CA1046330A - Photoconductive composition and elements with a styryl amino group containing photoconductor - Google Patents

Abstract

Abstract of the Disclosure A novel photoconductive composition and electro-photographic elements containing the same are prepared using as a photoconductor a compound having a central carbocyclic or sulfur heterocyclic divalent aromatic ring joined to two amino-substituted styryl radicals through the vinylene groups of the styryl radicals.

Description

104~j330 Field of the Invention This invention relates to electrophotography and in particular to photoconductive compositions and elements.
Description of the Prior Art The process of xerography, as disclosed by Carlson in U.S. Patent No. 2,297,691, employs an electrophotographic element comprising a support material bearing a coating of an insulating material whose electrical resistance varies with the amount of incident electromagnetic radiation it receives during an imagewise exposure. The element, commonly termed a photoconductive element, is first given a uniform surface charge, generally in the dark after a suitable period of dark adaptation. It is then exposed to a pattern of actinic radiation which has the effect of differentially reducing the potential of this surface charge in accordance with the relative energy contained in various parts of the radiation pattern. The differential surface charge or electrostatic latent image remaining on the electrophotograph-ic element is then made visible by contacting the surface with a suitable electroscopic marking material. Such marking material or toner, whether contained in an insulating liquid or on a dry carrier, can be deposited on the exposed surface in accordance with either the charge pattern or discharge pattern as desired. Deposited marking material can then be either permanently fixed to the surface of the sensitive element by known means such as heat, pressure, solvent vapor or the like, or transferred to a second element to which it can similarly be fixed. Lik~wise, the electrostatic charge pattern can be transferred to a second element and developed there.
Various photoconductive insulating materials have been employed in the manufacture of electrophotographic ele-ments. For example, vapors of selenium and vapors of sel-enium alloys deposited on a suitable support and particles of photoconductive zinc oxide held in a resinous, film-form-ing binder have found wide application in present-day document copying processes.
Since the introduction of electrophotography, a great many organic compounds have also been screened for their photoconductive properties. As a result, a very large number of organic compounds have been known to possess some degree of photoconductivity. Many organic compounds have revealed a useful level of photoconduction and have been in-corporated into photoconductive compositions. Among these organic photoconductors are the triphenylamines as described in U.S. 3,180,730 issued April 27, 1965, and other aromatic ring compounds such as those described in British Patent 944,326 dated December 11, 1963; U.S. 3,549,358 issued December 22, 1970 and U.S. 3,653,887 issued April 4, 1972.
Optically clear organic photoconductor-containing elements having desirable electrophotographic properties can be especially useful in electrophotography. Such electrophoto-graphic elements can be exposed through a transparent base if desired, thereby providing flexibility in equipment design.
Such compositions, when coated as a film or layer on a suit- .-able support, also yield an element which is reusable; that is, it can be used to form subsequent images after residual toner from prior images has been removed by transfer and/or cleaning. Thus far, the selection of various compounds for incorporation into photoconductive compositions to form electrophotographic layers has proceeded on a compound-by-compound basis. Nothing as yet has been discovered from the large number of different photoconductive substances tested which permits effective prediction, and therefore selection of the particular compounds exhibiting the desired electro-photographic properties.
A high speed "heterogeneous" or "aggregate" multi-phase photoconductive system was developed by William A. Light which overcomes many of the problems of the prior art. This aggregate photoconductive composition (as it is referred to hereinafter) is the subject matter of U.S. Patent No. 3,615,414 issued October 26, 1971. The addenda disclosed therein are responsible for the exhibition of desirable electrophoto-graphic properties in photoconductive elements prepared there-with. In particular, they have been found to enhance the speed of many organic photoconductors when used therewith.
The degree of such enhancement is, however, variable, depend- ~ `
ing on the particular organic photoconductor so used.
Summary of the ~vention In accord with the present invention there is provided a novel photoconductive composition comprising as a photo-conductor a compound having a central carbocyclic or sulfur heterocyclic divalent aromatic ring joined to two amino-substituted styryl radicals through the vinylene groups of the styryl radicals.
In accord with one embodiment of the invention, we have found that the distyryl-containing aromatic compounds may be used as the photoconductive material of a homogeneous organic photoconductive conductive composition.
In accord with another embodiment of the present invention, it has been discovered that one or more of these distyryl-containing aromatic compounds may be employed as the ~0 only organic photoconductor in the continuous polymer phase of a multiphase aggregate photoconductive composition of -the type referred to hereinabove to extend the white light speed and blue sensitivity of the aggregate photoconductive composition.
In accord with still another embodiment of the in-vention, we have found that the distyryl-containing aromatic compounds may be incorporated as a photoconductive material in a photoconductive composition which also contains one or more inorganic photoconductors. For example, photoconductive compositions comprising a mixture of the above-described distyryl-containing aromatic compounds and lead oxide provide elements exhibiting useful xeroradiographic properties.
Various closely related compounds having a cyano-substituted vinylene moiety in place of the unsubstituted viny-lene moieties contained in the photoconductive compounds used in the present invention have been described in the prior art. Representative of such prior art materials are compounds having the following formula:

CN CN
Am ~ CH=C - Ar C=CH ~ Am wherein Am represents an amino group and Ar represents a divalent aromatic group. See Merrill, U.S. 3,653,887 issued April 4, 1972.
According to the present invention, it has been found that the photoconductors described herein have substan-tially improved electrical speed over those related photo-conductors described in U.S. 3,653,887.
In addition, it has been found that the photoconduc-tors of the present invention enhance the blue sensitivity of aggregate photoconductive compositions in comparison to the use of other known prior art compounds employed in similar agqregate photoconductive compositions, for example the 10~330 triarylamines shown in U.S. Patent No. 3,180,730 and certain of the active hydrogen-containing photoconductive materials shown in Brantley et. al., U.S. Patent No. 3,567,450.
Description of the Preferred Embodiments The preferred photoconductors of the invention may be characterized by the following formula:
R ~ R3 N-Arl-CH=CH-Ar2-CH=CH-Ar3-N~

wherein Rl, R2, R3, and R4, which can be the same or different, represent alkyl or aryl radicals including substi-tuted alkyl and aryl radicals;
Arl and Ar3, which can be the same or different, represent an unsubstituted or a substituted phenyl radical having one or more substituents selected from the group con-sisting of an alkyl, aryl, alkoxy, aryloxy and halogen sub-stituent; and Ar2 represents a carbocylic or sulfur heterocyclic, mononuclear or polynuclear, aromatic ring typically containing 4 to 14 carbon atoms in the ring such as phenyl, naphthyl and anthryl aromatic groups as well as substituted aromatic groups having one or more substituents selected from the group of substituents defined above as substituents for Ar and Ar3.
Typically, Rl, R2, R3, and R4 represent one of the following alkyl or aryl groups:
1. an alkyl group having one to 18 carbon atoms e.g., methyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl, etc. including a substituted alkyl group havin~ one to 18 carbon atoms such as . ' ' ' '' ' '~ . , ' ' . ' . ' :' "'. '' .' ,, ' ~' :

