U.S. patent application number 09/877763 was filed with the patent office on 2002-01-31 for novel polymer and photoconductive element having a polymeric barrier layer.
This patent application is currently assigned to NexPress Solutions, LLC. Invention is credited to Molaire, Michel F., O'Regan, Marie B., Sorriero, Louis J..
Application Number | 20020012862 09/877763 |
Document ID | / |
Family ID | 24297590 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020012862 |
Kind Code |
A1 |
Sorriero, Louis J. ; et
al. |
January 31, 2002 |
Novel polymer and photoconductive element having a polymeric
barrier layer
Abstract
In a photoconductive element comprising a conductive support,
e.g., an electrically conductive film, drum or belt on which a
negatively chargeable photoconductive layer is formed, an
electrical barrier layer is formed between the support and the
photoconductive layer. The barrier layer provides a high energy
barrier to the injection of positive charges but transports
electrons under an applied electric field. The barrier layer of the
invention transports charge by electronic rather than ionic
mechanisms and, therefore, is not substantially affected by
humidity changes. The barrier layer comprises a polyester-co-imide,
polyesterionomer-co-imide or polyamide-co-imide having covalently
bonded as repeating units in the polymer chain, aromatic
tetracarboxylbisimide groups of the formula: 1 wherein Ar.sup.1 and
Ar.sup.2 represent, respectively, tetravalent and trivalent
aromatic groups of 6 to 20 carbon atoms.
Inventors: |
Sorriero, Louis J.;
(Rochester, NY) ; O'Regan, Marie B.; (Santa
Barbara, CA) ; Molaire, Michel F.; (Rochester,
NY) |
Correspondence
Address: |
JAECKLE FLEISCHMANN & MUGEL, LLP
39 State Street
Rochester
NY
14614-1310
US
|
Assignee: |
NexPress Solutions, LLC
|
Family ID: |
24297590 |
Appl. No.: |
09/877763 |
Filed: |
June 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09877763 |
Jun 8, 2001 |
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09574775 |
May 19, 2000 |
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6294301 |
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Current U.S.
Class: |
430/64 ; 528/170;
528/172; 528/173; 528/183; 528/310; 528/322; 528/327; 528/332;
528/335; 528/350; 528/353 |
Current CPC
Class: |
G03G 5/142 20130101;
C08G 73/16 20130101; C08G 73/1082 20130101; C08G 73/14
20130101 |
Class at
Publication: |
430/64 ; 528/170;
528/172; 528/173; 528/183; 528/310; 528/322; 528/327; 528/332;
528/335; 528/350; 528/353 |
International
Class: |
G03G 015/04 |
Claims
We claim:
1. A photoconductive element comprising an electrically conductive
support, an electrical barrier layer and, solvent-coated over said
barrier layer a charge generation layer capable of generating
positive charges when exposed to actinic radiation, said barrier
layer comprising a condensation polymer that transports charge
primarily by electronic rather than ionic transport mechanisms,
said polymer being a polyester-co-imide, polyesterionomer-co-imide
or polyamide-co-imide and having as a repeating unit a planar,
electron-deficient aromatic tetracarbonylbisimide group.
2. A photoconductive element of claim 1 wherein said barrier layer
polymer has covalently bonded as repeating units in the polymer
chain, aromatic tetracarbonylbisimide groups of the structure:
58wherein Ar.sup.1 and Ar.sup.2 represent, respectively,
tetravalent and trivalent aromatic groups of 6 to 20 carbon
atoms.
3. A photoconductive element of claim 1 wherein the barrier layer
polymer has the formula: 59wherein Q represents one or more groups
selected from (a) alkylenedioxy, aromatic dicarboxyl and aromatic
diamino groups having 2 to 36 carbon atoms; 60and wherein Ar, Ar
and Ar independently represent tetravalent aromatic groups having 6
to 20 carbon atoms, Ar.sup.3 represents a trivalent aromatic group
having 6 to 20 carbon atoms; R.sup.1, R.sup.2, R.sup.3, R.sup.4,
R.sup.5 and R.sup.6 independently represent alkylene or alkyleneoxy
groups having 2 to 12 carbon atoms; L.sup.1, L.sup.2, L.sup.3,
L.sup.4, L.sup.5 and L.sup.6 independently represent O, C=O,
CO.sub.2 or NH; and Z.sup.1 and Z.sup.2 independently represent an
aliphatic or aromatic dicarbonyl group having 2 to 36 carbon atoms;
and X is O, C(CF.sub.3).sub.2, S=O, SO.sub.2; x and y represent
mole fractions, x being the mole fraction of the group that
contains Ar.sup.1 and y being the mole fraction of Z.sup.1, and x
is 0.05 to 1 and y is 0 to 0.95.
4. A solvent-coated photoconductive element of claim 3 wherein said
polymer is substantially insoluble in the solvent employed for
coating said charge generation layer under the coating conditions
employed.
5. A photoconductive element of claim 4 wherein said polymer is
substantially insoluble in dichloromethane.
6. A photoconductive element of claim 4 wherein said polymer is
substantially insoluble in ketones.
7. A photoconductive element of claim 4 wherein said polymer is
substantially insoluble in tetrahydrofuran.
8. A photoconductive element of claim 4 wherein said polymer is a
polyesterionomer-co-imide.
9. A photoconductive element of claim 4 wherein said polymer is a
polyamide-co-imide.
10. A photoconductive element of claim 3 wherein said polymer is
prepared from one or more of the diacids, dianhydrides and diesters
selected from terephthalic acid, isophthalic acid, maleic acid,
2,6-napthanoic acid, 5-t-butylisophthalic acid,
1,4-cyclohexanedicarboxylic acid,
1,1,3-trimethyl-3-(4-carboxyphenyl)-5-indancarboxylic acid,
dodecanedioic acid, 1-methylsuccinic acid, pyromellitic
dianhydride, maleic anhydride, dimethyl succinate, dimethyl
glutarate, dimethyl azelate, dimethyl adipate and dimethyl
sebacate.
11. A photoconductive element of claim 3 wherein said polymer is
prepared from an ionic monomer selected from
dimethyl-5-sodiosulfoisophthalate,
5-(4-sodiosulfophenoxy)isophthalate acid,
dimethyl-3-3'-iminobis(sodiosul- fonylbenzoate), and dimethyl-S
-(N-potassio-p-toluenesulfonamido)isophthal- ate.
12. A photoconductive element of claim 8 wherein the cation of said
ionic monomer is selected from lithium, sodium, potassium, cesium,
trimethylammonium, triethylammonium, diethylhydroxyethylammonium,
dihydroxyethylethylammonium, triphenylmethylphosphonium and
mixtures thereof.
13. A photoconductive element of claim 3 wherein said polymer is
prepared one or more diols or equivalents selected from ethylene
glycol, ethylene carbonate, 1,2-propanediol, 1-methyl-ethylene
carbonate, 2,2'-oxydiethanol, 1,4-butanediol, 1,6-hexanediol,
1,10-decanediol, 1,4-cyclohexanedimethanol,
2,2-dimethyl-1,3-propanediol, 4,4-isopropylidenebisphenoxyethanol
and tetraethylene glycol.
14. A photoconductive element of claim 3 wherein said bisimide
groups are selected from 1,2,4,5-benzenetetracarboxylic bisimides;
1,4,5,8-naphthalenetetracarboxylic bisimides;
3,4,9,10-perylanetetracarbo- xylic bisimides;
2,3,6,7-anthraquinonetetracarboxylic bisimides and
hexafluoroisopropylidene-2,2', 3,3'-benzenetetracarbonyl
bisimides.
15. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,4,5,8-naphthalenetetracarbonyl-bisimide-2-ethoxyethylene-co-2,-
2-dimethyl-1,3-propylene (50/50) isophthalate].
16. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[4,5,8-naphthalenetetracarbonyl-bisimide-2-ethoxyethylene-co-2,2--
dimethyl-1,3-propylene-co-ethylene (25/25/50) terephthalate].
17. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,4,5,8-naphthalenetetracarbonyl-bisimide-5-pentamethylene-co-et-
hylene (50/50) terephthalate].
18. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[2,2'-oxydiethylene-co-1,4,5,8-naphthalenetetracarbonyl-bisimide--
5-pentamethylene (75/25) isophthalate-co-5-sodiosulfoisophthalate
(80/20)].
19. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[2,2'-oxydiethylene-co-1,4,5,8-naphthalenetetracarbonyl-bisimide--
5-pentamethylene (75/25) isophthalate-co-5-sodiosulfoisophthalate
(60/40)].
20. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[2,2'-oxydiethylene-co-1,4,5,8-naphthalenetetracarbonyl-bisimide--
5-pentamethylene (75/25) isophthalate-co-5-sodiosulfoisophthalate
(50/50)].
21. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[2,2'-oxydiethylene-co-1,4,5,8-naphthalenetetracarbonyl-bisimide--
2-ethoxyethylene (80/20) isophthalate-co-5-sodiosulfoisophthalate
(80/20)].
22. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,4,5,8-naphthalenetetracarbonyl-bisimido-2-ethoxyethylene-co-2,-
2'-oxydiethylene (60/40) isophthalate-co-5-sodiosulfoisophthalate
(80/20)].
23. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,4,5,8-naphthalenetetracarbonyl-bisimido-2-ethoxyethylene-co-2,-
2'-oxydiethylene (80/20) isophthalate-co-5-sodiosulfoisophthalate
(80/20)].
24. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,4,5,8-naphthalenetetracarbonyl-bisimido-2-ethoxyethylene-co-2,-
2'-oxydiethylene (40/60) isophthalate-co-5-sodiosulfoisophthalate
(80/20)].
25. A photoconductive element of claim 3 wherein said condensation
polymer is poly[dodecamethylene-co-piperazino
(50/50)-1,1,3-trimethylphenylindane- -co-dodecamethylene
(50/50)]amide.
26. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,3,3-trimethylcyclohexylmethylene-1,4,5,8-naphthylenetetracarbo-
nylbis(imido-3-propylene)-co-dodecamethylene (20/80)]amide.
27. A photoconductive element of claim 3 wherein said condensation
polymer is poly [dodecamethylene-co-1,4-piperazino
(35/65)-1,4,5,8-naphthalenetet-
racarbonyl-bis(imido-3-propylene)-co-dodecamethylene
(90/10)]amide.
28. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,3,3-trimethylcyclohexane-1,5-methylene-1,4,5,8-naphthalenetetr-
acarbonyl-bis(imido-11-undecamethylene)]amide.
29. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,3,3-trimethylcyclohexane-1,5-methylene-dodecamethylene-co-1,4,-
5,8-naphthalene tetracarbonyl-bis(imido-11-undecamethylene)
(90/10)]amide.
30. A photoconductive element of claim 3 wherein said condensation
polymer is poly
[1,3,3-trimethylcyclohexane-1,5-methylene-1,4,5,8-naphthalenetetr-
acarbonyl-bis(imido-11-undecamethylene)-co-dodecamethylene
(60/40)]amide.
31. A photoconductive element of claim 3 wherein said condensation
polymer is poly [decamethylene-co-piperazino (70/30)
decamethylene-co-1,1,3-trime-
thyl-3(4-phenylindanyl-co-1,4,5,8-naphthylenetetracarbonyl-bisimidopropyle-
ne (50/30/20)]amide.
32. A photoconductive element of claim 3 wherein the barrier layer
comprising said condensation polymer is on a conductive support
which is an electroplated, seamless, flexible cylinder of
nickel.
33. A photoconductive element of claim 3 wherein the barrier layer
polymer comprises a blend of (a) said polymer that contains an
aromatic tetracarboxylbisimide group with (b) an aliphatic
copolyamide.
34. A photoconductive element of claim 3 wherein the thickness of
said barrier layer is greater than one micron.
35. A polyamide-co-imide of the formula: 61wherein Ar.sup.1
represents a tetravalent aromatic group of 6 to 20 carbon atoms; R
and R' independently represent alkylene or alkyleneoxy groups of 2
to 12 carbon atoms, R" and R'" independently represent alkylene
groups of 2 to 12 carbon atoms; x is a mole fraction from 0.05 to
1, y is a mole fraction from 0 to 0.95 and z is a mole fraction
from 0 to 0.95.
36. Poly[1,3,3-trimethylcyclomethylene
1,4,5,8-naphthalenetetracarbonyl-bi-
s(imido-3-propylene)-co-dodecamethylene (20/80)]amide.
37. Poly[dodecamethylene-co-1,4-piperazino (35/65)
1,4,5,8-napthalenetetra-
carbonyl-bis(imido-3-propylene)-co-dodecamethylene
(90/10)]amide.
38. Poly[1,3,3-trimethylcyclohexane-1,5-methylene
1,4,5,8-naphthalenetetra- carbonyl-bis(imido-11
-undecamethylene)]amide.
39. Poly[1,3,3-trimethylcyclohexane-1,5-methylene
dodecamethylene-co-1,4,5-
,8-naphthalenetetracarbonyl-bis(imido-11-undecarnethylene)
(90/10)]amide.
40. Poly[1,3,3-trimethylcycylohexane-1,5-methylene
1,4,5,8-naphthalenetetr-
acarbonyl-bis(imido-11-undecamethylene)amide-co-dodecamethylene
(60/40)]amide.
41. Poly[decamethylene-co-piperazino (70/30)
decamethylene-co-1,1,3-trimet-
hyl-3(4-phenylindanyl-co-1,4,5,8-naphthalenetetracarbonyl-bisimidopropylen-
e (50/30/20)]amide.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No.: 09/574,775, filed May 19, 2000 (Attorney
Docket No. 89158.049201).
FIELD OF THE INVENTION
[0002] This invention relates to electrophotography. More
particularly, it relates to novel polymers and a novel
photoconductive element that contains a polymeric electrical charge
barrier layer.
BACKGROUND OF THE INVENTION
[0003] Photoconductive elements useful, for example, in
electrophotographic copiers and printers are composed of a
conducting support having a photoconductive layer that is
insulating in the dark but becomes conductive upon exposure to
actinic radiation. To form images, the surface of the element is
electrostatically and uniformly charged in the dark and then
exposed to a pattern of actinic radiation. In areas where the
photoconductive layer is irradiated, mobile charge carriers are
generated which migrate to the surface and dissipate the surface
charge. This leaves in nonirradiated areas a charge pattern known
as a latent electrostatic image. The latent image can be developed,
either on the surface on which it is formed or on another surface
to which it is transferred, by application of a liquid or dry
developer containing finely divided charged toner particles.
[0004] Photoconductive elements can comprise single or multiple
active layers. Those with multiple active layers (also called
multi-active elements) have at least one charge-generation layer
and at least one n-type or p-type charge-transport layer. Under
actinic radiation, the charge-generation layer generates mobile
charge carriers and the charge-transport layer facilitates
migration of the charge carriers to the surface of the element,
where they dissipate the uniform electrostatic charge and form the
latent electrostatic image.
[0005] Also useful in photoconductive elements are charge barrier
layers, which are formed between the conductive layer and the
charge generation layer to restrict undesired injection of charge
carriers from the conductive layer. Various polymers are known for
use in barrier layers of photoconductive elements. For example, the
patent to Hung, U.S. Pat. No. 5,128,226, discloses a photoconductor
element having an n-type charge transport layer and a barrier
layer, the latter comprising a particular vinyl copolymer.
Steklenski, et al., U.S. Pat. No. 4,082,551, refers to Trevoy, U.S.
Pat. No. 3,428,451, as disclosing a two-layer system that includes
cellulose nitrate as an electrical barrier. Bugner et al., U.S.
Pat. No. 5,681,677, discloses photoconductive elements having a
barrier layer comprising certain polyester ionorners. Pavlisko et
al, U.S. Pat. No. 4,971,873, discloses solvent-soluble polyimides
as polymeric binders for photoconductor element layers, including
charge transport layers and barrier layers.
[0006] The known barrier layer materials have certain drawbacks,
especially when used with negatively charged elements having p-type
charge transport layers. Thus, a negative surface charge on the
photoconductive element requires the barrier material to provide a
high-energy barrier to the injection of positive charges (also
known as holes) and to transport electrons under an applied
electric field. Many known barrier layer materials are not
sufficiently resistant to the injection of positive charges from
the conductive support of the photoconductive element. Also, for
many known barrier materials the mechanism of charge transport is
ionic. The ambient humidity affects the water content of the
barrier material and, hence, its ionic charge transport mechanism.
A need exists for charge barrier materials that transport charge by
electronic rather than ionic mechanisms and that, therefore, are
not substantially affected by humidity changes.
[0007] Still further, a number of known barrier layer materials
function satisfactorily only when coated in thin layers. As a
consequence, any irregularities in the coating surface, such as
bumps or skips, can alter the electric field across the surface.
This in turn can cause irregularities in the quality of images
produced with the photoconductive element.
[0008] Accordingly, a need exists for a negatively chargeable
photoconductive element having a p-type photoconductor, and
including an electrical barrier layer that can be coated from an
aqueous or an organic medium, that has good resistance to the
injection of positive charges, that can be sufficiently thick that
minor surface irregularities do not substantially alter the field
strength and that resists hole transport over a wide humidity
range. Still further a need exists for photoconductive elements of
which the barrier layer is substantially impervious to or insoluble
in solvents used for coating other layers, e.g., charge generation
layers, over the barrier layer. In accordance with the present
invention, a novel photoconductive element and certain novel
polyamides that meet such needs are provided.
[0009] Photoconductive elements comprising a photoconductive layer
formed on a conductive support such as a film, belt or drum, with
or without other layers such as a barrier layer, are also referred
to herein, for brevity, as photoconductors.
