Note: Descriptions are shown in the official language in which they were submitted.
~25at777
OVERCOATED PHOTORESPONSIVE DEVICES
c
BAÇKGROUND OF THE INVENTION
This invention is generally directed to layered photoresponsive
devices, and more specifically, the present invention is directecl to an
improved overcoated layered photoresponsive device which is capabie
of bein~ responsive to visible light, and~or infrared illumination
needed for laser printing. The layered photoresponsive devices of the
present invention contain a protective overcoating material. This
LS material also simultaneously functions as an ultraviolet light absorbing
layer thereby preventing the degradation of certain substances
contained in the other layers of the device and adversely affected by
ultraviolet light. In one important embocliment o~ the present
20 invention, there is provided an overcoated layered photoresponsive
imaging device, which is responsive to visible light, and infrared
illumination, this device being comprised of a substrate, a hole
transport layer, a photogenerating layer, and an overcoating layer
comprised of materials that function as an ultraviolet light absorbant
2s substance, while simultaneously functioning as a visible light
photogeneration layer, and as a physical protectant layer for the other
layers contained in the device.
. .
Photoresponsive devices, including layered photoresponsive
devices containing charge transport layers, and charge generating
layers of selenium, selenium alloys, phthalocyanines, and the like are
known. Also, photoreceptor materials comprised of inorganic or
organic compositions wherein the charge carrier generation and
35 charge carrier transport functions are accomplished by discrete
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contiguous layers are disclosed in the prior art. Additionally~
photoreceptor rnaterials are disclosed in the prior art which include an
overcoating layer of an eiectrically insulating polymeric material, and
in conjunction with this overcoated type photorecep~or, there have
been proposed a nurnber of irnagin3 methods.
Recently, there has been disclosed layered photoresponsive
devices comprised of generating layers and transport layers, reference
lO U.S. Patent 4,26~,990, and overcoated photoresponsive rnaterials
containing a hole injectin~ layer, overcoated with a charge transport
layer, foliowed by an overcoating of a photogenerating layer, and a top
coating of an insulating organic resin, reference U.S~ Patent
4,251,612. Examples of photogenerating compositions disclosed in
these patents include trigonal selenium, various phthalocyan;nes, and
the like, while examples of charge transport layers include those
compr~lsed of diamines. Additionally, there is disclosed in U.S. Patent
3,041,116 a photoconductive material containing a transparent plastic
20 material overcoated on a layer of vitreous selenium which is contained
on a recording substrate. Apparently in operation, the surface of the
transparent plastic is electrostatically charged to a desired polarity,
followed by exposing the device to activating radiation, which
generates a hole electron pair in the photoconductive layer, causing
electrons to move to the plastic layer and neutralize the positive
charges contained on the free surface of the plastic layer, thus
creating an elec~rostatic image.
In some of the prior art devices, the diamine transport molecules
contained in the transport layer can be adversely a~fected, and
degraded by ultraviolet light, and corona exposures, rendering such
devices substantially useless for obtaining continuous high quality
images. This is particularly a problem with regard to devices
containing a top photogenerating layer, which is charged positively.
3~ZSQ7~7
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Apparentiy, the diamines contained in the transport layer are
converted to a cationic radical by ultraviolet light, this radicai causing
the positive charges contained on the surface of the layered imaging
member to be undesirably eliminated. More specifically the
overcoating layer of the photoresponsive device of the present
invention is comprised of materials that will absorb damaging short
wavelength light, while transmitting the lonQer wavelengths to the
photogeneration layer. Since the damaging light radiation extends
o into the visible, that is wavelength of 450 nanometers the
photosensitivity is reduced in the blue by a purely absorptive iayer.
The photosensitivity at these blue wavelengths can however be
restored by using as an overcoat layer materials that are
photosensitive to the the short wavelengths they absorb.
Accordingly, there is a need for eliminating the degradation of such
diamine molecules. The improved layered photoresponsive device of
the present invention accomplishes this important objective.
Additionally, it is known that the application of protective coatings
to photoconductive substances, particularly inorganic
photoconductive materials, can be effected primarily for the purpose
of ex~ending the useful life of these devices. Without such
s overcoatings, deterioration of the photoconductive member occurs by,
for example, the mechanical abrasion attendent to the developing and
cleaning processes. In view of this, and for other reasons, various
. protective overcoatings have been applied to inorganic
30 photoresponsive devices. Thus for example, there is disclosed in U.S-
Patent 3,397,982 an electrostatic imaging device comprising a
photoconductive layer containing an inorganîc glass material, and a
photoconductive layer with an overcoating comprised of various
oxides, such as germanium oxides, the oxides of vanadium, and
3S silicone dioxides.
