Imaging element comprising an electrically-conductive layer containing intercalated vanadium oxide

CROSS REFERENCE TO RELATED APPLICATIONS
Reference is made to concurrently filed, commonly assigned, copending U.S. Ser. No. 09/161,881, entitled "Colloidal Vanadium Oxide Having Improved Stability", and U.S. Ser. No. 09/162,182, entitled "Imaging Element Comprising an Electrically-Conductive Layer Containing Intercalated Vanadium Oxide and a Transparent Magnetic Recording Layer", the disclosures of which are incorporated by reference in their entireties.
FIELD OF THE INVENTION
This invention relates generally to imaging elements comprising a support, one or more image-forming layers, and at least one transparent, electrically-conductive layer. More specifically, this invention relates to photographic and thermally-processable imaging elements comprising one or more sensitized silver halide emulsion layers and one or more electrically-conductive layers, the conductive layers containing colloidal vanadium oxide intercalated with a water-soluble vinyl-containing polymer.
BACKGROUND OF THE INVENTION
Problems associated with the generation and discharge of electrostatic charge during the manufacture and use of photographic film and paper products have been recognized for many years by the photographic industry. The accumulation of charge on film or paper surfaces can cause difficulties in support conveyance, as well as lead to attraction of dust, which can produce fog, desensitization, repellency spots and other physical defects. The discharge of accumulated static charge during or after the application of sensitized emulsion layer(s) can produce irregular fog patterns or "static marks". The severity of static problems has been exacerbated greatly by increases in sensitivity of new emulsions, coating machine speeds, and post-coating drying efficiency. The charge generated during the coating process results primarily from the tendency of high dielectric constant polymeric film base webs to undergo triboelectric charging during winding and unwinding operations, during transport through coating machines, and during post-coating operations such as slitting, perforating and spooling. Static charge can also be generated during the use of the finished photographic product. In an automatic camera, the repeated winding and unwinding of the photographic film in and out of the film cassette can result in generation of electrostatic charge, especially in a low relative humidity environment. The accumulation of charge on the film surface results in the attraction and adhesion of dust to the film and can even produce static marking. Similarly, high-speed automated film processing equipment can produce static that produces marking. Sheet films are especially subject to static charging during use in automated high-speed film cassette loaders (e.g., x-ray films, graphic arts films, etc.)
In order to eliminate problems arising from electrostatic charging, there are various well known methods by which an electrically-conductive antistatic layer can be introduced into the photographic element to dissipate accumulated static charge, for example, as a subbing layer, an intermediate layer, as an outermost layer overlying a silver halide emulsion layer, as a backing layer on the opposite side of the support from the silver halide emulsion layer(s) or on both sides of the support. A wide variety of conductive antistatic agents can be used in antistatic layers to produce a broad range of electrical conductivities. Many of the traditional antistatic layers used in photographic elements employ materials which exhibit predominantly ionic conductivity. Antistatic layers containing simple inorganic salts, alkali metal salts of surfactants, alkali metal ion-stabilized colloidal metal oxide sols, ionic conductive polymers or polymeric electrolytes containing alkali metal salts and the like have been taught in prior art. The electrical conductivities of such ionic conductors are typically strongly dependent on the temperature and relative humidity of the surrounding environment. At low relative humidities and temperatures, the diffusional mobilities of the charge carrying ions are greatly reduced and the bulk conductivity is substantially decreased. Further, at high relative humidities, an unprotected antistatic backing layer containing such an ionic conducting material can absorb water, swell, and soften. Especially in the case of roll films, this can result in the adhesion (viz., ferrotyping) and even physical transfer of portions of a backing layer to a surface layer on the emulsion side of the film (viz., blocking).
Antistatic layers containing electronic conductors such as conjugated conductive polymers, conductive carbon particles, crystalline semiconductor particles, amorphous semiconductive fibrils, and continuous semiconductive thin films or networks can be used more effectively than ionic conductors to dissipate charge because their electrical conductivity is independent of relative humidity and only slightly influenced by ambient temperature. Of the various types of electronic conductors disclosed in prior art, electronically-conductive metal-containing particles, such as semiconductive metal oxides, are particularly effective when dispersed with suitable polymeric binders. Binary metal oxides doped with appropriate donor heteroatoms or containing oxygen deficiencies have been disclosed in prior art to be useful in antistatic layers for photographic elements, for example: U.S. Pat. Nos. 4,275,103; 4,416,963; 4,495,276; 4,394,441; 4,418,141; 4,431,764; 4,495,276; 4,571,361; 4,999,276; 5,122,445; 5,294,525; 5,382,494; 5,459,021; and others. Suitable claimed conductive metal oxides include: zinc oxide, titania, tin oxide, alumina, indium oxide, silica, magnesia, zirconia, barium oxide, molybdenum trioxide, tungsten trioxide, and vanadium pentoxide. Preferred doped conductive metal oxide granular particles include Sb-doped tin oxide, Al-doped zinc oxide, and Nb-doped titania. Additional preferred conductive ternary metal oxides disclosed in U.S. Pat. No. 5,368,995 include zinc antimonate and indium antimonate. Other suitable electrically-conductive metal-containing granular particles including metal borides, carbides, nitrides, and silicides have been disclosed in Japanese Kokai No. 04-055,492.
Antistatic backing or subbing layers containing colloidal "amorphous" vanadium pentoxide, especially silver-doped vanadium pentoxide, are described in U.S. Pat. Nos. 4,203,769 and 5,439,785 and others. Colloidal vanadium pentoxide is composed of entangled microscopic fibrils or ribbons 0.005-0.01 .mu.m wide, about 0.001 .mu.m thick, and 0.1-1 .mu.m in length. However, colloidal vanadium pentoxide is soluble at the high pH typical of developer solutions for wet photographic processing and must be protected by a nonpermeable, barrier layer. Examples of suitable barrier layers are taught in U.S. Pat. Nos. 5,006,451; 5,221,598; 5,284,714; and 5,366,855, for example.
In order to improve the durability of the antistatic layer and adhesion to underlying or overlying layers it is generally preferred to disperse the colloidal vanadium pentoxide in a polymeric film-forming binder. However, due to the solution chemistry and oxidative potential of vanadium oxide, the selection of compatible binders is limited. For example, for low coating coverages the vanadium pentoxide may typically be coated at 0.05 wt. % or less. At such low concentrations the vanadium pentoxide is prone to instability and flocculation. Depolymerization of vanadium pentoxide gel may also occur at low concentrations or low pH values. A film-forming sulfopolyester latex or polyesterionomer binder can be combined with colloidal vanadium pentoxide in the conductive layer for improved solution stability and to minimize degradation during processing as taught in U.S. Pat. Nos. 5,360,706; 5,380,584; 5,427,835; 5,576,163; and others.
U.S. Pat. No. 5,439,785 teaches the use of a specified ratio of sulfopolymer to vanadium oxide to provide an antistatic formulation which remains conductive after photographic processing. A weight ratio range of from 1:20 to 1:150 V.sub.2 O.sub.5 :sulfopolymer is specified. Surface electrical resistivity values are typically greater than 1.times.10.sup.9 ohm/square for the indicated range. At lower colloidal vanadium oxide concentrations, the conductivity is insufficient to provide antistatic protection; at higher vanadium oxide concentrations the antistatic layer loses conductivity when subjected to photographic processing. However, prior art colloidal vanadium pentoxide typically have significantly lower resistivity values, i.e., 1.times.10.sup.8 ohm/square. Consequently, one of the primary benefits of colloidal vanadium oxide, low resistivity at low dry weight coverage is not achieved.
U.S. Pat. No. 5,718,995 teaches an antistatic layer containing colloidal vanadium oxide and a specified polyurethane binder having excellent adhesion to surface treated polyester supports and an overlying transparent magnetic layer. However, it is further disclosed that the coating composition has limited shelf-life (less then 48 hrs). In order to overcome the limited shelf life, a mixed melt process was preferably used in which separate solutions of colloidal vanadium pentoxide and of the polyurethane binder were prepared and mixed in-line just prior to the coating hopper. This results in an undesirable complication of the coating process. It is further disclosed in '995 that it is difficult to achieve adequate adhesion to glow discharge treated polyethylene naphthalate for a magnetics backing package consisting of a solvent coated cellulosic-based magnetic layer overlying an antistatic layer containing colloidal vanadium pentoxide and the preferred sulfopolyesters or interpolymers of vinylidene chloride cited in the above mentioned U.S. Patents.
In addition to the aqueous-based coating compositions described above it may be advantageous to coat antistatic layers from solvent-based formulations. U.S. Pat. No. 5,709,984 describes antistatic layers containing colloidal vanadium oxide gel, a volatile aromatic compound, and a polymeric binder prepared from a solvent-based dispersion using acetone and ethanol. Polymeric binders demonstrated include interpolymers of vinylidene chloride, polymethylmethacrylate, cellulose nitrate and cellulose diacetate. It is further disclosed that due to the exceptional adhesion requirements of antistatic layers containing colloidal vanadium oxide, such layers generally exhibit poor adhesion when directly coated on untreated or unsubbed polyester supports.
U.S. Pat. No. 5,356,468 teaches the use of cellulose nitrate as a binder or co-binder which imparts improved solution stability for solvent based coating formulations. The addition of cellulose nitrate to a formulation of vanadium oxide gel in a solvent mixture of acetone, alcohol and water resulted in improved resistance to precipitation when exposed to cellulose triacetate film supports.
U.S. Pat. No. 5,366,544 teaches the use of cellulose acetate having an acetyl content of from 15 to 35 weight percent as a binder for vanadium pentoxide. It is further disclosed to use a solvent mixture consisting of dialkyl ketone, an alkanol, and water.
U.S. Pat. No. 5,455,153 describes photographic elements containing a clad vanadium pentoxide layer. The cladding layer is formed by applying an overcoat of an oxidatively polymerizable compound which may be applied neat to the vanadium oxide or in the form of an aqueous solution, a solvent solution or as a vapor. Suitable oxidatively polymerizable monomers include anilines, pyrroles, thiophenes, furans, selenophenes and tellurophenes. Antistatic layers containing clad vanadium oxide were demonstrated to have improved resistance to basic solutions as typically encountered during conventional photographic processing. Improved base resistance results from cladding the surface of vanadium pentoxide rather than a change resulting from polymer intercalation between vanadium oxide layers.
