CA1338180C - Photographic element with novel subbing layer - Google Patents

Abstract

The use of a gelled network of inorganic oxide particles on the polymeric surface of a substrate provides a subbing layer having the potential for antistatic proper-ties, antihalation properties, and good coatability.

Description

~ 42155CAN8A

1~38180 PHOTOGRAPHIC ELEMENT WITH NOVEL SUBBING LAYER

1. Field of the Invention The present invention relates to photographic emulsions on substrates having a subbing or priming layer thereon.

2. Background of the Art The construction of silver halide photographic elements has become an art that is an amalgum of many dif-ferent sciences and technologies. Such varied disciplines 15 as polymer chemistry, crystallography, physics, electro-statics, dye chemistry, coating technologies, and the like have to come into focus to produce what is to the consumer a simple snapshot.
Two complex problems that have traditionally been 20 Of concern to the photographic industry are adherence of the - photographic emulsions to the substrates of choice (i.e., polymeric substrates such as polyester, polyolefin, or cellulosic ester bases and polymer coated paper bases such as white pigment filled polyolefin or polyvinylidene - 25 chloride coated paper). Another problem, particularly in high image content film which is processed mechanically is the development of static or triboelectric charges in the film which create spurious images.
Many different compositions, combinations of 30 layers, and treatment of substrates have been proposed to effect better adhesion between emulsion layers and sub-strates as is evidenced by the number of patents in this technical area. A sampling of these patents include U.S.
Patent Nos. 3,271,345, 2,943,937, 4,424,273, 3,791,831 and 35 the like. A great amount of work has also been directed in the photographlc sciences to the elimination of electrostatic charges on photographic film. Examples of the diverse work done in this area includes U.S. Patents 4,582,782, 3,884,699, 3,573,049 and the like.
Assorted handling problems (e.g., adhering of layers) are often addressed by the use of particulate matting agents in backside coatings or surface layers of photographic elements. Also sensitometric effects (e.g., lightscattering) are achieved by the use of particle-containing layers in photographic elements. These uses of particulate containing layers shown in U.S. patents 4,343,873, 4,144,064, 3,507,678, 4,022,622 and the like.
Typical photographic supports comprise a base material (e.g., polyester, cellulose triacetate, or paper) with a subbing layer on at least one surface to assist in the adherence of the gelatin layers, including the emulsion layers, to the base. Conventional subbing layers are described in U.S. patent Nos. 3,343,840, 3,495,984, 3,495,985 and 3,788,856.
SUMMARY OF THE INVENTION
The present invention relates to photographic elements having at least one sllver halide emulsion layer over a substrate, where the substrate has at least one polymeric surface to which is adhered a layer cornprising a gelled or a hydrolyzed network of inorganlc particles, preferably inorganic oxide particles, containing an ambifunctional silane.
According to one aspect of the present invention there ls provlded a radlatlon sensltlve photographlc element comprlslng a substrate wlth at least one polymerlc surface and at least one photographlc emulslon over sald at least one polymerlc surface, sald element belng characterlzed by the fact that sald at least one polymerlc surface has adhered thereto a contlnuous gelled network of lnorganlc oxlde partlcles contalnlng an adheslon promotlng effectlve amount of an amblfunctlonal sllane whereln sald amblfunctlonal sllane ls represented by the formula:
(Q)n-R-Sl(OR )3 whereln Rl ls alkyl or aryl, R ls an organlc group havlng n+l external valances, n ls 1, or 2, and Q ls a molety reactlve with gelatln hardeners or gelatln.
Accordlng to a further aspect of the present lnventlon there ls provlded a polymerlc fllm havlng on at least one surface thereof a contlnuous gelled network of lnorganlc oxlde partlcles contalnlng an adheslon promotlng amount of an amblfunctlonal sllane whereln sald amblfunctlonal sllane ls represented by the formula:
(Q)n-R-Sl(OR )3 whereln Rl ls alkyl or aryl, R ls an organlc group havlng n+l external valances, n ls 1, or 2, and Q ls a molety reactlve wlth gelatln hardeners or gelatln.