a. alkoxyalkyl e.g., ethoxypropyl, methoxybutyl, propoxymethyl, etc., b. aryloxyalkyl e.g., phenoxyethyl, naphthoxymethyl, phenoxypentyl, etc.
c. aminoalkyl, e.g., aminobutyl, aminoethyl, aminopropyl, etc., d. hydroxyalkyl e.g., hydroxypropyl, hydroxyoctyl, etc., e. aralkyl e.g., benzyl, phenethyl, etc.
f. alkylaminoalkyl e.g., methylaminopropyl, methyl aminoethyl, etc., and also including dialkyl-aminoethyl, e.g. diethyaminoethyl, dimethyl-aminopropyl, propylaminooctyl, etc., g. arylaminoalkyl, e.g., phenylaminoalkyl, diphenylaminoalkyl, N-phenyl-N-ethylaminopentyl, N-phenyl-N-ethylaminohexyl, naphthylaminomethyl, etc., h. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitro-pentyl, etc., i. cyanoalkyl, e.g., cyanopropyl, cyanobutyl, cyano-ethyl, etc., and j. haloalkyl, e.g., chloromethyl, bromopentyl, chlorooctyl, etc., k. alkyl substituted with an acyl group having the formula O
..
-C-R
wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc., lower alkyl having one to eight carbon atoms e.g., methyl, ethyl, propyl, etc., amino including substituted amino, e.g., diloweralkylamino, lower alkoxy having one to eight car- -bon atoms, e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, . :
.

naphthoxy, etc., or

2. an aryl group, e.g., phenyl, naphthyl, anthryl, fluorenyl, etc., including a substituted aryl group such as a. alkoxyaryl, e.g., ethoxyphenyl, methoxyphenyl, propoxynaphthyl, etc.
b. aryloxyaryl, e.g., phenoxyphenyl, naphthoxy-phenyl, phenoxynaphthyl, etc.
c. aminoaryl, e.g. aminophenyl, aminonaphthyl, aminoanthryl, etc.
d. hydroxyaryl, e.g., hydroxyphenyl, hydroxynaphthyl, hydroxyanthryl, etc.
e. biphenylyl, f. alkylaminoaryl, e.g., methylaminophenyl, methylaminonaphthyl, etc. and also including dialkylaminoaryl, e.g., diethylaminophenyl, dipropylaminophenyl, etc.
g. arylaminoaryl, e.g., phenylaminophenyl, diphenyl-aminophenyl, N-phenyl-N-ethylaminophenyl, naphthyl-aminophenyl, etc.
h. nitroaryl e.g., nitrophenyl, nitronaphtyly, nitroanthryl, etc., i. cyanoaryl, e.g., cyanophenyl, cyanonaphthyl, cyanoanthryl, etc., j. haloaryl, e.g., chlorophenyl, bromophenyl, chloronaphthyl, etc., k. alkaryl, e.g., totyl, ethylphenyl, propylnaphthyl, etc., and 1. aryl substituted with an acyl group having the formula O '~
-C-R
wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, : :

10~6330 etc., amino including substituted amino, e.g., diloweralkyl-amino, lower alkoxy having one to eight carbon atoms, e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy, etc., lower alkyl h~ing one to eight carbon atoms, e.g., methyl, ethyl, propyl, butyl, etc.
Typically, when either Arl or Ar3 represent a sub-stituted phenyl radical the substituents on the phenyl radical are al~yl or aryl groups as defined above for Rl, R2, R3, R4 or also any of the following: -1. an alkoxy group having one to 18 carbon atoms, e.g., methoxy, ethoxy, propoxy, butoxy, etc., 2. an aryloxy group e.g., phenoxy, naphthoxy, etc.;
and

3. halogen such as chlorine, bromine, fluorine or iodine.
Typical compounds which belong to the general class of photoconductive compounds described herein include the following materials listed in Table 1 below:

_ g _ ~, 10~6330 o o o o o o P~ ,, o ~ CO
~ ~ ~ o ~ O~
~ o ,, ~ o ,, ~ ~ ~ ,, _, o q~

~o .
O ~ ~1 ,1 al ~1 .C 1~ N ~ _ 0 O ~r ~ u a _, ~ ,1 m ~1 ~I~ "., ~I _ ~ Z ~
_l ~ P: ~ Z I I
_I ~D ~ I h ~ ~
~n 11 ~ P:
~1 ~ ~ ~C,~ ~ ~1 ~ ~ ~ ~ ~ m I ~ ~
o C~ ~I ~ C~ I C~
11 o I ~ ~ ~ / o ~ CJ ~ ~ 3 ~ ~ ~, ~ ` ~ ~ $~
,1 o ~ $ , ~ ~ ~ ~ ~ C~
11 s ~ ~ Z Z
' ~ ' ~ '~ r~
~, o . o ~ ~ ~ o . . , l .~s ~ ~ ~ ~ ~ ~

~ ~ ~ $
,~ I O ~ 0-,1 ~r o ~I c~ c~
Z I ~ I u~ D I - 5 s~U. I m~ I- ~, m I ~ ~
C~ , C~ ~rl --\
ac~ a ~ a ~ a ~ ~ ~ . .

H H H
-- H H H
H
-.
.' ' ' :' . ~.
- :
- :. - . , . : . - . ' . , :

10~6330 o~

'o o o o P~ U~ O ~D
~ a~ o b~ N N N
~ l l CO e~
~ ~ O
_I N N N
X ..

: .

,~ O N ~1 lQ ~ ~ ~U \ /
s '~, m~D ~ \mN >~
o m m~
~ .- ~ ~ Z s ~1 I s ~ ~ s ~r ~ m ,~
m n ~-) ~ N I 1~
~ _ _I m ~ ~ ~
_I I I ~ C~ o m~ PC~ ~ ~ P ~
m~ m~ ô ~ ~ m m c~
~-1 c~ o Q ~ ~ m 1l ~
N '~ U p, ~ 3 a m ~ z z _I O ~ C) -- N N Z ~ \ ~7 o ~ ~ m m I ~ / ~
~ m ~ m m~ m~ m ~ ~ \m a~
~r ~ ~ .

p ~ H H
H
~ 2 104t;330 Compounds which belong to the general class of photoconductive compounds described herein and which are preferred for use in accord with the present invention in-clude those compounds having the structural formula shown Rl, R2, R3, and R4 are aryl groups as defined above and wherein Ar2 is an unsubstituted phenyl radical or a substituted phenyl radical having alkyl substituents contain-ing 1 to about 4 carbon atoms. These compounds are preferred because of the generally higher electrical speeds which are obtained from photoconductive compositions containing the same.
Compounds which belong to the general class of photoconductive compounds described herein and which are especially preferred for use in accord with the present inven-tion include those compounds having the structural formula shown above wherein Rl, R2, R3, and R4 are alkaryl groups as defined above, particularly tolyl radicals, and wherein Arl, Ar2 and Ar3 are unsubstituted phenyl radicals or alkyl substituted phenyl radicals having no more than two alkyl substituents, said alkyl substituents containing 1 or 2 carbon atoms.
As set forth hereinabove, in accord with one embodi-ment of the invention, the photoconductive compounds of the invention can be used in aggregate photoconductive composi-tions of the present invention. Those distyryl-containing aro-matic compounds noted above as especially preferred have been found particularly useful in aggregate photoconductive composi-tions hecause ~ thEI~ a~ ity t6 i~G~e~se ~h~ ~l`ue sensitivityof t-~*se aggr~ga~e ~pQsii~ d~ àuse of their une~pected a~it~ ~o ina~ease~b~ peedi~ th~se aggregate composlticn3 in ~c~paæls~`~;.thæ-photccon~w tlve materia~s shown in U.S. Patent 3j~53~-887-which h~ve a very similar molecular structure.

