US 3874879 A
An article, such as photographic article, is disclosed characterized by a dielectric support, a hydrophilic colloid coating and a subbing layer comprised of an electrical conductor, such as a metal, which is oxidiazable if left unprotected and a protective inorganic oxide intimately intermixed with the electrical conductor. The subbing layer can be used to protect against the accumulation of static charge and non-adhesion of the colloid coating to the support. A radiation-sensitive material such as silver halide can be associated with the colloid coating.
Description (OCR text may contain errors)
[ Apr. 1, 1975 ARTICLE WITH OXIDATION PROTECTED ADHESIVE AND ANTI-STATIC LAYER  Inventor: Arthur A. Rasch, Webster, N.Y.
 Assignee: Eastman Kodak Company,
 Filed: May 22, 1972  Appl. No.: 255,487
 US. Cl. 96/87 A, 96/1.5, 96/86 R,
 Int. Cl G03c 1/78  Field of Search 96/87 A, 1.5, 86 R, 1.8; 1 17/106, 21 1  References Cited UNITED STATES PATENTS 2.687.373 8/1954 Hering 96/86 2,786,778 3/1957 Palmquist 117/106 2.852.415 9/1958 Colbert et a1. 117/211 2.939.787 6/1960 Giaimo 96/l.5
3,181,461 5/1965 Fromson 96/86 3,356,529 12/1967 Kiser et a1 117/106 R FOREIGN PATENTS OR APPLICATIONS 112.409 6/1940 Australia 96/87 A 309.659 4/1929 United Kingdom 96/87 A Primary Examiner-David Klein Assistant Examiner-John L. Goodrow Attorney, Agent, or Firm.l. T. Lewis  ABSTRACT An article, such as photographic article, is disclosed characterized by a dielectric support, a hydrophilic colloid coating and a subbing layer comprised of an electrical conductor, such as a metal, which is oxidiazable if left unprotected and a protective inorganic oxide intimately intermixed with the electrical conductor. The subbing layer can be used to protect against the accumulation of static charge and nonadhesion of the colloid coating to the support. A radiation-sensitive material such as silver halide can be associated with the colloid coating.
12 Claims, 3 Drawing Figures PATENTEDAPR 11% .874, 8753 FIG 2 ARTICLE WITH OXIDATION PROTECTED ADHESIVE AND ANTI-STATIC LAYER This invention relates to improving the adhesion of a hydrophilic colloid coating to a dielectric support while protecting the resulting article from static electrical discharge. In one aspect, this invention relates to an article having a hydrophilic colloid coating and a dielectric support which are bonded together by an interposed conductive adhesive layer having a surface resistivity sufficiently low to allow the lateral conduction of electrical charge. In another aspect, this invention relates to a photographic article containing a radiationsensitive material in which a hydrophilic colloid coating is bonded to a dielectric support by an interposed adhesive and anti-static subbing 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 discharge 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 about a 100 angstroms they become oxidixed during storage in association with the photographic emulsion coatings, so that their conductances progressively decline and, hence, their antistatic properties deteriorate. 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 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 partially and randomly transferred to the opposite surface of the support.
Prior to this invention it has been recognized that vapor codeposited metal inorganic oxide layers are readily adherent to siliceous surfaces, such as glass, and may be used to impart anti-static properties to glass surfaces, such as windows, lenses, Windshields and the like. It has been recognized that these metal inorganic oxide layers may in turn receive vapor deposited overlayers, such as vapor deposited metal oxide, metal halide and metal overlayers. For example, Colbert et al. US. Pat. No. 2,808,351, issued Oct. 1, 1957, teaches using certain vapor codeposited metal-inorganic oxide layers in conjunction with vapor deposited overlayers to provide anti-static properties to certain siliceous surfaces.