- 2a -1~38180 DETAILED DESCRIPTION OF THE INVENTION
The present lnventlon relates to photographlc elements. These elements comprlse a substrate havlng at least one sllver hallde emulslon layer on a surface thereof. A
surface wlth an emulslon thereon 18 herelnafter referred to as a ma~or surface of the substrate. The sllver hallde emulslon generally comprlses sllver hallde gralns (also - 2b -- 3 - 1~ 8 1 8 0 60557-3467 referred to as crystals or particles) carried in a water-penetrable binder medium of hydrophilic colloid. It has been recently found that the use of a gelled or hydrolyzed network of inorganic particles, preferably oxides, as a layer on a polymeric surface provides an excellent subbed (or primed) substrate for photographic emulsions. It was found that this gelled particulate layer is capable of providing one or more excellent properties to the photographic element including, but not limited to antistatic properties, ease of coatability of the particulate layer, photoinertness (harmless to the photographic emulsion and its properties), adhesion (both wet and dry, to both the substrate and the emulsion layers,) and reduction in specular reflectance (i.e.
antihalation properties). However, it has been determined that wet adhesion can be weak during development processing. It has been hypothesized that the bond between the gelled network and the gelatin is an acid/base bond. During the elevated pH conditions of development, this bond is sufficiently weakened so that other materials in the emulsion will compete with the gelatin for reaction with sites on the sol-gel coating. This can weaken the bond between the gelatin layer and gelled network layer. Lifting or separation of the layers can result.
It has been found according to the practice of the present invention that the addition of an ambifunctional silane into or onto the gelled network will produce a strong chemical bond between the inorganic particles and the gelatin.
The term ambifunctional silane means that the compound has reactive silanes on one end of the molecule and a different reactive species capable of reacting with a photographic hardener - - 3a - 60557-3467 for gelatin or directly with gelatin. This second functionality enables the compound to react with the inorganic particle (through the silane group) and also h~. A

react wlth the gelatln (reactlng wlth the gelatln hardener whlch also reacts wlth the gelatln). Amongst the preferred second functlonal groups on the compound are amlno groups and epoxy (e.g., glycldyl) groups. The second functlonallty may be present as a slngle functlonal molety or may be present as a multlple number of such groups.
A formula that may be used to represent the amblfunctlonal sllanes of the present lnventlon ls (Q)n-R-sl(oRl)3 whereln Rl ls alkyl or aryl, R ls an organic group wlth (n+l) external bonds or valences, n ls 0, 1 or 2, and Q ls a molety reactlve wlth photographlc hardeners or dlrectly wlth gelatln (e.g., alpha-amlno aclds).
Preferably Rl is alkyl of 1 to 10 carbon atoms and most preferably 1 to 4 carbon atoms. R ls preferably an allphatlc or aromatlc brldglng group such as alkylene, arylene, alkarylene, or aralkylene whlch may be lnterrupted wlth ether llnkages (oxygen or thloethers), nltrogen llnkages, or other relatlvely lnert moletles. More preferably R ls alkylene of 1 to 12 carbon atoms, preferably 2 to 8 carbon atoms, wlth n equal to 1. Q ls preferably epoxy, or amlno, prlmary or secondary, more preferably prlmary amlno.
Where prevlously lndicated that the second func-tional group may be present as a multlple number of such groups lt ls meant that the molety (Q)n~R~ may lnclude mol-etles such as NH2-(CH2)2-NH-(CH2)2-NH-(CH2)3-NH2-(CH2)-3 ( NH2 ) 2-CH-CH2-1~38180 ( NH2 )--CH2\
CH
( NH2 )--CH2/

5 and the like.
The substrates of the invention may comprise any material having at least one polymeric surface which is to be used as the major surface of the substrate.
The silver halide photographic emulsions which are 10 used in the present invention, as protective colloids, in addition to gelatin, include acylated gelatins such as phthalated gelatin and malonated gelatin, and may also contain cellulose compounds such as hydroxyethyl cellulose and carboxymethyl cellulose, soluble starch such as dextrin, 15 hydrophilic polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrylamide, plasticizers for dimensional stabilization, latex polymers, and matting agents can be added. The finished emulsion is coated on a suitable support.
Supports which can be used include films of syn-thetic polymers such a polyalkyl acrylate or methacrylate, polystyrene, polyvinyl chloride, partial formalation poly-vinyl alcohol, polycarbonate, polyesters such as polyethyl-ene terephthalate, and polyamides, films of cellulose 25 derivatives such as cellulose nitrate, cellulose acetate, cellulose triacetate, and cellulose acetate butyrate, paper covered with a-olefin polymers or gelatin (a natural polymer), for example, and synthetic papers made of poly-styrene; that is, any of transparent or opaque support 30 commonly used in photographic elements can be used. Primed polymeric substrates are also useful, including, but not limited to, gelatin-primed polymers (e.g., gelatin on poly(ethylene terephthalate)), and poly(vinylidene chloride) copolymers on polyester. Other primers such as aziridines, 35 acrylates, and melamine-formaldehyde are also known. This includes polymeric materials loaded with pigments and particulates such as titania to improve the white background -_ -6- 1338180 of the image and to provide antihalation or other sensito-metric effects.
The substrates of the invention may be used with any type of photographic silver halides including, but not 5 limited to silver chloride, silver bromide, silver chloro-bromide, silver iodochlorobromide, silver bromoiodide and silver chloroiodide grains, which may be in any of the many available crystal forms or habits including, but not limited to cubic, tetrahedral, lamellar, tabular, orthorhombic 10 grains, etc.
Soluble silver salts and soluble halides can be reacted by methods such as a single jet process, a double jet process, and a combination thereof. In addition, a procedure can be employed in which silver halide grains are 15 formed under the presence of an excess of silver ions (a so-called reverse mixing process). A so-called controlled double jet process can also be employed in which the-pAg of the liquid phase wherein the silver halide is formed is kept constant. Two or more silver halide emulsions which have 20 been prepared independently may be used in combination with each other.
Soluble salts are usually removed from the silver halide emulsion after the precipitate formation or physical ripening of the silver halide emulsion. For this purpose, a 25 noodle water-washing method can be employed in which the soluble salts are removed by gelling the emulsions. A
flocculation method utilizing inorganic salts containing polyvalent anions, anionic surface active agents, anionic polymers or gelatin derivatives can also be used.
Although so-called primitive emulsions which are not chemically sensitized can be used as the silver halide emulsions, the silver halide emulsions are usually chemi-cally sensitized. This chemical sensitization can be carried out, for example, by the methods as described in H.
35 Frieser ed., Die Grundlagen der Photographischen Prozesse mit Silverhalogeniden, Akademische Verlagsgesellschaft, pp.
675-734 (1968).

