CA1065126A - Photoconductive composition and elements containing same - Google Patents

Abstract

Abstract of the Disclosure An organic photoconductive insulating composition and electrophotographic elements containing the same are prepared using as a photoconductor a polyarylalkane compound having the formula

Description

65~;26 Field of the Invention This invention relates to electrophotography and in particular to photoconductive insulating 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 image-wise exposure. The element, commonly termed a photoconductiveelement, 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 electrophotographic 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 transerred to a second element to which it can-similarly be fixed. Likewise, 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 elements.
For example, vapors of selenium and vapors of selenium alloys

-2--deopsited on a suitable support and particles of photoconductive zinc oxide held in a resinous, film-forming 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 photo-conductive properties. As a result, a very large number Or organic compounds have been known to possess some degree of photoconductivity. Many organic compounds have revealed a useful level of photoconduction and have been incorporated into photoconductive compositions. Among these organic photo-conductors are certain of the triphenylamines as described in U.S. 3,180,730 issued April 27, 1965, and the polyarylalkane compounds such as those described in U.S. 3,274,000 issued September 20, 1966; u.s. 3,542,547 issued November 24, 1970;
U.S. 3,542,544 issued November 24, 1974; and in Rule, U.S.

3,615,402 issued October 26, 1971 and Rule, U.S. 3,820,989 issued June 28, 1974.
Optically clear organic photoconductor-containing elements having desirable electrophotographic properties can be especially useful in electrophotography. Such electrophotographic elements can be exposed through a transparent base if desired, -thereby providing flexibility in equipment design. Such compo-sitions, when coated as a film or layer on a suitable 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 generally proceeded on an empirical compound~by-compound selection basis.
A high speed "heterogeneous" or "aggregate" multiphase 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 t~e sub~ect matter of U.~. Patent No. 3,615,414 issued Octo~er 26, 1971. The addenda disclosed therein are responsible for the exhibltion of desirable electrophotographic properties in photoconductive elements prepared therewith. In particular, they have been round to enhance the speed of many organic photo-conductors when used therewith. The degree of such enhancement is, however, variable, depending on the particular organic photoconductor so used.

Summary o~ the Invention In accord with the present invention there is provided an organic,photoconductive insulating composition comprising a pol~arylalkane compound havin~ the formula Rs I. \N A1 - C - A2 _ N
R4/ 1 \R~

wherein Rl and R2, which may be the same or different, represent, when taken separately, hydrogen, aryl groups and alkyl groups, including substituted alkyl and aryl groups, and, when taken together, represent the saturated carbon atoms necQssary to complete a cycloalkyl group; R3, R , R5 and R6, which may be the same or different, each represent an aryl group, including a substituted aryl group; and Al and A2, which may be the same or different, represent phenyl groups, including substituted phenyl groups.

1 0 6 5~Z6 .
In accord with one embodiment of the present invention, it has been discovered that one or more of the ~ :
polyarylalkane compounds of rormula I may be employed as an organic photoconductor in the continuous polymer phase of a mul~iphase aggregate photoconductive composition of the type referred to hereinabove to extend the white light speed and thermal stability of the aggregate photoconductive composition.
In accord with another embodiment of the invention, it has been found that one or more of the polyarylalkane compounds of formula I may be employed as an organic photo-conductor in a "non-aggregate-containing" organic photocon-ductive insulating composition~ for example, a homogeneous organic photoconductive composition comprising a solid solution of one or more of the pGlyarylalkane compounds of formula I and a polymeric binder.
Various polyarylalkane compounds having a chemical structure somewhat related to, but not idential to, those described above in formula I have been disclosed in the prior art as useful in organic photoconductive compositions.
20 Representative of such prior art materials are compounds such as those disclosed in U.S. 3,542,547; u.s. 3,615,402; and u.s.3,820,989. -Other non-polyarylalkane classes of compounds somewhat similar to, but less closely related to, the polyarylalkane compounds of formula I above than the polyarylalkane com-pounds shown in U.S. 3,542,547, have also been described in the prior art as useful in organic photoconductive compositions. See, for example, the compounds shown in Canadian Patent 914,699 issued November 14, ~972 and U.S. Patents .
3,387,973, is sued June 11, 1968.
- .

~ 5 ... . . . .. . . . .. . . . .

1065~26 According to the present inventlon, it has been found that the photoconductors described hereln have sub-stant:Lally improved electrical speed over those related photoconductors described in U.S. 3,542,547. In addition, lt has been found that the photoconductors of the present invention enhance the thermal stability of organic photo-conductive compositions in comparison to those related photoconductors described in Canadian Patent 914,699 and U.S. Patents 3,615,402 and 3,820,989.
Small amounts of other polyarylalkane compounds structurally similar to those described above in formula I, ~or example, 4,4'-tetramethyldiaminodiphenylmethane, have been descrlbed in the prior art, e.g., in British Patent 1,141,666 datec January 29, 1969, as chemical activatorB or sensitizers for zinc oxlde photoconductive compositions. However, there is no teaching or su~gestion in British Patent 1,141,666 that com-pounds having formula I above are useful as organic photo-conductors in an organic photoconductive composition, i.e.
a photoconductive composition free from all inorganic photo-conductors such as zinc oxide. Moreover, it has been found that the organic photoconductive compositions of the present invention which contain the organic photoconductive compounds of formula I above exhibit enhanced thermal stability in comparison to that which would be obtained in the organic photoconductive composition if the "zinc-oxide-sensitizer"
compound of British Patent 1,141,666, i.e., 4,4'-tetramethyl-diaminodiphenylmethane, were substituted for the organic photoconductive compounds used in the present invention.