5~77~
Moreover, there is disclosed, for example in U.S. Patent 3,655,377
the use of an arsenic selenium alloy as an overcoating on a tellurium
selenium alloy photogenerator layer. Also there is described in a
copending application, photoresponsive devices c~ntaining a
- photogenerating layer, and a photoconductive layer. This prior art,
however is silent with regard to protecting the diamine transport
- molecule from damage by radiation and corona effluents.
~0 Furthermore, there is disclosed in U.S. Patent 2,886,434 processes
for protecting selenium photoconductive substances with a thin,
transparent film of a material having electrical characteristics
comparable to selenium. Examples of materials disclosed as
protective layers in this patent include zinc sulfide, silica, various
silicates, alkaline earth fluorides, and the like. Nevert~eless, thsre
continues to be a need for protective overcoatings, particularly for
layered photoresponsive devices containing charge transport layers,
and photogenerating layers, which overcoatings also function
20 simuitaneously as an ultraviolet light absorber layer for the purpose of
preventing degradation of the diamines contained in the charge
transport layer.
There also continues to be a need for improved layred
25 photoresponsive devices which not only generate acceptable images
but which can be repeatedly used in a number of imaging cycles
without deterioration thereof from the machine environment or
surrounding conditions. Additionally, there continues to be a need for
30 improved layered imaging devices, wherein the hole transporting
compositions selected for use in these devices do not degrade after
extended usage. Further, there also continues to be a nee~ for
improved photoresponsive devices which contain hole transport
layers photogenerating layers, and an overooating pro~ective layer,
35 whioh devices are sensitive to visible light and infrared illumination,
~25~7~
thereby allowing these devices to be selected for use in a number of
imaging and printing systems.
SUMMARY OF THE INVENTION
s
It is therefore an object of the present invention to provide an
improved photoresponsive member which overcomes the above~noted
disadvantages.
It is yet another object of the present invention to provide an
improved positive charging photoresponsive device which is sensitive
to visible light as well as to infrared light.
A further object of the present invention is the provision of an
improved photoresponsive device containing a hole transport layer,
and a protective overcoating layer.
It is yet a further object af the present invention to provide a
layered photoresponsive device containing a protective overcoating
which also functions as an ultraviolet light absorbing layer.
In a further object of the present invention there is provided a
2s layered photoresponsive imaging device wherein the aryldiamine
molecules that escape from the hole transport layer are prevented
from degradtion by the protective overcoating layer.
These and other objects of the present invention are accomplished
30 by the provision of an improved photoresponsive device comprising a
hole transport layer, a photogenerating layer, and a protective
overcoating layer comprised of ultraviolet light absorbing materials. In
one specific embodiment, the present invention is directed to an
3S improved photoresponsive devioe comprised in the order stated of (1)
a substrate, (2) a hole transport layer, (3) a photogenerating layer, and
~Z50~7
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(4) a protective overcoating layer comprised of ultraviolet light
absorbing materials. A further important embodiment of the present
invention resides in an improved photoresponsive devioe comprised in
the order stated of (1) a conductive substrate, (2) a hole transport
layer cornprised of certain diamines dispersed in an inactive resinous
binder composition, (3) a photogenerating layer comprised of a
photogenerating pigment optionally dispersed in a resinous binder,
and (4) a protective overcoating layer comprised of the alloys of
o selenium.
The improved photoresponsive devices of the present invention
can be prepared by a number of known methods, the process
parameters and the order of coating the layers being dependent on
the device desired. Thus, for examplel the improved photoresponsive
device of the present invention can be prepared by providing a
conductive substrate, and applying thereto by solvent coating
processes, laminating processes, solvent spraying processes, or other
~o methods, a hole transport layer, a photogenerating layer, and a
protective overcoating. More specifically, the irnproved
photoresponsive device of the present invention can be prepared by
depositing the hole transport layer and photogenerating layers by a
solvent spraying process, followed by application of the protective
overcoating layer by vacuum deposition. In this process, the hole
transport, and photogenerating layers are generally depositecl at room
temperature, while the overcoating layer is applied at higher
temperatures, with the thickness of the layers` being controlled for.
30 example by the proportions of solvent to hole transport layer or
photogenerating layer utilized, and by repeating the coating process
as appropriate. Examples of solvents that may be selected in the
solvent spraying process include methylene chloride, ethylene
chloride, and mixtures thereof.