_ 7_ 1~38180 That is, a sulfur sensitization method using sulfur-containing compounds capable of reacting with active gelatins and silver (e.g., thiosulfates, thioureas, mercapto compounds, and rhodanines), a reduction sensitization method 5 using reducing substances (e.g., stannous salts, amines, hydrazine derivatives, formamidinesulfinic acid, and silane compounds), a noble metal sensitization method using noble metal compounds (e.g., gold complex salts, and metal complex salts of Group VIII metals, such as platinum, rhodium, 10 iridium, and palladium, of the Periodic Table), and so forth can be used singly or in combination with each other.
The sulfur sensitization method is described in detail, for example, in U.S. Patent Nos. 1,574,944, 2,410,689, 2,278,947, 2,728,668 and 3,656,955; the reduction 15 sensitization method, in U.S. Patent Nos. 2,983,609, 2,419,974 and 4,054,458; and the noble metal sensitization method, in U.S. Patent Nos. 2,399,083, 2,448,060 and British Patent No. 618,061.
In photographic emulsions which are used in the 20 present invention may be incorporated various compounds for the purpose of, e.g., preventing the formation of fog during the production, storage or photographic processing of the light-sensitive material, or stabilizing photographic per-formance. That is, many compounds known as antifoggants or 25 stabilizers, such as azoles (E.G., benzothiazolium salts, nitroimidazoles, nitrobenzimidazoles, chlorobenzimidazoles, bromobenzimidazoles, mercaptothiazoles, mercaptobenzothia-zoles, mercaptobenzimidazoles, mercaptothiadiazoles, aminotriazoles, benzotriazoles, nitrobenzotriazoles, and 30 mercaptotetrazoles, (particularly 1-phenyl-5-mercaptotetra-zole), mercaptopyrimidines, mercaptotriazines, thioketo compounds (e.g., oxazolinethione), azaindenes (e.g., triazaindenes, tetraazaindenes (particularly 4-hydroxy-substituted-(1,3,3a,7)tetraazaindenes), and penta-35 azaindenes), benzenethiosulfonic acid, benzenesulfinic acid,and benzenesulfonic acid amide can be added.