. - ~ , . . ........................................ .

104t~.~30 The aggregate compositions used in this invention comprise an organic sensitizing dye and an electrically insulat-ing, film-forming polymeric material. They may be prepared by several techniques, such as, for example, the so-called "dye first" technique described in Gramza et al, U.S. 3,615,396 issued October 26, 1971. Alternatively, they may be prepared by the so-called "shearing" method described in Gramza, U.S. 3,615,415 issued October 26, 1971. This latter method involves the high speecl shearing of the photoconductive composition prior to coating and thus eliminates subsequent solvent treatment, as was disclosed in Light, U.S. 3,615,414 referred to above. By whatever method prepared, the aggregate composition is combined with the distyryl-containing photocon-ductor of the invention in a suitable solvent to form a photoconductor-containing composition which is coated on a suitable support to form a separately identifiable multiphase composition, the heterogeneous nature of which is generally apparent when viewed under magnification, although such com-positions may appear to be substantially optically clear to the naked eye in the absence of magnification. There can, of course, be macroscopic heterogeneity. Suitably, the dye-containing aggregate in the discontinuous phase is predominantly in the size range of from about 0.01 to about 25 microns.
In general, the aggregate compositions formed as described herein are multiphase organic solids containing dye and polymer. The polymer forms an amorphous matrix or continuous phase which contains a discrete discontinuous phase as distinguished from a solution. The discontinuous phase is the aggregate species which is a co-crystalline complex comprised of dye and polymer.
The term co-crystalline complex as used herein has reference to a crystalline compound which contains dye and .
.
, ~ :
~. . . .
.. : ..

polymer molecules co-crystallized in a single crystalline structure to form a regular array of the molecules in a three-dimensional pattern.
Another feature characteristic of the aggregate compositions formed as described herein is that the wave-length of the radiation absorption maximum characteristic of such compositions is substantially shifted from the wavelength of the radiation absorption maximum of a substantially homo-geneous dye-polymer solid solution formed of similar con-stituents. The new absorption maximum characteristic of the aggregates formed by this method is not necessarily an overall maximum for this system as this will depend upon the relative amount of dye in the aggregate. Such an absorption maximum shift in the formation of aggregate systems for the present invention is generally of the magnitude of atleast about 10 nm.
If mixtures of dyes are used, one dye may cause an absorption maximum shift to a long wavelength and another dye cause an absorption maximum shift to a shorter wavelength.
In such cases, a formation of the aggregate compositions can more easily be identified by viewing under magnification.
Sensitizing dyes and electrically insulating poly-meric materials are used in forming these aggregate composi-tions. Typically, pyrylium dyes, including pyrylium, bispyry-lium, thiapyrylium and selenapyrylium dye salts and also salts of pyrylium compounds containing condensed ring systems such as salts of benzopyrylium and naphthopyrylium dyes are useful in forming such compositions. Dyes from these classes which may be useful are disclosed in Light U.S. Patent No.
3,615,414.
Particularly useful dyes in forming the feature aggregates are pyrylium dye salts having the formula:

...... - . - . . .
. ~ ,: . , . - .

~ Z~

wherein:
R5 and R6 can each be phenyl radicals, including substituted phenyl radicals having at least one substituent chosen from alkyl radicals of from 1 to about 6 carbon atoms and alkoxy radicals having from 1 to about 6 carbon atoms;
R7 can be an alkylamino-substituted phenyl radical having from 1 to 6 carbon atoms in the alkyl moiety, and including dialkylamino-substituted and haloalkylamino-sub-stituted phenyl radicals;
X can be an oxygen or a sulfur atom; and Z~ is an anion.
The polymers useful in forming the aggregate com-positions include a variety of materials. Particularly use-ful are electrically insulating, film-forming polymers having an alkylidene diarylene moiety in a recurring unit such as those linear polymers, including copolymers, containing the following moiety in a recurring unit:

R8 IR9 IRl 1 ~} C--~R12 wherein:
Rg and Rlo, when taken separately, can each be a hydrogen atom, an alkyl radical having from one to about 10 carbon atoms such as methyl, ethyl, isobutyl, hexyl, heptyl, octyl, nonyl, decyl, and the like including substituted alkyl radicals such as trifluoromethyl, etc., and an aryl radical `` 10~6330 such as phenyl and naphthyl, including substituted aryl radi-cals having such substituents as a halogen atom, an alkyl radical of from 1 to about 5 carbon atoms, etc.; and Rg and Rlo, when taken together, can represent the carbon atoms necessary to complete a saturated cyclic hydrocarbon radical including cycloalkanes such as cyclohexyl and polycycloalkanes such as norbornyl, the total number of carbon atoms in Rg and Rlo being up to about 19;
R8 and Rll can each be hydrogen, an alkyl radical of from 1 to about 5 carbon atoms, e.g., or a halogen such as chloro, bromo, iodo, etc.; and R12 is a divalent radical selected from the fol-lowing:

O S O O O CH
1- .. - ,. " , 3 -O-C-O-, -O-C-O-, -C-O-, -C-O-CH2-, -C-O-CH-, O O
,. .. .
-CH2-O-C-O-, and -O-P-O-o~3 , .
Preferred polymers useful for forming aggregate crystals are hydrophobic carbonate polymers containing the following moiety in a recurring unit:

..
-R-C-R-O-C-O- - ~

Rlo ~ -20wherein:
each R is a phenylene radical including halo sub-stituted phenylene radicals and alkyl substituted phenylene radicals; and Rg and Rlo are as described above. Such compo-sitions are disclosed, for example in U.S. Patent Nos.
3,028,365 and 3,317,466. Preferably polycarbonates containing an alkylidene diarylene moiety in the recurring unit such as 104~330 those prepared with sisphenol A and including polymeric products of ester exchange between diphenylcarbonate and 2,2-bis-(4-hydroxyphenyl)propane are useful in the practice of this invention. Such compositions are disclosed in the following U.S. Patents: U.S. 2,999,750 by Miller et al, issued September 12, 1961, 3,038,874 by Laakso et al, issued June 12, 1962; 3,038,879 by Laakso et al, issued June 12, 1962;
3,038,880 by Laakso et al, issued June 12, 1962; 3~106,544 by Laakso et al, issued October 8, 1963; 3,106,545 by Laakso et al, issued October 8, 1963; and 3,106,546 by Laakso et al, issued October 8, 1963. A wide range of film-forming poly-carbonate resins are useful, with completely satisfactory results being obtained when using commercial polymeric materials which are characterized by an inherent viscosity of about 0.5 to about 1.8.
The following polymers are included among the materials useful in the practice of this invention:
Table 2 No. Polymeric Material 1 poly(4,4'-isopropylidenediphenylene-co-1,4-cyclohexanylenedimethylene carbonate) 2 poly(ethylenedioxy-3,3'-phenylene thiocarbonate) 3 poly(4,4'-isopropylidenediphenylene carbonate-co-terephthalate)

