Photographic article with composite oxidation protected anti-static layer
United States Patent 1191 Rasch et a1.  
 1451 Apr. 1, 1975 [75] Inventors: Arthur A. Rasch, Webster; Wilbur C. Hodges, Rochester, both of NY.  
 [73] Assignee: Eastman Kodak Company,  
 Rochester. NY.  
  22 Filed: May 22,1972  
  21 App1.No.:255,486  
 [52] US. Cl 96/87 A. 96/1.5. 96/1.8  
 151] Int. Cl. G03c 1/78 [58] Field of Search 96/1.5. 87 A, 86 R, 87 R. 96/1.8; 117/206, 106  
 [56] References Cited UNITED STATES PATENTS 2,687,373 8/1954 Hcring 961/86 R 2.786 778 3/1957 Palmquist 117/106 2,808,351 10/1957 Colbert ct a1. 117/106 2,852,415 9/1958 Colbert ct a1. 117/211 2,939,787 6/1960 Giaimo 96/l.5  
 3,181,461 5/1965 Fromson 96/86 R 3,356,529 12/1967 Kiscr ct a1 117/106 FOREIGN PATENTS OR APPLICATIONS 309,659 2/1928 England 96/87 A 112.409 6/1940 Australia 96/87 A Primary Eruminer-David Klein Assistant E.\&#39;aminer lohn L. Goodrow Attorney, Agent, or FirmJ. T. Lewis [57] ABSTRACT A photographic article having a dielectric support and a hydrophilic colloid coating is protected against the accumulation of a static electrical charge and, optionally non-adhesion of the colloid coating by the provision of a composite layer including a conductive layer portion having a surface resistivity of less than 10 ohms per square and a protective metal oxide layer portion overlying a major surface of the composite layer portion remote from the support. A second protective metal oxide layer portion may be interposed between the support and the conductive layer portion.  
 6 Claims, 4 Drawing Figures PHOTOGRAPHIC ARTICLE WITH COMPOSITE OXIDATION PROTECTED ANTI-STATIC LAYER This invention relates to an article having a hydrophilic colloid coating and a dielectric support which incorporates a composite anti-static layer. In one aspect this invention relates to a composite anti-static layer interposed as an adhesive subbing layer between a hydrophilic colloid coating and dielectric support. In another aspect, this invention relates to a photographic article containing a radiation-sensitive material in which a hydrophilic colloid coating is bonded to a dielectric support and the resulting article is protected against static charge accumulation by a composite conductive layer.  
  Prior to this invention it has been recognized that in photographic structures incorporating a photosensitive emulsion coating on a dielectric support the accumulation of static charge on the support can have the undesirable effect when accidentally discharged of fogging the emulsion coating in the vicinity of the discharge. Static charge accumulation is particularly troublesome in roll films not containing gel pelloid layers or paper interleavers, as is frequently the case in film applications requiring minimal weight and/or rapid processing.  
  One approach that has been suggested in the art for dissipating or controlling static electrical charges on dielectric photographic supports involves the utilization of a thin metal coating having sufficient conductivity to prevent high, localized static charge accumulation. The principal disadvantages associated with metallic anti-static coatings are that when they are deposited in thin films of less than a 100 angstroms they become oxidized during the various photographic processing steps and upon storage in association with the photographic emulsion coatings, so that their conductances progressively decline and, hence, their antistatic properties are diminished. If the metal coatings are applied in sufficient thicknesses to offset their declining conductivities in the photographic environment, the increased thicknesses produce undesirable increases in optical density. In either instance the metal anti-static coating can interact with the photosensitive emulsion coating to produce undesirable fogging. Further, the metal coating may inhibit bonding of a photographic emulsion to the support, so that metal antistatic coatings are typically placed on the support surface opposite to that of the photographic emulsion coating. A further disadvantage is that when a polymer support having a freshly deposited metal anti-static layer thereon is wound in reel form, the metal frequently will adhere to both adjacent surfaces. When this occurs the metal may cause blocking, i.e., prevent unwinding of the reel or, if unwinding is in fact accomplished, the metal coating may be wholly or partially and randomly transferred to the opposite surface of the polymer support.  
  Prior to this invention thin layers of metal and inorganic oxides having been associated in various types of articles to influence their optical properties, as is illustrated by Colbert et al. U.S. Pat. No. 2,501,563, issued Mar. 21, 1950, relating to mirrors and Dreyfus et al. U.S. Pat. No. 2,854,349, issued Sept. 30, 1958, relating to welding plates.  
