US3679408A - Heterogeneous photoconductor composition formed by two-stage dilution technique - Google Patents

Heterogeneous photoconductor composition formed by two-stage dilution technique Download PDF

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US3679408A
US3679408A US89448A US3679408DA US3679408A US 3679408 A US3679408 A US 3679408A US 89448 A US89448 A US 89448A US 3679408D A US3679408D A US 3679408DA US 3679408 A US3679408 A US 3679408A
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dye
solvent
dope
polymer
photoconductive
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Frederick J Kryman
William J Staudenmayer
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Eastman Kodak Co
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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
    • G03G5/02—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
    • G03G5/0557—Macromolecular bonding materials obtained otherwise than by reactions only involving carbon-to-carbon unsatured bonds
    • G03G5/0564—Polycarbonates
    • 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
    • G03G5/0557—Macromolecular bonding materials obtained otherwise than by reactions only involving carbon-to-carbon unsatured bonds
    • 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
    • G03G5/0557—Macromolecular bonding materials obtained otherwise than by reactions only involving carbon-to-carbon unsatured bonds
    • G03G5/056—Polyesters

Definitions

  • the dye used is dissolved in a solvent at a dye/ solvent ratio substantially equal to the solubility limit of the dye.
  • Polymeric binder and photoconductor are added and the additional solvent is added to substantially reduce the dye/solvent ratio well below the solubility limit.
  • a highspeed heterogeneous composition results.
  • One type of photoconductive insulating structure or element particularly useful in electrophotography utilizes a composition containing a photoconductive insulating material dispersed in a resinous material.
  • a unitary electrophotographic element is generally produced in a multilayer type of structure by coating a layer of the photoconductive composition onto a film support previously overcoated with a layer of conducting material or the photoconductive composition may be coated directly onto a conducting support of metal or other suitable conducting material.
  • Such photoconductive compositions have shown improved speed and/or spectral response, as well as other desired electrophotographic characteristics when one or more photosensitizing materials or addenda are incorporated into the photoconductive composition. Typical addenda of this latter type are disclosed in U.S. Pat. Nos.
  • photosensitizing addenda to photoconductive compositions are incorporated to effect a change in the sensitivity or speed of a particular photoconductor system and/or a change in its spectral response characteristics.
  • Such ic response of the photoconductor should be capable of reproducing the wide range of colors which are typically 3,679,408 Patented July 25, 1972 encountered in such use. If the response of the photoconductor falls short of these design criteria, it is highly desirable if the spectral response of the composition can be altered by the addition of photosensitizing addenda to the composition.
  • the method of this invention is used to form heterogeneous multiphase photoconductive compositions comprised of an organic sensitizing dye and an electrically insulating, film-forming polymeric material.
  • the present method is relatively uncomplicated and provides results which are readily reproducible and which are relatively independent of the crystalline structure of the particular dye or dyes used.
  • One of the essential features of the instant invention is the dissolution of the sensitizing dye in a suitable solvent at a dye-to-solvent ratio substantially equal to the solubility limit of the dye. This is done prior to the addition of any other add'enda. After dissolving the dye, the polymeric material is subsequently added with suitable stirring to dissolve the polymer. Additional solvent is then added to substantially reduce the dye-to-solvent ratio well below the solubility limit of the dye.
  • the heterogeneous nature of which is generally apparent when viewed under 2500 magnification, although such compositions may appear to be substantially optically clear to the naked eye in the absence of magnification.
  • the dye-containing aggregate in the discontinuous phase is submicron in size and is predominantly in the size range of about 0.01 to about 0.75 micron.
  • the heterogeneous compositions prepared by this invention are used to sensitize a particulate photoconductor, such as zinc oxide, another discontinuous phase will be present which may not fall within this size range.
  • the heterogeneous compositions formed by the present method are multiphase organic solids.
  • the polymer vehicle comprises an amorphous matrix or continuous phase which contains a discrete discontinuous phase as distinguished from a solution.
  • the discontinuous phase is the aggregate species which is a co-crystalline complex comprised of dye and polymer.
  • coci'ystalline complex as used herein has reference to a crystalline compound which contains dye and polymer molecules co-crystallized in a single crystalline structure 4 to form a regular array of the molecules in a three di mensional pattern.
  • the resultant photoconductive composition generally contains only two phases as the photoconductor usually forms a solid solution with the continuous polymer phase.
