EP0448780B1 - Electrophotographic imaging member - Google Patents
Electrophotographic imaging member Download PDFInfo
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- EP0448780B1 EP0448780B1 EP19900120917 EP90120917A EP0448780B1 EP 0448780 B1 EP0448780 B1 EP 0448780B1 EP 19900120917 EP19900120917 EP 19900120917 EP 90120917 A EP90120917 A EP 90120917A EP 0448780 B1 EP0448780 B1 EP 0448780B1
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- European Patent Office
- Prior art keywords
- layer
- blocking layer
- charge
- layers
- hema
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
- G03G5/14—Inert intermediate or cover layers for charge-receiving layers
- G03G5/142—Inert intermediate layers
Definitions
- This invention relates to an electrophotographic imaging member comprising a charge blocking layer containing a specific hydroxy methacrylate polymer and to a process for using said member.
- a xerographic plate containing a photoconductive insulating layer is imaged by first uniformly electrostatically charging its surface. The plate is then exposed to a pattern of activating electromagnetic radiation which selectively dissipates the charge in the illuminated areas of the photoconductive insulator while leaving behind an electrostatic charge pattern in the nonilluminated areas. This resulting electrostatic latent image may then be developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer.
- a photoconductive layer for use in xerography may be a homogeneous layer of a single material such as vitreous selenium or it may be a composite layer containing a photoconductor and another material.
- a composite photoconductive layer used in xerography is illustrated in US-A 4,265,990 which describes a photosensitive member having at least two electrically operative layers.
- One layer comprises a photoconductive layer which is capable of photogenerating holes and injecting the photogenerated holes into a contiguous charge transport layer.
- the outer surface of the charge transport layer is normally charged with a uniform charge of a negative polarity and the supporting electrode is utilized as an anode.
- the supporting electrode may also function as an anode when the charge transport layer is sandwiched between the anode and a photoconductive layer which is capable of photogenerating electrons and injecting the photogenerated electrons into the charge transport layer.
- the charge transport layer in this embodiment must be capable of supporting the injection of photogenerated electrons from the photoconductive layer and transporting the electrons through the charge transport layer.
- CGL charge generating layers
- CTL charge transport layers
- the photosensitive member described in US-A 4,265,990 utilizes a charge generating layer in contiguous contact with a charge transport layer comprising a polycarbonate resin and one or more of certain diamine compounds.
- Various generating layers comprising photoconductive layers exhibiting the capability of photogeneration of holes and injection of the holes into a charge transport layer have also been investigated.
- Typical photoconductive materials utilized in the generating layer include amorphous selenium, trigonal selenium, and selenium alloys such as selenium-tellurium, selenium-tellurium-arsenic, selenium-arsenic, and mixtures thereof.
- the charge generation layer may comprise a homogeneous photoconductive material or particulate photoconductive material dispersed in a binder.
- Other examples of homogeneous and binder charge generation layer are disclosed, for example, in US-A 4,265,990.
- Additional examples of binder materials such as poly(hydroxyether) resins are taught in US-A 4,439,507.
- the disclosures of the aforesaid US-A Patent 4,265,990 and US-A 4,439,507 are incorporated herein in their entirety.
- Photosensitive members having at least two electrically operative layers as disclosed above provide excellent images when charged with a uniform negative electrostatic charge, exposed to a light image and thereafter developed with finely divided electroscopic marking particles.
- the supporting conductive substrate comprises a charge injecting metal or non-metal
- difficulties have been encountered with these photosensitive members due to discharge in the dark. More specifically, these photosensitive members do not retain sufficient charge during the charging and subsequent imaging exposure and development steps.
- Most metallic ground planes have a natural oxide layer which inhibits charge injection. Typical metals of this type are aluminum, zirconium, titanium and the like. Some exceptions are metals that do not oxidize such as the noble metals, e.g., gold, platinum and the like that promote charge injection.
- Ground planes containing other materials such as copper iodide or carbon black also inject charge into charge generation layers so the photoreceptor does not effectively hold charge during the charging, image exposure and/or development steps.
- Copper iodide ground planes as disclosed in, for example, US-A 4,082,551 encounter degradation problems during cycling.
- Charge blocking layers are frequently used on metalized or other kinds of ground planes to inhibit charge injection. Some charge blocking layers require an additional adhesive layer between the charge generation layer and the conductive ground plane.
- the photoreceptors When attempts are made to use resins as a blocking layer, the photoreceptors usually exhibit increased residual charge with cycling. Failure to effectively hold charge during the image exposure and development steps or increased residual charge formation with cycling cannot normally be tolerated in precision copiers, duplicators, and printers.
- Copolymers of methyl vinyl ether and maleic anhydride such as the Gantrez AN resins from GAF Corporation have been utilized in blocking layers.
- these copolymers of methyl vinyl ether and maleic anhydride are sensitive to water and rapidly hydrolyze to form acidic products which are corrosive and attack metal ground planes of photoreceptors during electrical cycling. Loss of the ground plane due to corrosion during electrical cycling eventually prevents an electrophotographic imaging member from discharging. This is manifested by an increase in background toner deposits in the final image during electrical cycling.
- the mechanical properties of copolymers of methyl vinyl ether and maleic anhydride are affected at high humidity and cause flexible electrophotographic imaging members to delaminate.
- Poly(vinylalcohol) has been evaluated for use as a blocking layer.
- this material is very viscous and difficult to apply as a coating.
- very dilute but still viscous poly(vinylalcohol) aqueous solutions requires numerous spray coating passes to build up blocking layer dry thickness to the desired level.
- the solvents that may be employed for poly(vinylalcohol) are not conducive to the formation of high quality coatings.
- the adhesion of poly(vinylalcohol) to many conductive layer polymers is poor.
- a multilayer electrophotographic element comprising a conducting layer, a photoconductive layer, and a polymeric interlayer having a surface resistivity greater than about 10 12 ohm/sq between the conducting layer and the photoconductive layer.
- the interlayer comprises a blend of at least two distinct polymeric phases comprising: (a) a film forming water or alkali-water soluble polymer and (b) an electrically insulating, film forming, hydrophobic polymer.
- the conducting layer may contain cuprous iodide imbibed in a copolymeric binder of polymethylmethacrylate and polymethacrylic acid.
- a complex two phase hazy layer composed of a complex terpolymer (65 wt. percent) of poly-(methylacrylate-vinylidene chloride-itaconic acid) and polyvinylmethylether maleic anhydride) (35 wt. percent) is employed as an organic solvent barrier, an adhesive aid, and a hole blocking layer.
- the film forming water or alkali-water soluble polymer may contain pendant side chains composed of groups such as acidic, hydroxy, alkoxy and ester groups.
- a unitary photoconductive element having an electrically conducting layer, a photoconductive layer thereon, and a multilayer interlayer composition interposed between the conducting layer and the photoconductive layer.
- the multilayer interlayer composition comprises a layer containing an acidic polymer material, a layer containing a basic polymer material, and an acid-base reaction product zone formed at the interface of the acidic polymer-containing layer and the basic polymer-containing layer.
- the basic polymer materials appear to be basic because of the presence of amine groups.
- Various basic amino methacrylate and acrylate monomers and polymers are disclosed.
- the complex barrier bilayer adjacent to a Cul conductive layer may be composed of an acrylic or methacrylic acid copolymer and the top layer composed of a poly 2-vinylpyridine-polymethylmethacrylate copolymer such that a salt interlayer forms at the interface of these acidic and basic polymers.
- the multilayer interlayer composition provides good adhesion between the conducting and photoconductive layers of the resultant unitary element and can function as an electrical barrier blocking positive charge carriers which might otherwise be injected into the photoconductive layer from the underlying conducting layer.
- An electrophotographic imaging member comprising a charge generation layer, a contiguous charge transport layer and a cellulosic hole trapping material located on the same side of the charge transport layer as the charge generation layer.
- the cellulosic hole trapping material may be sandwiched between the charge generation layer and an electrically conductive layer.
- the conductive layer for the member may include gold and various other materials such as a hydrophilic material comprising a hygroscopic and/or antistatic compound and a hydrophilic binding agent.
- Suitable hygroscopic and/or antistatic compounds include, for example, glycerine, glycol, polyethylene glycols, hydroxypropyl sucrosemonolaurate, etc.
- Suitable hydrophilic binding agents include gelatin, polyvinyl alcohol, methylcellulose, carboxymethylcellulose, cellulosesulphate, cellulose hydrogen phthalate, cellulose-acetatesulphate, hydroxyethyl cellulose, etc. for obtaining a good adhesion of a hydrophilic layer and a hydrophobic polymeric sheet.
- a coating of a polymeric substance may be used on paper sheets to prevent organic polymeric photoconductive substance and radiation sensitive substance from penetrating within the paper sheet. The coating of a polymeric substance must not prevent the carrying off of electrons from exposed image areas during radiation.
- Coatings include cellulose diacetate, cellulose triacetate, cellulose acetobutyrate, ethyl cellulose, ethyl cellulose stearate or other cellulose derivatives, polymerisates such as polyacrylic acid esters, polymethacrylic acid esters, polycondensates such as polyethylene glycol esters, diethylene glycol polyesters, etc.
- An organic polymeric photoconductive substance together with a radiation-sensitive substance is dissolved or dispersed in an organic solvent and coated onto the surface of a suitable support.
- US-A 3,428,451 issued to D. Trevoy - Appears to employ some of the conductive coatings described in US-A 3,245,833 (see above) for use in electrically conductive supports for radiation sensitive recording elements (e.g. an electron microscope where direct electron recording is carried out). Coating applications do not appear to be electrophotographic.
- the E1 ⁇ 2 photosensitivity was about 10 ergs/cm 2 (Example 3) of 640 nm incident light.
- the E 1 / 3 photosensitivity ranged from 6.7-14.9 ergs/cm 2 using the same light source.
- No test of a barrier layer V O and V R behavior with repeated xerographic cycling is given. The above data is for only one cycle.
- These crosslinked barrier layers do reduce the number of white spots produced in the imaged film.
- the barrier layer also functions as a solvent barrier to toluene and methylene chloride in addition to its electrical function as a hole injection barrier.
- cuprous iodide conductive layers are disclosed wherein the cuprous iodide is imbibed into the polymeric substrate or a subbing adhesive layer on the polymeric substrate when the cuprous iodide - acetonitrile solution is coated without a binder in the same solution.
- a binder for the cuprous iodide is generated underneath the Cul by appropriate solvent swelling and/or heat and the result is a Cul - binder conductive layer.
- a Cul - polymer conductive layer wherein cellulose acetate butyrate is used as the polymeric binder is coated directly. The Cul is imbibed and no distinct Cul layer remains.
- An electrically activatable recording element comprising a polymeric electrically active conductive layer.
- a list of useful copolymers for the polymeric electrically active conductive layer includes many polymethacrylates can be found at column 6, lines 36-62. Synthetic polymers are preferred as vehicles and binding agents in the layers of the electrically activatable recording element. The use of polymers such as poly(vinylpyrrolidone), polystyrene and poly(vinylalcohol) is disclosed at column 11, lines 14-58.
- the dielectric imaging element may comprise a dielectric film, a film support and conductive layers.
- the conductive layers include polymers such as quaternized polymers of vinylpyridine with aliphatic esters, polymers of polyacrylic acid salts with metallic coated polyester films, and the like.
- the conductive layers may be coated with various dielectric resins including styrenated acrylics.
- a polymeric complex is prepared from 4-vinylpyridine (a basic polymer) and polymethyl acrylic acid (an acidic polymer) to vie a significant amount of the ionized salt structure (Figure III).
- An electrophotographic recording member which contains a non-metallic base of high electrical resistivity, a coating on the base for increasing the electrical conductivity, the coating comprising gelatinous hydrated silicic acid and a hygroscopic hydrated inorganic salt, and a photoconductive stratum covering the coating.
- a photoconductive member comprising a support, a photoconductive layer constituted of an amorphous material comprising silicon atoms as a matrix and a barrier layer between the support and the photoconductive layer, the barrier layer comprising a first sub-layer constituted of an amorphous material comprising silicon atoms as a matrix and containing an impurity which controls the conductivity and a second sub-layer constituted of an electrically insulating material different from the amorphous material constituting the first sub-layer.
- US-A-4822705 and DE-A-3006740 are directed to electrophotographic imaging members comprising an electrically conductive substrate or a supporting substrate having an electrically conductive surface, respectively, and a charge blocking layer comprising a vinyl hydroxy ester polymer.
- DE-A 3006740 is directed to water-soluble vinyl hydroxy ester polymers.
- US-A-4822705 discloses vinyl hydroxy ester polymers containing ether groups.
- photosensitive members comprising a support having an electrically conductive charge injecting surface, a blocking layer and at least one photoconductive layer, exhibit deficiencies as electrophotographic imaging members.
- an electrophotographic imaging member comprising a supporting substrate having an electrically conductive surface, a charge blocking layer comprising a water insoluble high molecular weight hydroxy methacrylate polymer having a weight average molecular weight of at least 10,000, and at least one photoconductive layer, wherein said blocking layer has a surface resistivity greater than 10 10 ohms/square and wherein said water insoluble high molecular weight hydroxy methacrylate polymer is a polymeric reaction product of one or more monomers having the following structure: wherein
- This imaging member may be employed in an electrophotographic imaging process comprising providing the electrophotographic imaging member according to the present invention depositing a uniform electrostatic charge of at least 20 V/ ⁇ m on the imaging surface of said imaging member, exposing said imaging member to activating radiation in image configuration to form an electrostatic latent image, contacting said imaging surface with marking particles to form a marking particle image on said imaging surface in conformance with said electrostatic latent image, transferring said marking particle image to a recieving member, and repeating said depositing, exposing, contacting and transferring steps at least once.
- the present invention further provides a process for preparing an electrophotographic imaging member comprising providing a supporting substrate having an electrically conductive surface, forming a dry, continuous charge blocking layer comprising a water insoluble high molecular weight hydroxy methacrylate polymer having a weight average molecular weight of at least 10,000 and having a surface resistivity greater than 10 10 ohms/square on said electrically conductive surface, forming at least one photoconductive layer on said charge blocking layer, said water insoluble high molecular weight hydroxy methacrylate polymer being a polymeric reaction product of at least one monomer having the above structure, said electrically conductive surface comprising a component that is soluble in a solvent in which said water insoluble high molecular weight hydroxy methacrylate polymer having a weight average molecular weight of at least 10 000 is substantially insoluble, and applying at least one coating solution subsequent to forming said blocking layer, said coating solution comprising said solvent.
- the supporting substrate layer having an electrically conductive surface may comprise any suitable rigid or flexible member such as a flexible web or sheet.
- the supporting substrate layer having an electrically conductive surface may be opaque or substantially transparent, and may comprise numerous suitable materials having the required mechanical properties.
- it may comprise an underlying insulating support layer coated with a thin flexible electrically conductive layer, or merely a conductive layer having sufficient internal strength to support the electrophotoconductive layer.
- the electrically conductive layer may comprise the entire supporting substrate layer or merely be present as a component of the supporting substrate layer, for example, as a thin flexible coating on an underlying flexible support member.
- the electrically conductive layer may comprise any suitable electrically conductive organic or inorganic material. Typical electrically conductive layers including, for example, aluminum, titanium, nickel, chromium, brass, gold, stainless steel, carbon black, graphite, metalloids, cuprous iodide, indium tin oxide alloys and Lewis acid doped polypyrrole.
- the electrically conductive layer may be homogeneous or heterogeneous, e.g. conductive particles dispersed in a film forming binder.
- the ground plane should be continuous and at least monomolecular in thickness.
- the continuous conductive layer may vary in thickness over substantially wide ranges depending on the desired use of the electrophotoconductive member.
- the conductive layer can generally range, for example, in thicknesses of from about 5 nm (50 Angstrom units) for some materials to many centimeters.
- a minimum thickness of about 0.5 micrometer is preferred.
- the thickness of conductive layers may be between about 10 nm (100 Angstroms) to about 200 nm (2,000 Angstroms).
- the resistivity of the ground plane should be less than about 10 8 and more preferably 10 6 ohms/square for efficient photoreceptor discharge during repeated cycling. If an underlying flexible support layer is employed, it may be of any conventional material including metal and plastics.
- Typical underlying flexible support layers include insulating or non-conducting materials comprising various resins or mixtures thereof with conductive particles, such as metals and carbon black, known for this purpose including, for example, polyesters, polycarbonates, polyamides and polyurethanes.
- the coated or uncoated supporting substrate layer having an electrically conductive surface may be rigid or flexible and may have any number of different configurations such as, for example, a sheet, a cylinder, a scroll or an endless flexible belt.
- the flexible supporting substrate layer having an electrically conductive surface comprises an endless flexible belt of commercially available polyethylene terephthalate polyester coated with a thin flexible metal coating.
- the material selected for the ground plane should not be attacked by solvents ultimately selected for use with the subsequently applied blocking layer.
- the blocking layer solvent attacks the ground plane, it may leach out and/or physically dislodge hole injecting components from the ground plane into the blocking layer. In subsequent coating operations, these already migrated hole injection components in the blocking layer may further migrate into the charge generating layer or charge transporting layer from which dark discharge and low charge acceptance can occur. Since hole injection in the charge generating layer or charge transporting layer is cumulative with xerographic cycling, V 0 also decreases with cycling (V 0 cycle-down).
- a charge blocking layer is interposed between the conductive surface and the imaging layer.
- the imaging layer comprises at least one photoconductive layer. This blocking layer material traps positive charges.
- the charge blocking layer of this invention comprises a uniform, continuous, coherent blocking layer comprising the above defined hydroxy methacrylate polymer.
- the hydroxy methacrylate polymer used in the blocking layer according to this invention is a polymeric reaction product of one or more monomers having the following structure: wherein
- Typical divalent R aliphatic hydrocarbon groups include methylene, ethylidene, propylidene, isopropylidene, butylene, isobutylene.
- the polymeric reaction product of the vinyl hydroxy ester monomer having the above structure may be a homopolymer or copolymer.
- the copolymer may be a copolymer of 2 or more different monomers or polymer blocks.
- These monomers can be prepared to yield compositions having a high degree of purity without electrically deleterious catalyst and/or monomer residuals, and at very high weight average molecular weights (e.g. ⁇ 1,000,000).
- these polymers are soluble in lower alcohols having from 1 to 4 carbon atoms which enables the coating of these materials on top of organic or inorganic (generally alcohol insoluble) conductive layers without washing away the conductive layer with the alcohol coating solvent.
- organic coating solvents such as toluene, tetrahydrofuran, and chlorinated alkanes
- the hydroxy methacrylate polymer may e.g. be a homopolymer, a copolymer or a terpolymer.