  However, prior to this invention there has been no recognition that composite metal-inorganic oxide layers may be formed having anti-static properties which are sufficiently stable to be compatible with the demanding requirements of photographic article use and processing environments. Further, it has not been previously appreciated in the art that composite anti-static layers are capable of bonding hydrophilic colloid coatings to dielectric supports. I-Iydrophilic colloid coatings, such as those utilized to form radiation-sensitive emulsion coatings in the photographic arts, are neither dimensionally stable nor protective in aqueous solutions. For example, hydrophilic colloids ingest water when brought into contact with aqueous solutions, such as photographic processing solutions. The ingestion of water creates substantial dimensional changes and/or large internal stresses, particularly at a bonding surface. Typically, a hydrophilic colloid coating may ingest a quantity of water several times its original weight leading to doubling, tripling or greater increase in its original thickness. When a hydrophilic colloid is deposited directly on a support, such as a hydrophobic film support, it can be sloughed from the support on swelling of the layer during exposure to aqueous solutions. Accordingly the art has heretofore generally utilized subbing layers to facilitate adhesion of hydrophilic colloid coatings to support surfaces. Since the hydrophilic colloid coatings must inherently be permeable to aqueous solutions in order to allow photographic processing solutions to reach the radiation-sensitive materials and addenda dispersed in the colloid, the subbing layer is, of course, brought into direct contact with the processing solutions and mustbe resistant to attack thereby if the colloid is to remain bonded to the support.  
  It is an object of this invention to provide a composite anti-static layer in an article having a dielectric support and a hydrophilic colloid coating in order to provide anti-static protection of improved stability.  
  It is another object of this invention to provide an article having an adhesive anti-static subbing layer for bonding a hydrophilic colloid coating to a dielectric support, particularly a hydrophobic support.  
  It is still another object to provide a photographic article containing a radiation-sensitive material, a hydrophilic colloid coating and a dielectric support that is protected from static charge accumulation by a composite anti-static layer that is compatible with radiation-sensitive materials, addenda and their processing solutions.  
  It is a further object to provide an article incorporating a composite anti-static layer on a flexible support that is resistant to blocking.  
  These and other objects of this invention are accomplished in one aspect by providing an article comprising a hydrophilic colloid coating and a dielectric support for the hydrophilic coating which incorporates a composite layer including an electrically conductive layer portion exhibiting a surface resistivity of less than 10 ohms per square which is capable of oxidation to a less conductive state. A protective inorganic oxide layer portion is bonded to a major surface remote from the support of the electrically conductive layer portion to retard oxidation thereof. The article can incorporate a radiation-sensitive material. In another aspect of this invention the composite .layer can be a subbing layer interposed between and bonded to the hydrophilic colloid coating and the dielectric support.  
  The composite anti-static layer is a binderless layer which consists essentially of an electrically conductive layer portion and protective inorganic oxide layer portion. The term binderless layer&#34; refers to a layer that is substantially free of organic adhesive materials and refers particularly to the absence of those organic adhesive and binder materials commonly utilized in the photographic arts, such as natural and synthetic polymeric binders and colloidal vehicles. The composite layer performs the function of a Conventional antistatic layer in an improved manner and can also be utilized as a subbing layer to promote adhesion ofa hydrophilic colloid coating to a dielectric support surface. The composite anti-static layer can be used in combination with conventional anti-static and/or adhesive subbing layers, but is preferably substituted for one or both.  
  In the course of processing after exposure, photographic articles bearing hydrophilic colloid coatings are typically brought into association with alkaline, acid and/or neutral aqueous solutions. In the course of such processing the colloid coating, being water perme able, ingests appreciable quantities of aqueous solution, and the increase in volume of the colloid coating can produce marked dimensional changes and/or internal stresses therein. It is a surprising feature of this invention that the composite layer utilized in the practice of this invention remains comparatively stable in these metal oxidizing photographic processing environments. It is also surprising that the composite layer is capable of binding the colloid coating, despite its internal ingestion of processing solutions, to a support. The composite layer is also quite adherent even when confronted with mechanical stress, as, for example, when binding a colloid coating to a flexible support that is wound or repeatedly flexed. The properties of the composite layer are all the more surprising when compared with metal anti-static coatings heretofore applied to photographic supports. By contrast, hydrophilic colloid coatings overlying metal anti-static layers frequently delaminate from flexible supports when mechanical stress, as by flexing, occurs. Metal anti-static layers have also been observed to be highly oxidized in photographic processing environments, and to actually inhibit binding of a colloid coating to its support rather than to acts as an adhesive. Additionally, while blocking and/r adhesive transfer of freshly deposited metal anti-static layers on rolled film is frequently observed, film employing composite layers according to this invention do not block nor is the composite layer or the colloid coating transferred in whole or in part.  