-5a-`~'` 10651Z6 ~ ~

De~ tion Or t~)e Prererred Embot~lments ~ e prercrred photoconductols Or the invention may be characterlzed by the following formula:

R~
I- ~\N Al - C- _ A2 _ N\ ;~

whereln }~1 and ~2, which can be the s~ne or different, represen~, -when takcn separately, hydrogen, alkyl, or aryl ~roups including -~substituted alkyl and aryl groups; and, when taken together, R -and R represent the saturated carbon atoms necessary to complete a substituted or unsubstituted cycloalkyl ~roup havlng from 3 to ~ -prererably from 5 to 7, carbon atoms in the cycloalkyl ring;
R3, Rl, R5 ind R6, which can be the same or dirrerent, each represent an unsubstltuted or substltuted aryl group; and Al and A2, which may be the same or different, represent an unsubstituted or substituted phenyl group.
Typlcally Rl and R2 represent one Or the rollowing alkyl or aryl groups:

1. an alkyl group having 1 to 18 carbon atoms e.g., rnethyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl, etc. includlng a substltuted alkyl group having 1 to 18 carbon atoms such as a. alkoxyalkyl, e.g., ethoxypropyl, methoxybutyl, ;~
propoxymethyl, etc., b. aryloxyalkyl, e.g., phcnoxyethyl, naphthoxymethyl, -phenoxypentyl, etc., ;
c. aminoalkyl, e.g., aminobutyl, amllloetl1yl, aminopropyl, etc., 1065~Z6 ~ .' d. hydroxyalkyl e.g., hydroxypropyl, hydroxyoctyl, etc., e. aralkyl e.g., oenzyl, p;nenethyl, etc.
f. alkylaminoalkyle.g., methylaminopropyl, methylzmino-ethyl, etc., ar.d also including dialkylaminoalkyl e.g., diethylaminoethyl, dimetnylaminopropyl, propyl-aminooctyl, etc., g. arylaminoalkyl, e.g., phenyl~ninoalkyl, diphenyl-aminoalkyl, N-pnenyl-N-ethylaminopentyl, N-phenyl-N-ethyl~ninohexyl, naphthylaminomethyl, etc., h. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitro-pentyl, etc., i. cyanoalkyl, e g., cyanopropyl, cyanobut~J1, c~ano-ethyl, etc., and j. haloalkyl, e.g., chloromethyl, bromopentyl, chloro-- octyl, etc., k. alkyl substituted with an acyl Oroup having tne 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 carbon 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, naphthoxyphenyl, 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, methylamino-naphthyl, 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, nitronaphthyl, nitroanthryl, etc., i. cyanoaryl, e.g., cyanophenyl, cyanonaphthyl, cyanoanthryl, etc., j. haloaryl, e.g., chlorophenyl, bromophenyl, -chloronaphthyl, etc., ;;
k. alkaryl, e.g., tolyl, ethylphenyl, propylnaphthyl, etc., and `~
1. aryl substituted with an acyl group having the formula ; ~ 11 , ' , -C-R
wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, --etc., amino including substituted amino, e.g., diloweralkylamino, lower alkoxy having one to eight carbon atoms, e.g., butoxy, ~ methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy,~etc., lower 30 ~ ;

,:
:

!

alkyl ~aV1nIJ 1 to 8 car~on a~oms,, e.~., mcthyl, ethyl, propyl, butyl, c~c.
T lcallY R3 ~4 R5 and R6 represent an aryl group as derined herelnabove ror ~1 and R2.
Typically, Al and A2 represent an unsubstituted phenyl group or ~ substi~uted pherlyl group having one or more substituent gro~ps such as those defined hereinabove for Rl and R2 in the case where Rl and R2 reprcsent substltuted aryls. In general, Al and A2 are unsubstituted when both Rl and R2 represent 10 substituents other th~n hydrogen. :~

In the case where Rl and R2 are taken togethcr ~ ~.
to form a substituted cycloalkyl ring, representative substitucnts are linear or branched chain aliphatic yroups having 1 to 10 and preferably 1 to ~ carbon atoms in the group.
~l'yplcal o~ such substitue~nts are those aliphatic groups includecl in the class or substituted and unsubstituted alkyl . groups listed above for R and R2.
Typical compounds which belon3 to the general class of photoconcluctive compounds described herein include the following materials listed in Table 1 below:

,, ~

1065~26 ..

a~ ~3 , ; ' C~l o ~, , o ~ ~ ~ ,, .

R ~ 1~ D

~ ~-V~ . ~V-V~

~: o ", ,r ~ ~ a ~1 c cu H
H H

~ -10-.. . . . .. . . .

~O~SlZ6 o ~ o o ,~

a ~0 ~ /r u ,~

0~
o ~ D (~ V

~ J p~ J ~ ` --- V ~-- V I V I V
m ~ m .

_~ H

~ -lOa-.
'', ~.
O ~h " ' '' ~ ,5 :

- H X X
.

- -lOb- -10651Z~
Compounds which belong to the general class of photoconductive compounds described herein and which are preferred for use in accord with the present invention include those compounds having the structural formula shown above wherein Al and A2 are unsubstituted phenyl groups and at least one of Rl or R2 represent a group other than hydrogen, preferably Rl and R2, taken together, represent the necessary saturated carbon atoms to complete a 6-member cycloalkyl ring. These compounds are preferred because of the high electrical speeds and significantly increased thermal stability which is obtained from organic photoconductive compositions containing the same. ;
Compounds which belong to the general class of photo-conductive compounds described herein and which are especially ~;
preferred for use in accord with the present invention include those compounds having the structural formula shown above wherein ~1 and A2 are unsubstituted phenyl groups, Rl and R represent the necessary saturated carbon atoms to complete a 6-member cycloalkyl ring, and R3, R4, R5 and R6 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. These compounds are preferred because of their ~enerall~ increased thermal stability and because of the high electrical speeds which are obtained from organic photoconductive compositions, particularly aggregate photoconductive compositions, - which contain these compounds.
The photoconductive insulating compositions used in the photoconductive elements of the present invention are essentially organic material-containing compositions free from all inorganic photoconductors, i.e., photoconductors such as zinc oxide composed solely of inorganic molecules. The term "organic"~ as used herein, refers to both organic and metallo-organic materials.