Intercalation of various species, including cations, metal-containing complexes, organic molecules and polymers, within vanadium oxide is well-known, particularly in the catalysis field and as cathode materials for batteries. However, intercalated colloidal vanadium oxide for antistatic applications has not typically been addressed.
U.S. Pat. No. 5,659,034 describes intercalation of metal coordination complexes, particularly Zn(2,2'-dipyridyl).sub.2, between layers of vanadium oxide. The resultant intercalated vanadium oxide was described as black rod-shaped crystals which are unsuitable for antistatic applications for photographic films.
U.S. Pat. No. 5,073,360 describes the formation of bridged/lamellar metallic oxides having intercalated spheroidal cationic species. The preferred metallic oxide is vanadium pentoxide and the spheroidal cationic species is preferably an aluminum polyoxocation, particularly [Al.sub.13 O.sub.4 (OH).sub.24 ].sub.7.sup.+. The vanadium oxide gel can be prepared for example by ion exchange or melt quenching. The intercalated material is then isolated by filtration, dried and optionally calcined to give high surface area materials which are particularly suited as molecular sieve filters, catalysts, and catalyst supports. However, no indication is given regarding the antistatic properties of the intercalated vanadium oxide.
Intercalation of a wide variety of organic or polymeric materials between vanadium oxide layers in vanadium oxide gels is well known. Intercalative polymerization of aniline resulting in polyaniline is described in Mater. Res. Soc. Symp. Proc. V. 233, pp. 183-194, 1991 and Chem. Mater. V. 8, pp. 1992-2004, 1996. A significant decrease in oxygen concentration and a color change from red to dark blue was observed when vanadium oxide gel was added to an air saturated solution of aniline in water. Conductivity of the polyaniline-vanadium oxide material increased substantially upon aging. It was proposed that conductivity in the fresh material occurred by electron transport through the vanadium oxide framework (semiconductive) but upon aging a metallic-like conductivity dominated as polyaniline chains formed.
Poly(ethylene oxide) intercalated vanadium oxide gels were reported in Chem. Mater, Vol. 3, 992-994, 1991 and Chem. Mater, Vol. 8, 525-534, 1996 to be highly light sensitive, turning dark blue within several weeks for exposure to room light or within several hours for exposure to UV irradiation. Non-intercalated vanadium oxide gels were not light sensitive. In addition to a color change, the conductivity increased and solubility decreased with increasing irradiation. However, the irradiated conductivity decreased with increasing polyethylene oxide intercalation. Changes in the vanadium oxide interlayer distance due to intercalation of poly(vinylpyrrolidone) (PVP), poly(propyleneglycol) (PPG), and methylcellulose are described in Adv. Mater, Vol. 5, 369-372, 1993. Interlayer distance increased linearly for (PVP).sub.x V.sub.2 O.sub.5.nH.sub.2 O for values of x up to 3. Furthermore, a change in the chemical nature of PVP was noted and ascribed to formation of hydrogen bonding with co-intercalated water. The interlayer spacing did not vary linearly with either PPG or methylcellulose. The interlayer distance remained constant for (PPG).sub.x V.sub.2 O.sub.5.nH.sub.2 O with x values greater than 1, and PPG remained chemically unaltered. Particularly in the case of PPG, the samples were light sensitive as indicated above.
The above references indicate a vast array of organic or polymeric species can be intercalated within vanadium oxide gel structures. However, the intercalated material is frequently light sensitive and conductivity changes during aging. Furthermore, intercalation and subsequent reaction frequently decreases solubility of the vanadium oxide gel.
The use of polyvinylpyrrolidone in antistatic formulations is also well known. For example, U.S. Pat. Nos. 4,418,141; 4,495,276; 5,368,995; 5,484,694; 5,453,350; 5,514,528 and others include polyvinylpyrrolidone amongst an extensive list of suitable binders for antistatic materials such as tin oxide or zinc antimonate. There is no specific mention or claim to enhanced properties or stability of polyvinylpyrrolidone or other water soluble vinyl-containing polymers relative to other polymeric binders for the above mentioned patents.
U.S. Pat. No. 4,489,152 describes a diffusion transfer film having an opaque layer consisting of carbon black having 2-10 percent polyvinylpyrrolidone based on the weight of carbon black. The addition of polyvinylpyrrolidone having a molecular weight of about 10,000 to the carbon black layer was found to improve the silver transfer process. However, there was no indication of antistatic properties nor of formulation stability for the carbon black layer.
U.S. Pat. No. 4,860,754 describes an electrically conductive adhesive material consisting of a low molecular weight plasticizer, a high molecular weight water soluble, crosslinkable polymer, uncrosslinked polyvinylpyrrolidone, and an electrolyte. The uncrosslinked polyvinylpyrrolidone is added as a tackifier. Antistatic properties are insufficient for photographic applications since the electrolyte can be removed during wet photographic processing. Furthermore, ionic conductors are generally not effective when overcoated with a hyrdrophobic layer such as a transparent magnetic recording layer.
U.S. Pat. No. 5,637,368 describes the use of colloidal dispersions of vanadium oxide for imparting antistatic properties to adhesive tapes. Polyvinylpyrrolidone and polyvinylpyrrolidone copolymers are included in a list of suitable adhesive compounds. The use of vanadium oxide in the adhesive layer is suggested, but all examples consist of a separate vanadium oxide layer and a separate adhesive layer. In addition polyvinylpyrrolidone was not demonstrated nor disclosed to give superior performance. Furthermore, use of the adhesive material having antistatic properties for use in photographic imaging applications is not suggested.
As disclosed in the above mentioned U.S. Patents several polymers, for example interpolymers of vinylidene chloride, sulfopolyesters, polyesterionomers, and cellulosics have been used as binders for antistatic layers containing colloidal vanadium oxide. However, due to the solution chemistry and oxidative potential of vanadium oxide, the selection of compatible binders and formulation range is limited. For example, for low coating coverages the vanadium pentoxide may typically be coated at 0.05 weight percent or less. Such low concentrations result in coating formulations which are prone to instability and flocculation of the vanadium oxide gel. This creates serious difficulties in accumulation of flocculated vanadium oxide plugging solution delivery lines, filters and coating hoppers. Furthermore, flocculation can result in coating defects or "slugs" which can result in optical and electrical non-uniformities in the coating. The addition of surfactants to the coating solution may stabilize the vanadium oxide gel, however, the typically high levels of surfactant required are undesirable for adhesion and coatability of subsequently applied layers. The concern of stability has been addressed in many of the above patents. Furthermore, interaction between colloidal vanadium oxide and polymeric binders can result in limited dispersion shelf-life. In addition to the potential for incompatibility of binders, it is well known that vanadium pentoxide can act as a reactant or catalyst for decomposition of organic solvents. Decomposition products can adversely impact the coating quality of the antistatic layer and potentially adversely impact the sensitometric performance of photographic emulsions thereby requiring careful selection of coating solvents and binders for the antistatic layer. Furthermore, due to the potential interaction of vanadium pentoxide with solvents and binders, careful consideration must be given to formulation of overlying layers, such as barrier layers and abrasion resistant layers.
Because the requirements for an electrically-conductive layer to be useful in an imaging element are extremely demanding, the art has long sought to develop improved conductive layers exhibiting a balance of the necessary chemical, physical, optical, and electrical properties. As indicated hereinabove, the prior art for providing electrically-conductive layers useful for imaging elements is extensive and a wide variety of suitable electroconductive materials have been disclosed. However, there is still a critical need in the art for improved conductive layers which can be used in a wide variety of imaging elements, which can be manufactured at a reasonable cost, which are resistant to the effects of humidity change, which are durable and abrasion-resistant, which do not exhibit adverse sensitometric or photographic effects, which exhibit acceptable adhesion to overlying or underlying layers, which exhibit suitable cohesion, which have improved solution stability, which have improved binder compatibility, and which have low catalytic or reactant activity. In particular, an improved colloidal vanadium oxide which is compatible with a wider selection of polymeric binders or facilitates the use of higher binder:vanadium oxide ratios to improve adhesion to the support and underlying or overlying layers is desired. It is toward the objective of providing an electrically-conductive layer that more effectively meet the diverse needs of imaging elements, especially those of silver halide photographic films, but also of a wide range of other types of imaging elements, than those of the prior art that the present invention is directed.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the invention, an imaging element is disclosed comprising: (i) a support; (ii) at least one image forming layer; and (iii) an electrically-conductive layer comprising colloidal vanadium oxide intercalated with a water soluble vinyl-containing polymer. The electrically-conductive layer preferably additionally comprises a film-forming binder, which is distinct from the water soluble vinyl-containing polymer. The water soluble vinyl-containing polymer is preferably poly-N-vinylpyrrolidone, polyvinyl alcohol or an interpolymer thereof. It was neither anticipated nor expected that intercalation of vanadium oxide gels with the water-soluble polymeric species of the present invention would result in a vanadium oxide gel having improved solution stability and reduced impact of solution aging on conductivity, which improves manufacturing robustness and enables the use of many polymeric binders which could not be effectively used with conventional vanadium oxide gels in conductive layers of imaging elements.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an imaging element for use in an image-forming process containing a support, at least one image-forming layer, and at least one transparent, electrically-conductive layer. The electrically-conductive layer contains a film forming polymeric binder and colloidal vanadium oxide which is intercalated with a water soluble vinyl-containing polymer. Particular advantages of intercalated vanadium oxide of the present invention are improved solution stability and improved compatibility with a wider selection of polymeric binders or a wider range of binder to colloidal vanadium oxide than is achievable with prior art colloidal vanadium oxide. Furthermore, an increase in polymeric binder to vanadium oxide can improve adhesion to underlying or overlying layers, such as curl-control layers, antihalation layers, abrasion resistant layers, barrier layers and transport control layers. In addition, a wider selection of compatible binders is desired to adequately satisfy the physical, chemical and electrical requirements of various imaging elements containing an antistatic.