  The conductive layer portion may be comprised of any metal heretofore utilized as an anti-static layer in a photographic article. The metals that are generally preferred are those yielding a low level of optical density for a given resistance value. Chromium, nickel, manganese, bismuth, copper, aluminum, iron, silver and are exemplary metals possessing low levels of optical density at desired levels of surface resistivity. The specific metal or metals chosen for use may depend upon the specific parameters, such as initial coat, optical density, conductance, short and long term oxidation resistance, etc., that may be operative for any particular application. It is further specifically recognized that since the metal layer portion is in all cases separated by the protective inorganic oxide layer portion from a hydrophilic colloid coating, metals. may be chosen for the metal layer portion that would be detrimentally reactive with the colloid coating if utilized alone, and, more specifically, metals that would, if used alone, fog or de sensitize a photographic emulsion coating can be uti lized.  
  In order to impart protection against static electrical discharge it is necessary that the conductive layer portion exhibit a surface resistivity of less than 10 ohms per square. In photographic applications it is generally preferred that the conductive layer portion exhibit a surface resistivity of less than 10 ohms per square. In order to insure that in all localized areas a surface resistivity of less than 10 ohms per square is attained it is preferred that the conductive layer portion have an overall surface resistivity of less than 10 ohms per square. With conductive layer portions having overall surface resistivities of less than 10 ohms per square photographic reproductions may be uniformly and reliably obtained with no evidence of optical alterations attributable to localized discharge of static electrical charge.  
  As is well understood by those skilled in the art surface resistivity is determined by measuring the resistance between two parallel electrodes of a given length spaced apart by the same distance along a surface. Since an increase in the length of the electrodes tends to decrease the resistance observed by an amount equal to that by which the resistance would be increased by lengthening the spacing between the electrodes by a like increment, it is apparent that the electrode length and spacing is not material, so long as they are identical. Hence the surface resistivity expressed in ohms per square is a resistance measurement taken for the special case in which electrode length and spacing are identical and therefore mutually cancelling parameters.  
  The conductive layer portion is preferably formed no thicker than is required to yield the desired conductance characteristics, since further increase in the thickness of the conductive layer portion serves to increase the optical density of the photographic article with which it is associated. Generally conductive layer portions of acceptable conductances and with acceptable optical densities below about 0.5 can be obtained using conductive layer portions of below Angstroms in thickness. Preferably the conductive layer portions are held below 50 Angstroms in thick ness. It is recognized that in those applications where the optical density of the conductive layer is of no concern the conductive layer portion may be increased in thickness significantly; however, conductive layer portions of thicknesses above about 1000 Angstroms are not required or contemplated for the practice of this invention.  
  The protective inorganic oxide layer portion is directly bonded to the surface of the conductive layer portion remote from the support to protect the conductive layer portion from oxidation that will decrease its conductivity. Metal oxides are particularly suitable as protective agents, since they are characteristically water insoluble and substantially chemically inert toward common photographic processing and developing solutions as well as toward radiation-sensitive colloid coatings. Preferred protective oxides are those which exhibit a low level of optical density and, most preferably, are substantially transparent. Oxides of silicon, such as silicon monoxide and silicon dioxide, have been observed to be superior oxides for the practice of this invention, since they are substantially water insoluble and chemically inert in photographic processing and use environments and are essentially transparent. Silicon oxides are also preferred since they can be vapor deposited by heating to vaporization temperatures that are low as compared to those required for vaporizing other oxides. Metal oxides such as aluminum oxide, magnesium oxide, tantalum oxide, titanium oxide and boro-silicon oxide are also recognized to be particularly suited to the practice of this invention. The protective oxides are useable in both crystalline and amorphous forms. It is specifically contemplated that glasses may be utilized, particularly glass forming mixtures of inorganic oxides. The use of crystalline mineral mixed oxides is also contemplated.  
  The inorganic oxide protective layer portion may be utilized in any thickness capable of reducing oxidation of the conductive layer portion. In order to impart a significant reduction in the rate of oxidation of the conductive layer it is desirable that the protective layer portion exhibit a thickness of at least Angstroms. To preserve the lowest possible optical densities in photographic articles it is generally desired to utilize the minimum thickness of inorganic oxide capable of protecting the conductive layer portion. For photographic applications it is preferred to limit the thickness of the protective layer portion to less than 1000 Angstroms with protective layer portion thicknesses of less than 500 Angstroms being most preferred. The exact choice of protective layer thickness is influenced by such factors as its required transparency and degree of impermeability to oxidants in photographic processing and use environments.  
  In completing the composite layer relied upon for protection of the photographic article against static charge accumulation it is preferred, where a particularly high degree of protection against attack of the conductive layer portion is desired or where the support is itself reactive with the conductive layer portion, to include a second protective inorganic oxide layer portion between the support and the conductive layer portion. The second protective layer portion may be identical to the first protective layer portion bonded to the surface of the conductive layer portion remote from the support. Together the protective layer portions form a sandwich structure with the conductive layer portion that protects both its major surfaces. The provision of a second protective inorganic oxide layer has been observed to markedly improve the stability of composite layers desposited on common photographic film polymer supports.  