Prior to this invention there has been no recognition in the art that metal-inorganic oxide layers are compatible with the demanding requirements of photographic use and processing environments. Further, while vapor deposited overlayers have been associated with metalinorganic oxide layers, such overlayers differ markedly in physical properties from hydrophilic colloids. l-lydrophilic colloid coatings are neither dimensionally stable nor are they 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 in the hydrophilic colloid, 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 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 radiationsensitive materials and addenda dispersed in the colloid, the subbing layer is, of course, brought into direct contact with the processing solutions and must be resistant to attack thereby if the colloid is to remain bonded to the support.
It is an 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 having a hydrophilic colloid coating bonded to a dielectric support by an interposed subbing layer which is an antistatic layer and which is relatively inert and insoluble in the course of photographic processing and also that is compatible with radiation-sensitive materials and addenda.
It is a further object to provide an article incorporating a subbing layer that is resistant to blocking.
These and other objects of the invention are accomplished in one aspect by providing an article comprising a dielectric support, a hydrophilic colloid coating and a subbing layer which is contiguous to the support and the hydrophilic colloid coating and is bonded to each. The subbing layer exhibits a surface resistivity of less than l0 ohms per square and is comprised of an electrical conductor capable of oxidation to a less conductive state and a protective inorganic oxide intimately intermixed with the electrical conductor in a'concentration sufficient to retard oxidation of the electrical conductor.
In accordance with this invention, it has been found that a hydrophilic colloid coating can be firmly bonded to a dielectric support surface by means of an adhesive anti-static layer which is contiguous to the supporting surface and to the hydrophilic colloid. The adhesive anti-static layer is a binderless layer which consists essentially of an electrical conductor and a protective inorganic oxide. The term binderless layer 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 adhesive layer performs the functions both of a conventional anti-static layer and a conventional subbing layer and may be used in combination with either or both, but is preferably substituted for conventional antistatic and subbing layers.
It is a surprising feature of this invention that the antistatic subbing layers exhibit conductivity characteristics of improved stability when incorporated into articles, particularly photographic articles, to adhesively bond a hydrophilic colloid coating to a support. It is also surprising that the hydrophilic colloid coating remains tenaciously bonded by the subbing layer of this invention to the support surface when the support surface is hydrophobic, when the article is immersed in colloid swelling aqueous solutions and when the article is subjected to mechanical flexure of the support and colloid. In the course of processing after exposure, photographic articles bearing photosensitive emulsion coatings are often brought into association with alkaline, acid and/or neutral aqueous solutions in accordance with procedures well known to those skilled in the art. In the course of such processing the emulsion coating, being water permeable, ingests appreciable quantities of aqueous solution, and the increase in volume of the emulsion coating can produce marked dimensional changes and/or internal stresses. Despite such changes and stresses the subbing layer utilized in the practice of this invention remains comparatively stable during such photographic processing. Furthermore, the subbing layer is also quite adherent even when subjected to mechanical stress, as. for example, when binding a colloid coating to a flexible support that is wound or repeatedly flexed.
The subbing layer exhibits a surface resistivity of less than 10 ohms per square, this being generally recognized as the maximum surface resistivity permissible if charge is to be conducted from a support. In photographic applications it is generally preferred that the layer 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 subbing layer have an overall surface resistivity of less than 10 ohms per square. With anti-static layers having overall surface resistivity of less than ohms per square it has been observed that photographic reproductions can 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 forthe special case in which electrode length and spacing are identical and therefore mutually canceling parameters.
It is a significant feature of this invention that the electrical conductor, typically a metal, incorporated in thesubbing layer need not itself be resistant to oxidation in the photographic environment in which it is used. That is, it is noted that metals employed according to this invention in combination with inorganic oxides are protected against excessive oxidation in use even where layers formed entirely by like quantities of the same metals have been observed to be highly oxidized. The metals that are generally preferred are those yielding a low level of optical density for a given resistance value. Chromium is observed to be outstandingly suited to the practice of this invention because of its low optical densities at given levels of layer conductiv= ity and because of its exceptional resistance to oxidation when utilized in combination with a protective inorganic oxide. Other metals that are noted to be highly useful in the practice of this invention are silver, copper and nickel. Still other metals which are not objection- I ably reactive with the dielectric support, hydrophilic colloid coating and the radiation-sensitivematerials and addenda which are present in photographic applications can'be used, depending upon the specific pa- I rameters, such asinitial cost, optical density, conductance, short and long term oxidation resistance, etc., that may be operative for any particular application.
