Electrically conductive toner powder

An electrically conductive toner powder, the separate particles of which contain thermoplastic resin, additives conventional in toner powders, such as coloring constituents and possibly magnetically attractable material, and an electrically conductive protonized polyaniline complex, the protonized polyaniline complex preferably having an electrical conductivity of at least 1 S/cm, the conductive complex being distributed over the volume of the toner particles or is present in a polymer-matrix at the surface of the toner particles.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an image development toner powder and, more 
specifically, to a toner powder which is utilized in the development of 
electrostatic, electrophotographic and magnetographic images. 
2. Discussion of Related Art 
In electrostatography and electrophotography it is known to form a visible 
image by using electrically conductive toner powder having a resistivity 
of less than 10.sup.12 .OMEGA..cm, preferably between 10.sup.4 and 
10.sup.9 .OMEGA..cm, measured as described in Example 1 of UK patent 
1,406,983. Examples of image-forming processes in which such electrically 
conductive toner powder is used will be found inter alia in the above 
mentioned UK patent 1,406,983, European patent 0,310,209 and U.S. Pat. No. 
3,563,734. 
Electrically conductive magnetically attractable toner powders can also be 
advantageously used in magnetographic image-forming processes, as 
described inter alia in U.S. Pat. No. 5,154,944. 
Electrically conductive toner powders usually consist of thermoplastic 
resin particles in which additives, such as coloring constituents and 
possibly magnetically attractable material, are present in finely divided 
or dissolved form and which contain electrically conductive material 
distributed over the volume of the particles and/or applied to or just 
beneath the surface of the particles. One electrically conductive material 
which is frequently used is carbon, the carbon particles preferably being 
affixed to the surface of the toner particles or being embedded completely 
or partially in the surface thereof. At the same time the carbon particles 
act as a coloring constituent. Examples of these toner powders are 
described in UK patent 1,406,983 and U.S. Pat. No. 3,639,245. For 
electrically conductive colored toner powders, use is made of electrically 
conductive colorless, relatively transparent substances, for example tin 
oxide which, to increase the electrical conductivity, is doped with 
antimony or fluorine. In this case too, the conductive material is 
preferably deposited on the surface of the toner particles. See published 
European patent application 0,441,426. 
Deposition of the conductive powder material on the surface of the toner 
particles has the advantage that relatively little material is required, 
usually not more than 8% by weight, to achieve the required electrical 
conductivity. In the preparation of the toner powder it is necessary to 
ensure that virtually no loose conductive powder, i.e. not adhering to the 
surface, is present. The fine conductive powder can be deposited on the 
image-recording element, e.g., photoconductive or dielectric surface, so 
that the span of life thereof is greatly reduced. If the conductive powder 
is distributed over the volume of the toner particles, the required 
electrical conductivity is often only achieved at weight percentages of 
conductive powder of more than 25. These large quantities of conductive 
powder in turn have an adverse effect on the heat-fixing properties of the 
toner powder. 
SUMMARY OF THE INVENTION 
Therefore, the object of the present invention is to provide an 
electrically conductive toner powder which will overcome the above-noted 
disadvantages. 
The present invention relates to a toner powder which, in addition to a 
thermoplastic binder and other additives conventional in toner powders, 
e.g., magnetically attractable material and/or coloring constituents, 
contain electrically conductive material to give the toner powder the 
required electrical conductivity so that it can be deposited on a charge 
or potential pattern by inductive attraction. More specifically, the 
electrically conductive toner contains a complex of a polyaniline and a 
protonizing acid as conductive material.

DETAILED DISCUSSION OF THE INVENTION 
The toner powder according to the present invention contains conductive 
material in the form of a polymeric compound deposited in a thin 
polymer-matrix on the surface of the toner particles or distributed as a 
conductive matrix in the volume of the toner particles. Suitable 
polyanilines and complexing protonizing acids which can be used in 
combination therewith are described in International patent application WO 
92/22911. Suitable polyanilines are those according to anyone of the 
general formulas I, II, III or IV: 
##STR1## 
wherein n is an integer from 0-4 
m is an integer from 0-4 with the proviso that the sum of n+m equals 4 
y is an integer equal to or greater than 0 
x is an integer equal to or greater than 1, with the proviso that x+y is 
greater than 1 
z is an integer equal to or greater than 1. 