~ -8- 1338180 Typical examples of such compounds and a method of using them are described, for example, in U.S. Patent Nos.
3,954,474, 3,982,947 and Japanese Patent Publication No.
28660/77.
The photographic emulsion layers of the light-sensitive material of the present invention may contain polyalkylene oxide or its derivatives (e.g., ethers, esters and amines), thioether compounds, thiomorpholines, quaternary ammonium salt compounds, urethane derivatives, 10 urea derivatives, imidazole derivatives, 3-pyrazolidones, hydroquinone or its derivatives, and the like for the pur-pose of increasing sensitivity or contrast, or accelerating development. For example, compounds as described in U.S.
Patent Nos. 2,400,532, 2,423,549, 2,716,062, 3,617,280, 15 3,722,021, 3,808,003 and British Patent No. 1,488,991 can be used.
As binders or protective colloids to be used in the emulsion layers and intermediate layer of the light-sensitive material of the present invention, it is advan-20 tageous to use gelatins. In addition, other hydrophiliccolloids can be used. For example, proteins such as gelatin derivatives, graft polymers of gelatin and other polymers, albumin, and casein, sugar derivatives such as cellulose derivatives (e.g., hydroxyethyl cellulose, carboxymethyl 25 cellulose, and cellulose sulfate), sodium alginate, and starch derivatives, and various synthetic hydrophilic polymeric substances, homopolymers or copolymers, such as polyvinyl alcohol, polyvinyl alcohol partial acetal, poly(N-vinyl)pyrrolidone, polyacrylic acid, polymethacrylic 30 acid, polyacrylamide, polyvinyl imidazole, and polyvinyl pyrazole can be used.
The light-sensitive material of the present inven-tion is particularly effectively used as a black-and-white reflection light-sensitive material which is to be subjected to rapid processing. In addition, it can be used as an X-ray recording light-sensitive material, a photomechanical process light-sensitive material, a light-sensitive material to be used in a facsimile system, etc., and further, as a multilayer, multicolor photographic light-sensitive material having at least two different spectral sensitivities.
The multilayer, multicolor photographic material usually comprises a support, and at least one red-sensitive emulsion layer, at least one green-sensitive emulsion layer and at least one blue-sensitive emulsion layer on the support. The order in which the above layers are arranged 10 can be chosen appropriately. Usually the red-sensitive emulsion layer contains cyan dye forming couplers, the green-sensitive emulsion layer contains magenta dye forming couplers, and the blue-sensitive emulsion layer contains yellow dye forming couplers. In some cases, other combina-15 tions can be employed. Even in the case of the multilayer,multicolor photographic material, the effects of the present invention are exhibited significantly in a reflection light-sensitive material.
Spectral sensitizing dyes may be used in one or 20 more silver halide emulsions useful on the subbed substrates of the present invention. These sensitizing dyes are well known in the art to increase the sensitization of silver halide grains to various portions of the electromagnetic spectrum such as the ultraviolet, blue, green, yellow, 25 orange, red, near infrared, and infrared. These dyes may be used singly or in combination with other dyes to sensitize the emulsions.
The substrate of the invention bears a coating comprising a continuous gelled network of inorganic metal 30 oxide particles, the network containing an ambifunctional silane. The particles preferably have an average primary particle size of less than about 500 or 200 A. As used =
herein, the term "continuous" refers to covering the surface of the substrate with virtually no straight-line penetrable 35 discontinuities or gaps in the areas where the gelled network is applied. However, the layer may be and usually is porous, without significant straight-line pores or gaps in the layer. The term "gelled network" refers to an aggregation of colloidal particles linked together to form a porous three-dimensional network. Generally all of or the majority of linkages are from the material of the particles 5 to each other and to the silane, but some binder such as up to about 5% by weight of the metal oxide of gelatin may also be present. The term "porous" refers to the presence of voids between the inorganic metal oxide particles created by the packing of the metal oxide particles. The term "primary 10 particle size" refers to the average size of unagglomerated single particles of inorganic metal oxide. The term "particle" includes spherical, non-spherical, and fibrillar particulate arrangements. If the ambifunctional silane is added to an aqueous metal oxide sol before coating, then the 15 silane will be hydrolyzed at the positions described as (OR') at page 4, line 6, substituting hydroxy groups for the (OR') groups. For example, a triethoxysilane will become a trihydroxysilane. In solution with the metal oxide particles, the hydrolyzed silane molecules may associate 20 with the metal oxide particles by "oxane" bonding in a reversible fashion (SiOH + HOM(particle)~Si-O-M(particle)).
As the solution is dried into a coated layer, it is expected that most of the hydrolyzed silane molecules will become associated with metal oxide particles through "oxane"
25 bonding susch that they cannot be washed out of the coating by a simple water wash. The presence of the silane molecules does not prevent the gelled particle network from gaining cohesive strength, although the time required to gain cohesive strength may be increased.
The coating should be thicker than a monolayer of particles. Preferably the coating comprises a thickness equal to or greater than three average particle diameters and more preferably equal to or greater than five particle diameters.
The articles of the invention comprise a substrate which may be transparent, translucent, or opaque to visible light having at least one polymeric surface, and have formed - 11 ~
thereon a coatlng in the form of a continuous gelled network of lnorganlc oxlde partlcles with an adheslon promoting effec-tlve amount of an amblfunctlonal sllane. When the coatlng ls applled to~transparent substrates to achleve lncreased llght transmlsslvlty, the coated artlcle preferably exhlblts a total average lncrease ln transmlsslvlty of normal lncldent llght of at least two percent and up to as much as ten percent or more, when compared to an uncoated substrate, dependlng on the substrate coated, over a range of wavelengths extendlng at least between 400 to 900 nm. An lncrease ln llght transmlsslon of two percent or more ls generally vlsually apparent and ls sufficient to produce a measurable increase in energy transmlsslvlty when the coated substrate is used. An increase in transmissivlty ls also present at wavelengths lnto the lnfrared portlon of the spectrum.
The gelled network ls a porous coatlng havlng voids between the lnorganlc oxlde particles. If the porosity is too small, the antlreflectance may be reduced. If the poroslty is too large, the coatlng ls weakened and may have reduced adheslon to the substrate. Generally, the colloldal solutlon from whlch the gelled network ls obtalned ls capable of provldlng poroslty of about 25 to 70 volume percent, preferab-ly about 30 to 60 volume percent when drled. The poroslty can be determlned by drylng a sufflclent amount of the colloldal solutlon to provlde a drled product sample of about 50 to 100 mg and analyzlng the sample uslng a "Quantasorb " surface area analyzer avallable from Quantachrome Corp., Syosett, NY.
The voids of the porous coating provide a multlpllc-lty of subwavelength lnterstlces between the inorganic par-tlcles where the lndex of refractlon abruptly changes fromthat of alr to that of the coatlng materlal. These subwavelength lnterstlces, whlch are present throughout the coatlng layer, provlde a coatlng whlch may have a calculated lndex of refractlon ~RI) of from about 1.15 to 1.40, preferab-ly 1.20 to 1.30 dependlng on the porosity of the coating.