The inorganic oxide component of the subbing layer functions to protect the metal against oxidation. Typically inorganic oxides are dielectric materials, and it is a surprising feature of this invention that they are capable of protecting the metal without increasing the elec: trical resistance of the subbing layer beyond useful anti-static levels. The protective inorganic oxides are characteristically water insoluble and substantially chemically inert toward common photograhpic processing solutions as well as toward photographic emulsion coatings. Preferred metal 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, are preferred 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 codeposited with metals by heating to vaporization temperatures that are low as compared to those required for vaporizing other protective oxides. Metal oxides such as aluminum oxide, magnesium oxide, tantalum oxide, boro-silicon oxide (e.g., borosilicate) and titanium oxide are also recognized to be particularly suited to the practice of this invention. The protective oxides are usable in both crystalline and amorphous forms. It is specifically contemplated that glasses may be utilized, particularly glass forming mixtures of oxides. The use of crystalline oxide vapors onto a support. The metal and protective oxide mixture can be blended at a molecular level as taught by Colbert et al, cited above, or can be a mixture of metal particles of up to 200 angstroms in diameter in a continuous matrix of protective oxide as noted, for example, by Milgram and Lu, 39, 4219-24, Journal of Applied Physics. Generally the most intimate physical intermixture obtainable of metal and protective oxide is preferred.
The proportions of metal and protective oxide can be varied as required to yield the desired balance of conductance and oxidation resistance properties. The minimum metal content of the subbing layer is determined by its maximum acceptable surface resistivity. As recognized in the copending application of Rasch et a1., Ser. No. 255,331, filed on May 22, 1972, titled AN AR- TICLE HAVING A HYDROPHILIC COLLOID LAYER ADHESIVELY BONDED TO A HYDRO- PHOBIC POLYMER SUPPORT, a layer finorganic oxide interposed between a hydrophilic colloid coating and a hydrophobic support surface is capable of improving the colloid coating adherency to the support. It is a surprising discovery of this invention that layers containing an intimate intermixture of metal and inorganic oxide improve colloid coating adherency to hydrophobic support surfaces to an even greater extent than layers consisting entirely of inorganic oxide. For this reason it is preferred to incorporate at least 30 percent by weight, based on total subbing layer weight, metal in the layer. On the other hand, in providing metal-rich subbing layers according to this invention having sufficient oxidation resistance to improve hydrophilic colloid adherency it is necessary that the subbing layer be comprised of at least 10 percent by weight and, preferably, at least 20 percent by weight, inorganic 0xide, based on the total weight of the subbing layer. For vacuum codeposited subbing layers of chromium and silicon oxides intended to exhibit subbing layer surface resistivities of less than 10 ohms per square and to improve hydrophilic colloid coating adherency chromium concentrations of from 80 to 30 percent by weight and silicon oxide concentrations of from 20 to 70 percent by weight (each percentage being based on the total weight of the subbing layer) are fully satisfactory.
The overall thickness of the subbing layer can be widely varied. To the extent that the layer is formed so thin that it exhibits undue surface resistivity-Le, does not fully cover the support surfacethe advantages of this invention may be at least partially diminished. At the same time for many photographic applications it is desirable to limit the layer thickness employed so that the optical density of the photographic article is not objectionably increased. For most photographic applications layer thicknesses of from to 1,000 angstroms are desirable, with thicknesses of from 50 to 500 angstroms being preferred.
