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
  • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
  • G03G5/0622—Heterocyclic compounds
  • G03G5/0624—Heterocyclic compounds containing one hetero ring
  • G03G5/0627—Heterocyclic compounds containing one hetero ring being five-membered
  • G03G5/0629—Heterocyclic compounds containing one hetero ring being five-membered containing one hetero atom
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/001—Electric or magnetic imagery, e.g., xerography, electrography, magnetography, etc. Process, composition, or product
  • Y10S430/10—Donor-acceptor complex photoconductor

Definitions

• DIBENZOTHIOPHENE OXIDE OR DIOXIDE SENSITIZERS FOR ORGANIC PHOTOCONDUCTORS [75] Inventors: Gerardus J. Crommentuyn, Lottum;
• the invention relates to an electrophotographic reproduction element, comprising a suitable support with a photoconductive coating layer on it, which contains a donor-acceptor complex, built up of an electron donor having photoor semiconductor properties and an electron acceptor, whereby the acceptor itself also may or may not possess photoconductive properties.
• the invention relates to a process for preparing a photoconductive composition which is suitable for the preparation of an electrophotographic reproduction element according to the above-mentioned composition, whereby a mixture is prepared of an organic electron-donor compound possessing photoor semiconductor properties and an organic electronacceptor compound, by which a donor-acceptor complex is formed and whereby the acceptor itself also may or may not possess photoconductive properties.
• Photoconductive compositions which contain an organic compound as photoconductive element, either monomer or polymer, are generally known.
• monomeric compounds which have been proposed as photo-conductors are: anthracene, phenanthrene, pyrene, perylene, carbazole, substituted carbazole, oxadiazole, substituted oxadiazole and other aromatic, mainly polynuclear compounds with or without one or more hetero atoms in an aromatic ring.
• polymeric compounds which have been proposed as photoconductor in literature are: poly-1 and poly-9- vinylanthracene, polyacenaphthylene, poly-N- vinylcarbazole, as well as their substituted produces such as nitrated or halogenated poly-N-vinylcarbazole, especially poly-3-bromo and poly-3,6-dibromo-N- vinylcarbazole, as well as copolymers, for instance of 3-nitro-N-vinylcarbazole and acenaphthylene.
• the invention makes it possible to enlarge the assortment of acceptors for organic photoconductive donors, especially poly-N-vinylcarbazole.
• the object of the invention is to provide an electro' photographic reproduction element which in practice gives as much satisfaction as the known elements.
• an electrophotographic reproduction element which comprises a suitable sup port with a photoconductive coating layer on it, which layer contains a donor-acceptor complex built up of an electron-donor having photo or semiconductor properties and an electron-acceptor, whereby the acceptor itself may or may not possess photoconductive properties, characterized in that the acceptor is a compound of the formula in which n 1 or 2 and the symbols R and R, which can be the same or different, each represent one or more hydrogen atoms or one or more electronattracting groups, known by themselves.
• n 1 are indicated as dibenzothiofene-5- (mono)-oxides, those in which n 2 as dibenzothiofene-5,5-dioxides.
• the measure of complex-formation will only depend on the acceptor. ln proportion as the electron-affinity (EA) of the acceptor is higher, a quicker and/or stronger complex-formation will occur. lt is supposed that besides the EA factor also other, especially steric, factors play a part in the complex formation, for instance whether donor and acceptor are well fitting to each other, so that they can approach each other so close that their mutual tendency to give away electrons, respectively to pick up electrons, also indeed leads to this result.
• EA electron-affinity
• TNF 2,4,7trinitro-9-fluorenone
• DTF 2,4,7-trinitro-9-dicyanomethylenefluorene
• the invention adds a new class of acceptors, very suitable for the electrophotographic process, to the two already existing classes. Especially in combination with poly-N-vinylcarbazole the compounds of this new class of acceptors yield an electrophotographic reproduction element which, with regard to all properties important for a reproduction element, such as discharge speed in light and dark, memory effect and contrast reproduction, can excellently stand a comparison with the best reproduction elements known so far based on organic photoconductors.
• dibenzothiofene oxides and dioxides may serve as illustration of the acceptors suitable according to the invention:
• the effect of the dioxides is greater than that of the mono-oxides, for which reason the dioxides are preferred.
• the new 1,3,7-trinitrodibenzothiofene-S,S-dioxide which has not yet been described in literature, takes the first place, so that preferably this compound is used as acceptor.
• acceptors can be applied with each electron-releasing photoconductor with which a donor-acceptor complex can be formed.