Conductive layers in accordance with this invention are broadly applicable to photographic, thermographic, electrothermographic, photothermographic, dielectric recording, dye migration, laser dye-ablation, thermal dye transfer, electrostatographic, electrophotographic imaging elements, and others. Details with respect to the composition and function of this wide variety of imaging elements are provided in U.S. Pat. Nos. 5,719,016 and 5,731,119. Electrically-conductive layers of this invention may be present as backing, subbing, or intermediate layers on either or both sides of the support. The conductive layer can be, e.g., a subbing layer underlying a sensitized silver halide emulsion layer(s) and/or antihalation layer; an intermediate layer inserted between emulsion layers; an intermediate layer either overlying or underlying a pelloid in a multi-element curl control layer, in particular, a backing layer on the side of the support opposite to the emulsion layer(s); a subbing layer underlying an abrasion resistant layer. When the electrically-conductive layer underlies an emulsion layer, pelloid layer or other hydrophilic layer it is preferred to overcoat the antistatic layer with a nonpermeable barrier layer for use in a photographic imaging element. Conductive layers of this invention are strongly adherent to the support and other underlying layers as well as to overlying layers such as pelloid, abrasion-resistant, transport control, or imaging layers. Further, the electrical conductivity afforded by conductive layers of this invention is nearly independent of relative humidity, only slightly degraded when overcoated with a suitable barrier layer and persists nearly unchanged after photographic processing.
Photographic elements that can be provided with electrically-conductive layers in accordance with this invention can differ widely in structure and composition. For example, they can vary greatly with regard to the type of support, the number and composition of the image-forming layers, and the number and types of auxiliary layers that are included in the elements. In particular, photographic elements can be still films, motion picture films, x-ray films, graphic arts films, paper prints or microfiche films, especially CRT-exposed autoreversal and computer output microfiche films. They can be black-and-white elements, color elements adapted for use in a negative-positive process or color elements adapted for use in a reversal process.
Colloidal vanadium oxide is commonly referred to as an "amorphous" gel which is composed of entangled microscopic fibrils, fibers or ribbons 0.005-0.01 .mu.m wide, about 0.001 .mu.m thick, and 0.1-1 .mu.m in length. Colloidal vanadium pentoxide can be prepared by any variety of methods, including, but not specifically limited to melt quenching as described in U.S. Pat. No. 4,203,769, ion exchange as described in DE U.S. Pat. No. 4,125,758, hydrolysis of a vanadium oxoalkoxide as claimed in U.S. Pat. No. 5,407,603, hydrolysis or thermohydrolysis of VOCl.sub.3 or VO.sub.2 OAc, reaction of vanadium or vanadium oxide with hydrogen peroxide or nitric acid, and direct hydrolysis of amorphous or fine-grained vanadium oxide. Melt-quenched vanadium oxide can be prepared by melting vanadium pentoxide or a mixture of vanadium oxide and optional additives, dopants or modifiers generally 100.degree. C. to 500.degree. C. above the melting point and quenching the molten mixture into water. The quenched material is typically aged to form a colloidal gel. Other methods of preparing quenched vanadium oxide include laser melting and splat cooling, for example, Rivoalen describes supercooling a melt on a roll cooled to the temperature of liquid nitrogen in J. Non-Crystalline Solids, 21, 171 (1976). Colloidal vanadium gels can be prepared by hydrolysis with a molar excess of deionized water of vanadium oxoalkoxides, preferably a trialkoxide of the formula VO(OR).sub.3 wherein each R is independently an aliphatic, aryl, heterocyclic or arylalkyl group. Preferably, hydrolysis occurs in the presence of a hydroperoxide such as hydrogen peroxide or t-butyl hydrogen peroxide. Ion exchange of soluble vanadium containing species, such as sodium metavanadate or ammonium metavanadate can be used to prepare colloidal vanadium pentoxide gels. In this process, protons are exchanged for the sodium or ammonium ions resulting in a hydrated gel. Preferred methods of preparing colloidal vanadium pentoxide are the melt-quench technique, detailed in U.S. Pat. No. 4,203,769, and hydrolysis of vanadium alkoxide or oxoalkoxides as taught in U.S. Pat. No. 5,407,603, both incorporated herein by reference with respect to the preparation of such dispersions.
Conductivity of vanadium oxide coatings may be enhanced by controlling the colloidal vanadium oxide morphology and vanadium oxidation state. One method of controlling the morphology and oxidation state is by addition of a dopant or modifier. Another method of controlling the vanadium oxidation state is the use of both V.sup.4+ and V.sup.5+ containing species, for example during the hydrolysis of vanadium oxoalkoxides. In addition to modifying conductivity or morphology, the presence of a metal dopant or modifier can alter the color or dispersability of colloidal vanadium pentoxide. Dopants or modifiers may include vanadium (4+), lithium, sodium, potassium, magnesium, calcium, manganese, copper, zinc, germanium, niobium, molybdenum, silver, tin, antimony, tungsten, bismuth, neodymium, europium, gadolinium, and ytterbium. Preferred metal dopants are calcium, magnesium, molybdenum, tungsten, zinc and silver. The dopant or modifiers may be added in any form suitable for the selected synthetic method. For example, metal oxides, metal phosphates, or metal polyphosphates may be mixed with vanadium pentoxide and melt quenched; metal alkoxides or metal oxoalkoxides may be added to a solution of vanadium oxoalkoxide and hydrolyzed, or a mixture of metal salts with ammonium vanadate or sodium metavanadate may be used for an ion exchange processes. Typically, when present, dopants or modifiers are added at the 0.1-20 mole percent level. An additional method of increasing the conductivity and adhesion of colloidal vanadium oxide coatings is the addition of conductivity-increasing amount of a volatile aromatic compound comprising an aromatic ring substituted with at least one hydroxy group or a hydroxy substituted substituent group as disclosed in U.S. Pat. No. 5,709,984 and incorporated herein by reference with regards to volatile aromatic compounds.
Water-soluble vinyl-containing polymers suitable for intercalation of the vanadium oxide gel include: poly-N-vinylpyrrolidone, polyvinylpyrrolidone interpolymers such as polyvinylpyrrolidone-polyvinylacetate, polyvinyl alcohol, A. polyvinyl alcohol interpolymers such as polyvinyl alcohol-ethylene, polyvinyl methyl ether and the like. Molecular weight of the vinyl-containing polymers may preferably range from about 10,000 to 400,000. Intercalation may be achieved by simply adding a dispersion of a vanadium oxide gel to an aqueous solution of the water soluble polymer. The amount of water soluble vinyl-containing polymer added is such an amount that causes intercalation, but less than that resulting in loss of the fibrous nature of colloidal vanadium oxide. Intercalation is demonstrated by insertion of the polymer between the layers of the colloidal vanadium oxide gel resulting in an increase in basal spacing of the layer by at least 1 .ANG.. Suitable amounts of intercalated polymer can vary depending on the specific water soluble vinyl-containing polymer, the presence of dopant or modifier species, the concentration of colloidal vanadium oxide and the desired conductivity level. However, it is generally preferred to use a molar ratio (based upon monomer units) of intercalating polymer to colloidal vanadium oxide of from 1:4 to 20:1. More preferably, molar ratios of at least 1:2, and most preferably at least 1:1 are used for optimal intercalation. A more preferred upper limit ratio of intercalating polymer to colloidal vanadium oxide is about 5:1, as above such ratio additional polymer may not effectively intercalate. In accordance with specific preferred embodiments of the invention, weight ratios of intercalating polyvinylpyrrolidone polymer to colloidal vanadium oxide of from about 1:2 to 4:1 are used.
In accordance with preferred embodiments of the invention, the use of vanadium oxide gels intercalated with water soluble vinyl-containing polymers allows for the selection of diverse, distinct film-forming binders in electrically-conductive layers, including binders which may not effectively be used with non-intercalated vanadium oxides.
Polymeric film-forming binders useful in conductive layers of the present invention include: water-soluble, hydrophilic polymers such as gelatin, gelatin derivatives, maleic acid anhydride copolymers; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, cellulose acetate butyrate, diacetyl cellulose or triacetyl cellulose; synthetic hydrophilic polymers such as polyvinyl alcohol, poly-N-vinylpyrrolidone, acrylic acid copolymers, polyacrylamide, their derivatives and partially hydrolyzed products, vinyl polymers and copolymers such as polyvinyl acetate and polyacrylate acid ester; derivatives of the above polymers; and other synthetic resins. Other suitable binders include aqueous emulsions of addition-type polymers and interpolymers prepared from ethylenically unsaturated monomers such as acrylates including acrylic acid, methacrylates including methacrylic acid, acrylamides and methacrylamides, itaconic acid and its half-esters and diesters, styrenes including substituted styrenes, acrylonitrile and methacrylonitrile, vinyl acetates, vinyl ethers, vinyl and vinylidene halides, and olefins and aqueous dispersions of polyurethanes, aqueous dispersions of sulfonated polyurethanes, polyesterionomers, and aqueous dispersions of sulfonated polyesters. Additional suitable binders are disclosed in U.S. Pat. Nos. 5,356,468 and 5,366,544, incorporated herein by reference. Gelatin derivatives, aqueous dispersed polyurethanes, sulfonated polyurethanes, polyesterionomers, and aqueous emulsions of vinylidene halide interpolymers, vinyl acetate copolymers, methacrylates and cellulosics are preferred binders for conductive layers of this invention. Preferred vinylidene halide based polymers include terpolymers of vinylidene chloride/methyl acrylate/itaconic acid and vinylidene chloride/acrylonitrile/acrylic acid. Preferred methacrylates include polymethylmethacrylate and butylmethacrylate-containing polymers. Preferred cellulosics include cellulose acetate, cellulose triacetate, and cellulose nitrate. Preferred polyurethane binders are aliphatic, anionic polyurethanes which have an ultimate elongation to break of at least 350 percent, such as Witcobond W-236 commercially available from Witco Corporation, and aliphatic, anionic, polyurethanes which have a tensile elongation to break of at least 50% and a Young's modulus measured at 2% elongation of at least 50,000 lb/in.sup.2, such as Witcobond W-232.