~;~5~7~7
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The improved layered photoresponsive device of the present
invention can be selected for use in various imaging systems, and
more importantly, can function in imaging and/or printing systens
utilizing visible light and/or infrared light. Thus, the improved
photoresponsive àevices of the presen~ invention can be selected for
use in irnaging devices where the device is positively charged and
t wherein the arylamine materials selected for use in the transport layer
are not degraded by ultravioiet light. In one embodiment, the imaging
method of the present invention involves positivety charging the
photoresponsive device described herein, subjecting the device to
imagewise charging for the purpose of forming an electrostatic latent
image thereon, developing the latent image with a developer
composition comprised of toner particles and carrier particles,
followed by transferring the image to a suitable substrate such as
paper, and permanently affixing the image thereto.
In another embodiment of the present invention, the
,0 photoresponsive device can be se~ected for use in printing systemsthat is in thcse apparatuses wherein a laser, such as a gallium
arsenide laser, or image bars are is used for generating the image to
be developed.
BRIEF DESCRIPTIQN OF THE DRAWING
For a better understanding of the present invention, and further
features thereof, reference is made to the followi~g detailed
description of various preferred embodiments wherein:
Figure 1 is a partially schematic cross sectional view of the
3~; improved photoresponsive device of the present inven~ion;
5~7
. ~.
- Figure 2 is a partially schematic cross-sectional view of a preferred
photoresponsive device of the present invention; and
Figure 3 is a partially schematic cross-sectional view of a preferred
photoresponsive device of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Illustrated in Figure 1 is the improved photoresponsive device of
the present invention, generally designated 1, and comprising a
substrate 3, a hole or charge transport layer ~, containing a hole
transporting composition dispersed in an inert resinous binder 6, a
charge carrier photogenerating layer 7, containing a photogenerating
15 pigment optionally dispersed in an inert resinous binder 8, and a
protective overcoating layer 9~
The substrate layer 3 may be opaque or substantially transparent,
~0 and rnay comprise suitable materials having the appropriate
mechanical properties. Generally, the substrate is comprised of an
insulating material, such as an organic or inorganic polymeric
material, a layer of an organic or inorganic material having a semi
conductive surface layer arranged thereon, or a conductive material
'5 such as for exarnple, aluminum, chromium, nickel, indium, tin oxide,
brass, or the like. Examples of insulating layers that can be selected
as the substrate include various resinous materials, such as
polycarbonates, polyesters, and the like, however, the substrate is
30 preferabiy comprised of a material commercially available as
aluminized Mylar. The substrate may be flexible or rigid, and may
have a number of different configurations, including a plate, a
cylindrical drum, a scroll, an endless flexible belt, and $he like.
Preferably, the substrate is in the form of an endless flexible belt, or a
35 rigid cylindrical drum.
~2~7~}7
The ~hickness of the substrate layer varies depending upon many
factors, including economical considerations, thus this layer rnay be
of substantial thickness, for example, over 10 millimeter~, or of
minimum thickness, providing there are no adverse effects with the
resulting device. In one preferred embodiment, the thickness of this
layer ranges from ab~ut 3 millimeters to about 10 millimeters.
The hole transport layer 5 can be comprised of a number of
lO suitable materials which are capable of transporting holes, this layer
generally havin~ a thickness in the range of from about 5 to about 50
micrometers, and preferably this layer is of a thickness of from about
20 to about 40 micrometers. Transport layer 5 thus comprises an
arylamine electron donor dispersed in an inert resinous bind~r
material 6. Illustrative examples of electron donor molecules include
those as described in U.S. Patent 4,265,990.
Specific illustrative examples
of electron donor molecules inciude aryl amines, such as substituted
20 N,N,N',N! tetraphenyl [1,1 '-biphenyl]4,4'-diamines of the forrnula as
illustrated in the 4,265,990 -patent.
The inert highly insulating resinous binder 6, which has a
resistivity of at ieast 1012 ohm-cm to prevent undue dark decay, is a
25 material which is not necessarily capable of supportiny the inj~ction of
holes from the photogenerator layer, and is not capable of all~wing
the transport of these holes through the material. Howe~er, the resin
becomes electrically active when it contains from about ~0 to 7
30 weight percent of the substituted N,N,N',N'-tetraphenyl-~ 1,1'-
biphenyl]4,4'-diamines. Specific examples of such diaminss include,
N,N'-diphenyl-N,N'-bis(alkylphenyl)-[1 ,1 '-biphenyl]-4,4'-diamine
wherein alkyl is selected from the ~roup consisting of methyl, such as
2-methyl, 3-methyl, and 4-methyl, athyl, propyl, bu~l, hexyl, and the
3S like. With halo substitution, the amine is N,N'-diphenyl N,N'-
s*~ ~
-` ~2507~
10'
bis(halophenyl)-~1 ,1'-biphenyl]-4!4'-diamine wherein halo is 2-chloro,
3-chloro, or 4-chloro.
