Imaging element comprising an electrically-conductive layer with enhanced abrasion resistance

Imaging elements, such as photographic, electrostatographic and thermal imaging elements, are comprised of a support, an image-forming layer and an electrically-conductive layer comprising electronically-conductive fine particles, such as antimony-doped tin oxide particles, and gelatin-coated water-insoluble polymer particles. The use of gelatin-coated water-insoluble polymer particles as a binder in the electrically-conductive layer facilitates the preparation of stable coating compositions and provides a layer with a high degree of conductivity at low concentrations of electronically-conductive fine particles and with excellent abrasion resistant properties.

CROSS REFERENCE TO RELATED APPLICATION 
Reference is made to and priority claimed from U.S. Provisional application 
Ser. No. 60/000,236, filed 15 Jun. 1995, entitled IMAGING ELEMENT 
COMPRISING AN ELECTRICALLY-CONDUCTIVE LAYER WITH ENHANCED ABRASION 
RESISTANCE. 
FIELD OF THE INVENTION 
This invention relates in general to imaging elements, such as 
photographic, electrostatographic and thermal imaging elements, and in 
particular to imaging elements comprising a support, an image-forming 
layer and an electrically-conductive layer. More specifically, this 
invention relates to such imaging elements having an 
electrically-conductive layer with a high degree of abrasion resistance. 
BACKGROUND OF THE INVENTION 
A variety of problems associated with the formation and discharge of 
electrostatic charge during the manufacture and use of photographic films 
are well recognized in the photographic industry. These electrostatic 
charges are generated by the highly insulating polymeric film bases such 
as polyester and cellulose acetate during winding and unwinding operations 
associated with the photographic film manufacturing process and during the 
automated transport of photographic films in film cassette loaders, 
cameras, and film processing equipment during use of the photographic film 
product. 
It is well known that electrostatic charges can be effectively controlled 
or eliminated by incorporating one or more electrically-conductive 
antistatic layers in the photographic film. A wide variety of conductive 
materials can be incorporated into antistatic layers to provide a wide 
range of conductivity and antistatic performance. Typically, the 
antistatic layers for photographic applications employ materials which 
exhibit ionic conductivity where the charge is transferred by the bulk 
diffusion of charged species through an electrolyte. Antistatic layers 
comprising inorganic salts, ionic conductive polymers, and colloidal metal 
oxide sols stabilized by salts have been described. U.S. Pat. No. 
4,542,095 discloses antistatic compositions for use in photographic 
elements wherein aqueous latex compositions are used as binder materials 
in conjunction with polymerized alkylene oxide monomers and alkali metal 
salts as the antistatic agents. U.S. Pat. No. 4,916,011 describes 
antistatic layers comprising ionically conductive styrene sulfonate 
interpolymers, a latex binder, and a crosslinking agent. U.S. Pat. No. 
5,045,394 describes antistatic backing layers containing Al-modified 
colloidal silica, latex binder polymer, and organic or inorganic salts 
which provide good writing or printing surfaces. The conductivities of 
these ionic conductive antistatic layers are very dependent on humidity 
and film processing. At low humidities and after conventional film 
processing the antistatic performance is substantially reduced or 
ineffective. 
Antistatic layers employing electronic conductors have also been described. 
The conductivity of these materials depends on primarily electronic 
mobilities rather than ionic mobilities and the conductivity is 
independent of humidity. Antistatic layers which contain conjugated 
polymers, semiconductive metal halide salts, conductive carbon or 
semiconductive metal oxide particles have been described. It is 
characteristic of these electronically conductive materials to be highly 
colored or have high refractive index. Thus, providing highly transparent, 
coloress antistatic layers containing these materials poses a considerable 
challenge. 
U.S. Pat. No. 3,245,833 describes conductive coatings containing 
semiconductive silver or copper iodide dispersed as 0.1 .mu.m or less 
particles in an insulating film-forming binder exhibiting surface 
resistivities of 10.sup.2 to 10.sup.11 .OMEGA./.quadrature.. However, 
these coatings must be overcoated with a water-impermeable barrier layer 
to prevent the loss of conductivity after film processing since these 
semiconductive salts are solubilized by conventional film processing 
solutions. 