--11-- .

iO65126 The organic, aggregate photocnnductive insulating compo-sitions used in this invention comprise an organic sensitizing dye and an electrically insulating, 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 speed shearing of the photoconductive 10 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 polyarylalkane photocon-ductor of the invention in a suitable solvent to form a photocon-ductor-containing composition which is coated on a suitable support to form a separately identi~iable multiphase composition, the hetero-geneous nature of which is generally apparent when viewed under ma~nification, although such compositions may appear to be sub-stantially optically clear to the naked eye in the absence of 20 magnification. There can, of course, be macroscopic hetero- ~-geneity. Suitably, the dye-containing aggregate in the discon- `
tinuous 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 aggrega-te 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 wavelength of the radiation absorption maximum characteristic of such compositions is substantially shifted from the wavelength of the radiation absorption maximum of a substantially homogeneous dye-p~lymer solid solution formed of similar constituents. 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 at least about 10 nm. If mixtures of dyes are used, one dye may cause an absorption maximum shift to a longer wavelength and another dye cause an absorption maximum shift to a shorter wavelength. In such casés, a formation of the aggre-- gate compositions can more easily be identified by viewing under magnification.
Sensitizing dyes and electrically insulating poly-meric materials are used in forming these aggregate compositions.
Typically, pyrylium dyes, including pyrylium, bispyrylium, thiapyrylium and selenapyrylium dye salts and also salts of pyrylium compounds containing condensed ring systems such as salts of benzopyrylium and naphthcpyrylium 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:

1065126 `
. ~ -R

~ Z~

wherein: j`
R5 and R6 can each be phenyl groups, including / ~;
substituted phenyl groups having at least one substituent chosen from alkyl groups of from 1 to about 6 carbon atoms ,.... .
and alkoxy groups having from 1 to about 6 carbon atoms; ~`-10R7 can be an alkylamino-substituted phenyl group ~ -. , having from 1 to 6 carbon atoms in the alkyl group, and including dialkylamino-substituted and haloalkylamino-substituted phenyl groups; `
X can be an oxygen, selenium or a sulfur atom; and ; ~ i9 an anion.
The polymers useful in forming the aggregate com- .
positions include a variety of materials. Particularly useful are electrically insulating, film-forming polymers having an -alkylidene diarylene group in a recurring unit such as those linear polymers, including copolymers, containing the following group in a recurring unit:

:R8 j ll ~C ~ R12 ,, wherein:
Rg and Rlo, when taken separately, can each be a hydrogen atom, an alkyl group having from one to about 10 carbon atoms such as methyl, ethyl, isobutyl, hexyl, heptyl, octyl, nonyl, decyl, and the like including substituted alkyl groups such as trifluoromethyl, etc., and an aryl group such as phenyl and ~065126 naphthyl, including substituted aryl groups having such sub-stituents as a halogen atom, an alkyl group of from 1 to about 5 carbon atoms, etc.; and Rg and Rlol when taken together, can represent the carbon atoms necessary to complete a saturated cyclic hydrocarbon group including cycloalkanes such as cyclo-hexyl 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 group of from 1 to about 5 carbon atoms, e.g., or a halogen such as chloro, bromo, iodo, etc.; and R12 is a divalent group selected from the following:

" ~ . " , 3 -0-C-0-, -O-C-O-, -C-O, -C-O-CH -, -C-O-CH-O O .~
., .. ,;. .
-CH2-0-C-0-, and -0-P-0-Preferred polymers useful for forming aggregate crystals are hydrophobic carbonate polymers containing the following group in a recurring unit:
Rg O
-R-C-R-O-C-O-wherein:
each R is a phenylene group including halo sub-stituted phenylene groups and alkyl substituted phenylene groups; and Rg and Rlo are described above. Such compositions are disclosed, for example in U.S. Patent Nos. 3,028,365 and 3,317,466. Preferably polycarbonates containing an alkylidene diarylene group in the recurring unit such as those prepared with Bisphenol A and including polymeric 10651Z6 ` ~ . ~

products of ester exchange between diphenylcarbonate and 2,2-bis-(4-hydroxyphenyl)propane are useful in the practice of -`
this ~nvention. Such compositions are disclosed in the following ~ :
U.S. Patents: U.S. 2,999,750 by Miller et al, issued September -.
12, lg61; 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 polycarbonate 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. :. ;
,s ...
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-cyclohexylenedimethylene 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) ~^. -16-. . . . .- , .

l~blc 2 (continl~ccl) No. Polymcric~ teri~l ..
9 poly [4,~ isopropylidenebis (2-methyl~
phenylene)-carbonate]
poly(4,4'-:isopropylidenediphenylene-co-1,4-phenylene carbonate) 11 po:Ly(4,~ ,opropylidenediphenylene-co-1,3-phenylene carbonate) 12 poly(4,4'-isopropyliderlediphenylene-co- ~ `.
o 4,4'-diphenylene carbonate) 13 poly(4,4'-isopropylidenediphenylene-co-4,4'-oxydiphenylene carbonate) .
14 poly(4,4'-i.sopropylidened.ipheny].ene-co-4,4'-carbonyldiphenylene carbonate r poly(4,4'-isopropylidenediphenylene-co- ~-4,4'-ethylenediphenylene carbonate r 16 poly[~ '-methylenebi~(2-methyl-phenylene)carbonate] `
17 poly[l,l-(p-bromophenylethylidene)bis(1,4- -phenylene)carbonate]
18 polyr~ opropylidenediphenyJ,cnc-co-4,4'-sul~onyld,phenylene)carbonate 19 poly~4,1l'-cyclohexylidene(4-diphenylene) carbonate]
poly[4,4'-i~opropylidenebis(2-chlorophenyl-ene)carbonate] , .
21 poly(4,4'-he~afluoroisopropylidenediphenyl ene carbonate) 22 poly(4,4'-i~opropylidenediphenylene 4,4'-isopropylidenedibenzoate) 23 poly(4,4'-i.sopropylidencdibenzyl 4,4'-isopropylidenedibenzoate) 24 poly[4,4'-(1,2-dilnetllylpropylidene)di-. phenylene carbonate]
poly[4,4'-(1,2,2-trimethylpropylic~ene)- .
diphenylene carbonate]
26 P O] Y ~IL, 4 1 -[l-(a-naphthy.l)ethylidene]-4 . diphenylene carbonate~
27 poly[4,4'-(1,3-dimethylbutylidene)-diphenylene carbonate]
28 poly~4,4'-(2-norbornylidene)diphenylene . carbonate]
29 poly[4,4f-(hexahydro-4,7-methanoindan-5-ylidene) diphenylene carbonate]

.