Othcr electrically active donor compositions which can be
dispersed in the electrically inac~ive resin to form a layer which will
transport holes include the arylamines, triphenylamine, bis-(4-
diethylamino 2-methylphenyl)phenylmethane;b;s-(4-
diethylaminophenyl)phenylmethane;t-phenyl-3-(4'-
10 diethylaminostearyl)-5-(4"-diethylaminophenyl) pyrazoline; 4-
diethylaminobenzaldehyde-1,1-diphenyl hydrazone; 2,5-bis-
(4'diethylaminophenyl)-1 ,3,i-oxadiazote; and 1 ,4-bis-[bis(4'-
(phenylmethyl)-amino 2'-m0thylphenyl)methyl] benzene.
~3 A preferred hole transport layer, in a thickness of from about 10
micrometers to about 20 micrometers, is comprised of 35 percent by
weig~t of th~ diamine N,N'-diphenyl-N,N'-bis(3-methylphenyl)1,1'-
biphenyl-4,4'-diamine, dispersed in 65 percent by weight of the
0 pr~lycarbonate resin commercially available as Makrolon.
Illustrative exarnples of insulating resinous binders 6 ~or the hole
transport layer include in addition to polycarbonate resins
commercially available as Makrolon, Merlon and Lexan, polysulfones
~; polystyrene, and the lik~. Generally, the diamine transport molecule is
dispersed in the resinous binder, in an amount rangin~ from about 25
percent by weight ~o 70 percent by weight, and preferably in an
amount of from about 30 percent by weight to about 50 percent by
3D weight.
The photogenerating layer 7 includes for example, numerous
photoconductive charge carrier generating materials providing they
are electronically compatible with the charge carrier transport layer,
3i that is, they can inject photoexeited charge carriers into the transpor~
. .
* Trademark
5~1!77~
layer and charge carriers can travel in both directions across the
interface between the two layers. Thus, the photogenerating layer 7
can be comprised of inorganic photosensitive pigments such as
trigonal s~lenium, mixtures of Groups IA and IIA elements, cadmium
selenide, cadmiun sulfur selenide, copper and chlorine doped
cadmium sulfide,and trigonal selenium doped with sodium carbonate
reference U.S. Patents 4,232,tO2 and 4,233,?83, and th~ like,
optionally dispersed in various resinous binders.
The photogenerating layer can also contain organic charge carrier
generating materials such as phthalocyanines, includin~ for example,
metal phthalocyanines, metal free phthalocyanines, vanadyl
phthalocyanines, squaraine pigments, such as methyl squarilium
pigments, hydroxy squariliurn pigments, and mixtures thereof,
optionally dispersed in resinous binders.
Other photogenerating materials not disclosed herein can be
20 selected for the photoresponsive device of the present invention
including, for example, other phthaiocyanines, such as copper
phthalocyanine, zinc phthalocyanine, magnesium phthalocyanine, the
x-form of metal free phthalocyanine, and the like.
2~ The photogenerating pigments are usually dispersed in an inactive
resinous binder, 8, illustrative examples of which include polyesters,
polycarbonates, polystyrenes, polysulfones, phenoxy resins, epoxy
resins, and the like, with polyesters being preferred. Generally, the
30 photogenerating pigment is contained in the resinous binder in ;an
amount of from about 5 percent by weight to about 80 percent by
weight, and preferably in an amount of from about 10 percent by
weight to about 40 percent by weight. Accordingly, in this
embodiment the resinous binder is present in an amount of from about
3s 95 percent by weight to about 20 percent by weight"and preferably in
~L25~P7~'7
1'
an amount of from about 90 percent by weight to about 60 percent by
weight.
The thickness of the phot~generating layer depends on a number
of factors including the thicknesses of the other layers, ~enerally,
however, this layer ranges in thickness of from about 0.01
micrometers to about 10 micrometers, and preferably is of a thickness
of from about 0.1 micrometers to about 1.0 micrometers. The
l0 maximum thickness of this layer is dependent primarily on factors
such as mechanical considerations, while the minimurn thickness of
this layer is dependent on for example, the pigment particle size,
optical density of the photogenerating pigment, and the like.
The overcoating layer 9, which generally ranges in thickness of
from about 0.05 micrometers to about 10 micrometers, and preferably
is of--a thickness of from about 0.2 micrometers to about 5
micrometers, is comprised of materials that are capable of absorbing
20 ultraviolet light so as to prevent the degradation of the electron donor
arylamine materials contained in the transport layer 5, which materials
diffuse to some extent into layer 7. Also, this layer can function as a
protective layer for the photoresponsive device. Illustrative examples
of materials selected for layer 9 include selenium, alloys of selenium,
2S such as arsenic selenium, containing 0.1 to 50 percent by weight of
arsenic, and 99.9 to about 50 percent by weight selenium, arsenic
selenium alloys containing halogens, such as chlorine or iodine, in an
amount of from about 1 part per million to about 1 percent, as well as
30 seleniurn tellurium alloys, arsenic selenium tellurium alloys, the above
selenium alloys containillg germanium, and the like.
