WO2014142844A1 - Photoconducteurs organiques - Google Patents

Photoconducteurs organiques Download PDF

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Publication number
WO2014142844A1
WO2014142844A1 PCT/US2013/030963 US2013030963W WO2014142844A1 WO 2014142844 A1 WO2014142844 A1 WO 2014142844A1 US 2013030963 W US2013030963 W US 2013030963W WO 2014142844 A1 WO2014142844 A1 WO 2014142844A1
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WO
WIPO (PCT)
Prior art keywords
polyfluorene
salt
aryl
carbons
group
Prior art date
Application number
PCT/US2013/030963
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English (en)
Inventor
Sivapackia Ganapathiappan
Krzysztof Nauka
Hou T. Ng
Original Assignee
Hewlett-Packard Development Company, L.P.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hewlett-Packard Development Company, L.P. filed Critical Hewlett-Packard Development Company, L.P.
Priority to PCT/US2013/030963 priority Critical patent/WO2014142844A1/fr
Publication of WO2014142844A1 publication Critical patent/WO2014142844A1/fr

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Classifications

    • 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
    • G03G5/02—Charge-receiving layers
    • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
    • G03G5/05—Organic bonding materials; Methods for coating a substrate with a photoconductive layer; Inert supplements for use in photoconductive layers
    • G03G5/0528—Macromolecular bonding materials
    • G03G5/0532—Macromolecular bonding materials obtained by reactions only involving carbon-to-carbon unsatured bonds
    • G03G5/0542—Polyvinylalcohol, polyallylalcohol; Derivatives thereof, e.g. polyvinylesters, polyvinylethers, polyvinylamines
    • 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
    • G03G5/02—Charge-receiving layers
    • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
    • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
    • G03G5/0601—Acyclic or carbocyclic compounds
    • G03G5/0603—Acyclic or carbocyclic compounds containing halogens
    • 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
    • G03G5/147—Cover layers
    • G03G5/14708—Cover layers comprising organic material
    • 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
    • G03G5/147—Cover layers
    • G03G5/14708—Cover layers comprising organic material
    • G03G5/14713—Macromolecular material
    • G03G5/14717—Macromolecular material obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • G03G5/1473—Polyvinylalcohol, polyallylalcohol; Derivatives thereof, e.g. polyvinylesters, polyvinylethers, polyvinylamines

Definitions

  • An organic photoconductor is one of the components in an electrophotographic (EP) printer.
  • a latent image which is a surface charge pattern, is created on the OPC prior to contact with a development system containing charged marking particles. This is accomplished by uniformly charging the OPC surface, followed by selective illumination that locally generates opposite charges which then move to the surface and locally neutralize deposited charges.
  • the OPC frequently has two layers: an inner layer for generating charges (charge generation layer - CGL) and an outer layer containing molecular moieties for facilitating charge movement (charge transport layer - CTL).
  • the OPC element may have a very uniform and defect free structural and electrical characteristics.
  • FIG. 1 is a schematic diagram of an apparatus that employs an example organic photoconductor (OPC) drum, in accordance with the teachings herein.
  • OPC organic photoconductor
  • FIG. 1 A is an enlargement of a portion of the OPC drum of FIG. 1 .
  • FIG. 2 is a flow chart depicting an example method for preparing a polyfluorene salt that is soluble in lower alkyl alcohols and/or water, in accordance with the teachings herein.
  • FIG. 3 is a flow chart depicting an example method for coating an OPC drum with the polyfluorene salt, in accordance with the teachings herein.
  • FIGS. 4A-4B on coordinates of optical density (OD) and number of impressions (K impressions), are each a plot of the sustainable evolution of OD with extended impressions for 20% ink (FIG. 4A) and 80% ink (FIG. 4B), based on an OPC drum provided with the coating of the polyfluorene salt.
  • alkyl refers to a branched, unbranched, or cyclic saturated hydrocarbon group, which typically, although not necessarily, includes from 1 to 50 carbon atoms, or 1 to 30 carbon atoms, or 1 to 6 carbons, for example.