- a preferred homopolymer is represented by the following formula: wherein
- Typical hydroxy methacrylate polymers include poly(4-hydroxybutyl)methacrylate, poly(3-hydroxypropyl)methacrylate, poly(2,3-dihydroxypropyl)methacrylate, poly(2,3,4-trihydroxybutyl)methacrylate,
- Poly(2-hydroxyethylmethacrylate) [P(HEMA)] is particularly insoluble in subsequently employed organic coating solvent.
- P(HPMA) exhibits some solubility in tetrahydrofuran when stirred in that solvent at room temperature for a prolonged time period (overnight). If the solvent evaporation is rapid, such as in a coating process normally employed to manufacture photoreceptors, then tetrahydrofuran solubility of the blocking layer polymer is an unlikely problem. Further, these polymers, particularly P(HEMA), attract about one weight percent water and retain much of the trapped water in a dense hydrogen bonding network even at low RH.
- the trapped water assists in the transport of photodischarged electrons through the blocking layer to the conductive layer and also assists in preventing electron trapping and V R cycle-up.
- each polymeric repeat unit not only maximizes intermolecular H-bonding in the form of OH-OH H-bonding and carbonyl (of the ester)-OH-bonding, but also allows for some intramolecular (5, 6 and 7 membered rings) H-bonding to maintain overall H-bonding density particularly in those blocking layer areas where intermolecular H-bonding is below the average, presumably because of conformationally unfavorable chain configurations.
- this intramolecular mode of H-bonding along with trapped water can maintain high H-bonding density which assists electron transport and completes photodischarge (low V R ). All of these properties contribute to enhanced photoreceptor electrical performance.
- the hydroxy methacrylate polymer may be crosslinked and uncrosslinked. If crosslinked, crosslinking may be effected by any suitable difunctional (or higher polyfunctionality) compound (usually a small molecule) that can react with hydroxyl groups at temperatures of less than about 135°C (where the substrate is polyethylene terephthalate) may be employed to crosslink the hydroxy ester polymers through the hydroxyl groups. Higher temperatures may be utilized if the substrate is not adversely softened at the reaction temperatures.
- Typical polyfunctionality compounds include diisocyanates such as toulenediisocyanate, methylenediisocyanate, isophoronediisocyanate and hexamethylenediisocyanate, blocked diisocyanates, polyfunctional aziridines such as XAMA-2, and polyfunctional epoxides such as 1,3-butadienediepoxide, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A diglycidyl ether, 1,4-divinylbenzene diepoxide, and difunctional aldehydes.
- diisocyanates such as toulenediisocyanate, methylenediisocyanate, isophoronediisocyanate and hexamethylenediisocyanate, blocked diisocyanates
- polyfunctional aziridines such as XAMA-2
- the difunctional aldehyde may have the following structure: wherein R"" is a divalent hydrocarbon or heteroaromatic unit or covalent bond.
- Typical R"" groups include methylene, ethylene, propylene, phenylene, biphenylene and pyridylene.
- Typical difunctional aldehydes include, for example, glutaraldehyde, glyoxal, 2,6-pyridinedicarboxaldehydes and terephthalaldehyde.
- the two OH groups in the hemiacetal linkages can further combine with two more OH groups in the polymer repeat units (or can remain as is, which is already a crosslink) to give acetal crosslinks with the elimination of water as illustrated below:
- the relative extent of hemiacetal and acetal crosslinking in dialdehyde crosslinked hydroxy ester polymer blocking layers is unknown. The higher the oven temperature during drying (solvent removal) of the blocking layer (up to a maximum of about 135°C.) and the longer the temperature is maintained at an elevated level (up to a practical maximum of about one hour) the more acetal linkages will form from the hemi-acetal linkages and other polymer repeat units and the higher will be the crosslink density.
- the monofunctional aldehydes (through acetal crosslinks only) can also be used to crosslink these hydroxy ester polymers but the crosslinking efficiency is less than that for the difunctional aldehyde because fewer crosslinks are formed per mole of monofunctional aldehyde versus difunctional aldehyde, all other factors being equal.
- Each time an acetal crosslink is formed two hydroxyl groups in the hydroxy ester polymer are consumed.
- a high crosslink density can consume many hydroxyl groups which in turn will significantly reduce the H-bonding density and electron transport capability of these blocking layers.
- crosslinking by hemiacetal crosslinks does not change the number of hydroxyl groups and is, therefore preferred.
- any other suitable technique may be utilized to crosslink hydroxy ester polymers through the hydroxyl groups.
- catalysts are employed with the polyfunctional compounds, care should be taken to wash out the catalyst and avoid catalytic residues in the final blocking layer which might adversely affect electrical properties.
- other permanent non-volatile residues which might interfere with the desired final electrical properties of the blocking layer should be avoided. This also ensures that there is no undesirable residue that could migrate out of the blocking layer or which could function as an electron trap in the blocking layer.
- hydroxy methacrylate polymers having a weight average molecular weight of at least about 10,000, the upper limit being limited by the viscosity necessary for processing.
- the weight average molecular weight is between about 20,000 and about 2,000,000.
- Optimum blocking layer performance is obtained when the weight average molecular weight is between about 100,000 and about 2,000,000.
- T g or glass transition temperature has no known effect on the ability of a hole blocking layer of this invention to function effectively.
- hydroxy methacrylate polymer poly(2-hydroxyethylmethacrylate) [P(HEMA)] which is represented by the following formula: wherein x represents sufficient repeat units for a molecular weight between about 20,000 and about 2,000,000.
- hydroxy methacrylate polymer is poly(2-hydroxypropylmethacrylate) [P(HPMA)] which is represented by the following formula: wherein x represents sufficient repeat units for a molecular weight between about 20,000 and about 2,000,000.
- Compounds used in this invention also include film forming copolymers of the above compounds with one or more copolymerizable vinyl or other suitable monomers.
- Typical copolymerizable vinyl monomers include acrylonitrile, methacrylonitrile, methylvinylether, and other alkyl and aryl vinyl ethers, styrene and substituted styrenes, ethylene, propylene, isobutylene, vinyl acetate, N,N-dimethylacrylamide, N-vinylpyrrolidone, 2, 3, and 4 vinylpyridine, various methacrylate and acrylate esters and vinyl chloride.
- Some monomers that undergo vinyl like polymerizations that are not vinyl monomers may also copolymerize with these hydroxy ester monomers. These include, for example, butadiene, isoprene, chloroprene, other conjugated diene monomers and the like. Generally, satisfactory results may be achieved with at least about 25 mole percent vinyl hydroxy ester repeat units in a copolymer.
- typical copolymers include those derived from 2-hydroxyethylmethacrylate and acrylonitrile; 2-hydroxyethylmethacrylate and N-vinylpyrrolidone, 2-hydroxypropylmethacrylate and N-vinylpyrrolidone, 2-hydroxyethylmethacrylate and 2-hydroxypropylmethacrylate.
- the polymers used in this invention may be blended with other compatible polymers.
- Compatible polymers are miscible with the hydroxy methacrylate polymer used in this invention.
- Typical miscible polymers include polyethyloxazoline (available from Dow Chemical Company) and any other sufficiently basic organic polymers capable of forming H-bonding complexes with hydroxyl groups sufficiently strong that phase separation is inhibited by the hydrogen bonding. It is believed that these basic organic polymers would include poly(ethylene and propylene) imines and other organic nitrogen containing basic polymers, but not poly(vinylpyridines).
- Polyethyloxyazoline may be represented by the following structural formula: wherein x is a number from 300 to 20,000.
- hydroxy methacrylate polymer in a blend with a polymer which does not contain any vinyl hydroxy ester polymer repeat units.
- a preferred blend concentration is one containing at least about 75 percent by weight of the hydroxy methacrylate polymer where the other polymer in the blend does not contain any vinyl hydroxy ester polymer repeat units.
- Optimum results are achieved with a concentration of 100 percent by weight of the hydroxy methacrylate polymer.
- the minimum amount of hydroxy methacrylate polymer to be blended can vary to some extent, depending upon what other repeat units are utilized.
- the hydroxy methacrylate polymers and copolymers used in this invention are generally miscible with each other. Moreover, if a vinyl hydroxy ester copolymer contains at least 50 mole percent of hydroxy ester repeat units then this copolymer will be miscible with another vinyl copolymer containing at least 50 mole percent of the hydroxyester in the first copolymer; or if the second copolymer contains at least 50 mole percent of the non-hydroxy repeat unit of the first copolymer. In some cases, the common repeat unit, in the second copolymer, can be as low as 33 mole percent and miscibility is achieved.
- Miscibility is defined as a nonhazy coating (after drying) of equal amounts of the two copolymers cast from common solution of the two copolymers in one solvent. These are all random (not blocked) copolymers.
- the vinyl hydroxy ester repeat unit content (expressed as weight percent) in a blend of two polymers, having a common vinyl hydroxy ester repeat unit content of at least 33 mole percent in each polymer is preferrably between about 0.10 and 99.9 weight percent.
- the specific composition selected for the ground plane will influence the thickness of the blocking layer selected.
- non-metallic or oxidizable charge injection ground plane materials require a thicker blocking layer.
- a photoreceptor utilizing a charge injecting ground plane layer containing copper iodide without an overlying blocking layer merely charges to about 3 volts/micrometer.
- the photoreceptor When a sufficiently thick blocking layer of this invention is applied over the ground plane layer containing copper iodide, the photoreceptor will charge to levels at least about 20 volts/micrometer. Charge levels of at least about 30 volts/micrometer are preferred with optimum results being achieved at levels of at least about 40 volts/micrometer. At levels below about 20 volts/micrometer, contrast potential decreases and lighter images cannot be developed with two-component dry xerographic developers.
- the blocking layer mixture is applied to the conductive surface of the supporting substrate.
- the blocking layer mixture used in this invention may be applied by any suitable conventional technique. Typical application techniques include e.g. spraying, dip coating, roll coating and wire wound rod coating. Coating compositions are usually applied with a solvent. Typical solvents include e.g. methanol, 1 -methoxy-2-hydroxypropane, tertiary butyl alcohol, water and mixtures of these solvents with other alcohol solvents and tetrahydrofuran. Choice of solvents depends upon the nature of the conductive layer upon which the barrier layer is applied and also on the properties of the polymers constituting the blocking layer.
- Appropriate solvents can, in general, be selected based on the known properties of the individual polymers, as is well known in the art. Mixtures of solvents may also be used, if desired.
- the proportion of solvent to be utilized varies with the type of coating technique to be employed, e.g., dip coating, spray coating, wire wound bar coating and roll coating, so that the viscosity and volatility of the coating mixture is adjusted to the type of coating technique utilized.
- the amount of solvent ranges from between about 99.8 percent by weight to about 90 percent by weight, based on the total weight of the coating composition.
- Typical combinations of specific solvents and polymers include, for example, poly(2-hydroxyethylmethacrylate) and 1-methoxy-2-hydroxypropane (Dowanol PM, available from Dow Chemical Co.) or tertiary butyl alcohol.
- Basic alcohols such as dimethylaminoethanol and acidic alcohols such as 2,2,2-trifluoroethanol also dissolve poly(2-hydroxyethylmethacrylate) significantly at room temperature but solvent neutrality is usually desirable to avoid interference with the ground plane or other layers affecting photoreceptor electrical performance.
- High boiling dipolar aprotic solvents such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone (DMF, DMAC and NMP respectively) also dissolve poly(2-hydroxyethylmethacrylate) extensively but are less desirable because total solvent removal from the coatings is more difficult to achieve due to the high boiling points of these solvents.
- DMF, DMAC and NMP N-methylpyrrolidone
- the limited solubility of high molecular weight hydroxy methacrylate polymers in common organic solvents is desirable because the deposition of subsequent device layers, such as the generator layer from solutions using common solvents such as toluene and tetrahydrofuran and the transport layer using common solvents such as methylene chloride, does not cause extensive solvent induced migration of these hydroxy ester and hydroxy amide vinyl polymers from the blocking layer into the layers overlying the blocking layer.
- the hydroxy methacrylate polymers and copolymers used in this invention have chemical structures containing hydroxyl groups which assist in retaining H 2 O through hydrogen bonding.
- the combination of the presence of hydroxyl groups and a small amount of water are believed to assist in enabling hole blocking layers to function effectively during charging and photo discharging negatively charged photoreceptors.
- the presence of the hydroxyl groups also provides the insolubility of the blocking layer towards the coating compositions deposited on top of the blocking layer such as the charge generating layer (applied with typical organic solvents such as toluene and tetrahydrofuran) and the charge transport layer (applied with typical organic solvents such as chlorinated alkane solvents, e.g.
- the blocking layer polymer is soluble in any of the organic solvents used in coating subsequent layers, the thickness uniformity and integrity thereof could be adversely affected because the organic solvents may wash the blocking layer material into the charge generating layer and/or charge transport layer. Thinner blocking layer or areas devoid of blocking layer material can result in very poor or even negligible device charge acceptance and high dark charge decay rate.
- the organic (non-hydroxyl containing) polymers described in US-A 4,410,614 would be too soluble in the above-mentioned organic solvents and, therefore, would not be suitable as blocking layers where the above-mentioned organic solvents are utilized with subsequently applied layers.
- organic solvents such as alcohols, glycol ethers and dipolar aprotic solvents can be utilized for the hydroxyl group containing polymeric blocking layer materials of this invention.
- the molecular weight of the hydroxy methacrylate polymer used in this invention is believed to be important in blocking layer applications because higher molecular weight polymers (all other things being equal) swell much more slowly than lower molecular weight polymers. Also, the use of higher molecular weight polymers in blocking layer applications allows the hydroxyl polymers to better encapsulate small molecules, such as water. Thus, longer chains of hydroxyl polymers can better encircle small water molecules and can better hydrogen bond these water molecules by providing more H-bonding sites per polymer chain when the polymer has a very high molecular weight.
- high molecular weight polymer chains can entangle (similar to spaghetti) with a larger number of contact sites than can low molecular weight polymer chains because the higher molecular weight polymer chains encompass or fill a larger volume of space.
- a contact site with the vinyl hydroxy ester of this invention means a hydrogen bonding site at another vinyl hydroxy ester site in the same polymer chain or with a neighbor chain. Therefore, longer (or higher MW) polymer chains will have more contact or entanglement sites with more neighbor chains creating a denser and tighter H-bonding network to encapsulate small H-bonding molecules such as water.
- Poly(2-hydroxylethylmethacylate) available from Scientific Polymer Products has a molecular weight of about 1.0 to 1.4 x 10 6 based on dilute solution measurements wherein the reduced viscosity is 1.8 to 2.0 g/dl.
- a high molecular weight poly(2-hydroxylethylmethacylate) blocking layer used in this invention is believed to have an intrinsic blocking layer advantage (because of a lower swelling rate) over the organic polymethacrylates described in US-A 4,410,614.
- the deposited coating is heated to drive out the solvent and form a solid continuous film.
- a drying temperature between 110°C and 135°C is preferred to minimize any residual solvent, to minimize any distortion to organic film substrates such as biaxially oriented polyethylene terephthalate.
- the temperature selected depends to some extent on the specific electrically conductive layer utilized and is limited by the temperature sensitivity of the substrate.
- the drying temperature may be maintained by any suitable technique such as ovens, forced air ovens or radiant heat lamps.
- the drying time depends upon the temperatures used. Thus, less time is required when higher temperatures are employed. Generally, increasing the drying time increases the amount of solvent removed. One may readily determine whether sufficient drying has occurred by chromatographic or gravimetric analysis.
- a typical treatment involves application of the coating with a half mil Bird coating bar followed by heating of the deposited coating at 130°C for 10 to 30 minutes.
- a dried blocking layer coating having a thickness between 0.05 micrometer and 8 micrometers on some conductive layers.
- the electrophotographic imaging member may show poor discharge characteristics and residual voltage build-up after erase during cycling.
- a thickness of less than 0.02 micrometer tends generally to result in pin holes as well as high dark decay and low charge acceptance due to non-uniformity of the thickness of different areas of the blocking layer.
- the preferred thickness range is between 0.3 micrometer and 1.5 micrometers with optimum blocking results being achieved with a thickness of between 0.8 micrometer and 1 micrometer on most conductive surfaces.
- the surface resistivity of the dry blocking layer used in the present invention is greater than 10 10 ohms/sq as measured at room temperature (25°C) and one atmosphere pressure under 40 percent relative humidity conditions. This minimum electrical resistivity prevents the blocking layer from becoming too conductive.
- Some of the blocking layer materials used in this invention can form a layer which also functions as an adhesive layer. However, if desired, an optional thin adhesive layer may be utilized between the relatively thick blocking layer and the charge generation layer. Any suitable adhesive material may be applied to the blocking layer.
- Typical adhesive materials include polyesters (e.g. 49000, available from E. I. duPont de Nemours & Co. and PE100 and PE200, available from Goodyear Tire & Rubber Co.) polyvinylbutyral, polyvinyl formal, polyvinylpyrolidone, polyamide, polyurethane, polyvinyl acetate, polyvinyl chloride, polyimide, polycarbonate, copolymers thereof and blends thereof.
- Adhesive layers having a thickness of between 0.005 micrometer to 0.2 micrometer.
- a preferred thickness is from 0.02 micrometer to 0.15 micrometer.
- Optimum results are achieved with a thickness of 0.03 micrometer (300 angstroms) to 0.12 micrometer from materials such as polyvinyl pyridine.
- the thickness of the adhesive layer exceeds 0.2 micrometer, residual voltage begins to cycle up excessively.
- Adhesive layers are especially useful for enhancing adhesion to charge generation layers containing materials, such as polyvinyl carbazole, which adhere poorly to vinyl hydroxy ester blocking layer polymers.
- Typical adhesive layer materials are those producing strong hydrogen bonds with vinyl hydroxy ester polymers, such as poly(4-vinylpyridine) and poly(2-vinylpyridine).
- Adhesive layers containing poly(4-vinylpyridine) form a hydrogen bonded polymeric complex with vinyl hydroxy ester blocking layer polymers which are believed to be unique adhesive compositions having solubility properties which allow the adhesive layer to also function as a solvent barrier layer.
- an acidic polymer and a basic polymer are sequentially coated onto a substrate instead of a neutral polymer and a basic polymer as accomplished in one embodiment of this invention.
- a polymeric salt complex forms in the device of US-A 4,082,551 whereas a hydrogen bonded polymeric complex is formed in one embodiment of this invention.
- the polymeric salt complex is a different composition of matter than the hydrogen bonded polymeric complex. More specifically, in US-A 4,082,551, a multilayer interlayer composition is disclosed comprising a lower layer (adjacent to the conductive layer) containing an acidic polymeric material (e.g.
- this multilayer-interlayer composition 0.4 micrometer layer of polyacrylic acid or methacrylic acid copolymer) and an upper layer (adjacent to the photogenerator layer) containing a basic polymeric material (e.g. 0.2 micrometer thick layer of a poly (2-vinylpyridine)-polymethylmethacrylate copolymer).