~0651Z6 Electrophotographic elements of the invention contain~
ing the above-described aggregate photoconductive composition 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 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. If desired, other polymers can be incorporated 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 COMPOSITIONS
AND ELEME~TS. 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 the polyarylalkane compounds described herein incorporated into the aggregate photoconductive compo ~ -tions and elements of the invention can be varied over a relatively wide range. When used in an aggregate photoconductive composition the polyarylalkane compounds described herein or a mixture thereof should be in the continuous phase of the aggregate composition and may be present in an amount within the range of from about 1.0 to about 60.0 percent by weight, preferably from about 5.0 to about 40.0 percent by weight, (based on the dry weight of the aggregate photoconductive composition). Larger or smaller amounts of the polyarylalkane compound may also be employed in aggregate photoconductive _ 1065126 compositions although best results are generally obtained when using an amount within the aforementioned preferred range- ;
In addition to electrographic elements containing the above-described aggregate photoconductive insulating 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 invention in the usual manner, i.e., by blending a dispersion or solution 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. Likewise, other 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, organic photoconductive insula~ing layers of the invention such as homogeneous organic photo-conductive compositions 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 invention can be selected from a wide variety of materials, including such materials as pyrylium dye salts including thiapyrylium dye materials and selenapyryliu~ dye salts dis-closed in VanAllan et 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~

- -: . - -1065126 `
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. 3,732,~01; mineral acids; carboxyllc acids, such as maleic acid, dichloroacetic acid, trichloroacetic acid and salicylic acid, sulfonlc and phosphoric acids, and various dyes, such as cyanine (including carbocyanine), mero-cyanine, diarylmethane, thiazine, azine, oxazine, xanthene, 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 selenapyrylium salts and thiapyrylium salts, and cyanine dyes including carbocyanine dyes.
Where a sensitizing compound is employed with the ~ , binder and organic photoconductor to ~orm a sensitized, non-aggregate containi~g organic photoconductive composition, it is the normal practice to mix a suitable amount of the sensi-tizing 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 sensitizer may, however, be employed - consistent with the practice of this invention. In preparing the non-aggregate organic photoconductive layers, no sensitizing compound is required to give photoconductivity in the layers ~which contain the photoconducting substances with respect to ultraviolet radiation sources,therefore, a sensitizer may not be required in a particular photoconductive layer of the invention depending upon the particular radiation source selected However, since relatively minor amounts of sensitizer are effective in (a) producing a layer exhibiting photoconductivity with respect to visible light and (b) substantially increasing the electrical - ~ . ~ , . .... .

~0651Z6 -speed of the layer, the use of a sensitizer is generally preferred. The amount of sensitizer that can be added to a photoconductor-incorporating layer to give effective increases in speed can vary widely. The optimum concentration in any give~ case will vary with the speci~ic 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 com-position, with an amount of from about 0.005 to about 10 percent by weight being typical.
Preferred binders for use in preparing the presentnon-aggregate organic photoconductive layers are film-forming, hydrophobic polymeric binders having fairly high dielectric s~rength and good electrical insulating properties.

Typical o~ ~hcse mat~rills arc: ~ -I Natural resins including gelatin, cellulose -~
ester derivatives such as alkyl esteræ of carboxylated cellulose, hydroxy ethyl cellulose, carboxy methyl celluloæe, carboxy methyl hydroxy ethyl eellulose, etc.;
II. Vinyl resins including a. polyvinyl esters sueh as a vinyl acetate resin, a copolymer of vinyl aeetate and crotonic acid, a copolymer of vinyl aeetate with an ester of vinyl alcohol and a higher aliphatic carboxylie aeid sueh as laurie aeid or stearie aeid, polyvinyl stearate, a eopolymer of vinyl aeetate and maleie aeid, .

1065126 ~ ~
a poly(vinylhaloarylate) such as poly(vinyl- ;~
m-bro benzoate-covinyl acetate), a ter- -~
polymer of vinyl butyralwith 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 ~inyl chloride and vinyl acetate, etc.;
c. styrene polymers such as poly~tyrene, 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 l,3-disulfobenzene and 2,2-bis(4-hydroxyphenyl)propane;

. .

106S126 ~
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 giycol, neopentyl, glycol, terephthalic acid and iso-phthalic 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.;

1065~Z6 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, naphthalene, etc., including substituted aromatic hydrocarbons such as toluene, xylene, mesitylene, etc.;
2~ Ketones such as acetone, 2-butanone, etc., 3~ Halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, ~thylene chloride~ etc., 4~ Ethers including cyclic ethers such as tetra-hydrofuran, ethyl ether;

5) Mixtures of the above.
In preparing the non-aggregate-containing organic 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 1.0 weight percent of the composition. Typically, when the polyarylalkane compound used in the present invention is a primary or the only photo-conductor employed in the composition, the polyarylalkane compound is present in the composition~ the polyarylalkane compound is present in an amount equal to at least about 15 percent by weight based on the dry weight of the resultant photoconductive composition. The upper limit in the amount of photoconductive material present in the non-aggregate photo-3 conductive composition of the invention can be widely varied toat least 90~ by weight in accordance with usual practice.
Suitable supporting materials on which both the aggregate and non-aggregate photoconductive insulating layers of this invention can be coated include any of a wide variety of 106S~26 ~
electrically conducting supports, for example, paper (at arelative 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 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 deposited on trans-parent film supports in sufficiently thin layers to allow electro-photographic elements prepared therewith to be exposed from eitherside 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. Such conducting layers both with an~ without insùlating 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 - 20 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 both the aggregate and non-aggregate photoconductive composition of the invention on a suitable support can vary widely. Normally, a coating in the range of about lO 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 30 useful results can be obtained outside of this range. The re-sultant dry thickness of the coating is preferably between about 2 microns and about 50 microns, although useful results can be obtained with a dry coating thickness between about l and about 200 microns.

~06Si26 ~:
After the photoconductive elements prepared according to the present invention have been dried, they can be employed in any of the well-known electrophotographic processes which;
require photoconductive layers. One such process is the xero-graphic process. In a process of this type, an electrophoto-graphic element is held in the dark and given a blanket electro-static charge by placing it under a corona discharge. This uni-form charge is retained by the layer because 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 photoconductive layer is then selectively ~
dissipated from the surface of the layer by imagewise exposure ~` r'l,, ' to light by means of a conventional exposure operation such as, for example, by a contact printing technique, or by lens projec- -tion of an image, and the like, to thereby form a latent electro-static image in the photoconducti~e layer. Exposing the surface in this manner forms a pattern of electrostatic charge by virtue ^
o~ the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be con-ducted away from the surface in proportion to the intensity of the illumination in a particular area.
The charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charged or uncharged areas rendered visible, by treat~ent with a medium comprising electrostatically-responsive particles having optical density. The developing electrostatically-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 3~ electrostatic image for solid area development is by the use of a magnetic brush. Methods of forming and using a magnetic-brush, toner applicator are described in the following U.S.