R is independently selected so as to be the same or different at each 
occurrence and is selected from the group consisting of alkyl, alkenyl, 
alkoxy, cycloalkyl, cycloalkenyl, alkanoyl, alkylthio, aryloxy, 
alkylthloalkyl, alkylaryl, arylalkyl, amino, alkylamino, dialkylamino, 
aryl, alkylsulfinyl, alkoxyalkyl, alkylsulfonyl, arylthio, arylsulfinyl, 
alkoxycarbonyl, arylsulfonyl, carboxylic acid, halogen, cyano, or alkyl 
substituted with one or more sulfonic acid, carboxylic acid, halogen, 
nitro, cyano or epoxy moieties; or any two R groups together may form an 
alkylene or alkenylene chain completing a 3, 4, 5, 6 or 7 membered 
aromatic or alicyclic ring, which ring may optionally include one or more 
divalent nitrogen, sulfur or oxygen atoms. 
Suitable protonizing acids are those of formulas V and VI 
##STR2## 
wherein: 
A is sulfonic acid, selenic acid, phosphonic acid, boric acid or a 
carboxylic acid group; or hydrogen sulfate, hydrogen selenate, hydrogen 
phosphate; 
n.sub.1 is an integer from 0 to 5; 
m.sub.1 is an integer from 0 to 4 with the proviso that the sum of n+m is 
5; 
R.sub.1 is alkyl, alkenyl, alkoxy, alkanoyl, alkylthio, alkylthioalkyl, 
having from 1 to about 20 carbon atoms; or alkylaryl, arylalkyl, 
alkylsulfinyl, alkoxyalkyl, alkylsufonyl, alkoxycarbonyl, carboxylic acid, 
where the alkyl or alkoxy has from 0 to about 20 carbon atoms; or alkyl 
having from 3 to about 20 carbon atoms substituted with one or more 
sulfonic acid, carboxylic acid, halogen, nitro, cyano, diazo, or epoxy 
moieties; or a substituted or unsubstituted 3, 4, 5, 6 or 7 membered 
aromatic or alicyclic carbon ring, which ring may include one or more 
divalent heteroatoms of nitrogen, sulfur, sulfinyl, sulfonyl or oxygen 
such as thiophenyl, pyrolyl, furanyl, pyridinyl. In addition to these 
monomeric acid forms, R.sub.1 can be a polymeric backbone from which 
depend a plurality of acid functions "A". Examples of polymeric acids 
include sulfonated polystyrene, sulfonated polyethylene and the like. In 
these cases the polymer backbone can be selected either to enhance 
solubility in nonpolar substrates or be soluble in more highly polar 
substrates in which materials such as polymers, polyacrylic acid or 
poly(vinylsulfonate), or the like, can be used. 
R.sub.2 is the same or different at each occurrence and is alkyl, alkenyl, 
alkoxy, cycloalkyl, cycloalkenyl, alkanoyl, alkylthio, aryloxy, 
alkylthioalkyl, alkylaryl, arylalkyl, alkylsulfinyl, alkoxyalkyl, 
alkylsufonyl, aryl, arylthio, arylsuffinyl, alkoxycarbonyl, arylsulfonyl, 
carboxylic acid, halogen, cyano, or alkyl substituted with one or more 
sulfonic acid, carboxylic acid, halogen, nitro, cyano or epoxy moieties; 
or any two R substituents taken together are an alkylene or alkenylene 
group completing a 3, 4, 5, 6 or 7 membered aromatic or alicyclic carbon 
ring or multiples thereof, which ring or rings may include one or more 
divalent heteroatoms of nitrogen, sulfur, sulfinyl, sulfonyl or oxygen. 
R.sub.2 typically has from about 1 to about 20 carbons, preferably 3 to 20 
and more preferably from about 8 to 20 carbons. 