- a basic polymeric material e.g. 0.2 micrometer thick layer of a poly (2-vinylpyridine)-polymethylmethacrylate copolymer.
- an acid-base reaction product zone otherwise called a salt interlayer is generated.
- the total thickness of this complex multilayer interlayer composition can be between 0.2 micrometer to 1.0 micrometer and its function is to provide good adhesion between the conductive and photoconductive layers and to act as an electrical barrier blocking positive charge carrier injection (hole injection) from the conductive layer to the photoconductive layer.
- the instant invention embodiment utilizes, for example, a very thin (e.g. 0.06 micrometer) basic poly (4-vinylpyridine) adhesive enhancement component on top of a thicker (e.g. 0.2 to 1.5 micrometer) neutral vinyl hydroxy ester polymer hole blocking component.
- a very thin (e.g. 0.06 micrometer) basic poly (4-vinylpyridine) adhesive enhancement component on top of a thicker (e.g. 0.2 to 1.5 micrometer) neutral vinyl hydroxy ester polymer hole blocking component.
- the presence of poly (4-vinylpyridine) component is not required to obtain high charge levels, (which is the same as preventing hole injection from the conductive layer to the photoconductive layer) but as a hydrogen bonded polymeric complex with the top of the vinyl hydroxy ester polymer hole blocking component.
- the poly (4-vinylpyridine)-vinyl hydroxy ester polymer interface also performs the functions of any interface material beneath the photogenerator layer.
- the vinyl hydroxy ester hole blocking component polymer alone performs these functions but the poly (4-vinylpyridine) enhances adhesion to generator layers.
- the poly (4-vinylpyridine)-vinyl hydroxy ester polymer adhesive interface also functions as a solvent barrier layer towards the solvents used to coat the layers above, and also readily accepts and transports photodischarged electrons when these photodischarged electrons arrive at the poly (4-vinylpyridine)-vinyl hydroxy ester polymer interface from the photogenerator layer.
- a draw bar coated (12.7 ⁇ m (0.5 mil) bar gap) poly (4-vinylpyridine) adhesive layer composition can consist of a 0.6 weight percent solution of 0.12g poly (4-vinylpyridine) (Reillene 4200, available from Reilly Tar and Chemical Co.) in 17.89g isobutanol and 1.99g isopropanol.
- the drawbar coating process can be carried out on a previously dried vinyl hydroxy ester polymer blocking layer and the resulting poly (4-vinylpyridine) layer can similarly be dried for one hour under ambient conditions and then for on hour at 100°C in an air convection oven.
- the depth of penetration of the poly (4-vinylpyridine) polymer into the vinyl hydroxy ester polymer layer is largely a function of the solubility of the vinyl hydroxy ester polymer in the solvent (e.g. isobutanol-isopropanol mixture) used to apply the poly (4-vinylpyridine).
- Vinyl hydroxy ester polymers such as poly (2-hydroxypropylmethacrylate), which has significant solubility in the above solvent mixture would be expected to imbibe the poly (4-vinylpyridine) to a larger penetration depth versus poly (2-hydroxyethylmethacrylate) which has almost no solubility in the alcoholic solvent mixture. Consequently, different thicknesses of the poly (4-vinylpyridine)-vinyl hydroxy ester polymer interface will result.
- poly (4-vinylpyridine) If the poly (4-vinylpyridine) is coated too thickly, poly (4-vinylpyridine) can migrate into the generator layer during subsequent coating steps and cause VR cycle-up. Thus, too thick a coating of poly (4-vinylpyridine) can result in a surplus of poly (4-vinylpyridine) chains adjacent to each other and not adjacent to the vinyl hydroxy ester polymer chains where hydrogen bonding anchoring occurs. These unanchored poly (4-vinylpyridine) chains can migrate upward if solubilized by the solvents used to coat the subsequent layers above. Poly (4-vinylpyridine) hydrogen bonded to vinyl hydroxy ester polymer comprises an insoluble solvent barrier layer.
- an optimum coating concentration thickness of about 0.6 weight percent provides an extrapolated poly (4-vinylpyridine) coating thickness of 0.06 micrometer (not the poly (4-vinylpyridine)-vinyl hydroxy ester polymer interface thickness) which results in a totally hydrogen bonded poly (4-vinylpyridine) and an excellent adhesive solvent barrier interface layer.
- Such a poly (4-vinylpyridine)-vinyl hydroxy ester polymer interface layer of optimum poly (4-vinylpyridine) concentration in devices comprising a charge generation layer and a charge transport layer show little or no increase in V R during charge-erase cycles.
- a multilayer electrophotographic element comprising a conducting layer, a photoconductive layer, and a polymeric interlayer having a surface resistivity greater than about 10 12 ohm/sq between the conducting layer and the photoconductive layer.
- the interlayer comprises a blend of at least two distinct polymeric phases comprising: (a) a film forming water or alkali-water soluble polymer and (b) an electrically insulating, film forming, hydrophobic polymer.
- the conducting layer may contain cuprous iodide imbibed in a copolymeric binder of polymethylmethacrylate and polymethacrylic acid.
- a complex two phase hazy layer composed of a complex terpolymer (65 wt.
- poly-(methylacrylate-vinylidene chloride-itaconic acid) and poly-(vinylmethylether maleic anhydride) (35 wt. percent) is employed as an organic solvent barrier, an adhesive aid, and a hole blocking layer.
- type 3 polymers are described as polymers, including homopolymers and copolymers, comprising a backbone chain of repeating hydrocarbon units and acidic groups containing up to 10 carbon atoms as pendant side chains chemically bonded to the backbone chain.
- Useful acidic groups may be selected from the group consisting of sulfonic acids, carboxylic acids and carboxylic anhdrides.
- type 3 polymers have 3 or more repeat units in the backbone chain wherein an acid group must be contained in at least one of these repeat units. If an acid group is present (and it must be in all of the preferred type 3 copolymers (see bottom of column 4 and top of column 5 of US-A 3,932,179) the carboxylic acid group provides the water solubility or alkali solubility (pH 7 to 12) that the type 3 polymers must possess.
- the blocking layer polymers of the instant invention are generally not water soluble and nor do they need to be combined with a hydrophobic polymer.
- the preferred blocking layer of the instant invention generally contains a single component, that is, one polymer or copolymer, so it contains a very high concentration of hydroxyl groups (not incidental) and no acid groups for water solubility since water solubility is to be avoided.
- a satisfactory blocking layer of the instant invention generally comprises a lower concentration (as low as about 25 weight percent) of hydroxyl group containing repeat units, wherein the hydroxyl repeat unit content is diluted with non-hydroxyl containing repeat units in the same polymer (a copolymer) or in another polymer (a blend) or both.
- the lower hydroxyl repeat unit content is not incidental to obtaining improved photoreceptor cyclic electrical performance versus the same blocking layer composition wherein the hydroxyl repeat units have been omitted.
- the blocking layer of the instant invention with the neutral hydroxyl blocking layer polymers achieves very dense H-bonding with numerous hydroxyl groups that the 2 component, blocking layers in US-A 3,932,179 cannot achieve because the amount of H-bonding in U.S. 3,932,179 blocking layer polymers are many fewer (COOH---HOOC) per chain than in a blocking layer polymer such as P(HEMA).
- the hydroxyl polymers [e.g.
- P(HEMA)] have an O-H group in every repeat unit whereas the terpolymer in US-A 3,932,179 has many fewer COOH groups because the itaconic acid (or any other acid containing repeat unit in these terpolymers) is only 1 of 3 repeat units in the backbone chain. After dilution with the second polymer component, the COOH group content may further decrease and, therefore, so will the acid---acid H-bonding density which was low initially.
- the electrophotoconductive imaging member of this invention comprises a supporting substrate layer having an electrically conductive surface, a hydroxy methacrylate polymer containing blocking layer and a photoconductive imaging layer.
- the photoconductive layer may comprise any suitable photoconductive material well known in the art.
- the photoconductive layer may comprise, for example, a single layer of a homogeneous photoconductive material or photoconductive particles dispersed in a binder, or multiple layers such as a charge generating overcoated with a charge transport layer.
- the photoconductive layer may contain homogeneous, heterogeneous, inorganic or organic compositions.
- An electrophotographic imaging layer containing a heterogeneous composition is described in U.S. Patent 3,121,006 wherein finely divided particles of a photoconductive inorganic compound are dispersed in an electrically insulating organic resin binder.
- electrophotographic imaging layers include amorphous selenium, halogen doped amorphous selenium, amorphous selenium alloys e.g. including selenium arsenic, selenium tellurium, selenium arsenic antimony, and halogen doped selenium alloys and cadmium sulfide.
- these inorganic photoconductive materials are deposited as a relatively homogeneous layer.
- This invention is particularly desirable for electrophotographic imaging layers which comprise two electrically operative layers, a charge generating layer and a charge transport layer.
- Typical charge generating or photogenerating material may be employed as one of the two electrically operative layers in the multilayer photoconductor embodiment of this invention.
- Typical charge generating materials include metal free phthalocyanine described in U.S. Patent 3,357,989, metal phthalocyanines such as copper phthalocyanine, vanadyl phthalocyanine, selenium containing materials such as trigonal selenium, bisazo compounds, quinacridones, substituted 2,4-diaminotriazines disclosed in U.S. Patent 3,442,781, and polynuclear aromatic quinones available from Allied Chemical Corporation under the tradename Indofast Double Scarlet, Indofast Violet Lake B, Indofast Brilliant Scarlet and Indofast Orange.
- any suitable inactive resin binder material may be employed in the charge generator layer.
- Typical organic resinous binders include e.g. polycarbonates, acrylate polymers, vinyl polymers, cellulose polymers, polyesters, polysiloxanes, polyamides, polyurethanes and epoxies. Many organic resinous binders are disclosed, for example, in U.S. Patent 3,121,006 and U.S. Patent 4,439,507. Organic resinous polymers may be block, random or alternating copolymers.
- the photogenerating composition or pigment is present in the resinous binder composition in various amounts. When using an electrically inactive or insulating resin, it is essential that there be particle-to-particle contact between the photoconductive particles.
- the photoconductive material be present in an amount of at least about 15 percent by volume of the binder layer with no limit on the maximum amount of photoconductor in the binder layer.
- the matrix or binder comprises an active material, e.g. poly-N-vinylcarbazole
- the photoconductive material need only to comprise about 1 percent or less by volume of the binder layer with no limitation on the maximum amount of photoconductor in the binder layer.
- charge generator layers containing an electrically active matrix or binder such as polyvinyl carbazole or phenoxy resin [poly(hydroxyether)]
- an electrically active matrix or binder such as polyvinyl carbazole or phenoxy resin [poly(hydroxyether)
- from about 5 percent by volume to about 60 percent by volume of the photogenerating pigment is dispersed in about 40 percent by volume to about 95 percent by volume of binder, and preferably from about 7 percent to about 30 percent by volume of the photogenerating pigment is dispersed in from about 70 percent by volume to about 93 percent by volume of the binder
- the specific proportions selected also depend to some extent on the thickness of the generator layer.
- the thickness of the photogenerating binder layer is not particularly critical. Layer thicknesses from 0.05 micrometer to 40.0 micrometers have been found to be satisfactory.
- the photogenerating binder layer containing photoconductive compositions and/or pigments, and the resinous binder material preferably ranges in thickness of from 0.1 micrometer to 5.0 micrometers, and has an optimum thickness of from 0.3 micrometer to 3 micrometers for best light absorption and improved dark decay stability and mechanical properties.
- photoconductive layers include amorphous or alloys of selenium such as selenium-arsenic, selenium-tellurium-arsenic and selenium-tellurium.
- the active charge transport layer may comprise any suitable transparent organic polymer or non-polymeric material capable of supporting the injection of photo-generated holes and electrons from the charge generation layer and allowing the transport of these holes or electrons through the organic layer to selectively discharge the surface charge.
- the active charge transport layer not only serves to transport holes or electrons, but also protects the photoconductive layer from abrasion or chemical attack and therefore extends the operating life of the photoreceptor imaging member.
- the charge transport layer should exhibit negligible, if any, discharge when exposed to a wavelength of light useful in xerography, e.g. 400 to 800 nm (4000 Angstroms to 8000 Angstroms). Therefore, the charge transport layer is substantially transparent to radiation in a region in which the photoconductor is to be used.
- the active charge transport layer is a substantially non-photoconductive material which supports the injection of photogenerated holes or electrons from the generation layer.
- the active transport layer is normally transparent when exposure is effected through the active layer to ensure that most of the incident radiation is utilized by the underlying charge carrier generator layer for efficient photogeneration.
- imagewise exposure may be accomplished through the substrate with all light passing through the substrate.
- the active transport material need not be absorbing in the wavelength region of use.
- the charge transport layer in conjunction with the generation layer in the instant invention is a material which is an insulator to the extent that an electrostatic charge placed on the transport layer is not conductive in the absence of illumination, i.e. does not discharge at a rate sufficient to prevent the formation and retention of an electrostatic latent image thereon.
- the active charge transport layer may comprise an activating compound useful as an additive dispersed in electrically inactive polymeric materials making these materials electrically active. These compounds may be added to polymeric materials which are incapable of supporting the injection of photogenerated holes from the generation material and incapable of allowing the transport of these holes therethrough. This will convert the electrically inactive polymeric material to a material capable of supporting the injection of photogenerated holes from the generation material and capable of allowing the transport of these holes through the active layer in order to discharge the surface charge on the active layer.
- An especially preferred transport layer employed in one of the two electrically operative layers in the multilayer photoconductor embodiment of this invention comprises from 25 to 75 percent by weight of at least one charge transporting aromatic amine compound, and 75 to 25 percent by weight of a polymeric film forming resin in which the aromatic amine is soluble.
- Examples of charge transporting aromatic amines represented by the structural formulae above for charge transport layers capable of supporting the injection of photogenerated holes of a charge generating layer and transporting the holes through the charge transport layer include triphenylmethane, bis(4-diethylamine-2-methylphenyl) phenylmethane; 4'-4"-bis (diethylamino)-2",2"-dimethyltriphenyl-methane, N,N'-bis(alkylphenyl)-[1,1'-biphenyl]-4,4'-diamine wherein the alkyl is, for example, methyl, ethyl, propyl or n-butyl, N,N'-diphenyl-N,N'-bis(chlorophenyl)-[1,1'-biphenyl]-4,4'-diamine and N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphen
- Typical inactive resin binders soluble in methylene chloride include polycarbonate resin, polyvinylcarbazole, polyester, polyarylate, polystyrene, polyacrylate, polyether and polysulfone. Molecular weights can vary from 20,000 to 1,500,000.
- the preferred -electrically inactive resin materials are polycarbonate resins have a molecular weight from 20,000 to 100,000, more preferably from 50,000 to 100,000.
- the materials most preferred as the electrically inactive resin material is poly(4,4'-dipropylidene-diphenylene carbonate) with a molecular weight of from 35,000 to 40,000, available as Lexan 145 from General Electric Company; poly(4,4'-isopropylidene-diphenylene carbonate) with a molecular weight of from 40,000 to 45,000, available as Lexan 141 from the General Electric Company; a polycarbonate resin having a molecular weight of from 50,000 to 100,000, available as Makrolon from Maschinenfabricken Bayer A.G., a polycarbonate resin having a molecular weight of from 20,000 to 50,000 available as Merlon from Mobay Chemical Company and poly(4,4'-diphenyl-1,1-cyclohexane carbonate).
- Methylene chloride solvent is a particularly desirable component of the
- the activating compound which renders the electrically inactive polymeric material electrically active should be present in amounts of from 15 to 75 percent by weight.
- the charge transport layer may comprise any suitable electrically active charge transport polymer instead of a charge transport momomer dissolved or dispersed in an electrically inactive binder.
- Electrically active charge transport polymers employed as charge transport layers are described, for example in US-A 4,806,443, US-A 4,806,444, and US-A 4,818,650.
- any suitable and conventional technique may be utilized to mix and thereafter apply the charge transport layer coating mixture to the charge generating layer.
- Typical application techniques include spraying, dip coating, roll coating and wire wound rod coating. Drying of the deposited coating may be effected by any suitable conventional technique such as oven drying, infra red radiation drying or air drying. Generally, the thickness of the transport layer is between 5 micrometers to 100 micrometers, but thicknesses outside this range can also be used.
- the charge transport layer should be an insulator to the extent that the electrostatic charge placed on the charge transport layer is not conducted in the absence of illumination at a rate sufficient to prevent formation and retention of an electrostatic latent image thereon.
- the ratio of the thickness of the charge transport layer to the charge generator layer is preferably maintained from 2:1 to 200:1 and in some instances as great as 400:1.
- an overcoat layer may also be utilized to improve resistance to abrasion.
- a back coating may be applied to the side opposite the photoreceptor to provide flatness and/or abrasion resistance.
- These overcoating and backcoating layers may comprise organic polymers or inorganic polymers that are electrically insulating or slightly semi-conductive.
- the high molecular weight hydroxy methacrylate polymers used in this invention contain a hydroxyl group and carbonyl containing (ester) functionality in each repeat unit for blocking hole injection in the dark and transporting photodischarged electrons.
- the blocking layers of this invention form a solvent barrier layer to most of the commonly used coating solvents used to coat the layers overlying the blocking layer, e.g. is substantially insoluble in solvents such as toluene, tetrahydrofuran and methylene chloride.
- substantially insoluble as employed herein is defined as not sufficiently soluble to erode away a blocking layer in the time period that these solvents are in contact with the blocking layer so that high charge acceptance (V 0 ) and low (V R ) are retained in at least 200 consecutive imaging cycles.
- High V 0 is defined as at least 600 volts and low V R is defined as less than about 100 volts. It is electrically hole blocking during and after corotron charging prior to photodischarge. It is also more dark stable. This prevents ground plane hole injection and enables high V O charging initially and with repetitive cycling.
- the blocking layers used in this invention electrically accept photodischarged electrons from the generator layer and transport most or all of the accepted electrons to the ground plane to complete the discharge process.
- the electrostatographic imaging member of this invention allows photodischarge with low residual voltage during cycling under most ambient relative humidities. This enables total discharge within the xerographic time scale, and thus low V R initially and with repetitive cycling.
- the high molecular weight hydroxy methacrylate polymers used in this invention also afford sufficiently thick blocking layers in one or two spray passes from low viscosity, more concentrated solutions compared to other materials such as viscous poly(vinylalcohol) aqueous solutions which require numerous spray coating passes to build up blocking layer dry thickness to the desired level.
- the co-presence of the carbonyl functionality in each repeat unit enhances hydroxy polymer solubility (versus PVOH) to generally include lower alcohols and glycol ethers as optional spray solvents which make higher quality coatings more likely.
- the hydroxy polymers because of their dipole interactions (ester, amide) with the conductive layer polymers, enhance solid state adhesion at this interface compared to materials such as poly(vinylalcohol).
