ARTICLE WITH OXIDATION PROTECTED

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ARTICLE WITH OXIDATION PROTECTED layers in conjunction with vapor deposited overlayers

ADHESIVE AND ANTI-STATIC LAYER to provide anti-static properties to certain siliceous surfaces.

This invention relates to improving the adhesion of a Prior to this invention there has been no recognition hydrophilic colloid coating to a dielectric support while 5 in the art that metal-inorganic oxide layers are compatprotecting the resulting article from static electrical ible with the demanding requirements of photographic discharge. In one aspect, this invention relates to an ar- use and processing environments. Further, while vapor tide having a hydrophilic colloid coating and a dielec- deposited overlayers have been associated with metaltrie support which are bonded together by an inter- inorganic oxide layers, such overlayers differ markedly posed conductive adhesive layer having a surface resis- 10 in physical properties from hydrophilic colloids. Hytivity sufficiently low to allow the lateral conduction of drophilic colloid coatings are neither dimensionally staelectrical charge. In another aspect, this invention re- ble nor are they protective in aqueous solutions. For lates to a photographic article containing a radiation- example, hydrophilic colloids ingest water when sensitive material in which a hydrophilic colloid coat- brought into contact with aqueous solutions, such as ing is bonded to a dielectric support by an interposed 15 photographic processing solutions. The ingestion of adhesive and anti-static subbing layer. water creates substantial dimensional changes and/or Prior to this invention it has been recognized that in large internal stresses in the hydrophilic colloid, particphotographic structures incorporating a photosensitive ularly at a bonding surface. Typically, a hydrophilic emulsion coating on a dielectric support the accumula- colloid coating may ingest a quantity of water several tion of static charge on the support can have the unde- 20 times its original weight leading to doubling, tripling or sirable effect when accidentally discharge of fogging greater increase in its original thickness. When a hydrothe emulsion coating in the vicinity of the discharge. philic colloid is deposited directly on a support, such as Static charge accumulation is particularly troublesome a film support, it can be sloughed from the support on in roll films not containing gel pelloid layers or paper swelling of the layer during exposure to aqueous soluinterleavers, as is frequently the case in film applica- 25 tions. Accordingly, the art has heretofore generally utitions requiring minimal weight and/or rapid processing. lized subbing layers to facilitate adhesion of hydroOne approach that has been suggested in the art for philic colloid coatings to support surfaces. Since the dissipating or controlling static electrical charges on hydrophilic colloid coatings must inherently be permedielectric photographic supports involves the utiliza- able to aqueous solutions in order to allow phototion of a thin metal coating having sufficient conductiv- 30 graphic processing solutions to reach the radiationity to prevent high, localized static charge accumula- sensitive materials and addenda dispersed in the coition. The principal disadvantages associated with me- loid, the subbing layer is, of course, brought into direct tallic anti-static coatings are that when they are depos- contact with the processing solutions and must be resisited in thin films of less than about a 100 angstroms tant to attack thereby if the colloid is to remain bonded they become oxidixed during storage in association 35 to the support.

with the photographic emulsion coatings, so that their It is an object of this invention to provide an article conductances progressively decline and, hence, their having an adhesive anti-static subbing layer for bonding antistatic properties deteriorate. If the metal coatings a hydrophilic colloid coating to a dielectric support, are applied in sufficient thicknesses to offset their de- particularly a hydrophobic support, clining conductivities in the photographic environ- ^ It is still another object to provide a photographic arment, the increased thicknesses produce undesirable tide containing a radiation-sensitive material having a increases in optical density. In either instance the metal hydrophilic colloid coating bonded to a dielectric supanti-static coating can interact with the photosensitive port by an interposed subbing layer which is an antiemulsion coating to produce undesirable fogging. Fur- static layer and which is relatively inert and insoluble ther, the metal coating may inhibit bonding of a photo- in the course of photographic processing and also that graphic emulsion to the support, so that metal anti- is compatible with radiation-sensitive materials and adstatic coatings are typically placed on the support sur- denda.

face opposite to that of the photographic emulsion It is a further object to provide an article incorporat

coating. A further disadvantage is that when a support ing a subbing layer that is resistant to blocking,

having a freshly deposited metal anti-static layer These and other objects of the invention are accom

thereon is wound in reel form, the metal frequently will plished in one aspect by providing an article comprising

adhere to both adjacent surfaces. When this occurs the a dielectric support, a hydrophilic colloid coating and

metal may cause "blocking" — i.e., prevent unwinding a subbing layer which is contiguous to the support and

of the reel or, if unwinding is in fact accomplished, the 55 the hydrophilic colloid coating and is bonded to each,

metal coating may be partially and randomly trans- The subbing layer exhibits a surface resistivity of less

ferred to the opposite surface of the support. than 1012 ohms per square and is comprised of an elec

Prior to this invention it has been recognized that trical conductor capable of oxidation to a less conduc

vapor codeposited metal inorganic oxide layers are tive state and a protective inorganic oxide intimately

readily adherent to siliceous surfaces, such as glass, and 6Q intermixed with the electrical conductor in a concen

may be used to impart anti-static properties to glass tration sufficient to retard oxidation of the electrical

surfaces, such as windows, lenses, windshields and the conductor.

like. It has been recognized that these metal inorganic In accordance with this invention, it has been found

oxide layers may in turn receive vapor deposited over- that a hydrophilic colloid coating can be firmly bonded

layers, such as vapor deposited metal oxide, metal hal- ^ to a dielectric support surface by means of an adhesive

ide and metal overlayers. For example, Colbert et al. anti-static layer which is contiguous to the supporting