Other overcoating materials not specifically disclosed herein may
also be selected providing the objectives of the present invention are
3S achieved including, for example, other inorganic and organic
7~7~
materials, such as vacuum deposited phthal~cyanines, subject to the
provision that these materials absorb ultravi~let light, and function as
an electrically active charge generating layer. Additional!y, solvent
coated organic polymers rnay be used provided they absorb ultraviolet
light, or contain ultraviolet absorbing additives, and further, providing
that the coating process does not result in the diffusion of the
arylamine transport molecule into the overcoating layer 9. Illustrative
examples of organic materials that may be selected for the
lO overcoating layer 9 include various polymers containing therein
organic and/or inorganic ultraviolet light absorbers. Examples of
these materials include polycarbonates, polyesters, silicon polymers,
siloxanes, and the like, having dispersed therein ultraviolet light
absorbers, such as zinc oxide, amorphous or crystalline particles of
selenium, arsenic, or selenium tellurium alloys, phenidone, uvinul,
and the like. Generally, the ultraviolet light absorbers are present in
the organic material in an arnount ranging from about 5 percent by
weight to about 40 percent by weisht, and preferably in an amount of
20 from about 10 percent by weight to about 20 percent by weight.
While it is not desired to be iimited by theory, it is believed that
overcoating tayer 9 prevents the degradation of the arylamines
contained in the charge transport layer that have migrated or diffused
into the photogenerating layer during, for example the solvent coating
of this layer. The overcoating layer is believed to prevent the
penetration into the photoresponsive device of ultraviolet light, and
ionized molecules resulting from corona exposure. The action of
30 ultraviolet light and ionized molecules on the charge transport amin~
molecules is believed to result in the formation of cations. This causes
the photoresponsive device to have unstable electricals due to the
trapped cation radicals. These unstable electricals cause an increase
residual voltage or loss in charge acceptance of the photoresponsive
device due to charge sweepout, adversely affecting the device- and
resulting in images of very low quality.
5(~!7~7'
14 -
Addtionally while the primary function of the overcoating layer 9 is
to prevent ultraviolet light from migrating to the photogenerating layer,
the overcoating layer can also act as a protectant, both physical and
chemical, for the photoresponsive device, and further, this overcoating
^ layer prevents ions generated by the corona charging device to reach
the photogenerating layer. More specifically, as a protective layer, the
overcoating !ayer prevents the mechanical abrasion and/or chemical
damage relating to the developing, charging and cleaning processes
selected for electrostatographic imaging methods. Also, this
overcoating layer enables broad spectral response of the
photoresponsive device in that it combines for example excellent blue
and visible photoresponse of the selenium alloy, overcoating layer
with excellent red and infrared photoresponse of the phthalocyanine
generating layer.
The photoresponsive device of the present invention is useful
primarily as an infrared imaging device, that oan be selected for
incorporation into various imaging systems, wherein light emitted by
lasers are utilized. Such a device has sensitivity ranging from about
700 nanometers to about 900 nanomaters, and thus can be selected
for use with solid state lasers, including helium-neon lasers, and
- gallium arsenide lasers. However, as disclosed herein, ~he
photoresponsive devices of the present inYention are also sensitive to
visible light, that is light having a wavelength of from about 400
nanometers to about 700 nanometers.
Illustrated in Figure 2 is a preferred layered photoresponsive
device of the present invention designated 10, and comprised of a
substrate 15 of an aluminurn drum in a thickness of 4 miilimeters, a
hole transport layer 17, containing 3~ percent by weight of N,N'-
diphenyl N,N'-bis~3-methylphenyl)1,1 ' biphenyl-4,4'-diamine dispersed
3~ in 18, 65 percent by weight of a polycarbonate commercially available
~25~7~
- 15
as Merlon, this iayer having a thickness of ~rom about 10 micrometers
to about 25 micrometers, a photogenerating layer 19, comprised of 30
percent by weight of vanadyl ph~halocyanine, dispersed in 20, 70
percent by weight of a polyester material, PE tO0, cornmercialiy
available from Goodyear Corporat;on, this layer having a thiekness of
1 micrometer, and layer 21, the protective layer, comprised of an
arsenic selenium alloy, containing 2 weight percent of arsenic, and 98
weight percent of selenium, this layer having a thickness of 1.0
o micrometers.
