CA1043893A - Photoreceptor fabrication utilizing ac ion plating - Google Patents

Abstract

PHOTORECEPTOR FABRICATION UTILIZING
ACTION PLATING
ABSTRACT OF DISCLOSURE
A durable photoreceptor having improved flexibility comprising a metal- or metal-coated flexible substrate and an inorganic photoconductor layer in charge blocking contact, the photoreceptor being obtained by initially bombarding the metal substrate, as an electrode, with both negative and positive ions of a non-metallic gas of low ionization potential under AC glow discharge in the presence of oxygen; and exposing the resulting oxidized substrate to a vapor cloud of inorganic ambipolar photoconductive material consisting essentially of positively and negatively charged and uncharged photoconductive material in a low frequency AC electrical field, utilizing the substrate as one electrode, a source of said vapor cloud of photoconductive material or adjacent structure as the other electrode, the latter functional step being effected in combination with at least part of the initial bombardment step.

Description

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BACKGROUND OF THE INVENTION
., . , ,.
This invention relates to improved photoreceptors utilizing flexible substrates and relatively brittle lonizable inorganic photoconductive material, the photoreceptor being obtained in accordance with a three-step ion bombardment clean- ~ -ing, oxidation, ion-deposition process.
~ Photoreceptors, par~icularly those related to xero-graphic copying, traditionally comprise a photoconductive insulating layer such as an element or alloy thereof exemplifiea by selenium ~amorphous or trigonal) and selenium alloys such as a Se-As, Se-Te, Se-Bi, etc., with varying amounts of a halogen.
Such materials are customarily applied in charge blocking contact to a supporting metal- or metal-covered substrate. Suit able substrates or such purpose include, for instance, aluminum, steel, nickel, bra~is, NESA ~trade mark) glass (glass having one surface coated with a thin conductive layer of tin oxide) or -corresponding me~al-coated polymeric materials.
Photoreceptors comprising at least the above elements -~
are generally given a uniorm electrostatic charge and the ,, ~ . , . .. , ~ .
~ 20 sensitlzed surace then exposed to an image pattern deined by 1~ an electromagnetic radiationi such as light. Light impingement ~ results in a selective dissipation of the i~itially applied ij . . . .
charge leaving a positive electrostatic image. The electro-static image is then customarily developed by applying opposite-lj , . .
ly charged marking particles onto the charge-bearing photo-t ~ receptor surface.
The above basic concept was originally described by 1 : . ...
.~ ~
Carlson in U. S. Patent 2,297,691, issued October 6, 1942, and ~i ~ has been slnce amplified and redescribed in many related t~ : 30 patents in the field. Generally speaking, photoconductive layers uitable or carrying out the above functions have a specific resistivity of about 101 - 1013 ~ ~ -

-2-,j~ ' , . .

ohm-crn, in the absence of lllumlnation. In addition, their resistivity must drop at least several orders of magnitude where exposed to an activating radiation such as light.
Photoconductive layers meeting the above criteria also normally exhibit some loss in applied charge, even in the absence of light exposure. This phenomenon is known as "dark ;~ decay" and will vary somewhat with sensitivity and with usage of the photoreceptor. The e~istence of the problem of "dark -~``ii decay" is well known and has been controlled to a substantial extent by incorporation of tnin barrier layers such as a dielectric fi1m between the base or substrate and the photoconductive . i iss~d ~L.3~S~ ~i5, 1959r 'j4~ ~ ~ ` insulating layer. U.S. Patent 2,901i34i3 of Dessauex et al ~ -r: utilizes a film of aluminum oxide of about 25 to 200 an~strom or an insulating resin layer, such as~a polystyrene of about O.l to 2 microns thickness for suchi purpose. With some limitations, these~barrier layers function to allow the photoconductive layer to support a charge of high field strength while minimizing "dark decay." When activated by~illumination, however, the photoconductive layer and barrier layer must become sufficiently conductive to permit substantial dissipation o~ the applied charge~in light-struck areas within a short period of time.
In addition to the above-indicate~ electrical requirements, it is al90 becoming increasingly important that photoreceptors meet rather stringent requirements with regard to mechanical properties i~uch as flexibi1ity and~durability.
Such additional criteria become particularly important in modern automatic copiers operating at high speeds where the photo-receptor is in the ~orm o~ an end1s~s ~1exibls belt (re~. U.S~
Patent 2,691,450). While belt-type photorecePtori~ hav~ many ~ advantages, thsre are also serLous technical problems inhsrsnt `J' -3--`:,' ,:

3~ 3 in their use. For example, high speed machine cycling condi-tions require particularly strong adhesion between the photo conductive layer and the underlying substrate. Unfortunately, however, some of the most sensitive and efficient photoconductive materials are relatively brittle as films and do not generally ~ -adhere well to flexing metal substrates~ It is very important, however, that any interface between the el'!ectrically conductive ;
supporting substrate and the photoconductive layer be stable and strongly adherent to both since changes at this point will have ~; . .
a substantial effect on the electrical properties of the photo~
receptor,. - ~
The above problems have been considered and resolved ~ .
to a substantial extent in a process described in a copending .
aRplication having the same filing date by Lewis B. Leder, John C. Schottmiller and Harold H. Schroeder entitled "Improved Photo- . ~
receptor Fabrication" Canadian Serial No. 226,.579 filed May 8, : ;:
1975 wherein the sub:strate is initially bornbarded by non-metallic ; :
ions under a DC glow discharge in the presence of air or an inert ...
rare gas containing at least 1% by volume available oxygen. The 20 ~ initial step, as desaribed, is Eollowed or overlapped by further ~; bor~ardment o~ the su~stxate with a mixture of high energy photo-.r conductive cations, and non-metallic high energy cations such ; as nitrogen or argon plus uncharged vaporized photoconductive material. While the above-described process repxesents a sub- ; ;
~ stantial technical breakthrough in utilizing the more efficient 3 ~ brittle photoconductors in flexible belt-type photoreceptors there still remai.ns room for irnprovement. In particular, the production of high energy photoconductive cakions in a glow dis-~ .
,i charge for bonbardrnent purposes is relatively inefficient (up : -;30 to 5% at best) and requires expensive electrical equipment _4_ 3~9q~ ::
of limited capacity. Moreover, the insulative nature of preferred inorganic photoconductive materials make it difficult to avoid the accumulation of some surface charges on the substrate in a , DC glow discharge environment, In effect, this results in a ' ' ... . .
substantially lowered efficiency in depositing ionic photo-~ conductive material of like sign onto the substrate.
,- Neither the use of an oppositely charged screen nor an increase in field strength will completely avoid this problem. -~ Summa~y of_the Invention :` :' ,.
In accordance with this invention there is provided a ', method for obtaining flexible photoreceptors having improved , ' " durability and adhesion between components thereof comprising a , .. . ......
~i flexible metal- or metal-coated substrate and an inorganic ambi- '~
' polar ionizable photoconductive layer in charge-blocking contact `, with the substrate, comprising initially bombarding the substrate as an electrode under DC or low frequency AC glow discharge with ions of an inert non~metallic gas in the presence of available . ,,~ , .
oxygen; and exposing the resulting oxidized substrate as an ,~
~1~ electrode to a vapor cloud from a donor source comprising posi~
tive and negative ions of the desired ambipolar photoconductiv ma~erial, ions of the inert non-metallic gas comprising the '1 glow discharge, and uncharged vaporized photoconductor material, `~, in or adjacent to a low frequency AC electrical field utilizing the donor source of the vapor cloud of photoconductive material or adjacent structure other than the substrate as an additional ~, electrode. Such vapor source includes, for instance, a resistance heated stainless steel or graphite crucibles containing the photo-'~ conductive material as electrodes.
This invention also relates to flexible photoreceptors produced by the previously described method.

