MACROCYCLIC COMPOUNDS THEREON.
IMAGE RECORDING MEDIA SENSITIVE TO ELECTRON AND/OR PHOTON EXPOSURE, AND DEVELOPABLE BY METAL DEPOSIT FROM A VAPOR, CONTAINS PHOTON OR ELECTRON SENSITIVE MATERIAL, NUCLEATION-INDUCING COMPOUND AND IMAGE DENSITY-EN HANCING AND STABILIZING ADDITIONS SUCH AS PHTHALONITRILE IN A FILM-FORMING BINDER, WHICH CAN ACT AS A CATALYST IN

D R A W I N G

Description

May 29, 1973 KASPAUL kT AL 3,736,142

' NUCLI'IA!ION-JH'IUOMHNU MEDIUM COMPRISING A IHU'IUGUNUUC'IOR, A

NUULEAIION-ENHANCING METAL SAM, AND

A PHTHALOCYANINE DYE FORMER Filed Nov. 5, 1971 3 Sheets-Sheet 1 Developed lmoge medium Fig.1.

May 29, 1973 NUCLEATION-RECORD A. F. KASPAUL ETAL 3,736,142 ING MEDLUM COMPRISING A PHOTOCONDUCTOR, A

s-She Filed Nov. 5, 1971 AND A y 1973 A. F. KASPAUL ETAL NUCLEATION'RECORDING MEDlUM COMPRISING A PHOTOCONDUCTOR,

NUCLEATION-ENHANCING METAL SALT,

A PHTHALOCYANINE DYE FORMER 3 Sheets-Sheet l Filed Nov.

u w H I w 20 D I m s e E m C m M Q E X E e r U S 0 m 0. m& u u w u MU m 2 0 8 6 w. 2 0

Fig. 5.

United States Patent 3,736,142 NUCLEATION-RECORDING MEDIUM COMPRIS- ING A PHOTOCONDUCTOR, A NUCLEATION- ENHANCING METAL SALT, AND A PHTHALO- CYANINE DYE FORMER Alfred E. Kaspaul and Erika E. Kaspaul, Malibu, Calif., assignors t0 Hughes Aircraft Company, Culver City,

Calif.

Filed Nov. 5, 1971, Ser. No. 196,170 Int. Cl. G03c 1/52 US. Cl. 9690 R 1 Claim ABSTRACT OF THE DISCLOSURE Image recording media sensitive to electron and/or photon exposure, and developable by metal deposit from a vapor, contains photon or electron sensitive material, nucleation-inducing compound and image density-em hancing and stabilizing additions such as phthalonitrile in a film-forming binder, which can act as a catalyst in the film-forming binder to promote imagewise formation of optically dense macrocyclic compounds thereon.

The invention herein described was made in the course of or under a contract or subcontract thereunder with the Department of Defense.

BACKGROUND Field of the invention This invention is directed to an image recording medium, and particularly a medium developable by deposition of metal from a vapor.

The prior art The selective deposition of materials, particularly metals, upon a preconditioned or what may be referred to as a prenucleated recording medium, is known. Such selective deposition processes have employed various means for providing a prenucleated image which is invisible and latent. Thus, such prenucleated images have been formed by scanning a surface of a substrate with an electron or ion beam or by exposing the surface to a light image of the desired pattern.

In US. Pat. No. 3,140,143, issued to the instant inventors, the formation of such prenucleated images is achieved by depositing at least trace amounts of an aqueous liquid on preselected portions of the surface of a substantially inert, anhydrous solid substrate which has an inorganic metal compound as a part of its surface. Such a surface is typically provided according to this patent by means of a thin film consisting of zinc oxide incorporated into a resinous binder, such as a copolymer of butadiene and styrene. The latent image on such a substrate surface is formed by depositing water, for example, in the pattern desired upon such surface. The image is then developed by exposing this surface to vapors of a metal in a vacuum chamber, the metal atoms being selectively deposited upon and in accordance with the aqueous liquid pattern.

Similarly, in US. Pat. No. 3,235,398, the instant inventors have disclosed recording media and processes for recording thermal or infrared information wherein substrates, such as mica, baryta paper, and polyethylene terephthalate films are coated with finely divided zinc oxide in an organic binder. On the surface of this coating, a material such as nickel, silver, copper, cuprous chloride, bismuth or bismuth oxide is in vacuo deposited. Such deposited materials, according to this patent, serve to presensitize the surface of the recording medium by forming nucleation sites which aid in the selective deposition of a metal from a vapor during development of an infrared image focused on the surface of the recording medium.

3,736,142 Patented May 29, 1973 p CC In this system, it is necessary to simultaneously or substantially immediately expose the recording medium to the development vapor with exposure to the infrared image, since the infrared image appears to have no lasting effect upon the recording medium.

As noted previously, another procedure for obtaining the requisite pattern of prenucleated areas is by scanning or otherwise exposing the surface of a substrate with electrons, ions or photons and, thereafter, developing the latent image thus formed by exposing the surface to metallic vapor so that the metal atoms are selectively deposited and grow upon and in accordance with the prenucleated pattern. Such a process is described by the present inventors as applicable for fabricating microcircuits in a paper, entitled Application of Molecular Amplification to Microcircuitry, published in the 1963 Transactions, Tenth National Vacuum Symposium, American Vacuum Society. The process described therein, as well as the phenomena involved in the present invention, are called molecular amplification because the nucleated sites selectively capture thousands of atoms or molecules of the depositing of condensing material. The term molecular amplification describes the collection eflectiveness of each nucleation center which captures a much larger number of atoms or molecules from the surrounding vapor than they contain themselves.