Conductive layers comprising inherently conductive polymers such as 
polyacetylene, polyaniline, polythiophene, and polypyrrole are described 
in U.S. Pat. No. 4,237,194, JP A2282245, and JP A2282248, but, these 
layers are highly colored. 
Conductive fine particles of crystalline metal oxides dispersed with a 
polymeric binder have been used to prepare humidity insensitive, 
conductive layers for various imaging applications. Many different metal 
oxides are alleged to be useful as antistatic agents in photographic 
elements or as conductive agents in electrographic elements in such 
patents as U.S. Pat. Nos. 4,275,103, 4,394,441, 4,416,963, 4,418,141, 
4,431,764, 4,495,276, 4,571,361, 4,999,276, 5,368,995. Preferred metal 
oxides are antimony doped tin oxide, aluminum doped zinc oxide, niobium 
doped titanium oxide, and metal antimonates. The high volume % of the 
conductive fine particles in the conductive coatings as taught in the 
prior art to achieve effective antistatic performance results in reduced 
transparency due to scattering losses and in brittle films subject to 
cracking and poor adherence to the support material. 
JP A4055492 describes antistatic layers comprising conductive non-oxide 
particles including TiN, NbB.sub.2, TiC, and MoB dispersed in a binder 
such as a water soluble polymer or solvent soluble resin. 
U.S. Pat. No. 5,066,422 describes vinyl surface covering materials 
comprising a fused sheet of a dry blend, wherein the dry blend contains a 
polyvinyl chloride porous resin, a plasticizer, and conductive particles. 
Reportedly, the conductive particles reside in the pores and surface of 
the polyvinyl chloride resin which thereby provides surface resistivities 
of the fused sheet of 10.sup.9 .OMEGA./.quadrature. at low weight % of the 
conductive particles. 
Fibrous conductive powders comprising antimony doped tin oxide coated onto 
nonconductive potassium titanate whiskers have been used to prepare 
conductive layers for photographic and electrographic applications. Such 
materials have been disclosed in U.S. Pat. No. 4,845,369, U.S. Pat. 
No.5,116,666, JP A63098656, and JP A63060452. Layers containing these 
conductive whiskers dispersed in a binder reportedly provide improved 
conductivity at lower volume % than the aforementioned conductive fine 
particles as a result of their higher aspect (length to diameter) ratio. 
However, the benefits obtained as a result of the reduced volume % 
requirements are offset by the fact that these materials are large in size 
(10 to 20 .mu.m long and 0.2-0.5 .mu.m diameter). The large size results 
in increased light scattering and hazy coatings. 
Transparent, binderless, electrically semiconductive metal oxide thin films 
formed by oxidation of thin metal films which have been vapor deposited 
onto film base are described in U.S. Pat. No. 4,078,935. The resistivity 
of such conductive thin films has been reported to be 10.sup.5 
.OMEGA./.quadrature.. However, these metal oxide thin films are unsuitable 
for photographic film applications since the overall process used to 
prepare them is complex and expensive and adhesion of these thin films to 
the film base and overlying layers is poor. 
U.S. Pat. No. 4,203,769 describes an antistatic layer incorporating 
"amorphous" vanadium pentoxide. This vanadium pentoxide antistat is highly 
entangled, high aspect ratio ribbons 50-100 Angstroms wide, about 10 
Angstroms thick, and 0.1-1 .mu.m long. As a result of this ribbon 
structure surface resistivities of 10.sup.6- 10.sup.11 
.OMEGA./.quadrature. can be obtained for coatings containing very low 
volume fractions of vanadium pentoxide. This results in very low optical 
absorption and scattering losses, thus the coatings are highly transparent 
and colorless. However, vanadium pentoxide is soluble at the high pH 
typical of film developer solutions and must be overcoated with a 
nonpermeable barrier layer to maintain antistatic performance after film 
processing. 
It can be seen that a variety of methods have been reported in an attempt 
to obtain non-brittle, adherent, highly transparent, colorless conductive 
coatings with humidity independent, film process surviving antistatic 
performance. However, the aforementioned prior art references are 
deficient with regard to simultaneously satisfying all of the above 
mentioned requirements. 