Preferred for use in the practice of this invention are functionalized 
protonic acid solutes of the above Formulas V and VI in which: 
A is sulfonic acid, phosphonic acid or carboxylic acid; 
n.sub.1 is an integer from 1 to 5; 
m.sub.1 is an integer from 0 to 4 with the proviso that the sum of n+m=5; 
R.sub.1 is alkyl, alkenyl, alkoxy, alkylthio, alkylthioalkyl, having from 5 
to about 16 carbon atoms; or alkylaryl, arylalkyl, alkylsulfinyl, 
alkoxyalkyl, alkylsulfonyl, alkoxycarbonyl, carboxylic acid where the 
alkyl or alkoxy has from 1 to about 20 carbon atoms; or alkyl having from 
3 to about 20 carbon atoms substituted with one or more sulfonic acid, 
carboxylic acid, halogen, nitro, cyano, diazo, or epoxy moieties; 
R.sub.2 is the same or different at each occurrence and is alkyl, alkenyl, 
alkoxy, arylalkyl, alkylsulfinyl, alkoxycarbonyl or carboxylic acid having 
from 3 to 12 carbon atoms, or alkyl substituted with one or more 
carboxylic acid, halogen, diazo or epoxy moieties. 
Among the materials mentioned for use in toner powder according to the 
invention, the protonized polyanilines having a conductivity of more than 
1 S/cm have proved to be particularly suitable. Examples of such 
protonized polyanilines are polyaniline emeraldine salt protonized with 
methanesulfonic acid (71 S/cm); ethane sulfonic acid (35.5 S/cm); (L,D) 
camphor sulfonic acid (2.7 S/cm); p-toluene sulfonic acid (22 S/cm); 
4-dodecyl benzene sulfonic acid; p-hydroxybenzene sulfonic acid (6.3 
S/cm); bis (2-ethyl lexyl hydrogen phosphate (7 S/cm). The choice of 
conductive polyaniline complex is also determined by the thermoplastic 
resin or resin mixture used as the main constituent or binder of the toner 
powder. 
Of course, a polyaniline complex should be used that is compatible with the 
toner resin (or the toner resin mixture) and preferably a polyaniline 
complex is used which can be so finely distributed in a melt of the toner 
resin as to give a conductive end product. Thus, given the correct choice 
of the polyaniline complex, the toner powder according to the present 
invention can be prepared in a simple manner by melting the thermoplastic 
resin or resins forming the main constituent of the toner powder and 
distributing, in the melt, the required additives, such as magnetizable 
material and/or coloring constituents, together with the protonized 
complex of the polyaniline and protonizing acid. After cooling of the 
melt, the material is ground to give toner particles of the required 
particle size. 
In combination with epoxy and phenoxy resins, polyester resins derived from 
an alkoxylated bisphenol and a dicarboxylic acid, such as fumaric acid, 
and mixtures of epoxy and polyester resins, which are frequently used in 
toner powders, polyaniline complexes of polyaniline emeraldine, protonized 
with camphor sulphonic acid or dodecylbenzene sulphonic acid, are 
particularly attractive. 
Apart from mixing in the resin melt, toner powders according to the 
invention can be produced by dissolving the thermoplastic resin in a 
suitable, preferably polar, solvent, distributing the protonized 
polyaniline complex, or the polyaniline and protonizing acid, in the 
solution, then distributing the other additives in the liquid, and then 
evaporating the solvent and grinding the solid material to give toner 
particles of the required size. An alternative to evaporating the solvent 
and grinding the solid is spray-drying of the dispersion. 
Volume-conducting toner powders can be prepared in the above-described 
manner with only 5-10% by weight of polyaniline complex being required to 
achieve the required electrical resistivity of the toner powder (usually 
between 10.sup.4 -10.sup.9 .OMEGA..cm). In this way, according to the 
invention, toner powders having good heat-fixing properties are obtained. 
A toner powder can also be prepared by preparing thermoplastic resin cores 
in which the additives, including magnetizable material and coloring 
material, are finely distributed and then coating these thermoplastic 
resin cores with a conductive polymer-matrix, preferably consisting of 
5-10% by weight of a protonized polyaniline complex and 90-95% by weight 
of the same thermoplastic resin as present in the cores themselves. In 
this way surface-conductive toner powder is obtained which is free of fine 
electrically conductive powder dust. 
Since the protonized polyaniline complexes used according to the invention 
are practically colorless, they are particularly suitable for preparing 
electrically conductive colored toner powders. 
PREFERRED EMBODIMENTS 
The following examples are intended to illustrate, but not limit, the 
subject matter of the present invention. 
