U.S. patent number 3,615,414 [Application Number 04/804,266] was granted by the patent office on 1971-10-26 for photoconductive compositions and elements and method of preparation.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to William A. Light.
United States Patent |
3,615,414 |
Light |
October 26, 1971 |
PHOTOCONDUCTIVE COMPOSITIONS AND ELEMENTS AND METHOD OF
PREPARATION
Abstract
Multiphase heterogeneous compositions are formed from an organic
dye and electrically insulating polymeric material. A solution of
dye and polymer is prepared and subsequently treated, for example,
by exposure of a coating thereof to a solvent to form the
heterogeneous compositions. These compositions which are useful as
photoconductors or electrophotosensitizers are characterized by a
radiation absorption maximum that is substantially shifted from the
absorption maximum of the dye dissolved in the polymer to form a
homogeneous composition. Particularly useful dyes are the pyrylium
dyes.
Inventors: |
Light; William A. (N/A,
NY) |
Assignee: |
Company; Eastman Kodak
(NY)
|
Family
ID: |
25188567 |
Appl.
No.: |
04/804,266 |
Filed: |
March 4, 1969 |
Current U.S.
Class: |
430/74; 430/75;
524/82; 549/13; 252/501.1; 430/91; 524/110; 549/426 |
Current CPC
Class: |
G03G
5/056 (20130101); G03G 5/0564 (20130101); G03G
5/0664 (20130101); G03G 5/043 (20130101) |
Current International
Class: |
G03G
5/043 (20060101); G03G 5/06 (20060101); G03G
5/05 (20060101); G03G 007/00 (); H01L 013/00 ();
C08G 051/04 () |
Field of
Search: |
;96/1.6,1,1.2,1.5,1.8
;252/501 ;260/40,345.1,327 ;106/307 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lesmes; George F.
Assistant Examiner: Wittenberg; M. B.
Parent Case Text
This application is a continuation-in-part of U.S. applications
Ser. No. 586,820, filed Oct. 14, 1966, now abandoned and Ser. No.
674,005, filed Oct. 9, 1967.
Claims
I claim:
1. A heterogeneous photoconductive composition comprising an
electrically insulating polymeric material having an alkylidene
diarylene moiety in the recurring unit, a pyrylium dye which has
been solubilized with said polymeric material and a photoconductor,
said composition being in the form of a multiphase organic solid
comprising a continuous phase of said polymeric material having
therein a particulate discontinuous phase containing a combination
of said dye and said polymeric material, the individual portions of
said discontinuous phase having a size of about 0.01 to 25 microns,
said composition having a maximum radiation absorption at a
wavelength at least about 10 m.mu. different from the wavelength of
maximum absorption of said dye solubilized with said polymeric
material in a homogenous composition.
2. The composition as described in claim 1 wherein said dye is
selected from the group consisting of a thiapyrylium dye salt, a
selenapyrylium dye salt and a pyrylium dye salt.
3. The composition as described in claim 1 wherein said insulating
polymeric material is selected from the group consisting of
carbonate polymers having an alkylidene diarylene moiety in the
recurring unit,
poly(4,4'-isopropylidene-dibenzyl-4,4'-isopropylidene dibenzoate)
and poly(4,4'-isopropylidene dibenzyl-4,4'-isopropylidene
dibenzoate).
4. A composition as described in claim 1 wherein said dye is
selected from the group consisting of perchlorate, fluoroborate and
p-toluenesulfonate salts of
4-[4-bis(2-chloroethyl)aminophenyl]-2,6-diphenylthiapyrylium.
5. A composition as described in claim 1 wherein said dye is
selected from the group consisting of perchlorate, fluoroborate and
p-toluenesulfonate salts of
4-(4-dimethylamino-phenyl)-2,6-diphenylthiapyrylium,
6. A composition as described in claim 1 wherein said dye is
selected from the group consisting of perchlorate, fluoroborate and
p-toluenesulfonate salts of
2,6-bis(4-ethyl-phenyl)-4-(4-dimethylaminophenyl)thiapyrylium.
7. A composition as described in claim 1 wherein said dye is
selected from the group consisting of perchlorate, fluoroborate and
p-toluenesulfonate salts of
4-(4-dimethylamino-phenyl)-2-(4-ethoxyphenyl)-6-phenylthiapyrylium.
8. A composition as described in claim 1 wherein said dye is
selected from the group consisting of perchlorate, fluoroborate and
p-toluenesulfonate salts of an anion selected from the group
consisting of
4-(4-dimethylamino-2-methylphenyl)-2,6-diphenylpyrylium,
4-[4-di(2-chloroethyl)aminophenyl]-2-(4-methoxyphenyl)-6-phenylthiapyryliu
m,
4-(4-dimethylaminophenyl)-2,6-diphenyl-thiaprylium,4-(4-dimethylaminopheny
l)-2,6-diphenylpyrylium,2-(2,4-dimethoxyphenyl)-4-(4-dimethylaminophenyl)be
nzo(b)pyrylium, and
4-4-dimethylaminophenyl)-2-(4-methoxyphenyl)-6-phenylthiapyrylium.
9. A heterogeneous photoconductive composition containing a dye
selected from the group consisting of pyrylium, thiapyrylium and
selenapyrylium dye salts and a hydrophobic carbonate polymer having
an alkylidene diarylene moiety in a recurring unit, said dye having
been solubilized with said polymer, said composition being in the
form of a multiphase organic solid comprising a continuous binder
phase of said polymer having dispersed therein a particulate
discontinuous phase comprising a combination of said dye and said
polymer, the individual portions of said discontinuous phase having
a size of about 0.01 to 25 microns, said composition having a
maximum radiation absorption at a wavelength at least about 10
m.mu. different from the wavelength of maximum absorption of said
dye solubilized with said carbonate polymer in a homogeneous
composition.
10. A composition as described in claim 9 wherein the pyrylium dye
has the formula:
wherein:
R.sub.1 and R.sub.2 are aryl radicals selected from the group
consisting of phenyl and substituted phenyl having at least one
substituent selected from the group consisting of an alkyl radical
of from 1 to 6 carbon atoms and an alkoxy radical of from 1 to 6
carbon atoms;
R.sub.3 is an alkylamino-substituted phenyl radical having from 1
to 6 carbon atoms in the alkyl moiety;
X is selected from the group consisting of sulfur and oxygen;
and
Z.sup.-is an anion:
and wherein the hydrophobic polymeric material is a film-forming
polymer containing the following recurring unit:
wherein:
R is a phenylene radical and
each of R.sub.4 and R.sub.5, when taken separately, is selected
from the group consisting of a hydrogen atom, alkyl radical of from
1 to 10 carbon atoms and a phenyl radical and Rj.sub.4 and R.sub.5,
when taken together, are the carbon atoms necessary to form a
cyclic hydrocarbon radical, the total number of carbon atoms in
R.sub.4 and R.sub.5 being up to 19.
11. An electrophotographic element comprising an electrically
conductive support having thereon at least one heterogeneous
photoconductive composition comprising an electrically insulating
polymeric material having an alkylidene diarylene moiety in the
recurring unit, a pyrylium dye which has been solubilized with said
polymeric material and a photoconductor, said composition being in
the form of a multiphase organic solid comprising a continuous
phase of said polymeric material having therein a particulate
discontinuous phase containing a combination of said dye and said
polymeric material, the individual portions of said discontinuous
phase having a size of about 0.01 to 25 microns, said composition,
when bearing an electrostatic charge on a surface thereof, being
capable of losing the charge in proportion to the intensity of
incident light striking said surface of the composition, the light
energy in meter-candle-seconds incident said surface capable of
causing a 100-volt reduction in said charge is not more than 200
meter-candle-seconds and said composition being characterized by an
ability to absorb radiation in a wavelength range different from
the wavelength range for a homogeneous composition containing said
dye solubilized with said polymeric material.
12. An element as described in claim 11 wherein the composition
contains an organic photoconductor different from said dye.
13. An element as described in claim 12, wherein said
photoconductor is 4,4'-benzylidenebis(N,N-diethyl-m-toluidine),
said dye being present in an amount of from about 0.001 to about 30
percent by weight of said composition and said dye being selected
from the group consisting of
4-(4-bis(2-chloroethyl)aminophenyl]-2,6-diphenylthiapyrylium
perchlorate; 4-(4-dimethylaminophenyl-2,6-diphenylthiapyrylium
perchlorate; 4-(4-dimethylaminophenyl-2,6-diphenylthiapyrylium
fluoroborate;
4-(4-dimethylamino-2-methylphenyl)2,6-diphenylpyrylium perchlorate;
4-(4-dimethyl-aminophenyl)-2,6-diphenylthiapyrylium
p-toluenesulfonate; 4-(4-dimethylaminophenyl)-2-(4-
methoxyphenyl)-6-phenylthiapyrylium perchlorate and
4-(4-dimethylaminophenyl)-2-(4-ethoxyphenyl)-6-phenylthiapyrylium
perchlorate.
14. A method for forming a composition which is capable of
responding to differences in light intensity by exhibiting a
differential conductivity when disposed to receive modulated
electromagnetic radiation comprising the steps of solubilizing a
pyrylium dye with a hydrophobic carbonate polymer having an
alkylidene diarylene moiety in a recurring unit, coating a layer of
the solubilized dye and polymer on a support, subjecting the layer
to solvent for said dye and polymer whereby a heterogeneous
two-phase material is formed in situ in said layer, said two phases
being visible under 2500X magnification, the continuous organic
binder phase of said carbonate polymer having dispersed therein a
discontinuous phase of said material containing a significant
portion of said dye in combination with said polymer and said
material having a maximum radiation absorption at a wavelength at
least about 10 m.mu.different from the wavelength of maximum
absorption of said dye solubilized with said polymer.
15. The method of claim 14, wherein the solvent used is a
halogenated hydrocarbon solvent.
16. The method of claim 14 wherein the coated layer is subjected to
the solvent in vapor form for a time sufficient to form the
heterogeneous two-phase material.
17. The method of claim 14 wherein the coated layer is subjected to
the solvent by overcoating with the solvent in liquid form for a
time sufficient to form the heterogeneous two-phase material.
18. A heterogeneous photoconductive composition containing an
electrically insulating polymeric material having an alkylidene
diarylene moiety in the recurring unit and a pyrylium dye which has
been solubilized with said polymeric material, said composition
being in the form of a multiphase organic solid comprising a
continuous binder phase of said polymeric material having dispersed
therein a particulate discontinuous phase comprising a combination
of said dye and said polymeric material, the individual portions of
said discontinuous phase having a size of about 0.01 to 25 microns,
said composition having a maximum radiation absorption at a
wavelength at least about 10 m.mu. different from the wavelength of
maximum absorption of said dye solubilized with said polymeric
material in a homogeneous composition.