U.S. Pat. No. 5,340,676 describes conductive layers comprising 
electrically-conductive fine particles, hydrophilic colloid, and 
water-insoluble polymer particles. Representative polymer particles 
described include polymers and interpolymers of styrene, styrene 
derivatives, alkyl acrylates or alkyl methacrylates and their derivatives, 
olefins, vinylidene chloride, acrylonitrile, acrylamide and methacrylamide 
and their derivatives, vinyl esters, vinyl ethers, or condensation 
polymers such as polyurethanes and polyesters. The use of a mixed binder 
comprising the polymer particles mentioned above in combination with a 
hydrophilic colloid such as gelatin provides a conductive coating that 
requires lower volume % conductive fine particles compared with a layer 
obtained from a coating composition comprising the conductive fine 
particles and water soluble hydrophilic colloid alone. 
It is toward the objective of providing improved imaging elements having 
enhanced properties in comparison with the imaging elements of U.S. Pat. 
No. 5,340,676 that the present invention is directed. 
SUMMARY OF THE INVENTION 
In accordance with this invention, an imaging element for use in an 
image-forming process comprises a support, an image-forming layer, and an 
electrically-conductive layer. The electrically-conductive layer comprises 
electronically-conductive fine particles and gelatin-coated 
water-insoluble polymer particles. The combination of 
electronically-conductive fine particles and gelatin-coated 
water-insoluble polymer particles provides conductive coatings which can 
employ low volume percentages of conductive particles and still provide 
the desired high degree of conductivity. The coatings strongly adhere to 
underlying and overlying layers such as photographic support materials and 
hydrophilic colloid layers. 
In comparison with U.S. Pat. No. 5,340,676, the binder for the 
electronically-conductive fine particles comprises gelatin-coated 
water-insoluble polymer particles rather than a mixture of water-insoluble 
polymer particles and a hydrophilic colloid such as gelatin. The use of 
gelatin-coated water-insoluble polymer particles provides much better 
coating solution stability. Moreover, the electrically-conductive layer 
has significantly enhanced wet abrasion properties as compared with the 
electrically-conductive layer of U.S. Pat. No. 5,340,676, while still 
providing the benefits of reduced volume % of conductive fine particles as 
described in the '676 patent. 
Electrically-conductive layers comprising electronically-conductive fine 
particles, a film-forming hydrophilic colloid and pre-crosslinked gelatin 
particles also provide a highly advantageous combination of 
characteristics. Such layers are described in copending commonly-assigned 
U.S. patent application Ser. No. 330,409, filed Oct. 28, 1994, "Imaging 
Element Comprising An Electrically-Conductive Layer Containing Conductive 
Fine Particles, A Film-Forming Hydrophilic Colloid And Pre-Crosslinked 
Gelatin Particles" by Charles C. Anderson, Yoncai Wang, James L. Bello, 
Ibrahim M. Shalhoub and Douglas D. Corbin. The combination of hydrophilic 
colloid and pre-crosslinked gelatin particles as a binder for the 
electronically-conductive fine particles provides the benefit of reduced 
volume % of conductive fine particles and good coating solution stability. 
The gelatin-coated water-insoluble polymer particles employed as the 
binder in the present invention provide similar benefits to the 
pre-crosslinked gelatin particles but the particles in the present 
invention are more easily prepared and dispersed and their size and size 
distribution are more readily controlled.

DETAILED DESCRIPTION OF THE INVENTION 
The imaging elements of this invention can be of many different types 
depending on the particular use for which they are intended. Such elements 
include, for example, photographic, electrostatographic, 
photothermographic, migration, electrothermographic, dielectric recording 
and thermal-dye-transfer imaging elements. 
Details with respect to the composition and function of a wide variety of 
different imaging elements are provided in U.S. Pat. No. 5,340,676 and 
references described therein. The present invention can be effectively 
employed in conjunction with any of the imaging elements described in the 
'676 patent. 