4 poly(4,4'-isopropylidenediphenylene carbonate) poly(4,4'-isopropylidenediphenylene thiocarbonate) 6 poly(4,4'-sec-butylidenediphenylene carbonate) 7 poly(4,4'-isopropylidenediphenylene carbonate-block-oxyethylene) 8 poly(4,4'-isopropylidenediphenylene carbonate-block-oxytetramethylene) `

10~33~
Table 2 (continued) No. _ Polymeric Material 9 poly[4,4'-isopropylidenebis(2-methyl-phenylene)-carbonate]
poly(4,4'-isopropylidenediphenylene-co-1,4-phenylene carbonate) . .
11 poly(4,4'-isopropylidenediphenylene-co-1,3-phenylene carbonate) 12 poly(4,4'-isopropylidenediphenylene-co-4,4'-diphenylene carbonate) 13 poly(4,4'-isopropylidenediphenylene-co-4,4'-oxydiphenylene carbonate) 14 poly(4,4'-isopropylidenediphenylene-co-4,4'-carbonyldiphenylene carbonate r poly(4,4'-isopropylidenediphenylene-co-4,4'-ethylenediphenylene carbonate r 16 poly[4,4'-methylenebis (2-methyl-phenylene)carbonate]
17 polyll,l-(p-bromophenylethylidene)bis(1,4-phenylene)carbonate]
18 poly[4,4'-isopropylidenediphenylene-co-4,4'-sulfonyldiphenylene) carbonat-r 19 polyl4,4'-cyclohexanylidene(4-diphenylene) .
carbonate]
poly~4,4'-isopropylidenebis(2-chlorophenylene) carbonate]
21 poly(4,4'-hexafluoroisopropylidenediphenylene carbonate) 22 poly(4,4'-isopropylidenediphenylene 4,4'-isopropylidenedibenzoate) 23 poly(4,4'-isopropylidenedibenzyl 4,4'-isopropylidenedibenzoate) 24 poly[4,4'-(1,2-dimethylpropylidene)diphenylene carbonate]
poly[4,4'-(1,2,2-trimethylpropylidene)-diphenylene carbonate]
26 poly ~4,4'-[1-(Q-naphthyl)ethylidene]-diphenylene carbonate~
27 poly[4,4'-(1,3-dimethylbutylidene)-diphenylene carbonate]
28 poly[4,4'-(2-norbornylidene)diphenylene carbonate]

1046;330 Table 2 (continued) No.Polymeric Material 29poly[4,4'-(hexahydro-4,7-methanoindan-5-ylidene) diphenylene carbonate]
Electrophotographic elements of the invention con-taining the above-described aggregate photoconductive com-position can be prepared by blending a dispersion or solution of the photoconductive composition together with a binder, when necessary or desirable, and coating or forming a self-supporting layer with the materials. Supplemental materials useful for changing the spectral sensitivity or electrophoto-sensitivity of the element can be added to the composition of the element when it is desirable to produce the characteristic effect of such materials. If desired, other polymers can be in-corporated in the vehicle, for example, to alter physical properties such as adhesion of the photoconductive layer to the support and the like. Techniques for the preparation of aggregate photoconductive layers containing such additional vehicles are described in C.L. Stephens, U.S. 3,679,407, issued July 25, 1972, and entitled METHOD OF FORMING HETEROGENEOUS
PHOTOCONDUCTIVE coMæosITIoNs AND ELEMENTS. The photoconductive layers of the invention can also be sensitized by the addition of effective amounts of sensitizing compounds to exhibit improved electrophotosensitivity.
The amount of distyryl-containing photoconductor incor-porated into the aggregate photoconductive compositions and elements of the invention can be varied over a relatively wide range. However, when used as a photoconductor in an ag-gregate photoconductive composition the distyryl-containing com-pounds described herein or a mixture thereof should be the only organic photoconductor present in the continuous phase of the aggregate composition and should be present in an amount in ~ - 19 -excess of about 15% by weight (based on the dry weight of the aggregate - l9a -0~6~3~) photoconductive composition). Small amounts of the distyryl-containing compound (i.e., amounts less than about 15 percent by weight of the total dry weight of the aggregate photoconductive composition) may be advantageously incorporated in an aggregate photoconductlve composition (as described in the previously cross-referenced Contois and Rossi, Canadian patent application Serial No. 198,352), as an additive in combination with a non-blue light absorbing organic photoconductor to provide enhanced resistance to electrical fatigue, improved temperature stability, and enhanced blue sensitivity. But, in accord with the present invention, larger amounts of the distyryl-containing compound (e.g. amounts in the range of 15 to 35 weight percent or more~ are incorporated in the continuous polymer phase of an aggregate photoconductive composition as the sole organic photoconductor contained in said continuous phase, thereby significantly increasing the overall white light electrophoto-graphic speed of the resultant aggregate composition as well as providing enhanced blue sensitivlty. At the same tlme, however, aggregate photoconductlve compositions containlng very large amounts of the distyryl-containing compound (i.e., amounts on the order of about 25 welght percent or more) do not appear to exhibit as good electrical fatigue resistance (sometimes referred to as charge regeneration) as ls provlded when smaller amounts of the dlstyryl-contalnlng compound ls lncorporated thereln as an addltlve ln comblnatlon wlth a non-blue llght absorblng organlc photocon-ductor. Accordingly, aggregate photoconductive composltions of the present inventlon whlch contaln a large amount of the distyryl-contalnlng aromatic compound as a photoconductor are particularly useful, ~or example, in electrographic elements and processes re-quiring relatively high speed non-reusable photoconductive com-positions. In contrast, small amounts of the distyryl-containing aromatic compound are particularly useful as an additive for a reusable aggregate photoconductive composition, which even without :

-. ' ' '', ~-'' . ' .