BRIEF SUMMARY OF THE INVENTION
[0010] The photoconductive element of the invention comprises an
electrically conductive support an electrical barrier layer and,
solvent-coated over the barrier layer, a charge generation layer
that is capable of generating positive charge carriers when exposed
to actinic radiation. The electrical barrier layer, which restrains
the injection of positive charge carriers from the conductive
support, comprises a condensation polymer having as a repeating
unit a planar, electron-deficient, aromatic tetracarbonylbisimide
group that transports charge primarily by electronic rather than
ionic transport mechanisms. This barrier layer polymer is
substantial insoluble in the solvent for the charge generation
layer under the coating conditions employed. More specifically, in
the photoconductive element of the invention, said barrier layer
comprises a condensation polymer having covalently bonded as
repeating units in the polymer chain aromatic tetracarbonylbisimide
groups of the formula: 2
[0011] wherein Ar.sup.1 and Ar.sup.2 represent, respectively,
tetravalent and trivalent aromatic groups of 6 to 20 carbon
atoms.
[0012] Preferably, the barrier layer polymer in the photoconductive
element of the invention is a polyester-co-imide,
polyesterionomer-co-imi- de, or polyamide-co-imide that contains an
aromatic tetracarbonylbisimide group, and has the formula: 3
[0013] wherein Q represents one or more groups selected from
[0014] (a) alkylenedioxy, aromatic dicarboxy and aromatic diamino
groups having 2 to 36 carbon atoms; 4
[0015] and wherein Ar, Ar.sup.1 and Ar.sup.2 independently
represent tetravalent aromatic groups having 6 to 20 carbon atoms;
Ar.sup.3 represents a trivalent aromatic group having 6 to 12
carbon atoms; R.sup.1 and R.sup.2 independently represent alkylene
or alkyleneoxy groups having 2 to 12 carbon atoms; L.sup.1,
L.sup.2, L.sup.3, L.sup.4, L.sup.5 and L.sup.6 independently
represent O, CO, CO.sub.2, or NH; and Z.sup.1 and Z.sup.2
independently represent an alkylenedioxy or alkylenediamino group
having 2 to 36 carbon atoms; X is O, C(CF.sub.3).sub.2, S=O or
SO.sub.2; and x and y represent mole fractions, x being the mole
fraction of the group that contains Ar.sup.1 and y being the mole
fraction of the group, Z.sup.1; and wherein x is 0.05 to 1 and y is
0 to 0.95.
[0016] The present invention also includes as novel compositions of
matter the novel polyamides defined above.
THE DRAWINGS
[0017] The invention will be described in more detail by reference
to the drawings, of which
[0018] FIG. 1 is a schematic cross section, not to scale, of one
embodiment of a photoconductive element of the invention; and
[0019] FIGS. 2-5 are graphical plots of results obtained in testing
examples of the invention and comparative examples.
DETAILED DESCRIPTION OF THE INVENTION
[0020] As illustrated in FIG. 1, a photoconductive element of the
invention 10 comprises a polymeric film support 11. On this support
is coated an electrically conductive layer 12. Over the conductive
layer is coated a polymeric barrier layer 13 the composition of
which is indicated above and described more fully hereinafter. Over
the barrier layer is coated a charge generation layer 14, and over
the latter is coated a p-type charge transport layer 15, which is
capable of transporting positive charge carriers generated by layer
14 to dissipate negative charges on the surface 16 of the
photoconductive element 10.
[0021] The barrier and other layers of the photoconductive element
are coated on an "electrically-conductive support," by which is
meant either a support material that is electrically-conductive
itself or a support material comprising a non-conductive substrate,
such as support 11 of the drawing, on which is coated a conductive
layer 12, such as vacuum deposited or electroplated nickel. The
support can be fabricated in any suitable configuration, for
example, as a sheet, a drum, or an endless belt. Examples of
"electrically-conductive supports" are described in Bugner et al,
U.S. Pat. No. 5,681,677 which is incorporated herein by
reference.
[0022] The barrier layer composition can be applied by coating an
aqueous dispersion of the polymer on the electrically conductive
support using, for example, a technique such as knife coating,
spray coating, swirl coating, extrusion hopper coating, or the
like. After application to the conductive support, the coating can
be air dried. It should be understood, however, that, if desired,
the barrier layer polymers can be coated as solutions or
dispersions in organic solvents.
[0023] Typical solvents for solvent coating a photoconductive layer
charge generation layer over a charge barrier layer are disclosed,
for example, in Bugner et al., U.S. Pat. No. 5,681,677; Molaire et
al, U.S. Pat. No. 5,733,695; and Molaire et al, U.S. Pat. No.
5,614,342, all of which patents are incorporated herein by
reference. As these references indicate the photoconductive
material, e.g., a photoconductive pigment, is solvent coated by
dispersing it in a binder polymer solution. Commonly used solvents
for this purpose include chlorinated hydrocarbons such as
dichloromethane as well as ketones and tetrahydrofuran. A problem
with known barrier layer compositions is that such solvents for the
coating of the photoconductive or charge generation layer will also
dissolve or damage the barrier layer. An advantage of the barrier
layer compositions of the invention, especially those comprising a
polyesterionomer-co-imide or a polyamide-co-imide, is that they are
not substantially dissolved or damaged by chlorinated hydrocarbons
or the other commonly used solvents for photoconductor or charge
generation layers, at the temperatures and for the time periods
employed for coating such layers.
[0024] Certain of the barrier layer polymers of the invention can
be dissolved in mixtures of dichloromethane with a polar solvent
such as methanol or ethanol, as will be seen from working examples
hereinafter. However, the barrier layer polymers of the invention,
especially the polyester-ionomer-co-imide and polyamide-co-imide
species, do not dissolve substantially in chlorinated hydrocarbons,
e.g., dichloromethane or in ketones such as dialkylketones or in
tetrahydrofuran. By "substantially insoluble" is meant dissolving
to the extent of less than 0.1 mg/100 ml of solvent at 25.degree.
C. over a period of 5 minutes.
[0025] Another advantage of the polymers employed in barrier layers
in accordance with the invention is that in addition to their other
advantages they can be made from more readily available starting
materials than can the polyimides of Pavlisko et al U.S. Pat. No.
4,971,873 and that the starting materials can be selected to yield
a polymer that is either substantially insoluble or soluble in
particular solvents.
[0026] The preferred embodiments of the present invention comprise
multi-active photoconductive elements having separate charge
generation layers and charge transport layers; such elements
provide superior photographic speed and benefit the most from the
use of a barrier layer to restrain migration of positive charge
carriers from the conductive support.
[0027] However, it should be understood that the invention also
includes single layer photoconductive elements having a barrier
layer between the conductive support and the photoconductive layer.
Even with such single layer elements, the injection of positive
charges from the conductive support is a problem. Hence, the
inclusion of a barrier layer in accordance with the invention
provides a valuable improvement in such elements.
[0028] The compositions of, the locations and methods of forming
the photoconductive charge generating layer, the charge transport
layer and other components of the photoconductive element of the
invention can be as described in Bugner et al., U.S. Pat. No.
5,681,677 cited above and incorporated herein by reference.
[0029] A preferred conductive support for use in
electrophotographic copying machines and in laser copiers is a
seamless, flexible cylinder or belt of nickel which can be
electroplated or vacuum deposited on a polymeric cylinder or belt.
Such nickel conductive supports have important advantages but at
least one drawback for which the barrier layer compositions of the
invention provide a solution. The deposited nickel layers often
have bumps or other irregularities which, when the barrier layer is
thin, can cause an irregular field strength across the surface and
thus cause defects in the resulting image. As an advantage over
conventional barrier materials, the barrier materials of the
present invention can be formed as thick layers and still have the
desired properties. As a relatively thick layer, e.g., greater than
0.5 micron and preferably greater than one micron, the barrier
layer of the invention can compensate for irregularity in the
thickness of the nickel surface. Other useful supports include
belts or cylinders of stainless steel or copper.
[0030] The barrier layer polymer in the photoconductive element of
the invention, is a condensation polymer that contains as a
repeating unit a planar, electron-deficient aromatic
tetracarbonylbisimide group as defined above. More specifically,
the preferred barrier layer polymer comprises a polyester-co-imide,
polyesterionomer-co-imide, or polyamide-co-imide of formula I
above.
[0031] The barrier layer polymers in accordance with the invention
thus contain planar, electron-deficient aromatic, functionalized
bisimide groups in which the aromatic group is a tri- or
tetravalent benzene, perylene, naphthalene or anthraquinone
nucleus. In addition to the carbonyl groups, Ar, Ar.sup.1, Ar.sup.2
and Ar.sup.3 of formula I can have other substituents such as
alkyl, alkoxy, halo and the like.