Thus, invisible nucleation centers, of the present medium, established by actinic ray exposure or other means (e.g., electrons, ions, molecules or photons), containing about 10 atoms per cm. (which corresponds to about 0.01 monolayer), become visible by collecting a total of about 10 atoms per cm. This means that each atom in a nucleation center has captured at least 10,000 atoms from the incident vapor (or molecular beam, which phrase is customarily used to describe material vapor directed toward the substrate surface as a vapor stream or beam).

The next step in enhancing sensitivity comprised the deposition of a surface layer of a suitable sensitive material. This very thin layer is produced either by predeposition of an electron or photon sensitive compound, such as described previously, or by having a gaseous compound in contact with the substrate at all times, such as described in US. Pat. No. 3,378,401. Because of the very small cross-section of thin surface layers interacting with-photons or electrons, a large portion of the incident radiation is lost into the subsurface.

Next, in order to enhance the sensitivity, a nucleationinducing compound or sensitization-enhancing material was mixed with the photon or electron sensitive material. This is taught in patent application Ser. No. 839,271, filed July 7, 1969. It is assumed that this results in an efiicient energy transfer upon exposure from the irradiated zinc oxide to a nucleation-inducing compound which is intimately dispersed with the zinc oxide in a suitable binder. It is further assumed that this transfer results in the generation and subsequent migration of metal ions to the surface nucleation sites Where neutralization by trapped electrons produces a stable nucleation cluster. The contribution by the volume or bulk of the recording medium to the overall gain of the deposition process is achieved by incorporating a nucleation-inducing agent in a film-forming binder in which is dispersed a material sensitive to electrons, ions or photons. The result is a net gain of two to three orders of magnitude, as compared to films of the prior art depending solely upon surface phenomena.

The maximum reflective optical densities for normally developed bulk-sensitized or surface-sensitized nucleation recording media seldom exceeded unity. However, electron beam-exposed samples of the bulk effect nucleation recording media with the sensitization-enhancing material uniformly mixed therein exhibited, upon development with zinc metal vapor, transmission densities of d=l.00 to 1.20. This was measured by scanning the developed images of the recording medium with an electron beam. Because the medium is largely composed of zinc oxide, light is generated directly below the image plane, and the photon flux is modulated by the corresponding optical density of the image. A photo detector measures the amount of light attenuation in each spot, and this results in corresponding values for the transmission densities.

It was thought that a transmission density of greater than unity should result in nearly twice this value for reflected light, because the ambient light is attenuated upon entering the images, as Well as upon leaving being reflected by the zinc oxide beneath the image plane. Unfortunately, this is not readily achieved due to the inherently high specular reflection of thin metallic films.

One of the causes of the observed low reflective densities is the quite perfect crystalline structure of the metal films. Therefore, control of the selective deposition of metal vapor atoms in a manner to form a more amorphous or filamentary structure would permit the image to exhibit enhanced light-absorbing capabilities. The amorphically-deposited metal vapor will appear black, as contrasted with the grey-appearing crystalline deposits resulting in enhanced image contrast.

Control of the thermal energy of the metal vapor atoms by various means can result in more amorphous images resulting in low specular reflectance. Moderation may be achieved by the use of low temperature and/ or large area vapor sources, or by moderating the energy of the metal atoms by means of adjacent walls where they can give up energy without condensation, or by appropriate multiple collisions with reactive or non-reactive gases within the development chamber. This is taught by our prior invention Ser. No. 71,043, filed Sept. 10, 1970.

However, this invention is directed to enhancing the optical density by employment of a chemical-active, density-enhancing agent in the medium.

SUMMARY In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to image recording media of the nature exposed by actinic radiation, such as electron or photon exposure and developed by deposition of metal from the vapor, and comprising a photon and/or electron sensitive material, a nucleation-enhancing material, and a macrocyclic compound-forming material as an image density-enhancing material mixed together in a film-forming binder.

Accordingly, it is an object of this invention to provide a medium which has an enhanced reflective optical density and stability, which medium is developed by the initial deposition of image metal from a vapor followed by chemical reaction of image-forming atoms with macrocyclic compound-forming materials.

It is a further object of this invention to provide a medium which has enhanced reflective optical density and image stability, which medium is developed by the initial deposition of image metal from a vapor followed by chemical reaction of image-forming atoms with vaporized organic molecules produced by separate source.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing of the exposure and development of media made in accordance with this invention.

FIG. 2 is a showing of a developed medium.

FIG. 3 is a schematic side-elevational view, with parts broken away, of another embodiment of an exposure and development apparatus for the medium of this invention.

FIG. 4 is an isometric view of an exposure and development (levies fer the medium Q h inv ntion.

FIG. 5 is a curve illustrating the diiferences in image density between two media, one of which is prepared in accordance with this invention.

DESCRIPTION It should be understood that broadly the present invention relates to the formation of an image on a recording medium, which image is initially not necessarily visible, but may be rendered visible and read electronically. Such images are, therefore, hereinafter referred to as latent. Furthermore, the term image, as used herein, is intended to mean the entire area of the surface of the recording medium or any portion less than the whole thereof, including patterns which visually impart information (such as words or pictures) or which patterns perform some esthetic or utilitarian function (such as a decorative design or electrically-conductive paths for so-called printed circuitry).