Iilustrated in Figure 3 is a another embodi~ent of the improved
photoresponsive device of the present invention designated 25, this
device being comprised of a substrate 30, of an electro~ormed nickel
belt in a thickness of 100 micrometers, a charge transport layer 32,
having a thickness of 16 micrometers, and containing 40 percent by
- weight of N,N'-diphenyl-N,N'-bis(3-methylphenyl)1,1'-biphe~yl-4,4'-
diamine, and 60 percent by weight of a polycarbonate, commercially
20 available as Merlon, a photogenerating layer 34 containing 30 percent
by weisht of trigonal selenium, dispersed in 33, 70 percent by weight
of a polyester material, PE-49,000, commercially available ~rom E. I.
duPont Co., this layer having a thickness of 0.8 micrometers, and a
protective layer 36, 0.5 micrometers in thickness containing a
selenium arsenie alloy, containing 36 weight percent of arsenic, and
64 weight percent of selenium.
This invention will now be described in detail with reference to the
30 speoific preferred embodiments thereof, it being understo~d that these
examples are intended to be illustrative only, and the invention is not
intended to be limited to materials, conditions, process parameters,
and the like recitsd herein. All parts and percentages are by.weight
unless otherwise indicated.
* Trademark
,~ '
~2S(~7
16-
Moreover, in the examples that follow, the processing steps wereaccornplished in a room containing red safe lights so as to not expose
the materials, particularly the amine charge transpor~ materials, to
light of wavelengths less than 500 Angstroms, in order to prevent
ultraviolet light degradation of such materials.
EXAMPLE I
An overcoated photoreceptive device was prepared by applying,
with spraying, with a Model No. 21 spray gun, commercially available
from Binks, Inc., an amine charge transport layer onto a clean
aluminum cylinder having a diameter of 83 millimeters. The spraying
was accomplished in a laminar air flow booth designed to process
~s volatile solvents containing an entrance means and exhaust means.
This booth also contained a motor driven mandrel with the aluminum
cylind~r mounted thereon, which cylinder was rotated about the
vertical axis of the mandrel at 290 revolutions per minute. The Binks
20 spray gun was located 20 centimeters from the aluminum cylinder, and
the spray booth was maintained at a temperature of 20 degrees
centigrade and a relative humidity of about 40 percent.
Prior to spraying the aluminum cylinder was cleaned by dipping it
into a solution containing 3 percent of sodium carbonate and 3
percent of sodium triphosphate, for 1 minute. Subsequently, the
aluminum cylinder was removed from the solution, washed with water
and immersed for 0.5 minutes in concentrated nitric acid, 67 weight
30 percent. The cylinder was then removed from the nitric acid a~d
rinsed thoroughly with deionized water.
The charge transport layer applied contained a 4 percent solid
solution of a mixture of 65 percent by weight of the polycarbonate
35 resin, Merlon M 39N, and 35 percent by weight of N,N'-diphenyl-N,N'-
~5
- 17 -
bis(3-methylphenyl) 1,1'-biphenyl-4,4'-diamine. This mixture was
prepared by dissolving in a 0.5 liter amber bottle, the polycarbonate
resin, Merlon M39N available commercially from Mobay Chemical, in a
solution containing 60 percent by volume of methylene chloride and
40 percent by volurne 1,1,2-trichloroethane. The polycarbonate resin
was dissolved by tumbling the solution mixture for one hour on a
paint shaker, and after tumbling the resulting mixture was allowed to
stand for about 24 hours at room tamperature.
There was then added to the resulting solution N,N'-diphenyl-N,N'-
bis(3 methylphenyl)-1,1'-biphenyl-4,4'-diamine, which diamine was
dissolved therein by tumbling the mixture for two hours on a paint
shaker. After tumbling, the resulting mixture was allowed to remain at
room ~emperature for about 24 hours.
The resulting solution was then applied to the aluminum cylinder,
by spraying with the Model No. 21 spray gun followed by drying at
40C for 20 minutes, and 160C for 60 minutes, the drying being
a~fected in a forced air oven! There resulted an aluminurn cylinder
containing thereon in a thickness of 15 micrometers, a charge
transport layer comprised of 35 percent by weight of the amine
indicated, and 65 percent by weight of the polycarbonate resin
specified.
There was thén applied to the ~ransport layer, by spraying with ~he
. above Binks Model No. 21 spray gun, a photogenerating layer
containing 30 percent by weight of vanadyl phthalocyanine, dispersed
in 70 percent by weight of a polyester.
The photogenerating composition was prepared by mixing 30
percent by of weight vanadyl phthalocyanine! and 70 percent by
weight of a polyester, commercially available from Goodyear as PE-
- 1~
100 poly~ster. This mixture was placed in a 1 liter amber bottle,
containing in a 60/40 volume ratio, a mixture of solvents of rnethylene
chloride and 1,1,2-trichloroethylene. To the bottle was added steel
shot, 3 millimeters in diameter. The contents of the bottle were then
mixed on a paint shaker for 24 hours.