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Suitable substrates for purposes of the present invention use~ully consist of relativel~ thin metal ~oils of ~
copper, steel, brass, aluminum, nickel, or a corresponding .;
met~ coated flexible polymeric base such as a coated polyethylene terephthalate. Of particular interest as substrates are aluminum-coated polyethylene terephthalate belts and nickel beltsO ' ' - . ;' ~: Ambipolar ionizable photoconductive material suitable :
. for use in the instant inventive process are exemplified by .- .
selenium and corresponding alloys thereof with arsenic, tellurium, .:
germanium, an~imony, bismuth, andjor~one or more halogens such : .:~
.. . .as chlorine, bromine, or iodine. Such photoconductive materials~ ~.
are obtainable by subjecting selenium, plus smali amounts of : one or more o~ the above alloy elements and/or a halogen to ~ ; heat~in a sealed container.~
,fi~- For:purposes of the present invention, the finished :1 ' . .
photoreceptor includes at least one thi.n oxide layer as a charge `.
blocking layer in general accordance with. the teaching of U.5.
,. . . . . .
Patent 2,901,3~8. When flexible metal belts such as nickel . ~ .
`; beltci are~used,~however, special chemical treatment has hitherto ; .
; ~: been required in order to obtain adequate adhesion o~ the photoconductive layer to the substrate and a controlled amount . : -oxi~e blocking la~er or la.~ers. This problem is avoided by the initial bo ~ ardment of the substrate, as an electrode under ...
DC or low frequency ~C glow discharge, with positive ions 1 . . . .
.

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of a non-metallic yas as above described. This step is besit carried out, ~or instance, by evacuating a suitably modif.ied vacuum coater down to a pressure of about 5 x 10-.5 Torr and then backfilling with up to abou-t 30 microns of air. A pressure of about 5 - 20 microns is generally preferred for this purpose, depending upon the gases utilized. While air under reduced pressure is aceeptable.,.it is also found convenient, on occasion, to utilize various alternative mixtures of inert ion producing and oxidizing gases at comparable pressures. Such include, for instance, argon-oxygen, argon-air, argon~C02, or a mixture of nitrogen and oxygen, etc. In each case, however, the amount of ~vailable oxygen for initial oxidation of the substrate sh~uld not be less than about 1% by volume of the available ~.
gases, and a glo~l discharge must be maintainable.
Maintenance of a satis~actory glow discharge fo~
purposes of effecting the initial ion bombardment and~oxidation o~ the substrate can be satisfactorily effected for purposes of the present invention under a DC field at a potential ranging rom about 1500 to about 3500 volts and a cathode current density of about .05 - .5 ma/cm2, depending upon the type and pressure o~
gas used to form the ions. Alternatively, a low frequency AC glow ! j . .
,~ discharge of about 60 - 400 cycles, a potential o~ about 500 to about 1400 volts and a substantiall.y reduced current density of about ~0~ - .15 ma/cm2 is al~o found to be sufficient~
Prior to completion o~ a period of time sufficient to ' orm an oxide barrier layer of about 10 - 200 angstrom thickness on the substrate, and assuming that~the substrate has been brought up to a suitable temperature (55 - 60~C.) by ion bombardment (about 5 - 20 rninu~es and prearably 8 - 10 minutes under tne ~ 7~