Photographic elements represent an important class of imaging elements 
within the scope of the present invention. In such elements, the 
electrically-conductive layer can be applied as a subbing layer, as an 
intermediate layer, or as the outermost layer on the sensitized emulsion 
side of the support, on the side of the support opposite the emulsion, or 
on both sides of the support. When the electrically-conductive layer is on 
the side of the support opposite to the emulsion layer, it can be 
overcoated with an anti-curl layer. The support may comprise any commonly 
used photographic support material such as polyester, cellulose acetate, 
or resin-coated paper. The electrically-conductive layer is applied from a 
coating formulation comprising essentially electronically-conductive fine 
particles and gelatin-coated, water-insoluble polymer particles. The 
conductive particle can be, for example, a doped-metal oxide, a metal 
oxide containing oxygen deficiencies, a metal antimonate, or a conductive 
nitride, carbide, or boride. Representative examples of conductive fine 
particles include conductive TiO.sub.2, SnO.sub.2, Al.sub.2 O.sub.3, 
ZrO.sub.3, In.sub.2 O.sub.3, MgO, ZnSb.sub.2 O.sub.6, InSbO.sub.4, 
TiB.sub.2, ZrB.sub.2, NbB.sub.2, TAB.sub.2, CrB.sub.2, MoB, WB, LAB.sub.6, 
ZrN, TiN, TiC, and WC. The conductive fine particles typically have an 
average particle size less than about 0.3 .mu.m and a powder resistivity 
of 10.sup.5 .OMEGA..multidot. cm or less. 
The gelatin-coated, water-insoluble polymer particles utilized in this 
invention preferably have an average diameter of about 10 nm to about 1000 
nm. More preferably, the particles have an average diameter of 20 to 500 
nm. The gelatin can be any of the types of gelatin known in the 
photographic art. These include, for example, alkali-treated gelatin 
(cattle bone or hide gelatin), acid-treated gelatin (pigskin or bone 
gelatin), and gelatin derivatives such as partially phthalated gelatin, 
acetylated gelatin, and the like. 
The polymer particle coated with gelatin is a water-dispersible, nonionic 
or anionic polymer or interpolymer prepared by emulsion polymerization of 
ethylenically unsaturated monomers or by post emulsification of preformed 
polymers. In the latter case, the preformed polymers may be first 
dissolved in an organic solvent and then the polymer solution emulsified 
in an aqueous media in the presence of an appropriate emulsifier. 
Representative polymer particles include those comprising polymers and 
interpolymers of styrene, styrene derivatives, alkyl acrylates or alkyl 
methacrylates and their derivatives, olefins, vinylidene chloride, 
acrylonitrile, acrylamide and methacrylamide and their derivatives, vinyl 
esters, vinyl ethers and urethanes. In addition, crosslinking monomers 
such as 1,4-butyleneglycol methacrylate, trimethylolpropane. triacrylate, 
allyl methacrylate, diallyl phthalate, divinyl benzene, and the like may 
be used in order to give a crosslinked polymer particle. The glass 
transition temperature (T.sub.g) of the polymer particle may vary widely, 
but, most preferably the Tg should be at least 20.degree. C. to provide 
the greatest reduction in the volume % of conductive particle required in 
conductive coating compositions. The polymer particle may be a core-shell 
particle as described, for example, in U.S. Pat. No. 4,497,917. The 
gelatin-coated polymer particle can be prepared either by having at least 
a part of its emulsion polymerization conducted in the presence of gelatin 
and/or by adding gelatin and a crosslinking agent after completion of the 
emulsion polymerization or post emulsification in order to link the 
polymer particle and gelatin through the crosslinking agent. 
Gelatin-coated polymer particles have been described in the photographic 
art. U.S. Pat. No. 2,956,884 describes the preparation of polymer latices 
in the presence of gelatin and the application of such materials in 
photographic emulsion and subbing layers. U.S. Pat. No. 5,330,885 
describes a silver halide photographic imaging element containing a 
photographic emulsion layer, emulsion overcoat, backing layer, and backing 
layer overcoat in which at least one layer contains a polymer latex made 
in the presence of gelatin. U.S. Pat. No. 5,374,498 describes a 
hydrophilic colloid layer provided on the photographic emulsion layer side 
of the support that contains a latex comprising polymer particles 
stabilized with gelatin. U.S. Pat. Nos. 5,066,572 and 5,248,558 describe 
case-hardened gelatin-grafted soft polymer particles that are incorporated 
into photographic emulsion layers to reduce pressure sensitivity. Although 
the abovementioned prior art references describe layers containing 
gelatin-coated or gelatin-containing polymer particles they do not 
disclose the use of these particles in conductive layers or suggest the 
benefits with respect to solution stability or reduction in volume % 
conductive fine particles taught in the present invention. 