The ratio of conductive vanadium oxide to polymeric film-forming binder in a conductive layer is one of the critical factors which influences the ultimate conductivity of that layer. If this ratio is too small, little or no antistatic property is exhibited. If the ratio is very large, adhesion between the conductive layer and the support or overlying layers can be diminished. The optimum ratio of conductive material to binder can vary depending on the colloidal vanadium oxide conductivity, vanadium oxide morphology, binder type, total dry weight coverage or coating thickness, and the conductivity requirements for the imaging element. The dry weight ratio of colloidal vanadium pentoxide to polymeric film-forming binder is preferably from 4:1 to 1:500, and more preferably from 2:1 to 1:250. While relatively high polymer binder to vanadium oxide weight ratios of greater than 4:1 and even greater than 8:1 may be desirable for many applications to provide good adhesion to underlying and overlying layers, dispersions of vanadium oxide gels are not stable with many polymeric binders at such high binder ratios, in particular many polyurethane polymeric binders. In accordance with a preferred embodiment of the invention, stabilized intercalated vanadium oxide gels allow for the use of such binders at relatively high levels in electrically conductive layers.
Solvents useful for preparing dispersions and coating formulations containing polymer intercalated colloidal vanadium oxide include water; alcohols such as methanol, ethanol, propanol, isopropanol; ketones such as acetone, methylethyl ketone, and methylisobutyl ketone; esters such as methyl acetate, and ethyl acetate; glycol ethers such as methyl cellusolve, ethyl cellusolve; ethylene glycol, and mixtures thereof. Preferred solvents include water, alcohols, and acetone.
In addition to the intercalated colloidal vanadium pentoxide and one or more suitable film-forming polymeric binders, other components that are well known in the photographic art can also be present in the conductive layer of this invention. Other addenda, such as: matting agents, lubricating agents, surface active agents including fluorine-containing surfactants, dispersing and coating aids, viscosity modifiers, polymer latices to improve dimensional stability, charge control agents, soluble and/or solid particle dyes, co-binders, antifoggants, biocides, and various other conventional addenda optionally can be present in any or all of the layers of the imaging element.
Conductive layers in accordance with this invention can be applied to a variety of supports. Typical photographic film supports include: cellulose nitrate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, poly(vinyl acetal), poly(carbonate), poly(styrene), poly(ethylene terephthalate), poly(ethylene naphthalate), poly(ethylene terephthalate) or poly(ethylene naphthalate) having included therein a portion of isophthalic acid, 1,4-cyclohexane dicarboxylic acid or 4,4-biphenyl dicarboxylic acid used in the preparation of the film support; polyesters wherein other glycols are employed such as, for example, cyclohexanedimethanol, 1,4-butanediol, diethylene glycol, polyethylene glycol; ionomers as described in U.S. Pat. No. 5,138,024, incorporated herein by reference, such as polyester ionomers prepared using a portion of the diacid in the form of 5-sodiosulfo-1,3-isophthalic acid or like ion containing monomers, polycarbonates, and the like; blends or laminates of the above polymers. Supports can be either transparent or opaque depending upon the application. Transparent film supports can be either colorless or colored by the addition of a dye or pigment. Film supports can be surface-treated by various processes including corona discharge, glow discharge, UV exposure, flame treatment, electron-beam treatment, as described in U.S. Pat. No. 5,718,995; or treatment with adhesion-promoting agents including dichloro- and trichloroacetic acid, phenol derivatives such as resorcinol, 4-chloro-3-methyl-phenol and p-chloro-m-cresol; and solvent washing or can be overcoated with adhesion promoting primer or tie layers containing polymers such as vinylidene chloride-containing copolymers, butadiene-based copolymers, glycidyl acrylate or methacrylate-containing copolymers, maleic anhydride-containing copolymers, condensation polymers such as polyesters, polyamides, polyurethanes, polycarbonates, mixtures and blends thereof, and the like. Other suitable opaque or reflective supports are paper, polymer-coated paper, including polyethylene-, polypropylene-, and ethylene-butylene copolymer-coated or laminated paper, synthetic papers, pigment-containing polyesters, and the like. Of these supports, films of cellulose triacetate, poly(ethylene terephthalate), and poly(ethylene naphthalate) prepared from 2,6-naphthalene dicarboxylic acids or derivatives thereof are preferred. The thickness of the support is not particularly critical. Support thicknesses of 2 to 10 mils (50 .mu.m to 254 .mu.m), e.g., are suitable for photographic elements in accordance with this invention.
Supports can be surface-treated by various processes including corona discharge, glow discharge, UV exposure, flame treatment, electron-beam treatment, or treatment with adhesion-promoting agents including dichloro- and trichloroacetic acid, phenol derivatives such as resorcinol and p-chloro-m-cresol, solvent washing or overcoated with adhesion promoting primer or tie layers containing polymers such as vinylidene chloride-containing copolymers, butadiene-based copolymers, glycidyl acrylate or methacrylate-containing copolymers, maleic anhydride-containing copolymers, condensation polymers such as polyesters, polyamides, polyurethanes, polycarbonates, mixtures and blends thereof, and the like.
Dispersions containing intercalated colloidal vanadium pentoxide, a polymeric film-forming binder, and various additives in a suitable liquid vehicle can be applied to the aforementioned film or paper supports using any of a variety of well-known coating methods. Handcoating techniques include using a coating rod or knife or a doctor blade. Machine coating methods include air doctor coating, reverse roll coating, gravure coating, curtain coating, bead coating, slide hopper coating, extrusion coating, spin coating and the like, as well as other coating methods known in the art.
The electrically-conductive layer of this invention can be applied to the support at any suitable coverage depending on the specific requirements of a particular type of imaging element. For example, for silver halide photographic films, total dry weight coverages for conductive layers containing vanadium pentoxide are preferably in the range of from about 0.002 to 1.5 g/m.sup.2 with the higher coverages generally preferred at higher binder/vanadium oxide ratios. More preferred dry coverages are in the range of about 0.005 to 0.5 g/m.sup.2. The conductive layers of this invention typically exhibit a surface electrical resistivity (SER) value of less than 1.times.10.sup.10 ohms/square, preferably less than 1.times.10.sup.9 ohms/square, and more preferably less than 1.times.10.sup.8 ohms/square. When overcoated with an optional auxiliary layer such as an abrasion resistant protective layer, barrier layer, or curl control layer, the conductive layers of this invention typically exhibit internal electrical resistivity values of less than 1.times.10.sup.11 ohms/square, preferably less than 1.times.10.sup.10 ohms/square, and more preferably less than 1.times.10.sup.9 ohms/square.
Imaging elements incorporating conductive layers of this invention also can comprise additional layers including adhesion-promoting layers, lubricant or transport-controlling layers, hydrophobic barrier layers, antihalation layers, abrasion and scratch protection layers, additional conductive layers and other special function layers. Optional additional conductive layers can be located on the same side of the support as the imaging layer(s) or on both sides of the support. Another conductive subbing layer can be applied either under or over a gelatin subbing layer containing an antihalation dye or pigment. Alternatively, both antihalation and antistatic functions can be combined in a single layer which is typically coated on the same side of the support as the sensitized emulsion layer. Further, an optional conductive layer can be used as an outermost layer of an imaging element, for example, as a protective layer overlying an image-forming layer. When a conductive layer is applied over a sensitized emulsion layer, it is not necessary to apply any intermediate layers such as barrier or adhesion-promoting layers between the conductive overcoat layer and the imaging layer(s), although they can optionally be present. It is also specifically contemplated to use an abrasion resistant layer, protective topcoat, or transport-controlling layer overlying the conductive layer of the present invention. One example of a suitable protective topcoat for use in combination with the electrically-conductive layer of the present invention is described in U.S. Pat. No. 5,679,505. The protective topcoat consisting of specified polyurethane binder and a lubricant and is particularly useful for use in a motion picture film. U.S. Pat. No. 5,006,451 discloses a latex polymer barrier layer applied over a vanadium oxide layer which is also suitable to the present invention.
In a particularly preferred embodiment, imaging elements comprising the electrically-conductive layers of this invention are photographic elements which can differ widely in structure and composition. For example, said photographic elements can vary greatly with regard to the type of support, the number and composition of the image-forming layers, and the number and types of auxiliary layers that are included in the elements. In particular, photographic elements can be still films, motion picture films, x-ray films, graphic arts films, paper prints or microfiche. It is also specifically contemplated to use the conductive layer of the present invention in small format films as described in Research Disclosure, Item 36230 (June 1994). Photographic elements can be either simple black-and-white or monochrome elements or multilayer and/or multicolor elements adapted for use in a negative-positive process or a reversal process. Suitable photosensitive image-forming layers are those which provide color or black and white images. Such photosensitive layers can be image- forming layers containing silver halides such as silver chloride, silver bromide, silver bromoiodide, silver chlorobromide and the like. Both negative and reversal silver halide elements are contemplated. For reversal films, the emulsion layers described in U.S. Pat. No. 5,236,817, especially examples 16 and 21, are particularly suitable. Any of the known silver halide emulsion layers, such as those described in Research Disclosure, Vol. 176, Item 17643 (December, 1978), Research Disclosure, Vol. 225, Item 22534 (January, 1983), Research Disclosure, Item 36544 (September, 1994), and Research Disclosure, Item 37038 (February, 1995) and the references cited therein are useful in preparing photographic elements in accordance with this invention. Generally, the photographic element is prepared by coating one side of the film support with one or more layers comprising a silver halide emulsion and optionally one or more subbing layers.
The coating process can be carried out on a continuously operating coating machine wherein a single layer or a plurality of layers are applied to the support.
For multicolor elements, layers can be coated simultaneously on the composite film support as described in U.S. Pat. Nos. 2,761,791 and 3,508,947.
Additional useful coating and drying procedures are described in Research Disclosure, Vol. 176, Item 17643 (December, 1978).
Imaging elements incorporating conductive layers in accordance with this invention useful for specific imaging applications such as color negative films, color reversal films, black-and-white films, color and black-and-white papers, electrographic media, dielectric recording media, thermally processable imaging elements, thermal dye transfer recording media, laser ablation media, and other imaging applications should be readily apparent to those skilled in photographic and other imaging arts.

The method of the present invention is illustrated by the following detailed examples of its practice. However, the scope of this invention is by no means restricted to these illustrative examples.