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'"'''-' ' ' . " ' ' ,, . ' ' ' " . ' '' .' ~ :'' ": , ' .', ' ' , ', ' '' ' conditions ind.icated above), the oxide bearing substrate is si.multaneously exposed to a vapor cloud of charged and uncharged photoconductor particles evolved from a heated photoconductive ~.
source by introducing the vapor into and adjacent to an area of a low fre~uency AC glow discharge. Under such conditions, it has been found that both negative and positive high energy ions of the ambipolar photoconductive material are formed in good yield under conditions favoring efficient deposition onto the su~strate ele~trode. In this mannex, the efficiency of high energy ionic deposition is increased about two-fold over that which would occur under a DC glow discharge alone, and the troublesom~ buildup of surface charges on the partially eovered substrate is controlled. --~ :
., j . In the abovs-described situation, the simultaneously oceurring substrate bombardment by non-metallie ions such as of argon or nitrogen wiIl still displace~the more loosely adherent photoconduetive particles already condensed onto the substrate in favor of eharged photoeonductive partlcles having greater ariginal energy eontent. This process is important and oecurs despite the relatively low coneentration of high energy photoconduetor ions obtained relative to the totaI
` amount o thermally ereated photoconduetive particles- .
For purposes o~ the present inventionO the depo~ition ,j, of photoeonduetive material onto the oxide-eoated substrate is best ef~eeted by separately heating the souree of photoconduetiva material to a temperature between room temperature and the . maximum evaporation temperature of the photoeonductive material.
For ~ueh purpose, thq pre~rred temperature range (1) favors .. " ~ .
:' ~maximum vap~r ~oncentration and ~i.el~ conditions eommen~urate , with maintenance o~ a low ~requeney ~,C glow diseharge proximate :'.''~ ~ ' -; -8-,. . . .
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~g~ h to the heated clonor electrode and the substrate electrode, and (2) favors the highest possible conversion of uncharged photo-conductive vapor into positive and negative ions and the production of non-metallic gas ions to effect the impaction of the highest possible concentration of high energy photoconductive particles onto the substrate. As above indicated, it is also much to be desired to minimize the accumulation of positive or negative charges on the surface of the partially coated substrate.
- For purpose of the latter photoconductor ion deposition step, it is found that an AC field up to about 500 cycles and having a potential not exceeding about 1400 volts under glow discharge is adequate. Preferably, however, a 60 - 400 cycle AC, 500 - lO00 volts field and a current density of about .01 .
to about .lS ma/cm2 is considered optimal.
In further reference to the second or photoconductor deposition step, it should be kept in mind that the concentration of argon or similar non-metallic inert gas ions must bs maintalned in the coater at a pressure sufficient to maintain an AC glow discharge even though the oxygen component may be ~ubstantially reduced in concentration or eliminated altogether for the latter photoconductor deposition step. An adeyuate concentration i5 generally obtainable although not limited to maintenance of a pressure o~ about 5 - 30 microns.

,1 . , .
As a practical matter, the above-described second phase o~ the instant inventive process is conveniently accomplished when desired by increasing the amount of vacuum *o 5 x 10~5 Torr and then backfilling the coating chamber with up to about 5 - 30 microns of argon, nitrogen, xenon or similar glow discharge , ~ :
~ maintaining inert gas. This technique e~fectively reduces the .,, ~ . .
~ r~lative concentration of oxygen and assures adeyuate displacement .1 . .
~ o~ the more loosely adheriny photoconductive material.
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, . . . . . . . .. . .

In order to effectively raise the vapor pressure of the photoconductive material for deposit onto an oxidized substrate, it is also convenient if the source is independently heated. This can be accomplished, for instance, by resistance heating by the use of an electron beam or gun directed at , the source or by separate ion bombardment to vaporize the photoconductive material. In any case, the optimum temperature for this purpose will vary with the particular p~lotoconductive material use~d, the distance between source and substrate, and the atmospheric composition and pressure utilized. By way of -example, a source temperature of up to about 350C. and preferably about 180C, - 350C. is found ade~uate for vaporizing selenium -i and most of the known selenium alloys at a pressure up to about 30 microns.
During the period of photoconductor deposition onto the clean oxide-coated substrate, it is essent;ial that a glow discharge be maintained for the purpose o~ creating photo-conductor ions but without seriously limiting the rate and area ef deposition o~ the photoconductive material onto the substrate.

i One embodiment o~ the relationship of the electrodes and other essential componentis of the above-described two major pha~es o~ the inventive process are very generally represented ~ ~ 5 f l ~r ~
A in modi~ied form in ~i~g~ IA and IB. In/IA either a DC or AC current is utilized to ~orm the oxide layer on the suhstrate.
In Dii~F;~ IB a low requency AC curreint is utilized to e~fect deposltion of photoconductor materlal onto the oxida covered substrate. Where an ~C field iB utilized, however, it is not .
posisible ~o visuall~ identify individual areas a~ the glow discharge.