-104~330 the distyryl-containing aromatic compound possesses a white light speed at or near the desired level, to provide improved resistance to electrical fatigue, improved temperature stability, and enhanced blue light sensitivity.
In addition to electrographic elements containing the above-described aggregate photoconductive compositions there are other useful embodiments of the present invention. For example, "non-aggregate-containing"electrographic elements can be prepared with the photoconductive compounds of the in-vention in the usual manner, i.e., by blending a dispersion orsolution of a photoconductive compound together with a binder, when necessary or desirable, and coating or forming a self-supporting layer with the photoconductor-containing materials.
Mixtures of the photoconductors described herein can be employed.
Likewise, other inorganic and organic photoconductors known in the art can be combined with the present photoconductors. In addition, supplemental materials useful for changing the spectral sensitivity or electrophotosensitivity of the element can be added to the composition of the element when it is desirable to produce the characteristic effect of such materials.
The "non-aggregate" photoconductive layers of the in-vention such as homogeneous organic photoconductive composi-tions, photoconductive compositions comprising an organic com-pound used in the present invention together with an inorganic compound such as lead oxide, and the like can be sensitized by the addition of effective amounts of sensitizing compounds to exhibit improved electrophotosensitivity. Sensitizing compounds useful with the photoconductive compounds of the present inven-tion can be selected from a wide variety of materials, including such materials as pyrylium dye salts including thiapyrylium dye materials as pyrylium dye salts including thiapyrylium dye salts and selenapyrylium dye salts disclosed in VanAllan et 104~330 al U.S. Patent No. 3,250,615; fluorenes, such as 7,12-dioxo-13-dibenzo(a,h)fluorene, 5,10-dioxo-4a,11-diazobenzo(b)-fluorene, 3,13-dioxo-7-oxadibenzo (b,g)fluorene, and the like; aromatic nitro compounds of the kinds described in U.S. Patent No. 2,610,120; anthrones like those disclosed in U.S. Patent No. 2,670,284; quinones, U.S. Patent No.
2,670,286; benzophenones U.S. Patent No. 2,670,287;
thiazoles,U.S. Patent No. 2,732,301; mineral acids;
carboxylic acids, such as maleic acid, dichloroacetic acid, trichloroacetic acid and salicyclic acid, sulfonic and phosphoric acids, and various dyes, such as cyanine (including carbocyanine), merocyanine, diarylmethane, thi-azine, azine, oxazine,XQn~nO , phthalein, acridine, azo, anthraquinone dyes and the like and mixtures thereof. The sensitizers preferred for use with the compounds of this invention are selected from pyrylium salts including selena-pyrylium salts and thiapyrylium salts, and cyanine dyes including carbocyanine dyes.
Where a sensitizing compound is employed with the binder and organic photoconductor to form a sensitized electro-photographic element, it is the normal practice to mix a suitable amount of the sensitizing compound with the coating composition so that, after thorough mixing, the sensitizing compound is uniformly distributed in the coated layer.
Other methods of incorporating the sensitizer or the effect of the sensi~izer may, however, be employed consistent with the practice of this invention. In pre-paring the non-aggregate photoconductive layers, no sen-sitizing compound is required to give photoconductivity in the layers which contain the photoconducting substances, there-fore, no sensitizer is required in a particular photoconductive layer. However, since relatively minor amounts of sensitizing ." . .

, 104ti330 material can provide relatively large increases in photocon-ductivity, the use of the sensitizer is preferred. The amount of sensitizer that can be added to a photoconductor-incorporating layer to give effective increases ln speed can vary widely.
The optimum concentration in any given case will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.001 to about 30 percent by weight based on the weight of the film-forming coating composition. Normally, a sensi-tizer is added to the coating composition in an amount by ~.
weight from about 0.005 to about 5~0 percent by weight of the total coating composition.
Preferred binders for use in preparing the presentnon-aggregate photoconductive layers are film-forming, hydro-phobic polymeric binders having fairly high dielectric strength and good electrical insulating properties.
Typical of these materlals are:
I. Natural resins including gelatin, cellulose ester derivatlves such as alkyl esters of carboxylated cellulose, hydroxy ethyl cellulose, carboxy methyl cellulose, carboxy methyl hydroxy ethyl cellulose, etc.;
II. Vinyl resins including a. polyvinyl esters such as a vinyl acetate resin~ a copolymer of vinyl acetate and crotonic acid, a copolymer of vinyl acetate with an ester of vinyl alcohol and a higher aliphatic carboxylic acid such as lauric ;~
acid or stearic acid, polyvinyl stearate, a copolymer of vinyl acetate and maleic acid, ~A

104~330 a poly(vinylhaloarylate) such as poly(vinyl-m-bromobenzoate-covinyl acetate), a ter-polymer of vinyl butyral with vinyl alcohol and vinyl acetate, etc.;
b. vinyl chloride and vinylidene chloride polymers such as a poly(vinylchloride), a copolymer of vinyl chloride and vinyl isobutyl ether, a copolymer of vinylidene chloride and acrylonitrile, a terpolymer of vinyl chloride, vinyl acetate and vinyl - -alcohol, poly(vinylidene chloride) a ter-polymer of vinyl chloride, vinyl acetate and maleic anhydride, a copolymer of vinyl chloride and vinyl acetate, etc.;
c. styrene polymers such as polystyrene, a nitrated polystyrene, a copolymer of styrene and monoisobutyl maleate, a copoly-mer of styrene with methacrylic acid, a co-polymer of styrene and butadiene, a copolymer of dimethylitaconate and styrene, polymethylstyrene, etc.;
d. methacrylic acid ester polymers such as a poly(alkylmethacrylate), etc.;
e. polyolefins such as chlorinated poly-; ethylene, chlorinated polypropylene, poly(isobutylene), etc.;
f. poly(vinyl acetals) such as poly(vinyl butyral), etc.; and g. poly(vinyl alcohol);
III. Polycondensates including a. a polyester of 1,3-disulfobenzene and 2,2-bis(4-hydroxyphenyl)propane;

- : . ' :

10~330 b. a polyester of diphenyl-p,p'-disulphonic acid and 2,2-bis(4-hydroxyphenyl) propane;
c. a polyester of 4,4'-dicarboxyphenyl ether and 2,2-bis(4-hydroxyphenyl)propane;
d. a polyester of 2,2-bis(4-hydroxyphenyl)-propane and fumaric acid;
e. polyester of pentaerythritol and phthalic acid;
f. resinous terpene polybasic acid;
g. a polyester of phosphoric acid and hydroquinone;
h. polyphosphites;
i. polyester of neopentylglycol and iso-phthalic acid;
j. polycarbonates including polythiocarbonates such as the polycarbonate of 2,2-bis(4-hydroxyphenyl)propane;
k. polyester of isophthalic acid, 2,2-bis[4-(~ -hydroxyethoxy)phenyl]propane and ethylene glycol;
1. polyester of terephthalic acid, 2,2-bis[4-( ~-hydroxyethoxy)phenyl]propane and ethylene glycol;
m. polyester of ethylene glycol, neopentyl, glycol, terephthalic acid and isophthalic acid;
n. polyamides;
o. ketone resins; and p. phenol-formaldehyde resins;
IV Silicone resins;
V Alkyd resins including styrene-alkyd resins, silicone-alkyd resins, soya-alkyd resins, etc.;

.