SAMPLES A-D
Colloidal vanadium oxide gels were prepared by a melt-quench method as described in U.S. Pat. No. 4,203,769. Vanadium pentoxide was melted in a furnace, quenched into distilled water and aged for 3 months to form a uniform reddish-brown colloidal gel. The resulting vanadium oxide gel was diluted with distilled water to 0.285 weight percent V.sub.2 O.sub.5 for Sample A. The vanadium oxide gel was added to solutions in water of polyvinylpyrrolidone (PVP) having an average molecular weight of 37,900 to give the corresponding total weight percentages of V.sub.2 O.sub.5 and PVP indicated in Table 1 for Samples B-D.
SAMPLES E-H
Colloidal vanadium oxide gels were prepared by a melt-quench method as described in U.S. Pat. No. 4,203,769. Mixtures of silver oxide (up to 10 mole percent) and vanadium pentoxide were melted in a furnace, quenched into distilled water and aged for 3 months to form a uniform reddish-brown colloidal gel. The resulting silver-doped vanadium oxide gels were diluted with distilled water to 0.285 weight percent V.sub.2 O.sub.5 for Sample E or added to solutions of PVP in water to give the corresponding total weight percentages of V.sub.2 O.sub.5 and PVP indicated in Table 1 for Samples F-H.
SAMPLES I and J
Colloidal vanadium oxide gels were prepared by an ion exchange method. 300 ml of a 0.35 M solution of sodium metavanadate in distilled water was poured through a column of 100 grams Dowex 50X2-100 resin which had been previously washed with 1.2 M HCl. The solution was aged for 3 months to form a uniform reddish-brown colloidal gel (2.8 weight percent solids). The resulting vanadium oxide gels were either diluted with distilled water to 0.285 weight percent vanadium pentoxide (Sample I) or added to a solution of PVP in distilled water to give a solution containing 0.285 weight percent vanadium pentoxide and 0.14 weight percent PVP (Sample J).
SAMPLES K AND L
Colloidal vanadium oxide gels were prepared by hydrolysis of vanadium oxoalkoxide as taught in U.S. Pat. No. 5,407,603. 15.8 g of vanadium oxoisobutoxide was added to a stirred solution of 1.56 g of 30 percent hydrogen peroxide in 233 ml of water. The resulting dark brown gel was stirred at room temperature for 3 hours, poured into a glass jar and aged for 3 months at room temperature to yield a 2.2 weight percent reddish-brown gel. The resulting vanadium oxide gel was either diluted with distilled water to 0.285 weight percent vanadium pentoxide (Sample K) or added to a solution of PVP in distilled water to give a solution containing 0.285 weight percent vanadium pentoxide and 0.14 weight percent PVP (Sample L).
SAMPLES M AND N
Calcium-doped colloidal vanadium oxide gels were prepared by a melt-quench method similar to Samples E and F. A mixture of calcium oxide (up to 3 mole percent) and vanadium pentoxide was melted in a furnace, quenched into distilled water and aged for 3 months to form a uniform reddish-brown colloidal gel. The resulting vanadium oxide gel was either diluted with distilled water to 0.285 weight percent vanadium pentoxide (Sample M) or added to a solution of PVP in distilled water to give a solution containing 0.285 weight percent vanadium pentoxide and 0.14 weight percent PVP (Sample N).
SAMPLES O AND P
Doped colloidal vanadium oxide gels were prepared by a melt-quench method similar to Samples E and F. A mixture of silver oxide (up to 8 mole percent), lithium fluoride (up to 1 mole percent) and vanadium pentoxide was melted in a furnace, quenched into distilled water and aged for 3 months to form a uniform reddish-brown colloidal gel. The resulting vanadium oxide gel was either diluted with distilled water to 0.285 weight percent vanadium pentoxide (Sample O) or added to a solution of PVP in distilled water to a give a solution containing 0.285 weight percent vanadium pentoxide and 0.14 weight percent PVP (Sample P).
SAMPLES Q AND R
Zinc-doped colloidal vanadium oxide gels were prepared by a melt-quench technique similar to Samples E and F. A mixture of zinc oxide (up to 3 mole percent) and vanadium pentoxide was melted in a furnace, quenched into distilled water and aged for 3 months to form a uniform reddish-brown colloidal gel. The resulting vanadium oxide gel was either diluted with distilled water to 0.285 weight percent vanadium pentoxide (Sample Q) or added to a solution of PVP in distilled water to give a solution containing 0.285 weight percent vanadium pentoxide and 0.14 weight percent PVP (Sample R).
SAMPLES S AND T
Doped colloidal vanadium oxide gels were prepared by a melt-quench method similar to Samples E and F. A mixture of silicon dioxide (up to 4 mole percent), silver oxide (up to 8 mole percent) and vanadium pentoxide was melted in a furnace, quenched into distilled water and aged for 3 months to form a uniform reddish-brown colloidal gel. The resulting vanadium oxide gel was either diluted with distilled water to 0.285 weight percent vanadium pentoxide (Sample S) or added to a solution of PVP in distilled water to give a solution containing 0.285 weight percent vanadium pentoxide and 0.14 weight percent PVP (Sample T).
TABLE 1______________________________________Description of Vanadium Oxide Gels. wt % wt % Dopant Sample Type V.sub.2 O.sub.5 PVP species Synthetic Method______________________________________Sample A Comp. 0.285 -- undoped melt-quench Sample B Inv. 0.285 0.14 undoped melt-quench Sample C Inv. 0.285 0.28 undoped melt-quench Sample D Inv. 0.285 0.70 undoped melt-quench Sample E Comp. 0.285 -- Ag melt-quench Sample F Inv. 0.285 0.14 Ag melt-quench Sample G Inv. 0.285 0.28 Ag melt-quench Sample H Inv. 0.285 0.70 Ag melt-quench Sample I Comp. 0.285 -- undoped ion exchange Sample J Inv. 0.285 0.14 undoped ion exchange Sample K Comp. 0.285 -- undoped oxoalkoxide Sample L Inv. 0.285 0.14 undoped oxoalkoxide Sample M Comp. 0.285 -- Ca melt-quench Sample N Inv. 0.285 0.14 Ca melt-quench Sample O Comp. 0.285 -- AgO/LiF melt-quench Sample P Inv. 0.285 0.14 AgO/LiF melt-quench Sample Q Comp. 0.285 -- Zn melt-quench Sample R Inv. 0.285 0.14 Zn melt-quench Sample S Comp. 0.285 -- Si/Ag melt-quench Sample T Inv. 0.285 0.14 Si/Ag melt-quench______________________________________
EXAMPLES 1-8
Colloidal vanadium oxide gel samples A-H (0.285 weight percent) were spin-coated at 2000 rpm on glass microscope slides and allowed to air dry. The d-spacing (001) corresponding to the basal distance between vanadium layers in the coating was determined by X-ray diffraction using Cu K.sub..alpha. radiation. Table 2 gives d-spacing values for Examples 1-8. The increase in d-spacing of the undoped or doped vanadium oxide gel with increasing polyvinylpyrrolidone amount indicates intercalation of the polymer resulting in a modified vanadium oxide gel structure. Though by no means a requirement of the invention, it is believed that preferential association of vinyl-containing polymers with catalytically active or reactive sites consequently reduces chemical reactivity or hinders other compounds from reacting with the vanadium oxide, thereby resulting in the improved solution stability and thermal stability described below.
TABLE 2______________________________________XRD Results Vanadium oxide Sample gel sample wt % PVP d-spacing ( .ANG.)______________________________________Example 1 Sample A 0 12.8 Example 2 Sample B 0.14 20.7 Example 3 Sample C 0.28 26.0 Example 4 Sample D 0.70 40.6 Example 5 Sample E 0 12.4 Example 6 Sample F 0.14 23.6 Example 7 Sample G 0.28 29.0 Example 8 Sample H 0.70 38.0______________________________________
EXAMPLE 9 AND COMPARATIVE EXAMPLE 9
Vanadium pentoxide gel samples G and E were mixed with a para-(t-octyl)phenoxy poly(ethoxy) ethanol surfactant commercially available from Rohm & Haas under the tradename Triton X-100 at a nominal ratio of 1/1 for Example 9 and Comparative Example 9, respectively. Nominally 3.6 mg of the sample containing vanadium pentoxide and surfactant was placed in a 20 ml septum capped headspace vial. The samples were equilibrated at 100.degree. C. for two hours. The headspace above the sample was analyzed by Headspace GC mass spectrometry using a Perkin-Elmer HS-40 Headspace analyzer. Separation was achieved with a 30M, Restek Rtx-50, 0.25 mm ID, 1 .mu.m thick film capillary column. The gas chromatograph oven was preheld at 40.degree. C. for four minutes and then heated to 250.degree. C. at 15.degree. C./min. The mass scan range was from 21 to 250 atomic mass units with a 3 minute solvent delay. In addition, vanadium pentoxide gel samples E and G without a surfactant were evaluated. Reaction products and retention times for the samples are given in Table 3.
EXAMPLE 10 AND COMPARATIVE EXAMPLE 10
Vanadium pentoxide gel samples G and E were mixed with a para-isononylphenoxy polyglycidol surfactant commercially available from Olin Mathieson Corporation under the tradename Surfactant 10G at a nominal ratio of 1/1 for Example 10 and Comparative Example 10, respectively. Nominally 3.6 mg of the sample containing vanadium pentoxide and surfactant was placed in a ml septum capped headspace vial. The samples were equilibrated at 100.degree. C. for two hours. The headspace above the sample was analyzed by Headspace GC mass spectrometry using a Perkin-Elmer HS-40 Headspace analyzer. Separation was achieved with a 30M, Restek Rtx-50, 0.25 mm ID, 1 .mu.m thick film capillary column. The gas chromatograph oven was preheld at 40.degree. C. for four minutes and then heated to 250.degree. C. at 15.degree. C./min. The mass scan range was from 21 to 250 atomic mass units with a 3 minute solvent delay. In addition, vanadium pentoxide gel samples E and G without a surfactant were evaluated. Reaction products and retention times for the samples are given in Table 3.