Trade-mark T

When the porosity of the coating is high, e.g., about 70 volume percent or more, lower values for the RI are obtained. When the porosity of the coating is low, e.g., 25 volume percent or less, higher values for the RI are 5 obtained.
The average primary particle size of the colloidal inorganic metal oxide particles is preferably less than about 200 A. The average primary particle size of the colloidal inorganic metal oxide particles is more preferably 10 less than about 70 A. When the average particle size becomes too large, the resulting dried coating surface is less efficient as an antireflection coating.
The average thickness of the dried coating is preferably from about 300 to 10,000 A, more preferably 800 15 to 5000 A and most preferably between 900 and 2000 A. Such coatings provide good antistatic properties. When the coating thickness is too great, the coating has reduced adhesion and flexibility and may readily flake off or form powder under mechanical stress.
Articles such as transparent sheet or film materials may be coated on a single side or on both sides to increase light transmissivity, the greatest increase being achieved by coating both sides.
The process of coating the layer of the present 25 invention comprises coating a substrate with a solution of colloidal inorganic metal oxide particles (and preferably the silane at this point), the solution preferably containing at least 0.2 or 0.5 to 15 weight percent of the particles, the particles preferably having an average 30 primary particle size less than about 500 or 200 A, more preferably less than about 70 A, and drying the coating at a temperature less than that which degrades the substrate, preferably less than about 200C, more preferably in the range of 80 to 120C. The coating provides the substrate 35 with an average reduction in specular reflectance of at least two percent over wavelengths of 400 to 900 nm.

_ -13- 1338180 Coating may be carried out by standard coating techniques such as bar coating, roll coating, knife coating curtain coating, rotogravure coating, spraying and dipping.
The substrate may be treated prior to coating to obtain a 5 uniform coating using techniques such as corona discharge, flame treatment, and electron beam. Generally, no pretreat-ment is required. The ambifunctional silane may be added before, during or after coating. It is preferred to add the silane to the coating mixture before coating. If the silane 10 is added after the "gelled network" has been coated and dried, it should be added from a water-containing solution, so that the silane will be in its hydrolyzed form.
The colloidal inorganic oxide solution, e.g., a hydrosol or organosol, is applied to the substrate of the 15 article to be coated and dried at a moderately low temperature, generally less than about 200C, preferably 80-120C, to remove the water or organic liquid medium. The coating may also be dried at room temperature, provided the drying time is sufficient to permit the coating to dry 20 completely. The drying temperature should be less than at which the substrate degrades. The resulting coating is hygroscopic in that it is capable of absorbing and/or rehydrating water, for example, in an amount of up to about 15 to 20 weight percent, depending on ambient temperature 25 and humidity conditions.
The colloidal inorganic oxide solution utilized in the present invention comprises finely divided solid inorganic metal oxide particles in a liquid. The term "solution" as used herein includes dispersions or suspen-30 sions of finely divided particles of ultramicroscopic sizein a liquid medium. The solutions used in the practice of this invention are clear to milky in appearance. Inorganic metal oxides particularly suitable for use in the present invention are those in which the metal oxide particles are 35 negatively charged, which includes tin oxide (SnO2), titania, antimony oxide (Sb2O5), silica, and alumina-coated silica as well as other inorganic metal oxides of Groups III