19. A composition as described in claim 18 wherein the pyrylium dye
has the formula:
wherein:
R.sub.1 and R.sub.2 are aryl radicals selected from the group
consisting of phenyl and substituted phenyl having at least one
substituent selected from the group consisting of an alkyl radical
of from 1 to 6 carbon atoms and an alkoxy radical of from 1 to 6
carbon atoms;
R.sub.3 is an alkylamino-substituted phenyl radical having from 1
to 6 carbon atoms in the alkyl moiety;
X is selected from the group consisting of sulfur and oxygen;
and
Z.sup.-is an anion;
and wherein the polymeric material is a film-forming polymer
containing the following moiety in a recurring unit:
wherein:
each of R.sub.4 and R.sub.5, when taken separately, is selected
from the group consisting of a hydrogen atom, an alkyl radical of
from 1 to 10 carbon atoms and a phenyl radical, and R.sub.4 and
R.sub.5, when taken together, are the carbon atoms necessary to
form a cyclic hydrocarbon radical, the total of carbon atoms in
R.sub.4 and R.sub.5 being up to 19;
R.sub.6 and R.sub.7 are each selected from the group consisting of
hydrogen, alkyl radicals of from 1 to 5 carbon atoms, alkoxy
radicals of from 1 to 5 carbon atoms and a halogen; and
R.sub.8 is selected From the group consisting of divalent radicals
having the formulas: ##SPC11## 20.
20. An electrophotographic element comprising a conductive support
having coated thereon a heterogeneous photoconductive composition
comprising a polyarylalkane photoconductor, a carbonate polymer
having an alkylidene diarylene moiety in a recurring unit and an
organic dye selected from the group consisting of a pyrylium dye
salt and a thiapyrylium dye salt which has been solubilized with
said polymer, the continuous organic binder phase of said carbonate
polymer having dispersed therein; a discontinuous phase of said
composition comprising a combination of said dye and carbonate
polymer, the individual portions of said discontinuous phase having
a size of about 0.01 to about 25 microns, and said composition
having a radiation wavelength range of absorption different from
the wavelength range of absorption of a homogeneous composition
comprised of said dye solubilized in said polymer, said
heterogeneous composition when bearing an electrostatic charge on a
surface thereof being capable of losing said electrostatic charge
in proportion to the intensity of incident actinic radiation such
that the incident radiation energy in meter-candle-seconds required
to cause a 100-volt reduction in the charge is not greater than
about 200 meter-candle-seconds.
21. An electrophotographic element as described in claim 20 wherein
said carbonate polymer has an inherent viscosity no greater than
about 1.
22. In an electrophotographic process wherein an electrostatic
charge pattern is formed on a photoconductive element, the
improvement wherein said element has a photoconductive layer
comprising an organic photoconductor in a heterogeneous composition
comprising an electrically insulating polymeric material having an
alkylidene diarylene moiety in a recurring unit and a pyrylium dye
which has been solubilized with said polymer material, said
composition being in the form of a multiphase organic solid
comprising a continuous phase of said polymer material having
therein a particulate discontinuous phase containing a combination
of said dye and said polymer material, the individual portions of
said discontinuous phase having a size of about 0.01 to 25 microns,
said composition having a maximum radiation absorption at least
about 10 m.mu. different from the wavelength of maximum absorption
of said dye solubilized with said polymeric material in a
homogeneous composition.
23. A heterogeneous photoconductive composition comprising a
continuous organic binder phase having dispersed therein
photoconductive zinc oxide sensitized with a particulate
combination of a hydrophobic polycarbonate having an alkylidene
diarylene moiety in a recurring unit and a pyrylium dye selected
from the group consisting of a thiapyrylium, a pyrylium and a
selenapyrylium salt, said dye having been solubilized with said
polycarbonate, said particulate combination having a size of about
0.01 to 25 microns, and said sensitizer having a wavelength of
maximum radiation absorption which is at least 10 m.mu. different
from the radiation absorption maximum of said dye solubilized with
said polycarbonate.
24. An electrophotographic element comprising a conductive support
having thereon a layer of a heterogeneous photoconductive
composition comprising a continuous organic binder phase having
dispersed therein a discontinuous phase comprising an organic
photoconductor sensitized with a particulate combination of a
carbonate polymer having an alkylidene diarylene moiety in a
recurring unit and a thiapyrylium dye salt, said dye salt having
been solubilized with said carbonate polymer, said particulate
combination having a size of about 0.01 to 25.mu., and said
combination having a wavelength of maximum radiation absorption
which is at least 10m.mu. different from the radiation absorption
maximum of said dye dissolved with said carbonate polymer in a
homogeneous composition.
25. An electrophotographic element as described in claim 24 wherein
said dye salt is selected from the group consisting of fluoroborate
and perchlorate salts of
4-(4-dimethyl-aminophenyl)-2,6-diphenylthiapyrylium and
4-(4-dimethylamino-phenyl)-2-
(4-ethoxyphenyl-6-phenylthiapyrylium.
26. An electrophotographic element as described in claim 24 wherein
said carbonate polymer is poly(4,4'-isopropylidenediphenylene
carbonate).
Description
This invention relates to electrography and to photoconductive
compositions, elements and structures useful in electrography and
particularly in electrophotography. In addition, this invention
relates to providing novel electrophotographic compositions
together with methods for their preparation and use.
Electrophotographic imaging processes and techniques have been
extensively described in both the patent and other literature, for
example, U.S. Pat. Nos. 2,221,776; 2,277,013; 2,297,691; 2,357,809;
2,551,582; 2,825,814; 2,833,648; 3,220,324; 3,220,831; 3,220,833
and many others. Generally, these processes have in common the
steps of employing a normally insulating photoconductive element
which is prepared to respond to imagewise exposure with
electromagnetic radiation by forming a latent electrostatic charge
image. A variety of subsequent operations, now well known in the
art, can then be employed to produce a permanent record of the
image.
One type of photoconductive insulating structure or element
particularly useful in electrophotography utilizes a composition
containing a photoconductive insulating material dispersed in a
resinous material. A unitary electrophotographic element is
generally produced in a multilayer type of structure by coating a
layer of the photoconductive composition onto a film support
previously overcoated with a layer of conducting material or the
photoconductive composition may be coated directly onto a
conducting support of metal or other suitable conducting material.
Such photoconductive compositions have shown improved speed and/or
spectral response, as well as other desired electrophotographic
characteristics when one or more photosensitizing materials or
addenda are incorporated into the photoconductive composition.
Typical addenda of this latter type are disclosed in U.S. Pat. Nos.
3,250,615, 3,141,770 and 2,987,395. Generally, photosensitizing
addenda for photoconductive compositions are incorporated to effect
a change in the sensitivity or speed of a particular photoconductor
system and/or a change in its spectral response characteristics.
Such addenda can enhance the sensitivity of an element to radiation
at a particular wavelength or to a broad range of wavelengths where
desired. The mechanism of such sensitization is presently not fully
understood. The phenomenon, however, is extremely useful. The
importance of such effects is evidenced by the extensive search
currently conducted by workers in the art for compositions and
compounds which are capable of photosensitizing photoconductive
compositions in the manner described.
Usually the desirability of a change in electrophotographic
properties is dictated by the end use contemplated for the
photoconductive element. For example, in document copying
applications the spectral electrophotographic response of the
photoconductor should be capable or reproducing the wide range of
colors which are normally encountered in such use. If the response
of the photoconductor falls short of these design criteria, it is
highly desirable if the spectral response of the composition can be
altered by the addition of photosensitizing addenda to the
composition. Likewise, various applications specifically require
other characteristics such as the ability of the element to accept
a high surface potential, and exhibit a low dark decay of
electrical charge. It is also desirable for the photoconductive
element to exhibit high shoulder speed and high toe speed as
measured in an electrical H and D or characteristic curve, a low
residual potential after exposure, and resistance to fatigue. H and
D curves as referred to herein are analogous to the curves first
employed by Hurter and Driffield except that voltage or charge on
the electrophotographic element is used instead of density.
Sensitization of many photoconductive compositions by the addition
of certain dyes selected from the large number of dyes presently
known has hitherto been widely used to provide for the desired
flexibility in the design of photoconductive elements in particular
photoconductor-containing systems. At the present time, however, no
photosensitizer addenda to photoconductor compositions or elements
have been shown to the art which are capable of producing a
significant improvement in substantially all of the aforementioned
desirable characteristics. Conventional dye addenda to
photoconductor compositions have generally shown only a limited
capability for overall improvement in the totality of
electrophotographic properties which cooperate to produce a useful
electrophotographic element or structure. The art is still
searching for improvements in shoulder and toe speeds, rapid
recovery and useful electrophotographic speed from either positive
or negative electrostatic charging. Thus far, dye sensitization
alone has not produced the quality of improvement in
photoconductor-containing systems which might be considered
satisfactory for the wide variety of electrophotographic
applications presently contemplated by workers in the art.
It is, therefore, an object of this invention to provide the art of
electrophotography with novel compositions of matter, methods for
their preparation and elements for their optimum employment.
It is a further object of this invention to substantially remove
the limitations encountered heretofore by novel means using
photosensitizing addenda for organic photoconductive materials in
the field of electrophotography. For example, it is an object of
this invention to provide photoconductive compositions and elements
having greater speed than has previously been obtainable with
conventional organic photoconductive compounds or compositions.
It is also an object of this invention to provide novel
photoconductive compositions and elements prepared therefrom which
show substantially improved resistance to fatigue and which
demonstrate substantially increased speed of recovery between
charging and exposure cycles.
It is likewise an object of this invention to provide novel
photoconductive elements having the aforementioned characteristics
which are well suited for use with either positive or negative
initial charging potentials thereby permitting a wide latitude in
the selection and use of image-toning means and compositions as
well as providing a greater degree of freedom in the selection of
the type of image to be reproduced than has previously been
possible.
It is still a further object of this invention to provide novel
photoconductive elements containing zinc oxide and having enhanced
electrophotographic properties.
The above and further objects and advantages of this invention will
become apparent from the following description of the
invention.
It has been discovered that many useful photographic sensitizing
dyes and mixtures of such dyes, can be combined with electrically
insulating polymers in solution and treated as described herein to
form a separately identifiable multiphase heterogeneous
composition. These heterogeneous compositions can be formed as
described herein. The feature composition thus formed has been
found to be useful as either a photoconductor or as a sensitizer in
electrophotographic compositions containing other
photoconductors.
A solution containing the constituents of the feature
electrophotographic compositions can be coated in the form of a
layer in a conventional manner onto a suitable support and the
formation of the composition of the invention achieved in situ in
the formed layer. One technique for converting a homogeneous
coating of dye and polymer to the present heterogeneous system is
by prolonged contact of the coating to vapors of solvent which is
capable of being absorbed in or penetrating the layers, the dye
being caused to migrate and form aggregates in a multiphase system.
Usually such vapor exposure is effective to permit formation of a
substantial amount of the feature compositions from the dye and
polymer in about two minutes at about 70.degree. F. Likewise,
inhibition of solvent removal in an otherwise normal coating
operation of a dope solution made up of the dye and polymer can
form the feature compositions. Similarly, immersing the homogeneous
coating in a solvent, or coating from an original solvent mixture
which contains a high boiling solvent which persists in the coating
during drying, are among other methods of forming the feature
compositions. Another suitable technique for forming the present
heterogeneous compositions involves high speed shearing of a
solution of dye and polymer in accordance with the procedure
described in copending Gramza application Ser. No. 674,006, filed
Oct. 9, 1967, now abandoned.