TABLE 3______________________________________GC Mass spectrometry results with surfactants (units are in mass spectrometer detector area counts) Sample Sample Comp. Comp. species E G Ex. 9 Ex. 9 Ex. 10 Ex. 10______________________________________Formic acid 0 0 13.5 309.7 5.9 14.2 1,2-Ethanediol 0 0 0 12.4 0 0 Monoformate 1,2-Ethanediol 0 0 0 123.1 0 0 diformate 2-Methoxy-1,3- 0 0 0 115.1 0 8.5 Dioxalane______________________________________
EXAMPLE 11 AND COMPARATIVE EXAMPLE 11
Vanadium oxide gel samples E and F were spin coated on silicon wafers. One microliter of acetone was added to the vanadium oxide coatings from samples E and F for Comparative Example 11 and Example 11, respectively. The coated silicon wafers were placed in 22 ml headspace vials and equilibrated for 3 hrs at 125.degree. C. The headspace above the samples was analyzed using a Perkin-Elmer HS-40 Headspace analyzer. The gas chromatagraph oven was held for 3 minutes at 40.degree. C., then heated to 230.degree. C. at 12.degree. C./min and held for 5 minutes at 230.degree. C. The mass scan range was from 21 to 550 atomic mass units. Gas chromatography results for the samples and for acetone similarly applied to a silicon wafer without a vanadium oxide coating are given in Table 4.
TABLE 4______________________________________GC Mass spectrometry results with acetone. (units are in mass spectrometer detector area counts) retention acetone Comp. species time (min.) onto Si wafer Ex. 11 Example 11______________________________________Acetone 4.8 1239 1209 1281 Acetic Acid 14.5 0 58.3 12.8 Formic Acid 15.3 0 36.4 4.4______________________________________
EXAMPLE 12 AND COMPARATIVE EXAMPLE 12
Nominally equal amounts of vanadium pentoxide gel Samples E and G were placed in 22 ml headspace vials and one microliter of acetone was injected into the vials containing Samples E and G for Comparative Example 12 and Example 12, respectively. The samples were equilibrated at 100.degree. C. for two hours. The headspace above the sample was analyzed by Headspace GC mass spectrometry using a Perkin-Elmer HS-40 Headspace analyzer. Separation was achieved with a 30M, Restek Rtx-50, 0.25 mm ID, 1 .mu.m thick film capillary column. The gas chromatograph oven was preheld at 40.degree. C. for four minutes and then heated to 230.degree. C. at 12.degree. C./min and held at 230.degree. C. for 5 minutes. The mass scan range was from 21 to 550 atomic mass units. GC analysis was also obtained for Samples E and G without the addition of acetone and for acetone without the presence of vanadium oxide gel. Reaction products and retention times for the samples are given in Table 5.
TABLE 5______________________________________GC Mass spectrometry results with acetone. (units are in mass spectrometer detector area counts) retention time Sample Sample Comp. species (min.) E G Acetone Ex. 12 Ex. 12______________________________________Acetone 4.6 0 0 3333 3121.7 3325.8 Acetic acid 14.5 0 0 0 182.0 8.6 Formic acid 15.27 0 0 0 114.2 0______________________________________
EXAMPLE 13 AND COMPARATIVE EXAMPLE 13
Nominally equal amounts of vanadium pentoxide gel Samples E and G were placed in 22 ml headspace vials and one microliter of methanol was then injected into the vials containing Samples E and G for Comparative Example 13 and Example 13, respectively. The samples were equilibrated at 100.degree. C. for two hours. The headspace above the sample was analyzed by Headspace GC mass spectrometry using a Perkin-Elmer HS-40 Headspace analyzer. Separation was achieved with a 30M, Restek Rtx-50, 0.25 mm ID, 1 .mu.m thick film capillary column. The gas chromatograph oven was preheld at 40.degree. C. for four minutes and then heated to 230.degree. C. at 12.degree. C./min and held at 230.degree. C. for 5 minutes. The mass scan range was from 21 to 550 atomic mass units. GC analysis was also obtained for Samples E and G without the addition of methanol and for methanol without the presence of vanadium oxide gel. Reaction products and retention times for the samples are given in Table 6.
TABLE 6______________________________________GC Mass spectrometry results with methanol. (units are in mass spectrometer detector area counts) retention time Sample Sample Meth- Comp. species (min) E G anol Ex. 13 Ex. 13______________________________________Dimethoxy 3.5 0 0 0 218.1 118.2 methane Methyl 3.8 0 0 0 588.4 50.6 formate Methanol 5.9 0 0 2425 874.1 2414.2 Acetic acid 14.5 0 0 0 0 93.0 Formic Acid 15.27 0 0 0 48.4 0______________________________________
EXAMPLE 14 AND COMPARATIVE EXAMPLE 14
Nominally equal amounts of vanadium pentoxide gel Samples E and G were placed in 22 ml headspace vials and one microliter of n-butanol was injected into the vials containing Samples E and G for Comparative Example 14 and Example 14, respectively. The samples were equilibrated at 100.degree. C. for two hours. The headspace above the sample was analyzed by Headspace GC mass spectrometry using a Perkin-Elmer HS-40 Headspace analyzer. Separation was achieved with a 30M, Restek Rtx-50, 0.25 mm ID, 1 .mu.m thick film capillary column. The gas chromatograph oven was preheld at 40.degree. C. for four minutes and then heated to 230.degree. C. at 12.degree. C./min and held at 230.degree. C. for 5 minutes. The mass scan range was from 21 to 550 atomic mass units. GC analysis was also obtained for Samples E and G without the addition of n-butanol and for n-butanol without the presence of vanadium oxide gel. Reaction products and retention times for the samples are given in Table 7.
TABLE 7______________________________________GC Mass spectrometry results with butanol. (units are in mass spectrometer detector area counts) reten- tion Sample Sample n- Comp. species time E G butanol Ex. 14 Ex. 14______________________________________Acetaldehyde 3.23 0 0 0 43.5 0 Propanal 4.26 0 0 0 298.6 62.45 Butanal 5.63 0 0 0 2900.65 1416.35 Butyl Formate 8.23 0 0 0 1157.4 129.85 Butanal 8.73 0 0 0 63.35 15.65 Butyl Acetate 9.11 0 0 0 135.15 14.5 Butanol 10.21 0 0 4485 2604.55 3914.4 Acetic Acid 14.5 0 0 0 67.8 11.53 Formic Acid 15.29 0 0 0 102.3 9.85 Propanoic 15.5 0 0 0 128.6 15.85 Acid Butanoic Acid 16.5 0 0 0 77.4 6______________________________________
The above results for Examples 9-14 clearly indicate intercalated vanadium oxide gels have greatly reduced reactivity with common coating solvents or surfactants than prior art colloidal vanadium oxide (Comparative Examples 9-14). In particular, there are fewer species detected after reaction with intercalated vanadium oxide gels than after reaction with non-intercalated vanadium oxide. Furthermore, for the identified species from reaction with intercalated vanadium oxide, there is typically a reduced level present when compared with non-intercalated vanadium oxide. The reduced catalytic or chemical activity resulting for intercalated vanadium oxide is of particular interest for photographic imaging elements which may be fogged by the evolution of unanticipated chemical species from a coated layer and for applications in which reaction with common solvents can result in a corrosive environment due to the formation of various organic acids.
EXAMPLE 15
Vanadium oxide gel sample F intercalated with polyvinylpyrrolidone was placed in a prewetted Spectra/Por molecular porous membrane dialysis tube having a molecular weight cutoff of 12,000-14,000 and a dry thickness of 0.9 mil (23 microns). The tube ends were tied and the filled dialysis tube placed in a 4000 ml beaker of continuously replenished distilled water and allowed to dialyze for one week. The resulting vanadium oxide gel sample had a uniform dark reddish-brown coloration with no observable change in appearance.
A coating solution consisting of 0.0285 weight percent dialyzed vanadium pentoxide gel, 0.0285 weight percent terpolymer latex binder and 0.02 weight percent Triton X-100 (Rohm & Haas) was coated on a 4 mil (100 .mu.m) thick polyethylene terephthalate support using a coating rod to give a 3 mil (76 .mu.m) wet coverage and a nominal dry coverage of 0.022 g/m.sup.2. The terpolymer latex consisted of acrylonitrile, vinylidene chloride, and acrylic acid. The support had been coated previously with a typical primer layer consisting of acrylonitrile, vinylidene chloride, and acrylic acid. The surface electrical resistivity (SER) of the conductive layer was measured at nominally 20.degree. C. and 50% relative humidity using a two-point DC electrode method similar to that described in U.S. Pat. No. 2,801,191. For adequate antistatic performance, conductive layers with SER values of 10 log ohms/square or less are preferred. The SER value for the vanadium oxide gel coating was 8.3 log ohms/sq. indicating excellent antistatic properties for the dialyzed vanadium oxide gel.
COMPARATIVE EXAMPLE 15
Vanadium oxide gel sample E was placed in a prewetted Spectra/Por molecular porous membrane dialysis tube having a molecular weight cutoff of 12,000-14,000 and a dry thickness of 0.9 mil (23 microns). The tube ends were tied and the filled dialysis tube placed in a 4000 ml beaker of continuously replenished distilled water and dialyzed for one week. The resulting vanadium oxide gel sample had a light orange brown appearance with green-brown fibular debris rather than a uniform dark reddish-brown coloration indicating considerable degradation of the gel structure.
A coating solution consisting of 0.0285 weight percent dialyzed vanadium oxide gel, 0.0285 weight percent terpolymer latex binder and 0.020 5 weight percent Triton X-100 was coated on 4 mil (100 .mu.m) thick polyethylene terephthalate support using a coating rod to give a 3 mil (76 .mu.m) wet coverage and a nominal dry coverage of 0.022 g/m.sup.2. The terpolymer latex consisted of acrylonitrile, vinylidene chloride, and acrylic acid. The support had been coated previously with a typical primer layer consisting of acrylonitrile, vinylidene chloride, and acrylic acid. The SER value for the vanadium oxide gel coating was greater than 12 log ohms/sq. which is not considered effective for antistatic applications.
EXAMPLES 16-23 AND COMPARATIVE EXAMPLES 16-23
Solutions of vanadium oxide gel samples A-T were diluted with distilled water to 0.0285 weight percent vanadium pentoxide. The solutions had 0.020 weight percent of Triton X-100 added as a coating aid. The solutions were coated on 4 mil (100 .mu.m) thick polyethylene terephthalate supports using a coating rod to give a 3 mil (76 .mu.m) wet coverage and a nominal dry coverage of 0.022 g/m.sup.2. The support had been coated previously with a typical primer layer consisting of a terpolymer latex of acrylonitrile, vinylidene chloride, and acrylic acid. Coatings were prepared using fresh solutions or aged solutions. The coatings were dried at 100.degree. C. for 1 minute. SER values for vanadium oxide gel layers are given in Table 8.