and IV of the Perloclc Table and mlxtures thereof. The selec-tlon of the lnorganlc metal oxlde ls dependent upon the ultl-mate balance of propertles deslred. Inorganlcs such as sill-con nltrlde, slllcon carblde, and magneslum fluorlde when provlded ln sol form are also useful.
The colloldal coatlng solutlon preferably contalns about 0.2 to 15 welght percent, more preferably about 0.5 to 8 welght percent, colloldal lnorganlc metal oxlde partlcles. At partlcle concentratlons about 15 welght percent, the resultlng coatlng may have reduced unlformlty ln thlckness and exhlblt reduced adheslon to the substrate surface. Dlfflcultles ln obtalnlng a sufflclently thln coatlng to achleve increased llght transmlsslvlty and reduced reflectlon may also be encountered at concentratlons above about 15 welght percent.
At concentrations below 0.2 welght percent, process ineffic-iencies result due to the large amount of llquld which must be removed and antlreflectlon propertles may be reduced.
The thlckness of the applled wet coatlng solutlon ls dependent on the concentratlon of lnorganlc metal oxlde par-tlcles ln the coatlng solutlon and the deslred thlckness ofthe drled coatlng. The thlckness of the wet coatlng solutlon ls preferably such that the resultlng drled coatlng thlckness ls from about 80 to 500 nm thlck, more preferably about 90 to 200 nm thlck.
The coatlng solutlon may also optlonally contaln a surfactant to lmprove wettablllty of the solutlon on the substrate, but lnclusion of an excesslve amount of surfactant may reduce the adheslon of the coatlng to the substrate.
Examples of sultable surfactants include "Tergltol " TMN-6 (Unlon Carblde Corp.) and "Trlton " X-100 (Rohm and Haas Co.).
Generally the surfactant can be used ln amounts of up to about 0.5 welght percent of the solutlon.
The coatlng solutlon may optlonally contaln a very small amount of polymerlc blnder, partlcularly a hydrophlllc polymer blnder, to lmprove scratch reslstance, or to reduce formatlon of partlcluate dust durlng subsequent use of the Trade-mark coated substrate. Useful polymeric binders include polyvinyl alcohol, polyvinyl acetate, gelatin, polyesters, polyamides, polyvinyl pyrrolidone, copolyesters, copolymers of acrylic acid and/or methacrylic acid, and copolymers of 5 styrene. The coating solution can contain up to about 5 weight percent of the polymeric binder based on the weight of the inorganic metal oxide particles. Useful amounts of polymeric binder are generally in the range of about 0.1 to 5 weight percent to reduce particulate dust. These binders 10 can reduce some of the beneficial properties (e.g., antistatic properties) of the coatings if used in larger amounts, so that they are not most preferred.
The ambifunctional silane is generally present as at least 0.1% by weight of the solids content of the gelled 15 particulate layer. Preferably the ambifunctional silane is present as from 1 to 20% by weight of the solids content of the particulate layer. More preferably the silane is present as 0.2 to 10% by weight of the solids content of the particulate layer.
The following procedures were used in making all samples used in the following Examples.

EXAMPLES
Experimental Method: Each sample described in the attached 25 table is prepared as follows:
The sol as received from the manufacturer is diluted with water to the desired percent solids. Then the specified coupling agent is added to the diluted sol. The amount of coupling agent is calculated according to the 30 percent weight to metal oxide solids. After addition of coupling agent the mixture is vigorously shaken for 30 sec.
to dissolve the coupling agent. Then, 0.05-.1% wt. of Triton X-100 surfactant is added as a coating aid. This mixture is coated onto an appropriate substrate film by:
1) a 10 cm x 20 cm sheet of film is placed on a flat surface; 2) a bead of the mixture is drawn across the top of the sheet (about 1 milliliter); 3) the mixture is spread across the sheet by means of a #4 stainless steel wire-wound rod; 4) the coated sheet is dried in an oven for about two minutes at 100C. The dried coated sheets are allowed to stand at room temperature for one day or more before further 5 use.
Next, a standard x-ray photographic emulsion is prepared and coated onto the above sheets by: 1) the temperature of the emulsion mixture is adjusted to about 40C; 2) a bead of the emulsion (approx. 2 ml) is drawn 10 across the top of a sol-coated sheet; 3) the emulsion is spread across the sheet by means of a #24 stainless steel wire-wound rod; 4) the emulsion coated sheet is dried at 50C for about two hours.

15 Adhesion Test Methods: The following method was used to test all of the experimental samples for emulsion adhesion.
Following the tests described below, each sample is given a grade between zero (0) and 10, according to the approximate percentage of emulsion remaining on the sample. Thus if 50 20 of the emulsion remains the grade is "5". If all of the emulsion remains, the grade is "10".
The test method is: 1) a 5 cm x 10 cm portion of the x-ray emulsion coated material from above is immersed in x-ray developer at room temperature for two minutes; 2) the 25 material is removed from the developer and, while still wet with developer, scribed in a cross-hatch pattern with the corner of a razor blade, and rubbed with firm pressure in a circular motion for 24 cycles with a rubber glove-tipped index finger; 3) the sample is washed in cold water and 30 dried; 4) a 2.5 cm x 5 cm portion of 3M #610 tape is affixed over the cross-hatched area of the test material and pulled off with a vigorous snap; 5) the sample is graded as described above for emulsion adhesion.
The substrate film used in the examples was 4-mil 35 PET primed with about 0.04 microns of a poly(vinylidene chloride) containing terpolymer.

_ -17- 1338180 0.50g of a 10% wt. solution of Triton-X-100/H2O was added to each sol mixture to ald in coating.

Example 1 Four test samples were prepared according to the above method using the following silica/silane coupling agent coating solutions:
APS is 3-aminopropyltriethoxysilane A. 17.2g Nalco 2326 colloidal silica, 82.6g H2O, 0.25g APS
(2.5% silica) B. 17.2g Nalco 2326 colloidal silica, 82.7g H2O, 0.125g APS
C. - 27.6g Nalco 2326 colloidal silica, 72.0g H2), 0.4g APS
(4.0% silica) 15 D. 55.2g Nalco 2326 colloidal silica, 44.0g H2O, 0.8g APS
(9.0% silica) Each fully prepared sample was tested for adhesion according to the described method. The adhesion test results for A, C, and D were all "10" (no failure); the grade for B was 20 "9.5".