P~tents: 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,o63 by Greig, issued February 17, 1959.
Liquicl 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 insulating 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 powde image then causes the resin to melt or fuse into or on the ele-ment. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other ca~es, a trans~er o~ 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. ~J~ , The electrical resistivity of the photoconductive insulatlng element of the invention (as measured across the photoconductive insulating composition of the element in the absence of activating radiation for the composition) should be at least about 109 ohm-cms. at 25C. In general, it is advantageous to use elements having a resistivity several order of magnitude higher than 101 ohm-cms., for example, elements having an electrical resistivity greater than about 1014 ohm-cms. at 25C.
The polyarylalkane compounds of formula I describedherein can, in general, be prepared by standard organic chemical synthetic procedures. Accordingly, extended description regard-ing the preparation of these polyarylalkane compounds is -?7-.. . . . . . . ...

~06S126 ;`. .
unnecessary herein. Briefly, it may be noted that the following chemical reaction equation represents one useful synthetic procedure for preparing many of the polyarylalkane compo~nds of formula I.

~4 ~ h6 ~ + Rl CR2 ..

Methane-sulfoni~ ~ N ~ C ~ 5 R4~ ~ ' 6 Acid R2 R

wherein Rl, R2, R3, and R4 are as defined hereinbefore.

To further illustrate the general reaction procedure outlined in reaction formula II above, the chemical synthesis of Gompound I of Table 1 i~ presented as ~ollows:
, .. .
In a 100 ml round-bottomed flask fitted with a water-cooled condenser with drying tube, and with a nitrogen-gas inlet, was placed a mixture of 4,4'-dimethyltriphenylamine, 20 g, cyclohexanone, 8.8 g, acetic acid, 30 mls, and methane-sulfonic acid, 0.5 g. A small current of nitrogen was passed I -through the mixture which was heated on the steam bath. All the solid went into solution, and the liquid turned blue.
The mixture was heated overnight, during which time a crystalline - :
solid was deposited. A small portion o~ the solid plus super-natant Iiquid was removed, dissolved in benzene, washed with dilute NaOh, separated, dried over K2C03 and examined by thin-layer chromatography using Eastman silica Chromagram ~ sheet ~with light ligroin as eluent. It was found that the product -~
was principally the desired compound. The whole of the remaining reaction mixture was dissolved in benzene and washed with dilute NaOH (the blue coloration turning to brown). The aqueous layer was separated off and re-extracted twice with a little benzene.

1()6S1~6 The combined benzene iayers were dried over K2503, filtered and evaporated down somewhat. Solvent loss was made up by replacement with ethanol, and crystallization was induced by seeding and scratching. The light-tan solid was ~iltered off and crystallized twice more from benzene-ethanol, m.p.
178.1-181.4. The off-white material was taken into solution ln benzene, treated hot with decolorizing charcoal, and filtered hot. The filtrate was evaporated down with replenishment of solvent with ethanol until spontaneous crystallization occurred. The white solid was filtered off and dried in a vacuum at 45, overnight. Yield 16.1 g, m.p.
181.4-182.4. ~ ;
A mass-spectrum analysis of the product revealed it to be the desired one having a molecular weight of 626.
The following examples are presented herein merely to illustrate, not to llmit, the present inventlon.

Example l Compound I of Table l was utilized as a photoconductor in the following three compositions.

Homogeneous Non-A~gregate Photoconductive Coating Composition I

Polyester binder (Vitel ~ PE lOl purchased from Goodyear Tire and Rubber Co.) - l.0 g. .`~
Compound I of Table 1 - 0.25 g.
2,6-bis(4-ethylphenyl)-4-(~-n-amyloxyphenyl)-thiapyrylium perchlorate - 0.01 g.
Dichloromethane - 9.6 g.
~.

-2~-; - .

iO~;5126 :
:`" ' Homo~2eneous Non-A~regate Photoconductive Coating Composition II ;
Polyester binder (Vitel ~ PE 101) - 1.0 g.
Compound I of Table 1 - 0.25 g.
4-(n Butylan3ino)_2-(4_methoxyphenyl)benzo~b]-pyrylium perchlorate - 0.02 g.

Dichloromethane - 9.6 g.

Aggregate Photoconductive Coating Composition I
Lexan ~ 145 (Bisphenol A polycarbonate sold by General Electric Co.) - 1.0 g.
Compound I of Table 1 - 0.25 g.
4-p Dimethylaminophenyl-2,6-diphenylthiapyrylium perchlorate - 0.025 g. (aggregated with Lexan~ 145 as described in Example 8 of U.S. 3,615,396).
Dichloromethane - 9.6 g.

The above-noted coating compositions were coated on a poly(ethylene terephthalate) base having an evaporated nickel conductive layer and the relative electrical speed of these -compositions was measured as shown in Table 2 The relative speed measurements reported in this and the following examples are relative H & D electr~cal speeds. The relative H & D electrical speeds measure the speed of a given photoconductive 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~ m e relative shoulder or toe speed, Rn, Or any o~her pl30toconductive material, n, relative to this value, Ro, may then be calculated as follows: Rn = (An)(R/Ao) wherein An is the absolute electrical speed of material n, Ro is the speed value arbitrarily assigned to the first material, anu --~0--1065~26 Ao is the absolu~e electrical speed of the first material. The abso~.ute l~ & D elec~rical speed, either the shoulder (SH) or toe speed, of a material may be determined as follows: The materi~l is electrostatically charged under, for example, a corona source un~il the surface pote~tial, as measured by an -`
electrolneter 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 measurement$ are then plotted on a graph of surface potential V vs. log exposure for each ~t~p, ~hereby forming an electrical characteristic curve. m~ electrical or electro-photographlc speed of the photoconductive composition can then be expressed in terms of the reclprocal of the exposure required to reduce the surface potential ~o any fixed selected value. rrhe actual positive or 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 V0 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 10 divided by the exposure in meter-candle-seconds required to reduce the 3 inLtial potential VO to an absolute value o~ 100 volts. Again, if one wishes to determine the 50 volt toe speed, one merely uses the exposure required to reduce VO to an absolute value ?~ ~

of 50 volts. An apparatus useful for determining the electro-photographic speeds of photoconductive compositions is described in Robinson et al, U.S. Patent No. 3,449,658, issued June 10, 1969.