EXAMPLES 24-31 AND COMPARATIVE EXAMPLES 24-31
Solutions of vanadium oxide gel samples A-T were diluted with ethanol to 0.0285 weight percent vanadium pentoxide. The solutions had 0.020 weight percent of Triton X-100 added as a coating aid. The solutions were coated on 4 mil (100 .mu.m) thick polyethylene terephthalate supports using a coating rod to give a 3 mil (76 .mu.m) wet coverage and a nominal dry coverage of 0.022 g/m.sup.2.The support had been coated previously with a typical primer layer consisting of a terpolymer latex of acrylonitrile, vinylidene chloride, and acrylic acid. Coatings were prepared using fresh solutions or aged solutions. The coatings were dried at 100.degree. C. for 1 minute. SER values for vanadium oxide gel layers are given in Table 9.
EXAMPLES 32-39 AND COMPARATIVE EXAMPLES 32-39
Solutions of vanadium oxide gel samples A-T were diluted with a 50:50 mixture of ethanol and acetone to 0.0285 weight percent vanadium pentoxide. The solutions had 0.020 weight percent of Triton X-100 added as a coating aid. The solutions were coated on 4 mil (100 .mu.m) thick polyethylene terephthalate supports using a coating rod to give a 3 mil (76 .mu.m) wet coverage and a nominal dry coverage of 0.022 g/m.sup.2. The support had been coated previously with a typical primer layer consisting of a terpolymer latex of acrylonitrile, vinylidene chloride, and acrylic acid. Coatings were prepared using fresh solutions or aged solutions. The coatings were dried at 100.degree. C. for 1 minute. SER values for vanadium oxide gel layers are given in Table 10.
TABLE 8______________________________________Surface electrical resistivity (log ohms/sq) of vanadium oxide gel coatings from aqueous solutions SER log ohms/sq. V.sub.2 O.sub.5 oxide Fresh aged soln aged soln aged soln Sample gel sample soln (2 weeks) (10 weeks) (6 months)______________________________________Example 16 Sample B 9.3 9.2 9.4 ** Example 17 Sample F 7.7 7.7 ** 8.5 Example 18 Sample J 8.5 8.7 9.0 ** Example 19 Sample L 8.5 8.2 9.0 ** Example 20 Sample N 8.3 8.6 9.1 ** Example 21 Sample P 7.6 7.9 8.5 ** Example 22 Sample R 7.7 7.9 8.5 ** Example 23 Sample T 9.3 9.5 9.7 ** Comp. Ex 16 Sample A 9.1 9.3 11.9 ** Comp. Ex 17 Sample E 7.4 8.0 ** >12 Comp. Ex 18 Sample I 8.6 9.0 >12 ** Comp. Ex 19 Sample K 8.4 8.9 >12 ** Comp. Ex 20 Sample M 8.1 8.5 >12 ** Comp. Ex 21 Sample O 7.7 7.8 >12 ** Comp. Ex 22 Sample Q 7.9 7.8 >12 ** Comp. Ex 23 Sample S 9.4 9.9 >12 **______________________________________
TABLE 9______________________________________Surface electrical resistivity (log ohm/sq) of vanadium oxide gel coatings from ethanolic solutions. SER log ohms/sq for coatings V.sub.2 O.sub.5 oxide Fresh aged soln aged soln aged soln Sample gel sample soln (2 weeks) (10 weeks) (6 months)______________________________________Example 24 Sample B 9.1 9.3 9.5 ** Example 25 Sample F 7.6 7.9 ** 8.1 Example 26 Sample J 8.4 8.8 9.1 ** Example 27 Sample L 8.3 8.9 9.1 ** Example 28 Sample N 8.2 8.5 9.0 ** Example 29 Sample P 7.9 8.5 8.8 ** Example 30 Sample R 8.0 8.4 8.6 ** Example 31 Sample T 9.1 9.0 9.6 ** Comp. Ex 24 Sample A 9.3 9.2 >12 ** Comp. Ex 25 Sample E 6.7 9.2 ** >12 Comp. Ex 26 Sample I 8.7 9.3 >12 ** Comp. Ex 27 Sample K 8.5 9.2 >12 ** Comp. Ex 28 Sample M 8.0 8.7 >12 ** Comp. Ex 29 Sample O 8.0 7.9 >12 ** Comp. Ex 30 Sample Q 8.2 8.1 >12 ** Comp. Ex 31 Sample S 9.6 9.8 >12 **______________________________________
TABLE 10______________________________________Surface electrical resistivity (log ohms/sq) of vanadium oxide gel coatings prepared from acetone/ethanol mixtures. SER log ohms/sq. for coatings V.sub.2 O.sub.5 oxide Fresh aged soln aged soln aged soln Sample gel sample soln (2 weeks) (10 weeks) (6 months)______________________________________Example 32 Sample B 9.1 9.4 9.3 ** Example 33 Sample F 8.3 8.3 ** 8.4 Example 34 Sample J 8.3 8.7 9.0 ** Example 35 Sample L 8.4 8.5 9.0 ** Example 36 Sample N 8.1 8.7 9.1 ** Example 37 Sample P 8.1 7.9 9.0 ** Example 38 Sample R 8.1 8.0 8.7 ** Example 39 Sample T 9.2 9.5 9.8 ** Comp. Ex 32 Sample A 9.0 9.4 >12 ** Comp. Ex 33 Sample E 7.8 8.2 ** >12 Comp. Ex 34 Sample I 8.7 9.4 >12 ** Comp. Ex 35 Sample K 8.6 9.1 >12 ** Comp. Ex 36 Sample M 8.2 8.5 >12 ** Comp. Ex 37 Sample O 7.6 7.8 >12 ** Comp. Ex 38 Sample Q 7.8 8.0 >12 ** Comp. Ex 39 Sample S 9.5 9.6 >12 **______________________________________
The above SER results demonstrate the greatly improved shelf life of the coating formulations with minimal impact on the antistatic properties of coated layers for both aqueous and solvent-based coating formulations.
EXAMPLE 40 AND COMPARATIVE EXAMPLE 40
Antistatic coating compositions consisting of silver-doped vanadium pentoxide gels, an aqueous dispersible polyurethane binder and surfactant were prepared according to the formulation given below. Example 40 used PVP intercalated silver-doped vanadium oxide gel (Sample F) and Comparative Example 40 used a silver-doped vanadium oxide gel without PVP, (Sample E). The polyurethane binder was Witcobond W-236 commercially available from Witco Corporation.
______________________________________Component Weight percent (wet)______________________________________V.sub.2 O.sub.5 -gel Sample E or F 0.033 W-236 Polyurethane binder 0.133 Triton X-100 0.033 Water balance______________________________________
The appearance and viscosity of the coating formulations evaluated immediately after preparation and for aging up to 48 hrs are reported in Table 11. Comparative Example 40 appeared as a clear reddish-brown solution initially but changed to a greenish gelatinous mixture within 24 hrs. This instability was also reported for a similar formulation used in Example 6 of U.S. Pat. No. 5,718,995. Examples 14-16 of U.S. Pat. No. 5,718,995 teach the use of multiple coating formulations which were mixed just prior to the coating hopper to avoid the observed solution instability.
Example 40 remained a clear reddish-brown solution with no significant change in viscosity for 24 hrs demonstrating the effectiveness of PVP intercalation in reducing reactivity between colloidal vanadium oxide gel and polyurethane binders. A significant advantage of the present invention is improved solution stability for antistatic coating formulations. Furthermore, due to the dramatically improved solution stability of colloidal vanadium oxide intercalated with a vinyl-containing polymer compared to prior art vanadium pentoxide gels, a simplified coating process (i.e., single dispersion) can be used over the process described for Examples 14-16 of U.S. Pat. No. 5,718,995. A similar mixture to the above formulation was prepared except additional water was substituted for the polyurethane binder. The mixture remained a clear reddish-brown solution for 48 hrs with no noticeable change in viscosity, indicating solution instability for non-intercalated vanadium oxide results primarily from reaction between the polyurethane binder and vanadium oxide gel.
EXAMPLE 41 AND COMPARATIVE EXAMPLE 41
Antistatic coating compositions consisting of silver-doped vanadium pentoxide gel Sample G (Example 41) or Sample E (Comparative Example 41), and a polyurethane binder were prepared. Due to the potential for interaction of vanadium oxide with surfactants a coating aid was not included. Furthermore, the polyurethane binder (Witcobond W-236 ) was purified by a combination of ion exchange and diafiltration to remove low molecular weight species and ions which could react with the vanadium oxide gel. The formulation is given below:
______________________________________Component Weight percent (wet)______________________________________V.sub.2 O.sub.5 -gel Sample E or G 0.040 Polyurethane binder 0.160 Surfactant -- Water balance______________________________________
Appearance and solution viscosity (centipoise) for the samples are given in Table 11. While the present Comparative Example without intercalated PVP did not form a gelatinous precipitate, the initial solution had a cloudy appearance indicating flocculation and demonstrated a significant increase in viscosity, though not as dramatic as for Comparative Example 40. Example 41 on the other hand showed no significant change in either solution appearance or viscosity.