The gelatin/polymer weight ratio of the gelatin-coated polymer particle is 
preferably 5/95 to 40/60. At gelatin/polymer ratios less than 5/95 the 
polymer particle is not sufficiently coated with gelatin to provide the 
improvements in solution stability and wet abrasion properties and for 
ratios greater than 40/60 there is insufficient polymer particle to 
provide the desired reduction in volume % conductive particles required in 
the conductive coating. 
The conductive layer preferably comprises 50 volume % or less of the 
conductive fine particles, more preferably the conductive layer comprises 
35 volume % or less of the conductive fine particles. The amount of the 
conductive particle contained in the coating is defined in terms of volume 
% rather than weight % since the densities of the conductive particles and 
polymer binders may differ widely. The binder for the conductive particles 
comprises the gelatin-coated polymer particles and, optionally, up to 20 
weight % (based on the total dry weight of the gelatin-coated polymer 
particles) additional gelatin. The conductive layer can additionally 
contain wetting aids, matte particles, biocides, dispersing aids, 
hardeners, and antihalation dyes. The conductive layer is applied from an 
aqueous coating formulation to give dry coating weights which are 
preferably in the range of about 100 to about 1500 mg/m.sup.2. 
In a particularly preferred embodiment, the imaging elements of this 
invention are photographic elements, such as photographic films, 
photographic papers or photographic glass plates, in which the 
image-forming layer is a radiation-sensitive silver halide emulsion layer. 
Such emulsion layers typically comprise a film-forming hydrophilic 
colloid. The most commonly used of these is gelatin and gelatin is a 
particularly preferred material for use in this invention. Useful gelatins 
include alkali-treated gelatin (cattle bone or hide gelatin), acid-treated 
gelatin (pigskin gelatin) and gelatin derivatives such as acetylated 
gelatin, phthalated gelatin and the like. Other hydrophilic colloids that 
can be utilized alone or in combination with gelatin include dextran, gum 
arabic, zein, casein, pectin, collagen derivatives, collodion, agar-agar, 
arrowroot, albumin, and the like. Still other useful hydrophilic colloids 
are water-soluble polyvinyl compounds such as polyvinyl alcohol, 
polyacrylamide, poly(vinylpyrrolidone), and the like. 
The photographic elements of the present invention can be simple 
black-and-white or monochrome elements comprising a support bearing a 
layer of light-sensitive silver halide emulsion or they can be multilayer 
and/or multicolor elements. 
Color photographic elements of this invention typically contain dye 
image-forming units sensitive to each of the three primary regions of the 
spectrum. Each unit can be comprised of a single silver halide emulsion 
layer or of multiple emulsion layers sensitive to a given region of the 
spectrum. The layers of the element, including the layers of the 
image-forming units, can be arranged in various orders as is well known in 
the art. 
A preferred photographic element according to this invention comprises a 
support bearing at least one blue-sensitive silver halide emulsion layer 
having associated therewith a yellow image dye-providing material, at 
least one green-sensitive silver halide emulsion layer having associated 
therewith a magenta image dye-providing material and at least one 
red-sensitive silver halide emulsion layer having associated therewith a 
cyan image dye-providing material. 
In addition to emulsion layers, the elements of the present invention can 
contain auxiliary layers conventional in photographic elements, such as 
overcoat layers, spacer layers, filter layers, interlayers, antihalation 
layers, pH lowering layers (sometimes referred to as acid layers and 
neutralizing layers); timing layers, opaque reflecting layers; opaque 
light-absorbing layers and the like. The support can be any suitable 
support used with photographic elements. Typical supports include 
polymeric films, paper (including polymer-coated paper), glass and the 
like. Details regarding supports and other layers of the photographic 
elements of this invention are contained in Research Disclosure, Item 
36544, September, 1994. 