[0032] Useful imides include
1,2,4,5-benzenetetracarboxylic-bisimides: 5
[0033] 1,4,5,8-naphthalenetetracarboxylic-bisimides: 6
[0034] 3,4,9,10-perylenetetracarboxylic-bisimides: 7
[0035] 2,3,6,7-anthraquinonetetracarboxylic-bisimides: 8
[0036] and hexafluoroisopropylidene-2,2',
3,3'-benzenetetracarboxylic-bisi- mides: 9
[0037] Especially preferred are naphthalenetetracarbonyl-bisimides
and perylenetetracarbonyl-bisimides. They transport electrons more
effectively than corresponding groups in formula I wherein Ar.sup.1
is a single ring. These moieties are especially useful when
incorporated into polyesters-co-imides, polyesterionomer-co-imides,
and polyamide-co-imides as the sole electron-deficient moiety or
when incorporated into such polymers in various combinations. The
mole percent concentration of the electron deficient moiety in the
polymer can range from 2.5% to 100%, the preferred range being 2.5%
to 75%.
[0038] Examples of specific dicarbonyl groups, alkylenedioxy groups
and alkylene groups that are suitable in the barrier layer polymers
for photoconductive elements of the invention are cited in Sorriero
et al, U.S. Pat. No. 5,266,429, incorporated herein by
reference.
[0039] The barrier layer polymers in accordance with the invention
are prepared by condensation of at least one diol or diamine
compound with at least one dicarboxylic acid, ester, anhydride,
chloride or mixtures thereof. Such polymers have a weight-average
molecular weight of 2,500 to 250,000, preferably 5,000 to
150,000.
[0040] The bisimide structure containing the tetravalent-aromatic
nucleus can be incorporated either as a diol or diacid by reaction
of the corresponding tetracarbonyl dianhydride with the appropriate
amino-alcohol or amino-acid. The resulting bisimide-diols or
bisimide-diacids may then be polymerized, condensed with diacids,
diol, or diamines to prepare the barrier layer polymers by
techniques well-known in the art. The preferred technique is melt
phase polycondensation as described by Sorensen and Campbell,
"Preparative Methods of Polymer Chemistry," pp. 113-116 and 62-64,
Interscience Publishing, Inc. (1961) New York, N.Y.
[0041] Preferred diesters, diacids and dianhydrides for preparing
the barrier layer polymers include terephthalic acid, isophthalic
acid, maleic acid, 2,6-naphthanoic acid, 5-t-butylisophthalic acid,
1,4-cyclohexanedicarboxylic acid,
1,1,3-trimethyl-3-(4-carboxyphenyl)-5-i- ndancarboxylic acid,
pyromellitic dianhydride, maleic anhydride, dimethyl succinate,
dimethyl glutarate, dimethyl azelate, dimethyl adipate, dimethyl
sebacate, dodecanedioic acid, and 1-methylsuccinic acid.
[0042] Preferred diols and their equivalents for preparing the
barrier layer polymers include ethylene glycol, ethylene carbonate,
1,2-propanediol, 1-methyl-ethylene carbonate, 2,2'-oxydiethanol,
1,4-butanediol, 1,6-hexanediol, 1,10-decanediol,
1,4-cyclohexanedimethano- l, 2,2-dimethyl-1,3-propanediol,
4,4-isopropylidenebisphenoxyethanol and tetraethylene glycol.
[0043] The described polymers are all good film formers and exhibit
excellent adhesion to most of the substrates of interest. These
polymers resist attack by the solvent employed for the next film
layer, in this case the solvent for the charge-generation-layer
(CGL). Resistance to CGL solvent renders the barrier layer intact
and results in controlled thickness as well as reproducible film
electrical properties.
[0044] The following examples further illustrate the invention:
POLYESTER-CO-IMIDE EXAMPLES
[0045] The polyester-co-imide examples were all prepared by known
melt phase polycondensation techniques as documented by Sorenson et
al, cited above, pp. 113-116.
[0046] Polymer A:
[0047] Poly
[1,4,5,8-naphthalenetetracarbonyl-bisimido-2-ethoxyethylene-co- -2,
2-dimethyl-1,3-propylene (50/50) isophthalate].
[0048] A mixture of 194 g (1.00 mole) of dimethylisophthalate, 72.8
g (0.70 mole) of 2,2-dimethyl-1,3-propanediol, and 221 g (0.50
mole) of
1,4,5,8-naphthalenetetracarbonyl-bis(2-hydroxyethoxyethyl)imide
contained in a polymerization flask equipped with a Claisen head
and a nitrogen inlet tube was heated to 200.degree. C. under a
nitrogen atmosphere to produce a burgundy, transparent, homogeneous
melt. Then 1000 ppm of titanium isopropoxide catalyst were added,
and the temperature was slowly raised to 280.degree. C. over
several hours. Heating was continued until no further evolution of
methanol could be detected. A mechanical stirrer was introduced,
and the flask was connected to a source of vacuum. The mixture was
stirred under vacuum at 280.degree. C. for about two hours, then
cooled to room temperature. The polymerization product was removed
from the reaction vessel and submitted for assay. Polymer A has an
inherent viscosity in dichloromethane of 0.65 dl/g, a glass
transition temperature of 74.degree. C., and a weight average
molecular weight of 64,000.
[0049] Polymer B:
[0050] Poly
[1,4,5,8-naphthalenetetracarbonyl-bisimido-5-pentamethylene-co- -2,
2-dimethyl-1,3-propylene-co-ethylene (25/25/50) terephthalate].
[0051] A mixture of 194 g (1.00 mole) of dimethylterephthalate,
109.5 g (0.25 mole) of 1,4,5,8-naphthalenetetracarbonyl-bis
(5-hydroxypentyl)imide, 36.4 g (0.35 mole) of
2,2-dimethyl-1,3-propanedio- l, and 21.7 g (0.35 mole) of ethylene
glycol was combined in a polymerization flask as per polymer A. The
resulting polymer B had an inherent viscosity of 0.62 dl/g, a glass
transition temperature of 93.degree. C., and a weight average
molecular weight of 72,000.
[0052] Polymer C:
[0053] Poly
[1,4,5,8-naphthalenetetracarbonyl-bisimido-5-pentamethylene-co-
-ethylene (50/50) terephthalate].
[0054] A mixture of 194 g (1.00 mole) of dimethylterephthalate, 219
g (0.50 mole) of 1,4,5,8-naphthalenetetracarbonyl-bis
(5-hydroxypentyl)imide and 43.4 g (0.70 mole) of ethylene glycol
were combined in a polymerization flask as per polymer A. The
resulting polymer C had an inherent viscosity of 0.54 dl/g, a glass
transition temperature of 92.degree. C., and a weight average
molecular weight of 56,000.
[0055] The polyester-co-imide examples described above are listed
in Table I along with their respective responses to varying
relative humidity (RH). The responses are shown as weight percent
water loss, which changes the ionic conductivity of the
polymer.
1TABLE I POLYESTER-CO-IMIDES 10 % Water Loss From 70 F/60% RH
Polymer x y z R" R' R To 80 F/20% RH A 0.5 0 0.5 11 12 0.038 B 0.25
1.00 0.25 13 14 15 0.087 C 0.50 1.00 0.50 16 17 0.225
POLYESTERIONOMER-CO-IMIDE EXAMPLES
[0056] The polyesterionomer-co-imide examples were also prepared by
known melt phase polycondensation techniques as documented by
Sorensen et al, cited above, pp. 113-116.
[0057] The polyesterionomer-co-imides of the examples hereinafter
all contain the 5-sodiosulfoisophthalic acid moiety but the present
invention is not limited to the use of this ionic moiety. The
inventors have found, for example, that ionic esters such as
dimethyl-3,3'-iminobis-sodiosulfon- ylbenzoate,
dimethyl-5-(N-potassio-p-toluenesulfonylamido)sulfonyl-isophth-
alate, and dimethyl-5-(4-sodiosulfonyl)isophthlate are also useful
for forming the polyester-ionomers. Cations including alkali metal,
ammonium, and phosphonium cations have been shown to exhibit the
desired properties.
[0058] Comparative Polymer D:
[0059] Poly [2,2'-oxydiethylene-co-ethylene (78/22)
5-sodiosulfoisophthalate-co-isophthalate (12/88)]is commercially
available as AQ38S polymer from Eastman Chemical Company,
Kingsport, Tenn. This material was tested as received and was also
prepared as follows:
[0060] A mixture of 170.2 g (0.88 mole) of dimethylisophthalate,
35.5 g (0.12 moles) of dimethyl-5-sodiosulfoisophthalate, 19.1 g
(0.031 mole) ethylene glycol and 86.2 g (0.78 mole) of
2,2'-oxydiethanol contained in a polymerization flask equipped with
a Claisen head and a nitrogen inlet tube was heated to 200.degree.
C. under a nitrogen atmosphere to produce a clear, homogenous melt.
Then 100 ppm of titanium isopropoxide catalyst were added, and the
temperature slowly raised to 260.degree. C. over several hours.
Heating was continued until no further evolution of methanol could
be detected. A mechanical stirrer was then introduced, and the
flask connected to a source of vacuum. The mixture was stirred
under vacuum at 260.degree. C. for about two hours, then cooled to
room temperature. The resulting Comparative Polymer D had an
inherent viscosity of 0.68 dl/g, a glass transition temperature of
40.degree. C, and a weight average molecular weight of 58,000.