Observable heterogeneous structure in the present photoconductive
layers is indicative of the presence of the feature compositions.
The presence of such compositions in the layer permits the layer to
produce the hereinafter enumerated improved properties when used as
a photoconductor or as a photosensitizing addendum for other
photoconductors. The feature compositions when formed in situ in
the layer generally have an identifiable heterogeneous appearance
when viewed under at least 2500X magnification, although such
compositions may appear to be substantially optically clear to the
naked eye in the absence of magnification. In other compositions of
the invention there is a macroscopic heterogeneity. Suitably, the
dye-containing aggregate in the discontinuous phase in
predominantly in the size range of about 0.01 to 25 microns.
However, it should be noted that when the heterogeneous
compositions of the invention are used to sensitize a particulate
photoconductor, such as zinc oxide, another discontinuous phase
will be present which may not fall within this size range.
In general, the present heterogeneous compositions are two phase
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 contains a significant portion of the dye
present and generally a predominant portion of the dye present is
in the discontinuous phase. The dye in the discontinuous phase can
be considered as being in particulate form; however, that phase
need not be comprised wholly of dye. It is believed that in some
instances the discontinuous phase may be comprised of a
cocrystalline complex of dye and polymer. However, it is also
believed that all of the aggregates which can be formed in
accordance with this invention are not necessarily comprised of
both dye and polymer. Preferably, substantially all of the dye
present in the system is in the discontinuous phase. When the
present compositions are used in conjunction with an organic
photoconductor, the resultant photoconductive composition generally
contains only two phases as the photoconductor usually forms a
solid solution with the continuous polymer phase. On the other
hand, when the present multiphase compositions are used in
conjunction with a particulate photoconductor, three phases may be
present. In such a case, there would be a continuous polymer phase,
a discontinuous phase containing dye as discussed above and another
discontinuous phase comprised of the particulate photoconductor. Of
course, the present multiphase compositions may also contain
additional discontinuous phases.
The feature compositions of this invention have shown many useful
properties in the electrophotographic art. Electrophotographic
elements made with layers containing this new substance alone or
together with other photoconductive compounds and compositions are
broadly improved. The feature compositions of this invention can be
specifically identified by their effect as a photoconductive
material per se or upon other photoconductive materials as
sensitizers therefor. A particularly distinctive property
characteristic of electrophotographic elements having coated
thereon many of the compositions of the invention is an increased
photosensitivity irrespective of the polarity of surface charge
placed on the photoconductive element. Such photoconductive
elements exhibit high photosensitivity and photoconductivity as
well as good regeneration. The observed tendency of elements
containing the material of this invention to recover very rapidly
after charging and exposure is important in continuous or cyclic
electrophotographic applications. When a feature composition of the
invention is present in an electrophotographic element, the element
has an improved ability to repeatedly accept a high surface
potential after completion of a charge-expose-develop cycle. Such
elements can, therefore, be further characterized by their
resistance to the kind of electrical fatigue which is normally
characteristic of photoconductor-containing elements and which
prevents rapid reuse of such elements.
The prior art photoconductive layers can be prepared in a wide
variety of ways. Typically, a solution comprising a photoconductor,
a film-forming hydrophobic binder and a sensitizing dye can be
prepared as shown in U.S. Pat. No. 3,141,770 and cast or coated in
the manner taught therein, for example, in the form of a layer onto
a suitably prepared conducting support material. A layer prepared
in this manner absorbs radiation over a particular wavelength
region characteristic of the dye used and appears substantially
homogeneous under 2500X magnification. The electrophotographic
properties of these prior art photoconductive layers are adequate
for the preparation of a useful image when charged, exposed
imagewise and developed in the conventional manner. However,
according to this invention, a significant improvement in many of
the electrophotographic properties presently characteristic of
these types of materials, particularly a speed increase, is
provided by the formation of the feature nonhomogeneous multiphase
compositions of this invention. The wavelength of the radiation
absorption maximum characteristic of the heterogeneous compositions
is substantially shifted from the wavelength of the radiation
absorption maximum of the substantially homogeneous untreated
dye-polymer solid solution. The new absorption maximum
characteristic of the aggregates of this invention is not
necessarily an overall maximum for the system as this will depend
upon the relative amount of dye in the aggregate. Such an
absorption maximum shift in the formation of the present multiphase
heterogeneous systems is generally of the magnitude of at least
about 10 m.mu.. 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
cases the formation of the present heterogeneous compositions can
be more easily identified by viewing under magnification. To
prepare such an improved element a photoconductive layer prepared
as described above can be exposed to the vapor of an organic
solvent. For example, after about two minutes at room temperature
or about 70.degree. F. this treatment produces changes in the
layer. The color of the layer during treatment changes, e.g. from a
deep blue to a shade of red, and absorbs radiation in a wavelength
region different than the original material. When the
photoconductive layer is removed from the solvent vapor and viewed
under magnification, the layer containing the feature composition
has a two phase heterogeneous appearance.
A photoconductive layer of the invention transformed as above, in
addition to having undergone physical appearance changes, has also
undergone a conversion which imparts to the layer the novel
properties described herein such as an increased
electrophotographic speed, sometimes regardless of the polarity of
the original electrostatic charge. Sometimes the dark conductivity
of such transformed material is also lowered, and the layer can be
repeatedly charged and exposed with no apparent electrical fatigue.
Likewise, such feature photoconductive layers do not have a memory
or retain spurious images when subsequently charged and exposed.
The present photoconductive material can be rapidly charged and its
charge stability is high when subjected to high humidity or
repeated exposure and development.
Particularly useful dyes in the present invention are pyrylium
dyes, including pyrylium, thiapyrylium and selenapyrylium dye
salts, which are capable of forming sensitizing and photoconductive
compositions of this invention can be represented by the following
general formula:
wherein R.sup.a, R.sub.b, R.sup.c, R.sup.d, and R.sup.e can each
represent (a) a hydrogen atom; (b) an alkyl group typically having
from 1 to 15 carbon atoms, such as methyl, ethyl, propyl, isopropyl
butyl, tertiary butyl, amyl, isoamyl, hexyl, octyl, nonyl, dodecyl,
etc., (c) alkoxy groups like methoxy, ethoxy, propoxy, butoxy,
amyloxy, hexoxy, octoxy, and the like; and (d) aryl groups
including substituted aryl groups such as phenyl, 4-diphenyl,
alkylphenyls as 4-ethylphenyl, 4-propylphenyl, and the like,
alkoxyphenyls as 4-ethoxyphenyl, 4-methoxyphenyl, 4-amyloxyphenyl,
2-hexoxyphenyl, 2-methoxyphenyl, 3,4-dimethoxyphenyl, and the like,
.beta.-hydroxy alkoxyphenyls as 2-hydroxyethoxyphenyl,
3-hydroxyethoxyphenyl, and the like, 4-hydroxyphenyl, halophenyls
as 2,4-dichlorophenyl, 3,4-dibromophenyl, 4-chlorophenyl,
2,4-dichlorophenyl, and the like, azidophenyl, nitrophenyl,
aminophenyls as 4-diethylaminophenyl, 4-dimethylaminophenyl and the
like, napthyl; and vinyl substituted aryl groups such as styryl,
methoxystyryl, diethoxystyryl, dimethylaminostyryl,
1-butyl-4-p-dimethylaminophenyl-1,3-butadienyl,
.beta.-ethyl-4-dimethylaminostyryl, and the like; and where X is a
sulfur, oxygen or selenium atom, and Z.sup..sup.- is an anionic
function, including such anions as perchlorate, fluoroborate
iodide, chloride, bromide, sulfate, periodate, p-toluenesulfonate,
and the like. In addition, the pair R.sup.a and R.sup.b as well as
the pair R.sup.d and R.sup.e can together be the necessary atoms to
be complete an aryl ring fused to the pyrylium nucleus.
Typical pyrylium dyes for use in the present invention are listed
in table 1.