More particularly, the invention relates to the formation of image areas for the process of exposing a recording medium to electrons, ions or photons whereby the exposed areas of the medium appear to function as what may be called nucleation sites on which one or more materials may be selectively deposited from the vapor phase thereof and thus rendered visible or otherwise useful. The exposure process is referred to hereinafter as selective nucleation, by which is meant the establishment of such nucleation sites in or on the recording medium, which nucleation sites are capable of condensing vast numbers of atoms or molecules or other particle from a vapor of a suitable material to which the recording medium is exposed. This nucleation is selectively established in response to impingement of the recording medium by electrons, ions or photons. The invention relates especially to new and exceptionally eflicient recording medium materials capable of forming such nucleation sites in response to exposure by light or by a bombarding and scanning electron or ion beam.

These nucleation sites are developed (rendered visible or otherwise useful) by the vapor deposition of metal, and the particular medium of this invention is directed to a medium which has an enhanced visible optical contrast ratio between the non-image areas where metal is not deposited and the image areas where the development metal is deposited. The use of the medium of the present invention involves two principal steps, the first of which is exposure of a nucleatable recording medium to electrons, ions, or photons, which may be in the form of a scanning beam or a mask-formed pattern thereof whereby a latent image is established on or in the medium corre sponding to that formed by the beam or pattern of such energy. The latent image is apparently constituted by nucleating sites selectively established in accordance with the areas of the recording medium impacted by the electrons, ions or photons. These latent images are termed nucleating sites herein because of their apparent ability to enhance and promote the growth thereat of atoms or molecules of the vapor developer material, while other unexposed areas of the recording medium do not appear to permit such deposition or growth to any appreciable extent.

The second step in the process is the development of the latent image comprising these nucleating sites so as to render this image visible or otherwise useful, which step is accomplished by exposing the surface of the recording medium to a developer material in the vapor phase thereof. This material deposits and grows (nucleates) on and from the latent image nucleating sites to form a visible image or pattern which is bonded to the recording medium thereby remaining permanently in place.

Some media may become mounted in such a manner th t it s se fpp g o e e other med a y equire a supporting structure for physical support or to provide electrical conductivity.

Suitable support substrates for use in the latter of these embodiments may be formed of almost any material and may partake of almost any geometry. Thus, paper, especially in the form of tape, may serve as a suitable support substrate and is particularly desirable for recording information and the like. Glass may also be used, as well as various types of transparent plastics, such as acetate films and the like (i.e., methyl methacrylate, cellulose acetate, polycarbonates). Furthermore, there may be a conductive top surface, such as a thin metal film, on the supporting substrate for electrical conductivity purposes whereby two films may be made optically transparent, or the entire support may be metal, such as a metal plate or tape.

Mixed together in a film-forming binder are a sensitive material, a nucleation-enhancing or nucleation-inducing material, an image density-enhancing material and/or a catalyst to promote the formation of macrocyclic compounds dispersed together in a film-forming resin or binder. The image density-enhancing material may be incorporated into the medium or supplied by a separate source.

The process of development, termed selective condensation" herein, is best understood from the following explanation. Upon exposure of a given surface, such as glass, or plastic, to an incident flux of atoms and/ or molecules from a molecular oven or other vapor source, atoms and/ or molecules will condense upon the surface, at first moving about it random fashion. At low incident rates, a certain number of atoms will be present on the surface at any given time and the equilibrium concentration is reached as soon as the evaporation rate equals the incident flux.

Molecular amplification results from manipulation of surface free energies leading in turn to the selective acquisition of a large number of atoms by effective nucleation sites. The amplification or gain may then be defined as the total number of atoms so captured divided by the number of atoms in these nucleation centers. To illustrate this phenomenon more clearly, when a surface such as a glass slide is exposed to an incident flux of atoms from a molecular oven, atoms of given thermal energy arrive at the surface, move about it in random fashion, and eventually re-evaporate after a given time interval has passed. For low incident rates, a certain fixed number of atoms will always be found upon the surface and the atom population rises and falls with the incident flux. However, once a critical incident rate or critical surface concentration is exceeded, auto-nucleation commences. This is due to the greater collision frequency experienced by atoms moving about the host surface, resulting in rapid formation of stable nucleation centers. Thus, a drastic reduction of the number of re-evaporating atoms ensues and nearly every incident atom must be captured from there on.

Generally, this is the chosen method for the nonselective deposition of in vacuo deposited thin films, and most commercial processes are largely based upon the formation of auto-nucleation centers. As long as the incident flux is kept low, no single atoms will remain on the host surface once the influx of atoms is halted. However, with a steady increase in incident rates, one must expect to find more and more a tendency of forming random centers (twins, triplets, and stable clusters) which are in direct competition with the image-forming sites. Above the critical incident rate, all incoming atoms must be captured as soon as auto-nucleation commences. Hence, for the selective deposition. of atoms without any background, one has to stay clear of auto-nucleation at all times and the critical incident flux cannot be exceeded even for a very short moment.