EXAMPLE 1 
100 g of polyester resin (Atlac 500 T of ICI, England) are melted, 
whereupon there are added to the melt and distributed thoroughly therein 9 
g of protonized complex of polyaniline emeraldine and camphor sulphonic 
acid, prepared as described below. The following are then added to and 
homogeneously distributed in the melt: 33g of magnetizable pigment (type 
Bayferrox B 318 M of Bayer AG, Germany). After cooling, the solid mass is 
ground and sifted, particles having a size of between 10 and 25 
micrometers being separated. The resulting toner powder had a resistivity 
of about 10.sup.8 .OMEGA..cm and was usable with good results for magnetic 
brush development of latent charge images formed on a photoconductor 
element. 
Preparation of the Protonized Polyaniline Complex 
Polyaniline was prepared according to the method described by Y. Cao, A. 
Andereatta, A. J. Heeger and P. Smith, Polymer, 30 (1989) 2305: A solution 
of 40 ml of freshly distilled aniline (Aldrich), 50 ml of 35% HCI (Fisher) 
and 400 ml distilled water was prepared in an 1 L Erlenmeyer flask. The 
flask was placed in a cooling bath maintained at 0.degree. C. 
Polymerization was effected by addition of an oxidant solution consisting 
of 46 g of (NH.sub.4).sub.2 S.sub.2 O.sub.8 (Aldrich) and 100 ml of 
distilled water. After all oxidant was added (2 hrs.), the flask was 
capped and left stirring for an additional 3 hours. The precipitated 
polymer powder was recovered, filtered and washed with distilled water 
until the pH of the washing liquid was 6-7. Subsequently, the polymer was 
washed with methanol until the liquid was clear, and then with ethyl ether 
to eliminate residual water and methanol. 
Finally, the polymer was dried in a vacuum at room temperature for 48 
hours. Emeraldine base form of polyaniline was prepared by compensation of 
the polyaniline salt, 10 g of polyaniline salt was stirred with 1000 ml of 
3% NH.sub.4 OH solution during 2 hours at room temperature. The resulting 
emeraldine base was filtrated and washed by distilled water until the pH 
of washing liquid was 7-8. Subsequently, the polymer was washed by 
methanol until washing liquid was colorless and then, with methyl ether. 
The emeraldine base was dried in dynamic vacuum at room temperature for 48 
hours. The resulting polymer was insoluble in all common non-polar or 
weakly polar solvents, and of high molecular weight; the inherent 
viscosity of the non-conducting polyaniline measured at 25.degree. C. in 
97% sulfuric acid, 0.1% w/w, was 1.2 dL/g. 
The non-conductive form of polyaniline, 5.43 g (0.06M of aniline), was 
mixed thoroughly with 6.96 g (0.03 M of (.+-.) --10-- camphor sulfonic 
acid (DSA) (Aldrich) using an agate mortar and pestle in a dry bag filled 
with nitrogen. The molar ratio of CSA to aniline repeat unit was 0.5; 
sufficient to completely protonate the emeraldine base form into the 
conducting salt form. 
EXAMPLE 2 
160 g of polyester resin as used in Example 1 were melted, whereupon the 
following were homogeneously distributed in the melt: 
20 g carbonyl iron having on average a particle size of about 3 micrometers 
2.4 g Astra Phloxine 
0.8 g Basonyl Rot 560-perchlorate 
3.2 g Macrolex Fluorescent Yellow 10 GN. 
After cooling, the mass was ground and sifted, particles having a size of 
between .+-.10 and .+-.20 micrometers being separated. The resulting cores 
were rapidly added with agitation to a solution of the following: 
20 g polyester resin (Atlac 500T) 
1.2 g complex of polyaniline and dodecylbenzenesulfonic acid, was prepared 
as described in Example 1; however, 9.79 g of dodecylbenzenesulfonic acid 
in place of 6.96 of CSA was used. 
0.4 g Basonyl Rot 560-perchlorate 
150 ml o-Cresol 
The dispersion was then spray-dried. This gave toner powder of a red color 
with a resistivity of about 10.sup.7 .OMEGA..cm. 
The present invention being thus described, it will be obvious that the 
same may be varied in many ways. Such variations are not to be regarded as 
a departure from the spirit and scope of the invention, and all such 
modifications as would be obvious to one skilled in the art are intended 
to be included within the scope of the following claims.