  The composite layer utilized in the practice of this invention may be advantageously applied to any conventional photographic article support which is dielectric; that is, exhibits a surface resistivity in excess of at least 10 ohms per square and, most commonly, 10 ohms per square, and, particularly, to those dielectric supports which present a hydrophobic bonding surface. Where the composite layer is applied to any support of greater resistance it will impart improved protection against the accumulation of static electrical charge. Where the support is hydrophobic in character, as is typical of polymer film support employed in the manufacture of photographic articles, the composite layer may be utilized to present to the hydrophilic colloid coating which follows, a hydrophilic bonding surface. This then eliminates any further need for resort to conventional surface preparations of hydrophobic supports for rendering them hydrophilic and hence more adherent to the hydrophilic colloid coating. It is, of course,  
 recognized that such conventional hydrophilic surface preparations can still be utilized in addition to depositing the composite layer, if this is desired. Also, it is not essential that the composite layer be bonded to that surface of the support which receives the colloid coating, although this is preferred. it is specifically contemplated that most photographic articles fabricated according to this invention utilizing hydrophobic polymer film as coated supports will be benefitted by the composite layer deposited thereon both by the imparting of anti-static properties and by the improvement in the adherency of the hydrophilic colloid coating which follows.  
  Exemplary dielectric supports useful in the practice of this invention include supports such as glass, polymers, and the like. Polymer supports and polymer coated supports are preferred supports. It is a surprising and useful feature of this invention that the composite anti-static layers are readily adherent to hydrophobic polymer supporting surfaces. Typical hydrophobic polymers which form supporting surfaces according to this invention include cellulose esters such as cellulose nitrate and cellulose acetate; poly(vinyl acetal) polymers, polycarbonates, polyesters such as polymeric, linear polyesters of bifunctional saturated and unsaturated aliphatic and aromatic dicarboxylic acids condensed with bifunctional polyhydroxy organic compounds such as polyhydroxy alcohols, e.g., polyesters of alkylene glycol and/or glycerol with terephthalic, isophthalic, adipic, maleic, fumaric and/or azelaic acid; polyhalohydrocarbons, such as polyvinyl chloride; and polymeric hydrocarbons, such as polystyrene and polyolefins, particularly polymers of olefins having from 2 to 20 carbon atoms. The above polymers may be utilized in the form of flexible films or other unitary supports or may be utilized as coatings on glass, paper and polymer supports. A preferred class of coated supports is alpha-olefin resin coated paper supports, such as paper supports coated with polyethylene, polypropylene, ethylene-butene copolymers and the like.  
  The hydrophilic layer to be adhesively bonded to the hydrophobic polymeric support surface can be formed from one or more hydrophilic, water permeable colloid forming substances including both naturally occurring substances such as, for examle, proteins such as gelatin and gelatin derivatives; cellulose derivatives; polysaccharides such as dextran, gum arabic and the like and synthetic polymer substances, such as water soluble polyvinyl compounds like poly(vinylpyrrolidone), acrylamide polymers and the like.  
  The hydrophilic colloids utilized can also contain other synthetic polymeric compounds such as those which increase the dimensional stability of the colloid layers. Suitable synthetic polymers include those described, for example, in Nottorf U.S. Pat. No. 3,142,568, issued July 28, 1964; White U.S. Pat. No. 3,193,386, issued July 6, 1965; Houck et al. U.S. Pat. No. 3,062,674, issued Nov. 6, 1962; Houck et al. U.S. Pat. No. 3,220,844, issued Nov. 30, 1965; Ream et al. U.S. Pat. No. 3,287,289 issued Nov. 22, 1966; and Dykstra U.S. Pat. No. 3,411,911 issued Nov. 19, 1968. Particularly effective are those water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, those which have cross-linking sites which facilitate hardening or curing described in Smith U.S. Pat. No. 3,488,708, issued Jan.  
 6, 1970, and those having recurring sulfobetaine units as described in Dykstra Canadian Pat. No. 774,054.  
  The hydrophilic colloid can be hardened by various organic or inorganic hardeners, alone or in combination, such as the aldehydes and blocked aldehydes described in Allen et a1. U.S. Pat. No. 3,232,764, issued Feb. 1, 1966, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers as described in Burness et a1. U.S. Pat. No. 3,539,644 issued Nov. 10, 1970, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, polymeric hardeners such as oxidized polysaccharides like dialdehyde starch and oxyguargum and the like.  