[0061] Polymer E-1:
[0062] Poly
[2,2'-oxydiethylene-co-1,4,5,8-naphthalenetetracarbonyl-bisimi-
do-5-pentamethylene (75/25)
isophthalate-co-5-sodiosulfoisophthalate (80/20)].
[0063] A mixture of 155.2 g (0.80 mole of dimethylisophthalate,
57.2 g (0.20 mole) of dimethyl-5-sodiosulfoisophthalate, 109.2 g
(0.25 mole) of
1,4,5,8-naphthalenetetracarbonyl-bis(5-hydroxypentyl)imide, and
111.3 g (1.05 mole) of 2,2'-oxydiethanol contained in a
polymerization flask equipped with a Claisen head and a nitrogen
inlet tube was heated to 200.degree. C. under a nitrogen atmosphere
to produce a transparent, burgundy, homogenous melt. The
polycondensation step was the same as that employed for Comparative
Polymer D. The resulting polymer E-1 has an inherent viscosity of
0.58 dl/g, a glass transition temperature of 72.degree. C., and a
weight average molecular weight of 64,0000.
[0064] Polymer E-2:
[0065]
Poly[2,2'-oxydiethylene-co-1,4,5,8-naphthalenetetracarbonyl-bisimid-
o-5-petamethylene (75/25) isophthalate-co-5-sodioisophthalate
(60/40).
[0066] The procedure was the same as for polymer El except that the
diesters consisted of 116.4 g (0.60 moles) of dimethylisophthalate
and 118.4 g (0.400 moles) of dimethyl-5-sodiosulfoisophthalate. The
polycondensation reaction was carried out in the same manner and
the resulting polymer had an inherent viscosity of 0.24 dl/g, a
glass transition temperature of 92.degree. C., and a weight average
molecular weight of 16,500.
[0067] Polymer E-3:
[0068]
Poly[2,2'-oxydiethylene-co-1,4,5,8-naphthalenetetracarbonyl-bisimid-
o-5-petamethylene (75/25) isophthalate-co-5-sodioisophthalate
(50/50).
[0069] The procedure was the same as for polymer El except that the
diesters consisted of 97.0 g (0.50 moles) of dimethylisophthalate
and 148 g (0.50 moles) of dimethyl-5-sodiosulfoisophthalate. The
polycondensation reaction was carried out in the same manner and
the resulting polymer had an inherent viscosity of 0.12 dl/g, a
glass transition temperature of 92, and a weight average molecular
weight of 12,500.
[0070] Polymer F:
[0071] Poly
[2,2'-oxydiethylene-co-1,4,5,8-naphthalenetetracarbonyl-bisimi-
do-2-ethoxyethylene (80/20)
isophthalate-co-5-sodiosulfoisophthalate (80/20)].
[0072] The procedure was the same as for polymer E-1 except that
the glycol mixture consisted of 88.4 g (0.20 mole) of
1,4,5,8-naphthalenetetr- acarbonyl-bis(2-hydroxyethoxyethyl)imide
and 118.7 g (1.12 mole) of 2.2'-oxydiethanol. The resulting polymer
F had an inherent viscosity of 0.55 dl/g, a glass transition
temperature of 68.degree. C., and a weight average molecular weight
of 65,000.
[0073] Polymer G:
[0074] Poly
[1,4,5,8-naphthalenetetracarbonyl-bisimido-2-ethoxyethylene-co
-2,2'-oxydiethylene (60/40) isophthalate-co-sodiosulfoisophthalate
(80/20)].
[0075] The procedure was the same as for polymer E-1 except that
the glycol mixture consisted of 265.2 g (0.60 moles) of
1,4,5,8-naphthalenetetracarbonyl-bis(2-hydroxyethoxyethyl)imide and
59.4 g (0.56 moles of 2,2'-oxydiethanol. The resulting polymer G
had an inherent viscosity of 0.58 dl/g, a glass transition
temperature of 82.degree. C., and a weight average molecular weight
of 61,000.
[0076] Polymer H:
[0077] Poly
[1,4,5,8-naphthalenetetracarbonyl-bisimido-2-ethoxyethylene-co
-2,2'-oxydiethylene (80/20)
isophthalate-co-5-sodiosulfoisophthalate (80/20)].
[0078] The procedure was the same as for polymer E-1 except that
the glycol mixture consisted of 353.6 g (0.80 mole) of
1,4,5,8-naphthalenetetracarbonyl-bis(2-hydroxyethoxyethyl)imide and
29.7 g (0.28 mole) of 2,2'-oxydiethanol. The resulting polymer H
had an inherent viscosity of 0.54 dl/g, a glass transition
temperature of 92.degree. C., and a weight average molecular weight
of 56,000.
[0079] Polymer I:
[0080]
Poly[1,4,5,8-naphthalenetetracarbonyl-bis2-ethoxyethylene-co-2,2'-o-
xydiethylene (40/60) isophthalate-co-5-sodiosulfoisophthalate
(80/20)].
[0081] The procedure were the same as for polymer E-1 except that
the glycol mixture consisted of 89.1 g (0.84 mole) of
2,2'-oxydiethanol and 176.8 g (0.40 mole) of
1,4,5,8-naphthalenetetracarbonyl bis(2-ethoxyethanol)imide. The
resulting polymer I had an inherent viscosity of 0.58 dl/g, a glass
transition temperature of 79.degree. C., and a weight average
molecular weight of 105,000.
[0082] The polyesterionomer-co-imide examples described above and
their responses to changes in relative humidity are listed in Table
II.
2TABLE II POLYESTERIONOMER-CO-IMIDES 18 % Water Loss From 70 F/60%
RH To Polymer x .sup.1-x y .sup.1 -(y+z) z R R' R" 80 F/20% RH
Compar ative 0.11 0.89 0 0.78 0.22 19 20 E-1 0.20 0.80 0.25 0 0.75
21 22 0.061 E-2 0.40 0.60 0.25 0 0.75 23 24 E-3 0.50 0.50 0.25 0
0.75 25 26 0.698 F 0.20 0.80 0.20 0 0.80 27 28 0.179 G 0.20 0.80
0.60 0 0.40 29 30 0.295 H 0.20 0.80 0.80 0 0.20 31 32 0.656 I 0.20
0.80 0.40 0 0.60 33 34
POLYAMIDE-CO-IMIDE EXAMPLES
[0083] The novel polyamide-co-imides of the invention were also
prepared by known techniques of melt phase polycondensation, as
described by Sorenson et al, cited above, pp. 62-64.
[0084] The control of reaction stoichiometry is required in order
to achieve both high conversion and molecular weight. The examples
of the invention were prepared by melt phase polycondensation from
either combinations of the appropriate diacids and diamines or the
salts of these diacids and diamines.
[0085] Comparative Polymer J:
[0086] This comparative polymer is a commercially available
aliphatic polyamide sold under the trade name "Amilan CM8000" by
Toray Co., Ltd. of Japan. This polymer is identified in U.S. Pat.
No. 5,876,889, which is incorporated herein by reference, as
6/66/610/12 copolymerized nylon. Identification of the monomers
which form the 6/66/610/12 copolymer are: 35
[0087] Comparative Polymer K: Poly[dodecamethylene-co-piperazino
(50/50) 1,1,3-trimethylphenylindane-co-dodecamethylene
(50/50)]amide.
[0088] A mixture of 162 g (0.50 mole) of
1,1,3-trimethyl-3-(4-carboxypheny- l)-5-indancarboxylic acid,
115.15 g (0/.50 mole) of dodecanedioic acid, 43 g (0.50 mole) of
piperazine, and 100 g (0.50 mole) of dodecanediamine were combined
in a polymerization flask equipped with side arm and gas inlet
tube. The contents were heated to 220.degree. C. under a positive
argon atmosphere to achieve a clear, homogenous melt. The
polymerization temperature was raised from 220.degree. C. to
280.degree. C. over a period of four hours or until the evolution
of distillate terminated. The flask was then equipped with a
stirrer and connected to a source of vacuum. The resulting product
was collected as a tough, amorphous solid which had a glass
transition temperature of 89.degree. C. and a weight average
molecular weight of 105,000.
[0089] Polymer L:
[0090] Poly[1,3,3-trimethylcyclohexylmethylene
1,4,5,8-naphthalenetetracar-
bonyl-bis(imido-3-propylene)-co-dodecamethylene (20/80)]amide.
[0091] A mixture of 184.2 g (0.80 moles) dodecandioic acid, 126.8 g
(0.20 moles) of 1,4,5,8-naphthalenetetracarbonyl-bis(11 -undecanoic
acid)imide, and 170.3 g (1.00 moles)
5-amino-1,3,3-trimethylcyclohexanemethylamine contained in a
polymerization flask equipped with a Claisen head and a nitrogen
inlet tube was heated to 220.degree. C. under a nitrogen atmosphere
to produce a dark burgundy, homogeneous melt. The temperature was
slowly raised to 280.degree. C. over several hours. Heating was
continued until no further distillate was observed. A mechanical
stirrer was introduced, and the flask was connected to a source of
vacuum. The mixture was stirred under vacuum at 280.degree. C. for
about two hours, or until the desired melt viscosity was achieved,
then the product was allowed to cool to room temperature. The
resulting polymer L was soluble in mixed solvents such as
dichloromethane-methanol, and had a glass transition temperature of
102.degree. C. and a weight average molecular weight of 80,000.