Under carefully controlled conditions, rates as high as atoms/cm. -sec. may be utilized, and imagewise, selective deposition can be accomplished to the extent of many thousand or even ten thousand atom layers per second. Hence, even a thick deposit is produced in less than one second. Because the required film thickness for image and data storage applications is much less, no more than several hundred atom layers, a picture may be fully developed in 10 to 50 milliseconds without unduly bringing up the background.

Because of its quantitative predominance, which usually determines the color of the recording media, the material which is sensitive to electrons, ions or photons is sometimes referred to as a pigment. The term sensitive material will be used in this specification as a convenient expression to mean a material which is sensitive to impingement of electrons, ions or photons. The sensitive material, the nucleation-inducing agent, and the image density-enhancing material are mixed together with an appropriate binder and solvent therefor in an orbital ball mill, for example, after which the mixture is coated upon a desired substrate or formed into a self-supporting film.

A satisfactory hinder or matrix for the materials of the invention may be any of many well-known film-forming resins and particularly those of the butadiene and/or styrene type. A typical binder of the styrene-butadiene type which has been used successfully in the practice of the present invention is one identified as Pliolite by the manufacturer thereof, Goodyear Tire and Rubber Co., Chemical Division, Akron, Ohio. Other satisfactory matrix materials are polystyrene, chlorinated rubber, polyvinylidene chloride, polyvinyl butyral and the like. Any suitable solvent for thinning the film-forming resin or otherwise adjusting its miscibility and spreadability may be employed and a typically satisfactory solvent is toluene. It will be understood that neither the binder nor the solvent therefor are of critical importance, since the primary purpose is to permit the sensitive material and the nucleationinducing agent materials to be thoroughly mixed and then, while still flowable, to be supplied to a suitable substrate on which the binder may harden and form a relatively tough film in which the sensitive material and the nucleation-inducing materials are uniformly dispersed. Thus, the binder and the solvent function primarily in a physical manner to provide a support carrier or matrix for the sensitive material and the nucleation-enhancing materials.

The photon or electron sensitive materials suitable for use in the practice of the present invention appear to include materials which are classifiable as either photo-conductive or photo-emissive or both. As noted hereinbefore, they function for the purposes of the present invention in response to either photons, electrons or ions. In general, the preferred sensitive materials for use in recording media according to the invention include compounds formed by elements of Group II of the Periodic Chart of the Elements (hereinafter referred to as Group II elements) with elements of Group VI thereof (hereinafter referred to as Group VI elements). However, the sensitive materials for use in the recording media of the invention include compounds such as oxides of titanium, tantalum, indium, magnesium, germanium, zinc, iron, tin and bismuth, sulfides of calcium, zinc, cadmium and indium, and boron nitride, calcium tungstate, beryllium aluminide, lithium carbonate, zinc carbonate, cadmium niobate, lithium niobate, calcium magnesium silicate (cesium-activated) and mixtures thereof.

The nucleation-inducing material or sensitization-enhancing material suitable for use in the practice of the present invention are, especially with zinc oxide, any of the metallic or metallo-organic compounds and metallic halides, and particularly copper halide, copper (II) acetylacetonate, nickel (II) acetylacetonate, zinc (II) acetylacetonate, chromium (III) acetylacetonate, bismuth trioxide (Bi O cuprous chloride, a mixture of cuprous chloride and triethylamine salt of tetra cyanoquinomethane, a mixture of cuprous chloride and copper (II) acetylacetonate, a mixture of copper formate and cuprous chloride, cupric sulfate, cupric chloride hydrated with 2 water molecules, cuprous bromide, cuprous iodide, cupric bromide, cuprous sulfite, cupric thiocyanate, cuprous sulfide, cupric molybdate, cupric lactate, cupric formate, copper p-toluene sulfinite, cupric salicylate, cupric linoleate, cupric acetate, glycine cupric salt, cupric stearate, cupric oleate, cupric tartrate, cupric citrate, dextro-levo malic acid copper salt, cupric oxalate, bis (ethyl acetoacetate) copper, bis (l-phenyl 1,3-butane-dione) copper, cupric dimethyl dithiocarbamate, cuprous sulfate B naphthol, cupric acetylacetonate, silver benzotriazole, tin chloride, nickel chloride, chromium chloride, nickel sulfate, nickel fluoride, silver nitrate, and silver oxide.

The image density-enhancing and stabilizing materials are phthalonitrile, phthalimide, the orthodinitriles of henzene, naphthalene and anthracene; the substituted phthalonitriles, such as ortho cyanobenzonitrile tetrachlorophthalonitrile and 4 phenyl phthalonitrile, groups especially forming pthalocyanines such as monoiminophthalimide, 1,3-diiminois-oindoline, dimethylfumaric dinitrile, naphthalene-2,3-dinitrile, dimethyl malic dinitrile tetrahydrophthalonitrile, citraconic dinitrile.

Essentially the phthalocyanine pigments may be considered as formed by the condensation of four molecules of phthalonitrile forming a large ring of alternate carbon and nitrogen atoms containing eight of each. As phthalonitrile contains only two reactive groups and these are all exhausted in forming the great tetraazaporphine ring, monomeric substances have been produced, that is to say, each molecule of the pigment contained only a single tetraazaporphine ring.

The sensitive material, the nucleation-inducing material are incomminuted form and are mixed together with the macrocyclic compound-forming material with the desired binder and solvent in a suitable mill until thorough dispersion of the dry ingredients is achieved.