- a particularly surprising aspect of the high molecular weight blocking layers used in this invention is the lack of a strong dependence upon a large amount of H-bonded water to assist photodischarged electron injection and transport. Devices containing the high molecular weight blocking layers used in this invention can function independent of relative humidity without the need to provide an enclosed humidifier in the xerographic engine.
- the hole blocking capability of the various hydroxy methacrylate containing polymeric materials used as blocking layers were evaluated to establish the hole injecting capability of various non-metallic conductive layers. This was accomplished in this Control Example by measuring the first cycle surface voltage in the dark immediately after corotron charging ( ⁇ 0.2 seconds) photoreceptors not containing a hole blocking layer. This value was thereafter compared in the following Examples to the first cycle surface voltage obtained on an otherwise identical photoreceptor, but with the polymeric hole blocking layer included. The larger the difference [V o(1) with blocking layer V o(1) without blocking layer] in measured voltages under a constant set of electrical testing conditions for two photoreceptors having approximately the same layer thicknesses and same conductive layer, the larger is the intrinsic ability of the hole blocking layer material to block hole injection.
- the photoreceptors were fabricated without hole blocking layers in this Example and with hole blocking layers in all the remaining Examples.
- the conductive layers used in this evaluation consisted of a conductive material, usually (but not always) dispersed in an insulative polymeric binder, at a given loading level (>10 weight percent) sufficient to function as a conductive ground plane in discharging the photoreceptor over many consecutive charge-erase (discharge) cycles.
- CIT conductive composite film
- PVF polyvinylfluoride
- Tedlar® is polyvinylfluoride without carbon black dispersed in it (also available from,E.I. duPont De Nemours & Co.).
- the loading level of the conductive carbon black in carbon impregnated Tedlar® was between 10-25 weight percent, and the film physically and electrically resembles polyvinylfluoride loaded with 15 weight percent conductive carbon black Black Pearls 2000(available from Carbot Corp.).
- CIT has sufficiently conductive resistivity ( ⁇ 10 5 ohms/square), when measured with a four point probe, to be used successfully in numerous consecutive xerographic charge-discharge cycles.
- Polyvinylfluoride coatings with or without impregnated conductive carbon black, are chemically and physically resistant to common organic solvents (below 100°C) such as methylene chloride, tetrahydrofuran (THF), and toluene which are frequently used coating solvents for the other layers in these devices.
- common organic solvents such as methylene chloride, tetrahydrofuran (THF), and toluene which are frequently used coating solvents for the other layers in these devices.
- THF tetrahydrofuran
- the same PVF coatings are similarly solvent resistive to the more polar solvents such as lower alcohols (methanol, ethanol, isopropanol, n-butanol, sec. butanol and isobutanol) and ketones (acetone, methylethyl ketone and methyl isobutyl ketone) and water.
- Conductive layer carbon black formulations were developed for both drawbar and spray coating fabrication.
- the drawbar coated formulation consisted of 6.87 grams polyacrylic resin (Carboset® 514A, available from B.F. Goodrich Co. as a 70% solution in isopropanol) diluted with 20.4 grams isopropanol and 7.5 grams methylisobutyl ketone (MIBK). To this solution was added 0.94 grams of a conductive carbon black (Black Pearls® 2000 from Cabot Corp.) which was suspended with a Paint Shaker (Red Devil, Inc. Model 5100X) for 90 minutes.
- XAMA-2 a Carboset crosslinking agent available from Virginia Chemicals
- XAMA-2 a Carboset crosslinking agent available from Virginia Chemicals
- the resulting carbon black dispersion with crosslinking agent was drawbar coated (2 mil gap) using a Model P290 Gardner Labs, Inc. 8 1/2" x 11" drawbar coater now available from Paciific Scientific.
- This carbon black conductive layer dispersion was coated onto insulative polymeric substrates, such as duPont's Tedlar® or Mylar film or Melinex Polyester (ICI), and was then dried for one hour ambiently and one hour at 100-120°C. in an air convection oven.
- the dry thickness of the conductive layer was about 10 ⁇ 5 micrometers wherein the useful conductivity range was not a function of thickness.
- the resulting dried conductive layer was a crosslinked network wherein the conductive carbon black particles are trapped in the polymeric network.
- Carboset-carbon black conductive layers were also spray coated onto insulative polymeric substrates (e.g. Tedlar®, Mylar, Melinex®).
- the dispersion formulation used in spray coating was 80 grams Carboset 514A, 9.9 grams Black Pearls® 2000 conductive carbon black, 400 grams isopropanol and 1000 grams methylisobutyl ketone. All solvents used in this work were reagent grade.
- the above dispersion was roll milled with glass beads, for 64 hours. After decanting away the dispersion from beads, 8.4 grams XAMA-2 (the crosslinking agent) was added and magnetically stirred into the dispersion for 0.25 hour.
- the dispersion was sprayed using commercially available spray guns and equipment manufactured by Binks Manufacturing Company.
- a Binks Model 21 automatic spray gun was used in a Binks spray booth Model BF-4 with a type 42753 reciprocator.
- the Model 21 gun was equipped with a 638 fluid nozzle and a 63 PE air atomization nozzle.
- the fluid pressure was 27.6 kPa (4 psi) and the spray atomization pressure was 344.8 kPa (50 psi).
- the needle setting was at 1.5 turns and the spray fan angle at 0.75 turns. These settings were counted from the closed position.
- the spray gun was operated in an automatic mode and was traversed on a reciprocator while spraying from top to the bottom of the vertically positioned mandrel.
- the insulative polymeric substrates sprayed were tape mounted and rotated on a cylindrical aluminum mandrel positioned on a shaft connected to a turntable.
- the conductive dispersion was spray cycled three times with 1.5 minutes elapsing between passes.
- the coating was removed from the mandrel and was dried at 120°C. for 0.5 hour in an air convection oven.
- the crossllnked conductive layer (drawbar or spray coated) functions as a solvent barrier preventing erosion thereof by subsequently used coating compositions and their solvents. Because of the maintained layer integrity, proper xerographic charging and discharging results over thousands of cycles.
- a conductive carbon black and a polymeric resin in a 60/40 by volume solvent mixture of toluene and xylene was spray coated as received (without dilution) to give a 10-16 micrometer thick conductive layer that was sufficiently conductive to function as a ground plane for numerous consecutive xerographic charge-discharge cycles.
- the LE16610 black conductive olefinic flash primer (600 grams) was also redispersed ( ⁇ 0.5 hour.) using the previously described paint shaker (no steel shot or glass beads used). To spray a 12 micrometer thick (after drying) coating, four passes were applied according to the following set of spray parameters. Atomization Pressure (55psi) 379.2 kPa Fluid Pressure (6psi) 41.4 kPa Fan Angle 0.75 turns from closed position Fluid Opening 1.25 turns from closed position The previously described spray guns and associated equipment manufactured by the Binks Manufacturing Company were also used to spray this conductive layer composition on the same insulative polymeric substrates, mounted as previously described. The coated substrates were then ambiently air dried for 1-16 hours and at 90°C. in an air convection oven for at least 0.25 hour.
- a typical formulation for drawbar coating a conductive layer 20 grams of Polaroid ICP-117 polypyrrole-polymer complex at 10 weight percent in ethylacetate was diluted with 10 grams of the same solvent. This dispersion was drawbar coated [12.7 ⁇ m gap (0.5 mil gap)] with the previously described Gardner coating apparatus onto an insulative polymeric substrate, such as Mylar or Tedlar® from duPont. The coated conductive layer on the insulative polymeric substrate was transferred to an air convection oven maintained at 100-120°C. for .5 to 1.0 hour to evaporate the coating solvent. Polaroid ICP-117 polypyrrole-polymer complex is negatively charged and the polypyrrole fragments are positively charged.
- Conductive layers were drawbar and spray fabricated from commercially available copper iodide. The coatings prepared by drawbar fabrication will first be described.
- the clear filtrate was drawbar coated using a 6 mil bar gap and the coating was dried for one hour ambiently and then for at least 10 minutes in an air convection oven at 100°C.
- the dried coating thickness range from 20-100 nm (200-1000 Angstroms) as measured with an Auto EL elipsometer (Rudolph Research) at a wavelength of 632.8 nm (6328 Angstrom).
- the spray fabricated conductive copper iodide coatings are next described.
- To one liter of reagent grade butyronitrile solvent was added 23 grams of ultra pure cuprous iodide and the mixture was magnetically agitated at room temperature for two hours.
- the resulting solution [2.3 weight solute/volume solvent percent (w/v %)] was pressure filtered through a 0.2 micrometer Nuclepore filter at about 275.8 kPa (40 psi), and the filtrate was spray coated in 1 or 2 passes on either Mylar or Tedlar substrates.
- the transparent cuprous iodide coating ranged in thickness from 5 to 50 nm (50 to 500 Angstroms).
- the previously described spray guns and associated equipment manufactured by the Binks Manufacturing Company were used to spray this conductive layer composition, mounted as previously described.
- the sprayed conductive layers were allowed to ambiently dry for at least one hour and were then air convection oven dried for at least 0.5 hour.
- a mixed nitrile saturated solution comprising 515 ml butyronitrile, 345 ml acetonitrile (60:40 by volume) and 23.2 g cuprous iodide (2.7 w/v %), was filtered as described above and the filtrate was spray coated in 1 or 2 passes (1.5 minutes between passes) to give conductive layer coatings as described above for the single solvent spray solution. Similar drying conditions were employed but the spray parameters were slightly different: Atomization Pressure (55psi) 379.2 kPa Fluid Pressure (4psi) 27.6 kPa Fan Angle 0.5 turns from closed position Fluid Opening 0.5 turns from closed position. These spray fabricated Cul coatings were found to be equally useful to drawbar coated Cul conductive layers.
- the above conductive layers were fabricated (drawbar or sprayed) or used in the as received coated form (such as carbon impregnated Tedlar) as ground planes on which the other photoreceptor layers were fabricated.
- the vinyl hydroxy ester polymer blocking layers were deliberately omitted to establish the hole injection severity of representative conductive layer coatings.
- the devices fabricated in this example did not contain an adhesive layer between the conductive layer and the photogenerator layers except when the conductive layer was binderless cuprous iodide. In this case delamination occurred between the cuprous iodide layer and the photogenerator layer with routine handling of the completed device.
- a very thin ( ⁇ 0.1 micrometer) poly(4-vinylpyridine) [P(4VPy)] adhesive layer was drawbar coated between the conductive layer and photogenerator layer.
- a typical poly(4 vinylpyridine) adhesive layer formulation consisted of a 0.6 weight percent solution of 0.12g Reillene® 4200 (Reilly Tar & Chemical Co.) in 17.89g isobutanol and 1.99g isopropanol. After applying this solution as a coating with a 12.7 ⁇ m (0.5 mil) drawbar gap, using the previously described Gardner coating apparatus, the coating was dried ambiently for one hour and then for one hour at 100°C. in an air convection oven (standard conditions).
- the poly(4 vinylpyridine) adhesive layer was drawbar fabricated in devices of subsequent examples, the above formulation, coating procedure and drying conditions were used unless otherwise indicated.
- a charge generator layer mixture was prepared by forming a dispersion of about 8.57g trigonal selenium particles doped with about 1-2 percent by weight sodium hydroxide, 16.72g polyvinylcarbazole, 4.93g N,N'-bis-(3"-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine, 100.55g tetrahydrofuran and 100.55g toluene. This dispersion was then diluted with an equal weight of toluene. The diluted dispersion was next agitated on a wrist shaker for about 5 minutes immediately prior to coating the conductive layer with a 25.4 ⁇ m (1 mil) drawbar gap. The charge generator coating was next dried for one hour at room temperature and for one hour at 1O0°C in an air convection oven. The dry thickness of the photogenerator layer thus obtained was about 1.0 ⁇ 0.3 micrometer in this and subsequent Examples.
- a charge transport layer coating mixture was prepared by mixing about 2.8g N,N'-bis(3"methylphenyl)-[1,1'biphenyl]-4,4"diamine, 4.2g polycarbonate resin (Makrolon® 5705, available from Wegricken Bayer A.G.) and 40g methylene chloride. This mixture was coated with a 127 ⁇ m (5 mil) drawbar gap onto the photogenerator layer. The transport layer coating was dried at room temperature for one hour, and then through an incremental heating cycle from 50 to 100°C. in 0.50 to 0.75 hour and finally at 110°C. for at least 10 minutes. The dry thickness of the charge transport layers in this and subsequent Examples was about 25-30 micrometers as determined with a type DS No. 11033 Permoscope. The completed devices were electrically charge-erase cycled using either an ambient scanner or an environmental scanner which are described below.
- the ambient cyclic scanner used to obtain the charge-erase cycling results was equipped with a single wire corotron (5 cm wide) set to deposit 9 x 10 -8 coulombs/cm 2 of charge on the surface of these experimental devices.
- the devices were grounded to an aluminum drum having a 76.5 cm circumference and the drum was rotated at a speed of 12 rpm giving a surface speed of 152.4 cm (6 inches) per second.
- the devices were discharged (erased) with a tungsten white light source emitted through a plexiglass light pipe and the intensity of the erase lamp was varied from 2 to 10X the amount of light required to discharge the device down to twice the asymptotic residual voltage.
- the entire xerographic simulation discharge and erase was carried out in a light tight enclosure.
- the environmental cyclic scanner used to obtain charge-erase cycling results under various environmental conditions was equipped with a single wire corotron (5 cm wide) set to deposit 9 x 10 -8 coulombs/cm 2 (or 14 x -10 -8 coulombs/cm 2 in some cases) of charge on the surface of these experimental devices.
- the devices were grounded to an aluminum drum having a 63.1 cm circumference and the drum was rotated at a speed of 20 rpm to produce a surface speed of 210.8 cm (8.3 inches) per second.
- the devices were discharged (erased) with a short arc white light source emitted through a fiber optic light pipe.
- the entire xerographic simulation (charge and erase) was carried out in an environmentally controlled light tight chamber.
- This Example demonstrates the selection of a preferred poly(4 vinylpyridine) [P(4VPy)] thickness (coating concentration) as an adhesive layer between poly(2-hydroxyethylmethacrylate) [P(HEMA)] blocking layers and generator layers containing trigonal selenium particles dispersed in polyvinyl carbazole (PVK).
- P(4VPy) adhesive layer is too thick or is bulk mixed into the P(HEMA) to give phase separated (immiscible) blocking layer compositions, V R cycle-up is immediately apparent (see following TABLE B).
- devices IIc & IId described in detail below, which have no P(4VPy) adhesive layer, have no significant V R cycle-up.
- the V R cycle-up in both the layered and mixed devices arises to some extent from P(4VPy) migration into the generator and/or transport layer during coating of these layers.
- the migrated P(4VPy) polymer in the generator and/or transport layer traps holes during device discharge thus causing V R cycle-up.
- the P(4VPy) migration is more prevalent when larger amounts (thicker layers) of P(4VPy) are present in the adhesive composition. Since P(4VPy) is methylene chloride soluble, considerable migration of P(4VPy) occurs during coating of the transport layer. Some of the P(4VPy) directly in contact with P(HEMA) will not migrate because the strong H-bonding interaction between the P(4VPy) and the P(HEMA) will anchor the former.
- the second V R cycle-up mechanism which occurs primarily in devices having a mixed P(4VPy)-P(HEMA) layer, results from electron trapping in these blocking layers during discharge.
- Vinyl Hydroxy ester polymer blocking layers possess extensive hydroxyl-hydroxyl H-bonding which structurally resembles water in its H-bonded state. It is presumed that photodischarged electrons migrate through the hydroxy ester polymer blocking layer medium (plus the small amount of H-bonded water contained therein) much like electrons migrate through water.
- P(4VPy) H-bonds to hydroxyl groups in the P(4VPy)-P(HEMA) blocking layers many of the hydroxyl-hydroxyl H-bonding sites are disrupted.
- V R cycle-up is about twice as large in the mixed P(4VPy)-P(HEMA) blocking layer devices (IIe-IIg) versus the layered devices (IIa-IIb).
- the charge-erase cycling data were obtained at ambient RH using the ambient scanner for 12000 cycles.
- the Carboset 514A conductive layers on Tedlar® substrates were drawbar coated for devices IIa and IIc and were spray coated for devices IIe-IIg.
- the formulations, coating conditions and drying conditions for both fabrication methods were described in Example I.
- the as received carbon impregnated Tedlar® (CIT) bulk conductive substrates were drawbar coated with the P(HEMA) blocking layer solution.
- the P(HEMA) (0.6 gram) was coated from a 6 weight percent solution in methanol (9.4 grams). The same formulation was used to coat the thick P(4VPy) adhesive layer in devices IIa and IIb and a 12.7 ⁇ m (0.5 mil) drawbar gap was used for both layers. Standard drying conditions were employed for both layers wherein standard drying conditions are one hour at ambient conditions and one hour at 100°C in an air convection oven.
- the P(HEMA) used in the above TABLE B was obtain from Polysciences, Inc. (see Example IV) and the P(4VPy) from the Reilly Tar & Chemical Co. as Reillene® 4200.
- the blocking layer polymer poly(2-hydroxypropylmethacryate) P(HPMA)
- the blocking layer polymer was coated onto smooth 2" x 2" glass substrates from a 90:10 by weight solvent mixture of isobutanol:isopropanol at four concentrations, 1.2, 3.6, 6.0 and 8.4 weight percent, after drying as described above (standard conditions) and the dry thickness of the coatings was measured with a Dektak® surface profile measuring system.
- the Dektak® is available from Sloan Technology Corp.
- the P(4VPy) adhesive layer thickness was systematically increased on top of a P(HEMA) blocking layer of constant (0.8-1.0 micrometer) thickness.
- the P(HEMA) used in this segment of this Example was the very high molecular weight variety available from Scientific Polymer Products, Inc. (Example IV) which was coated and dried as described above for the lower molecular weight P(HEMA).
- Dowanol® PM was used as the coating solvent again at 6 weight percent as previously described.
- Dowanol® PM available from Dow Chemical Co., is a glycol methyl ether systematically named as 1-methoxy-2-hydroxypropane.
- the P(4VPy) adhesive layers were coated and dried as previously described in Example I formulated in the 90:10 by weight isobutanol:isopropanol solvent mixture.
- the dry P(4VPy) thicknesses were estimated from the Dektak® generated P(HPMA) calibration curve. For concentrations less than 1.2 weight percent and greater than 8.4 weight percent, thicknesses were estimated from the Dektak® curve extrapolated at either end.
- P(4VPy) concentrations of 0.0, 0.3, 0.6, 1.2, 2.5, 5.0 and 10.0 weight percent correspond to the estimated adhesive layer thicknesses in the following table.