TABLE 11__________________________________________________________________________ Coating Formulation AgeSample 0 hr 4 hr 24 hr 48 hr__________________________________________________________________________Example 40 Appearance clear reddish-brown clear reddish-brown clear reddish-brown clear reddish-green Viscosity 4.2 4.0 4.3 4.4 Comp Ex 40 Appearance clear reddish-brown clear green cloudy green gel cloudy green gel Viscosity 3.9 3.9 25.2 24.7 Example 41 Appearance clear reddish-brown clear reddish-brown clear reddish-brown clear reddish-brown Viscosity 5.0 5.0 5.0 4.9 Comp Ex 41 Appearance cloudy brown cloudy brown cloudy brown cloudy brown Viscosity 4.9 8.3 8.3 8.4__________________________________________________________________________
EXAMPLE 42 AND COMPARATIVE EXAMPLE 42
Antistatic coating compositions were prepared in a similar manner to Example 41 and Comparative Example 41, however the polyurethane binder was not purified by ion exchange or diafiltration. Example 42 used Sample G and Comparative Example 42 used Sample E. The initial appearance of Example 42 was a dark greenish-brown solution which had a viscosity of nominally 4.9 centipoise. After aging for 17 hrs, Example 42 remained as a dark greenish-brown stable solution and had a solution viscosity of 4.9 centipoise indicating minimal chemical reactivity. The initial appearance of Comparative Example 42 was a dark brownish-green solution which had a viscosity of nominally 4.5 centipoise. After aging for 17 hrs, Comparative Example 42 resulted in a green gelatinous precipitate having a solution viscosity of 8.4 centipoise indicating significant chemical reactivity.
EXAMPLES 43-47 AND COMPARATIVE EXAMPLES 43-47
Antistatic coating compositions consisting of silver-doped vanadium oxide gel Sample F (Examples 43-47) or Sample E (Comparative Examples 43-47), various polymeric binders and a surfactant were prepared according to the formulation below. The binder for Example 43 and Comparative Example 43 was a polyurethane latex commercially available from Witco Corporation under the tradename Witcobond W-232. A different polyurethane latex, Flexthane 639 EXP emulsion, commercially available from Air Products and Chemicals, Inc was used as the binder for Example 44 and Comparative Example 44. Example 45 and Comparative Example 45 used an acrylic copolymer emulsion, commercially available from Rohm and Haas under the tradename Rhoplex WL-51. Example 46 and Comparative Example 46 used a latex of glycidyl methacrylate and Example 47 and Comparative Example 47 used a terpolymer latex of methacrylic acid, vinylidene chloride and itaconic acid as the polymeric binder. The solutions were coated on 4 mil (100 .mu.m) thick polyethylene terephthalate support using a coating rod to give a 0.9 mil (23 .mu.m) wet coverage and a nominal dry coverage of 0.025 g/m.sup.2. The support had been previously coated with a typical primer layer consisting of a terpolymer latex of acrylonitrile, vinylidene chloride, and acrylic acid. Coatings were prepared using either fresh or aged solutions and dried at 100.degree. C. for 3 minutes. Solution appearance, solution viscosity (centipoise) and SER values (log ohm/sq) for coatings prepared from fresh and aged solutions are given in Table 12.
______________________________________Component Weight percent (wet)______________________________________V.sub.2 O.sub.5 -gel Sample E or F 0.033 Binder 0.033 Triton X-100 0.033 Water balance______________________________________
TABLE 12__________________________________________________________________________ Coating Formulation AgeExample 0 hr 4 hr 24 hr 72 hr__________________________________________________________________________Example 43 Appearance clear reddish-brown clear reddish-brown clear reddish-brown clear light green Viscosity 2.2 2.2 2.2 2.1 SER 8.6 -- 8.7 8.9 Comp Ex 43 Appearance clear reddish-brown clear reddish-brown reddish-ye llow gel green gel Viscosity 3.3 10.7 12.2 12.0 SER 8.6 -- 9.5 12.4 Example 44 Appearance clear reddish-brown clear reddish-brown clear reddish-brown clear reddish-brown Viscosity 2.3 2.2 2.2 2.2 SER 8.5 -- 8.5 8.9 Comp Ex 44 Appearance clear reddish-brown clear reddish-brown clear reddish-yellow clear yellow Viscosity 1.9 1.8 1.9 2.2 SER 8.3 -- 8.4 8.6 Example 45 Appearance clear reddish-brown clear reddish-brown clear reddish-brown clear reddish-yellow Viscosity 2.3 2.2 2.2 2.2 SER 8.6 -- 9.0 9.1 Comp Ex 45 Appearance clear reddish-brown clear reddish-brown clear reddish-yellow clear light green Viscosity 1.9 1.8 1.7 1.7 SER 8.6 -- 8.3 8.7 Example 46 Appearance clear reddish-brown clear reddish-brown clear reddish-brown clear reddish-brown Viscosity 2.3 2.2 2.3 2.2 SER 9.1 -- 8.6 8.5 Comp Ex 46 Appearance clear reddish-brown cloudy red-brown cloudy red-brown cloudy red-brown Viscosity 1.8 1.7 1.7 1.7 SER -- -- -- -- Example 47 Appearance clear reddish-brown clear reddish-brown clear reddish-brown clear reddish-brown Viscosity 2.2 2.2 2.2 2.2 SER 9.1 -- 8.3 9.7 Comp Ex 47 Appearance clear reddish-brown clear reddish-brown clear reddish-yellow clear greenish-yello w Viscosity 1.8 1.7 1.7 1.7 SER 8.9 -- 9.3 9.1__________________________________________________________________________
EXAMPLES 48-55
Antistatic coating formulations were prepared using vanadium oxide gel Sample F (Examples 48-55) Sample E (Comparative Examples 48-55), a surfactant, and polyvinyl acetate-ethylene emulsions commercially available from Air Products and Chemicals under the tradenames Airflex 426 (Examples and Comparative Examples 48-50), Airflex 460 (Examples and Comparative Examples 51-53), Airflex 420 (Example and Comparative Example 54), and Airflex 421 (Example and Comparative Example 55) at the concentrations indicated below. The coating formulations were applied to a moving 4 mil (100 .mu.m) thick polyethylene terephthalate support using a coating hopper to give nominal dry coverages coverage of 0.01, 0.02, and 0.03 g/m.sup.2. The polyethylene terephthalate support had been previously coated with a typical primer layer consisting of a terpolymer of acrylonitrile, vinylidene chloride, and acrylic acid. Total optical (ortho) and ultraviolet densities (D.sub.min) were evaluated at 530 nm and 380 nm, respectively, using a X-Rite Model 361T transmission densitometer. Net or Delta D.sub.min valued were determined by correcting the total D.sub.min values for the contribution from the support. Descriptions of the electrically-conductive layers, SER values, Delta UV D1 and Delta UV D.sub.min values are given in Table 13. Similar coating formulations using vanadium oxide gel sample E, without intercalated PVP were not sufficiently stable and consequently were not coated.
______________________________________Component Weight percent (wet)______________________________________V.sub.2 O.sub.5 -gel Sample F 0.033 Binder 0.133 Triton X-100 0.033 Water balance______________________________________
TABLE 13______________________________________ dry covg. .DELTA.UV .DELTA.ortho Example binder g/m.sup.2 SER.sup.+ dry adh D.sub.min D.sub.min______________________________________Example 48 Airflex 426 0.01 8.8 excellent .016 .002 Example 49 Airflex 426 0.02 8.7 excellent .029 .004 Example 50 Airflex 426 0.03 8.8 excellent .028 .003 Example 51 Airflex 460 0.01 9.4 excellent .013 .001 Example 52 Airflex 460 0.02 8.4 excellent .029 .005 Example 53 Airflex 460 0.03 9.1 excellent .029 .005 Example 54 Airflex 420 0.01 8.5 excellent -- -- Example 55 Airflex 421 0.01 8.7 excellent -- -- Comp. Ex. 48 Airflex 426 0.01 * * * * Comp. Ex. 49 Airflex 426 0.02 * * * * Comp. Ex. 50 Airflex 426 0.03 * * * * Comp. Ex. 51 Airflex 460 0.01 * * * * Comp. Ex. 52 Airflex 460 0.02 * * * * Comp. Ex. 53 Airflex 460 0.03 * * * * Comp. Ex. 54 Airflex 420 0.01 * * * * Comp. Ex. 55 Airflex 421 0.01 * * * *______________________________________ .sup.+ log .OMEGA./sq *Did not coat due to poor solution stability
EXAMPLE 56
An antistatic coating formulation was prepared using vanadium oxide gel sample F, a surfactant, and a terpolymer latex consisting of n-butylmethacrylate, styrene and methacrlyloyloxyethyl--sulfonic acid at the concentrations indicated below. The coating formulation was applied to a moving 4 mil (100 .mu.m) thick polyethylene terephthalate support using a coating hopper to give nominal dry coverages coverage of 0.01 and 0.02 g/m.sup.2. The polyethylene terephthalate support had been previously coated with a typical primer layer consisting of a terpolymer of acrylonitrile, vinylidene chloride, and acrylic acid. SER, adhesion and net ultraviolet and optical densities for the electrically-conductive layers are given in Table 14.
______________________________________Component Weight percent (wet)______________________________________V.sub.2 O.sub.5 -gel 0.033 Binder 0.033 Triton X-100 0.033 Water balance______________________________________
TABLE 14______________________________________ dry covg SER .DELTA. UV .DELTA. ortho Sample g/m.sup.2 log .OMEGA./sq. dry adh D min D min______________________________________Ex. 56a 0.01 9.5 excellent 0.026 0.003 Ex. 56b 0.02 7.9 excellent 0.045 0.006______________________________________
The above examples demonstrate the improved solution stability for either aqueous dispersions or solvent-based dispersions of vanadium oxide gels intercalated with a water soluble vinyl-containing polymer relative to prior art vanadium oxide gels. The improved solution stability also allows formulation with polymeric binders which are not compatible with prior art vanadium oxide gels. Consequently, the improved compatibility with polymeric binders permits the use of electrically-conductive layers containing colloidal vanadium oxide having physical and chemical properties in addition to electrical properties which more adequately meet the requirements of various imaging elements. In particular, polymeric binders resulting in improved adhesion of underlying or overlying layers or in improved abrasion or scratch resistance can be used in the electrically-conductive layer of the present invention. Furthermore, improved solution stability is desirable for manufacturing simplicity and can reduce coating defects due to agglomeration or coagulation of the coating formulation or as a result of filter plugging.
The above described supports with electrically-conductive layers may be coated with imaging layers, such as photographic silver halide emulsion imaging layers as well known in the art, in order to obtain an imaging element in accordance with the invention. As described above, the imaging layer(s) may be coated on the same side of the support as the electrically conductive layer, or on the opposite side, and the imaging elements may contain additional conventional imaging element layers above, below, or between such imaging layers and electrically-conductive layers.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

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Imaging element comprising an electrically-conductive layer containing intercalated vanadium oxide

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