The subbing layers utilized in the practice of this invention may be advantageously applied to those conventional photographic article supports which are dielectric-that is, exhibit 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 subbing layer is applied to any support of greater surface resistivity, itwill impart improved protection against the accumulation of static electrical charge. Where the support is hydrophobic in character,
as is typical of polymer film supports employed in the manufacture of photographic articles, the subbing layer presents to the colloid coating which, follows a hydrophilic bonding surface. This then eliminates any further need for resort to additional 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 prior or subsequent to depositing the subbing layer of this invention, if this is desired. For example, it may be desirable to coat a hydrophilic colloid coating over the adhesive anti-static subbing layer of this invention to act as a subbing layer for one or more subsequent radiation-sensitive colloid coatings.
The subbing layer can be utilized on any conventional dielectric supporting surfaces and is particularly effective in bonding hydrophilic colloid to a hydrophobic dielectric supporting surface. 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-cg, 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 stoms. The above polymers may be utilized in the form of flexible films or other unitary dielectric supports or may be utilized as coatings on glass, paper and polymer dielectric supports. A preferred class of coated dielectric supports is alpha-olefin resin coated paper supports, such as paper supports coated with polyethylene, polypropylene, ethylene-butene coplymers and the like.
The hydrophilic coat-ing to be adhesively bonded to the dielectric support can be formed from one or more hydrophilic, water permeable colloid forming substances including both naturally occurring substances such as, for example, 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 a1. U.S. Pat. No. 3,062,674, issued Nov. 6, 1962; l-louck et a1. 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.
7 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 al. US. 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 al. US. 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 that portion of the article 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 colloid coating (e.g., a photographic or photosensitive emulsion coating) having a hydrophilic surface. Inalternative forms the radiation-sensitive portion of the article can comprise a plurality of coatings with the radiation-sensitive material or materials being contained in some or all of the coatings, but not necessarily in the hydrophilic colloid coating immediately adjacent the inorganic oxide subbing layer. For example, as is characteristic of color photography, a plurality of colloid coatings can be present sensitized within separate segments of the visible spectrum. Typically the hydrophilic colloid coating nearest the support is itself substantially free of radiation-sensitive material as coated. While each of the coatings can comprise a hydrophilic colloid coating, it is recognized that only the bonding surface of the radiation-sensitive portion of the article need be comprised of hydrophilic colloid in order to achieve the objectives of this invention. Suitable hydrophilic colloid coatings which can be bonded to a hydrophobic 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, dye-mordant 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 oxice, 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. Silver halide emulsions can comprise, for example, silver chloride, silver bromide, silver bromoidide, 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. 330-338), double jet emulsions such as Lippmann emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions 8 such as those described in Nietz et al. US. Pat. No.. 2,222,264, issued Nov. 19, 1940; Illingsworth US. Pat. No. 3,320,069, issued May 16, 1967, and McBride U.S.
Pat. No. 3,271,157, issued Sept. 6, 1966. Negative type 1 emulsions can be made, as well as directpositive emul- Mar. 17, 1970; Ives US. Pat. No. 2,563,785, issued Aug. 7, 1951, Knott et al. US. Pat. No. 2,456,953, issued Dec. 21, 1948 and Land US. 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 paragraph IV, V, XI, XIV, XV, and XXII, respectively, of Product Licensing Index, Vol. 92, December 1971, publication. 9,232, pages 107-110.
As previously indicated photographic articles of this invention can be processed with aqueous photographic processing solutions. Photographic articles containing the inorganic oxide subbing layers described herein can also be used in non-aqueous processinge.g., in so-. called dry processing systems. For example, the subbing layers described herein can be used in silver halide containing articles designed for recording print out im-' ages as described in Fallesen US. Pat. No. 2,369,449 issued Feb. 13, 1945 or Bacon et al. U.S. Pat. 3,447,927 issued June 3, 1969; direct print images as described in Hunt US. Pat. No. 3,033,682 issued May 8, 1962 and McBride US. Pat. No. 3,287,137 issued Nov. 22, 1966; and articles designed for processing with heat, such as in articles containing an oxidation-; reduction image-forming combination with a photosensitive metal salt such as a silver salt as described in Sheppard et al. U.S. Pat. No. 1,976,302 issued Oct. 9,
1934; Sorensen et al. US. Pat. No. 3,152,904 issued Oct. 13, 1964 and Morgan et al. US. Pat. No
3,457,075 issued July 22, 1969.