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,; Xn Pigures 1~ and lB, therefore,~ (a) and ~d) conveniently `, ', r,ep~esent the substrate electrode and a heated photoconductor source~containir.g photoconductor material ~M), while areas (b) `"',~
and~c) represent the Cathode Dark Space and Negative Glow areas when a DC Glow Discharge is used. ~;
The initia~ bombardment o the substrate is preferably 'carried out at a pressure of about 10 - 20 ~, at a potential of about 500 - 3500 volts ~500 - 1400 v AC)~and a current density of about .01 - .3 ma/cm2 ~preferably .01' - .15 ma/cm~) ';
' 10~, to form~a clean oxide blocking layer under glow dis~harge. This - step, whether e~fected under AC or DC, has the triple function ' o~ (l) c3,eaning the substrate, (2) heating it to an appropriate temperature for coating, and (3) ~orming an oxide charge-blocking layer. Looking to the specifics of this step it is noted that when a D voltage is applied, a breakdown of available inert ' non-metallic gases occurs and an "abnormal glow" is preferably established, whereby current flow is positively correlated with voltage. l~he formation and ch~racteristics of such "abnormal ~low" discharges are described, for instance, by G. Francis in "The Glow Discharge at Low Pressure"; Vol. 22, Encyclo of Ph~ s (Springer-Verlag, Berlin [1956]).
For purposes of the present invention , it is further noted that the preferred electrode spacing is such that only the Cathode Dark Space and Negative Glow can be visually identified in the DC mode and not at all in the AC field applied between the substrate and the photoconductor source.
It is also known that almost all of the applied potential is dropped across the area corresponding to the Cathode Dark Space and that the highest concentration of gas ions exist in the area corresponding to the Negative Glow region. Thus, an ion ~produced in the Negative Glow region will be accelerated across the Cathode Dark Space and impact the substrate at an energy level considerably higher than that of a thermally excited atom or molecule. It is noted, in this ronnection~ that the glow discharge current can be monitored to determine when a substrate sur~ace has been cleaned by ion bombardment (Diagram IA) since ; .
J ~' the glow discharge current will gradually decrease to a lower , steady statç value. This i5 because the clean rnetal substrate surface has a lower secondary electron emission coe~ficient than a dirty or oxide coated surface.

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Pri~r to completiorl of the oxide barrier layer on the - ~ substrate, and asquming that the substrate is at a suitable 3,~ temperature ~i.e. about S5 - 60 C.), the second p~lase of the :s ~
instant process is conveniently begun (ref. Diagram IB). This - ~ is effecte.d by evaporation of pbotoconductive material into ,. ~ .
i~ t~e glow discharge region. Since the evaporated photoconductor , . .

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material is ambipolar, both positive and negative ions will be formed in the glow discll~r~e. rlloreover~ the speed of ion mi~ration is so much higher than the field frequency both positive and negative photoconductor ions can impact the substrate at a high energy level. This effectively almost doubles the number of high energy photocondu~tor ions available for impactlng the substrate.
By effecting the above deposition in the presence of positive non-metallic gas ions such as argon or nitrogen, it is also possible to displace a substantial amount of low energy de~osited (unionized) photoconductive material from the substrate in favor of the available charged high energy photoconductor ions.
Successful impact deposition, however, requires a balance between removal and deposition so as to obtain a net coating comprising a larger proportion Qf inltially ionized photoconductor material. The time required to obtain an ade~uate photoconductive layer will largely depend~directly or indirect~y on these factors.
Since the chief advantage of depositing an ionized vitreous photoconductor on a metallic substrate is realized in improved adhesion and acceptable or improved inter~ace electrical properties, only a small thickness need be deposited as described.