---------------------------------------------------------------------------
TABLE 1
Compound Number Name of Compound
__________________________________________________________________________
1 4-[4-bis(2-chloroethyl)aminophenyl]-2,6-diphenylthiapyrylium
perchlorate 2 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium
perchlorate 3 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium
fluoroborate 4
4-(4-dimethylamino-2-methylphenyl)-2,6-diphenylpyrylium perchlorate
5 4-[4-bis(2-chloroethyl)aminophenyl]-2-(4-methoxyphenyl)-6
iapyrylium perchlorate 6
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium sulfate 7
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium
p-toluenesulfonate 8 4-(4-dimethylaminophenyl)-2,6-diphenylpyrylium
p-toluenesulfonate 9
2-(2,4-dimethoxyphenyl)-4-(4-dimethylaminophenyl)-benzo(b
perchlorate 10
2,6-bis(4-ethylphenyl-4-(4-dimethylaminophenyl)-thiapyrylium
perchlorate 11
4-(4-dimethylaminophenyl)-2-(4-methoxyphenyl)-6-phenylthia
perchlorate 12
4-(4-dimethylaminophenyl)-2-(4-ethoxyphenyl)-6-phenylthiap r
perchlorate 13
4-(4-dimethylaminophenyl)-2-(4-methoxyphenyl)-6-(4-methylp rylium
perchlorate 14 4-(4-diphenylaminophenyl)-2,6-diphenylthiapyrylium
perchlorate 15 2,4,6-triphenylpyrylium perchlorate 16
4-(4-methoxyphenyl)-2,6-diphenylpyrylium perchlorate 17
4-(2,4-dichlorophenyl)-2,6-diphenylpyrylium perchlorate 18
4-(3,4-dichlorophenyl)-2,6-diphenylpyrylium perchlorate 19
2,6-bis(4-methoxyphenyl)-4-phenylpyrylium perchlorate 20
6-(4-methoxyphenyl)-2,4-diphenylpyrylium perchlorate 21
2-(3,4-dichlorophenyl)-4-(4-methoxyphenyl)-6-phenylpyrylium
perchlorate 22 4-(4-amyloxyphenyl)-2,6-bis(4-ethylphenyl)pyrylium
perchlorate 23 4-(4-amyloxphenyl)-2,6-bis(4-methoxyphenyl)pyrylium
perchlorate 24 2,4,6-triphenylpyrylium fluoroborate 25
2,6-bis(4-ethylphenyl)-4-(4-methoxyphenyl)pyrylium perchlorate 26
2,6-bis(4-ethylphenyl)-4-(4-methoxyphenyl)pyrylium fluoroborate 27
6-(3,4-diethoxystyryl)-2,4-diphenylpyrylium perchlorate 28
6-(3,4-diethoxy-.beta.-amylstyryl)-2,4-diphenylpyrylium
fluoroborate 29
6-(4-dimethylamino-.beta.-ethylstyryl)-2,4-diphenylpyrylium
fluoroborate 30 6-(1-n-amyl-4-p-dimethylaminophenyl
1,3-butadienyl)2,4-diphenylpyrylium fluoroborate 31
6-(4-dimethylaminostyryl)-2,4-diphenylpyrylium fluoroborate 32
6-(.alpha.-ethyl-.beta.,.beta.-dimethylaminophenyl
vinylene)-2,4-diphenylpyrylium fluoroborate 33
6-(1-butyl-4-p-dimethylaminophenyl-1,3-butadienyl)-2,4-dip ylium
fluoroborate 34 6-(4-dimethylaminostyryl)-2,4-diphenylpyrylium
perchlorate 35
6-[.beta.,.beta.-bis(4-dimethylaminophenyl)vinylene]-2,4-d yrylium
perchlorate 36 2,6-bis(4-dimethylaminostyryl)-4-phenylpyrylium
perchlorate 37
6-(.beta.-methyl-4-dimethylaminostyryl)-2,4-diphenylpyrylium
fluoroborate 38
6-(1-ethyl-4-p-dimethylaminophenyl-1,3-butadienyl-2,4-diph lium
fluoroborate 39
6-[.beta.,.beta.-bis(4-dimethylaminophenyl)vinylene]-2,4-d yrylium
fluoroborate 40
6-(1-methyl-4-p-dimethylaminophenyl-1,3-butadienyl)-2,4-di rylium
fluoroborate 41 4-(4-dimethylaminophenyl)-2,6-diphenylpyrylium
perchlorate 42 2,6-bis(4-ethylphenyl)-4-phenylpyrylium perchlorate
43 2,6-bis(4-ethylphenyl)-4-methoxyphenylthiapyrylium fluoroborate
44 2,4,6-triphenylthiapyrylium perchlorate 45
4-(4-methoxyphenyl)-2,6-diphenylthiapyrylium perchlorate 46
6-(4-methoxyphenyl)-2,4-diphenylthiapyrylium perchlorate 47
2,6-bis(4-methoxyphenyl)-4-phenylthiapyrylium perchlorate 48
4-(2,4-dichlorophenyl)-2,6-diphenylthiapyrylium perchlorate 49
2,4,6-tris(4-methoxyphenyl)thiapyrylium perchlorate 50
2,6-bis(4-ethylphenyl)-4-phenylthiapyrylium perchlorate 51
4-(4-amyloxyphenyl)-2,6-bis(4-ethylphenyl)thiapyrylium perchlorate
52 6-(4-dimethylaminostyryl)-2,4-diphenylthiapyrylium perchlorate
53 2,4,6-triphenylthiapyrylium fluoroborate 54
2,4,6-triphenylthiapyrylium sulfate 55
4-(4-methoxyphenyl)-2,6-diphenylthiapyrylium fluoroborate 56
2,4,6-triphenylthiapyrylium chloride 57
2-(4-amyloxyphenyl)-4,6-diphenylthiapyrylium fluoroborate 58
4-(4-amyloxyphenyl)-2,6-bis(4-methoxyphenyl)thiapyrylium
perchlorate 59
2,6-bis(4-ethylphenyl)-4-(4-methoxyphenyl)thiapyrylium perchlorate
60 4-anisyl-2,6-bis(4-n-amyloxyphenyl)thiapyrylium chloride 61
2-[.beta.,.beta.-bis(4-dimethylaminophenyl)vinylene]-4,6-d
hiapyrylium perchlorate 62
6-(.beta.-ethyl-4-dimethylaminostyryl)-2,4-diphenylthiapyrylium
perchlorate 63 2-(3,4,-diethoxystyryl)-4,6-diphenylthiapyrylium
perchlorate 64 2,4,6-trianisylthiapyrylium perchlorate 65
6-ethyl-2,4-diphenylpyrylium fluoroborate 66
2,6-bis(4-ethylphenyl)-4-(4-methoxyphenyl)thiapyrylium chloride 67
6[.beta.,.beta.-bis(4-dimethylaminophenyl)vinylene]-2,4-bi
lphenyl)pyrylium perchlorate 68
2,6-bis(4-amyloxyphenyl)-4-(4-methoxyphenyl)thiapyrylium
perchlorate 69
6-(3,4-diethoxy-.beta.-ethylstyryl)-2,4-diphenylpyrylium
fluoroborate 70
6-(4-methoxy-.beta.-ethylstyryl)-2,4-diphenylpyrylium fluoroborate
71 2-(4-ethylphenyl)-4,6-diphenylthiapyrylium perchlorate 72
2,6-diphenyl-4-(4-methoxyphenyl)thiapyrylium perchlorate 73
2,6-diphenyl-4-(4-methoxyphenyl)thiapyrylium fluoroborate 74
2,6-bis(4-ethylphenyl-4-(4-n-amyloxyphenyl)thiapyrylium perchlorate
75 2,6-bis(4-methoxyphenyl)-4-(4-n-amyloxyphenyl)thiapyrylium
perchlorate 76 2,4,6-tris(4-methoxyphenyl)thiapyrylium fluoroborate
77 2,4-diphenyl-6-(3,4-diethoxystyryl)pyrylium perchlorate 78
4-(4-dimethylaminophenyl)-2-phenylbenzo(b)selenapyrylium
perchlorate 79
2-(2,4-dimethoxyphenyl)-4-(4-dimethylaminophenyl)-benzo(b) rylium
perchlorate 80 4-(4-dimethylaminophenyl)-2,6-diphenylselenapyrylium
perchlorate 81
4-(4-dimethylaminophenyl)-2-(4-ethoxyphenyl)-6-phenylselen m
perchlorate 82
4-[4-bis(2-chloroethyl)aminophenyl]-2,6-diphenylselenapyrylium
perchlorate 83
4-(4-dimethylaminophenyl)-2,6-bis(4-ethylphenyl)-selenapyrylium
perchlorate 84
4-(4-dimethylamino-2-methylphenyl)-2,6-diphenylselenapyrylium
perchlorate 85
3-(4-dimethylaminophenyl)naphtho(2,1-b)selenapyrylium perchlorate
86 4-(4-dimethylaminostyryl)-2-(4-methoxyphenyl)benzo(b)selen m
perchlorate 87 2,6-di(4-diethylaminophenyl)-4-phenylselenapyrylium
perchlorate 88
4-(4-dimethylaminophenyl)-2-(4-ethoxyphenyl)-6-phenylthiap r
fluoroborate
__________________________________________________________________________
Preferred pyrylium dyes used in forming the feature aggregates are
pyrylium dye salts having the formula:
wherein:
R.sub.1 and R.sub.2 can each be phenyl radicals, including
substituted phenyl radicals having at least one substituent chosen
from alkyl radicals of from 1 to 6 carbon atoms and alkoxy radicals
having from 1 to 6 carbon atoms;
R.sub.3 can be an alkylamino-substituted phenyl radical having from
1 to 6 carbon atoms in the alkyl moiety including
dialkylamino-substituted and halogenated alkylamino-substituted
phenyl radicals;
X can be an oxygen or a sulfur atom; and
Z.sup..sup.- is the same above.
While the pyrylium dyes are preferred in preparing the present
two-phase heterogeneous systems, other photographic spectral
sensitizing dyes that activate light exposed areas of photographic
compositions can be utilized in the electrically insulating polymer
of the present system, such as the J-aggregated dyes disclosed in
copending Gilman and Heseltine U.S. application Ser. No. 804,267,
cofiled herewith and entitled PHOTOCONDUCTIVE COMPOSITIONS AND
ELEMENTS, including J-aggregates of cyanine, merocyanine and styryl
dyes such as anhydro-1-ethyl1'-sulfobutyl-2,2'-cyanine hydroxide,
2-(5,5'-dicyano-2,4-pentenylidene)-3-ethylbenzothiazoline and
2-p-diethylaminostyryl-3-ethyl-6-(2-oxo-1-pyrrolidinyl)benzothiazolium.
The term dye as used herein is meant to include organic materials
which absorb radiation in the visible range of the spectrum as well
as those materials which absorb in the near ultraviolet region of
the spectrum and in the infrared region of the spectrum. In
general, the term dye has reference to organic materials which
absorb radiation having a wavelength in the range of from about 300
to about 10.sup.5 m.mu., with most preferred materials having a
long wavelength maximum absorption in the range of from about 380
to about 1,000 m.mu..
Electrically insulating film-forming polymers suitable for the
formation of electrophotographic compositions containing the
feature aggregates of this invention include polycarbonates and
polythiocarbonates, polyvinyl ethers, polyesters,
poly-.alpha.-olefins, phenolic resins, and the like. Mixtures of
such polymers can also be utilized. Such polymers include those
which function in the formation of the aggregates of this invention
as well as functioning as binders for the sensitizer and
photoconductor. Typical polymeric materials from these classes are
set out in table 2.