It is, of course, recognized that the photographic article formed according to this invention can, if desired,
incorporate anti-static or conducting layers other than I or in addition to adhesive anti-static subbing. layers of this invention. Such layers can comprise soluble salts,
tional 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 an article 1 comprising a dielectric support 3, such as a hydrophobic polymer support. A hydrophilic colloid coating 5 is located over the support and is adhesively bonded thereto by adhesive antistatic layer 7 according to this invention.
FIG. 2 illustrates a photographic article 10 in which a dielectric support 12 is provided with a dielectric hydrophobic polymer layer 14 adjacent one major surface. A radiation-sensitive hydrophilic colloid coating 16 containing radiation-sensitive material is adhesively bonded to the hydrophobic polymer layer by adhesive anti-static subbing layer 18.
H6. 3 illustrates a photographic article 100 in which a dielectric support 102 is provided with a dielectric hydrophobic polymer layer 104 adjacent one major surface. An adhesive anti-static subbing layer 106 bonds a radiation-sensitive portion 108 of the article to the hydrophobic polymer surface presented by the layer 104. The radiation-sensitive portion 108 is comprised of a hydrophilic colloid layer 110, which is as coated substantiallyfree of radiation-sensitive materials, and a radiation-sensitive emulsion layer 112, which overlies the layer 110.
For further illustrate the invention the following examples are included:
EXAMPLE 1 In a specific illustration of this invention a subbing layer formed of an intimate intermixture of chromium and silicon monoxide is produced on a polyethylene terephthalate film support which may be utilized without any surface treatment or with a conventional subbing layer formed of a terpolymer of acrylonitrile, vinylidene chloride and acrylic acid. Deposition of the subbing layer is accomplished utilizing a vacuum system in which a length of the film about 5 inches wide With the support in place on the drive rolls and with the chromium and silicon monoxide cermet present as a powder in the crucible the vacuum chamber in which the support and crucible are located is pumped down to 2.3 X 10 Torr. and the cermet is heated by sweeping an electron beam over the surface of the powder. When a sufficiently high temperature is reached for the cermet to sublime readily, the shutter is opened and the support coated to the desired thickness as is determined using a conventional quartz crystal thickness monitor.
Laterally spaced successive layers of intimately intermixed chronium and silicon monoxide layers varying in thickness from 30 to 150 angstroms are deposited on the support. Upon removal from the vacuum system the optical density and surface resistivity of the layers formed on the support are measured, and the metalmetal oxide subbing layers are subjected to an accelerated keeping test in which they are stored under conditions of percent relative humidity at 50C. The results of the keeping tests on several different layers are shown in Table I. The optical densities are in each instance net optical densities and are determined using an optical densitometer as the difference between the optical densities of otherwise identical coated and uncoated supports. The surface resistivities are determined by placing electrodes on the coated surface of the support in parallel relation and separated by a spacing equal to their length. The surface resistivity can then be read directly in ohms as the resistance separating the electrodes.
In addition to having excellent stability on storage, the chromium and silicon monoxide layers are unaffected when bathed in common photographic processing solutions, such as aqueous alkaline developing solutions and aqueous acid fixing and stop baths. The low electrical surface resistivity of the coatings provides excellent anti-static protection to the supports.