  Where the article formed is employed in forming an image by exposure to activating radiation, the hydrophilic colloid coating to be bonded to the support will contain in or on it a radiation-sensitive material. This material may be panchromatic or orthochromatic material, sensitive only to X-rays or sensitive to selected portions of the electro-magnetic spectrum. In one form of the invention the radiation-sensitive portion of the photographic article can contain a single, unitary hydrophilic colloid coating having dispersed therein the radiation-sensitive material together with photographic addenda to form a radiation-sensitive emulsion coating (e.g., a photographic or photosensitive emulsion coating) having a hydrophilic colloid surface. In alternative forms the radiation-sensitive portion of the article can comprise a plurality of coatings with the radiationsensitive material or materials being contained in some or all of the coatings, but not necessarily in the hydrophilic colloid coating immediately adjacent the composite anti-static layer or support. For example, as is characteristic of color photography, a plurality of hydrophilic colloid coatings can be present sensitized within separate segments of the visible spectrum. Typically the hydrophilic colloid coating nearest the support is itself free of radiation-sensitive material as coated. Suitable hydrophilic colloid layers which can be bonded to a dielectric support surface but which contain no radiation-sensitive material, such as silver halide, when coated include, for example, antihalation layers, nucleated chemical transfer receiving layers, dyemordant layers and the like.  
  Suitable radiation-sensitive materials which can be employed in practicing this invention are sensitive to electromagnetic radiation and include such diverse materials as silver salts, zinc oxide, photosensitive polycarbonate resins and the like. Silver halides are preferred radiation-sensitive materials and are preferably associated with a colloid or synthetic polymer dispersion vehicle to form an emulsion coating or layer. Silver halide emulsions can comprise, for example, silver chloride, silver bromide, silver bromoiodide, silver chlorobromide, silver chloroiodide, silver chlorobromoiodide crystals or mixtures thereof. The emulsions can be coarse or fine grain emulsions and can be prepared by a variety of techniques, e.g., single jet emulsions such as those described in Trivelli and Smith The Photographic Journal, Vol. LXXIX, May, 1939 (pp. 330338), double jet emulsions such as Lippmann emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions such as those described in Nietz et a1. U.S. Pat. No. 2,222,264, issued Nov. 19, 1940; lllingsworth U.S. Pat. No. 3,320,069, issued May 16, 1967, and McBride U.S. Pat. No. 3,271,157, issued Sept. 6, 1966. Negative type emulsions can be made, as well as direct positive emulsions as described in Leermakers U.S. Pat. No. 2,184,013, issued Dec. 19, 1939; Kendall et a1. U.S. Pat. No. 2,541,472, issued Feb. 13, 1951; Schouwenaars British Pat. No. 723,019, issued Feb. 2, 1955; lllingsworth et a1. French Pat. No. 1,520,821, issued Mar. 4, 1968, lllingsworth U.S. Pat. No. 3,501,307, issued Mar. 17, 1970; Ives U.S. Pat. No. 2,563,785, issued Aug. 7, 1951, Knott et a1. U.S. Pat. No. 2,456,953, issued Dec. 21, 1948 and Land U.S. Pat. No. 2,861,885, issued Nov. 25, 1958.  
  The silver halide emulsions employed in the articles of this invention can be sensitized with chemical sensitizers, such as with: reducing compounds; sulfur, selenium or tellurium compounds; gold, platinum or palladium compounds; or combinations of these.  
  The radiation-sensitive colloid coatings can additionally include a variety of conventional addenda both for the colloid and for the radiation-sensitive material. For example, photographic emulsion layers employed according to this invention may include development modifiers, antifoggants and stabilizers, plasticizers and lubricants, brighteners, spectral sensitization agents and color forming materials as set forth in paragraphs IV, V, XI, XIV, XV, and XXII, respectively, of Product Licensing Index, Vol. 92, December 1971, publication 9232, pages 107-110.  
  As previously indicated photographic articles of this invention can be processed with aqueous photographic processing solutions. Photographic articles containing the composite anti-static layers described herein can also be used in non-aqueous processinge.g., in socalled dry processing systems. For example, the subbing layers described herein can be used in silver halide containing articles designed for recording print out images as described in Fallesen U.S. Pat. No. 2,369,449 issued Feb. 13, 1945 or Bacon et a1. U.S. Pat. No. 3,447,927 issued June 3, 1969; direct print images as described in Hunt U.S. Pat. No. 3,033,682 issued May 8, 1962 and McBride U.S. Pat. No. 3,287,137 issued Nov. 22, 1966; and articles designed for processing with heat, such as in articles containing an oxidationreduction image-forming combination with a photosensitive metal salt such as a silver salt as described in Sheppard et al. US. Pat. No. 1,976,302 issued Oct. 9, 1934; Sorensen et a1. U.S. Pat. No. 3,152,904 issued Oct. 13, 1964 and Morgan et a1. U.S. Pat. No. 3,457,075 issued July 22, 1969.  