104f~330 VI. Polyamides;
VII. Paraffin; and VIII. Mineral waxes.
Solvents useful for preparing coating compositions containing the photoconductors of the present invention can include a wide variety of organic solvents for the components of the coating composition.
Typical solvents include:
1) Aromatic hydrocarbons such as benzene, naph- -thalene, etc., including substituted aromatic hydrocarbons such as toluene, xylene, methylene, etc.;
2) Ketones such as acetone, 2-butanone, etc.;
3) Halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, ethylene chloride, etc.;
4) Ethers including cyclic ethers such as tetra-hydrofuran,ethylether;

5) Mixtures of the above.
In preparing the non-aggregate-containing photo-conductive coating compositions of the present invention useful results are obtained where the photoconductor is present in an amount equal to at least about 0.1 weight percent of the coating composition. The upper limit in the amount of photoconductive material present can be widely varied to at least 90~ by weight in accordance with usual practice.
Suitable supporting materials on which the photocon-ductive layers of this invention can be coated include any of a wide variety of electrically conduct mg supports, for example, paper (at a relative humidity above 20 percent); aluminum-paper laminates; metal foils such as aluminum foil, zinc foil, etc.;
metal plates, such as aluminum, copper, zinc, brass and :: .

~- 1046330 galvanized plates; vapor deposited metal layers such as silver, nickel, aluminum and the like coated on paper or conventional photographic film bases such as cellulose acetate, polystyrene, etc. Such conducting materials as nickel can be vacuum de-posited on transparent film supports in sufficiently thin lay-ers to allow electrophotographic elements prepared therewith to be exposed from either side of such elements. An especially useful conducting support can be prepared by coating a support material such as poly(ethylene terephthalate) with a conducting layer containing a semiconductor dispersed in a resin or vacuum deposited on the support. Such conducting layers both with and without insulating barrier layers are described in U.S.
Patent 3,245,833 by Trevoy, issued April 12, 1966. Likewise, a suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer. Such kinds of conducting layers and methods for their optimum preparation and use are disclosed in U.S. 3,007,901 by Minsk, issued November 7, 1961 and 3,262,807 by Sterman et al, issued July 26, 1966.
Coating thicknesses of the photoconductive compo-sition on the support can vary widely. Normally, a coating in the range of about 10 microns to about 300 microns before drying is useful for the practice of this invention. The preferred range of coating thickness is found to be in the range from about 50 microns to about 150 microns before drying, although useful results can be obtained outside of this range.
The resultant dry thickness of the coating is preferably be-tween abo~t 2 micron~ aRd abou~ 50 mi~ro~a, although usef~l results can be obtained with a dry coating thickness between about 1 and about 200 microns.
After the photoconductive elements prepared ~04~30 according to the method of this invention have been dried, they can be employed in any of the well-known electrophotographic processes which require photoconductive layers. One such pro-cess is the xerographic process. In a process of this type, an electrophotographic element is held in the dark and given a blanket electrostatic charge by placing it under a corona discharge. This uniform charge is retained by the layer be-cause of the substantial dark insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photocon-ductive layer is then selectively dissipated from the surface of the layer by imagewise exposure to light by means of a con-ventional exposure operation such as, for example, by a contact printing technique, or by lens projection of an image, and the like, to thereby form a latent electrostatic image in the ;i`
photoconductive layer. Exposing the surface in this manner forms a pa~ern of electrostatic charge by virtue of the fact that light energy striking the photoconductor causes the electro-static charge in the light struck areas to be conducted away from the surface in proportion to the intensity of the illumi-nation in a particular area.
The charge pattern produced by exposure is then de-veloped or transferred to another surface and developed there, i.e., either the charged or uncharged areas rendered visible, by treatment with a medium comprising electrostatically respon-sive particles having optical density. The developing electro-statically responsive particles can be in the form of a dust, i.e., powder, or a pigment in a resinous carrier, i.e., toner. A preferred method of applying such toner to a latent electrostatic image for solid area development is by the use of a magnetic brush. Methods of forming and using a magnetic , . : . :.
~- '' ~ .

10~330 brush toner applicator are described in the following U.S.
Patents: 2,786,439 by Young, issued March 26, 1957; 2,786,440 by Giaimo, issued March 26, 1957; 2,786,441 by Young, issued March 26, 1957; 2,874,063 by Greig, issued February 17, 1959.
Liquid development of the latent electrostatic image may also be used. In liquid development, the developing particles are carried to the image-bearing surface in an electrically in-sulating liquid carrier~ Methods of development of this type are widely known and have been described in the patent literature, for example, U.S. Patent 2,907,674 by Metcalfe et al, issued October 6, 1959. In dry developing processes, the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a low-melting resin. Heating the powder image then causes the resin to melt or fuse into or on the element.
The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a trans-fer of the electrostatic charge image formed on the photo-conductive layer can be made to a second support such as paper which would then become the final print after development and fusing. Techniques of the type indicated are well known in the art and have been described in the literature such as in "RCA
Review" Vol. 15 (1954) pages 469-484.
The following examples are included for a further understanding of this invention.
Preparation of Photoconductors The photoconductive materials used in the composi-tions of the invention may be prepared by known methods of che-mical synthesis. Specifically, the compounds used herein are prepared by reacting any of various dialkylarylphosphonates with an appropriate aldehyde in the presence of a strong base to 10~i330 give the desired olefin product. By this procedure, the reac-tion of p-diphenylaminobenzaldehyde or 4-di-(p-tolylamino) benzaldehyde with an appropriate bis-phosphonate and two equi-valents of sodium methoxide in dimethylformamide solution is used to prepare the distyryl compounds I-VI listed in Table 1 hereinbefore.
For purposes of illustration the specific reac-tion procedure used to prepare compound V of Table 1 is as follows:
To a solution of 6.1 g of tetraethyl 4,6-dimethyl-m-xylylenediphosphonate and 2.0 g of sodium methox-ide in 50 ml of dimethylforamide is added dropwise at room tem-perature 9.0 g of 4-di-p-tolylaminobenzaldehyde in 50 ml of dimethylformamide; an exotherm to 40C occurs. A solid separates after several minutes and the mixture is stirred overnight at room temperature. The mixture is poured onto 100 g of ice, and the yellow solid is collected, washed with 50 ml of water and air-dried to give 10.5 g of crude product, m.p. 91-102C. Two recrystallizations from dimethyl-formamide gives 4.1 g of com-pound V if the form of yellow crystals, m.p. 211-215C.
The other photoconductive compounds of Table 1 are prepared by a similar procedure.
Example 1 In this example aggregate and homogeneous organic photoconductive compositions of the present invention are com-pared to the somewhat similar photoconductors described in Merrill, U.S. Patent 3,653,887 to demonstrate the unexpected improvement in 100 volt positive toe speed provided by the photo-conductive compositions of the present invention. A set of four different photoconductive compositions coated on a con-ductive film support are tested for each photoconductor, three .. . . , . , ,. . :. .