Table 1 After 12 Weeks Storage Fresh Resis- Layer Surface Treatment Optical Resistivity Optical tivity Composmon of Support Density (ohms/sq) Density (ohms/sq) 70% Cr- None O.l0 3500 0.09 2. 3074 SiO 7 X 10 50% Cr- None 0.09 l.7 X lo 0.09 3.5 X 10 50% SiO 50% Cr- None 0.25 2800 0.25 4200 50% SiO 58g: terpolymer 0.13 3000 0.11 1.5x 10- 28; terpolymer 0.15 1.2 X10 0.13 X104 is taped to form a loop and fitted over a set of drive EXAMPLE 2 rolls. A chromium and silicon monoxide cermet is placed in a crucible a distance of 12 inches below the lower surface of the support for electron beam heating 60 to produce a vapor source. Between the crucible and the surface of the support a mask is provided to limit access of the vapor to the support surface, and a shutter is provided in the mask to allow selective areal access of the vapor to the support. The support loop is transported by the drive rolls to allow successive layer thicknesses resulting from varied shutter opening times to be deposited at different locations on the support.
Utilizing the same vacuum system as described in Example l a number of layers of intimately intermixed chromium and silicon monoxide are deposited on a terpolymer treated polyethylene terephthtalate support of the type described in Example 1 using as a vapor source a- 1:1 weight ratio of chromium and silicon monoxide. With the source heated in the electron beam to a point where it is subliming at a high rate, the shutter protection for the support is opened and the support is drawn past the shutter opening at rate such that the chromium and silicon monoxide layer condensing on the support forms a layer thickness of approximately 70 angstroms thick.
Using the same general procedures layers of nickel and chromium of 25 angstroms thickness are separately deposited on similar supports. Samples of the layers when submitted to accelerated keeping test in which they are stored under conditions of 50 percent relative humidity at 50C. yield results as shown in Table II.
Table II After 14 Weeks Fresh Storage Composition Optical Resistivity Optical Resistivity of Layer Density (ohms/sq) Density (ohms/sq) 50%SCr-50% 0.10 1.4 X 10" 0.09 2.2 X 10 i 50%SC650% 0.05 3.3 X 10 0.04 1.8 X
l Chromium 0.12 9.6 X 10 0.09 2.2 X 10 Nickel 0.12 840 0.05 1 X 10 EXAMPLE 3 Gold electrodes are deposited on a glass support by deposition in vacuum and then an intermixed chromium and silicon monoxide is deposited on the support as described in Example 1. The layer exhibits an optical density of 0.22 when exposed to air for 5 minutes. Electrical connections are made to the electrodes, and the sample is placed in a vacuum system which is pumped to a pressure of 1.0 X 10 Torr. The film is first sintered at 200C. by heating the substrate and then resistance meausrements are made at various temperatures. In a similar manner a nickel film having an optical density of 0.13 is prepared and resistance measurements made. The results are given in Table II].
Table III Chromium-silicon Monoxide Layer Nickel Temp., C. Resistivity, ohms/sq Resistivity, ohms/sq 23 1.1 X 10 1.3 X10 100 9.3 X 10 1.3 X10 150 8.9 X 10 L4 X10 200 7.9 X 10 1.4 X 10 The chromium and silicon monoxide layer exhibits a negative temperature coefficient of resistance which suggests that its mode of electrical current conduction is more analogous to that of semiconductive materials than to metals. This indicates that there is no continuous metal structure in the film coating and that the chromium particles are at least partially encapsulated by the silicon oxide. The factor contributes to the exceptional stability of the film when stored.
EXAMPLE 4 A number of anti-blocking coatings are made on rolls of polyethylene terephthalate support in the following manner: A roll is loaded into a conventional vacuum roll coater, and an anti-blocking glass to be deposited, such as a borosilicate glass, e.g., Code 8,329 glass (manufactured by Jena Glaswerk Schott and Gen.,
Mainz, West Germany) is placed in the crucible of an electron beam heated vapor source. The vacuum chamber is closed and pumped down to a pressure of 7.2 X 10' Torr. The glass is heated in an elelctron beam until it is evaporating at a high rate. Shutters protecting the support from the vapor are opened and the support is drawn through the vapor beam at a rate such posite the glass coating. The anti-blocking glass is, of
course, unnecessary for molecularly intermixed subbing layers according to this invention, since they are notably free of any blocking tendency, but the antiblocking glass is provided on all supports to assure direct comparability of characteristics.