Generally speaking, about 1 - 10% of the total thickness i~
,~,. ~, . , uficient but not limiting, with the balance of the deposition compLeted by conventio~al vacuum deposition techniques at about 5 x 10 5 Torr. If desired, however, more of ~he photoconductive layer may be deposited by mean~ of the above-described process.
The following examples specifically demonstrate preferred embodiments of the present invention without limiting it thereby~
EXAMPLE I

.,, - ~ A stain-free nickel alloy test belt identifi~d as A-l ~ ~ ~ having a thickness of 4.5 mil (.0045"), a length of 10" an~ a ,. . .
~ 13-, .,; ' , " ,,, , ~ ,. . ,~ . . , ,: ' ~3~
circumference of 15", is cleaned with a hot aqueous solution containing 10% by weight of "Mitchell Bradford #14 Cleaner"
and then rinsed in deioni~ed water for about 2 minutes.
A sample belt identified as A-l is mounted in a vacuum coater on a rotatable mandrel insulated from ground and about 6" away from 3 stainless steel crucibles equipped with resistive heating means and containing photoconductive selenium alloy consisting of about 99.5% selenium and .5% arsenic. After evacuating the coater to 5 x 10-5 Torr and backfilling to about 10 ~ air pressure, a glow discharge is formed using the belt and the alloy-containing stainless steel crucibles as electrodes .
in a 700 volt 60 cycle AC field at .05 ma/cm2. After lO minutes under glow discharge, the steel crucibles are heated up to about :
250C. for 3 minutes. Thereafter, the field is turned off and the coater pressure again e.vacuated to 5 x 10-5 Torr and normal vacuum deposition permitted at 300C. for 10 additional minutes.
Throughout the entire treatment the mandrel and mounted substrate are constantly rotated at about 10 revolutions per minute to obtain a uniorm photoconductive layer 50~u ln thickness. The coater is then permitted to return to ambient conditions and the photoreceptor removed and tested for electrical properties and adhesion. The results are reported in Table I infra.
EXAMPLE II
.. ~ : ;~
!: , , .
Two nickel test belts of identical size and shape as tes~t belt A-l, and identified as A-2 and A-3 respectively, are cleaned as in Example I and coated as ~ollows:
élt A-2 lS coated as i.n Example I except that a 20JU
backill o oxygen (10% by volume) and argon ~90% by volume) mixture is utilized in place of air during the initial cleaning, ~, ~
heating and oxidation phase. The AC electrical field is operated .. :

.;

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;i~O~ o~ , wlder 60 c~cles at 1000 volts and with a current density of .15 ma/cm2. After lO minutes under glow discharge, the oxygen flow is stopped and glow discharge con~inued under argon at 20~u.
The AC voltage is then decreased to 500 volts and .lO ma/cm2 current density, and the crucibla heated up to about 240C.
for 5 minutes, during which time the photoconductor material is partially vaporized into the glow discharge. Thereafter, the electric field and argon ~low are cut off and regular vacuum deposition effected at 280C. for lO additional minutes. The ,~ coater is then permitted to return to ambient conditions, and the photoreceptor belt removed from the chamber and tested as in Example I. The results are reported in Table I infra.
Belt A-3 (control) is cleaned and oxidized under glow discharge in an identical manner as belt A-2, the glow discharge then being cut off and regular vacuum deposition 3~ ~ ~ ef~ected at 5 x 10 5 Torr for about 20 minutes at crucible temperatures of 280C. to obtain a pho~oreceptor having a photo-conductor layer of about 50~u thickness. The cooled photo-receptor belt is re ved and tested as in Example I and the results reported in q'able I infra.
i, . .
,~- EXAMPLE III
, : : . . .
~ Belt A-4 ~s treated exactly as belt A-l except that 3~
the belt i5 not chemically cleaned or washed prior to mounting in the vacuum chamber for oxidation of the substrate. After ; coating as in A-l, the photoreceptor is cooled, removed and t ~ tested as b~fore, and the results reported in Table I.
XAMPLE IV
Test belt A-S is treated exactly as in ~xample I except that the inltlal oxidation step ~i.e. ion b~mhardment cleaning, heating and oxidation) is effected under a DC glow discharge at 2000 :~ .
./~: :
. ;~