Example 2 Three test samples similar to the samples A, C, and D of Example 1 were prepared, except that no silane 25 coupling agent (APS) was added.
A. 17.2g Nalco 2326 colloidal silica, 82.8g H2O
B. 27.6g Nalco 2326 colloidal silica, 72.4g H2O
C. 55.2g Nalco 2326 colloidal silica, 44.8g H2O
The adhesion test results for A, B and C were all "0"
(complete failure).

Example 3 Three further samples were prepared in order to test various types of silane coupling agents. The samples 35 were formulated as follows:
A. 27.6g Nalco 2326 colloidal silica, 72.0g H2O, 0.40g y-glycidoxypropyltrimethoxysilane B. 27.6g Nalco 2326* colloldal slllca, 72.0g H2O, 0.40g methacryloxypropyltrlmethoxysllane C. 27.6g Nalco 2326 colloldal slllca, 72.0g H2O, 0.40g 3-chloropropyltrlethoxysllane The adheslon test results were: Sample A, "10", Sample B, "0", Sample C, "0". These results are ln agreement wlth the expected reactlvlty of the functlonal groups wlth gelatln.

Example 4 Two samples were prepared ln order to test the usefulness of organotitanate coupllng agents:
A. 27.6g Nalco 2326 colloldal slllca, 72.0g H20, 0.40g lsopropyltrl(n-ethylamlnoethylamlno)tltanate B. 27.6g Nalco 2326 colloldal slllca, 72.0g H2O, 0.40g dl-(dloctylpyrophosphato)ethylenetltanate The adheslon test result for Sample A was "3", for Sample B, "O" .

ExamPle 5 Three samples were prepared ln order to lllustrate the use of dlfferent slzesttypes of colloldal slllca:
A. 16.7g Nalco 1115 colloldal slllca, 83.lg H2O, 0.26g APS
B. 5.0g Nalco 1060 colloldal slllca, 94.8g H2O, 0.25g APS
C. 8.33g Nalco 1034A colloidal slllca, gl.5g H2O, 0.25g APS
The adheslon test results for Samples A, B and C were all "10" .

Example 6 Three samples slmllar to those of Example 5 were prepared, except that no APS was used. The adheslon test results were all "0".

Example 7 Twelve samples were prepared wlth colloldal metal oxldes other than slllca:
Trade-mark GPS ls ~-glycldoxypropyltrlmethoxysllane.
A. 21.4g Nalco TX-2588 colloldal tltanla, 78.4g H2O, 0.25g APS
B. 8.33g Nalco lSJ-612 colloldal slllca/alumlna, 91.5g H2O, 0.25g APS
*

C. 11.4g Nalco lSJ-613 colloldal alumlna, 88.4g H2O, 0.25g APS
D. 25.0g Nalco lSJ-614 colloldal alumlna, 74.8g H2O, 0.25g APS
E. lO.Og Nyacol SN-20 colloldal stannlc oxlde, 89.8g H2O, 0.25g APS
F. 17.9g Nyacol colloidal yttrla, 81.9g H2O, 0.25g APS
G. 10.4g Nyacol colloldal zlrconla slllcate, 89.4g H2O, 0.25g APS
H. 12.5g Nyacol colloldal zlrconla acetate, 87.3g H2O, 0.25g APS
I. 11.6g Nyacol colloldal cerlc nltrate, 88.2g H2O, 0.25g APS
J. 8.33g Nalco lSJ-612 colloldal slllca/alumlna, 91.5g H2O, 0.25g GPS
The adheslon test results for Samples A and E were "10", for Samples B, C, D, F, G, H, I and J the results were "0". It ls noted that ln Samples A and E the colloldal partlcles are anlonlc, whereas ln all the other samples the partlcles are catlonlc.

Example 8 Twelve samples slmllar to those of Example 7, except that no APS or GPS was used, were prepared. The adheslon test results were all "0".

Example 9 A slllca-coated sample was prepared uslng the coat-lng mlxture 2B and the above-descrlbed preparatlve method.
Thls sample was dlpped lnto a solutlon of 0.10% APS ln ethanol Trade-mark X

- l9a - 1338180 for 15 seconds and air drled. Thls was then emulslon coated and tested accordlng to the above procedures. The adheslon test result was "10".

Example 10 Four silica-coated samples were prepared using the coating mixture 2B and the above-described preparative method. These samples were coated with x-ray emulsion 5 modified as follows:
A. lOOg x-ray emulsion, 0.05g APS
B. lOOg x-ray emulsion, O.lOg APS
C. lOOg x-ray emulsion, 0.20g APS
D. lOOg x-ray emulsion, 0.40g APS
10 The adhesion test results were: Samples C and D, "10";
Sample B, "3"; Sample A, "2".