The normal solvent for Pliolite 8-7, which is the filmforming binder principally used in the examples hereinafter, is toluene. Sufficient toluene is added to provide proper fluidity. The toluene thus serves as the principal or primary solvent, providing the necessary fluidity for proper mixing. It was unexpectedly discovered that the employment of a second solvent of proper nature improved the photon or electron sensitivity. For example, when methanol is employed as a second solvent in the amount of 4-8 milliliters per one-hundred grams of sensitive material, the nucleation-inducing material is apparently better dispersed in or coated on the sensitive material to provide for greater sensitivity. The greater sensitivity provides a fully created latent image with the impingement of a lesser amount of exposure. The second solvent is a liquid alcohol having a chain length from 1 to 8, and is preferably methanol. The semi-fluid or viscous mixture is then applied to a suitable substrate by conventional knife-coating equipment so as to form a film ih9ll ha g a wet thic ness of about 100 mic cns,

for example. In general, the dry thickness of the film varies between 25 percent to 50 percent of the wet thickness of the film. Upon drying, the film is ready for use.

The media is thus prepared by dispersing together the appropriate ingredients and coating the mixture upon a suitable substrate. The dispersing step comprises providing a sufficient amount of solvent suitable to solvate the binder to provide fluidity, not only to the binder, but to the entire mixture so that complete dispersion is obtained. However, in addition to the principal, or first solvent, in some cases an additional solvent is employed. This additional solvent is generally an alcohol and is used for two reasons. The use of this second solvent unexpectedly suppresses the background upon development. It also improves the dispersion or solvation of the respective mixtures. The process includes forming a film from the mixture, in most cases, by coating the solvent including mixture onto a substrate, followed by solvent removal. In view of the fact that the finished surface of the medium must be as smooth as possible to prevent mechanically produced nucleation centers, which would provide spurious images, the top surface must be as level as possible in the finished media. Suflicient solvent to provide a moderate amount of self-leveling after knife coating aids in eliminating undue surface irregularities. After solvent removal, which may be speeded up by infrared heating or moderate vacuum application, and following the drying step, the media is ready for use. Particular examples of recording media are set forth in the following examples.

In the examples given below, the pigment or actinic ray sensitive material is Photox 8-01, a zinc oxide manufacture by New Jersey Zinc, of Palmerton, Pa. The resinous film-forming binder was Pliolite S7, which is a resinous copolymer of butadiene and styrene manufactured and sold under that designation by Goodyear Tire and Rubber Co., of Akron, Ohio, or E4127, a resin manufactured by DeSoto Inc., of 1700 ,South Mt. Prospect Road, Des Plaines, 111., which is a mixture of 50 percent resinous solids in toluene. The phthalonitrile came from Eastman Chemical Co. Tenlo70 is a Wetting agent manufactured by =Nopco Chemical Co., Newark, NJ.

EXAMPLE I Composition number 588. Pigment ZnO (Photox 801). Binder Pliolite S-7. Pigment/dry binder weight ratio 4.5.. Nucleation-inducing compound Mandelic acid copper salt.

Pigment/nucleation-inducing compound 750. Sensitivity and density-enhancing compound Phthalonitrile. Pigment to/DDEC 75.

A recording tape, according to the invention, was prepared by mixing together the above ingredients in an orbital ball mill. The ingredients amounted to about milliliters. The materials were milled together for about 1.5 hours, using 100 grams of glass balls.

Suflicient toluene solvent for the binder was employed in each case to achieve desired viscosity for milling and coating. In general, Pliolite S-7 can be used in the range of 38 to 100 grams of each grams of zinc oxide pigment. Tenlo can be added in the range of 0 to .6 gram per 150 grams of zinc oxide pigment. The addition of methanol increases the efl ectiveness of the nucleationinducing compound and can be added in the range from 1 to 16 milliliters per 150 grams of zince oxide. Thereafter, film of the composition was applied by a knife coater at a speedof 2 centimeters per second onto the aluminized surface of a Mylar tape. Following coating, the tapes were dried to a thickness of about 30 percent of the wet coating thickness.

Latent images, or nucleation sites, were subsequently formed on this tape. The developed imag s were found to be sharp with good continuous tone qualities and high differential density from the darkest areas to the background. The resolving power exceeded 256 lines pairs per millimeter.

Each of the tape compositions was recorded upon by forming latent images, followed by development. The developed images were found to be sharp, with good continuous tone quality. Then sensitivity of amount of exposure energy employable to obtain a fully-developed image varied with the several tape compositions. However, each was sufiiciently sensitive to have utility. It was found that the overall sensitivity was directly related to the photon or electron sensitivity of the pigment, and enhanced by the nucleation-inducing compounds.

The examples "below were mixed in the same way and, in some cases, Tenlo-70 was added as a wetting agent. Similarly, in some of the examples, methanol was added to aid in the dispersion of the nucleation-inducing compound, which aids sensitivity.

EXAMPLE II Composition number 577. Pigment ZnO (Photox 801). Binder Pliolite S-7. Pi gment/ dry binder weight ratio 4.5. Nucleation-inducing compound Mandelic acid copper salt.

Pigment/NIC ratio 750. Differential density enhancing compound none.

The recording medium of Example II is identical to that of Example I, except that it does not contain the macrocylic compound-forming material.