- the precise thickness of the P(4VPy) adhesive layer is unimportant so long as the coating concentration and drawbar gap can be correlated to an electrically useful charge-erase window.
- the bulk conductive substrate, carbon impregnated Tedlar (CIT) was used for all the devices in this adhesive layer thickness study. All devices electrically tested in this Example (both tables) contain charge generator and transport layers formulated, coated and dried as described in Example I. The charge-erase cycling data in the following table were obtained at ambient RH using the environmental scanner for 200 cycles.
- Device No. P(4VPy) Adhesive Layer V O(1) V O(200) V R(1) V R(200) Approx.
- Adhesive layer thicknesses between 0.03 and 0.12 micrometer, corresponding to a P(4VPy) concentration range of 0.3 to 1.2 weight percent, provide a useful adhesive layer thickness window wherein sufficient adhesion is provided for routine handling without delamination, and acceptable charge-erase cycling data is obtained.
- the initial charge acceptance which is maintained in all devices for 200 cycles and in most of the devices for 12000 cycles, indicates the 0.8-1.0 micrometer P(HEMA) hole blocking layer is minimizing charge injection from the carbon based conductive layers.
- the latter charge at a much lower level (Example I) when the blocking layer is omitted in an otherwise identical device.
- This example illustrates the use of P(4VPy) and P(2VPy), available from Reilly Tar & Chemical Co. as Reillane® 4200 and 2200 respectively, as a combined hole blocking and adhesive layer in an attempt to eliminate the need for a vinyl hydroxy ester polymer blocking layer.
- This Example will first describe a device set in which all the layers were drawbar coated, and then a second device set in which all the layers were spray coated. Both device sets were fabricated on carbon black conductive layers but in the second set a metallic conductive layer (titanized Mylar) was also included to evaluate the impact of the conductive layer on charge-erase electrical performance.
- the adhesive/blocking layers of the first device set were formulated, drawbar coated and dried as described in the following table.
- the THF used to coat the charge generator layer may channel through the top P(4VPy) layer to dissolve the underlying P(2VPy) which would promote interlayer mixing between the two P(VPy) layers and also between the P(VPy) layers and the PVK generator layer binder.
- the V R cycle-up reflects the presence of hole trapping P(2VPy) in the charge active layers.
- the vinyl hydroxy ester polymer is not necessary to prevent conductive layer hole injection in these mixed P(VPy) isomer blocking layer devices (V o values are large), its presence is necessary to help anchor the P(VPy) isomers through hydrogen bonding to the P(HEMA) hydroxyl groups. This anchoring reduces or substantially eliminates [when a thin layer of P(VPy) isomer is used] hole trapping P(VPy) migration into the charge active layers during coating thereof and so V R cycle-up decreases.
- P(4VPy) anchoring mechanism by P(HEMA) is described in Example II and also applies to P(2VPy), but probably to a lesser extent because H-bonding to P(2VPy) is more sterically hindered than to P(4VPy). Thus, the P(2VPy) is more free to migrate during coating than is the P(4VPy) because of solubility and H-bonding considerations.
- the totally sprayed second device set of this Example will next be described.
- the Carboset 514A carbon black conductive layer was formulated, spray fabricated onto Mylar and dried as described in Example I, and the titanized Mylar was used as received from E.I. duPont de Nemours & Co. These substrate-conductive layers were next spray coated with a dilute solution (0.9 weight percent) of either P(VPy) isomer in mixed alcohol solvents.
- the spray solution was formulated by mixing 6.86 grams of P(4VPy) or P(2VPy) with 663.6 grams isobutanol and 79.6 grams isopropanol in an amber quart bottle which was roll milled for 2-5 hours to obtain a solution.
- This blocking layer solution was sprayed using commercially available spray guns and equipment manufactured by Binks Manufacturing Co.
- the Binks Model 21 automatic spray gun was used in the Binks spray booth Model BF-4 with a type 42753 reciprocator.
- the Model 21 gun was equipped with a 63B fluid nozzle and a 63PE air atomization nozzle
- the fluid pressure was 27.6 kPa (4 psi) and the spray atomization pressure was 379.2 kPa (55 psi).
- the needle setting was at 0.75 turns and the spray fan angle at 0.50 turns counted from the closed position.
- the spray gun was operated in an automatic mode and was traversed on a reciprocator while spraying from the top to the bottom of the vertically placed mandrel.
- the substrate-conductive layer sheets to be sprayed were tape mounted and rotated on a cylindrical aluminum mandrel positioned on a shaft connected to a turntable.
- the blocking layers solution was spray cycled with two or four passes with 1.5 minutes elapsing between passes. Finally, the coating was removed from the mandrel and was dried at 120°C for 5 minutes in an air convection oven.
- the dry thickness of these sprayed P(VPy) blocking layers is estimated for the two pass layer to be between 0.5 to 1.5 micrometer and for the four pass blocking layer to be between 1.5 to 2.5 micrometer.
- the generator layer mixture was then formulated for spray fabrication using the masterbatch formulation described in Example I.
- To 200 grams of the generator layer masterbatch in a one quart amber glass bottle was added 258 grams of toluene and 258 grams of THF and this mixture was magnetically stirred for 3-4 hours prior to spray coating.
- the dispersion (3.65 weight percent total solids) was sprayed using the previously described Binks equipment.
- the fluid pressure was 27.6 kPa (4 psi) and the spray atomization pressure was 379.2 kPa (55 psi).
- the needle setting was at 0.75 turns and the spray fan angle at 0.5 turns counted from the closed position.
- the spray gun was operated in an automatic mode and was traversed on a reciprocator while spraying from the top to bottom of the vertically placed mandrel.
- the partially fabricated devices consisting of a substrate, conductive layer and blocking layer were tape mounted and rotated on a cylindrical aluminum mandrel positioned on a shaft connected to a turntable.
- the generator layer dispersion was spray cycled in three passes with 1.5 minutes elapsing between passes. Finally, the coating was removed from the mandrel and was dried at 120°C for 5 minutes in an air convection oven.
- the generator layer dry thickness was estimated to be between 0.4 and 2.0 micrometers in thickness.
- the charge transport layer composition was formulated and sprayed.
- a one gallon amber glass bottle was charged with 88 grams N,N'bis-(3'-methylphenyl)-[1,1'-biphenyl]-4,4'diamine, 132 grams polycarbonate resin (Merlon M-39, available from Mobay Chemical Co., Inc.), 2640 grams of methylene chloride and 1760 grams of 1,1,2-trichloroethane.
- the resulting solution was sampled for spray fabrication using the previously described spray equipment manufacture by Binks Manufacturing Co.
- the fluid pressure was 55.2 kPa (8 psi) and the spray atomization pressure was 379.2 kPa (55 psi).
- the needle setting was at 0.75 turns and the spray fan angle at 0.5 turns counted from the closed position.
- the spray gun was operated in an automatic mode and was traversed on a reciprocator while spraying from the top to the bottom of the vertically placed mandrel.
- the partial devices with the last coated generator layer on the surface were tape mounted and rotated on a cylindrical aluminum mandrel position on a shaft connected to a turntable.
- the above transport layer solution was sprayed in five passes with 1.5 minutes elapsing between passes. Finally, the coating was removed from the mandrel and was dried at 120°C for 10 minutes in an air convection oven.
- the transport layer dry thickness was found to be between 20-30 micrometers using the previously described Dektak® (Example II) procedure.
- the P(VPy) blocking layers in these carbon black conductive layer devices have inferior blocking capability compared to other blocking layers containing vinyl hydroxy ester polymers alone (IIc & IId), vinyl hydroxy ester polymers with P(4VPy) adhesive layers (IIa & IIb), and mixed P(VPy) isomers without vinyl hydroxy ester polymers present (IIIa-IIId).
- the improved blocking capability (higher V o versus the same devices without a blocking layer in Example I) of the aforementioned three blocking layer compositions indicates these compositions are more effective in preventing conductive layer components from mixing upward into the generator and/or transport layers during coating of these layer.
- the solvent barrier properties of these compositions contribute significantly to blocking conductive layer mixing and its effect, i.e.
- V O cycle-down in the above devices dictates the severity of the interlayer mixing and V O charge depletion.
- the absence of the possibility of conductive layer component mixing in the titanium conductive layer devices appears electrically as higher V O(1) with retention thereof with cycling.
- the presence of the natural titanium oxide blocking layer on this metallic conductive layer also contributes to the prevention of V O cycle-down.
- the absence of V O cycle-down in the titanium devices provides indirect evidence that carbon black conductive layers are deleteriously involved in causing V O cycle-down in otherwise identical devices.
- V R cycle-up in the device set of the above TABLE G occurs extensively in all the P(2VPy) blocking layers devices (IIIh-IIIj) independent of conductive layer composition.
- the most likely cause of V R cycle-up originates in the ease of P(2VPy) migration into the generator and/or transport layers during solvent coating of these layers.
- hole trapping occurs with V R cycle-up similar to that observed in drawbar coated devices (IIIa-IIId) which also contain P(2VPy).
- the absence of extensive V R cycle-up in the P(4VPy) blocking layer devices (IIIe-IIIg) may reflect a lesser degree of P(4VPy) migration into the upper (CGL, CTL) layers during coating thereof.
- the P(4VPy) is not as effective a hole trapping material as is the P(2VPy), so migrated P(4VPy) is less effective than migrated P(2VPy) in forming trap sites.
- the V R in IIIe-IIIg therefore cycles up much less. Since none of the devices in this Example delaminated during routine fabrication and electrical testing procedures, the interfacial adhesion at all interfaces is sufficient to enable photoreceptor use. Overall, the electrical cycling properties of the devices in this Example illustrate two important desirable properties of a photoreceptor blocking layer: (1) The blocking layer should co-function, as much as possible, as a barrier layer to subsequently applied coating compositions so that it becomes a protective coating for non-metallic conductive layers.
- the blocking layer itself should be insoluble in subsequently applied coating compositions so that it can maintain barrier properties [as described in (1)] and so that the blocking layer material itself does not migrate into the CGL and CTL during coating thereof.
- the insolubility of the vinyl hydroxy ester or vinyl hydroxy amide polymer blocking layers of this application arises from dense intermolecular hydrogen bonding.
- NMR analysis (C 13 ) of the 0.654 intrinsic viscosity P(HEMA) in concentrated (7-8 weight percent) DMSO-d 6 solution between 297°K- 307°K provided information concerning the tacticity of the polymer.
- the NMR spectrometer was a Bruker AM 360 equipped with a 5 mm QNP probe at a carbon frequency of 90.5 MHz.
- the C 13 spectrum was obtained using inverse grated decoupling with 30 seconds recycle delay between acquisitions to ensure quantitative integrals for all carbon nuclei
- P(HEMA) tacticities were previously studied using C 13 -NMR wherein P(HEMA) obtained from a radical solution polymerization had a similar triad distribution, i.e. 58 percent syndiotactic, 42 percent heterotactic ⁇ 1 percent isotactic [D.E. Gregonis, G.A. Russell, J.D. Andrade and A.C. deVisser, Polymer 19 , 1279-1284 (1978)].
- the triad content for the 0.654 intrinsic viscosity P(HEMA) is typical of a radically polymerized polymer.
- the low molecular weight P(HEMA) was prepared using a modification of the procedure described in a Czechoslovakian Patent [Chem. Abstr. 99 (2): 14003j (1982); Czech CS200433B, No. 30, 1982] wherein the solvent was changed from methyl Cellosolve to tertiary butylalcohol and the crosslinking agent was omitted.
- the coagulated polymer was vacuum filtered on a coarse frit funnel and the filtered polymer was slurried at room temperature with 300 ml reagent grade tetrahydrofuran. The slurried polymer was filtered as before and dried overnight in a vacuum oven on a sheet of Mylar at 60°C at 0.5 mm Hg. The dried water-white polymer yield was 31.25g (78.1 percent of theory) and had an intrinsic viscosity of 0.272 dl/g. This material was used without further purification to drawbar coat blocking layers.
- the blocking layer compositions were formulated as follows. Device No.
- Example II The devices were evaluated at ambient (27 %) and low ( ⁇ 5%) relative humidities using the ambient cyclic scanner.
- Blocking layer thicknesses were obtained from the Dektak generated calibration curve In Example II.
- blocking layer thickness range of 0.2 to 1.0 micrometer generally acceptable V R and V R cycle-up were observed in this 4000 cycle test at both low and ambient RH.
- blocking layer thicknesses of greater than about 2 micrometers may be too thick to enable complete photodischarge (V R cycle-up) at ambient or low RH in the presence or absence of an adhesive layer.
- the presence of an adhesive layer in the 0.2 - 1.0 micrometer range is electrically negligible except at 1.0 micrometer where a significant V R cycle-up at low RH (35 to 70 volts) occurred in 4,000 cycles.
- Example II Illustrated in this Example is the use of two different molecular weights of P(HEMA) as blocking layers on a conductive polypyrrole based polymer (ICP-117 from Polaroid Corp.).
- the conductive polymer dispersion was formulated, drawbar coated and dried as described in Example I on either insulative polymer substrates, Mylar or Tedlar®.
- the P(HEMA) blocking layer solution were prepared with three coating solvents using a 12.7 ⁇ m (0.5 mil) bar gap unless otherwise indicated. Thicknesses for methanol and Dowanol PM coated P(HEMA) blocking layers were projected from the dry thickness/concentration curve described in Example II for P(HEMA).
- Vd and Vg Devices (Vd and Vg) containing 0.8 - 1.0 micrometer of high molecular weight P(HEMA) blocking layers afford xerographically useful high V O values confirming the strong solvent barrier properties attributable to high molecular weight P(HEMA).
- V O values decreased indicating even the high molecular weight P(HEMA) blocking layer, when less than about 0.8 micrometer, is not as strong a solvent barrier on ICP-177 conductive layers as compared to its effectiveness as a barrier on chemically inert CIT conductive layers.
- This conductive layer composition has an aggressive affinity for subsequently used organic coating solvents.
- V R cycle-up in devices Vc and Vh implies a charge trapping mechanism is simultaneously operative with the charge depletion mechanism.
- the precise cause of the trapping mechanism is unclear, but it is possible that some of the P(HEMA) is moved up into the CGL and/or CTL during coating thereof.
- some of the P(HEMA) may be uprooted and carried along into these layers resulting in charge trapping and the observed V R cycle-up.
- the first device set of this Example illustrates the use of poly(2-hydroxypropylmethacrylate), P(HPMA), as a blocking layer on the carbon based conductive layer crosslinked Carboset 514.
- Tedlar® substrates were used for all four devices wherein devices Vla, Vlb and Vld contained spray coated conductive layers and device VIc a drawbar coated conductive layer.
- the Carboset 514A was formulated, coated and dried as described in Example I.
- the P(HPMA) (available from Polysciences, Inc.) blocking layers were coated [drawbar gap 12.7 ⁇ m (0.5 mil)] from a 90/10 by weight solvent mixture of isobutanol/isopropanol at concentrations of 1.2, 3.6, 6.0 and 8.4 weight percent to give dry coating thicknesses of 0.1-0.3, 0.5-0.7, 0.8-1.0 and 1.3-1.5 micrometers, respectively. The thicknesses were projected from the dry thickness/concentration curve developed for this polymer in Example II. After drying the blocking layer at standard conditions (Example II), a P(4VPy) adhesive layer was coated [drawbar gap 12.7 ⁇ m (0.5 mil)] from 0.4-0.6 weight percent solutions.
- the adhesive layer solvent composition and drying conditions were the same as used for the blocking layer coating.
- Charge generator and transport layers were sequentially applied as described in Example I.
- Charge-erase electrical cycling data were obtained with the ambient cyclic scanner at ambient RH (38-40 percent) for 12,000 cycles. In one case, the device tested for 12,000 cycles was dark rested at least overnight and was then retested for 45,000 continuous cycles.
- V O (1 and 12,000) obtained in the above blocking layer thickness range indicates significant blocking of positive charge (hole) injection from the conductive layer at ambient RH prior to photodischarging.
- Example I a similar device without a blocking and adhesive layer charged to a V O of only 460 volts.
- Device Vla having a thin blocking layer, was the only device that showed VR cycle-up. Because Carboset 514 conductive layers are less chemically inert than CIT conductive layers, mixing of conductive components from the Carboset 514 conductive layer into the thin blocking layer disrupts hydroxyl-hydroxyl H-bonding sufficiently to cause photodischarged electron trapping to occur with each successive xerographic cycle and thus V R cycle-up occurs.
- Vlc having a blocking layer sufficiently thick to prevent interlayer mixing, cycled flat for the first 12,000 cycles and then exhibited a 33 percent V O cycle-down in the subsequent 45,000 charge-erase cycling test.
- the magnitude of the V O cycle-down is common for such a severe cycling test especially with ozone buildup in the non-ventilated scanner chamber. With dark resting for 24 hours, V O recovered to approximately the same voltage (Vo) as was found prior to the 45,000 cycling test.
- P(4VPy) adhesive layer compositions were formulated, coated and dried as previously described in this Example. Both blocking and adhesive layer thicknesses were estimated from the previously described dry thickness concentration curve (Example II). Charge generator and transport layers were formulated, coated and dried as described in Example I. The devices were tested with the ambient cyclic scanner for 200 cycles. Device No.
- both P(HPMA) and P(HEMA) provide satisfactory hole blocking capability in 200 cycles at both ambient and low RH.
- V O remains significantly higher that same device in Example I without a blocking layer.
- the P(HPMA) blocking layer device develops considerable V R cycle-up at low RH testing conditions.
- V R cycle-up is probably not related to interlayer mixing because it did not occur at ambient RH when the same device was tested. More likely, the V R cycle-up is probably related to a decreased water level in P(HPMA) versus P(HEMA) blocking layers. More trapped water, although not a large amount, in P(HEMA) versus P(HPMA) assists in enhancing the hydrogen bonding density by bridging hydrophobic (low H-bonding density areas) gaps. Also, hydroxyl H-bonding density in P(HEMA) is probably larger than in P(HPMA) because of methyl steric hindrance to some of the H-bonding sites in P(HPMA).
- This Example illustrates the use of P(HEMA) blocking layers at two different molecular weights and three different thicknesses.
- the blocking layers were drawbar coated on LE1661O carbon black conductive layers which were formulated and sprayed (on Tedlar® substrates) and dried as described in Example I.
- three of the high molecular weight P(HEMA) devices were crosslinked with glutaraldehyde, added as a 25 weight percent aqueous solution just prior to drawbar coating the blocking layers. Crosslinking then proceeded after solvent evaporation during air convection oven drying of the coating at 120°C for one hour.
- the charged molar ratio of glutaraldehyde to P(HEMA) repeat units in the blocking layer coating solution was held constant at 1:3.
- Each aldehyde group in the glutaraldehyde molecule is capable of crosslinking two P(HEMA) hydroxyl groups through formation of acetal linkages.