Relative Electrical Speed Positive Negative Charging Charging Photoconductive (100 volt SH/ (100 volt SH/
10Compositions 100 volt toe) 100 volt toe) ~ .
Homogeneous I 15.5/l o 10/0 Homogeneous II 1.9/0 2.7/0 Aggregate I 3448/345 1379/86 * Arbitrarily assigned a speed value of 1.0 Exam~le 2 Two aggregate photoconductor formulations of the type described in Example 1 were prepared utilizing (at 20~ by weight~ -the control photoconductor 4,4'-bis(diethylamino)-2,2'-dimethyl-triphenylmethane in one, and in the other, the photoconductor described in Example 1 above. Each of these elements contained 2 percent by weight of 4-~-dimethylaminophenyl-2,6-diphenyl-thiapyrylium perchlorate aggregated with the Lexan ~ polycarbonate as in Example 1.
The electrophotographic sensitivity of each of these elements was determined by conventional techniques which involve low intensity, continuous exposures. It was noted that in the range of 25C to 105C, the positive exposure of materials con-taining the photoconductor of Example 1, exhibited a gradual increase in sensitivity with increasing temperature; the element containing the control photoconductor exhibited an increase in response in the range of 25C to 85C followed by a sharp decrease in sensitivity for temperatures above 85C to 90C.
It thus appeared that high levels of thermal stability and radiation sensitivity, particularly for the positive charging mode, can be obtained by the incorporation of the subaect ~
photoconductor into aggregated photoconductive compositions. ~-~xample 3 In the course of investigating the improved heat stability provided by the organic photoconductive materials employed in the organic photoconductive compositions of the present invention (as shown in preceding Example 2) it was found, unexpectedly, that the improvement in heat stability corresponded to the relatively high glass transition temperature, Tg, possessed by the materials used in the present invention.
To demonstrate the significance of the substantial differences in glass transition temperature existing between the organic photoconductive materials used in the present invention in comparison to certain known organic photoconductors having a similar molecular structure, a series of glass transition temperature measurements were performed and the following results were obtained as compiled in Table 2A below. As is apparent from Table 2A the materials used in the present 20 invention exhibit a significantly higher glass transition temperature in comparison to the known organic photoconductors having a similar molecular structure.

.. ..

-- ~06S126 bD
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h ~ C,) ~; V ~ ' o o o ~1 , O
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C~ ~ ~ ' .
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~ c U~ O ,~
~ O ~01 ~ q, ,, T
H o ~J /

v V~ 1 ~pD
7 ~
V~-V-V

rR ~ N ~ ~ lD N
O:~ o~ ~ ~J ^~J ~
C) ~; C) ~ ~ C) ~~o o v ~-- C`J a) v V
V ~ ~ ~ ~ a~ v ,~
rl' V ~ V
O O
0~
~; a) ~E~
O
V 4~ H H H H

_~
~n E~
h ~ ~:"
h . . . . :
~ V ' V oV V
E~ o ~ ~ ) ~ ~ ~
, ., ~, ~n : , ~d O~
E~ ~ -' ~
' O
C`J ':
~B ~ , ~ ,'~ ~ ~ p ~ p V~ p~
O ~ V V X 'i-` ' H
.~ V ~ . V~ ~ ~

~ ~ ~, z o a) ~ ~ ~V ~ v~
S~ V ~: 1~ V ~ , :

~ ~I h1~ ~ 0 ~ V 0 p )--V
V~ I ~ ~ V ~0 ~i~ o~; ~CU I O a) . ,i. . .
s~ ~ ~ ~ a) ~ o ~ ~ Q, i~
O ~ 0~ ~ 0~ ~ 0~ O
) ~ C~ ~ ~Q
~ ~o ta~o ~Q ~o ~Q C~l o v v v ^ a V ~
V ,~ V ,~ V ,~ p~ 0 ~ O
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8 ~ H H H
Vq~ p . .

106S~Z6 _~
.:
: .

.
E~ v v ~ Ll~
,o ~ ~o ..
.,, Z~a s~
E~
Z,~.
Z,~
~ Z~ ,~

Zl) ~0 ~0 '-~ ~,~ , ~ :
Z~, ~ ~

50r ~ ~- 0~ ~0/ C

W~

~1 ' .~
$ i, o~
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V ~. Z-Z X

1065~Z6 Example 4 Two aggregate photoconductor formulations of the type described in Example 1 were prepared utilizing (at 20% by weight) the control photoconductor 4,4'-tetramethyldiaminophenylmethane in o~e, and in the other, the photoconductor of the invention described in Example 1 above. Each of these elements con-tained 2 percent by weight of 4-~-dimethylaminophenyl-2,6-diphenylthiapyrylium perchlorate aggregated with the Lexan~
polycarbonate as in Example 1.
. 10 The relative electrical speeds of each of these elements was determined as described in Example 2 and are noted .
in Table 3. As shown in Table 3, the photoconductor of the type used in the present invention generally provided an .~:
aggregate photoconductive composition exhibiting higher speeds than could be obtained when the control photoconductor, 4,4'-tetramethyldiaminophenylmethane, was substituted in the aggregate photoconductive composition.
Table 3 Relative Electrical Speed . Positive Charging Negative Charging Photoconductive (100 volt'SH/ (100 volt SH/
Composition 100 volt toe) 100 volt toe .....
Aggregate Compo- . 11.6/1.0* 20/4.2 sition with control photoconductor Aggregate Compo- 83.4/8.3 33.3/2.1 sition with photo-conductor of the invention *Arbitrarily assigned a speed value of 1.0 ~065126 E~cam~le 5 As noted in preceding Example 3, an organic photocon-ductive composition having improved thermal stability can be ob-tained by using an organic photoconductor having a relatively high glass transition temperature. In this regard, the organic photoconductors used in the present invention have been found to possess a relatively high glass transition particularly when compared to structurally somewhat similar, prior art compounds such as N,N,N',N'-substituted-1,3-10 phenylenediamine and 4,4'methylene bis(N,N-dimethylaniline). ~;
For examplé, compounds I and II o~ Table I, two of the polyarylalkane compounds of the present invention, exhibit a glass transition temperature of about 82C and 72C, respectively. In contrast, N,N,N',N'-tetrabenzyl-1,3-phen~Jlenediamine, a prior art compound which is believed ~o be incorporated in certain commercial~y available electro-photographic compositions, possesses a glass transition temperature of only about 11C and 4,4'methylene bis(N,N-dimethylaniline) possesses a glass transition temperature of less than about 0C.
The invention has been described in detail with reference to certain preferred embodiments thereo~, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