• the quantity of acceptor added, related to the quantity of photoconductor, can vary within very wide limits.
• the lower limit is determined by that quantity which still exercises an activating effect on the photoconductor. This lower limit appears to lie near the limit of 0,001 mole per 1 mole of photoconductor, as already mentioned in older literature, calculated according to the monomeric unit.
• the upper limit is determined by the solubility of the acceptor in the solvent. This upper limit lies for instance near the mole proportion 1 1 for the combination preferably applied, PVK/1,3,7-trinitrodibenzothiofene-5,5-dioxide.
• the quantities of acceptor preferably applied lie in the range between :02 and 1 mole per mole of photoconductor, calculated according to the monomeric unit.
• the reproduction elements according to the invention are obtained by coating a suitable support with a photoconductive composition containing a donoracceptor complex according to the invention.
• the support can for instance consist of a metal plate or foil, a plastic foil on which a conductive layer is applied or of paper which is either sufficiently conductive by origin, for instance by impregnation in the paper mill with conductive materials, or has been made conductive by providing it with a conductive layer, for instance a layer containing carbon.
• the light-sensitive layer may also contain one or more photoconductors and/or one or more light-sensitivity increasing compounds.
• a binding agent can be added for that purpose.
• photoconductive layers consisting of PVK/1,3,7- trinitro-dibenzothiofene-5,5-dioxide in the mole proportion of about 1 1 to about 1, if negatively charged, are clearly more sensitive than when they have been charged positively.
• proportions of about 10 l to 25 1 the layers are in both cases almost equally sensitive, whereas layers in which the proportion donor acceptor is greater than about 25 1, when positively charged, are more sensitive than when they have been charged negatively.
• the thickness of the photoconductive layers is not critical and can vary within fairly wide limits. In general a thickness of 3-10 ,u. is already sufficient to yield layers which are suitable for practical use, but also thicker layers, for instance of ,u, are suitable.
• the reproduction elements according to the invention can be used both in the direct and in the indirect electrophotographic process.
• the latent image formed on the reproduction element is developed and fixed.
• the latent image is first transferred onto a receiving material, such as pa per, and is developed and fixed on it, or is first devel oped after which the loose powder image is transferred to a receiving material and is fixed on it.
• the invention further relates to a process for the preparation of a photoconductive composition suitable for the manufacture of a reproduction element as herein set forth, whereby a mixture is prepared of an organic electron donor compound which has photoof semiconductor properties and an organic electron acceptor compound, by which a donor-acceptor complex is formed, whereby the acceptor itself may or may not possess photoconductive properties.
• This process is characterized by the fact that as acceptor a compound of the above formula Inn is taken, in which n 1 or 2 and the symbols R and R, which may be the same or different, each represent one or more hydrogen atoms or one or more electron attracting groups known by themselves.
• the preparation of these new acceptors isrealized with the aid of reactions which are usual in organic chemistry.
• the mono-oxides can be prepared by oxidation with chlorine in carbon tetrachloride, as described in J. Am. Chem. Soc. 70, 1748 (1948), after which by nitration the monoand dinitrocompounds are produced.
• the dioxides can be synthetized by allowing dibenzothiofene to oxidize with a mixture of sulfuric acid and dichromate. By means of nitration the mono, dior trinitro compound can be obtained.
• the dibenzothiofene from which one starts does not yet carry a halogensubstituent
• this can be introduced in the dioxide by first introducing a nitrogroup, be reducing this, by diazotizing, and subsequently by replacing the diazoniumsalt group by a halogen group with a Sandmeyer reaction.
• Introduction of a cyano group takes place in an analogous way.
• Compounds carrying mixed substituents for instance nitroand halogen
• the reproduction element thus obtained was charged under a positive corona of 7 kV to about 200 V, then it was imagewise exposed under an enlarging apparatus during 2 seconds with a glow lamp, whereby the quantity of light on the irradiated areas amounted to 40 lux, and finally it was developed, for instance with a powdery toner.
• This loose powder image could both be fixed on the plate itself and could also first be transferred to a receiving material, such as paper, and be fixed on this. In both cases an excellent image was obtained.
• EXAMPLE IV With the aid of a solution of poly-N-vinylcarbazole and 3,7-dibromo-1,9-dinitro-dibenzothiofene-S,5- dioxide, in which the proportion donor acceptor was 20 1, an aluminium support was coated with a lightsensitive layer having a thickness of 2-3 p.. The number of lux sec., required to reduce the initial potential of 500 V to 125 V 25 upon exposure with a glowlamp amounted to 215 lux sec. for a plate charged negatively and 180 lux sec. for a plate charged positively.