EXAMPLE III Composition number 591. Pigment ZnO (Photox 801). Binder Pliolite S-7. Pigment/dry binder weight ratio 4.5. Nucleation-inducing compound Mandelic acid copper salt. Pigment/NFC 750. Differential density-enhancing com- Phthalonitrile.

pound Pigment/DDEC 25.

EXAMPLE IV Composition number 639. Pigment ZnO (Photox 801). Binder E-027. Pigment/ dry binder weight ratio 2.5. Nucleation-inducing compound Mandelic acid copper salt. Pigment/N10 750. Differential density-enhancing compound Phthalonitrile. Pigment/DDEC 200.

EXAMPLE V Composition number 641. Pigment ZnO (Photox 801). Binder E-027. Pigment/dry binder weight ratio 2.5. Nucleation-inducing compound Mandelic acid copper salt. Pigment/NIH 750. Differential density-enhancing compound Phthalonitrile. Pigment/DD'EC 140. Solvent Methanol ml./ 100 g.

pigment). Wetting agent Tenlo-70. Pigment/wetting agent 650.

10 EXAMPLE VI Composition number 642. Pigment ZnO (Photox 801). Binder E-027. Pigment/ dry binder weight ratio 2.5. Nucleation-inducing compound Mandelic acid copper salt. Pigment/NIH 750. Differential density-enhancing compound Phthalonitrile. Pigment/DDEC 130. Solvent Methanol (5 ml./ g.

pigment). Wetting agent Tenlo-70. Pigment/wetting agent 650.

EXAMPLE VII Composition number 643. Pigment ZnO (Photox 801). Binder E-027. Pigment/ dry binder weight ratio 2.5/1. Nucleation-inducing compound Mandelic acid copper salt. Pigment/NIH 750. Differential density-enhancing compound Phthalonitrile. Pigment/DDEC 120. Solvent Methanol (5 ml./100 g.

pigment). Wetting agent Tenlo70. Pigment/wetting agent 650.

EXAMPLE VIII Composition number 604. Pigment ZnO (CO-026-6A). Binder Pliolite S-7. Pigment/ binder dry weight ratio 4.5. Nucleation-inducing compound Mandelic acid copper salt. Pigment/NIC 750. Sensitivity and density-enhancing compound Phthalonitrile. Pigment/DDEC 35.5.

After preparation of the medium, the medium is exposed to various radiation so as to have a latent image of nucleation sites formed thereon by the corresponding ions, electrons, or photons, which are generically considered actinic rays.

The electrons, ions or photons may be formed in relatively narrow actinic ray beams and caused to scan the recording medium to establish the desired pattern of nucleation centers. Such a scheme is depicted in FIG. 1 where a beam source 2 is provided to generate a beam of ions, electrons or photons with which to scan a recording medium 4 according to the invention. The beam 3 is capable of being deflected orthogonally, as indicated by the X-Y axes, by means of apparatus and techniques well known in the art. A beam of light or photons may be generated and caused to scan the recording medium 4 by a cathode ray tube, particularly of the type known as a flying-spot scanner. The electron beam may be generated by any of the well-known electron gun devices used in cathode ray tubes, for example. In the cases where scanning and nucleation are accomplished by ions or electrons, it will be appreciated that beams of these energy forms must be generated in vacuo and the recording medium 4 will also need be exposed thereto in vacuo. The requisite vacuum chamber 6 is indicated in FIG. 1 by dotted lines, since it may be of any design or structure to accomplish the purpose of permitting an evacuated volume to be established and maintained therewithin. Normally, since it will be desirable to insert and remove recording media (either discretely or continuously), parts (not shown) for such purposes will be provided in the vacuum-forming structure. Likewise not shown but desirable are means for pumping down or evacuating the chamber 6 whenever the desired vacuum therewith is lost, as by opening the chamber to remove recording media. It will also be understood that, since the recording media of the present invention are usually light-sensitive, the recording step should be carried out in a lighttight or dark box which excludes light of the frequency or frequencies to which the recording media are sensitive. In the case of optical or photon exposure, however, it is not necessary to provide the recording medium in a vacuum, except for the development step.

A low tape speed recording system is illustrated in FIG. 3. In a low-tape speed nucleation recorder, images have to be developed within a few millimeters of the writing beam, thus the developing station has to be in the same enclosure 10 and at the same ambient pressure with the writing beam. The tape 12 is transported through the recorder by a drive capstan 14, a feed reed 16, a take-up reel 18 and an idler roll 20.

For electron beam recording, the development process has to be carried out at less than 10- torr ambient to avoid electron scattering. At this low pressure, there is very little probability of thermalization by gas-gas collision and, therefore, special precautions must be practiced to avoid overdevelopment downstream for the writing station.

Low thermal energy atoms are best suited for the development of the slow moving tape and are generated by a large area source 24, such as a copper braid-covered zinc wire. The source 24 is housed within a shroud 26. Even at 10* torr, enough oxygen can leak into the housing 10 to aifect the efliciency and life of the source 24. A protective gas, such as hydrogen or nitrogen, can be leaked into the shroud 26 through a selectively permeable plug 28, suitably a platinum foil, in the case of hydrogen.

The electron gun 30 is housed in a separate barrel 32 having an upper chamber 34 for receiving the gun 30. A first diffusion pump 36 maintains the electron gun chamber 34 at 10' torr, and a second pump maintains the writing area at 10- torr. The beam 39 emitted from the gun passes through aperture 38 and is focused and defiected by coils 40, 42 which surround the barrel 32 to form scanning traces which selectively nucleate the surface of the tape 12 at the writing station 44.