- the simultaneous elimination of water at 120°C drives the crosslinking reaction in the absence of acidic catalysis.
- Crosslinking was confirmed to have occurred at the above stoichiometry and curing conditions in a separate experiment in which the crosslinked coating, which as scraped from a glass slide, was totally insoluble in Dowanol PM.
- the P(HEMA) blocking layers were formulated at 3.6 and 6.0 weight percent in methanol and Dowanol PM, and at 2 weight percent in t -butanol. Standard drying conditions were used when crosslinking agent was not added.
- the impact of glutaraldehyde crosslinking is most noticeable in the thinner (0.5-0.7 vs. 0.8-1.0 micrometer) blocking layer devices when high molecular weight P(HEMA) is used as the hole blocking polymer.
- the crosslinked device Vllc charges 155 volts higher than its sister device (Vlld) which has not been crosslinked.
- the crosslinked P(HEMA) blocking layer is better able to function as a barrier layer and so more effectively blocks upward migration and mixing of LE16610 conductive layer components into the generator and transport layers during coating thereof.
- crosslinking the P(HEMA) blocking layer reduces V R cycle-up because hole trapping P(HEMA) remains fixed in place in the crosslinked blocking layer.
- the P(HEMA) cannot be carried upwards by migrating conductive materials because the crosslinked P(HEMA) layer itself significantly decreases the extent of conductive material migration which is the primary cause of trapping and V R cycle-up.
- the high molecular weight P(HEMA) blocking layer thickness is increased to 0.8-1.0 micrometer, electrical effects due to crosslinking (VIIe vs VIIf or VIIi) become indiscernable.
- the increased P(HEMA) blocking layer thickness alone is sufficient to impart solvent resistance and barrier (to mixing) properties making P(HEMA) crosslinking unnecessary in thicker blocking layers.
- V R cycle-up Devices which contain uncrosslinked high molecular weight P(HEMA) blocking layers of 0.5-0.7 micrometer thickness (VIId and VIIh) differ significantly in V R cycle-up.
- the larger V R cycle-up for VIIh versus VIId implies that the change in blocking layer coating solvent to the more organic Dowanol PM (from methanol) is at least, in part, responsible for the trapping and V R cycle-up.
- the propylene glycol methyl ether (Dowanol PM) solvent is more effective than methanol in penetrating and uprooting LE1661O conductive layer components. This solvent induced conductive layer component migration into the blocking layer disrupts and decreases the hydroxyl-hydroxyl hydrogen bonding density in the blocking layer.
- Identical devices VIId and VIIh differ markedly in V O (by 340 volts). Since the only formulation variation in the two devices is the change in blocking layer coating solvents, this change must in part be responsible for the V O decrease. The lower boiling methanol cast coatings apparently loose their solvent too rapidly so that thin and thick areas arise because of insufficient polymer flow. The thin areas of such a non-uniform blocking layer become prime sites for hole injection from the conductive layer. However, blocking layer thinness is not a sufficient explanation for low V O since 0.2 micrometer methanol cast P(HEMA) blocking layers are sufficiently thick to block hole injection (Example IV) on carbon impregnated Tedlar® bulk conductive substrates.
- t-butanol coated P(HEMA) blocking layers simply indicates the presence of an overall thinner blocking layer which must exist because of the high molecular weight P(HEMA) solubility limitation (2 weight percent) in t-butanol, as described in Example V.
- the significantly thinner t -butanol coated P(HEMA) blocking layer even if uniform in thickness, is porous to charge injection from the LE16610 conductive layer.
- This Example illustrates the use of both P(HEMA) and P(HPMA) as vinyl hydroxy ester polymer blocking layers of various thickneses on strongly injecting binderless cuprous iodide conductive layer.
- the conductive layers for all the devices in this Example were drawbar coated as described in Example I on Tedlar® substrates.
- the moderate viscosity P(HEMA) [ ⁇ ] 0.506 was coated from 6 and 10 weight percent methanol solutions using 12.7 and 127 ⁇ m (0.5 and 5.0 mil) drawbar gaps to give 0.8-1.0 and 8.5 micrometer blocking layers, respectively.
- the very thick P(HEMA) blocking layer was measured directly with the Dektak® stylus whereas the other thicknesses were estimated from the dry thickness - concentration curve developed for P(HPMA) as described in Example II.
- a nominally thin (0.4-0.6 weight percent ⁇ 0.06 micrometer) P(4VPy) adhesive layer was drawbar coated (12.7 ⁇ m (0.5 mil) bar gap] and dried as described in previous examples. The charge generator and transport layers were next applied as described in Example I.
- the very thick P(HEMA) blocking layer device Vllld has a nominally low V R at cycling onset and cycles up to only 174 volts in 12,000 cycles.
- the relatively small V R cycle-up level observed for the 8.5 micrometer P(HEMA) blocking layer device implies that the natural abundance of electron trapping sites in P(HEMA) is small versus other much thinner blocking layer polymers used in this embodiment, and that the P(HEMA) is less likely to migrate into the CGL and CTL where hole trapping can occur.
- the P(HEMA) blocking layers were coated using standard 3.6, 6.0 and 2.0 weight percent solutions in Dowanol PM and t -butanol as indicated in the following table.
- two devices contained blocking layers which contained glutaraldehyde crosslinked P(HEMA) in which the mole ratio of P(HEMA) repeat units to moles of glutaraldehyde was about 3:1. Since no adhesive layer was applied in these devices, the charge generator and transport layers were next applied as described in Example I.
- copolymers derived from the hole blocking P(HEMA) repeat units and the P(4VPy) adhesive repeat units were to combine in one coated layer both properties (blocking and adhesive), thus eliminating the need to coat a separate adhesive layer in these devices on non-metallic conductive layers. Consequently, no separate P(4VPy) adhesive layer was coated.
- the bulk conductive substrate, carbon impregnated Tedlar® (CIT) was used as the conductive layer.
- the three copolymers were coated [drawbar gap 12.7 ⁇ m (0.5 mil)] from 6 weight percent t -butanol solutions to give blocking layers of 0.8-1.0 micrometer thickness after drying at standard conditions.
- the 64:36 composition copolymer was coated from 2.0 and 3.6 weight percent t -butanol solutions to give 0.2-0.4 and 0.5-0.7 micrometer blocking layers.
- the blocking layer thicknesses were estimated from the previously described (Example II) dry thickness-concentration curve developed for P(HPMA).
- Charge generator and transport layers were next applied as described in Example I, and the charge-erase cycling data were obtained at ambient RH using the ambient scanner.
- An alternative or simultaneous mechanism for increased V R cycle up with increased P(4-VPy) content in the copolymer invokes blocking layer copolymer migration into the generator layer during coating of the CGL and/or CTL. Migration would be expected to increase with increasing P(4-VPy) content in the copolymer because the homopolymer P(4VPy) is soluble in the CGL coating solvent, methylene chloride. Thus, the copolymer richest in P(4-VPy) content, the 40:60 copolymer, would be most likely to migrate into the CGL and CTL while coating the latter. Although the three copolymers failed to dissolve at the one weight percent level in methylene chloride, some low finite copolymer concentration does dissolve and migrate.
- V R cycle-up Very low polymer solubilities and migration levels (ppm) are sufficient to cause electrically noticeable hole trapping in the generator layer as V R cycle-up. Further inspection of the above table indicates that even the thinnest 0.2-0.4 micrometer blocking layer provides good blocking of hole injection on the solvent resistant CIT conductive layers (versus the same device in Example I without a blocking layer). Similar results were found for devices containing 100 percent P(HEMA) blocking layers on CIT (Example IV) at both ambient and low RH.
- the second electrical data set of this Example describes charge-erase cycling of devices containing three blocking layer thicknesses of the 64:36 copolymer on CIT conductive layers.
- Three concentrations of the 64:36 copolymer in t -butanol (1.8, 3.6 and 14.4 weight percent) were drawbar coated [12.7 ⁇ m (0.5 mil) gap] to give estimated blocking layer thickness ranges of 0.2-0.4, 0.5-0.7 and 2.0-2.4 micrometers. Since no P(4VPy) adhesive layer was coated, charge generator and transport layers were applied as described in Example I.
- the completed devices were charge-erase cycled with the ambient scanner at both ambient and low RH. Device No.
- the adhesion of the P(HEMA-4VPy) copolymer blocking layers to the t -Se/PVK generator layers in this Example was comparable to that obtained with a separate P(4VPy) adhesive layer applied on top of a high molecular weight P(HEMA) blocking layer.
- the P(4VPy) repeat units in the P(HEMA-4VPy) blocking layer provide interfacial adhesion to the t -Se/PVK generator layer via a similar mechanism as does the separately coated P(4VPy) adhesive layer while still providing useful cyclic electrical properties, provided that the blocking layer is not too thick.
- This Example illustrates the preparation of four additional P(HEMA) copolymers containing repeat units of poly(2-hydroxypropylmethacrylate) [P(HPMA)] and poly(N-vinylpyrrolidone) [P(VP)] along with the charge-erase blocking layer evaluation of two of the copolymer compositions on carbon impregnated Tedlar® (CIT).
- the blocking layer copolymers were formulated in Dowanol PM at concentrations of 3.6 and 6.0 weight percent to give approximate thicknesses of 0.5-0.7 and 0.8-1.0 micrometer based on the P(HPMA) dry thickness-concentration curve in Example II. Blocking layers were drawbar coated [12.7 ⁇ m (0.5 mil) gap] and then dried at standard conditions.
- Example IX the incentive for using these P(HEMA) copolymers as blocking layers was to improve adhesion to the PVK based generator layer, so no separate P(4VPy) adhesive layer was applied.
- the charge generator and transport layers were formulated, coated and dried as described in Example I.
- the four copolymers were prepared according to the following procedure.
- the HEMA (Mhoromer BM-920) and HPMA (Mhoromer BM-955) monomers were first passed three times through a De-Hibit 100 column, as described in Example IV, to remove the hydroquinone based polymerization inhibitors.
- the N-vinylpyrrolidone (98 percent from Aldrich Chem.) monomer ( ⁇ 16 grams) was dissolved in 250 ml toluene and 15 ml of deionized water was added. The two liquid layers were shaken in a separatory funnel thus transferring the 0.1 percent KOH polymerization inhibitor from the monomer-toluene phase to the aqueous phase. This extraction was repeated a second time and the toluene layer was separated and rotoevaporated under reduced pressure at 50°C to yield monomer suitable for copolymerization.
- Copolymers derived from monomer combinations of HEMA-HPMA, HEMA-VP and HPMA-VP were previously prepared in bulk polymerizations frequently containing low added levels of difunctional vinyl monomer for crosslinking, with and without polymerization initiators, at 60-70°C in 12 hours. This work is described in U.S. 3,721,657 with the resulting polymer hydrogels being suitable for contact lens and membrane applications. This procedure was modified using tertiary butyl alcohol as a polymerization solvent and AIBN (at 0.3 mole percent based on total monomer weight charge) as the polymerization initiator without an added crosslinking agent. Alcohol soluble vinyl hydroxy ester based polymeric materials were sought for solvent coating the blocking layer.
- Crosslinking agents may be added to the already formed polymer in the coating solution used to coat the blocking layer composition. Crosslinking then occurs in a convection air oven at 100 - 120°C while the solvent was removed from the blocking layer coating.
- Crosslinking of P(HEMA) or P(HPMA) repeat units in copolymer blocking layer applications may be achieved through formation of acetal groups, when using a dialdehyde (such as glutaraldehyde).
- Example IV To a 1 liter 3 neck round bottom flask, equipped as described in Example IV, was charged the pure HEMA monomer and the comonomer (M2 is HPMA or VP) and the AIBN polymerization initiator. The polymerization solution was magnetically stirred with argon passed through the solution throughout the polymerization. After cooling the reaction vessel contents, the polymer solution or dispersion, was coagulated into toluene (9.0 - 9.5 x the volume of polymer solution) and the precipitated polymer was filtered on a coarse glass frit using vacuum. The solvent moist copolymer was next dried at 50-70°C overnight in a vacuum oven at ⁇ 0.5 mm Hg.
- M2 is HPMA or VP
- the integrated peak areas for the methylene group attached to the carboxyl in P(HEMA) and P(HPMA) repeat units were compared to the integrated peak area for the methylene group attached to the carbonyl in vinylpyrrolidone at 31 ppm to give the copolymer compositions in the above table. All four copolymers were practically insoluble in methylene chloride at room temperature ( ⁇ 0.02 weight percent solubility at a 0.1 weight percent initial concentration) and in toluene ( ⁇ 0.1 weight percent solubility) as well.
- the poly(ethloxyazoline) used was P(EOx) 500, having a Mw of 500,000 from Dow Chemical.
- Two conductive layers were used: ICP-117 polypyrrole and carbon impregnated Tedlar (CIT).
- the ICP-117 conductive layers were drawbar coated from the Polaroid provided dispersions, diluted to 5 weight percent, onto Tedlar® [38.1 ⁇ m (1.5 mil) gap] and Mylar [12.7 ⁇ m (0.5 mil) gap].
- the blocking layer formulations were drawbar coated [12.7 ⁇ m (0.5 mil) bar gap] from approximately 6.0 and 3.6 weight percent methanol solutions to give dry thicknesses of 0.8-1.0 and 0.5-0.7 micrometer. The thicknesses were estimated from the Dektak® generated curve for P(HPMA) in Example II. After combining the two blocking layer polymers in the appropriate quantities, methanol was added and the mixture was warmed gently (40-50°C.) to give the desired solids level solution. Standard blocking layer drying conditions (Example II) were applied and then the charge generator and transport layers were applied as described in Example I. Since the incentive for using these P(EOx)-P(HEMA) hydrogen bonding complexes as blocking layers was to improve adhesion to the PVK generator layers, the P(4VPy) adhesive layer was omitted.
- Blocking Layer Compositions Device No. Repeat Unit Mole Percent Weight Percent Weight Percent Weight Percent P(EOx)-P(HEMA) P(EOx)-P(HEMA) Polymers in Methanol XIa 54-46 47-53 6.0 XIb 43-57 36-64 5.8 XIc 30-70 25-75 5.7 Xld 16-84 13-87 6.0 XIe 8.5-91.5 7-93 6.0 XIf 7-93 5.5-94.5 3.6 PEOx is known to compatibilize normally incompatible hydroxylic polymers such as the Bakelite Phenoxy resins (Keskkula, H., and Paul, D.R.
- V R cycle-up At a blocking layer thickness of 0.8-1.0 micrometer and at ambient (20-24%) RH, devices XIa-XIe show a well defined trend in V R cycle-up. As the P(EOx) content decreases, the V R cycle-up also decreases. This implies that some hole trapping P(EOx), when present as a blocking layer component in larger quantities, is not sufficiently anchored (by means of H-bonding) in the blocking layer and migrates into the generator and/or transport layer during coating of these layers. The migrated P(EOx) then traps holes in these layers which, as an ongoing process with charge-erase cycling, appears as V R cycle-up.
- P(EOx) is soluble in tetrahydrofuran and methylene chloride, two of the three subsequently used coating solvents, P(EOx) migration during coating of the generator and transport layers is a likely occurrence.
- P(EOx) content is further reduced to ⁇ 10 mole percent of the polymeric repeat units present in an 0.8-1.0 micrometer thick blocking layer (device XIe)
- very little P(EOx) migration occurs as evidenced by the small V R cycle-up, even at low RH.
- device XId which has 16 mole percent P(EOx), has high residual voltages at low RH, but not at ambient RH.
- the initial charging levels for devices XIe and XIf on the ICP-117 polypyrrole conductive layer indicate this conductive layer to be more hole injecting versus carbon impregnated Tedlar®, which is used in all the other devices. Inspection of the V O levels for the same devices containing no blocking layer in Example I verifies the above hole injection capability. Furthermore, decreasing blocking layer thickness (XIf vs. XIe) decreases V O implying insufficient blocking layer thickness over the high areas of the ICP-117 conductive layer. A second mechanism contributing to V O decline which cannot be precluded with the ICP-117 devices involves migration and mixing of conductive layer components into the CGL and/or CTL during coating thereof.
- the CIT conductive layer devices (XIa-XId) are more uniform and more resistant to coating solvent effects so V O levels are higher and remain higher with cycling.
- the P(EOx)-P(HEMA) hydrogen bonding polymeric complexes used as blocking layer materials in this Example provide sufficient interfacial adhesion to maintain device integrity during routine handling procedures.
- This Example illustrates the use of 0.8-1.0 micrometer thick blocking layers of P(HEMA) copolymers and the P(HEMA)-P(EOx) hydrogen bonded polymeric complex.
- the blocking layers were drawbar coated [12.7 ⁇ m (0.5 mil) gap] onto strongly injecting spray coated cuprous iodide ground planes wherein the cuprous iodide coatings were spray fabricated as described in Example I.
- Mylar polyester (E.I. duPont de Nemours & Co.) substrates were used for all devices.
- the 6 weight percent blocking layer coating solutions consisted of 0.6 gram polymer(s) in 9.4 grams of methanol or Dowanol PM solvent.
- Blocking layer thickness was estimated from the dry thickness-concentration calibration curve and standard drying conditions were used for all coated layers as in Examples I and II. No adhesive layer was necessary at the blocking layer-generator layer interface since device integrity was maintained during routine handling and electrical evaluation.
- the charge generator and transport layers were applied as described in Example I, and the ambient cyclic scanner was employed to obtain charge-erase cycling data at ambient RH. The following charge-erase data in TABLE Y were obtained. Device No .
- Blocking Layer Composition V O(1) V O(200) V R(1) V R(200) Mole % Repeat Units XIIa P(HEMA-HPMA) Copolymer 81-19 770 880 10 16 XIIb P(HEMA-HPMA) Copolymer 59-41 840 850 15 36 XIIc P(HEMA-VP) Copolymer 88-12 770 940 27 32 XIId P(HEMA-4VPy) Copolymer 64-36 860 960 31 70 XIIe P(HEMA)-P(EOx) Complex 93-7 910 930 26 50 The preparation and analyses of the above blocking layer compositions were provided in Example X (for XIIa, XIIb and XIIc), Example IX (for XIId) and Example XI (for XIIe).
- This Example illustrates the use of blocking layers derived from the 64:36 (repeat unit molar ratio) HEMA-4VPy copolymer, and various blend compositions (H-bonded polymeric complexes) of P(HEMA) and P(EOx) on conductive carbon black layers of olefinic flash primer LE16610 (Red Spot Paint & Varnish Co.).
- the conductive layers were formulated, sprayed and dried on Mylar substrates as described in Example I. All blocking layer compositions were coated from methanol solution at 3.6 and 6.0 weight percent to give 0.5-0.7 and 0.8-1.0 micrometer thicknesses, respectively.