10~330 homogeneous photoconductive compositions, i.e., Nos. 1-3 below, and one aggregate composition, i.e., No. 4 below, the type des-cribed in Light, U.S. Patent 3,615,414. The formulation of the compositions used in this example is as follows:
No. 1: 78.4 weight percent polyester binder, 20 weight percent photoconductor, 1.6 weight percent of the sensitizer 4-(n-butyl amino) -2-(4-methoxy phenyl) benzo[b] pyrylium perchlorate No. 2: 79.2 weight percent polyester binder, 20 weight percent photoconductor, 0.8 weight percent of the sensitizer Rhodamine B
No. 3: 80.0 weight percent polyester binder, 20.0 weight percent photoconductor, no sensitizer No. 4: 78.0 weight percent polycarbonate binder, 20.0 weight percent photoconductor, and 2.0 weight percent of the sensitizer 4-p-dimethylaminophenyl-2,6-diphenyl-pyrylium perchlorate The above four compositions are tested using two different photoconductors, A and B. Photoconductor A is a compound of the type described in U.S. 3,653,887 and has the formula CH~ ~ CN=C ~ C-C~ ~ N ~

Photoconductor B is compound II of Table 1 of the present invention. The following data is ob~ained:

.

104~i330 RELATIVE ELECTRICAL H & D SPEED

(+ 100 VOLT TOE) Photoconductor No. 1 No. 2 No. 3 No. 4 A 100* 170 0 500 *arbitrarily assigned a relative speed value of 100 for this example The relative positive 100 volt toe speeds in Table 3 are measured as described in Example 4 hereinafter. As shown in ;

Table 3, the relative 100 volt positive toe speeds of photo-conductor B of the present invention are substantially higher than prior art photoconductor A.
Example 2 This example illustrates the blue sensitivity of aggregate photoconductive compositions of the present invention.
The following aggregate photoconductive composition consisting ` of:
j polycarbonate resin 1.0 parts by weight photoconductor II of Table 1 0.25 parts by weight 2,6-Diphenyl-4-~-dimethylamino- 0.025 parts by weight phenyl thiapyrylium perchlorate is prepared as follows:
The formulation is made up by a seed-shear technique which consists of the preparation of two stock solutions:
Solution I
3.92 g of polycarbonate resin 0.08 g of 4-p-dimethylaminophenyl-2,6-diphenylthia-pyrylium perchlorate 26.8 ml dichloromethane - - . : - . . :

10~30 The above dope is sheared in a Waring Blender for 30 minutes at 70F.
Solution II
A dye solution is prepared consisting of 0.03 g of 4-_-dimethylaminophenyl-2,6-diphenylthiapyrylium per-chlorate and lO.2 ml of dichloromethane.
A dope containing these solutions is prepared as follows:
7.7 g of Solution I
4.5 g of Solution II
0.25 g of photoconductor II of Table l 0.25 g of Lexa ~ 145 The above-described dope is then coated on a conductive poly(ethylene terephthalate) support to provide a resultant aggregate photoconductive element. Wedge spectrograms of this aggregate photoconductive element are obtained when the element is exposed to visible light after being sub~ected to uniform positive charging. As a result is it found that thls aggregate photoconductive element of the invention exhibits a secondary peak of light sensitivity at 460 nm.
In contrast, when a series of prior art photo-conductors including triphenylamine, tri-p-tolylamine, 4,4'-diethylamino-2,2'-di-methyl-triphenyl methane, and _-diphenylaminocinnamic acid are substituted for the photo-conductors used in the present invention in aggregate photoconductive elements otherwise identical to that described above; it is found that wedge spectrograms of such aggregate photoconductive elements when sub~ected to light exposure after uniform positive charging exhibit a sensitivity : `

.

-` ~04~ 30 minimum at 460 nm, thereby indicating the absence of blue sensitivity possessed by these photoconductive elements.

Example 3 To illustrate the advantages of using the organic photoconductors of the present invention in combination with various inorganic photoconductors, three different photo- :
conductive compositions are made having the composition shown below as follows:
Photoconductor II of Table 1 is combined with tetragonal PbO in a polyester binder and coated on a conductive support to yield the following data shown in Table 4:

, . . . .

104~330 o ~o ~ ~ c o ~n er U~I ~ ~ N 11 ~_ O ~ ~J O
a ~

O
~ O
rl ~
s o ~q ~, _ li3 a~ In _ O O
~1 ~ ~ u~
_ o ~ ~r 0 + ~ ~ O 11 ~1-- O ~ O~ O

~I
a U _I ~ ~
R ~ O- ~ ,1 oE~ a~ 3 3 U~ R X
HO R R
ai S H dP d~
~ ~ U~

O
~ .
' .
O
~1 .,1 .,1 ~1 o a~ a~ O
U ~ 3 ~ 3 o R ~ R _I
U~ 0 O d~ ,~ dP
U ~D l'C ~
~0 ~ _1 ~1 0 H o ~ .q R
P. P~

::

~ .
a~ a~ ~1 3 3 3 R~
R R R
dP d~
~ In o~
co ~ r--Example 4 104~330 Each of photoconductors I-VI of Table 1 are used to form both homogeneous and aggregate photoconductive compositions of the invention. The homogeneous photoconductive compositions prepared in this example are prepared containing about 80~ by weight of a polyester binder, about 0.8% by weight of the sensitizer 2,6-bis(p-ethylphenyl)-4-(p-n-amyloxyphenyl)-thia-pyrylium perchlorate, and about 19% by weight of each of photo-conductors I-VI. The aggregate photoconductive compositions 10 prepared in this example contain about 80% by weight of poly-carbonate binder, about 2.0% by weight of the sensitizer 2,6-diphenyl-4-(p-dimethylaminophenyl)-thiapyrylium perchlorate, and about 18~ by weight of each of photoconductors I-VI of Table 1. Relative H and D positive and negative shoulder and 100 toe volt electrical speeds are measured for each of these photoconductive compositions as shown in Table 5.
In Examples 1-4 of the present application Relative H & D Electrical Speeds are reported. The relative H & D
electrical speeds measure the speed of a given photoconductive 20 material relative to other materials typically within the same test group of materials. The relative speed values are not absolute speed values. However, relative speed values are related to absolute speed values. The relative electrical speed (shoulder or toe speed) is obtained simply by arbitrarily assigning a value, Ro, to one particular absolute shoulder or toe speed of one particular photoconductive material. The relative shoulder or toe speed, Rn, of any other photoconductive material, n, relative to this value, Ro, may then be calculated as follows: Rn = (An)(R/Ao) wherein An is the absolute 30 electrical speed of material n, Ro is the speed value .-arbitrarily assigned to the first material, and Ao is the 10~30 absolute electrical speed of the first material. The absolute H & D electrical speed, either the shoulder (SH) or toe speed, of a material may be determined as follows: The material is electrostatically charged under, for example, a corona source until the surface potential, as measured by an electrometer probe, reaches some suitable initial value VO' typically about 600 volts. The charged element is then exposed to a 3000K
tungsten light source through a stepped density gray scale. The exposure causes reduction of the surface potential of the element under each step of the gray scale from its initial potential VO to some lower potential V the exact value of which depends upon the amount of exposure in meter-candle-seconds received by the area. The results of these measurements are then plotted on a graph of surface potential V vs. log exposure for each step, thereby forming an electrical character-istic curve. The electrical or electrophotographic speed of the photoconductive composition can then be expressed in terms of the reciprocal of the exposure required to reduce the surface potential to any fixed selected value. The actual positive or 20 negative shoulder speed is the numerical expression of 104 divided by the exposure in meter-candle-seconds required to reduce the initial surface potential VO to some value equal to VO minus 100. This is referred to as the 100 volt shoulder speed. Sometimes it is desirable to determine the 50 volt shoulder speed and, in that instance, the exposure used is that required to reduce the surface potential to VO minus 50.
Similarly, the actual positive or negative toe speed is the numerical expression of 104 divided by the exposure in meter-candle-seconds required to reduce the initial potential VO to 30 an absolute value of 100 volts. Again, if one wishes to deter-mine the 50 volt toe speed, one merely uses the exposure 10'~i33~) required to reduce VO to an absolute yalue of 50 volts. Anapparatus useful for determining the electrophotographic speeds of photoconductive compositions is described in Robinson et al, U.S. Patent No. 3,449,658, issued June 10, 1969.