The light-sensitive silver halide emulsions employed in the photographic 
elements of this invention can include coarse, regular or fine grain 
silver halide crystals or mixtures thereof and can be comprised of such 
silver halides as silver chloride, silver bromide, silver bromoiodide, 
silver chlorobromide, silver chloroiodide, silver chorobromoiodide, and 
mixtures thereof. The emulsions can be, for example, tabular grain 
light-sensitive silver halide emulsions. The emulsions can be 
negative-working or direct positive emulsions. They can form latent images 
predominantly on the surface of the silver halide grains or in the 
interior of the silver halide grains. They can be chemically and 
spectrally sensitized in accordance with usual practices. The emulsions 
typically will be gelatin emulsions although other hydrophilic colloids 
can be used in accordance with usual practice. Details regarding the 
silver halide emulsions are contained in Research Disclosure, Item 36544, 
September, 1994, and the references listed therein. 
The photographic silver halide emulsions utilized in this invention can 
contain other addenda conventional in the photographic art. Useful addenda 
are described, for example, in Research Disclosure, Item 36544, September, 
1994. Useful addenda include spectral sensitizing dyes, desensitizers, 
antifoggants, masking couplers, DIR couplers, DIR compounds, antistain 
agents, image dye stabilizers, absorbing materials such as filter dyes and 
UV absorbers, light-scattering materials, coating aids, plasticizers and 
lubricants, and the like. 
Depending upon the dye-image-providing material employed in the 
photographic element, it can be incorporated in the silver halide emulsion 
layer or in a separate layer associated with the emulsion layer. The 
dye-image-providing material can be any of a number known in the art, such 
as dye-forming couplers, bleachable dyes, dye developers and redox 
dye-releasers, and the particular one employed will depend on the nature 
of the element, and the type of image desired. 
Dye-image-providing materials employed with conventional color materials 
designed for processing with separate solutions are preferably dye-forming 
couplers; i.e., compounds which couple with oxidized developing agent to 
form a dye. Preferred couplers which form cyan dye images are phenols and 
naphthols. Preferred couplers which form magenta dye images are 
pyrazolones and pyrazolotriazoles. Preferred couplers which form yellow 
dye images are benzoylacetanilides and pivalylacetanilides. 
The invention is further illustrated by the following examples of its 
practice. 
PREATION OF GELATIN-COATED POLYMER TICLES 
A stirred reactor containing 1069 g of deionized water, 60.0 g of 
lime-processed bone gelatin, and 6.0 g of 30% aqueous Triton 770 
surfactant (Rohm & Haas Co.) was heated to 80.degree. C. and purged with 
N.sub.2 for 1 hour. After addition of 0.45 g of potassium persulfate, an 
emulsion containing 150.0 g of deionized water, 176.4 g of ethyl acrylate, 
3.6 g of sodium styrene sulfonate, 27.0 g of 10% aqueous Olin 10G 
surfactant, 6.0 g of 30% aqueous Triton 770 surfactant, 0.3 g of sodium 
bicarbonate and 0.45 g of potassium persulfate was slowly added over a 
period of 1 hour. The reaction was allowed to continue for an additional 2 
hours. After the reaction was completed the gel-coated latex was purged 
with a N.sub.2 sweep for 30 minutes to remove any residual unreacted 
momoner. An additional 36.0 g of 10% aqueous Olin 10G surfactant was added 
and the gel-coated latex (designated particle P-1) was cooled to room 
temperature, filtered, and refrigerated. The total percent solids of the 
gel-coated latex was 14.5 weight % and the particle size using a light 
scattering technique was measured at 180 nm for the gel-coated particle 
and 62 nm for the particle in which the gelatin was removed by 
enzymolysis. The other gel-coated polymer particles used in the following 
examples were prepared in an analogous manner and their compositions are 
described in Table 1. 
TABLE 1 
______________________________________ 
Particle 
Gel/ Particle 
Size, nm 
Par- Polymer Size, nm 
(gel 
ticle 
Polymer Composition 
ratio Tg, .degree.C. 