---------------------------------------------------------------------------
TABLE 2
Number Polymeric Materials
__________________________________________________________________________
1 polystyrene 2 polyvinyltoluene 3 polyvinylanisole 4
polychlorostyrene 5 poly.alpha.-methylstyrene 6 polyacenaphthalene
7 poly(vinyl isobutyl ether) 8 poly(vinyl cinnamate) 9 poly(vinyl
benzoate) 10 poly(vinyl naphthoate) 11 polyvinyl carbazole 12
poly(vinylene carbonate) 13 polyvinyl pyridine 14 poly(vinyl
acetal) 15 poly(vinyl butyral) 16 poly(ethyl methacrylate) 17
poly(butyl methacrylate) 18 poly(styrene-co-butadiene) 19
poly(styrene-co-methyl methacrylate) 20 poly(styrene-co-ethyl
acrylate) 21 poly(styrene-co-acrylonitrile) 22 poly(vinyl
chloride-co-vinyl acetate) 23 poly(vinylidene chloride-co-vinyl
acetate) 24
poly(4,4'-isopropylidenediphenyl-co-4,4'-isopropylidenedic l
carbonate 25
poly[4,4'-isopropylidendbis(2,6-dibromophenyl)carbonate] 26
poly[4,4'-isopropylidenebis(2,6-dichlorophenyl)-carbonate] 27
poly[4,4'-isopropylidenebis(2,6-dimethylphenyl)carbonate] 28
poly(4,4'-isopropylidenediphenyl-co-1,4-cyclohexyldimethyl
carbonate) 29 poly(4,4'-isopropylidenediphenyl
terephthalate-co-isophthalate) 30 poly(3,3'-ethylenedioxyphenyl
thiocarbonate) 31 poly(4,4'-isopropylidenediphenyl
carbonate-co-terephthalate) 32 poly(4,4'-isopropylidenediphenyl
carbonate) 33 poly(4,4'-isopropylidenediphenyl thiocarbonate) 34
poly(2,2-butanebis-4-phenyl carbonate) 35
poly(4,4'-isopropylidenediphenyl carbonate-block-ethylene oxide) 36
poly(4,4'-isopropylidenediphenyl
carbonate-block-tetramethyleneoxide) 37
poly[4,4'-isopropylidenebis(2-methylphenyl)carbonate] 38
poly(4,4'-isopropylidenediphenyl-co-1,4-phenylene carbonate) 39
poly(4,4'-isopropylidenediphenyl-co-1,3-phenylene carbonate) 40
poly(4,4'-isopropylidenediphenyl-co-4,4'-diphenyl carbonate 41
poly(4,4'-isopropylidenediphenyl-co-4,4'-oxydiphenyl carbonate) 42
poly(4,4'-isopropylidenediphenyl-co-4,4'-carbonyl-diphenyl
carbonate) 43
poly(4,4'-isopropylidenediphenyl-co-4,4'-ethylenediphenyl
carbonate) 44 poly[4,4'-methylene bis(2-methylphenyl)carbonate] 45
poly[1,1-(p-bromophenylethane)bis(4-phenyl)carbonate] 46
poly[4,4'-isopropylidenediphenyl-co-sulfonyl
bis(4-phenyl)carbonate] 47 poly[1,1-cyclohexane
bis(4-phenyl)carbonate] 48
poly(4,4'-isopropylidenediphenoxydimethylsilane) 49
poly[4,4'-isopropylidene bis(2-chlorophenyl)-carbonate] 50
poly[.alpha.,.alpha.,.alpha.',.alpha.'-tetramethyl-p-xlene
bis(4-phenyl carbonate)] 51
poly(hexafluoroisopropylidenedi-4-phenyl carbonate) 52
poly(dichlorotetrafluoroisopropylidenedi-4-phenyl carbonate) 53
poly(4,4'-isopropylidenediphenyl 4,4'-isopropylidene-dibenzoate) 54
poly(4,4'-isopropylidenedibenzyl 4,4'-isopropylidene-dibenzoate) 55
poly(4,4'-isopropylidenedi-1-naphthyl carbonate) 56
poly[4,4'-isopropylidene bis(phenoxy-4-phenyl sulfonate)] 57
acetophenone formaldehyde resin 58 poly[4,4'-isopropylidene
bis(phenoxyethyl)-co-ethylene terephthalate] 59 phenol-formaldehyde
resin 60 polyvinyl acetophenone 61 chlorinated polypropylene 62
chlorinated polyethylene 63 poly(2,6-dimethylphenylene oxide) 64
poly(neopentyl-2,6-naphthalenedicarboxylate) 65 poly(ethylene
terephthalate-co-isophthalate) 66
poly(1,4-phenylene-co-1,3-phenylene succinate) 67
poly(4,4'-isopropylidenediphenyl phenylphosphonate) 68
poly(m-phenylcarboxylate) 69 poly(1,4-cyclohexanedimethyl
terephthalate-co-isophthalate) 70 poly(tetramethylene succinate) 71
poly(phenolphthalein carbonate) 72 poly(4-chloro-1,3-phenylene
carbonate) 73 poly(2-methyl-1,3-phenylene carbonate) 74
poly(1,1-bi-2-naphthyl thiocarbonate) 75 poly(diphenylmethane
bis-4-phenyl carbonate) 76 poly[2,2-(3-methylbutane)bis-4-phenyl
carbonate] 77 poly[2,2-(3,3-dimethylbutane)bis-4-phenyl carbonate]
78 poly 1,1-[1-(1-naphthylethylidene)]bis-4-phenyl carbonate 79
poly[2,2-(4-methylpentane)bis-4-phenyl carbonate] 80
poly[4,4'-(2-norbornylidene)diphenyl carbonate] 81
poly[4,4'-(hexahydro-4,7-methanoindan-5-lidene)diphenyl carbonate]
__________________________________________________________________________
Especially useful polymers for forming the present heterogeneous
compositions are compounds number 28, 30-47, 49, 51, 53, 54 and
76-81 as listed in table 2 above.
Included among the preferred polymers used for preparing the
two-phase heterogeneous compositions of the invention, including
copolymers, are those linear polymers having the following
recurring unit: ##SPC1##
wherein:
R.sub.4 and R.sub.5, when taken separately, can each be a hydrogen
atom, an alkyl radical such as methyl, ethyl, propyl, isopropyl,
butyl, tertiary butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl
and the like including substituted alkyl radicals such as
trifluoromethyl, etc. and an aryl radical such as phenyl and
naphthyl including substituted aryl radicals having such
substituents as a halogen, alkyl radicals of from 1 to 5 carbon
atoms, etc.; and R.sub.4 and R.sub.5, when taken together, can
represent the carbon atoms necessary to form a cyclic hydrocarbon
radical including cycloalkanes such as hexyl and polycycloalkanes
such as norbornyl, the total number of carbon atoms in R.sub.4 and
R.sub.5 being up to 19;
R.sub.6 and R.sub.7 can each be hydrogen, an alkyl radical of from
1 to 5 carbon atoms or a halogen such as chloro, bromo, iodo, etc.
and
R.sub.8 is a divalent radical selected from the following:
##SPC2##
Among the hydrophobic carbonate polymers particularly useful in
accordance with this invention are polymers comprised of the
following recurring unit:
wherein:
Each R is a phenylene radical including halo substituted phenylene
radicals and alkyl substituted phenylene radicals; and R.sub.4 and
R.sub.5 are described above. Such compositions are disclosed, for
example, in U.S. Pat. Nos. 3,028,365 and 3,317,466. Preferably
polycarbonates containing an alkylidene diarylene moiety in the
recurring unit such as those prepared with Bisphenol A and
including polymeric products of ester exchange between
diphenylcarbonate and 2,2-bis(4-hydroxyphenyl)-propane are used in
the practice of this invention. Such compositions are disclosed in
the following U.S. Pat. Nos. 2,999,750; 3,038,874; 3,038,879;
3,038,880; 3,106,544; 3,106,545; 3,106,546; and published
Australian Pat. Specification No. 19575/56. A wide range of
film-forming polycarbonate resins are useful, particularly
completely satisfactory results are obtained when using commercial
polymeric materials which are characterized by an inherent
viscosity of about 0.5 to 0.6. In addition, a high molecular weight
material such as a high molecular weight Bisphenol A polycarbonate
can be very useful. Preferably, such high molecular weight
materials have an inherent viscosity of greater than about 1 as
measured in 1,2-dichloroethane at a concentration of 0.25 g./100
ml. and a temperature of about 25.degree. C. The use of high
molecular weight polycarbonate, for example, facilitates the
formation of aggregate compositions having a higher dye
concentration which results in increased speeds.
Liquids useful for treating polymer-dye coatings to form the
aggregate or heterogeneous compositions of the invention can
include water, and a number of organic solvents such as aromatic
hydrocarbons, for example, benzene and toluene, ketones such as
acetone and ethylmethyl ketone, halogenated hydrocarbons such as
methylene chloride and alcohols like methyl, ethyl, and benzyl
alcohol, as well as mixtures of such solvents.
The present heterogeneous compositions are electrically insulating
in the dark such that they will retain in the dark an electrostatic
charge applied to the surface thereof. In addition, as mentioned
above, the present compositions are also photoconductive. This term
has reference to the ability of such compositions to lose a
retained surface charge in proportion to the intensity of incident
actinic radiation. In general, the term "photoconductive" as used
to describe the present heterogeneous compositions means that the
amount of incident radiation energy in meter-candle-seconds
required to cause a 100-volt reduction in retained surface
potential is not greater than about 200 meter-candle-seconds.
The heterogeneous compositions of this invention are typically
coated as a photoconductor or as a sensitizer onto a conventional
conducting support such as paper (at a relative humidity above 20
percent) including paper made more conductive by various coating
and/or sizing techniques or carrying a conducting layer such as a
conducting metal foil, a layer containing a semiconductor dispersed
in a resin, a conducting layer containing the sodium salt of a
carboxyester lactone of maleic anhydride and a vinyl acetate
polymer such as disclosed in U.S. Pat. Nos. 3,007,901 and
3,262,806, a thin film of vacuum deposited nickel, aluminum,
silver, chromium, etc., a conducting layer as described in U.S.
Pat. No. 3,245,833, such as cuprous iodide, and like kinds of
conducting materials. Such conducting materials can be coated in
any well known manner such as doctor-blade coating, swirling,
dip-coating, spraying, and the like. Other supports, including such
photographic film bases as poly(ethylene terephthalate),
polystyrene, polycarbonate, cellulose acetate, etc., bearing the
above conducting layers can also be used. The conducting layer can
be overcoated with a thin layer of insulating material selected for
its adhesive and electrical properties before application of a
photoconducting layer. Where desired, however, the photoconducting
layer can be coated directly on the conducting layer where
conditions permit to produce the unusual benefits described
herein.
When the present multiphase compositions of the invention are used
as photoconductive compositions, useful results are obtained by
using the described dyes in amounts of from about one to about 50
percent by weight of the coating composition. When the present
multiphase compositions are used as sensitizers for photoconductive
coatings, useful results are obtained by using the described dyes
in amounts of about 0.001 to about 30 percent by weight of the
photoconductive coating composition, although the amount used can
be widely varied. The upper limit in the amount of photoconductive
composition present in a sensitized layer is determined as a matter
of individual choice and the total amount of any photoconductor
used will vary widely depending on the material selected, the
electrophotographic response desired, the proposed structure of the
photoconductive element and the mechanical properties described in
the element. Lesser amounts of the present feature compositions can
be utilized as sensitizing amounts to increase the speed
sensitivity of other photoconductors than amounts that would be
used if the feature material were the only photoconductor
present.
Coating thicknesses of a photoconductive composition containing the
feature material of the invention can vary widely. More generally,
a wet coating in the range from about 0.005 inch to about 0.05 inch
on a suitable support material is used in the practice of the
invention. The preferred range of wet coating thickness was found
to be in the range from about 0.002 inch to about 0.030 inch.
The present invention can readily be used for enhancing the
sensitivity and extending the spectral range of sensitivity of a
variety of organic photoconductors and inorganic photoconductors
including both n- and P-type photoconductors. For example, the
present invention can be used in connection with organic, including
organometallic, photoconducting materials which have little or
substantially no persistence of photoconductivity. Representative
organometallic compounds are the organic derivatives of Group IIIa,
IVa, and Va metals such as those having at least one amino-aryl
group attached to the metal atom. Exemplary organometallic
compounds are the triphenyl-p-dialkylaminophenyl derivatives of
silicon, germanium, tin and lead, the tri-p-dialkylaminophenyl
derivatives of arsenic, antimony, phosphorus, bismuth boron,
aluminum, gallium, thallium and indium. Useful photoconductors of
this type are described in copending Goldman and Johnsom U.S. Pat.
application Ser. No. 650,664, filed July 3, 1967 and Johnsom
application Ser. No. 755,711, filed Aug. 27, 1968.