  • Alkyls include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n- butyl, isobutyl, t-butyl, octyl, and decyl, for example, as well as cycloalkyi groups such as cyclopentyl, and cyclohexyl, for example.
  • “Lower alkyl” is an alkyl with 1 to 4 carbon atoms.
  • aryl refers to a group including a single aromatic ring or multiple aromatic rings that are fused together, directly linked, or indirectly linked (such that the different aromatic rings are bound to a common group such as a methylene or ethylene moiety).
  • Aryl groups described herein may include, but are not limited to, from 5 to about 50 carbon atoms, or 5 to about 40 carbon atoms, or 5 to 30 carbon atoms or more.
  • Aryl groups include, for example, phenyl, naphthyl, anthryl, phenanthryl, biphenyl, phenoxyphenyl, aminobi- phenyl, and benzoylphenyl.
  • substituted aryl refers to an aryl group comprising one or more substituent groups.
  • heteroaryl refers to an aryl group in which at least one carbon atom is replaced with a heteroatom. If not otherwise indicated, the term “aryl” includes unsubstituted aryl, substituted aryl, and heteroaryl.
  • substituted means that a hydrogen atom of a compound or moiety is replaced by another atom such as a carbon atom or a heteroatom, which is part of a group referred to as a substituent.
  • substituents include, but are not limited to, for example, alkyl, alkoxy, aryl, aryloxy, alkenyl, alkenoxy, alkynyl, alkynoxy, thioalkyl, thioalkenyl, thioalkynyl, and thioaryl.
  • halo and halogen refer to a fluoro, chloro, bromo, or iodo substituent.
  • alcohol means a lower alkyl chain alcohol, such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, and tert- butanol.
  • the organic photoconductor (OPC) in an electrophotographic printer is a thin film photoconductive layer.
  • An electrostatic latent image is formed on the pre-charged photoreceptor surface via image-wise optical exposure.
  • a visual image is obtained after the electrostatic image is developed with charged color toner particles that are subsequently transferred to paper and the OPC is prepared for the next imaging process.
  • the photoreceptor (web or cylinder) is required to have very uniform area characteristics: coating uniformity, dark conductivity, and photoconductivity.
  • the OPC surface is subjected to a number of punishing electrochemical and mechanical processes. They include corrosive ozone and acid treatments from corona charging, abrasive mechanical treatments from toner development, and toner transfer to paper and doctor blade cleaning. They may cause removal of the top part of CTL or mechanical damage (scratching) and local cracking of the CTL.
  • FIG. 1 is a schematic diagram of portion of a generic EP printer.
  • the illustrative example of FIG. 1 depicts a liquid EP printer. It will be understood that examples herein might be implemented in any type of EP printers such as, but not limited to, a dry toner EP printer.
  • An EP printer 100 comprises an OPC drum 102 that is rotatable about an axis 102a.
  • the OPC drum 102 rotates, it passes through several stations, including a charging station 104, an exposure station 106, a development station 108, and a transfer station 1 10.
  • an electrostatic charge is uniformly distributed over the surface of the OPC drum 102. Charging is typically done by a corona or a charge roller.
  • the exposure station 106 also known as the image-forming station
  • the document to be printed or its image formed on a screen is illuminated and either passed over a lens or is scanned by a moving light and lens, such that its image is projected onto and synchronized with the moving drum surface.
  • the corresponding area of the drum becomes lit.
  • the drum is not illuminated.
  • the charge that remains on the drum after this exposure is a "latent" image and is a negative of the original document.
  • the drum 102 is presented with toner, e.g., liquid toner, more specifically, black ink in the case of a black ink- only printer and colored inks in the case of a color ink printer.
  • toner e.g., liquid toner, more specifically, black ink in the case of a black ink- only printer and colored inks in the case of a color ink printer.
  • the liquid toner is electrically charged and attracted to areas on the drum bearing complementary electrical charges.
  • the ink on the drum 102 is transferred to a print medium 1 12 either directly or through an intermediate transfer medium, moving in the direction indicated by arrow A.
  • the drum 102 is prepared for a new imaging cycle.
  • FIG. 1 A is an enlargement of a portion of the drum 102 of FIG. 1 , and depicts an example configuration in accordance with the teachings herein.