[0092] Polymer M:
[0093] Poly[dodecamethylene-co-1,4-piperazino (35/65)
1,4,5,8-napthalenetetracarbonyl-bis(imido-3-propylene)-co-dodecamethylene
(90/10)]amide.
[0094] A mixture of 205.7 g (0.65 moles) dipiperazonium
dodecanedioate, 107.6 g (0.25 moles), hexamethylenediammonium
dodecanedioate, and 63.8 g (0.10 moles) hexamethylenediammonium
1,4,5,8-naphthalenetetracarbonyl-bis- imido-3-propionate was
combined as per example polymer L and subjected to the same
polycondensation procedure. The resulting polymer M had solubility
in mixed solvents, a crystalline melting point of 114.degree. C.
and a weight average molecular weight of 72,500.
[0095] Polymer N:
[0096]
Poly[1,3,3-trimethylcyclohexane-1,5-methylene-1,4,5,8-naphthalenete-
tracarbonyl-bis(imido-11-undecamethylene)]amide.
[0097] A mixture of 634 g (1.00 moles)
1,4,5,8-naphthalenetetracarbonyl-bi- s(l 1-undecanoic acid)imide
and 170.3 g (1.00 moles)
5-amino-1,3,3-timethylcyclohexanemethylamine was combined as per
polymer example L and subjected to the same polycondensation
procedure. The resulting polymer N exhibited solubility in
dichloromethane-methanol, a crystalline melting point of
172.degree. C. and a weight average molecular weight of
105,000.
[0098] Polymer O:
[0099] Poly[1,3,3-trimethylcyclohexane-1,5-methylene
dodecamethylene-co-1,4,5,8-naphthalenetetracarbonyl-bis(imido-11-undecame-
thylene) (90/10)]amide.
[0100] A mixture of 200.3 g (1.00 moles)
1,3,3-trimethylcyclohexanemethyld- iammonium dodecandioate and
304.2 g (1.00 moles) 1,3,3-trimethylcyclohexan- emethyldiammonium
1,4,5,8-naphthalenetetracarbonyl-bisimido-3-propionate was combined
as per polymer example L and subjected to the same polycondensation
procedure. The resulting polymer O exhibited solubility in a
mixture of dichloromethane-methanol and had a glass transition
temperature of 152.degree. C. and a weight average molecular weight
of 25,000.
[0101] Polymer P:
[0102] Poly[1,3,3-trimethylcycylohexane-1,5-methylene
1,4,5,8-naphthalenetetracarbonyl-bis(imido-11-undecamethylene)amide-co-do-
decamethylene (60/40)]amide.
[0103] A mixture of 80.1 g (0.20 moles)
1,3,3-trimethylcyclohexanemethyldi- ammonium dodecanedioate, 253.5
g (0.40 moles), and 68.1 g (0.40 moles)
5-amino-1,3,3-trimethylcyclohexanemethyamine was combined as per
polymer example L and subjected to the same polycondensation
procedure. The resulting polymer P exhibited solubility in a
mixture of dichloromethane-methanol, had a glass transition
temperature of 113.degree. C. and a weight average molecular weight
of 141,000.
[0104] Polymer Q:
[0105] Poly[decamethylene-co-piperazino (70/30)
decamethylene-co-1,1,3-tri-
methyl-3(4-phenylindanyl-co-1,4,5,8-naphthalenetetracarbonyl-bisimidopropy-
lene (50/30/20)]amide.
[0106] A mixture of 115.15 g (0.50 moles) of docecanedioic acid,
96.2 g (0.30 moles) of
1,1,3-trimethyl-3-(4-carboxyphenyl)-5-indancarboxylic acid, 87.6 g
(0.20 moles) of 1,4,5,8-napthalenetetracarbonyl-bis(3-carbox-
ypropyl)imide, 47.6 g (0.70 moles) of 1,4-piperazine, and 69.1 g
(0.30 moles of dodecane diamine was combined in a polymerization
flask equipped with side arm and gas inlet tube, heated to
200.degree. C. to achieve a homogeneous, optically transparent,
dark burgundy melt. The temperature was raised from 220.degree. C.
to 280.degree. C. and maintained until no further distillate was
detected. The flask was then equipped with a stirrer, fitted to a
vacuum source, and polymerized to moderate-high melt viscosity. The
resulting product had a glass transition temperature of 90.degree.
C. and a weight average molecular weight of 81,000.
[0107] Polyamide-co-imide examples of the invention and comparative
polymers are shown in Table III with their respective responses to
changes in relative humidity.
[0108] In the novel polyamide-co-imide of the invention as depicted
by formula in Table III, Ar.sup.1 represents a tetravalent aromatic
group of 6 to 20 carbon atoms, R and R' independently represent
alkylene or alkylenoxy groups of 2 to 12 carbon atoms, R" and R'"
independently represent alkylene groups of 2 to 12 carbon atoms, x
is a mole fraction from 0.05 to 1, y is a mole fraction from 0 to
0.95 and z is a mole fraction from 0 to 0.95.
3TABLE III POLYAMIDE-CO-IMIDES 36 1- % Water Loss From Polymer x z
(x + z) y 1 - y R R' R" R"' 70 F/60% RH to 80 F/20% RH Comparative
0 1.276 Polymer J Comparative 0 0.50 0.50 0.50 0.50 37 38 39
Polymer K L 0.20 0.80 1.00 0 40 41 42 0.172 M 0.10 0.90 0.35 0.65
43 44 45 0.207 N 1.00 0 1.00 0 46 47 0.236 O 0.10 0.90 1.00 0 48 49
50 0.244 P 0.40 0.60 1.00 0 51 52 53 0.656 Q 0.20 0.50 0.30 0.70
0.30 54 55 56 57
[0109] Tables I, II and III show that the percent water loss for
the polymers employed in the photoconductive elements of the
invention was much smaller than the water loss for the comparative
polymers which contained no planar, electron-deficient aromatic
tetracarbonylbisimide group and which absorbed and lost relatively
large amounts of water with humidity changes. As a result, the
comparative polymers are susceptible to substantial variation in
conductivity when employed in a barrier layer.
[0110] The examples which follow describe the preparation and
testing of photoconductive elements of the invention and of
comparative photoconductive elements. They are referred to,
respectively, as "examples" and as "comparative examples."
COMPARATIVE EXAMPLE 1
[0111] A multiactive photoconductive film comprising a conductive
support, a barrier layer, a charge generation layer (CGL), and a
charge transport (CTL), coated in that order, was prepared from the
following compositions and conditions.
[0112] Coated on nickelized poly (ethylene) terephthalate, at dry
coverage of 0.05 g/ft.sup.2 was a barrier layer of Amilan CM8000
polyamide having no planar tetracarbonylbisimide repeating unit.
The barrier layer was prepared at 2.5 wt % in a 65/35 (wt/wt)
mixture of ethanol and dichloromethane. A coating surfactant,
SF1023, was added at a concentration of 0.003 wt % of the total
solution.
[0113] A second layer (CGL) was coated on the barrier layer at a
dry coverage of 0.05 g/ft.sup.2. The CGL mixture comprised 50% of a
75/25 cocrystalline pigment mixture of titanyl phthalocyanine and
tetrafluoro titanyl phthalocyanine, prepared as described in
Molaire et al U.S. Pat. No. 5,614,342 and 50% of a polyester
ionomer binder, poly [2,2-dimethyl-1,3-propylene-co-oxydiethylene
(80/20) isophthalate-co-5-sodiosulfoisophthalate (95/5)] prepared
as described in Molaire et al. U.S. Pat. No. 5,733,695. The CGL
mixture was prepared at 3 wt % in a 65/35 (wt/wt) mixture of
dichloromethane and 1,1,2-trichloroethane, as described in U.S.
Pat. No. 5,614,342. A leveling agent, DC510 was added at a
concentration of 0.019 wt %.
[0114] A third layer (CTL) was coated onto the CGL at a dry
coverage of 2.3 g/ft.sup.2. The CTL mixture comprised 50-wt %
Makrolon 5705, 10% poly [4,4'-(norbomylidene) bisphenol
terephthalate-co-azelate (60/40)], 20 wt % of
1,1-bis[4-(di-4-tolylamino)phenyl] cyclohexane, 20 wt %
tri-(4-tolyl)amine. The CTL mixture was prepared at 10 wt % in
dichloromethane. A coating surfactant, DC510, was added at a
concentration of 0.016 wt % of the total mixture.