Example 11 A silica-coated sample was prepared using the 15 coating mixture lC, except that 0.56g of K&K #1312 gelatin was dissolved in the mixture. This was emulsion coated and tested according to the above procedures. The adhesion test result was "10". Furthermore the conductive and optical properties of the silica-coated sample were comparable to 20 those of silica-coated sample prepared with mixture lC.
The terms sol-gel and gelation, as they apply to the use of inorganic dispersions of particles in the formation of layers, are well understood in the art. Sol-gels, as previously described, comprise a rigidized dispersi~n of a 25 colloid in a liquid, that is the gelled network previously described. Gelation is the process of rigidizing the sol-gel. This is often accompanied by extraction of the liquid. Gelation, as opposed to pyrolysis, does not necessarily require the addition of heat as room temperatures and normal humidity conditions will allow gelation to occur. These temperatures and humidity conditions will eventually remove sufficient amounts of the liquid for the colloidal particles to become more solid.
Heat of course can be useful in speeding up the liyuid 35 extraction process as would gas flow directed against or parallel to the sol-gel coating.

The liquid extracted sol-gel coating (which will generally retain some significant amounts of liquid, e.g., at least 0.1% by weight up to 10% or 15% or more by weight in some cases) can be described in a number of various 5 physical terms which distinguish it from other particulate constructions such as sintered, adhesively bound, or thermally fused particles. The association of the particles in a sol-gel system is a continuous sol-gel network which is known to mean in the art that the 10 particles form an inorganic polymer network at the intersection of the particle (e.g., as with silica sol-gels), or an inorganic salt system. Bonding forces such as van der Waals forces and hydrogen bonding can form an important part of the mechanism of particle association.
15 These characterizations of sol-gel compositions are quite distinct from the use of polymer binders which form a binding medium to keep particles associated and where the particles themselves do not exert direct bonding forces on one another.
As previously noted, the size of the colloid particles in the sol-gel is important. Processes where particulates are ball-milled generally produce particles of no less than about 1 micron. Unless a chemical process is used to form the particles of smaller size, which agglomer-25 ate to effectively form large particles which are then ball-milled to break up the agglomeration, the particle size limit of about 1 micron from physical processing tends to hold true.
Larger particles also cannot be used in sol-gel 30 compositions to form an integral layer by only gelation processes. The large particles do not bond with sufficient strength to withstand any significant abrasion.

Claims (13)

1. A radiation sensitive photographic element comprising a substrate with at least one polymeric surface and at least one photographic emulsion over said at least one polymeric surface, said element being characterized by the fact that said at least one polymeric surface has adhered thereto a continuous gelled network of inorganic oxide particles containing an adhesion promoting effective amount of an ambifunctional silane wherein said ambifunctional silane is represented by the formula:
(Q)n-R-Si(OR1)3 wherein R1 is alkyl or aryl, R is an organic group having n+1 external valances, n is 1, or 2, and Q is a moiety reactive with gelatin hardeners or gelatin.

2. The element of claim 1 wherein said gelled network of inorganic oxide particles comprises a layer having an average thickness of between 300 and 10,000 Angstroms.

3. The element of claim 1 wherein said gelled network of inorganic oxide particles comprises a layer having an average thickness of between 800 and 5000 Angstroms.

4. The element of claim 1 wherein said gelled network of inorganic oxide particles comprises a layer having an average thickness of between 900 and 2000 Angstroms.

5. The element of claims 2, 3 or 4 wherein said inorganic oxide particles are selected from the class consisting of silica, titania, tin oxide and mixtures thereof.

6. The element of claim 1 wherein R1 is alkyl of 1 to 4 carbon atoms, R is a bridging moiety selected from the group consisting of alkylene, arylene, alkarylene, and aralkylene of up to 10 carbon atoms, n is 1, and Q is amino or epoxy.

7. The element of claim 6 wherein R is alkylene and Q is primary amino.

8. The element of the claim 1 or 3 wherein said substrate is a polymeric film selected from the group consisting of polyester, and primed polyester.

9. The element of claim 4 wherein said substrate is a polymeric film selected from the group consisting of polyester, and primed polyester.

10. A polymeric film having on at least one surface thereof a continuous gelled network of inorganic oxide particles containing an adhesion promoting amount of an ambifunctional silane wherein said ambifunctional silane is represented by the formula:
(Q)n-R-Si(OR1)3 wherein R1 is alkyl or aryl, R is an organic group having n+1 external valances, n is 1, or 2, and Q is a moiety reactive with gelatin hardeners or gelatin.

11. The film of claim 10 wherein said gelled network of inorganic oxide particles comprises a layer having an average thickness of between 800 and 5000 Angstroms.

12. The film of claims 10 or 11 wherein said inorganic oxide particles are selected from the class consisting of silica, titania, tin oxide and mixtures thereof.

13. The film of claim 10 or 11 wherein R1 is alkyl of 1 to 4 carbon atoms, R is a bridging moiety selected from the group consisting of alkylene, arylene, alkarylene, and aralkylene of up to 10 carbon atoms, n is 1, and Q is amino or epoxy.