-3~-... .. _ . _

Claims (19)

We Claim:

1. An organic photoconductive insulating composition comprising an electrically insulating polymeric binder and an organic photoconductive compound having the formula wherein R1 and R2, which may be the same or different, repre-sent, when taken separately, (i) hydrogen, (ii) an unsubstituted alkyl group or substituted alkyl group having 1 to about 18 carbon-atoms, said substituted alkyl having a substituent selected from the group consisting of alkoxy, aryloxy, amino, hydroxy, aryl, alkylamino, arylamino, nitro, cyano, halogen, and acyl or (iii) when taken together R1 and R2 represent the saturated carbon atoms necessary to complete a cycloalkyl ring having 3 to 10 carbon atoms in the cycloalkyl ring, R3, R4, R5, and R6, which may be the same or different, each represent an unsubstituted or substituted aryl group having a substituent selected from the group consisting of alkyloxy, aryloxy, amino, hydroxy, alkylamino, arylamino, nitro, cyano, halogen, alkyl, and acyl; and A1 and A2, which may be the same or different, repre-sent an unsubstituted phenyl group or a substituted phenyl having the substituents defined for R3, R4, R5 and R6 above.

2. A photoconductive composition as described in Claim l wherein said composition contains an amount of sensi-tizer effective to sensitize said composition.

3. An organic photoconductive insulating composition comprising an electrically insulating polymeric binder, an organic photoconductive compound, and an amount of sensitizer effective to sensitize said composition, said photoconductive compound having the formula wherein R1 and R2, which may be the same or different, represent, when taken separately, (i) hydrogen, (ii) an unsubstituted alkyl group or substituted alkyl group having 1 to about 18 carbon atoms, said substituted alkyl having a substituent selected from the group consisting of alkoxy, aryloxy, amino, hydroxy, aryl, alkylamino, arylamino, nitro, cyano, halogen, and acyl or (iii) when taken together, R1 and R2 represent the saturated carbon atoms necessary to complete a cycloalkyl ring having 3 to 10 carbon atoms in the cycloalkyl ring, R3, R4, R5, and R6, which may be the same or different, each represent an unsubstituted or substituted aryl group having a substituent selected from the group consisting of alkyloxy, aryloxy, amino, hydroxy, alkylamino, arylamino, nitro, cyano, halogen, alkyl, and acyl; and A1 and A2, which may be the same or different, represent an unsubstituted phenyl group or a substituted phenyl group having the substituents defined for R3, R4, R5 and R6 above.

4. A photoconductive composition as defined in Claim 3 wherein R1 and R2, taken together, represent the saturated carbon atoms necessary to complete a 6-member cycloalkyl ring and A1 and A2 represent unsubstituted phenyl groups.

5. A photoconductive composition as defined in Claim 3 wherein R3, R4, R5, and R6 each represent unsubstituted phenyl groups or alkyl substituted phenyl groups and A1 and A2 represent unsubstituted phenyl groups.

6. A photoconductive composition as defined in Claim 3 wherein said sensitizer is present in an amount of from about 0.005 to about 10 percent by weight of said composition and said organic photoconductive compound is present in an amount of from about 15 to about 90 percent by weight of said composition.

7. A photoconductive composition as defined in Claim 3 wherein said composition is a homogeneous composition having said organic photoconductive compound in solid solution with said polymeric binder.

8. An organic, homogeneous, photoconductive insulat-ing composition comprising an electrically insulating polymeric binder, an organic photoconductive compound in an amount equal to at least about 15 percent by weight of said composition, and a sensitizer for said composition in an amount within the range of from about 0.005 to about 10 percent by weight of said composition, said organic photoconductive compound in solid solution with said binder and having the formula wherein R1 and R2, which may be the same or different, represent, when taken separately, (i) hydrogen, (ii) an unsubstituted alkyl group or substituted alkyl group having 1 to about 18 carbon atoms, said substituted alkyl having a substituent selected from the group consisting of alkoxy, aryloxy, amino, hydroxy, aryl, alkylamino, arylamino, nitro, cyano, halogen, and acyl or (iii) when taken together, R1 and R2 represent the saturated carbon atoms necessary to complete a cycloalkyl group having 5 to 7 carbon atoms in the cycloalkyl ring, R3, R4, R5, and R6, which may be the same or different, each represent an unsubstituted or substituted aryl group having a substituent selected from the group consisting of alkyloxy, aryloxy, amino, hydroxy, alkylamino, arylamino, nitro, cyano, halogen, alkyl, and acyl; and A1 and A2, which may be the same or different, represent an unsubstituted phenyl group or a substituted phenyl group having the substituents defined for R3, R4, R5 and R6 above.

9. A homogeneous photoconductive composition as defined in Claim 8 wherein said organic photoconductive compound is selected from the group consisting of 1,1-Bis(4-di-p-tolylaminophenyl)cyclohexane; 2,2-Bis(di-p-tolylaminophenyl)-propane; 4,4'-Bis(di-p-tolylamino)-1,1,1-triphenylethane; 4,4'-bis(di-p-tolylamino)tetraphenylmethane; bis(4-di-p-tolylamino-phenyl)methane; bis(4-di-p-tolylaminophenyl)phenylmethane; 1,1-bis(4-di-p-tolylaminophenyl)-4-t-butylcyclohexane; 1,1-bis(4-di-p-tolylamlnophenyl)-2-methylpropane; 1,1-bis(4-di-p-tolyl-aminophenyl)ethane; and 1,1-bis(4-di-p-tolylaminophenyl)-3-methylbutane.