COMPARATIVE EXAMPLE 2
[0115] The photoconductive element was prepared as described in
Comparative Example 1, except that the barrier layer polymer was
AQ38S polyesterionomer, having no planar tetracarbonylbisimide
moiety, sold by Eastman Chemical Company. The barrier layer
solution was prepared at 5 wt % deionized water. A coating
surfactant, Olin 10 G was added at a concentration of 0.07 wt % of
the total solution. The barrier layer was coated at a dry coverage
of 0.05 g/ft.sup.2.
EXAMPLE 1
[0116] The photoconductor was prepared as described in Comparative
Example 1, except that the barrier layer polymer was
polyesterionomer-co-imide E-1 of Table II. The barrier layer
solution was prepared at 2 wt % in deionized water. A coating
surfactant, Olin 10 G, was added at a concentration of 0.45 wt % of
the total solution. The barrier layer was coated at a dry coverage
of 0.05 g/ft.sup.2.
EXAMPLE 2
[0117] The photoconductor was prepared as described in Comparative
Example 1, except that the barrier layer polymer was
polyesterionomer-co-imide I of Table II. The barrier layer solution
was prepared at 2 wt % in deionized water. A coating surfactant,
Olin 10 G, was added at a concentration of 0.45 wt % of the total
solution. The barrier layer was coated at a dry coverage of 0.05
g/ft.sup.2.
EXAMPLE 3
[0118] The photoconductor was prepared as described in Comparative
Example 1, except that the barrier layer polymer was
polyesterionomer-co-imide G of Table II. The barrier layer solution
was prepared at 2 wt % in deionized water. A coating surfactant,
Olin 10 G, was added at a concentration of 0.45 wt % of the total
solution. The barrier layer was coated at a dry coverage of 0.05
g/ft.sup.2.
EXAMPLE 4
[0119] The photoconductor was prepared as described in Comparative
Example 1, except that the barrier layer polymer was
polyesterionomer-co-imide F of Table II. The barrier layer solution
was prepared at 2 wt % in deionized water. A coating surfactant,
Olin 10 G, was added at a concentration of 0.45 wt % of the total
solution. The barrier layer was coated at a dry coverage of 0.05
g/ft.sup.2.
[0120] Although the described condensation polymers having aromatic
tetracarboxylbisimide groups are valuable when used as the sole
polymer of the barrier layer provide, as demonstrated by the
examples herein, the invention also includes barrier layers
comprising a blend of such polymers with other polymers such as the
Amilan CM8000 aliphatic copolyamide previously described herein.
The following examples 5, 6 and 7 describe such compositions. Their
useful properties are illustrated by the results recorded in Table
IV hereinafter.
EXAMPLE 5
[0121] The photoconductor was prepared as described in Comparative
Example 1, except that the barrier layer was a 75/25 wt/wt mixture
of Amilan CM8000 aliphatic polyamide and the
polyesterionomer-co-imide F of Table II. The barrier layer solution
was prepared at 2 wt % in a methanol/water mixture. A coating
surfactant, Olin 10 G, was added at a concentration of 0.45 wt % of
the total solution. The barrier layer was coated at a dry coverage
of 0.05 g/ft.sup.2.
EXAMPLE 6
[0122] The photoconductor was prepared as described in Example 5,
except that the barrier layer was a 75/25 wt/wt mixture of Amilan
CM8000 aliphatic polyamide and the polyesterionomer-co-imide E of
Table II.
EXAMPLE 7
[0123] The photoconductor was prepared as described in Example 5,
except that the barrier layer was a 50/50 wt/wt mixture of Amilan
CM8000 aliphatic polyamide and the polyesterionomer-co-imide E of
Table II.
Evaluation
[0124] The films were tested in a laboratory apparatus that
charges, exposes and erases the film continuously. The residual or
"toe" voltage after 2000 cycles was recorded for each film. The
results of Table IV show that the examples of the invention
outperform the comparative examples.
4 TABLE IV Absolute Residual Potential after 2,000 cycles
25.degree. C. 25.degree. C. Example Barrier Polymer 50% RH 20% RH
Comp Amilan CM8000 46 V 108 V Example 1 Comp AQ38S 167 V Example 2
Example 1 Polymer E 47 V 33 V Example 2 Polymer I 44 V 28 V Example
3 Polymer G 50 V 33 V Example 4 Polymer F 43 V 40 V Example 5
Amilan CM8000/Polymer F 75/25 74 V 80 V Example 6 Amilan
CM8000/Polymer E 50/50 62 V 65 V Example 7 Amilan CM8000/Polymer E
75/25 56 V 66 V
Evaluation of Regeneration Stability
[0125] It is essential for an electrophotographic or
photoconductive element that is cycled many times in the
electrophotographic process to maintain stable residual voltages
close to zero during use. Longer regeneration cycles were run for
comparative example 1 and invention examples 1, 6 and 7. The
machine was stopped after every 2000 cycles for one hour and
started again until 10,000 cycles were reached. The results are
shown in FIGS. 2, 3, 4 and 5 of the drawing. These figures are
plots of the negative surface potential, in volts, for the
indicated photoconductive elements for V.sub.0, i.e., the voltage
after charging and before exposure and for the "toe voltage" which
is the residual voltage on the photoconductive surface after full
exposure. As shown in FIG. 2, for comparative example 1, the toe
voltage rose substantially at 2000 cycles but dropped back to the
original value after the one-hour rest, only to climb back up again
in the next 2000 cycles burst. FIGS. 3, 4 and 5 show that the
examples of the invention, i.e., examples 1,6, and 7, are more
stable.
Evaluation of Electroformed Nickel Substrate
COMPARATIVE EXAMPLE 3
[0126] A multiactive photoconductive element comprising an endless
conductive nickel sleeve 180 mm diameter, 5 mil thick and 395 mm
long, manufactured by Stork Rotaform, a barrier layer, a charge
generation layer (CGL), and a charge transport (CTL), coated in
that order, was prepared as follows:
[0127] Coated on the endless seamless nickel sleeve using the dip
coating process, at dry coverage of 0.15 g/ft.sup.2 was a barrier
layer of Amilan CM8000 polyamide. The barrier layer was prepared at
3.5 wt % in a 65/35 (wt/wt) mixture of ethanol and dichloromethane.
A coating surfactant, SF1023, was added at a concentration of 0.003
wt % of the total solution.
[0128] A second layer (CGL) was coated on the barrier layer at a
dry coverage of 0.05 g/ft.sup.2. The CGL mixture comprised 50% of a
90/10 cocrystalline pigment mixture of titanyl pthalocyanine and
tetrafluoro titanyl phthalocyanine, prepared as described in
Molaire et al U.S. Pat. No. 5,614,342 and 50% of a polyester
ionomer binder, poly [2,2-dimethyl-1,3-propylene-co-oxydiethylene
(80/20) isophthalate-co-5-sodiosulfoisophthalate (95/5)] (prepared
as described in Molaire et al., U.S. Pat. No. 5,733,695. The CGL
mixture was prepared at 3 wt % in a 65/35 (wt/wt) mixture of
dichloromethane and 1,1,2-trichloroethane, as described in U.S.
Pat. No. 5,614,342. A leveling agent, DC510 was added at a
concentration of 0.019 wt %.
[0129] A third layer (CTL) was coated onto the CGL at a dry
coverage of 2.3 g/ft.sup.2. The CTL mixture comprised 30 wt %
Makrolon 5705 polymer, 20% Lexan polymer, 10% poly
[4,4'-(norbomylidene-bisphenol terephthalate-co-azelate (60/40)],
20 wt % of 1,1-bis [4-(di-4-tolylamino)phenyl] cyclohexane, 20 wt %
tri-(4-tolyl)amine. The CTL mixture was prepared at 10 wt % in
dichloromethane. A coating surfactant, DC510, was added at a
concentration of 0.016 wt % of the total mixture.
EXAMPLE 8
[0130] A photoconductive element of the invention was prepared as
described in Comparative Example 3, except that the barrier layer
was the polyesterionomer-co-imide G of Table II. The barrier layer
solution was prepared at 3.5 wt % in a 65/35 (wt/wt) mixture of
ethanol and deionized water. A coating surfactant, Olin 10 G, was
added at a concentration of 0.45 wt % of the total solution. The
barrier layer was coated at a dry coverage of 0.12 g/ft.sup.2. The
CGL was coated out of 100% tetrahydrofuran as a solvent.
[0131] Comparative Example 3 and invention Example 8 were evaluated
in an experimental high speed coating machine. The residual or toe
voltage for each cylinder was measured initially and after 1000
cycles. The results are shown in Table V. The barrier layer of the
invention shows markedly more stable performance at 25% RH than the
comparative example.
5TABLE V Vexposed Vexposed @ @ 25% RH 25% RH 1000 Example Barrier
Polymer Initial cycles Delta Comp Example 3 Amilan CM8000 on Nickel
sleeve 160 V 238 V +78 V Example 8 Polymer G on Nickel sleeve 181.6
V 185.6 V +4V
[0132] The following comparative example 4 and invention examples
9, 10, 11 and 12 demonstrate the effect of barrier layer thickness
on the regeneration of photoconductive films.
