US 20140322638A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2014/0322638A1 Zhou et al. (43) Pub. Date: Oct. 30, 2014 (54) ALCOHOL-SOLUBLE HOLE TRANSPORT (30) Foreign Application Priority Data MATERALS FOR ORGANIC PHOTOCONDUCTOR COATINGS Dec. 15, 2011 (CN) .............................. 2011 O42O829 (75) Inventors: Zhang-Lin Zhou, Palo Alto, CA (US); Publication Classification Krzysztof Nauka, Palo Alto, CA (US); Lihua Zhao, Sunnyvale, CA (US) (51) Int. Cl. GO3G 5/47 (2006.01) (73) Assignee: HEWLETTPACKARD (52) U.S. Cl. DEVELOPMENT COMPANY., L.P., CPC .................................. G03G 5/14717 (2013.01) Houston, TX (US) USPC .................... 430/66; 430/56; 430/132: 528/8 (21) Appl. No.: 14/364,994 (57) ABSTRACT (22) PCT Filed: Dec. 20, 2011 An alcohol-soluble organic coating including a hole transport (86). PCT No.: PCT/US2O11?066256 material formed on a surface of organic photoconductor is provided. The coating comprises a cationic alternate fluo S371 (c)(1), rene-based copolymer with phosphonium salt terminal 2), (4) Date: Jun. 12, 2014 grouprouns embedded in an in-situ cross-linked polypolvmer. Patent Application Publication Oct. 30, 2014 Sheet 1 of 6 US 2014/0322638A1 Patent Application Publication Oct. 30, 2014 Sheet 2 of 6 US 2014/0322638A1 20 350 40 .5 50 550 8. 3) (.8 0.8 4. 302 0.2 O.O 350 400 45 50 550 6OO Wavelength (rim) Fig. 3 Patent Application Publication Oct. 30, 2014 Sheet 3 of 6 US 2014/0322638A1 y'61) {}{} Patent Application Publication Oct. 30, 2014 Sheet 4 of 6 US 2014/0322638A1 s S: s S. : O i. ge ? c s rer Kr sy (un) ideo Joe OS Patent Application Publication Oct. 30, 2014 Sheet 5 of 6 US 2014/0322638A1 9'61) ASueCeOdo US 2014/0322638 A1 Oct. 30, 2014 ALCOHOL-SOLUBLE HOLE TRANSPORT 0009 FIG. 6, on coordinates of optical density and num MATERALS FOR ORGANIC ber of imprints, is a plot of the change in optical density as a PHOTOCONDUCTOR COATINGS function of imprints, comparing an uncoated and a coated OPC, where the coating is an example coating. BACKGROUND 0010 FIG. 7 demonstrates shrinkage of printed features 0001. An organic photoconductor (OPC) is one of the during an extended printing, and the ways that an example components in an electrophotographic (EP) printer. A latent OPC coating can prevent the shrinkage. image, which is a Surface charge pattern, is created on the OPC prior to contact with a development system containing DETAILED DESCRIPTION charged marking particles. This is accomplished by uni 0011 Reference is made now in detail to specific formly charging the OPC surface, followed by selective illu examples, which illustrate the best mode presently contem mination that locally generates opposite charges within the plated by the inventors for practicing the invention. Alterna bulk of the OPC which then move to the surface and locally tive examples are also briefly described as applicable. neutralize deposited charges. The OPC frequently has two 0012. It is to be understood that this disclosure is not layers: an inner layer for generating charges (charge genera limited to the particular process steps and materials disclosed tion layer—CGL) and an outer layer containing molecular herein because such process steps and materials may vary moieties for facilitating charge movement (charge transport Somewhat. It is also to be understood that the terminology layer CTL). The OPC element must have very uniform and used herein is used for the purpose of describing particular defect-free structural and electrical characteristics. Its usable examples only. The terms are not intended to be limiting lifetime is often determined by the occurrence of physical because the scope of the present disclosure is intended to be defects introduced by mechanical, physicochemical and elec limited only by the appended claims and equivalents thereof. trical interactions between the surface of the CTL and one or 0013. It is noted that, as used in this specification and the more elements of the electrophotographic process (com appended claims, the singular forms “a,” “an and “the monly known as “OPC wear-out”). Some of the proposed include plural referents unless the context clearly dictates Solutions addressing this issue involve coating the CTL Sur otherwise. face with a hard, inorganic film that may significantly raise 0014. As used herein, “about” means a +10% variance the OPC cost and introduce other deleterious effects associ caused by, for example, variations in manufacturing pro ated with the contamination particles originating from the CCSSCS. inorganic coating. (0015. As used herein, “alkyl” refers to a branched, 0002 Alternative solutions have proposed coating the unbranched, or cyclic Saturated hydrocarbon group, which OPC with an organic coating having Superior damage resis typically, although not necessarily, includes from 1 to 50 tance and electrical properties corresponding to the original carbonatoms, or 1 to 30 carbon atoms, or 1 to 6 carbons, for OPC. This might be accomplished by using a mixture of example. Alkyls