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~ 5~55~ -volts at a current density of .25 ma/cm2. An initial photoconductor layer is then applied under an 800 volts 60 cycle glow discharge at a current density of .06 ma/cm2 for 2 minutes. The remaining photoconductor material is then applied by vapor deposition to obtain a 50,u coating as in Example I. The r~sulting photoreceptor belt is cooled, removed and tested as be5fore, the results being reported in Table I.
EXAMPLE V
` An identical nickel test belt identified as A-6 is chemically cleaned and rinsed as in Example I and then heated in air for 25 minutes at 350C. and cooled to effect thermal oxidation ~60 ~). The oxidized belt is then mounted for 20 minutes in a coater at 5 x 10 5 Torr at a crucible temperature of 300C. to obtain a 50,u photoconductor coat. The pho~o-receptor is then cooled, removed and tested as be~ore, and the res~lts reported in Table I.
. .:

~ TABLE I
.. . .
Test Belt Capacitive 20 sec. ¦ Mandrel Test Charge Dark Decay (1 1/2" diam~ter) (v/u) v/sec .~ ~ _ _ _ _ . , , .. .
, A-l 30.1 10 P

A-2 2~.4 12 P

A-3 25.5 14 F
~control) 5,~ A-4 26.2 11 P

5'~;- A-5 23.4 16 P

~ A-6 24.1 15 F
. .
P =~ pass (no cracks or spalls obser~ed) F ~~ fail tone or more cracks or spalls observed) when belt is bent around a 1 1/2" pipe5 once at room temperature.
, ~ .

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EX~MPLF VI
: . Example ~ is repeated using respectively steel, aluminum, and brass test belts of the same dimensions as the nicke:L test belts A-l through A-6. The results obtained are found to be ', consistent with Example I with respect to resistance to cracking~
i and spalling.

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Claims (11)

WHAT IS CLAIMED IS:

1. A method for obtaining flexible photoreceptors having improved durability and adhesion between components thereof comprising a flexible metal or metal-coated substrate and an inorganic ambipolar ionizable photoconductive layer in charge-blocking contact with the substrate, comprising initially bombarding the substrate as an electrode under DC or low frequency AC glow discharge with ions of an inert non-metallic gas in the presence of available oxygen; and exposing the resulting oxidized substrate as an electrode to a vapor cloud from a donor source comprising positive and negative ions of the desired ambipolar photoconductive material, ions of the inert non-metallic gas comprising the glow discharge, and uncharged vaporized photoconductor material, in or adjacent to a low frequency AC electrical field utilizing the donor source of the vapor cloud of photoconductive material or adjacent structure other than the substrate as an additional electrode.

2. The method of Claim 1 wherein the exposure of the oxidized substrate to the vapor cloud is effected in conjunction with at least part of the initial substrate bombardment step.

3. The method of Claim 1 wherein initial ion bombard-ment for oxidation of the substrate is effected at an atmospheric pressure up to about 30 micron , the amount of oxygen present being not less than about 1% by volume of available gases.

4. The method of Claim 1 wherein exposure of the oxidized substrate to a vapor cloud of photoconductive material is effected by heating the photoconductive material to an intermediate temperature between room temperature and the maximum photoconductive evaporation, utilizing the substrate as one electrode and the donor source as another electrode under a low frequency AC glow discharge.

5. The method of Claim 3 wherein the initial positive ion bombardment of the substrate is effected under an oxygen containing atmosphere at about 5 - 30 microns pressure.

6. The method of Claim 4 wherein the photoconductive material is heated by electron bombardment, by ion bombardment or by resistance heating means during photoconductor deposition unto the oxidized substrate.

7. The method of Claim 1 wherein the substrate is a charge conductive metal belt and the inorganic ionizable ambipolar photoconductive layer comprises selenium and alloys thereof with one or more of tellurium antimony, bismuth, arsenic and a halogen.

8. The method of Claim 1 wherein the substrate is a charge conductive metal belt and the inorganic ionizable photoconductive layer comprises selenium or a selenium-arsenic halogen alloy.

9. The method of Claim 1 wherein additional photo-conductive material is subsequently applied to the substrate by vapor deposition.

10. The method of Claim 7 wherein the substrate is a nickel belt.

11. The method of Claim 8 wherein the substrate is a nickel belt.