  • An OPC 120 may comprise a conductive substrate 122, a charge generation layer (CGL) 124, and a charge transport layer (CTL) 126.
  • the thickness of the CTL 126 may be greater than 10 ⁇ .
  • a CTM-doped protective coating (DPC) 128 may be formed over the exterior surface of the CTL 126. While each layer may be formed "on" the layer below, there may be one or more intermediate layers provided.
  • Such intermediate layers do not alter the basic structure of the conductive substrate 122, the CGL 124, the CTL 126, and the DPC 128, but may serve to augment these layers 122, 124, 126, 128.
  • the term “over” is intended to include both “directly on” and separation by one or more intermediate layers.
  • the organic photoconductor commonly used in electrophotographic applications is a dual layer structure consisting of a relatively thin (for example, 0.1 to 2 ⁇ ) bottom layer (CGL) 124 and a relatively thick (for example, about 20 ⁇ ) top layer (CTL) 126.
  • CGL bottom layer
  • CTL top layer
  • Light passes through the transparent CTL and strikes the CGL that generates free electrons and holes. Electrons are collected by the electrical ground of the photoreceptor and holes are driven towards the top of the CTL by the applied electrical field.
  • the CTL provides a mechanism for holes transporting towards the surface, where they are used to neutralize negative surface ions deposited during the pre-charging process.
  • the CTL 126 may consist of non-conductive organic material (usually a polymer) with charge transport moieties embedded in it.
  • the CTL 126 may be made of a non-conductive polycarbonate matrix having charge transport moieties in form of conductive organic small molecules or short chain polymers, such as aryl hydrazones, aminoaryl heterocycles such as oxa- diazole, and, in some examples, highly conjugated arylamines.
  • the organic photoconductor (OPC) in an electrophotographic printer is a thin film photoconductive layer.
  • An electrostatic latent image is formed on the pre-charged photoreceptor surface via image-wise optical exposure.
  • a visual image is obtained after the electrostatic image is developed with charged color toner particles that are subsequently transferred to paper.
  • the photoreceptor needs to be cleaned and the corona charged with ions to get ready for the next imaging process.
  • the photoreceptor web or cylinder
  • the photoreceptor is required to have very uniform area characteristics: coating uniformity, dark conductivity, and photoconductivity.
  • the OPC surface is subjected to a number of punishing electrochemical and mechanical processes.
  • the structure of the organic photoreceptor usually has several layers of materials, each of which performs a specific function, such as charge generation, charge transport, and occasionally additional surface protection. These layers are formed by individual sequential coatings.
  • One of these layers is the charge transport material (CTM) layer, or CTL 126.
  • CTM charge transport material
  • CTL 126 CTL 126.
  • CTM charge transport material
  • aromatic tertiary amino compounds and their corresponding polymers are usually used.
  • these materials are soluble in common organic solvents such as tetrahydrofuran (THF) and dichloromethane (CH2CI2). Because of their solubility in these solvents, there is usually a loss of charge transport material and/or mixing with the material that is over-coated on top for protection. In addition, these materials cannot facilitate "fast" transport of electrical charges, making them less desirable for the high-speed printing applications, such as digital commercial printing.
  • the photoreceptor (belt or cylinder) ideally has very uniform area characteristics: coating uniformity, dark conductivity, and photoconductivity.
  • the OPC surface is subjected to a number of punishing electrochemical and mechanical processes. These include corrosive ozone and oxidative reactions from corona or charge roller charging, abrasive mechanical treatments from toner development, toner transfer to paper, and doctor blade cleaning of the drum and contact with a charge roller.
  • the essential physical properties that dictate the electrophotographic imaging process, such as dark and photo conductivity and electronic defects on the photoreceptor surface etc. would definitely accelerate their deterioration under such detrimental conditions. Therefore, it may be desirable to develop protective overcoats for the OPCs.
  • Polycarbonates used in the CTL 126 can survive only a few solvents such as water and alcohols, while essentially all of the commercially-available CTMs have very poor solubility in water and alcohols. Thus, the development of water-soluble CTMs could permit a solution process to coat the OPC layer without damaging the polycarbonate layer.