An especially useful class of organic photoconductors is referred
to herein as "organic amine" photoconductors. Such organic
photoconductors have as a common structural feature at least one
amino group. Useful organic photoconductors which can be spectrally
sensitized in accordance with this invention include, therefore,
arylamine compounds comprising (1) diarylamines such as
diphenylamine, dinaphthylamine, N,N'-diphenylbenzidine,
N-phenyl-1-naphthylamine,n-phenyl-2-napthylamine,n,n'-diphenyl-p-phenylene
diamine, 2-carboxy-5-chloro-4'-methoxydiphenylamine,
p-anilinophenol, N,N'-di-2-naphthyl-p-phenylenediamine, those
described in Fox U.S. Pat. 3,240,597, issued Mar. 15, 1966, and the
like, and (2) triarylamines including (a) nonpolymeric
triarylamines, such as triphenylamine,
N,N,N'-N'-tetraphenyl-m-phenylenediamine, 4-acetyltriphenylamine,
4-hexanoyltriphenylamine, 4-lauroyltriphenylamine,
4-hexyltriphenylamine, 4-dodecyltriphenylamine,
4,4'-bis(diphenylamino)benzil, 4,4'-bis(diphenylamino)benzophenone
and the like, and (b) polymeric triarylamines such as
poly[N,4"-(N,N',N'-triphenylbenzidine)], polyadipyltriphenylamine,
polysebacyltriphenylamine, polydecamethylenetriphenylamine,
poly-N-(4-vinylphenyl)diphenylamine, poly-N-(vinylphenyl)- .alpha.,
.alpha.'-dinaphthylamine and the like. Other useful amine-type
photoconductors are disclosed in U.S. Pat. No. 3,180,730, issued
Apr. 27, 1965.
Useful photoconductive substances capable of being sensitized in
accordance with this invention are disclosed in Fox U.S. Pat. No.
3,265,496, issued Aug. 9, 1966, and include those represented by
the following general formula:
wherein T represents a mononuclear or polynuclear divalent aromatic
radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl,
binaphthyl, etc.), or a substituted divalent aromatic radical of
these types wherein said substituent can comprise a member such as
an acyl group having from 1 to about 6 carbon atoms (e.g., acetyl,
propionyl, butyryl, etc.), an alkyl group having from 1 to about 6
carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy
group having from 1 to about 6 carbon atoms (e.g., methoxy, ethoxy,
propoxy, pentoxy, etc.), or a nitro group; M represents a
mononuclear or polynuclear monovalent aromatic radical, either
fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.), or a
substituted monovalent aromatic radical wherein said substituent
can comprise a member, such as an acyl group having from 1 to about
6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl
group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl,
propyl, butyl, etc.), an alkoxy group having from 1 to about 6
carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.), or a nitro
group; Q can represent a hydrogen atom, a halogen atom or an
aromatic amino group, such as MNH-; b represents an integer from 1
to about 12; and, R represents a hydrogen atom, a mononuclear or
polynuclear aromatic radical, either fused or linear (e.g., phenyl,
naphthyl, biphenyl, etc.), a substituted aromatic radical wherein
said substituent comprises an alkyl group, an alkoxy group, an acyl
group, or a nitro group, or a poly(4'-vinylphenyl) group which is
bonded to the nitrogen atom by a carbon atom of the phenyl
group.
Polyarylalkane photoconductors are particularly useful in producing
the present invention. Such photoconductors are described in U.S.
Pat. No. 3,274,000, French Pat, No. 1,383,461 and in copending
application of Seus and Goldman titled PHOTOCONDUCTIVE ELEMENTS
CONTAINING ORGANIC PHOTOCONDUCTORS, Ser. No. 627,857, filed Apr. 3,
1967, now U.S. Pat. No. 3,542,544. These photoconductors include
leuco bases of diaryl or triaryl methane dye salts,
1,1,1-triarylalkanes wherein the alkane moiety has at least two
carbon atoms and tetraarylmethanes, there being substituted an
amine group on at least one of the aryl groups attached to the
alkane and methane moieties of the latter two classes of
photoconductors which are nonleuco base materials.
Preferred polyarylalkane photoconductors can be represented by the
formula:
wherein each of D, E and G is an aryl group and J is a hydrogen
atom, an alkyl group, or an aryl group, at least one of D, E and G
containing an amino substituent. The aryl groups attached to the
central carbon atom are preferably phenyl groups, although naphthyl
groups can also be used. Such aryl groups can contain such
substituents as alkyl and alkoxy typically having 1 to 8 carbon
atoms, hydroxy, halogen, etc., in the ortho, meta or para
positions, ortho-substituted phenyl being preferred. The aryl
groups can also be joined together or cyclized to form a fluorene
moiety, for example. The amino substituent can be represented by
the formula
wherein each L can be an alkyl group typically having 1 to 8 carbon
atoms, a hydrogen atom, an aryl group, or together the necessary
atoms to form a heterocyclic amino group typically having 5 to 6
atoms in the ring such as morpholino, pyridyl, pyrryl, etc. At
least one of D, E, and G is preferably p-dialkylaminophenyl group.
When J is an alkyl group, such an alkyl group more generally has 1
to 7 carbon atoms.
Representative useful polyarylalkane photoconductors include the
compounds listed in table 3.
---------------------------------------------------------------------------
TABLE 3
Compound Number Name of Compound
__________________________________________________________________________
1 4,4'-benzylidene-bis(N,N-diethyl-m-toluidine) 2
4',4"-diamino-4-dimethylamino-2',2"-dimethyltriphenylmethane 3
4',4"-bis(diethylamino)-2,6-dichloro-2',2"-dimethyltriphe e 4
4',4"-bis-(diethylamino)-2',2"-dimethyldiphenylnaphthylmethane 5
2',2"-dimethyl-4,4',4"-tris(dimethylamino-)triphenylmethane 6
4',4"-bis(diethylamino)-4-dimethylamino-2',2"-dimethyltri hane 7
4',4"-bis(diethylamino)-2-chloro-2',2"-dimethyl-4-dimethy
phenylmethane 8
4',4--bis(diethylamino)-4-dimethylamino-2,2',2"-trimethyl methane 9
4',4"-bis(dimethylamino-2-chloro-2',2"-dimethyltriphenylmethane 10
4',4"-bis(dimethylamino)-2',2"-dimethyl-4-methoxytriphenyl e 11
bis(4-diethylamino)-1,1,1-triphenylethane 12
bis(4-diethylamino)tetraphenylmethane 13
4',4"-bis(benzylethylamino)-2',2"-dimethyltriphenylmethane 14
4',4"-bis(diethylamino)-2',2"-diethoxytriphenylmethane 15
4,4'-bis(dimethylamino)-1,1,1-triphenylethane 16
1-(4-N,N-dimethylaminophenyl)-1,1-diphenylethane 17
4-dimethylaminotetraphenylmethane 18
4-diethylaminotetraphenylmethane
__________________________________________________________________________
Another class of photoconductors useful in this invention are the
4-diarylamino-substituted chalcones. Typical compounds of this type
are low molecular weight nonpolymeric ketones having the general
formula:
wherein R.sub.1 and R.sub.2 are each phenyl radicals including
substituted phenyl radicals and particularly when R.sub.2 is a
phenyl radical having the formula:
where R.sub.3 and R.sub.4 are each aryl radicals, aliphatic
residues of 1 to 12 carbon atoms such as alkyl radicals preferably
having 1 to 4 carbon atoms or hydrogen. Particularly advantageous
results are obtained when R.sub.1 is a phenyl radical including
substituted phenyl radicals and where R.sub.2 is a
diphenylaminophenyl, dimethylaminophenyl or phenyl.
Other photoconductors which can be used with the present aggregate
compositions include rhodamine B, malachite green, crystal violet,
phenosafranine, cadmium sulfide, cadmium selenide, parachloronil,
benzil, trinitrofluoroenone, tetranitrofluoroenone, etc.
The following table 4 comprises a partial listing of U. S. Patents
disclosing a wide variety or organic photoconductive compounds and
compositions which can be improved with respect to speed,
sensitivity, and/or regeneration when incorporated into the feature
compositions and elements of this invention.
---------------------------------------------------------------------------
TABLE 4
Inventor U.S. Patent No.
__________________________________________________________________________
Hoegl et al. 3,037,861 Sues et al. 3,041,165 Schlesinger 3,066,023
Bethe 3,072,479 Klupfel et al. 3,047,095 Neugebauer et al.
3,112,197 Cassiers et al. 3,133,022 Schlesinger 3,144,633 Noe et
al. 3,122,435 Sues et al. 3,127,266 Schlesinger 3,130,046 Cassiers
3,131,060 Schlesinger 3,139,338 Schlesinger 3,139,339 Cassiers
3,140,946 Davis et al. 3,141,770 Ghys 3,148,982 Cassiers 3,155,503
Cassiers 3,158,475 Tomanek 3,161,505 Schlesinger 3,163,530
Schlesinger 3,163,531 Schlesinger 3,163,532 Hoegl 3,169,060 Stumpf
3,174,854 Klupfel et al. 3,180,729 Klupfel et al. 3,180,730
Neugebauer 3,189,447 Neugebauer 3,206,306 Fox 3,240,597 Schlesinger
3,257,202 Sues et al. 3,357,203 Sues et al. 3,257,203 Fox 3,265,496
Kosche 3,265,497 Noe et al. 3,274,000
__________________________________________________________________________
The composition of the present invention can be employed in
photoconductive elements useful in any of the well known
electrophotographic processes which require photoconductive layers.
One such process is the xerographic process. In a process of this
type, an electrophotographic element held in the dark is given a
blanket electrostatic charge by placing it under a corona discharge
to give a uniform charge to the surface of the photoconductive
layer. This charge is retained by the layer owing to 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 to light by means of a conventional 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 photoconductive layer. Exposing the
surface in this manner forms a pattern of electrostatic charge by
virtue of the fact that light energy striking the photoconductor
causes the electrostatic charge in the light struck areas to be
conducted 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 treatment with
a medium comprising electrostatically responsive toner particles.
The developing electrostatically responsive particles can be in
various forms such as small particles of pigment or in the form of
small particles comprised of a colorant in a resinous binder. A
preferred method of applying such dry toners to a latent
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. Pat. Nos. 2,786,439;
2,786,440; 2,786,441; 2,881,465; 2,874,063; 2,984,163; 3,040,704;
3,117,884; and Reissue 25,779. Liquid development of the latent
electrostatic image can 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. Pat No. 2,907,674 and in Australian
Pat. No. 212,315.
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 transfer of the electrostatic charge image formed on the
photoconductive layer can be made to a second support such as paper
which could 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 a number of U.S. and foreign patents,
such as U.S. Pat. Nos. 2,297,691 and 2,551,582 and in "RCA Review"
Vol. 15 (1954) pg. 469-484.
Processes such as described hereinbefore have found utility where
the photoconductive layer is either inexpensive and expendable such
as the various processes using photoconductive zinc oxide, or where
the photoconductive media is rapidly reusable such as vitreous
selenium. The feature compositions of this invention now permit a
large number of known organic photoconductive compounds and
compositions as well as inorganic materials to be employed in
xerographic processes where rapid repeated charging and exposing
are desired. For example, it is now possible with the advance
provided by the discovery of the compositions of this invention to
employ a closed loop or belt of reusable organic photoconductive
film in a xerographic process thereby permitting extremely rapid
reproduction of original images. In addition, photoconductive
compositions containing the feature material can, of course, be in
the form of coated plates and drums. With the discovery disclosed
herein, it is now possible to reproduce copy from a microfilm or
other original as rapidly as the state of the related mechanical
handling arts will permit.