- the blocking layer thicknesses were estimated based on a previously described (Example II) dry thickness-coating concentration curve and standard drying conditions were employed. An adhesive layer at the blocking layer-generator layer interface was not needed since the devices maintained their integrity during routine handling and electrical testing. Charge generator and transport layers were applied as described in Example I. Both ambient and low RH charge-erase testing conditions were used to evaluate these devices using the ambient cyclic scanner. The electrical results for the devices containing the 64:36 P(HEMA-4VPy) copolymer blocking layer are indicated in the following table. Device No.
- the charge-erase results for the thin P(HEMA-4VPy) copolymer blocking layer (device XIIIa) indicates that hole injection (low V O value) is in fact more severe than it is in the same device without a blocking layer (Example I). This implies mixing of hole conductive components from the conductive layer into the generator and/or transport layers during coating of these layers.
- V O(1 & 200) increases to levels greater than that found for the same device without a blocking layer.
- the solvent barrier properties of the 64:36 P(HEMA-4VPy) copolymer blocking layer to subsequently used coating compositions are only sufficient when the blocking layer is at least 0.8-1.0 micrometer.
- V R cycling behavior for 200 cycles at ambient RH (device XIIIb) is very similar to device XIId (Example XII) and device IXg (Example IX) indicating the conductive layer composition has no significant electrical effect on V R cycle-up provided that the 64:36 HEMA-P(4VPy) copolymer blocking layer is sufficiently thick on the LE16610 conductive layer.
- the ambient V R cycle-up as described in Example IX for blocking layers of the same composition, implies blocking layer copolymer migration into the generator and/or transport layers during coating of these layers. Hole trapping then occurs in these layers with the observed associated electrical effect of V R cycle-up.
- the more severe V R cycle-up at low RH implies the simultaneous presence of a second trapping mechanism, which is the same blocking layer electron trapping mechanism described in Example IX.
- the P(HEMA)-P(EOx) polymer blend blocking layers were formulated, drawbar coated and dried as described in Example XI. Since all the blocking layers were coated from 6 weight percent methanol solutions, the thicknesses were estimated at 0.8-1.0 micrometer based on the aforementioned calibration curve (Example II). The charge-erase electrical results were obtained with the ambient cyclic scanner at ambient and low RH and are indicated in the following table. Device No.
- V R cycle-up trend with increasing P(EOx) content in the blocking layer parallels that observed in Example XI, on CIT conductive substrates, for similar reasons.
- Device XIIIf was charge-erase cycled in the tabulated sequence of the above table wherein V R cycle-up in each cycling sequence was for the most part recoverable at the beginning of the next cycling sequence. The time between each cycle sequence was 2-3 days as a matter of convenience, but the actual V R recovery time may be considerably less.
- a P(HEMA) blocking layer, a Se particles dispersed in poly (vinylbutyral) [PVB] CGL, and an N,N'-bis-(3"-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine in polycarbonate (Merlon 50, available from Mobay Chemical Co.) CTL were all sprayed on top of the conductive titanium coated substrate. No adhesive layers were employed at the blocking layer - CGL interface. The spray fabrication of each layer will first be described starting with the P(HEMA) blocking layer.
- a 2 weight percent P(HEMA) blocking layer solution was prepared by dissolving 12 grams of P(HEMA) in 588 grams of propylene glycol methyl ether (Dowanol PM, available from Dow Chemical Co.) solvent at room temperature. This solution was sprayed using commercially available spray guns and equipment manufactured by Binks Manufacturing Company.
- a Model 77 electrostatic spray gun was used in the non-electrostatic mode with a horizontal recipricator. The Model 77 gun was equipped with a N63A fluid nozzle and a N63PC air atomization nozzle. The fluid pressure was 15.2 kPa (2.2 psi) and the spray atomization pressure was 206.9 kPa (30psi).
- the fan angle air supply was opened until a reading of 4814 dm 3 (170 cu. ft) per hour was obtained on the air flow meter in the atomization line.
- the spray gun was operated automatically and was traversed [1.16 m/min (3.8 ft./min.)] on the reciprocator while spraying from right to left onto the horizontally postioned mandrel.
- the conductive substrate titanium coated Mylar from E.I.
- duPont de Nemours & Co. sheets to be sprayed were tape mounted onto the cyclindrical aluminum mandrel which was rotated at a speed of 120 rpm.
- the P(HEMA) blocking layer was sprayed in one pass and the solvent moist coating was rotated for 3 or 4 minutes after completing the spray process in order to flash off the bulk of the solvent.
- the partially dried coating was dismounted from the mandrel and dried at 110°C for 20 minutes in an air convection oven.
- the dry thickness of this P(HEMA) blocking layer was approximately 0.8-1.0 micrometer determined from the weight applied to a known area.
- the generator layer (CGL) dispersion was prepared by roll milling trigonal selenium (13.6grams), poly (vinylbutyral) [B-76, available from Monsanto] (3.5 grams) and the solvent mixture comprising 72.2 grams toluene and 24.2 grams tetrahydrofuran for several days (2-5 days).
- This concentrated dispersion (15 weight percent solids) contained approximately 45 volume percent trigonal selenium and 55 volume percent poly (vinylbutyral).
- the concentrated dispersion Prior to spraying , was diluted with a 1:1 (by weight) mixture of toluene and THF (141.8 grams each) which was manually swirled for 1-2 minutes to give a sprayable 4.3 weight percent total solids dispersion.
- the above dispersion was sprayed using commercially available spray guns and equipment manufactured by Binks Manufactruring Company.
- a Model 21 non-electrostatic spray gun was used with a horizontal recipricator.
- the Model 21 gun was equipped with a 63A fluid nozzle and a 63PE air atomization nozzle.
- the fluid pressure was 5 psi with the needle valve in the fluid nozzle set at 0.75 turns from the closed position.
- the spray atomization pressure was set as follows. With the fan angle closed to 0° and the air supply at 7646 dm 3 /h (270 cu. ft./hour), the fan angle air supply was opened until a reading of 8778 dm 3 /h (310 cu.
- the transport layer (CTL) solution was formulated at 5 weight percent solids as follows. Polycarbonate (Merlon M-50) (36 grams) was roll milled with 1140 grams of a solvent mixture comprising 684 grams methylene chloride and 456 grams 1,1,2- trichloroethane for 2-3 days until a solution formed.
- the above CTL solution was spray fabricated onto the dried CGL again using the spray guns and associated equipment available from Binks.
- a Model 77 spray gun was again used in the non-electrostatic mode in the same Binks spray booth using the same horizontal recipricator.
- the Model 77 spray gun was equipped with a 0.035 fluid nozzle and a N65PB air atomization nozzle.
- the fluid pressure was 57.9 kPa (8.4 psi) and the spray atomization pressure was 413.7 kPa (60 psi). With the atomization pressure at 413.7 kPa (60 psi) and the fan angle at 0°, the fan angle air supply was opened until a reading of 5380 dm 3 /h (190 cu.
- the partially dried coating was dismounted from the mandrel and was dried in an air convection oven by slowly increasing the temperature of the oven from 40 to 135°C in 35 minutes followed by isothermal heating at 135°C for 10 minutes.
- the dry thickness of the CTL was 23.2 micrometers determined from the weight applied to a known area.
- the spray fabricated completed devices were charge-erased cycled using the environmental cyclic scanner at ambient RH (35%), low RH (5%), and at high RH (70%).
- the charge-erase cyclic data for two of these devices at various RH testing conditions is described below.
- Device XIVa was charge-erase tested under the indicated relative humidity sequence allowing considerable ( > 16 hours) equilibration time at the next RH condition prior to charge-erase testing at that new RH condition.
- Device XIVa maintained its high charging level and low residual voltage (V R ) at all relative humidities used in this test.
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Description
Atomization Pressure | (55psi) 379.2 kPa |
Fluid Pressure | (6psi) 41.4 kPa |
Fan Angle | 0.75 turns from closed position |
Fluid Opening | 1.25 turns from closed position |
Atomization Pressure | (55 psi) 379.2 kPa |
Fluid Pressure | (5psi) 34.5 kPa |
Fan Angle | 0.75 turns from closed position |
Fluid Opening | 0.75 turns from closed position. |
Atomization Pressure | (55psi) 379.2 kPa |
Fluid Pressure | (4psi) 27.6 kPa |
Fan Angle | 0.5 turns from closed position |
Fluid Opening | 0.5 turns from closed position. |
Device # | Conductive Layer (Fabrication Method) | VO(1) | VO(200) | VR(1) | VR(200) |
la | duPont CIT (prefabricated) | 420 | 330 | 32 | 36 |
Ib | B.F. Goodrich Carboset® 514A (drawbar) | 460 | --- | 10 | --- |
Ic | Red Spot® LE16610 (sprayed) | 600 | 440 | 36 | 65 |
Id | Polaroid ICP-117 (d rawbar) | 200 | 180 | 22 | 25 |
le | Cul (d rawbar) | 90 | 90 | 4 | 4 |
Device No. | Conductive Layer | Adhesive-Blocking Layer(s) | VO(1) | VO(12K) | VR(1) | VR(12K) | |
Composition | Thickness | ||||||
(micrometer) | |||||||
IIa | Carboset® 514A | P(4PVPy)-P(HEMA) | 08-1.0 @ layer | 1360 | 1320 | 70 | 160 |
IIb | CIT | P(4PVPy)-P(HEMA) | 0.8-1.0 @ layer | 1280 | 1240 | 56 | 130 |
IIc | Carboset® 514A | P(HEMA) | 0.8-1.0 | 1020 | 680 | 30 | 40 |
IId | CIT | P(HEMA) | 0.8-1.0 | 1200 | 1180 | 28 | 56 |
IIe | Carboset® 514A | P(4VPy)-P(HEMA) 1:1 | 0.8-1.0 | 1440 | 1600 | 40 | 270 |
IIf | Carboset® 514A | P(4VPy)-P(HEMA) 2:1 | 0.8-1.0 | 1200 | 1440 | 92 | 300 |
IIg | Carboset® 514A | P(4VPy)-P(HEMA) 1:2 | 0.8-1.0 | 1360 | 1600 | 48 | 290 |
Device No. | REPEAT UNIT MOLAR RATIO | P(4VPy) | P(HEMA) | |||
P(4VPy) | P(HEMA) | m Mole | Grams | m Mole | Grams | |
IIe | 1 | 1 | 5.00 | 0.65 | 5.00 | 0.53 |
IIf | 2 | 1 | 6.93 | 0.73 | 3.47 | 0.45 |
IIg | 1 | 2 | 3.23 | 0.34 | 6.46 | 0.84 |
Device No. | P(4VPy) Adhesive Layer | VO(1) | VO(200) | VR(1) | VR(200) |
(Approx. thickness) (micrometer) | |||||
IIh | 0.0 | 1095 | 1115 | 55 | 50 |
IIi | 0.03 | 880 | 890 | 40 | 40 |
IIj | 0.06 | 925 | 935 | 40 | 40 |
IIk | 0.12 | 940 | 975 | 45 | 50 |
IIl | 0.25 | 1090 | 1120 | 55 | 65 |
IIm | 0.50 | 875 | 950 | 50 | 70 |
IIn | 1.00 | 945 | 1045 | 70 | 95 |
Device No. | Conductive Layer | Adhesive/Blocking Layer Formulations | ||
Tedlar Substrates | Weight % P(VPy) | Grams P(VPy) | Grams Solvent(s) | |
(micro meter) | ||||
IIIa | CIT | 6 (0.8-1.0) | 0.3 P(4VPy) + 0.3 P(2VPy) | 5.64 isopropanol + 3.76 isobutanol |
IIIb | CIT | 1.5 | 0.15 P(4VPy) + 0.15 P(2VPy) | 9,85 t-butanol |
1.5 (0.20 -.25 each) | 5.91 isopropanol + 3.94 isobutanol | |||
IIIc | Carboset 514A | 6 (0.8-1.0) | 0.3 P(4VPy) + 0.3 P(2VPy) | 5.64 isopropanol + 3.76 isobutanol |
IIId | Carboset 514A | 1.5 | 0.15P(4VPy) | 9.85 t-butanol |
1.5 (0.20 -.25 + each) | 0.15 P(2VPy) | 5.91 isopropanol + 3.94 isobutanol |
Device No | Conductive Layer | Adhesive/Blocking Layers Composition/Thickness | VO(1) | VO(12K) | VR(1) | VR(12K) |
IIIa | CIT | P(4VPy) - P(2VPy) 0.8- 1.0 | 1240 | 1320 | 110 | 305 |
IIIb | CIT | P(4VPy) / P(2VPy) 0.20 - .25 each | 1220 | 1110 | 80 | 200 |
IIIc | Carboset 514A | P(4VPy) - P(2VPy) 0.8.1.0 | 1160 | 1200 | 75 | 180 |
IIId | Carboset 514A | P(4VPy) / P(2VPy) 0.20- 25 each | 700 | 800 | 40 | 150 |
Device No. | Conductive Layer | Polymer Blocking Layer | VO(1) | VO(2-5) | VO(200) | VR(1) | VR(200) |
IIIe | Carboset 514A | P(4VPy) | 700 | 3604 | 400 | 45 | 30 |
IIIf | Carboset 514A | P(4VPy) | 750 | 4505 | 500 | 45 | 70 |
IIIg | Titanium | P(4VPy) | 800 | 8202 | 720 | 35 | 50 |
IIIh | Carboset 514A | P(2VPy) | 660 | 5502 | 600 | 100 | 180 |
IIIi | Carboset 514A | P(2VPy) | 640 | 5002 | 560 | 70 | 140 |
IIIj | Titanium | P(2VPy) | 820 | 8802 | 920 | 80 | 225 |
Source of P(HEMA) | [η]dl/g | |
Scientific Polymer Products | 0.654 | 1.0-1.4 x 106 |
Polyscience | 0.506 | --- |
Synthesized | 0.272 | --- |
Device No. | P(HEMA) Solids Level | P(HEMA) | Solvent | |
(Weight%) | (Grams) | Type | Grams | |
IVa | 3.6 | 0.36 | methanol | 9.64 |
IVb | 6.0 | 0.60 | methanol | 9.40 |
IVc | 3.6 | 0.36 | t-butanol | 9.64 |
IVd | 7.2 | 0.72 | t-butanol | 9.28 |
Device No. | P(HEMA) [η] | Blocking Layer Thickness | %RH | VO(1) | VO(200) | VR(1) | VR(200) |
(dl/g) | (micrometer) | ||||||
IVa | 0.272 | 0.5-0.7 | 12 | 910 | 800 | 25 | 32 |
IVb | 0.272 | 0.8-1.0 | 12 | 890 | 870 | 28 | 57 |
IVc | 0.506 | 0.5-0.7 | 29 | 1400 | 1420 | 45 | 50 |
IVd | 0.506 | 0.5-0.7 | <5 | 1340 | 1360 | 60 | 80 |
IVd | 0.506 | 1.0-1.2 | 29 | 1380 | 1410 | 40 | 50 |
IVd | 0.506 | 1.0-1.2 | <5 | 1320 | 1360 | 55 | 75 |
Device No | P(4VPy) | Blocking Layer | %RH | VO(1) | VO(20) | VO(200) | VO(~4k) | VR(1) | VR(20) | VR(200) | VR(~4k) |
(micrometer) | |||||||||||
IVe | No | 0.2-0.4 | 27 | 920 | 860 | 800 | 800 | 22 | 20 | 20 | 25 |
IVe | No | 0.2-0.4 | <5 | 840 | 800 | 800 | 800 | 30 | 35 | 35 | 35 |
IVf | Yes | 0.2-0.4 | 27 | 1030 | 980 | 960 | 960 | 32 | 30 | 30 | 40 |
IVf | Yes | 0.2-0.4 | <5 | 900 | 760 | 760 | 760 | 45 | 50 | 50 | 50 |
IVg | No | 0.5-0.7 | 27 | 880 | 900 | 880 | 920 | 25 | 25 | 25 | 30 |
IVg | No | 0.5-0.7 | <5 | 840 | 860 | 860 | 880 | 37 | 65 | 65 | 55 |
IVI | Yes | 0.5-0.7 | 27 | 1000 | 980 | 980 | 1000 | 25 | 25 | 25 | 27 |
IVI | Yes | 0.5-0.7 | <5 | 920 | 980 | 980 | 940 | 37 | 57 | 57 | 45 |
IVm | No | 0.8-1.0 | 27 | 940 | 960 | 960 | 980 | 25 | 25 | 20 | 20 |
IVm | No | 0.8-1.0 | <5 | 940 | 1000 | 1000 | 1020 | 30 | 40 | 50 | 50 |
IVn | Yes | 0.8-1.0 | 27 | 940 | 1000 | 1020 | 1050 | 25 | 30 | 25 | 22 |
IVn | Yes | 0.8-1.0 | <5 | 960 | 1050 | 1050 | 1050 | 35 | 75 | 80 | 70 |
IVo | No | 2.0-2.4 | 27 | 800 | 880 | 880 | 800 | 75 | 90 | 95 | 115 |
IVo | No | 2.0-2.4 | <5 | 840 | 1050 | 1070 | 950 | 100 | 180 | 210 | 200 |
IVp | Yes | 2.0.2.4 | 27 | 800 | 960 | 960 | 1020 | 180 | 220 | 230 | 320 |
IVp | Yes | 2.0-2.4 | <5 | 860 | 1100 | 1100 | 1020 | 205 | 270 | 300 | 280 |
Device No. | [η] | P(HEMA) Blocking Layer | %RH | VO(1) | VO(200) | VR(1) | VR(200) | |
Solvent | Thickness | |||||||
(µm) | ||||||||
Va | 0.272 | Methanol | 0.5-0.7 | 12 | 400 | 380 | 18 | 48 |
Vb | 0.272 | Methanol | 0.8-1.0 | 12 | 380 | 340 | 15 | 25 |
Vc | 0.654 | Methanol | 0.5-0.7 | 16 | 600 | 560 | 29 | 82 |
Vc | 0.654 | Methanol | 0.5-0.7 | 29 | 630 | 650 | 55 | 205 |
Vd | 0.654 | Methanol | 0.8-1.0 | 16 | 770 | 780 | 20 | 20 |
Vd | 0.654 | Methanol | 0.8-1.0 | 29 | 780 | 790 | 20 | 45 |