include, but are not limited to, methyl, ethyl, damage-resistant polymer (matrix) and molecular moieties n-propyl, isopropyl. n-butyl, isobutyl, t-butyl, octyl, and (CTM-charge transport material) providing electrical decyl, for example, as well as cycloalkyl groups such as charge conduction, and coating the original OPC with their cyclopentyl, and cyclohexyl, for example. solvent-based mixture. This solution has not been successful 0016. As used herein, “aryl refers to a group including a due to a lack of appropriate hole-conducting dopants that can single aromatic ring or multiple aromatic rings that are fused be used with a solvent that does not attack the original OPC. together, directly linked, or indirectly linked (such that the All commonly-available hole-CTMs requiresolvents that are different aromatic rings are bound to a common group such as incompatible with polycarbonate, the matrix component for a methylene or ethylene moiety). Aryl groups described most of the commercial OPCs. herein may include, but are not limited to, from 5 to about 50 carbonatoms, or 5 to about 40 carbonatoms, or 5 to 30 carbon BRIEF DESCRIPTION OF THE DRAWINGS atoms or more. Aryl groups include, for example, phenyl, naphthyl, anthryl, phenanthryl, biphenyl, diphenylether, 0003 FIG. 1 is a schematic diagram of an apparatus that diphenylamine, and benzophenone. The term “substituted employs an example organic photoconductor (OPC) drum, in aryl” refers to an aryl group comprising one or more substitu accordance with the teachings herein. ent groups. The term "heteroaryl” refers to an aryl group in 0004 FIG. 1A is an enlargement of a portion of the OPC which at least one carbonatom is replaced with a heteroatom. drum. If not otherwise indicated, the term “aryl' includes unsubsti 0005 FIG.2, on coordinates of normalized absorption and tuted aryl, substituted aryl, and heteroaryl. wavelength (in nm) is an absorption plot of two example 0017. As used herein, “substituted” means that a hydrogen copolymers in Solution. atom of a compound or moiety is replaced by another atom 0006 FIG.3, on coordinates of normalized absorption and Such as a carbon atom or a heteroatom, which is part of a wavelength (in nm) is an absorption plot of two example group referred to as a substituent. Substituents include, but copolymers as a thin film. are not limited to, for example, alkyl, alkoxy, aryl, aryloxy, 10007 FIG.4, on coordinates of V(in volts) and number alkenyl, alkenoxy, alkynyl, alkynoxy, thioalkyl, thioalkenyl, of imprints, is a plot of degradation as the OPC ages, com thioalkynyl, and thioaryl. paring an uncoated and a coated OPC, where the coating is an (0018. The terms “halo' and “halogen” refer to a fluoro, example coating. chloro, bromo, or iodo substituent. 0008 FIG. 5, on coordinates of scratch depth (in um) and 0019. As used herein, “alcohol means a lower alkyl chain load (ing) is a plot of scratch resistance as a function of load, alcohol. Such as methanol, ethanol, n-propanol, iso-propanol, comparing an uncoated and a coated OPC, where the coating n-butanol, iso-butanol, tert-butanol, pentanol, hexanol, and is an example coating. their analogs. A fluorinated alcohol is an alcohol having at US 2014/0322638 A1 Oct. 30, 2014 least one of its alkyl hydrogen atoms replace with a fluorine 0030 The structure of the organic photoreceptor usually atom. A perfluorinated alcohol is an alcohol having all of its has several layers of materials, each of which performs a alkyl hydrogen atoms replaced with fluorine atoms. specific function, such as charge generation, charge transport, 0020. As used herein, a plurality of items, structural ele and occasionally additional Surface protection. These layers ments, compositional elements, and/or materials may be pre are formed by individual sequential coatings. One of these sented in a common list for convenience. However, these lists layers is the charge transport material (CTM) layer, or CTL should be construed as though each member of the list is 126. In this regard, mainly aromatic tertiary amino com individually identified as a separate and unique member. pounds and their corresponding polymers are usually used. Thus, no individual member of such list should be construed Generally, these materials are soluble in common organic as a de facto equivalent of any other member of the same list solvents such as tetrahydrofuran (THF) and dichloromethane solely based on their presentation in a common group without (CH,Cl). Because of their solubility in these solvents, there indications to the contrary. is usually a loss of charge transport material and/or mixing 0021. The organic (OPC) in an electrophotographic with the material that is over-coated on top for protection. In printer is a thin film photoconductive layer. An electrostatic addition, these materials cannot facilitate “fast' transport of latent image is formed on the precharged photoreceptor Sur electrical charges, making them irrelevant for the high-speed face via optical exposure.