The output end of the shroud is directed at a location immediately preceding the writing station 44. The source 24 emits a suflicient number of atoms which are carried to the Writing station by the tape 12. Because of the direction superimposed on the atoms by the source and the lateral confinement by the tape edges, most atoms will be captured by the freshly-generated nucleating sites in the scanning beam path. Even though incident rates may exceed 10 atoms/cm. sec. for the area immediately preceding the freshly-written trace, the overall surface concentration should stay below critical at all times. The removal of the atoms on the surface of the tape by the leading edge of the continuously-growing Z-dimensional image will equal the incident flux.

In some cases, however, the zinc atoms may not impinge upon the recording medium prior to the electron beam irradiation, because of sub-image formation. It has been obeserved that the more sensitive recording tape formulations tend to contain a larger number of low free energy sites which are randomly distributed over the surface. Zinc atoms incident upon such a surface will develop an image that is generally not visible to the naked eye, thus termed sub-image. However, once exposed to the recording electron beam, the already existing sub-image will compete with the real image formation resulting in an apparent reduction of the overall sensitivity. Or otherwise stated, the onset of condensation for fur her development of the sub-im ge precedes that for the heal image in the final development step and, consequently, reduces the differential density to a lower value.

A low-speed tape recording system which incorporates a moving wall development station is generally indicated at 50 in FIG. 4. The recording system 50 is quite similar to the recording system illustrated in FIG. 3. It has a sensitive tape 52, such as those described above, which is transported by a similar reel system through an exposure station 54 to the moving Wall development station 56. Writing is accomplished by electron gun 58 which produces a scanned and modulated electron beam 60 which produces the nucleated latent image on the tape. The entire structure is positioned within a suitable enclosure, suitable for vacuum maintenance.

The moving wall developer 56 comprises an endless belt 62 which is engaged around propulsive and guide rollers to define a narrow development chamber slot 64. The tape 52 is preferably made of stainless steel, metallized polyimide, or other material which will not degrade under the temperatures found in the installation. Zinc metal vapor sources 66 and 68 provide for zinc metal vapor in the very narrow development chamber. Zinc atoms are injected from the two sides from sources 66 and 68 (or from the top) and subsequently collide with the wall surfaces of belt 62 and the recording medium 52. Because the walls are not stationary, no zinc deposition occurs, and only the very slow-moving recording tape 52 is able to pick up the atoms. Furthermore, the high frequency of collisions with wall tape 62 extracts excess thermal energy from the zinc atoms leading to a greater optical density.

In yet another embodiment, a macrocyclic compoundforming material may be vaporized and subsequently injected between the moving walls, either from the top, as shown in FIG. 4, 69, or from the sides, thus interacting mainly on the recording medium surface with the zinc .atoms so as to form stable phthalocyanine dyes.

Such complex development devices are not necessary, but other stationary or moving development techniques can be employed. For example, Alfred P. Kaspaul Pat. No. 3,585,965 illustrates another development method and criteria. Stated more broadly: As a result of the impingement of electrons, ions or photons on the recording substrate, the surface thereof is provided witha latent image comprising a number of nucleation sites, the pattern of which corresponds to the indicia to be reproduced. 'When such a latent image is exposed to the vapor of a metal, for example, atoms or molecules from the vapor are selectively attracted to and retained in place only by the nucleated areas comprising the latent image. By the invention, it is calculated that each atom in a nucleating site may capture as many as 10,000 atoms from the vapor. Thus a quantitatively significant deposition of the material of the vapor upon the recording medium in any desired pattern may be achieved. Where the deposition pattern represents symbolic or pictorial information, such information will be readily visible to the eye.

The development of a latent image of such prenucleated areas may be achieved either sequentially or simultaneously with respect to the step of exposure, as desired. The necessary vapor may be formed by heating a supply of the vapor material in its solid state to form a vapor thereof and introducing the vapors thus formed into an evacuated chamber containing the exposed recording medium. The vapor or molecular beam may be supplied from a source or furnace disposed in the sensitization chamber or from a source external thereto which may be controllably opened or connected to the sensitization chamber to permit the vapor to be introduced thereinto. The exposed recording medium may also be transferred to a separate chamber for development by exposure to the vapor.

As noted, it is possible to expose a sensitized recording medium to the development vapor or molecular beam during the exposure step so that the latent image is developed as it is being formed. However, it may be ef able to develop the latent image sequentially with respect to its formation and after it has been completely formed. In general, it has been found convenient to provide an evaouable chamber in which the recording medium is disposed and containing as well an electron or ion source and a vapor source which is controllably isolated from the chamber interior. After evacuating the chamber, the latent image is formed by electrons or ions. The vapor source may be activated during this step and, thus, ready to deliver vapor to the chamber. After the latent image is formed, the vapors are then admitted to the chamber interior and the now-sensitized recording medium exposed thereto.

To render the latent images visible or otherwise useful, the recording medium is exposed in vacuo to the vapor of a material which selectively grows only on and from the sensitized or nucleated areas thereof. Generally, the developer materials are metals, such as magnesium, zinc, cadmium or mercury. The latter of these metals, namely mercury, may, under some circumstances, be less desirable than the other metals listed for this purpose, although under suitable temperature conditions, mercury may be useful and can produce images of relative permanence and with other desirable characteristics. As suggested in FIG. 1, development can be performed in the same evacuated chamber in which the latent images are formed. Alternatively, a separate developing chamber may be utilized.