To the surface of the supportrolls opposite the glass 1 anti-blocking coatings are deposited anti-static layers by the. same procedures. A layer formed of intermixed chromium and silicon monoxide is deposited using a l:1 weight ratio of chromium and silicon monoxide cermet. For purposes of comparison layers of nickel and aluminum are also deposited. The thicknesses and opti cal densities of the supports with the metal and intermixed metal and methal oxide layers is set forth below in Table IV.
Table IV Layer Composition Thickness Optical Density Nickel 40A 0.21 Aluminum A 0.41 Chromium-Silicon monoxide A 0.15
The superiorly low optical density of the chromium and silicon monoxide intermixture is readily apparent.
The coatings are stored in rolls for 2 weeks under ambient conditions and then overcoated on a conventional emulsion coating machine with a silver bromoiodide photographic emulsion at a coverage of 400 mg. of silver/ft? In addition to the support bearing layers as set forth in Table IV, supports of untreated polyethylw ene terephthalate and polyethylene terephthalate coated with a conventional subbing layer for emulsion adhesion comprised of a terpolymer of methyl acrylate, vinylidene chloride and acrylic acid are also overcoated with the photographic emulsion.
The dry, unprocessed photographic emulsion adheres very poorly to the unsubbed support and will flake off if the support is flexed or twisted. This effect does not appear on any of the articles which are provided with a layer interposed between the support and the photographic emulsion coating. This indicates that prior to processing each of the interposed layers to some extent improves the bond between the support and the emulsion.
- To illustrate the effects of photographic processing on the adhesion of the emulsion coatings to the supports like sized strips of each coated support are developed in a buffered aqueous developing solution having a pH of approximately and incorporating equal parts by weight p-methyl aminophenol and hydroquinone for 2 minutes at 23C., followed by 3 minutes fixation in a sodium thiosulfate containing aqueous fixing bath, the developing solution and the fixing bath being commercially available as Kodak Developer DK-60a and Kodak Fixing Bath F-S, respectively. The strips are subsequently washed in running water for 30 minutes at C. Upon evaluation after processing but before drying the emulsion is noted to adhere to all but the one support to which the emulsion coating is directly applied. In those articles incorporating nickel and aluminum as the interposed layer some frilling occurs along the edges of the support, whereas with the conventional terpolymer layer and the intermixed chromium and silicon monoxide layer no frilling occurs and the swollen emulsion adheres firmly to the support.
EXAMPLE 5 In order to further compare the adherency of the emulsion coatings to the supports several photographic articles are prepared as described above in Example 4 and, additionally, an article is similarly prepared incorporating a borosilicate glass layer as described above in Example 4 between the emulsion coating and support. In the first test the emulsion coating is scribed to the support with an 0.1 mm. stylus and the article is processed under conditions of high agitation. The amount of peeling from the scribed mark is taken as a relative measure of adhesion. In the second test a 1-inch circle of the emulsion coating is submitted to a wash cycle at 71C. and dried. Thereafter the percent peel from the sample is measured. The layer compositions are compared and their performance set forth in Table V.
From the foregoing it is apparent that the aluminum 'layer is totally ineffective to bond the emulsion coating to the support under the oxidizing conditions presented and it is not to be expected that other oxidizable metal layers would behave in a significantly different manner. The glass layer, while adhering less well than the conventional terpolymer subbing layer, is nevertheless significantly better than the metal layer and is capable of providing acceptable adhesion of the emulsion coating to the support. The intermixed metal and metal oxide layer provides a very stable adhesion of the emulsion coating to the support which, in terms of mm. of peel, is superior to the adherency provided by the conventional terpolymer subbing layer.