COMPARATIVE EXAMPLE 4
[0133] The photoconductor was prepared as described in Comparative
Example 1, except that the charge generation layer was coated at
0.10 g/ft.sup.2.
EXAMPLE 9
[0134] The photoconductor was prepared as described in Comparative
Example 4, except that the barrier layer polymer was
polyesterionomer-co-imide E-2 of Table II. The barrier layer
solution was prepared at 2 wt % in deionized water. A coating
surfactant, Olin 10 G, was added at a concentration of 0.45 wt % of
the total solution. The barrier was coated at a dry coverage of 0.1
g/ft.sup.2.
EXAMPLE 10
[0135] The photoconductor was prepared as described in Comparative
Example 4, except that the barrier layer polymer was
polyesterionomer-co-imide E-2 of Table II. The barrier layer
solution was prepared at 2 wt % in deionized water. A coating
surfactant, Olin 10 G, was added at a concentration of 0.45 wt % of
the total solution. The barrier was coated at a dry coverage of 0.2
g/ft.sup.2.
EXAMPLE 11
[0136] The photoconductor was prepared as described in Comparative
Example 4, except that the barrier layer polymer was
polyesterionomer-co-imide E-3 of Table II. The barrier layer
solution was prepared at 2 wt % in deionized water. A coating
surfactant, Olin 10 G, was added at a concentration of 0.45 wt % of
the total solution. The barrier was coated at a dry coverage of 0.5
g/ft.sup.2.
EXAMPLE 12
[0137] The photoconductor was prepared as described in Comparative
Example 4, except that the barrier layer polymer was
polyesterionomer-co-imide E-3 of Table II. The barrier layer
solution was prepared at 2 wt % in deionized water. A coating
surfactant, Olin 10 G, was added at a concentration of 0.45 wt % of
the total solution. The barrier was coated at a dry coverage of 0.2
g/ft.sup.2.
Evaluation
[0138] The photoconductor films were tested in an apparatus that
charges, exposes and erases the film continuously. The residual
voltage after 1000 cycles (toe @ 20%RH) was recorded for each film.
The results show that the examples of the invention, even with
substantially thicker barrier layers, outperform the comparative
example by exhibiting lower differences between the initial toe
voltage and the voltage after 1000 cycles, as recorded in the
"Delta" column of Table VI.
6TABLE VI V.sub.toe @ V.sub.toe @ Thick- 25.degree. C./ 25.degree.
C./ Barrier ness 20% RH 20% RH Example Polymer g/ft.sup.2 Initial
1000 cycles Delta Comparative CM8000 0.05 -9 -75 66 Example 4
Amilan Example 9 Polymer E-2 0.05 -11 -21 10 Example 10 Polymer E-2
0.2 -50 -78 28 Example 11 Polymer E-3 0.05 -13 -19 6 Example 12
Polymer E-3 0.2 -31 -38 7
COMPARATIVE EXAMPLE 4A
[0139] The photoconductor was prepared as described in Comparative
Example 1, except that the barrier layer polymer was Amilan CM8000
polyamide. The barrier layer was prepared at 2.5 wt % in a 65/35
(wt/wt) mixture of ethanol and dichloromethane. A coating
surfactant, SF1023, was added at a concentration of 0.003 wt % of
the total solution. The barrier layer was coated at a dry coverage
of 0.10 g/ft.sup.2.
COMPARATIVE EXAMPLE 5
[0140] The photoconductor was prepared as described in Comparative
Example 1, except that the barrier layer polymer was comparative
polyamide K of Table III. The barrier layer was prepared at 2.5 wt
% in a 65/35 (wt/wt) mixture of ethanol and dichloromethane. A
coating surfactant, SF1023, was added at a concentration of 0.003
wt % of the total solution. The barrier layer was coated at a dry
coverage of 0.10 g/ft.sup.2.
EXAMPLE 13
[0141] A photoconductive element of the invention was prepared as
described in Comparative Example 1, except that the barrier layer
polymer was polyamide-co-imide Q of Table III. The barrier layer
was prepared at 2.5 wt % in a 65/35 (wt/wt) mixture of ethanol and
dichloromethane. A coating surfactant, SF1023, was added at a
concentration of 0.003 wt % of the total solution. The barrier
layer was coated at a dry coverage of 0.10 g/ft.sup.2. The
evaluation results are shown in Table VII.
7TABLE VII V.sub.toe @ V.sub.toe @ 20% RH 20% RH Example Barrier
Polymer Initial 1000 cycles Delta Comp Ex- CM8000 Amilan -22 V -110
V +88 V ample 4A Comp Example 5 Polymer K -153 V -243 V +90 V
Example 13 Polymer Q -41 V -60 V +19 V
Black Spots Evaluation
[0142] As disclosed in Bugner et al, U.S. Pat. No. 5,681,677,
incorporated herein by reference, in a Discharged Area Development
(DAD) system, such as a high speed laser or LED printer, black spot
formation can occur with certain photoconductive elements. The
choice of barrier layer and barrier layer thickness is critical to
minimize and eliminate the formation of black spots. The following
examples which demonstrate the good performance of photoconductive
elements of the invention, were coated using a 30 mm drum format
compatible with the Hewlett Packard LaserJet 5Si commercial laser
printer.
COMPARATIVE EXAMPLE 6
[0143] The methods and compositions of Comparative Example 3 were
used to coat a 30 mm drum that is compatible with the HP LaserJet
5Si laser printer, except that no barrier layer was used. The CGL
layer was coated over the bare aluminum substrate.
COMPARATIVE EXAMPLE 7
[0144] The same procedure and materials of Comparative Example 6
were used, except that Amilan CM8000 polymer was used as a barrier
layer and coated at thickness of 0.1, 0.3, 0.8, and 1.7 microns
EXAMPLE 14
[0145] A photoconductive element of the invention was prepared in a
manner similar to Comparative Example 7, except that
polyamide-co-imide L of Table III was used as the barrier layer. It
was coated at thickness of 0.2, 0.8, and 1.2 microns.
EXAMPLE 15
[0146] A photoconductive element of the invention was prepared in a
manner similar to Comparative Example 7, except that
polyesterionomer-co-imide E-2 of Table II was used as the barrier
layer. It was coated at thickness of 0.2, 0.8 and 1.2 microns.
[0147] To evaluate "black spot" formation susceptibility of these
drums, the drum being evaluated replaced the original drum of an
HP5Si cartridge. A "white page" was generated using the LaserJet
5Si laser printer for each drum sample. The generated white pages
were scanned and analyzed for black spots. Correction was made for
single toner background particles. The area analyzed was kept
constant for all samples. The lower the "Black Spot Count", the
better is the barrier layer. The results are shown in Table VIII.
The effect of barrier thickness can be seen. Without any barrier
the Black Spot Count is above 15,000. It is down to 241 for a
0.8-micron layer of Amilan CM8000. Examples 14 and 15 of this
invention show good performance for similar thicknesses.
8TABLE VIII Thickness Black Example Barrier Polymer Microns Spot
Count Comp Example 6 None 15,667 Comp Example 7 Amilan CM8000 0.1
5,587 Comp Example 7 Amilan CM8000 0.3 449 Comp Example 7 Amilan
CM8000 0.8 241 Comp Example 7 Amilan CM8000 1.7 265 Example 14
Polymer L 0.2 662 Example 14 Polymer L 0.8 333 Example 14 Polymer L
1.2 294 Example 15 Polymer E-2 0.8 580 Example 15 Polymer E-2 1.1
161 Example 15 Polymer E-2 1.6 130
Effect of CGL Coating Solvent
EXAMPLES 16 AND 17
[0148] For the barrier layer to be effective, it is essential that
it keep its integrity after the next coating (CGL) is applied. In
other words the solvent of the CGL coating should not attack and
dissolve the coated barrier layer. This is even more critical in
the dip coating process, because of relatively long residence time
in the coating solution. To show the importance of this effect
Examples 12 and 13 were coated using polymer H and polymer E-1,
respectively. These polyesterionomer-co-imides H and E-1 are
slightly soluble and or swellable by chlorinated solvent such as
dichloromethane (DCM) and 1,1,2-trichloroethane (TCE). However,
they are completely immune to attack by tetrahydrofliran (THF).
These two barrier polymers were employed with CGLs coated
respectively with a DCM/TCE and a THF solution in a process similar
to Comparative Example 3. The Black Spot Count comparison for the
two conditions is shown in Table IX. The THF CGL versions performed
substantially better than the DCM/TCE. This demonstrates the
importance of protecting the barrier layer from damage by the
solvent of the CGL.
9TABLE IX Black Black Barrier Thickness Spot Count Spot Count
Example Polymer Microns DCM CGL THF CGL Example 16 Polymer H 0.7
1743 430 Example 17 Polymer E 2.5 1205 374
[0149] The invention has been described with particular reference
to preferred embodiments thereof, but it will be understood that
variations and modifications can be effected by a person of
ordinary skill in the art within the spirit and scope of the
invention.
* * * * *