• EXAMPLE V An aluminium support was provided with a lightsensitive layer having a thickness of 3 ,u, which contained poly-N-vinylcarbazole as donor and 3,7-dinitrodibenzothiofene-5oxide as acceptor in the molar proportion 1.
• the reproduction-element thus obtained was charged by means of a negative corona to about 400 V.
• the 70 light-sensitivity of this layer was 350 lux-sec.
• Electrophotographic reproduction element comprising a support having thereon a photoconductive coating layer containing an organic photoconductive compound that is an electron donor and an organic electron acceptor that forms a donor-acceptor complex with said donor, said acceptor being present in a ratio of between 0.001 and 1 mol thereof per mol of said donor calculated as a monomer, and being a compound of the formula in which n l or 2 and R and R, which may be the same or differentQeach represents one or more hydrogen atoms or one or more substituents selected from the group consisting of halogen atoms and nitro and cyano groups and at least one of R and R represents one or more of said substituents.
• Electrophotographic reproduction element in which at least one of R and R represents one or more nitro groups.
• Electrophotographic reproduction element according to claim 1 in which n 2.
• Electrophotographic reproduction element according to claim 1, said acceptor being 1, 3, 7-trinitrodibenzothiofene-5,5-dioxide.
• Electrophotographic reproduction element said photoconductive compound being selected from the group consistingvof a poly-N- vinyl carbazole, monomeric carbazole compounds, 2,5- bis (4-diaminophenyl)-l,3,4-oxadiazole, 2,5-bis (4- dialkylaminophenyl)-l,3,4-oxadiazole and poly-9-vinyl anthracene.
• Electrophotographic reproduction element according to claim 1, said photoconductive compound being poly-N-vinyl carbazole and said acceptor being 1,3,7-trinitrodibenZothiofene-S,5-dioxide.
• Electrophotographic reproduction element containing from about 1 to about 10 mols of said carbazole per mol of a said acceptor, whereby said element is more light-sensitive when negatively charged than when positively charged.
• Electrophotographic reproduction element containing from about 10 to about 25 mols of said carbazole per mol of said acceptor, whereby said element is approximately equally light sensitive when either negatively or positively charged.
• Electrophotographic reproduction element containing more than about 25 mols of said carbazole per mol of said acceptor, whereby said element is more light-sensitive when positively charged than when negatively charged.
• Electrophotographic reproduction element said layer having a thickness of about 3 to 10 microns, said photoconductive compound being poly-N-vinyl carbazole, said acceptor being 1,3,7-trinitro-dibenzothiofene-S,5-dioxide, and said layer containing from about 1 to about 10 mols of said carbazole per mol of said acceptor.
• Photoconductive composition for use in a coating layer of an electrophotographic reproduction element comprising in admixture an organic photoconductive compound that is an electron donor and, per mol of said donor calculated as a monomer, between 0.001 and 1 mol of an organicelectron acceptor that forms a donor-acceptor complex with said donor, said acceptor being a compound of the formula in which n l or 2 and R and R, which may be the same or different, each represents one or more hydrogen atoms or one or more substituents selected from the group consisting of halogen atoms and nitro and cyano groups and at least one of R and R represents one or more of said substituents.
• Photoconductive composition accordingto claim 11, said photoconductive compound being selected from the group consisting of poly-N-vinyl carbazole, monomeric carbazole compounds, 2,5-bis(4 diaminophenyl)-1,3,4-oxadiazole, 2,5-bis(4-dialkylaminophenyl)-1,3,4-oxadiazole and poly-9-vinyl anthracene.
• Photoconductive composition according to claim 11 said acceptor being 1,3,7-trinitrodibenzothiofene- 5,5-dioxide.
• Photoconductive composition according to claim 11 said photoconductive compound being poly-N- vinyl carbazole and said acceptor being 1,3,7-
• Photoconductive composition according to claim mols of said photoconductive compound being present per mol of said acceptor.
• said photoconductive compound being poly-N- viny] carbazole, said acceptor being 1,3,7-

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Citations (8)

• 1972
  • 1972-09-15 NL NL7212511A patent/NL168059C/nl not_active IP Right Cessation
• 1973
  • 1973-09-05 US US394458A patent/US3905814A/en not_active Expired - Lifetime
  • 1973-09-14 GB GB4335373A patent/GB1443449A/en not_active Expired
  • 1973-09-14 FR FR7333068A patent/FR2200553B1/fr not_active Expired
  • 1973-09-14 JP JP48104489A patent/JPS5833548B2/ja not_active Expired
  • 1973-09-14 GB GB2891874A patent/GB1443450A/en not_active Expired
  • 1973-09-15 DE DE19732346536 patent/DE2346536A1/de not_active Ceased

Patent Citations (8)

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