10. An organic, aggregate, photoconductive insulating composition comprising a continuous, electrically insulating binder phase containing (a) dissolved therein one or more photo-conductive compounds and (b) dispersed therein a particulate co-crystalline complex of (1) a dye salt selected from the group consisting of pyrylium, thiapyrylium, and selenapyrylium dye salts and (2) a polymer having an alkylidene diarylene moiety in a recurring unit thereof, at least one of said photoconductors having the formula wherein R1 and R2, which may be the same or different, repre-sent, when taken separately, (i) hydrogen, (ii) an unsubstituted alkyl group or substituted alkyl group having 1 to about 18 carbon atoms, said substituted alkyl having a substituent selected from the group consisting of alkoxy, aryloxy, amino, hydroxy, aryl, alkylamino, arylamino, nitro, cyano, halogen, and acyl or (iii) when taken together, R1 and R2 represent the saturated carbon atoms necessary to complete a cycloalkyl ring having 3 to 10 carbon atoms in the cycloalkyl ring, R3, R4, R5, and R6, which may be the same or different, each represent an unsubstituted or substituted aryl group as defined above for R1 and R2, and A1 and A2, which may be the same or different, represent an unsubstituted phenyl group or a substituted phenyl group having the substituents defined for R3, R4, R5 and R6 above.

11. An aggregate photoconductive composition as defined in Claim 10 wherein said dye salt is a 2,4,6-substituted thiapyrylium dye salt, Al and A2 represent unsubstituted phenyl groups, and R3, R4, R5 and R6 each represent an unsubstituted phenyl or an alkyl substituted phenyl group.

12. An organic, aggregate, photoconductive insulat-ing composition comprising a continuous, electrically insulating binder phase containing (a) dissolved therein one or more photo-conductive compounds and (b) dispersed therein a particulate co-crystalline complex of (1) a thispyrylium dye salt and (2) a carbonate polymer having a alkylidene diarylene moiety in a recurring unit thereof, at least one of said photoconductors having the formula wherein R1 and R2, which may be the same or different, repre-sent, when taken separately, (1) hydrogen, (11) an unsubstituted alkyl group or substituted alkyl group having 1 to about 18 carbon atoms, said substituted alkyl having a substituent selected from the group consisting of alkoxy, aryloxy, amino, hydroxy, aryl, alkylamino, arylamino, nitro, cyano, halogen, and acyl of (iii) when taken together, R1 and R2 represent the saturated carbon atoms necessary to complete a cycloalkyl ring having 5 to 7 carbon atoms in the cycloalkyl ring, R3, R4, R5, and R6, which may be the same or different, each represent an unsubstituted or substituted aryl group having a substituent selected from the group consisting of alkyloxy, aryloxy, amino, hydroxy, alkylamino, arylamino, nitro, cyano, halogen, alkyl, and acyl; and A1 and A2, which may be the same or different, represent an unsubstituted phenyl group or a substituted phenyl group having the substituents defined for R3, R4, R5 and R6 above.

13. An aggregate photoconductive composition as defined in Claim 12 wherein R1 and R2, taken together, represent the saturated carbon atoms necessary to complete a 6-member cycloalkyl ring and A1 and A2 represent unsubstituted phenyl groups.

14. An aggregate photoconductive composition as defined in Claim 12 wherein R3, R4, R5, and R6 each represent an unsubstituted phenyl group or an alkyl-substituted phenyl group, and A1 and A2 represent unsubstituted phenyl groups.

15. An aggregate photoconductive composition as defined in Claim 12 wherein at least one of said photoconductors is selected from the group consisting of 1,1-bis(4-di-p-tolyl-aminophenyl)cyclohexane; 2,2-bis(di-p-tolylaminophenyl)propane;
4,4'-bis(di-p-tolylamino)-1,1,1-triphenylethane; 4,4'-bis(di-p-tolylamino)tetraphenylmethane; bis(4-di-p-tolylaminophenyl)-phenylmethane; 1,1-bis(4-di-p-tolylaminophenyl)-4-t-butyl-cyclohexane; 1,1-b1s(4-di-p-tolylaminophenyl)-2-methylpropane;
1,1-bis(4-di-p-tolylaminophenyl)ethane; and 1,1-bis(4-di-p-tolylaminophenyl)-3-methylbutane.

16. An aggregate photoconductive composition as defined in Claim 12 wherein at least one of said photoconductors is 1,1-bis(4-di-p-tolylaminophenyl)cyclohexane.

17. In an electrophotographic element comprising a conductive support bearing an organic, photoconductive insu-lating layer, the improvement wherein said organic photoconductive insulating layer comprises the photoconductive composition of Claim 1.

18. In an electrophotographic element comprising a conductive support bearing an organic, photoconductive insulating layer, the improvement wherein said organic, photo-conductive insulating layer comprises the photoconductive composition of Claim 10.

19. In an electrophotographic process wherein an electrostatic charge pattern is formed on a photoconductive element comprised of an electrically conducting support bearing a layer of an organic, photoconductive insulating composition, the improvement wherein said organic, photoconductive insulating composition comprises an electrically insulating polymeric binder and an organic photoconductive compound having the formula wherein R1 and R2, which may be the same or different, represent, when taken separately, (i) hydrogen, (ii) an unsubstituted alkyl group or substituted alkyl group having 1 to about 18 carbon atoms, said substituted alkyl having a substituent selected from the group consisting of alkoxy, aryloxy, amino, hydroxy, aryl, alkylamino, arylamino, nitro, cyano, halogen, and acyl or (iii) when taken together, R1 and R2 represent the saturated carbon atoms necessary to complete a cycloalkyl ring having 3 to 10 carbon atoms in the cycloalkyl ring, R3, R4, R5, and R6, which may be the same or different, each represent an unsubstituted or substituted aryl group having a substituent selected from the group consisting of alkyloxy, aryloxy, amino, hydroxy, alkylamino, arylamino, nitro cyano, halogen, alkyl, and acyl; and A1 and A2, which may be the same or different, represent an unsubstituted phenyl group or a substituted phenyl group having the substituents defined for R3, R4, R5 and R6 above.