U.S. Pat. No. 2,808,351, issued Oct. 1, 1957, teaches surface and to the hydrophilic colloid. The adhesive an

using certain vapor codeposited metal-inorganic oxide ti-static layer is a binderless layer which consists essen3 4

tially of an electrical conductor and a protective inor- urement taken for the special case in which electrode

ganic oxide. The term "binderless layer" refers to a length and spacing are identical and therefore mutually

layer that is substantially free of organic adhesive mate- canceling parameters.

rials and refers particularly to the absence of those or- It is a significant feature of this invention that the ganic adhesive and binder materials commonly utilized 5 electrical conductor, typically a metal, incorporated in in the photographic arts, such as natural and synthetic the subbing layer need not itself be resistant to oxidapolymeric binders and colloidal vehicles. The adhesive tion in the photographic environment in which it is layer performs the functions both of a conventional an- used. That is, it is noted that metals employed accordti-static layer and a conventional subbing layer and may ing to this invention in combination with inorganic oxbe used in combination with either or both, but is pref- 10 ides are protected against excessive oxidation in use erably substituted for conventional antistatic and sub- even where layers formed entirely by like quantities of bing layers. the same metals have been observed to be highly oxi

It is a surprising feature of this invention that the anti- dized. The metals that are generally preferred are those static subbing layers exhibit conductivity characteris- yielding a low level of optical density for a given resistics of improved stability when incorporated into arti- 15 tance value. Chromium is observed to be outstandingly cles, particularly photographic articles, to adhesively suited to the practice of this invention because of its bond a hydrophilic colloid coating to a support. It is low optical densities at given levels of layer conductivalso surprising that the hydrophilic colloid coating re- ity and because of its exceptional resistance to oxidamains tenaciously bonded by the subbing layer of this tion when utilized in combination with a protective ininvention to the support surface when the support sur- 20 organic oxide. Other metals that are noted to be highly face is hydrophobic, when the article is immersed in useful in the practice of this invention are silver, copper colloid swelling aqueous solutions and when the article and nickel. Still other metals which are not objectionis subjected to mechanical flexure of the support and ably reactive with the dielectric support, hydrophilic colloid. In the course of processing after exposure, pho- colloid coating and the radiation-sensitive materials tographic articles bearing photosensitive emulsion 25 and addenda which are present in photographic applicoatings are often brought into association with alka- cations can be used, depending upon the specific paline, acid and/or neutral aqueous solutions in accor- rameters, such as initial cost, optical density, conducdance with procedures well known to those skilled in tance, short and long term oxidation resistance, etc., the art. In the course of such processing the emulsion that may be operative for any particular application, coating, being water permeable, ingests appreciable 30 The inorganic oxide component of the subbing layer quantities of aqueous solution, and the increase in vol- functions to protect the metal against oxidation. Typiume of the emulsion coating can produce marked di- cally inorganic oxides are dielectric materials, and it is mensional changes and/or internal stresses. Despite a surprising feature of this invention that they are capasuch changes and stresses the subbing layer utilized in ble of protecting the metal without increasing the electhe practice of this invention remains comparatively ^5 trical resistance of the subbing layer beyond useful anstable during such photographic processing. Further- ti-static levels. The protective inorganic oxides are more, the subbing layer is also quite adherent even characteristically water insoluble and substantially when subjected to mechanical stress, as. for example, chemically inert toward common photograhpic prowhen binding a colloid coating to a flexible support that cessing solutions as well as toward photographic emulis wound or repeatedly flexed. 40 sion coatings. Preferred metal oxides are those which

The subbing layer exhibits a surface resistivity of less exhibit a low level of optical density and, most preferathan 1012 ohms per square, this being generally recog- bly, are substantially transparent. Oxides of silicon, nized as the maximum surface resistivity permissible if such as silicon monoxide and silicon dioxide, are precharge is to be conducted from a support. In photo- ferred oxides for the practice of this invention, since graphic applications it is generally preferred that the they are substantially water insoluble and chemically layer exhibit a surface resistivity of less than 108 ohms inert in photographic processing and use environments, per square. In order to insure that in all localized areas and are essentially transparent. Silicon oxides are also a surface resistivity of less than 10" ohms per square is preferred, since they can be vapor codeposited with attained it is preferred that the subbing layer have an metals by heating to vaporization temperatures that are overall surface resistivity of less than 105 ohms per low as compared to those required for vaporizing other square. With anti-static layers having overall surface protective oxides. Metal oxides such as aluminum oxresistivity of less than 105 ohms per square it has been ide, magnesium oxide, tantalum oxide, boro-silicon observed that photographic reproductions can be uni- oxide (e.g., borosilicate) and titanium oxide are also formly and reliably obtained with no evidence of opti- 55 recognized to be particularly suited to the practice of cal alterations attributable to localized discharge of this invention. The protective oxides are usable in both static electrical charge. As is well understood by those crystalline and amorphous forms. It is specifically conskilled in the art, surface resistivity is determined by templated that glasses may be utilized, particularly measuring the resistance between two parallel elec- glass forming mixtures of oxides. The use of crystalline trades of a given length spaced apart by the same dis- 6Q mineral mixed oxides is also contemplated, tance along a surface. Since an increase in the length The unexpected combination of conductance and oxof the electrodes tends to decrease the resistance ob- idation resistance properties observed in the subbing served by an amount equal to that by which the resis- layer are attributable to the intimate intermixture of tance would be increased by lengthening the spacing the metal and protective inorganic oxide. While various between the electrodes by a like increment, it is appar- ^ techniques are known that may be employed to achieve ent that the electrode length and spacing is not material an intermixture of metal and protective inorganic oxso long as they are identical, hence, the surface resistiv- ide, it is preferred that the mixture be formed by vacity expressed in ohms per square is a resistance meas- uum codeposition of metal and protective inorganic