  It is, of course, recognized that the articles formed according to this invention can, if desired, incorporate anti-static or conducting layers other than or in addition to composite anti-static layers. Such layers can comprise soluble salts, e.g., chlorides, nitrates, etc., ionic polymers such as those described in Minsk U.S. Pat. No. 2,861,056, issued Nov. 18, 1958, and Sterman et a1. U.S. Pat. No. 3,206,312, issued Sept. 14, 1965, or insoluble inorganic salts such as those described in Trevoy U.S. Pat. No. 3,428,451, issued Feb. 18, 1969.  
  This invention may be better understood by reference to the drawings, which are each fragmentary sectional views of photographic articles according to this invention. For ease of illustration the various elements of the articles are not drawn to scale.  
  FIG. 1 illustrates a photographic article 1 comprised of a dielectric support 3. A composite layer 5 overlies and is bonded to one major surface of the support. The composite layer is formed of a conductive layer portion 7, a first protective inorganic oxide layer portion 9, and ide source is then heated and deposited over the nickel a second protective inorganic oxide layer portion 11. layer portion in like manner to a thickness of 400 ang- Overlying the composite layer and bonded thereto is a stroms. The surface resistivity of the composite layer is radiation-sensitive hydrophilic colloid coating 13. measured and the pressure in the chamber then raised FIG. 2 illustrates a photographic article 15 comprised to atmospheric. of a dielectric support 17. The composite layer 19 over- As a control a second support is prepared identically lies and is bonded to one major surface of the support. to the first, except the silicon monoxide protective The composite layer is formed of a conductive layer layer portion is omitted. The supports with the layers portion 21 bonded directly to one major surface of the formed thereon are stored under conditions of 50 persupport and a protective inorganic oxide layer portion cent relative humidity at 50C and after 6 weeks the op- 23. Overlying the composite layer and bonded thereto tical density and the surface resistivity of each article is a photosensitive emulsion coating 25. is measured. Comparative measurements are set forth FIG. 3 illustrates a photographic article 27 comprised in Table I. The optical densities are in each instance net of a dielectric support 29. A photosensitive emulsion optical densities and are determined using an optical layer 31 overlies one major surface of the support and densitometer as the difference between the optical denis bonded thereto with a conventional subbing layer 33. sities of otherwise identical coated and uncoated sup- A composite layer 35 identical to composite layer 5 is ports TABLE 1 Layer When Coated After Storage Surface Resistivity Under In Surface Vacuum Atmosphere Optical Resistivity Optical (ohms/sq.) (ohms/sq.) Density- (ohms/sq.) Density Control (nickel) 320 400 0.10 4400 0.10  
 Composite (Nickel SiO) l7l) I70 0. I 8 420 0.16  
 bonded to the opposite major surface of the support. Although the surface resistivity of the composite FIG. 4 illustrates a photographic article 37 comprised layer increased slightly on storage, its stability was of a dielectric support 39. A photosensitive emulsion much higher than that of the control. layer 41 overlies one major surface of the support and is bonded thereto with a conventional bonding layer EXAMPLE 2 43. A composite layer 45 identical to composite layer 35 19 is bonded to the opp sit maj r surfa f th p- To illustrate the influence of photographic processporting a pair of supports with composite and control layers To further illustrate the invention the following speare prepared according to the procedure of the Examcific examples are included: 4 ple l and bathed for 5 minutes in a buffered aqueous alkaline solution having a pH of about 10 comprised of EXAMPLE I one part by weight p-methyl aminophenol for each four To illustrate the superior stability of a composite anparts hydroquinone (Kodak D-l9 Developer). This is ti-static layer according to this invention as compared followed by bathing for 10 minutes in an acid aqueous to a conventional metal anti-static layer, a polyethylene 45 fixing bath containing sodium thiosulfate (Kodak F-5 terephthalate support coated with a conventional sub- Fixer). No change is noted in the optical density or suring lay r mpris d f a t rp ym 0f acrylonitriie. face resistivity of the composite layer while most of the vinylidene chloride and acrylic acid is provided with plain nickel layer dissolves and the surface resistivity gold stripes spaced one inch apart. The support is increases to greater than 10 ohms per square.  