  • the respective liquid solvent mixture of monomers, oligomers or even polymers, mixed with uniformly distributed charge transfer species may be used, followed by deposition of the mixture on the photocon- ductor and, finally, cross-linking of the polymerizable species.
  • the resulting product is a thin protective layer, fully mechanically conformal with the photo- conductor and containing uniformly distributed charge transfer moieties.
  • this process can be used to the entire CTL region - in this case, a thin solvent mixture layer may be deposited on the CGL film. Deposition process can be further controlled by using appropriate surfactants improving wetting of the deposition substrate.
  • Hole transport material is essential in the operation of an OPC to transport holes.
  • aromatic tertiary amines are commonly used. They are crystalline materials and require a large amount of the amine, as hole conduction has to occur by a hopping mechanism. The presence of large amounts of these crystalline materials degrades the integrity of the film that contains these compounds.
  • the structure of some of the hole transport compounds (PTA and TBD) are shown below.
  • PTA is tris(p-tolylamine);
  • TBD is N,N'-Bis(3- methylphenyl)-N,N'-diphenylbenzidine. Solubility of these compounds is also limited in lower alkyl alcohols, such as iso-propanol (isopropyl alcohol, IPA).
  • conductive polymers In order to minimize the amount of these materials, more effective conductive polymers are used.
  • conjugated polymers especially fluorene-based polymers.
  • These polymers are soluble in organic solvents such as toluene, chloroform, dichloromethane or tetrahydrofuran but poorly soluble in lower alkyl alcohols such as isopropyl alcohol (IPA).
  • IPA isopropyl alcohol
  • a fluorene polymer that is soluble in IPA can be made.
  • An example includes forming alcohol-soluble coatings that have cationic alternate fluorene-based monomers with phosphonium salt terminal groups. These coatings may be used to coat the OPC and then cross- linked in-situ to form cationic alternate fluorene-based copolymers with phos- phonium salt terminal groups.
  • alcohol-soluble coatings that have cationic alternate fluorene-based monomers with phosphonium salt terminal groups.
  • IPA-soluble, polyfluorenes may be desired.
  • scalable synthetic methods and key building blocks of a class of fluorene-based polymers are provided, employing a one-step modification. These polyfluorenes readily solubilize in isopropyl alcohol for effective coating without detrimental damage to underlying substrate.
  • the solvent is used to apply the polyfluorenes to the OPC and thus may have a volatility to easily evaporate.
  • a solvent is isopropyl alcohol, as noted above.
  • Other examples include the lower alkyl alcohols (1 to 4 carbon atoms), water and mixtures thereof.
  • the polyfluorenes allow formation of a substantially uniform coating on existing organic photoconductors (OPC) to be realized while extending the operational lifespan by at least five times.
  • OPC organic photoconductors
  • substantially uniform in the context herein means within the variances common in ordinary commercial processing.
  • These materials can either be used to replace the currently-used aromatic tertiary amines which are crystalline hole transport materials (CTM 126) or to form the top overcoat 128.
  • the thickness of the coating in either case may range from about 10 to 5,000 nm.
  • polyfluorenes suitable in the practice of the teachings herein is shown below in the generic formula (I).
  • Various functional groups may be provided that (1 ) render the polyfluorene soluble in IPA (or other lower alkyl alcohol and/or water) and (2) promote use of the polyfluorene as a hole transport material for the OPC.
  • the polyfluorenes may be present in any of the layers 126, 128 from 0.05 to 35% by weight, based on the total composition of the coating.
  • the balance may be any of various polymeric additives such as, for example, polycarbonates and polyesters, as well as poly- vinylphenol.
  • polyfluorene may be present up to 100 wt%.