Development or formation of a visible image takes place under the usual and known conditions governing the deposition of metals in vacuo. Thus, the development step can be performed in conventional deposition or coating apparatus, comprising a vacuum chamber in which a boat or wire source (i.e., nickel, Nichrome or other material) is used to vaporize the development metal. The recording media to be developed may be located at a distance from the vapor-producing source which does not unduly exceed the mean free path existing in the chamber at given conditions. Pressures in the range of about 10' to 10- mm. of mercury may be used for this purpose. Helium-argon or argon-hydrogen mixtures may also be employed and introduced into the chamber to modify the velocity at which the vapor molecules reach the surface of the recording medium, permitting a greater degree in controlling the contrast of the image being developed. It is also possible, instead of directly vaporizing a metal, to employ a metal compound which may controllably be caused to undergo decomposition on the nucleation sites and result in the deposition of metal thereat. To achieve this result, the recording medium must be maintained at the proper temperature, generally corresponding to the decomposition temperature of the compound. Nickel carbonyl is a typical example for vaporplating from a metal compound.

The manner in which the macrocyclic compound-forming materials contrast ratio is not fully understood. FIG. 5 illustrates the density versus exposure curve of the tape of Example I as the upper left curve, with the same information for the tape of Example H in the lower right curve. The phthalonitrile is in supersaturated solution with respect to the other constituents of the tape. Under such conditions, phthalonitrile vapor is constantly driven out of the mixture. The phthalonitrile vapor then interacts with the incoming zinc atoms chemically, as well as physically. The result on the zinc image, as seen on scanning electron microscope photographs, is a spongy deposit rather than a metallic, crystalline deposit. When zinc is used as a development metal at pressures below torr and an exposed tape of Example II, the zinc deposits in the image area as a series of small platelets, which are highly specular reflective. The inclusion of the phthalonitrile in the tape medium, or the presence of it during development results in a more sponge-like deposit of much lower speculaf reflection, hus resulting in an improved differential density.

14 Two possible effects might be responsible for the much improved reflective optical densities:

(l) Thermalization of zinc atoms by phthalonitrile vapor,

(2) Chemical reaction of imagewise-deposited zinc atoms with phthalonitrile, thus forming a macrocyclic compoundthe zinc phthalocyanine dye.

This invention having been described in its preferred embodiment, and several alternative embodiments disclosed, it is clear that this invention is subject to various modifications and embodiments within the spirit of the invention and without the exercise of the additional inventive faculty. Accordingly, the scope of this invention is defined by the scope of the following claim.

What is claimed is:

1. A nucleation-recording medium comprising:

a resinous film-forming vehicle in which is dispersed with the aid of a solvent suitable to solvate the resin ous film-forming vehicle:

an actinic ray sensitive compound selected from the group consisting of oxides of titanium, tantalum, indium, magnesium, germanium, zinc, iron, tin and bismuth, sulfides of calcium, zinc, cadmium and indium, and boron nitride, calcium tungstate, beryllium aluminide, lithium carbonate, zinc carbonate, cadmium niobate, lithium niobate, calcium magnesium silicate )cesium-activated( and mixtures thereof;

a nucleation-enhancing material comprising a metallic salt selected from the group consisting of copper halide, copper (II) acetylacetonate, nickel (II) acetylacetonate, zinc (II) acetylacetonate, chromium (III) acetylacetonate, bismuth trioxide (Bi O cuprous chloride, a mixture of cuprous chloride and triethylamine salt of tetra cyanoquinomethane, a mixture of cuprous chloride and copper (II) acetylacetonate, a mixture of copper formate and cuprous chloride, cupric sulfate, cupric chloride hydrated with 2 water molecules, cuprous bromide, cuprous iodide, cupric bromide, cuprous sulfite, cupric thiocyanate, cuprous sulfide, cupric molybdate, cupric lactate, cupric formate, copper p-toluene sulfinite, cupric salicylate, cupric linoleate, cupric acetate, glycine cupric salt, cupric stearate, cupric oleate, cupric tartrate, cupric citrate, dextro-levo malic acid copper salt, cupric oxalate, bis (ethyl acetoacetate) copper, bis (l-phenyl 1,3-butane-dione) copper, cupric dimethyl dithiocarbamate, cuprous sulfate B napthol, cuprous acetylacetonate, mandelic acid copper salt, silver benzotriazole, tin, chloride, nickel chloride, chromium chloride, nickel sulfate, nickel fluoride, silver nitrate, and silver oxide; and, the improvement comprising:

a compound capable of forming phthalocyanine dye for enhancing the reflective optical density of the developed medium, said compound is selected from the group consisting of phthalonitrile, phthalimide, monoiminophthalimide, 1,3- diiminoisoindoline, dimethylfumaric dinitrile, dimethyl malic dinitrile, tetrahydrophthalonitrile, tetrachloro-phthalonitrile, 4 phenylphthalonitrile, citraconic dinitrile, naphthalene 2,3 dinitrile, ortho cyanobenzonitrile, and orthodinitriles of benzene, naphthalene and anthracene.

References Cited UNITED STATES PATENTS NORMAN G. TORCHIN, Primary Examiner W. HENRY LOUIE, JR., Assistant Examiner

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