Ve | 0.654 | t-Butanol | 0.2-0.4 | 15 | 400 | 410 | 26 | 50 |
Vf | 0.654 | t-Butanol | 0.2-0.4 | 15 | 440 | 460 | 26 | 55 |
Vg | 0.654 | Dowanol PM | 0.8-1.0 | 21 | 805 | 860 | 30 | 50 |
Vh | 0.654 | Dowanol PM | 0.5-0.7 | 21 | 385 | 450 | 40 | 105 |
Device | P(HPMA) Blocking Layer | X Cycles | VO(1) | VO(X) | VR(1) | VR(X) |
(micrometer) | ||||||
VIa | 0.1-0.3 | 12,000 | 900 | 750 | 76 | 140 |
VIb | 0.5-0.7 | 12,000 | 880 | 750 | 56 | 68 |
VIc | 0.8-1.0 | 12,000 | 840 | 840 | 40 | 35 |
VIc | 0.8-1.0 | Rest + 45,000 | 820 | 540 | 60 | 44 |
VId | 1.3-1.5 | 12,000 | 740 | 680 | 36 | 68 |
Device No. | Blocking Layer Composition | % RH | VO(1) | VO(200) | VR(1) | VR(200) |
VIe | P(HPMA) | 58 | 1220 | 1420 | 35 | 60 |
VIe | P(HPMA) | <5 | 1440 | 1510 | 60 | 190 |
VIf | P(HEMA) | 35 | 900 | 900 | 40 | 50 |
VIf | P(HEMA) | <5 | 880 | 940 | 35 | 50 |
Device No. | [η] | P(HEMA) Blocking Layer | VO(1) | VO(200) | VR(1) | VR(200) | |
Thickness | Solvent | ||||||
(µm) | |||||||
VIIa | 0.272 | 0.5-0.7 | Methanol | 310 | 310 | 36 | 86 |
VIIb | 0.272 | 0.8-1.0 | Methanol | 370 | 320 | 36 | 50 |
VIIc | 0.654 (X-linked) | 0.5-0.7 | Methanol | 695 | 640 | 40 | 65 |
VIId | 0.654 | 0.5-0.7 | Methanol | 540 | 560 | 40 | 104 |
VIIe | 0.654 (X-linked) | 0.8-1.0 | Methanol | 885 | 885 | 35 | 35 |
VIIf | 0.654 | 0.8-1.0 | Methanol | 800 | 920 | 52 | 80 |
VIIg | 0.654 (X-linked) | 0.5-0.7 | DowPM | 840 | 1000 | 30 | 75 |
VIIh | 0.654 | 0.5-0.7 | Dow PM | 880 | 1040 | 90 | 200 |
VIIi | 0.654 | 0.8-1.0 | Dow PM | 830 | 970 | 76 | 85 |
VIIj | 0.654 | 0.2-0.4 | t-Butanol | 600 | 380 | 40 | 44 |
VIIk | 0.654 | 0.2-0.4 | t-Butanol | 720 | 500 | 50 | 3 |
Blocking Layer | X-Cycles | VO(1) | VO(X) | VR(1) | VR(X) | ||
Device No. | Composition | Thickness | |||||
(micrometers) | |||||||
VIIIa | P(HPMA) | 0.5-0.7 | 1,450 | 730 | 680 | 35 | 25 |
VIIIb | P(HPMA) | 0.8-1.0 | 1,450 | 680 | 640 | 30 | 24 |
VIIIc | P(HEMA) | 0.8-1.0 | 12,000 | 1,200 | 1,000 | 20 | 58 |
VIIId | P(HEMA) | ~8.5 | 12,000 | 1,200 | 1,400 | 24 | 174 |
P(HEMA) Blocking Layer | VO(1) | VO(200) | VR(1) | VR(200) | ||
Device No. | Thickness | Solvent | ||||
(micrometers) | ||||||
VIIIe | 0.5-0.7 | Dow PM | 1040 | 1130 | 15 | 28 |
VIIIf | 0.2-0.4 | t-butanol | 1020 | 1020 | 18 | 38 |
VIIIg | 0.2-0.4 | t-butanol | 1015 | 1010 | 16 | 22 |
VIIIh, | 0.2-0.4 | t-butanol | 870 | 870 | 25 | 25 |
VIIIi, | 0.8-1.0 | Dow PM | 920 | 920 | 25 | 25 |
Copolymer No. | Monomers Charged | Polymerization Conditions | Yield Grams | Polymer Composition | |||||
HEMA | 4VPy | Time | Temp. | Mole % Repeat Unit | |||||
grams | moles | grams | moles | P(HEMA) | P(4VPy) | ||||
(grams solvent) | (mole%) | (mole%) | (hrs) | (°C) | (%) | ||||
IXa (150) | 21 84 | 1.678x10-1 (84) | 3.38 | 3.22x10-2 (16) | 15 | 66 | 17.93 (71) | 91 | 9 |
IXb (150) | 17.65 | 1.356x10-1 (68) | 6.77 | 6.44x10-2 (32) | 15 | 57 | 12 20 (50) | 64 | 36 |
ICc (150) | 13.01 | 1.00x10-1 (50) | 10.51 | 1.00x10-1 (50) | 16 | 62 | 10.50 (45) | 40 | 60 |
Device No. | Blocking Layer | VO(1) | VO(200) | VR(1) | VR(200) | |
Composition | Thickness | |||||
P(HEMA-4VPy) Copolymer Mole % R.U. | (micrometer) | |||||
IXd | 91-9 | 0.8-1.0 | 880 | 920 | 40 | 60 |
IXe | 64-36 | 0.2-0.4 | 960 | 1000 | 50 | 50 |
IXf | 64-36 | 0.5-0.7 | 860 | 1000 | 50 | 80 |
IXg | 64-36 | 0.8-1.0 | 980 | 1000 | 50 | 75 |
IXh | 40-60 | 0.8-1.0 | 880 | 900 | 50 | 90 |
Device No. | 64:36 Copolymer Blocking Layer | %RH | V(X Cycles) | VO(1) | VO(1200) | VO(X) | VR(1) | VR(1200) | VR(X) |
IXi | 0.2-0.4 | 24 | 4415 | 890 | 970 | 920 | 30 | 37 | 40 |
IXi | 0.2-0.4 | <5 | 2260 | 860 | 1040 | 1040 | 35 | 90 | 80 |
IXj | 0.5-0.7 | 24 | 4415 | 780 | 910 | 810 | 28 | 55 | 60 |
IXj | 0.5-0.7 | <5 | 2260 | 780 | 1050 | 1040 | 38 | 170 | 145 |
IXk | 2.0-2.4 | 24 | 4415 | 840 | 1040 | 1100 | 35 | 85 | 165 |
IXk | 2.0-2.4 | <5 | 2260 | 850 | 1200 | 1230 | 65 | 250 | 260 |
Copolymer No. | Monomers Charged | Polymerization Conditions | Yield Grams | Polymer Composition | |||||
HEMA | M2 | Time | Temp | Mole % Repeat Unit | |||||
grams | moles | grams | moles | HEMA | M2 | ||||
(grams solvent) | (mole%) | (mole%) | (hrs) | (°C) | (%) | ||||
HPMA | |||||||||
Xa | 40.00 | 3.073x10-1 | 44.30 | 3.073x10-1 | 19.5 | 78 | 66,07 | 59 | 41 |
(480) | (50) | (50) | (78) | ||||||
HPMA | |||||||||
Xb | 60.00 | 4.610x10-1 | 22.16 | 1.537x10-1 | 19.5 | 76 | 66,50 | 81 | 19 |
(480) | (75) | (25) | (81) | ||||||
VP | |||||||||
Xc | 40.00 | 3.073x10-1 | 16.07 | 1.446x10-1 | 17.5 | 83 | 51,40 | 80 | 20 |
(340) | (68) | (32) | (92) | ||||||
VP | |||||||||
Xd | 50.00 | 3.840x10-1 | 10.68 | 9.600x10-2 | 17.5 | 79 | 54,15 | 88 | 12 |
(360) | (80) | (20) | (89) |
Device No. | Blocking Layer | VO(1) | VO(200) | VR(1) | VR(200) | |
Composition | Thickness | |||||
P(HEMA-M2) Copolymer Mole % R.U. | (µm) | |||||
Xe | P(HEMA-HPMA) 59-41 | 0.5-0.7 | 840 | 770 | 27 | 40 |
Xf | P(HEMA-VP) 88-12 | 0.8-1.0 | 840 | 850 | 24 | 35 |
Blocking Layer Compositions | |||
Device No. | Repeat Unit Mole Percent | Weight Percent | Weight Percent |
P(EOx)-P(HEMA) | P(EOx)-P(HEMA) | Polymers in Methanol | |
XIa | 54-46 | 47-53 | 6.0 |
XIb | 43-57 | 36-64 | 5.8 |
XIc | 30-70 | 25-75 | 5.7 |
Xld | 16-84 | 13-87 | 6.0 |
XIe | 8.5-91.5 | 7-93 | 6.0 |
XIf | 7-93 | 5.5-94.5 | 3.6 |
Device No. | Blocking Layer Composition | %RH | V(X cycles) | VO(1) | VO(200) |
P(EOx) - P(HEMA) Repeat Unit Mole % | |||||
XIa, | 54-46 | 24 | 200 | 1020 | 1150 |
XIb, | 43-57 | 24 | 200 | 1040 | 1150 |
XIc, | 30-70 | 24 | 200 | 970 | 1050 |
XId, | 16-84 | 24 | 3015 | 860 | 1030 |
XId, | 16-84 | <5 | 3515 | 1000 | 1250 |
XIe, | 8.5-91.5 | 20 | 2250 | 760 | 790 |
XIe, | 8.5-91.5 | < 5 | 3560 | 760 | --- |
XIf, | 7-93 | 20 | 2250 | 550 | --- |
XIf, | 7-93 | <5 | 3560 | 520 | --- |
XIa, | --- | 70 | 200 | --- | |
XIb, | --- | 60 | 140 | --- | |
XIc, | --- | 55 | 95 | --- | |
XId, | 980 | 30 | 50 | 45 | |
XId, | 1100 | 60 | 235 | 168 | |
Xle, | 760 | 50 | 50 | 65 | |
XIe, | 800 | 60 | --- | 60 | |
XIf, | 740 | 250 | --- | 350 | |
XIf, | 590 | 240 | --- | 270 |
Device No . | Blocking Layer Composition | VO(1) | VO(200) | VR(1) | VR(200) |
Mole % Repeat Units | |||||
XIIa | P(HEMA-HPMA) Copolymer 81-19 | 770 | 880 | 10 | 16 |
XIIb | P(HEMA-HPMA) Copolymer 59-41 | 840 | 850 | 15 | 36 |
XIIc | P(HEMA-VP) Copolymer 88-12 | 770 | 940 | 27 | 32 |
XIId | P(HEMA-4VPy) Copolymer 64-36 | 860 | 960 | 31 | 70 |
XIIe | P(HEMA)-P(EOx) Complex 93-7 | 910 | 930 | 26 | 50 |
Device No. | P(HEMA-4VPy) Copolymer Blocking Layer - | V(X cycles) | VO(1) | VO(X) | VR(1) | VR(X) | |
(micrometers) | %RH | ||||||
XIIIa | 0.5-0.7 | 12 | 200 | 460 | 380 | 43 | 76 |
XIIIb | 0.8-1.0 | 12 | 200 | 730 | 780 | 46 | 76 |
XIIIb | 0.8-1.0 | <5 | 1420 | 700 | 680 | 53 | 110 |
Device No. | P(EOx)-P(HEMA) Blend Blocking Layer | %RH | VO(1) | VO(200) | VR(1) | VR(200) |
P(EOx)-P(HEMA) | ||||||
XIIIc | 54-46 | 19 | 980 | 1350 | 90 | 500 |
XIIId | 43-57 | 19 | 1000 | 1050 | 40 | 110 |
XIIIe | 30-70 | 19 | 1000 | 1130 | 35 | 35 |
XIIIe | 30-70 | <5 | 880 | 1100 | 45 | 125 |
XIIIf | 16-84 | 19 | 900 | 920 | 25 | 25 |
XIIIf | 16-84 | <5 | 780 | 860 | 35 | 50 |
XIIIf | 16-84 | < 5 | 860 | 920 | 45 | 112 |
XIIIf | 16-84 | 24 | 820 | 900 | 35 | 80 |
Device No. | % RH | X Cycles | VO(1) | VO(X) | VR(1) | VR(X) |
XIVa | 35 | 1200 | 881 | 895 | 7 | 3 |
5 | 200 | 960 | 950 | 10 | 9 | |
70 | 3200 | 876 | 950 | 5 | 30 | |
< 5 | 3000 | 920 | 870 | 15 | 15 | |
XIVb | 35 | 3400 | 909 | 942 | 5 | 3 |
Claims (19)
- An electrophotographic imaging member comprising a supporting substrate having an electrically conductive surface, a charge blocking layer comprising a water insoluble high molecular weight hydroxy methacrylate polymer having a weight average molecular weight of at least 10,000, and at least one photoconductive layer, wherein said blocking layer has a surface resistivity greater than 1010 ohms/square and wherein said water insoluble high molecular weight hydroxy methacrylate polymer is a polymeric reaction product of one or more monomers having the following structure: whereinR is an aliphatic hydrocarbon group having 1 to 5 carbon atoms, andz is 1 to 5.
- The electrophotographic imaging member according to Claim 1, wherein said water insoluble high molecular weight hydroxy methacrylate polymer is represented by the following formula: whereinx represents sufficient repeat units for a weight average molecular weight between 20,000 and 2,000,000,R is an aliphatic hydrocarbon group having 1 to 5 carbon atoms, andz is 1 to 5.
- The electrophotographic imaging member according to Claim 1 or 2, wherein said water insoluble high molecular weight hydroxy methacrylate polymer has a weight average molecular weight of between 100,000 and 2,000,000.
- The electrophotographic imaging member according to Claim 4, wherein said blocking layer has a thickness between 0.8 µm and 1 µm.
- The electrophotographic imaging member according to Claim 1, wherein said electrically conductive surface comprises carbon black impregnated polyvinyl fluoride and said blocking layer has a thickness between 0.05 µm and 8 µm.
- The electrophotographic imaging member according to Claim 1, wherein said blocking layer has a thickness between 0.3 µm and 1.5 µm.
- The electrophotographic imaging member according to Claim 1, wherein said water insoluble high molecular weight hydroxy methacrylate polymer is a homopolymer.
- The electrophotographic imaging member according to Claim 1, wherein said photoconductive layer comprises a charge generating layer and a charge transport layer.
- The electrophotographic imaging member according to Claim 1, wherein said electrically conductive surface comprises a hole injecting material.
- The electrophotographic imaging member according to Claim 10, wherein said electrically conductive surface comprises copper iodide.
- The electrophotographic imaging member according to Claim 1, wherein the resistivity of said electrically conductive surface is less than 108 ohms/square.
- The electrophotographic imaging member according to Claim 1, wherein an adhesive layer is sandwiched between said charge blocking layer and said photoconductive layer.
- The electrophotographic imaging member according to Claim 13, wherein said adhesive layer comprises poly-4-vinylpyridine hydrogen bonded to said hydroxy methacrylate polymer.
- The electrophotographic imaging member according to Claim 1, wherein said water insoluble high molecular weight hydroxy methacrylate polymer is cross-linked.
- An electrophotographic imaging process comprising providing the electrophotographic imaging member according to any of claims 1 to 15, depositing a uniform electrostatic charge of at least 20 V/µm on the imaging surface of said imaging member, exposing said imaging member to activating radiation in image configuration to form an electrostatic latent image, contacting said imaging surface with marking particles to form a marking particle image on said imaging surface in conformance with said electrostatic latent image, transferring said marking particle image to a receiving member, and repeating said depositing, exposing, contacting and transferring steps at least once.
- A process for preparing an electrophotographic imaging member comprising providing a supporting substrate having an electrically conductive surface, forming a dry, continuous charge blocking layer comprising a water insoluble high molecular weight hydroxy methacrylate polymer having a weight average molecular weight of at least 10,000 and having a surface resistivity greater than 1010 ohms/square on said electrically conductive surface, forming at least one photoconductive layer on said charge blocking layer, said water insoluble high molecular weight hydroxy methacrylate polymer being a polymeric reaction product of at least one monomer having the following structure: whereinR is an aliphatic hydrocarbon group having 1 to 5 carbon atoms, andz is 1 to 5,
- The process for preparing an electrophotographic imaging member according to Claim 17, including that the forming of at least one photoconducitve layer comprises applying a mixture of photoconductive particles dispersed in a solution of a film forming polymer dissolved in at least one solvent to form a coating and drying said coating to form a dry photoconductive layer.
- The process for preparing an electrophotographic imaging member according to Claim 18, including crosslinking said water insoluble high molecular weight hydroxy methacrylate polymer having a weight average molecular weight of at least 10,000 while forming said dry, continuous charge blocking layer on said electrically conductive surface.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US45891689A | 1989-12-29 | 1989-12-29 | |
US458916 | 1995-06-02 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0448780A1 EP0448780A1 (en) | 1991-10-02 |
EP0448780B1 true EP0448780B1 (en) | 1998-04-08 |
Family
ID=23822611
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19900120917 Expired - Lifetime EP0448780B1 (en) | 1989-12-29 | 1990-10-31 | Electrophotographic imaging member |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0448780B1 (en) |
JP (1) | JP3029464B2 (en) |
DE (1) | DE69032218T2 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5244762A (en) * | 1992-01-03 | 1993-09-14 | Xerox Corporation | Electrophotographic imaging member with blocking layer containing uncrosslinked chemically modified copolymer |
DE69417328T2 (en) * | 1993-09-10 | 1999-10-14 | Canon Kk | Electrophotographic apparatus, operating cassette and imaging process |
EP0752625B1 (en) * | 1995-07-06 | 2000-11-15 | Hewlett-Packard Company | Copolymers useful as charge injection barrier materials for photoreceptor |
US7534535B2 (en) * | 2004-11-23 | 2009-05-19 | Xerox Corporation | Photoreceptor member |
CN101405051A (en) * | 2006-03-21 | 2009-04-08 | 阿尔扎公司 | Hydratable polymeric ester matrix for drug electrotransport |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS51126149A (en) * | 1974-11-16 | 1976-11-04 | Konishiroku Photo Ind Co Ltd | Photosensitive plate for electrophotography |
US4281055A (en) * | 1979-02-24 | 1981-07-28 | Konishiroku Photo Industry Co., Ltd. | Photosensitive element with water soluble interlayer |
JPS5912453A (en) * | 1982-07-14 | 1984-01-23 | Fuji Photo Film Co Ltd | Electrophotographic sensitive material |
US4822705A (en) * | 1987-02-24 | 1989-04-18 | Ricoh Company, Ltd. | Electrophotographic photoconductor with layer preventing charge injection |
-
1990
- 1990-10-31 DE DE1990632218 patent/DE69032218T2/en not_active Expired - Fee Related
- 1990-10-31 EP EP19900120917 patent/EP0448780B1/en not_active Expired - Lifetime
- 1990-12-25 JP JP2406119A patent/JP3029464B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
JPH04104162A (en) | 1992-04-06 |
EP0448780A1 (en) | 1991-10-02 |
JP3029464B2 (en) | 2000-04-04 |
DE69032218D1 (en) | 1998-05-14 |
DE69032218T2 (en) | 1998-07-30 |
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