The following examples are included for a further understanding of
the invention.
Example 1
Coatings of the invention are prepared by dissolving 6 g.
poly(4,4'-isopropylidenediphenyl carbonate) resin (a composition
formed from the reaction between phosgene and a
dihydroxydiarylalkane or from the ester exchange between
diphenylcarbonate and 2,2-hydroxphenylpropane, such as "Lexan 105"
polycarbonate resin, General Electric Company); 4 g. of
4,4'-benzylidenebis(N,N-diethyl-m-toluidine) photoconductor; and
0.2 g. of
4-[4-bis(2-chloroethyl)aminophenyl]-2,6-diphenylthiapyrylium
perchlorate sensitizer in a solvent mixture consisting of 85 g. of
dichloromethane and 5 g. of methanol by stirring the solids in the
solvent for 2 hours at about 70.degree. F. to form a solution. The
resulting solution is hand coated at .004-inch wet coating
thickness onto two separate strips of poly(ethylene terephthalate)
film support overcoated with a conducting layer containing the
sodium salt of a carboxyester lactone of maleic anhydride and vinyl
acetate polymer such as disclosed in U.S. Pat. No. 3,007,901. The
coating block is maintained at 70.degree. F. during coating. Both
coatings are allowed to dry, and only one of the coatings is taped
to a glass plate. This plate is immediately inverted over a bath of
dichloromethane with the coating in the vapors thereof and kept
there in room light at 70.degree. F. for about two minutes. During
this vapor treatment, an observable change takes takes place in the
color and general physical appearance of the coating. The
vapor-treated coating and the coating which was not vapor treated
are examined microscopically at 500X magnification. The
vapor-treated coating has acquired a granular appearance not
present in the nonvapor-treated coating. A spectrophotometric
transmission curve for the vapor-treated coating indicates that the
coating absorbed 75 percent of the incident radiation at a
principal absorption peak of 515 m.mu.. The coating which has not
been vapor treated absorbs 89 percent at an absorption peak of 555
m.mu.. It is noted that the absorption peak of the vapor-treated
coating has shifted to a shorter wavelength by 40 m.mu.from the 555
m.mu. peak characteristic of the coating which has not been vapor
treated. The actual positive electrical speeds of the converted
(vapor-treated) and unconverted (nonvapor-treated) coatings are
determined in the following manner. The element is
electrostatically charged under a corona source until the surface
potential, as measured by an electrometer probe, reaches about 600
volts. The charged element is then exposed to a 3,000.degree. K.
tungsten light source through a transparent continuous neutral
density or gray scale wedge. The exposure causes reduction of the
surface potential of the element under the neutral density wedge
from its initial potential, V.sub.o, to some lower potential, V,
whose exact value depends on the actual 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. The actual positive speed of the
element can then be expressed in terms of the reciprocal of the
exposure required to reduce the surface potential to any
arbitrarily selected value. Herein, unless otherwise stated, the
actual positive speed is the numerical expression of 10.sup.4
divided by the exposure in meter-candle-seconds required to reduce
the 600-volt charged surface potential to a value of 100 volts.
Measuring as described herein, it is found that the coating which
is vapor treated has a speed of 240 when initially charged
positively. The coating which is not vapor treated has a speed of
63 when initially charged positively and a speed of 35 when
initially charged negatively. The speeds and spectral
characteristics of the coatings described hereinbefore, and similar
coatings containing dyes other than
4-[4-bis(2-chloroethyl)aminophenyl]-2,6-diphenyl- thiapyrylium
perchlorate are tabulated in table 5. All of the converted or
heterogeneous coatings can be toned to produce visible images after
being charged and image-wise exposed, typical suitable toners being
disclosed in U.S. Reissue Pat. No. 25,136.
TABLE 5 ##SPC3## ##SPC4##
Example 2
The procedure for this example for preparing the photoconductive
coatings is generally the same as described in example 1 with the
following changes: The sensitizer,
4-[4-bis(2-chloroethyl)aminophenyl]-2,6-diphenylthiapyrylium
perchlorate, is replaced with the same amount of
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate
(compound No. 2, table 1). Two solutions are prepared, one in 90 g.
of dichloromethane solvent, the other in a solvent mixture
consisting of 85 g. of dichloromethane and 5 g. of methanol. Both
solutions are stirred and coated as in example 1. Upon drying the
coating prepared with dichloromethane as the sole solvent is
converted into a two phase heterogeneous material by exposing to
the vapors of dichloromethane solvent as in example 1. A
predominant portion of the dye present is in the particulate
discontinuous phase. The coating from the 85 g. dichloromethane, 5
g. methanol solution is not so treated. In addition to the
foregoing speed and spectral response changes, another sample of
the first converted coating shown below is coated on an element
having a nickel conducting layer and is repeatedly charged to a 600
v. potential and photodischarged to determine the resistance of the
coating to electrical fatigue. After 1,000 such cycles at a time
interval of 3 seconds between photodischarge and recharging, the
coating will accept a 550 v. potential under the same charging
conditions. The uncoverted coating in the same system will accept
only a 400 v. to 450 v. potential. Further cycling produces little
change in the ability of the converted coating to accept a high
surface potential while the unconverted coating continues to
deteriorate. The speeds and spectral characteristics for
compositions prepared as described above containing the same
sensitizer binder combination with variations in the organic
photoconductor used are tabulated in table 6.
TABLE 6 ##SPC5##
Example 3
Photoconductive compositions and elements are prepared by the
procedures of example 1, with the following changes: the
sensitizer,
4-[4-bis(2-chloroethyl)aminophenyl]-2,6-diphenylthiapyrylium
perchlorate, is replaced by the same amount of a mixture of
sensitizer dyes in each case. The speeds and spectral
characteristics for compositions containing sensitizer mixtures are
tabulated in table 7.
TABLE 7 ##SPC6##
The absorption shift of the two individual dyes contained in the
mixtures of the first and third coatings have in effect combined to
give a net absorption peak which is unchanged; however, the
absorption spectrum has changed.
Example 4
The procedure for this example is generally the same as the
procedure for the preparation of photoconductive compositions and
elements prepared as in example 1, with the following changes noted
hereinafter and in table 8. The sensitizer
4-[4-bis(2-chloroethyl)aminophenyl]-2,6-diphenylthiapyrylium
perchlorate is replaced by
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate in
each case. The speeds and spectral characteristics for compositions
in different polymers are tabulated in table 8.
TABLE 8 ##SPC7##
Example 5
An electrophotographic element is prepared by dissolving 9.5 g. of
the arylalkane polycarbonate described in example 1 and 0.5 g. of
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium fluoroborate
sensitizer dye in 70 g. of chloromethane solvent by stirring the
solids in the solvent for 2 hours at about 70.degree. F. A second
solution is prepared by dissolving 9.5 g. of the polycarbonate and
0.5 g. of 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium
fluoroborate in a solvent mixture consisting of 66.5 g.
dichloromethane and 3.5 g. of methanol by stirring the solids in
the solvent for 2 hours at about 70.degree. F. The first and second
solutions are then separately hand coated at 0.005-inch wet coating
onto a barrier or insulator overcoated conducting layer of cuprous
iodide coated on a poly(ethylene terephthalate) film base.
(Conducting layers with or without insulating overcoated barrier
layers of the type used herein are shown in U.S. Pat. No.
3,245,833). The coating block is maintained at 90.degree. F. when
solutions 1 and 2 are coated. After drying, the first coating is
treated with solvent vapor as in example 1 and each of the coatings
is examined microscopically at 500X magnification. It is noted that
the coating from the first solution has a granular appearance not
present in the second coating. In addition, at least a predominant
portion of the dye present in the first coating is contained in the
granular appearing discontinuous phase. The spectrophotometric
transmission curve for the first coating indicates that the coating
absorbs 93 percent of the incident radiation at an absorption peak
of 640 m.mu.. The second coating absorbs 94 percent at a peak of
580 m.mu.. It is noted that the absorption peak of the first
coating has shifted to a longer wavelength by 60 m.mu. from the 580
m.mu. which is characteristic of the second coating. The speeds of
these coatings are measured using the procedure described for
example 1. However, in this case, the speed of the coating is
determined on the basis of the reciprocal of the exposure required
to reduce the potential of the surface charge by 100 volts
(shoulder speed) as measured with an electrometer probe. It is
found that the first coating has a speed of 630 when initially
charged positively, and 1,200 when initially charged negatively.
The second coating has low speed when initially charged positively
or negatively. The speeds and spectral characteristics of coatings
made in this same manner, and which contain dyes other than
4-(4-dimethyl aminophenyl)-2,6-diphenylthiapyrylium fluoroborate
are tabulated in table 9.
---------------------------------------------------------------------------
TABLE 9
Converted Heterogeneous Coating
__________________________________________________________________________
max. % Shoulder Dye (m.mu.) Absorption Speed
__________________________________________________________________________
compound 2, table 1 685 82 +1100 and -1100 compound 1, table 1 520
88 +285 and -715 compound 12, table 1640 92 +565 and -400
__________________________________________________________________________
Example 6
The procedure of example 1 is generally repeated using as the
sensitizer 0.4 g. of
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate in
place of the
4-[4-bis(2-chloroethyl)-aminophenyl]-2,6-diphenylthiapyrylium
perchlorate. The polycarbonate resin, the photoconductor and the
sensitizer are dissolved in a solvent mixture of 52.5 g. of
dichloromethane and b 52.5 g. of 1,2-dichloroethane by stirring the
solids in the solvent for 2 hours at about 70.degree. F. The
resulting dope is then coated onto a conducting substrate and
converted into a two phase composition in the manner shown in
example 1. The substrate consists of an evaporated nickel film
coated on a poly(ethylene terephthalate) film base which is subbed
with a terpolymer of 2 weight percent itaconic acid, 13 weight
percent methyl acrylate and 85 weight percent vinylidene chloride.
The net density of the evaporated nickel film is about 0.10 and
resistivity of the substrate is about 10.sup.3 ohms/sq. This
photoconductive coating has an absorption peak at 675 m.mu. and
absorbs 94 percent of the incident radiation at this wavelength.
The positive and negative 3 second, 1,000 cycle regeneration of the
coating (measured as described in example 2) is excellent and the
positive and negative speeds measured as in example 1 are 3,200 and
3,500, respectively. The densities and resistivities of other metal
conducting substrates as well as the speeds and absorption of other
organic photoconductive coatings which are coated directly on these
metal substrates are tabulated in table 10. The photoconducting
layers show excellent regeneration properties and can be repeatedly
charged, exposed and toned.
TABLE 10 ##SPC8##
Example 7
The procedure of example 1 is repeated using as the dye
2,6-bis-(4-ethylphenyl)-4-(4-dimethylaminophenyl)thiapyrylium
perchlorate (Compound 10, table 1). After hand coating the
resulting solution, an overcoat of toluene is applied in place of
the solvent vapor treatment. Upon drying the feature composition is
formed. The absorption maximum is 570 m.mu. (87 percent absorption)
for the unconverted coating and 635 m.mu.(93 percent absorption),
respectively, for the converted coating. Speeds for the coatings
are determined for both positive and negative charging. The speeds
of the unconverted coating are ++100 and -56 whereas the converted
coating has speeds of +450 and -500.