 placed in a vacuum coating system and electrical connections are made to the gold stripes through appropri- EXAMPLE 3 ate feed-throughs in the system enclosure to permit In Example 1 the small amount of deterioration that electrical measurements to be made on the support imoccurs in the composite layer during storage is due mediately after vapor deposition thereon. The support principally to reaction of the nickel layer portion with is placed 15 inches from vapor sources which consist of the terpolymer subbing layer upon which it is deposelectrically heated tungsten boats containing nickel ited. To eliminate even this limited deterioration of the and silicon monoxide, respectively. A vapor mask incomposite layer, a protective undercoat for the nickel eluding a selectively openable shutter is interposed belayer portion is provided according to the same general tween the sources and the support, and the deposition procedure as in Example 1. Several articles are prechamber is evacuated to a pressure of 2 X 10 Torr. 6O pared in which a 300 angstrom thick film of silicon With the shutter providing a barrier between the monoxide is deposited on the support followed by a sources and the support the nickel is heated to its evapnickel layer portion and then another layer portion of oration temperature. The shutter is moved aside and a silicon monoxide 300 angstroms thick, the relative first layer portion of nickel is deposited on the support thicknesses of the nickel layer portions being proporhaving a thickness of 37 angstroms as measured within tional to their initial surface resistivities. To show aging the vacuum system using a conventional thickness effects the articles are stored for 10 weeks under condimonitor. Thereafter the shutter is returned to its blocklions O 50 percent relative humidity at 50C. Exeming position and the source cooled. The silicon monoxplary results are set forth in Table II.  
 TABLE II Layer Type When Coated After Storage Resistivity Optical Resistivity Optical (ohms/sq.) Density (ohms/sq.) Density SiO Overcoat only 500 0. I 2300 0.05 SiO Overcoat only 290 0.12 1600 0.08 SiO Ovvereout only l50 ().I 730 0.1 l Over and Untlercozit SiO 100 0.16 370 0.16 Over and L&#39;ndercoat SiO 3.l X 0.07 8.6 X l0 006 Over and Undercoat SiO 9.2 X 10 0.09 l.7 X 10&#39;&#39; 0.08 Nickel only 2.2 X It) 0.13 10&#34; 003 The composite layers with protective layer portions both over and beneath the metal anti-static layer porcent relative humidity and 50C. Comparative measurements are set forth in Table III.  
  TABLE III Layer When Coated After Storage Resistivity Optical Resistivity Optical (ohms/sq.) Density (ohms/sq.) Density Aluminum only 60 0.35 300 0.26  
 SiO Al SiO 47 0.37 70 0.34  
  A roll of terpolymer subbed polyethylene terephthalate is loaded into a conventional vacuum roll coater while silicon monoxide is placed in a crucible within the coater for heating by an electron beam to provide a vapor source. The vacuum chamber is closed and pumped down to a pressure of 2.2 X 10 Torr. The silicon monoxide is heated in the electron beam of the vapor source to a point where it is subliming at a high rate. Shutters protecting the support from the silicon monoxide vapor are opened and the support drawn through the vapor at a rate such that the silicon monoxide condensed on the support has a thickness of 180 angstroms. After the roll of support is coated, the vapor source is cooled and the vacuum chamber returned to atmospheric pressure.  
  The coater is reloaded with the same roll and silicon monoxide is removed from the vapor source and replaced with aluminum. The vacuum chamber is pumped down to a pressure of 2.2 X 10&#39; Torr., the vapor source heated, and second layer portion of aluminum deposited over the silicon monoxide. The optical density of the aluminum layer portion is 0.37 (approximately 70 angstroms).  
  Upon returning the vacuum chamber to atmospheric pressure, the aluminum is replaced with silicon monoxide, the same roll reloaded in the machine and, repeating the procedure for forming the first layer portion, a third layer portion of silicon monoxide 180 angstroms in thickness is deposited over the aluminum layer portion.  
  For purposes of comparison an identical roll, except for the absence of silicon monoxide overcoat and undercoat layer portions, is also prepared. These supports are then stored for 7 weeks under conditions of 50 per- The article bearing the composite layer is quite stable as compared to the article bearing only the aluminum layer. When the articles are brought into association with photographic developing and fixing solutions according to the general procedures of Example 1, the aluminum is substantially bleached and its surface resistivity rises to unacceptably high values (above 10 ohms per square) while the composite layer remains low enough to provide excellent anti-static protection for its support.  
 EXAMPLE 5 Repeating the general procedure of Example 4 a silicon dioxide first layer portion approximately angstrons thick is deposited onto an identical subbed polyester support. Thisis followed by a nickel second layer portion having an optical density of 0.10 (25 angstrons thickness) and a third layer portion of silicon dioxide 100 angstrons thick to form the entire composite layer. The article formed is stored at 50 percent relative humidity at 50C for 14 weeks. During this period the optical density decreased to 0.09 and the surface resistivity increased from 1.5 X 10 to 6.5 X 1-0 ohms/square. A similar, but unprotected, article bearing only a nickel layer completely deteriorates under the same conditions, exhibiting a terminal surface resistivity about 10 ohms per square.  