When other metals of an oxidizable nature, such as silver, nickel, and copper, are substituted for chromium similarly improved adherency and anti-static characteristics are achieved, although the most invariant surface resistivities are achieved using chromium. Other vapor depositable metal oxides, such as silica, alumina, magnesia, titania and tantalum oxide, are also capable of protecting the intermixed metals against oxidation with the same degree of effectiveness as silicon monoxide, although the silicon oxides are preferred because of their lower vapor deposition temperatures. With vapor codeposited interrnixtures of the above enumerated metals and metal oxides high levels of adherency, oxidation resistance, anti-static properties are obtained together with low surface resistivities for given levels of optical density.
The invention has been described in detail with particular reference to preferred embodiments thereof, but, it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
What is claimed is:
1. In a photographic article comprising a radiation sensitive material, a dielectric hydrophobic polymer support, a hydrophilic colloid coating and an adhesive hydrophilic subbing layer which is contiguous to said support and said hydrophilic colloid coating and is bonded to each, the improvement in which said adhesive subbing layer is additionally an anti-static layer exhibiting a surface resistivity of less than 10 ohms per square and is binderless and consists essentially of an intimate blend of a. a metal electrical conductor capable of oxidation to a less conductive state and at least about 20 weight, based on the weight of said blend of b. a protective inorganic oxide selected from the group consisting of silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, titanium oxide, boro-silicon oxide and mixtures thereof; the thickness of said adhesive subbing layer being from about 50 to about 500 angstroms.
2. In a photograpic article comprising a radiationsensitive material, a dielectric hydrophobic polymer support, a hydrophilic gelatin coating and an adhesive hydrophilic subbing layer which is contiguous to said support and said hydrophilic gelatin coating and is bonded to each, the improvement in which said adhesive subbing layer is additionally an anti-static layer exhibiting a surface resistivity of less than 10 ohms per square and is binderless and consists essentially of an intimate blend of a. a metal electrical conductor capable of oxidation to a less conductive state, and at least about 20 weight, based on the weight of said blend of b. a protective inorganic oxide selected from the group consisting of silicon oxide, magnesium oxide, aluminum oxide, tantalum oxide, titanium oxide, boro-silicon oxide and mixtures thereof; the thickness of said anti-static layer being from about 50 to about 500 angstroms.
3. In a photographic article according to claim 2, said protective inorganic oxide consisting essentially of silicon monoxide.
4. In a photographic article according to claim 2, said subbing layer consisting essentially of a mixture of chromium and silicon oxide.
5. In a photographic article according to claim 2,'said support being polyethylene terephthalate.
6. In a photographic article according to claim 2, said radiation-sensitive material being a silver halide.
7. In a photographic article according to claim 2, said support being polyethylene terephthalate, said radiation-sensitive material being a silver halide and said subbing layer consisting essentially of silicon oxide and chromium.
8. In a photographic article according to claim 7, said silver halide being silver bromochloride.
9. In a photographic article comprising a dielectric hydrophobic polymer support, a first hydrophilic gelatin coating, a second hydrophilic gelatin coating bonded to said first hydrophilic gelatin coating and containing a radiation-sensitive silver halide, and an adhesive hydrophilic subbing layer which is contiguous to said support and said first hydrophilic gelatin coating and is bonded to each, the improvement in which said adhesive subbing layer is additionally an anti-static layer exhibiting a surface resistivity of less than 10 ohms per square, is substantially transparent and consists essentially of an intimate blend of a. a vapor deposited electrically conductive metal capable of oxidation to a less conductive state and thickness of said anti-static layer being from about 50 to about 500 angstroms. 10. In a photographic article according to claim 9,
said electrically conductive metal consisting essentially of chromium.
11. In a photographic article according to claim 9,
said subbing layer consisting essentially of a mixture of chromium and silicon monoxide.
12. In a photographic article according to claim 9, said subbing layer consisting essentially of from 80 to 30 percent by weight chromium and from 20 to per- 9 cent by weight an oxide of silicon monoxide.
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