After removing, the steel shot by filtration there was added to the
resulting slurry sufficient additional solvents so as to result in a
lO mixture containing 1 percent solids, of vanadyl phthalocyanine and the
PE-100 polyester. This mixture was then sprayed onto the above
prepared dlamine charge transport layer, with the Binks spray gun.
After spraying~ the resulting device was dried at 100C for 1.25
15 hours hours in a forced air oven, resulting in a photogenerating layer
having a dry thickness of 1 micrometer.
A top ultraviolet light absorbing overcoating layer was then 2pplied
20 to the above photogeneratin~ layer by placing the aluminum cylinder,
containing the charge transport layer, and the photogeneratin~ layer
in a vacuurn chamber, and vacuum evaporating on the
photogenerating layer, an alloy containin~ 98 percent by weight of
seleniurn and 2 percent by weight of arsenic. The vacuum chamber
25 contained a horizontally rotating, motor driven shaft, a string of four
crucibles, longer in length than the aluminum cylinder, these crucibles
being of the size of 1 x 5 inches, which crucibles were placed ~2
inches in distance away from the cylinder. There was also included in
30 the vacuum chamber a radiant heater, which was placed above the
cylinder, at a distance of 6 centimeters therefrom. These crucibles
were loaded with the arsenic-selenium alloy pellets, each orucible
containing about two grams of pellets. The vacuum chamber was
then evacuated to a pressure of less than a micro Torr, and the
35 aluminum cylinder was rotated at a speed of 200 revolutions per
~;~SC~i7~';7
- - 19-
minute, while being heated to 70C with the radiant heaters. The
arsenic selenium alloy was caused to evaporate and was deposited on
the photogenerating layer by heating each of the crucibles to 300C.
After cooling, there resulted on the photogenerating layer an
overcoating layer of an arsenic selenium alloy, containing 2 percent by
weight of arsenic and 98 percent by weight of selenium, which
overcoating had a thickness of 1.5 micrometers.
There thus results a photoresponsive device comprised in the
order stated of (1) an aluminum substrate, (2) a diamine transport
layer, (3) a photogenerating layer of vanadyl phthalocyanine, and ~4)
and overcoating layer containing a selenium arsenic alloy.
The above prepared device was then charged positively to
800 volts with a corotron and was found to be electrically stable, over
100,000 imaging cycles, in that the device retained a positive charge
20 of 800 volts as measured with an electrostatic voltmeter, commercially
available from Monroe Electronics Inc. of Rochester New York.
Moreover, the photoresponsive device sensitivity ranged from ga
volts/erg/cm~ at 400 nanometers to 60 volts/erg/cm2 at 900
nanometers, as measured with an electrostatic voltmeter,
2~ commerciaily available from Monroe Electronics Inc. of Rochester
New York, which indicates that images can be formed on this device
over a wavelength ranging from 400 nanometers to 900 nanometers.
,
The above-prepared photoresponsive device was incorporated
30 as a photoreceptor into a commercially available Xerox 3300 copying
apparatus, containing exposure larnps generating visible light,
corotrons, a developing station, a fixing station, a transfer station, and
a fusing station. Subsequent to development with toner particles
3S containing a styrene n-butylmethacrylate resin copolymer and carbon
black there resulted ior 2,000 imaging cycles high quality images with
~2'~07~
~ ~o -
excellent solid area coverage and low background, as determined by a
visual observation of these images.
Additionally,the above-prepared photoresponsivedevice was
5 incorporated as a photoreceptor into a commercially available Xerox
2700 printing device~ The resulting images subsequent to
development with toner particles containing a styrene n-
butylmethacrylate copolymer and carbon black particles, were of
excellent resolution with good solid area coverage for 100,000 imaging
cycles, as determined by a visual observation of these images.
Example il
A photoresponsive device was prepared by applying with a Bird
applicator gap thickness of 12~ micrcmeters an amine transport layer,
onto a clean nickel sheet, having a thickness of 50 micrometers. The
~o nickel sheet was cleaned by rep.eating the process steps of Example I
as they apply to the cleaning of the aluminum cyclinder.
There was then applied to the nickel sheet, with a Bird applicator a
solution prepared in a one liter amber bottle containing 8.4 grams of
the available polyester resin Makrolon, and 5.6 grams of N,N'-diphenyl-
N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine in 62 milliliters of
methylene chloride. The device was then dried in a forced air oven at
13~C for 60 minutes, resulting in a transport layer having a thickness
3~ of 20 micrometers.