 EXAMPLE 6 Repeating the general procedures of Example 4,-  
 layer portions of silicon dioxide (100 angstrons in thickness), aluminum (25 angstrons in thickness) and silicon dioxide (100 angstrons in thickness) are deposited in the order recited and in separate runs on a similar subbed polyester support. This composite layer has an optical density of 0.14. The composite layer is stored under conditions of 50 percent relative humidity at 50C for 14 weeks during which time the optical density drops to 0.12, while the surface resistivity remains unchanged at 1800 ohms/square. Similar unprotected layers of aluminum deteriorate rapidly when stored under the same conditions. The composite layer is not affected when bathed in photographic developers of fixing baths as in Example 3, while the unprotected aluminum layer dissolves.  
 EXAMPLE 7 Using equipment and techniques as described in Example 4, a thin film of nickel 18 angstroms thick is deposited on a plain, unsubbed polyethylene terephthalate support. A second crucible containing silicon monoxide is contained within the vapor source and is used to deposit a silicon monoxide layer portion over a length of the film support bearing the nickel layer portion. This is achieved without breaking the initial vacuum. The silicon monoxide layer portion is approximately 100 angstroms thick.  
  Samples of film with a nickel layer portion only and with nickel overcoated with silicon monoxide are stored under conditions of 50 percent relative humidity at 50C with the results as set forth in Table IV.  
  The improvement in stability afforded by the silicon monoxide overcoat is amply demonstrated by these results. Samples of these substrates are bathed for minutes in Kodak D-l9 Developer with the result that the unprotected nickel layer is completely removed while the composite layer is not affected. The surface resistivity of the protected nickel layer portion is low enough so that excellent anti-static protection is provided for the support.  
  Additional samples as prepared above are overcoated with a photographic silver bromoiodide hydrophilic colloid gelatin emulsion. When the emulsion coatings are processed photographically, the emulsion sloughs off the support coated with nickel only. However, the emulsion coated over the silicon monoxide protected nickel layer portion adheres thereto during processing, and the fully processed film shows no evident marks caused by electrostatic discharge. A similar emulsion coating on conventional polyethylene terephthalate support without anti-static protection shows severe static marking upon handling and processing under the same conditions.  
 EXAMPLE 8 Using equipment and techniques described in Example 4 a composite layer is deposited on a polyethylene terephthalate support with a terpolymer subbing layer as noted in Example 4. The composite layer consists of approximately 100 angstroms of silicon dioxide, 50 angstroms of aluminum, and approximately 100 angstroms of silicon dioxide, the silicon dioxide forming both a protective overcoat and undercoat for the aluminum.  
  The surface resistivity is 200 ohms/square and does not change significantly when stored from 4 weeks at 50 percent relative humidity at 50C. The surface resistivity and stability of this film is sufficient to provide good permanent anti-static protection to the support.  
  A sample of the support is overcoated with a photographic hydrophilic colloid gelatin emulsion coating. When the emulsion is photographically processed, the emulsion adheres to the composite layer throughout processing and is found to be free of fog caused by electrostatic discharges.  
 What is claimed is:  
  1. In a photographic article comprising a radiationsensitive material, a flexible hydrophobic polyester film support, hydrophilic colloid coating and a composite subbing layer interposed between and bonded to said film and said hydrophilic colloid coating, the improvement in which said subbing layer is vapor deposited and binderless and comprises an electrically conductive layer portion exhibiting a surface resistivity of less than 10 ohms per square which is capable of oxidation to a less conductive state and a protective inorganic oxide layer portion which consists essentially of said inorganic oxide bonded to a major surface remote from said support of said electrically conductive layer portion to retard oxidation thereof; said composite subbing layer having a thickness of less than angstroms and an optical density of at most about 0.5.  
  2. In a photographic article comprising a radiationsensitive material, a flexible hydrophobic polyester film support, a gelatin layer and a composite subbing layer interposed between and bonded to said film and said gelatin layer, the improvement in which said subbing layer is vapor deposited and binderless and comprises an electrically conductive layer portion exhibiting a surface resistivity of less than 10 ohms per square which is capable of oxidation to a less conductive state and a protective inorganic oxide layer portion which consists essentially of said inorganic oxide bonded to a major surface remote from said support of said electrically conductive layer portion to retard oxidation thereof; said composite subbing layer having a thickness of less than 100 angstroms and an optical density of at most about 0.5.  
  3. A photographic article according to claim 2, in which said film support is polyethylene terephthalate.  
  4. A photographic article according to claim 2, in which said radiation-sensitive material is a silver salt.  
  5. A photographic article according to claim 2, in which said support is polyethylene terephthalate, said radiation-sensitive material is a silver halide and said inorganic oxide is silicon oxide.  
 6. A photographic article according to claim 5, in  
 which said silver halide is silver bromochloride.