(with gel) 
removed) 
______________________________________ 
P-1 ethyl acrylate/sodium 
25/75 -20 320 62 
styrene sulfonate 98/2 
P-2 ethyl methacrylate/ 
25/75 65 137 60 
sodium styrene 
sulfonate 99/1 
P-3 methyl methacrylate/ 
25/75 125 164 60 
sodium styrene 
sulfonate 98/2 
C-1 ethyl acrylate/sodium 
0/100 -20 -- 76* 
acrylamido-2-propane 
sulfonate/2-aceto- 
acetoxy ethyl 
methacrylate 
93.6/4.4/2 
C-2 ethyl methylacrylate/ 
0/100 65 -- 78* 
sodium acrylamido-2- 
propane sulfonate/2- 
acetoacetoxy ethyl 
methacrylate 
93.6/4.4/2 
C-3 methyl methacrylate/ 
0/100 125 -- 48* 
methacrylic acid 97/3 
______________________________________ 
*-these comparative particles were not made in the presence of gelatin. 
EXAMPLES 1-3 AND COMATIVE SAMPLES A-C 
Antistat coatings comprising conductive fine particles and polymer binder 
were coated onto 4 mil thick polyethylene terephthalate film support that 
had been subbed with a terpolymer latex of acrylonitrile, vinylidene 
chloride, and acrylic acid. The aqueous coating formulations comprising 
about 4 weight % total solids were dried at 120.degree. C. to give dried 
coating weights of 1000 mg/m.sup.2. The coating formulations contained; 
2.4 weight % of conductive tin oxide particles (doped with 6% antimony) 
with an average particle size of about 50 nm, 1.6 weight % of a polymer 
binder, 3 weight % of 2,3-dihydroxy-1,4-dioxane gelatin hardener based on 
the total weight of gelatin in the coating composition, and 0.01 weight % 
of Olin 10G surfactant. 
The surface resistivity of the coatings was measured at 20% relative 
humidity using a 2-point probe. The coating compositions and resistivities 
for the coatings are tabulated in Table 2. For purposes of comparison, 
results are also reported for Comparative Samples A to C in which either 
gelatin alone was used as the binder or the polymer particle and gel 
mixtures described in U.S. Pat. No. 5,340,676 were used as the binder. 
Coatings of the invention provide improved conductivity at low volume % of 
the conductive particle compared with those comprising only gelatin as the 
binder and the resistivities are comparable to the polymer particle and 
gel mixtures taught in U.S. Pat. No. 5,340,676. 
TABLE 2 
______________________________________ 
Surface 
Coating Volume Resistivity 
No. Binder % SnO.sub.2 
(.OMEGA./.quadrature.) 
______________________________________ 
Example P-1 20 5.0 .times. 10.sup.9 
Example P-2 20 4.0 .times. 10.sup.8 
2 
Example P-3 20 1.0 .times. 10.sup.9 
3 
Sample A gelatin 20 .sup. 4.0 .times. 10.sup.12 
Sample B 25/75 gelatin/C-1 
20 4.0 .times. 10.sup.9 
Sample C 25/75 gelatin/C-2 
20 4.0 .times. 10.sup.8 
______________________________________ 
Dry adhesion of the conductive layers to the support was determined by 
scribing small hatch marks in the coating with a razor blade, placing a 
piece of high tack tape over the scribed area and then quickly pulling the 
tape from the surface. The amount of the scribed area removed is a measure 
of the dry adhesion. Wet adhesion for the coatings was tested by placing 
the test samples in deionized water at 35.degree. C. for 1 minute. While 
still wet, a one millimeter wide line was scribed in the coating and a 
finger was rubbed vigorously across the scribe line. The percent of the 
rubbed area that was removed was used as a measure of wet adhesion. The 
adhesion results for Examples 1 and 2 that comprise gel-coated polymer 
particles and Samples B and C that comprise mixtures of gelatin with 
analogous non-gel-coated polymer particles are shown in Table 3. As can be 
seen, the wet adhesion for coatings of the invention is superior to the 
comparative samples featuring the binders taught in the '676 patent. 