  • the polyfluorenes suitably employed in the practice of these teachings may have the generic formula (I):
  • R, R', R", R'" are independently H, alkyl, aryl or substituted alkyl or aryl groups with carbons from 1 to 20, and may be the same or different; or alternatively, R, R', R'" are independently alkyl, aryl or substituted alkyl or aryl groups with carbons from 1 to 20 and may be the same or different and R" is a hydroxyalkyi group with carbons from 1 to 20 and the presence of the hy- droxyl group either as a terminal group or as a secondary alcoholic group along the chain to improve solubility in, e.g., isopropyl alcohol;
  • Y COO, SO 3 , PO 3 , OPO 3 ;
  • Formula (II) below shows the structure of an example commercially-available polyfluorene: poly(9,9,-bis(3'-(N,N-dimethyl)-propyl-2,7-fluorene)alt- 2,7-(9,9-dioctylfluorene)) (OS0743, PFN-P1 )
  • Polyfluorene (II) was obtained from 1 -Material (Quebec, Canada). This material is not soluble in IPA. In order to make it soluble in IPA, the tertiary amino groups are converted to ammonium or quaternary ammonium salts. At the same time, the ionic interaction between the cation and the anion has to be minimized to make it more soluble in IPA. If it can be incorporated with a hy- droxyl group containing pendant groups, then the solubility can be further increased. To satisfy these requirements, the above polyfluorene was subjected to three different reactions to form three different reaction products, or polyfluorene salts, that each were soluble in IPA.
  • polyfluorene (II) was neutralized with trifluo- roacetic acid to form trifluoroacetate salt (A).
  • polyfluorene (II) was reacted with ethyl trifluoromethanesulfonate to form trifluoromethanesulfonate salt (B).
  • polyfluorene (II) was reacted with 3- bromopropanol to form the corresponding hydroxypropylammonium derivative (C).
  • the structures of the products obtained in these cases are illustrated below:
  • Structure A1 is a variant of structure A above, while Structure B1 is a variant of structure B above.
  • FIG. 2 is a flow chart illustrating an example method 200 for preparing a polyfluorene, soluble in a lower alkyl alcohol or water, for use as a coating on an OPC.
  • a polyfluorene that is insoluble in the lower alkyl alcohol or water may be provided 205.
  • the polyfluorene may be synthetically prepared, using known synthetic preparation routes. Alternatively, the polyfluorene may be obtained commercially.
  • the polyfluorene may be treated 210 with trifluoroacetic acid or 3- bromopropanol to form a polyfluorene salt.
  • the treating may be done at room temperature or an elevated temperature.
  • the reaction with trifluoroacetic acid may be done at room temperature, while the reaction with bromo- propanol may be improved with heating.
  • Both the polyfluorene and the trifluo- roacetic acid or 3-bromopropanol may each be contained in a solvent that dissolves the polyfluorene, such as chloroform or dichloromethane.
  • the polyfluorene salt which is soluble in the lower alkyl alcohol or water, may be recovered 215. Recovering may be performed, for example, by mild heating to remove the solvent.
  • the solid polyfluorene polymer salt may then be extracted with a lower alkyl alcohol or water or mixture thereof.
  • the polyfluorene salt may be coated onto an OPC drum, either as the charge transport layer 126 on the charge generation layer 124 or as the CTM-doped protective coating 128 on the CTL 126, or both. Two cases and variants thereof are now described.
  • polyfluorene salt form from a solution where the solvent is a lower alkyl alcohol or water
  • the balance is polyvinylphenol or Bisphenol A glycerolate dimethacrylate (BPG-DMA) or mixture of polyvinylphenol and BPG-DMA; optionally, free-radical initiator in the amounts of 0.1 to 3% by weight of BPG-DMA.
  • free-radical initiators are hydrogen peroxide, t-butyl hydroperoxide and 2,2'-azobisisobutyronitrile.
  • protective layer 128 on CTL 126 either 100% polyfluorene salt form (from a solution where the solvent is a lower alkyl alcohol or water), or 0.05 to 35% polyfluorene salt form (from a solution where the solvent is a lower alkyl alcohol or water), and the balance is polyvinyl- phenol or BPG-DMA or mixture of polyvinylphenol and BPG-DMA; optionally, free-radical initiator in the amounts of 0.1 to 3% by weight of BPG-DMA.
  • a dilute solution of the polyfluorene salt may be prepared, using as the solvent one or more of a lower alkyl alcohol and/or water.