Example 8
The procedure of example 1 is repeated using
4-(4-dimethylaminophenyl-2,6-diphenylthiapyrylium perchlorate as
the dye and 90 g. of dichloromethane as the solvent. Two coatings
are then formed as in example 1 without the subsequent vapor
treatment. The first coating is converted by covering immediately
after coating so as to restrict the rate of solvent evaporation.
The second coating is converted by immersing briefly in a bath of
benzene. After drying, comparisons between converted and
unconverted coatings are made. The unconverted coating has speeds
of +40 and -30, whereas the first converted coating has a speed of
+2,000 and -2,000, while the second converted coating has speeds of
+1,600 and -1,800.
Example 9
The procedure of example 1 is repeated using a solvent mixture
containing a high boiling solvent. The solvent mixture consists of
81 g. of dichloromethane and 9 g. of toluene. The mixture is coated
as in example 1 and allowed to dry at room temperature which
results in the solvent being in contact with the coating long
enough to cause conversion to the aggregate. The final converted
coating has positive and negative speeds of 1,800 and 2,100,
respectively.
The following two examples demonstrate the improved results
obtained by using a higher viscosity polycarbonate in forming the
heterogeneous compositions of the present invention.
Example 10
Control Coating
A 35.3-gram portion of a low viscosity Bisphenol A polycarbonate
having an inherent viscosity of about 0.56, 23.5 grams of
4,4'-benzylidenebis (N,N-diethyl-m-toluidine, and 1.2 grams of
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate are
dissolved in a solvent mixture comprised of 242 ml. of
dichloromethane and 150 ml. of 1,1,2-trichloroethane by stirring
the solids in the solvent for four hours at room temperature. The
resulting solution is then sheared in a water-jacketed high speed
shearing blender for 30 minutes in accordance with the procedures
described in copending Gramza application, U.S. Ser. No. 674,006,
filed Oct. 9, 1967. The water in the jacket of the blender is
maintained at 50.degree. F. during shearing. The sheared dope is
then coated at a coverage of 1 g./ft..sup.2 on a poly(ethylene
terephthalate) film base carrying a conductive layer of a sodium
salt of a polymeric lactone as described in U.S. Pat. NO.
3,260,706. The coating is allowed to dry and then examined
microscopically using transmitted light and 450X magnification. It
is noted that the coating is heterogeneous in nature. The
spectrophotometric transmission characteristics of the coating are
then measured and it is found that the coating absorbs 92 percent
of incident radiation at 690 m.mu., 80 percent at 600 m.mu.and 20
percent at 500 m.mu.. The electrophotographic speed of the coating
is then measured as in the previous examples and the positive and
negative 100-volt toe speeds of the coating are found to be 2,500
and 2,850, respectively for this control coating.
High Viscosity Coating
A second coating is made using 16.2 grams of Bisphenol A
polycarbonate having an inherent viscosity of 2.70 as measured in
1,2-dichloroethane, 10.8 grams of the above photoconductor and 3
grams of the above thiapyrylium dye. The solids are dissolved in a
solvent mixture comprises of 228 ml. of 1,2-dichlorethane and 213
ml. of dichloromethane by stirring into the solvents for four hours
at room temperature. The resulting solution is sheared in a
water-jacketed high speed shearing blender as in the control
coating while maintaining the water temperature at 50.degree. F.
The sheared dope is coated at a coverage of 1 g./ft..sup.2 on a
conducting substrate similar to that used in the control coating.
The coating is allowed to dry and examined microscopically using
transmitted light 450X magnification. It is noted that the coating
contains a very fine grain dense discontinuous phase. This
heterogeneous coating is much finer grained than the control
coating above. The coating is also examined visually with the
unaided eye and it is noted that the surface of the second coating
has very little orange peel as compared to the control coating. The
spectrophotometric transmission characteristics of the coating
absorbs over 90 percent of the incident radiation at all
wavelengths between 530 m.mu.and 700 m.mu. . The
electrophotographic speeds of the coating are measured as in the
previous example and it is found that the negative toe speed of
this coating is three times faster than the negative toe speed of
the control coating. The positive and negative toe speed of the
control coating. The positive and negative 100-volt toe speeds are
400 and 9,500, respectively.
Example 11
Coating A is prepared by dissolving 18 grams of the polycarbonate
binder of example 1 in 201 ml. of dichloromethane by stirring the
binder in the solvent for two hours at room temperature. The
resulting solution is placed in a water-jacketed high speed
shearing blender and 12 grams of photoconductive zinc oxide are
added to the solution which thereafter is sheared for ten minutes.
The water in the jacket of the blender is maintained at 70.degree.
F. during shearing. The sheared dispersion is hand-coated at a
0.008-inch wet coating thickness on a poly(ethylene terepthalate)
support having a 0.4 neutral density high vacuum evaporated nickel
conducting layer thereon. The coating block is maintained at a
temperature of 70.degree. F. during coating. Next, coating B is
prepared by dissolving 17.6 g. of the polycarbonate binder in 194
ml. of dichloromethane as previously. The resultant solution is
then placed in the jacketed high speed shearing blender with the
addition of 11.8 grams of photoconductive zinc oxide and the
mixture is sheared for 10 minutes with the water temperature being
maintained at 70.degree. F. After shearing, 0.6 grams of
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate and
13 ml. of methyl alcohol are simply stirred into the sheared
dispersion for 30 minutes at room temperature. The resulting
dispersion is hand coated at a 0.008-inch wet coating thickness on
a nickel-coated support as above. Next, coating C is prepared by
dissolving 17.6 grams of the above polymer and 0.6 grams of the
thiapyrylium dye of coating B in 201 ml. of dichloromethane by
stirring for two hours at room temperature. The resultant solution
is placed in a high speed shearing blender and sheared for 30
minutes after which 11.8 grams of photoconductive zinc oxide are
added to the blender followed by additional shearing for 5 minutes
with the water in the jacket of the blender being maintained at
70.degree. F. during shearing. The sheared dispersion is hand
coated as previously onto a similar conducting support. The
coatings, A, B, and C are dried in a laboratory oven at 60.degree.
C. for 16 hours. The electrophotographic speeds and spectral
characteristics for each of the three coatings are determined and
are tabulated in table 11 below:
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TABLE 11
Speed Negative Percent V.sub.o 100 V Coating .lambda.max (mu)
Absorption (Volts) Toe
__________________________________________________________________________
A unsensitized 300 10 B B 580 96 240 too slow to be measured C 685
95 270 225
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example 12
Coating A is prepared by dissolving 3.73 grams of Bisphenol A
polycarbonate, 6.07 grams of
phenyl-tri(p-diethyl-aminophenyl)stannane, and 0.2 grams of
4-(4-dimethylaminophenyl)-2,6-diphenylthiaphyrylium perchlorate in
a solvent mixture of 38.3 ml. of dichloromethane, 23.7 ml. of
1,1,2-trichloroethane, and 5.7 ml. of methanol by stirring the
solids in the solvent for 2 hours at 20.degree. C. The resulting
solution is hand coated on a nickel-coated subbed poly(ehtylene
terephthalate) support as described in example 6, held at a
temperature of 20.degree. C. Coating B is prepared by dissolving
3.73 grams of Bisphenol A polycarbonate, 6.07 grams of
phenyl-tri-(p-diethylaminophenyl)stannane and 0.2 grams of
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate in a
solvent mixture identical to that used for preparing Coating A.
Stirring is carried out in the same manner as above, after which
the solution is placed in a water-jacketed high speed shearing
blender while 20.degree. C. water is circulated through the jacket.
The sheared solution is then coated and dried in the same manner as
is done for Coating A. Coatings A and B are dried in a laboratory
oven held at 60.degree. C. for 16 hours. The electrophotographic
speeds and spectral characteristics are determined as in the above
examples and the values are shown in table 12 below.
TABLE 12 ##SPC9##
Example 13
An 8 g. portion of the binder of example 1 and 2 g. of
2,4,7-trinitro-9-fluorenone are dissolved in 67 ml. of
dichloromethane by stirring the solids in the solvent for 2 hours
at room temperature. The resulting solution is hand coated at an
0.006-inch wet coating thickness on 0.4 neutral density subbed
evaporated nickel substrate. The coating block is maintained at
70.degree. F. during coating. A second coating is prepared by
dissolving 7.85 g. of the above binder, 1.96 g. of
2,3,7-trinitro-9-fluorenone, and 0.2 g. of
4-(4-dimethylamonophenyl)-2,6-diphenylthiapyrylium perchlorate in a
solvent mixture consisting of 63.8 ml. of dichloromethane and 5.7
ml. of methyl alcohol by stirring the solids in the solvent for 2
hours at room temperature. The resulting solution is hand coated at
an 0.006-inch wet coating thickness on a poly(ethylene
terephthalate) film base carrying a conducting nickel layer as
above. The coating block is maintained at 70.degree. F. during
coating. A third coating is prepared by dissolving 7.85 g. of the
above binder, 1.96 g. of 2,4,7-trinitro-9-fluoronone, and 0.2 g. of
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate in a
solvent mixture consisting of 40.3 ml. of dichloromethane and 25
ml. of 1,1,2-trichloroethane by stirring the solids in the solvent
for 2 hours at room temperature. The resulting solution is placed i
in a jacketed, high-speed shearing blender and sheared for 30
minutes. The water in the jacket of the blender is maintained at
70.degree. F. while shearing. The sheared material is hand coated
as above. The coatings 1, 2, and 3 are dried in a laboratory oven
at 60.degree. C. for 16 hours. The 100 V. toe speeds and spectral
characteristics are determined for each of the coatings as in the
previous examples and the values are tabulated in table 13.
TABLE 13 ##SPC10##
Example 14
A control coating is prepared by dissolving 0.375 g. of
4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium fluoroborate,
4.5 g.
poly(4,4'-isopropylenediphenylcarbonate-block-oxytetramethylene)
and 3 g. of 4,4'-benzylidenebis(n,n-diethylm-toluidine 42.5 g. of
methylene chloride. The solution is coated on a conducting support
as in the preceding example. Next, a similar solution is prepared
followed by shearing in a water-jacketed high-speed shearing
blender for 30 minutes during which time the water in the jacket is
maintained at 70.degree. F. The sheared composition is coated as
above to form a second element. The absorption maximum for the
control coating is at 585 m.mu.; whereas, the maximum for the
converted second coating is at 690 m.mu.. The resultant second
element can be charged imagewise, exposed and developed as in
example 1 to form a visible image.
It will be apparent from the foregoing examples and description
that the compositions of the present invention can be used in
electrophotographic elements having many structural variations. For
example, the photoconductive composition can be coated in the form
of single layers or multiple layers on a suitable opaque or
transparent conducting support.
The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
* * * * *