TABLE 3 
______________________________________ 
Wet Adhesion 
Dry Adhesion 
Coating No. (% removed) 
(% removed) 
______________________________________ 
Example 1 10 0 
Example 2 10 0 
Sample B 50 0 
Sample C 100 0 
______________________________________ 
EXAMPLES 4-9 AND COMATIVE SAMPLES D AND E 
The following examples demonstrate the excellent solution stability for 
coating compositions of the invention. The following aqueous formulations 
were prepared and maintained at 45.degree. C. to evaluate their stability 
against flocculation at various times. The results are shown in Table 4. 
Solution 1: 2.00 weight % conductive tin oxide particles, 1.33 weight % 
P-1, 0.01 weight % 2,3-dihydroxy-1,4-dioxane, and 0.01 weight % Olin 10G 
surfactant and a balance of deionized water. 
Solution 2: 1.33 weight % conductive tin oxide particles, 2.00 weight % 
P-1, 0.015 weight % 2,3-dihydroxy-1,4-dioxane, and 0.01 weight % Olin 10G 
surfactant and a balance of deionized water. 
Solution 3: 2.00 weight % conductive tin oxide particles, 1.33 weight % 
P-2, 0.01 weight % 2,3-dihydroxy-1,4-dioxane, and 0.01 weight % Olin 10G 
surfactant and a balance of deionized water. 
Solution 4: 1.33 weight % conductive tin oxide particles, 2.00 weight % 
P-2, 0.015 weight % 2,3-dihydroxy-1,4-dioxane, and 0.01 weight % Olin 10G 
surfactant and a balance of deionized water. 
Solution 5: 2.00 weight % conductive tin oxide particles, 1.33 weight % 
P-3, 0.01 weight % 2,3-dihydroxy-1,4-dioxane, and 0.01 weight % Olin 10G 
surfactant and a balance of deionized water. 
Solution 6: 1.33 weight % conductive tin oxide particles, 2.00 weight % 
P-3, 0.015 weight % 2,3-dihydroxy-1,4-dioxane, and 0.01 weight % Olin 10G 
surfactant and a balance of deionized water. 
Solution 7: 2.00 weight % conductive tin oxide particles, 1.00 weight % 
C-3, 0.33 weight % gelatin, 0.01 weight % 2,3-dihydroxy-1,4-dioxane, and 
0.01 weight % Olin 10G surfactant and a balance of deionized water. 
Solution 8: 1.33 weight % conductive tin oxide particles, 1.50 weight % 
C-3, 0.50 weight % gelatin, 0.015 weight % 2,3-dihydroxy-1,4-dioxane, and 
0.01 weight % Olin 10G surfactant and a balance of deionized water. 
As shown in Table 4, the coating compositions of the invention have 
excellent stability even after aging for 48 hours. Coating compositions of 
comparative samples D and E comprising a binder that is a mixture of a 
latex particle and gelatin, rather than a gelatin-coated latex particle of 
the invention, exhibited a large amount of flocculation after 24 hours 
aging. 
TABLE 4 
______________________________________ 
Solution Stability, 
Stability, 
Stability, 
Sample # fresh 24 hrs 48 hrs 
______________________________________ 
Example 4 1 Excellent 
Excellent 
Excellent 
Example 5 2 Excellent 
Excellent 
Excellent 
Example 6 3 Excellent 
Excellent 
Excellent 
Example 7 4 Excellent 
Excellent 
Excellent 
Example 8 5 Excellent 
Excellent 
Excellent 
Example 9 6 Excellent 
Excellent 
Excellent 
Comparative Sample D 
7 Excellent 
Poor Poor 
Comparative Sample E 
8 Excellent 
Poor Poor 
______________________________________ 
As shown by the above examples, use of gelatin-coated water-insoluble 
polymer particles as a binder for electronically-conductive fine particles 
in electrically-conductive layers of imaging elements provides many 
important advantages. In particular, excellent conductivity is achieved at 
low volume percentages of electronically-conductive fine particles, the 
electrically-conductive layer has excellent abrasion resistant properties, 
and the coating compositions from which the electrically-conductive layer 
is formed can be easily prepared in a stable form. 
The invention has been described in detail, with particular reference to 
certain preferred embodiments thereof, but it should be understood that 
variations and modifications can be effected within the spirit and scope 
of the invention.