  • the solution may contain from about 0.05 to 0.5 wt% of the polymer salt. In another example, the solution may contain about 0.1 wt% of the polymer salt.
  • Coating of the polymer salt on the OPC may be done by any of the common techniques usually employed in such coating processes, including, but not limited to, wired bar, doctor blade, spray coating, and the like.
  • the coating may be processed to remove the solvent, leaving a film of the polyfluorene salt.
  • the film may contain about 0.05 to 35 wt% of the polymer salt, and the balance the polymeric additive(s). Or, in another example, the film may contain 100 wt% of the polyfluorene.
  • Removal of the solvent may be performed by any of the well- known methods, such as by elevated heating for a period of time or simply allowing it to evaporate.
  • the solvent is isopropyl alcohol
  • heat may be supplied to raise the temperature of the underlying substrate to about 80°C for 1 hour.
  • FIG. 3 depicts a flow chart illustrating an example method 300 for coating an organic photoconductor (OPC) with a hole-transport material, namely, the polyfluorene salt.
  • OPC organic photoconductor
  • a polyfluorene salt that is soluble in a lower alkyl alcohol or water as prepared above may be provided 305.
  • the salt may be diluted 310 in a solvent of a lower alkyl alcohol, water, or a mixture thereof to form a dilution of about 0.05 to 0.5 wt%.
  • the polyf- luorene salt alone may be contained in the solvent.
  • a polymer as described above may be included as well. Both instances may be referred to as diluting the polyfluorene salt in the solvent.
  • the diluted polyfluorene salt may be coated 315 on the OPC, and may form the charge generation layer 124, the protective coating 128, or both.
  • the diluted polyfluorene salt and a polymer as described above may be coated on the OPC. Both instances may be referred to as coating the diluted polyfluorene salt on the OPC.
  • the solvent may be removed 320 to form a film of the polyfluorene salt on the OPC. Removal may be done by simple evaporation.
  • a post-deposition annealing may be performed. If done, the annealing may be performed at a temperature in the range of 60° to 120°C for a period of time ranging from about 5 m to 2 h. In an example, the annealing may be performed at 80° for 1 h.
  • An advantage of the post-deposition annealing is that it can provide a better conformity between the OPC substrate (layer 126) and the thin layer polymer coating (layer 128).
  • Example 1 Preparation of polyfluorene with trifluoroacetic acid to form trifluo- roacetate salt (A).
  • Example 3 Coating of OPC with trifluoroacetate salt of polyfluorene II.
  • FIGS. 4A-4B show the sustainable evolution of OD with extended impressions (out to 500,000 impressions each), where FIG. 4A is for the 20% ink and FIG. 4B is for the 80% ink. As can be seen in both cases, the OD remained fairly the same from beginning to end.
  • the coating can extend its lifetime at least 5X, as evidenced by impressions out to 500,000; see FIGS 4A-4B.
  • hole transport materials based on alcohol- soluble and water-soluble polyfluorenes may be used as a charge transport layer and/or as an overcoat to increase the life of the OPC.
  • a generic one-step synthetic modification has been developed to enable these materials to be readily soluble in IPA and other lower alkyl alcohols, water, and mixtures thereof and allow uniform coating on existing OPCs.
  • a single step modification of commercially-available polyfluorene may be achieved in a quantitative manner. This is a simple neutralization process of the pendant amino groups as it does not affect the backbone conductive structure.
  • These modified polyfluorenes may be soluble in IPA, other lower alkyl alcohols, water, and mixtures thereof, which is useful for the coating process. This also increases the life of the OPC almost five times which can reduce the cost of the OPC significantly.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Photoreceptors In Electrophotography (AREA)

Abstract

Un revêtement organique est formé sur une surface d'un photoconducteur organique (OPC), ce revêtement comprenant un matériau de transport de trous. Le matériau de transport de trous est un sel de polyfluorène soluble dans l'eau ou dans un alcool d'alkyle inférieur, ou les deux. L'invention concerne également des procédés de préparation de sel de polyfluorène et de fabrication d'OPC.
PCT/US2013/030963 2013-03-13 2013-03-13 Photoconducteurs organiques WO2014142844A1 (fr)

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