The transport layer was then overcoated with a photogeneration
layer as follows:
3S In a one iiter amber bottle, 1.77 grams of Makrolon was dissolved
~l~5Q7~7
in 15.6 milliliters of methylene chloride. Added to this solution was
0.43 gr~ms of hydroxy squarilium and giass beads for mixing. This
mixture was then placed on a paint shaker for 90 minutes and the
resulting slurry, after removal of the glass beads by filtration was
coated with a Bird applicator to a dry thickness of about 1 micrometer,
on the amine transport layer. The device was dried at 120C for 60
minutes in a forced air oven.
An overcoating layer of arsenic triselenide (As~Se3) 39 percent by
weight of arsenic, and 61 percent by weight of selenium was applied
to the photogenerating layer in a vacuum chamber by vacuum
deposition, by repeating the appropriate process steps of Example 1.
The device was maintained at room temperature while sufficient
As2Se3 was evaporated to produce an overcoating layer thickness of
0.1 micrometers.
.
The above-prepared device was then charged positively to 800
volts with a corotron! and was found to be electrically stable, over
30,000 imaging cycles in that the device retained a positive charge of
800 volts as measured with an electrostatic voltmeter, commercially
available from Monroe Electronics, Inc. Moreover, the
photoresponsive device sensitivity ranged from 10 volts/ery/cm2, at
2s 400 nanometers, to 30 volts/erg/cm2, at 900 nanometers, as
measured with an electrostatic voltmeter, commercially available from
Monroe Electronics, Inc., indicating that images could be formed on
this device.
EXAMPLE l~l
A photoresponsive device was prepared by repeating the
procedure of Example I with the exception that the top overcoating
layer of the selenium arsenic alloy was not applied to the
photogenerating layer, thus resulting in a photoresponsive device
- ~l2~ 7
- 22-
comprised in the order stated vf (1) an aluminum substrate, (2) a
diamine transport layer, and (3) a photogenerating layer of vanadyl
ph~halocyanine. This device was then incorporated as a
photoreceptor into the Xerox 2700 printer, reference Example 11, and
after 1,000 irnaging cycles substantially no images resulted since
apparently the amine transport layer, some of the molecules of which
diffused into the photo~enerating layer, were adversely affected.
Subsequent to 2,000 imaging cycles, and exposure of the
photoresponsive device to room fluorescent light, slectrical
measurements of the device with an electrostatic voltmeter,
cornmercially available from Monroe Electronics, Inc., indicated that
the charge acceptance of this device without an overcoating layer,
undesirably decreased from 850 volts to tO0 volts, indicating that no
images would be obtainable.
-- In contrast, the overcoated photoresponsive device prepared in
accordance with Example I was incorporated as a photoreceptor in
the sarne Xerox 2700 printer and after 50,000 images were forrned and
developed, no image degradation was observed in that the images
were of high resolution with good solid background. Further, the
overcoated device after 50,000 imaging cycles and exposure to room
fluorescen~ light, showed that the charge acceptance remained at 850
~$ volts with no decreasel as measured by an electrostatic voltmeter,
commercially available from Monroe Electronics, Inc.
- EXAMPLE IV
Two photoresponsive devices were prepared, by repeating the
procedures of Examples I and 111, resulting in the photoresponsive
device without a seienium alloy overcoating, and a photoresponsive
device with a selenium alloy. Both photoresponsive devices were then
exposed to light of a wavelength of 400 noanometers, at an intensity of
3S 2 milliwatts/cm2, for 5 minutes. The device with no seienium alloy
~5Q~77
- 23-
overcoating accepted less than 100 volts, as measured with an
electrostatic voltmeter, commerciaily available from Monroe
Electronics, Inc., while the device containin~ the arsenic alloy
overcoating, reference the device of Example 1, was unaffected and
accepted charge of 800 volts. These measurements indicated that the
non-overcoated device would not form images, since charge
acceptance was not sufficient,and that the overcoated device would
form images.
Further, the photoresponsive devices as prepared in
accordance with Examples I-IV, were individually tested for ultraviolet
light degradation by exposing these devices to unfiltered light from a 1
kilowatt Xenon lamp for a period of 30 seconds, for the purpose of
5 determining whether the devices would accept charge since
acceptance of charge indicates that these devices would form images
and were not degraded by ultraviolet light. Measurements were
accomplished with an electrostatic voitmeter, commercially available
20 from Monroe Electronics, Inc. Those devices containing the arsenic
alloy overcoating, reference the device as prepared in Example 1,
accepted 800 volts of charge, while those devices that did not contain
a selenium alloy overcoating, accepted 0 volts, indicating substantial
degradation of the materials in the device.
,5
Other modifications of the present invention may occur to those
skilled in the art based upon a reading of the present disclosure and
these modifications are in~ended to be included within the scope of
the present invention.