, - - , '::
~;

a) I ~ o ~ I~
O ~r ~D. O .. 00 . O
a) E~ ~ ,1~ co ~~ 1~ ~ 00 0 ~ ~ ~ :
Z a) ~ :
~ O O~D OOO OO O ~D
,, o o~ ~U~U~ o~ o _, ~ ,` U~
o o o ~ U~ ,~
Cq ~ ~
~1 ~1 .

~ . . .. .. . a~
o U~ ~ ~ ,, ~ ~ oo a~ ~ _I
.,, ~o ~ .,, O ~ ~ I
P~ ~ O 1`~1 1~ 0 ~ o a ~1 O a:~_I co o oo ~ ~ o ~ Q, ~ ~ I o n o ~ ~ ~ ~
~ o o U~V~ ~ ~
o o o o ~ ,.
o o o ~ ~ ~
P:: ~ ~ ~ .
__ m Q~

~ s~ o ~o ~ oo ~ o ~ o ~ ~
m ,1 , tO 10 ~ ~ ul la o :~

_I ~I
......
~ s~

o ~ ~C
_ 115 0 H HH H H~ ~ p ~ H
E~l O H H HH H p O H

.. . ..

104~330 The invention has been described in detail with particular reference to preferred embodiments thereof but it will be lmderstood that variations and modifications can be effected within the spirit and scope of the invention.

~40-.
, "

Claims (12)

We Claim:

1. A photoconductive composition comprising an electrically insulating polymeric binder and as a photoconductor an organic compound having the formula wherein R1, R2, R3, and R4 are each selected from the group consisting of an aryl radical and an alkyl radical, Ar1 and Ar3 are each selected from the group con-sisting of an unsubstituted phenyl radical and a substituted phenyl radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, and Ar2 is an unsubstituted carbocyclic aromatic radical or a substituted carbocyclic aromatic radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, said aromatic radical having about 4 to 14 carbon atoms in the aromatic ring thereof.

2. A photoconductive composition as described in claim 1 wherein said composition contains an inorganic photoconductive compound.

3. A photoconductive composition comprising an electrically insulating binder, an organic photoconductive compound, and an amount of sensitizer effective to sensitize said composition, said photoconductive compound having the formula wherein R1, R2, R3, and R4 are each selected from the group consisting of an aryl radical and an alkyl radical, Ar1 and Ar3 are each selected from the group con-sisting of an unsubstituted phenyl radical and a substituted phenyl radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, and Ar2 is an unsubstituted carbocyclic aromatic radical or a substituted carbocyclic aromatic radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, said aromatic radical having about 4 to 14 carbon atoms in the aromatic ring thereof.

4. A photoconductive composition as described in claim 3 wherein R1, R2, R3, and R4 are each aryl radicals and Ar2 is a phenyl radical or an alkyl-substituted phenyl radical containing 1 to about 4 carbon atoms in said alkyl substituents.

5. A photoconductive composition as described in claim 3 wherein said photoconductor is selected from the group consisting of 4-diphenylamino-4'-[4-(diphenylamino)styryl]stilbene;
4-di-(p-tolylamino)-4'-[4-(di-p-tolylamino)styryl]stilbene;
4-di-(p-tolylamino)-2',3',5',6'-tetramethyl-4'-[4-(di-p-tolylamino)styryl]stilbene; 4-di-(p-tolylamino)-2'-[4-(di-p-tolylamino)styryl]stilbene; 4-di-(p-tolylamino)-2',4'-dimethyl-5'-[4-(di-p-tolylamino)styryl]-stilbene; 9,10-bis[4-(di-p-tolylamino)styryl]-anthracene; and 1,4-bis(4-N-ethyl-N-p-tolylaminostyryl)benzene.

6. A photoconductive composition as described in claim 3 wherein said composition contains photoconductive lead oxide.

7. An aggregate photoconductive composition comprising a continuous binder phase containing (a) dissolved therein greater than about 15 percent by weight of one or more organic photoconductors and (b) dispersed therein a particulate co-crystalline complex of (1) a dye selected from the group consisting of a 2,4,6-substituted pyrylium dye salt and a 2,4,6-substituted thiapyrylium dye said and (2) a carbonate polymer having an alkylidene diarylene moiety in a recurring unit, each of said organic photoconductors having the formula wherein R1, R2, R3, and R4 are each selected from the group consisting of an aryl radical and an alkyl radical, Ar1 and Ar3 are each selected from the group con-sisting of an unsubstituted phenyl radical and a substituted phenyl radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, and Ar2 is an unsubstituted carbocyclic aromatic radical or a substituted carbocyclic aromatic radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, said aromatic radical having about 4 to 14 carbon atoms in the aromatic ring thereof.

8. An aggregate photoconductive composition as described in claim 7 wherein R1, R2, R3, and R4 are each phenyl radicals or alkyl-substituted phenyl radicals and Ar2 is a phenyl radical or an alkyl-substituted phenyl radical, said alkyl substituents having 1 or 2 carbon atoms.

9. An aggregate photoconductive composition as described in claim 7 wherein said organic photoconductor is selected from the group consisting of 4-diphenylamino)-4'-[4-(diphenylamino)styryl]stilbene; 4-di-(p-tolylamino-4'-[4-(di-p-tolylamino)styryl]stilbene; 4-di-(p-tolylamino)-2', 3',5',6'-tetramethyl-4'-[4-(di-p-tolylamino)styryl]stilbene;
4-di-(p-tolylamino)-2'-[4-(di-p-tolylamino)styryl]stilbene; 4-di-(p-tolylamino)-2',4'-dimethyl-5'-[4-(di-p-tolylamino)styryl]-stilbene; and 1,4-bis(4-N-ethyl-N-p-tolylaminostyryl)benzene.

10. In an electrophotographic element comprising a conductlve support and a photoconductive layer coated over said support, the improvement wherein said photoconductive layer comprises the photoconductive composition of claim 1.

11. In an electrophotographic element comprising a conductive support and a photoconductive layer coated over said support, the improvement wherein said photoconductive layer comprises the photoconductive composition of claim 7.

12. In an electrophotographic process wherein an electrostatic charge pattern ls formed on a photoconductive element comprised of an electrically conducting support having coated thereover a layer of a photoconductive composition, the improvement wherein said photoconductive composition is as described in claim 1.