  • the present multiphase compositions are used in conjunction with a particulate photoconductor, three phases may be present. In such a case, there would be a continuous polymer phase, a discontinuous phase containing the aggregate as discussed above and another discontinuous phase comprised of the particulate photoconductor.
  • the present multiphase compositions may also contain additional discontinuous phases of trapped impurities, etc.
  • Another feature characteristic of the heterogeneous compositions formed in accordance with this invention is that the wavelength of the radiation absorption maximum characteristic of such compositions is substantially shifted from the wavelength of the radiation absorption maximum of a substantially homogeneous dye-polymer solid solution formed of similar constituents.
  • the new absorption maximum characteristic of the aggregates formed by this method is not necessarily an overall maximum for this system as this will depend upon the relative amount of dye in the aggregate.
  • Such an absorption maximum shift in the formation of multiphase heterogeneous systems for the present invention is generally of the magnitude of at least about 10 nm. It mixtures of dyes are used, one dye may cause an absorption maximum shift to a long wavelength and another dye cause an absorption maximum to a shorter wavelength. In such cases, a formation of the heterogeneous compositions can more easily be identified by viewing under magnification.
  • Sensitizing dyes and electrically insulating polymeric materials are used in forming these heterogeneous compositions.
  • pyrylium dyes including pyrylium, thiapyrylium and selenapyrylium dye salts are useful in wherein R R R R and R can each represent (a) a hydrogen atom; (b) an alkyl group typically having from 1 to 15 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl, amyl, isoamyl, hexyl, octyl, nonyl, dodecyl, etc., (c) alkoxy groups like methoxy, ethoxy, propoxy, butoxy, amyloxy, hexoxy, octoxy, and the like; and (d) aryl groups including substituted aryl groups such as phenyl, 4-diphenyl, alkylphenyls
  • R and R when taken separately, can each be a hydrogen atom, an alkyl radical having from one to about carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, tertiary butyl, pentyl, 'hexyl, heptyl, octyl, nonyl, decyl and the like, including substituted alkyl radicals such as trifiuoromethyl, etc., and an aryl radical such as phenyl and naphthyl, including substituted aryl radicals having such substituents as a halogen, alkyl radicals of from 1 to about 5 carbon atoms, etc.; and R and R when taken together, can represent the carbon atoms necessary to form a cyclic hydrocarbon radical including cycloalkanes such as cyclohexyl and polycyclo- :alkanes such as norbornyl the total number of carbon atoms in R and R being up
  • R and R can each be hydrogen, an alkyl radical of from 1 to about 5 carbon atoms, e.g., methyl, ethyl, isopropyl, butyl, amyl, etc., or a halogen atom such as chloro, bromo, iodo, etc.; and
  • R is a divalent radical selected from the following:
  • each R is a phenylene radical including halo substituted phenylene radicals and alkyl substituted phenylene radicals and alkyl substituted phenylene radicals; and R and R are as described above.
  • Such compositions are disclosed, for example, in U.S. Pat. Nos. 3,028,365 by Schnell et al., issued Apr. 3, 1962 and 3,317,466 by Caldwell et al., issued May 2, 1967.
  • polycarbonates containing an alkylidene diarylene moiety in the recurring unit such as those prepared with Bisphenol A and including polymeric products of ester exchange between diphenylcarbonate and 2,2-bis(4-hydroxypheuyl)propane are useful in the practice of this invention.
  • compositions are disclosed in the following U.S. Patents: 2,999,750 by Miller et al., issued Sept. 12, 1961; 3,038,874 by Laakso et al., issued June 12, 1962; 3,038,879 by Laakso et al., issued June 12, 1962; 3,038,880 by Laakso et al., issued June 12, 1962; 3,106,544 by Laakso et al., issued Oct. 8, 1963; 3,106,545 by Laakso et al., issued Oct. 8, 1963; 3,106,546 by Laakso et al., issued Oct. 8, 1963; and published Australian patent specification No. 19,575/56.
  • a wide range of film-forming polycarbonate resins are useful, with completely satisfactory results being obtained when using commercial polymeric materials which are characterized by an inherent viscosity of about 0.5 to 0.6.
  • a high molecular weight material such as a high molecular weight Bisphenol A polycarbonate can be very useful.
  • such high molecular weight materials have an inherent viscosity of greater than about 1 as measured in 1,2-dichloroethane at a concentration of 75 0.25 g./ ml. and a temperature of about 25 C.
  • the use of high molecular weight polycarbonate facilitates the formation of aggregate compositions having increased speeds.
  • Sensitized compositions formed according to the present invention can readily be used for enhancing the sensitivity and extending the spectral range of sensitivity of a variety of organic photoconductors and inorganic photoconductors including both nand p-type photoconductors.
  • a typical example of an inorganic photoconductor would be zinc oxide.
  • the present invention can be used in connection with many organic, including organometallic, photoconducting materials which having little or substantially no persistence of photoconductivity.
  • Representative organo-metallic compounds are the organic derivatives of Group Illa, IVa, and Va metals such as those having at least one aminoaryl group attached to the metal atom.
  • organo-metallic compounds are the triphenylp-dialkylaminophenyl derivatives of silicon, germanium, tin and lead, the tri-p-dialkylaminophenyl derivatives of arsenic, antimony, phosphorus, bismuth boron, aluminum, gallium, thallium and indium.
  • Useful photoconductors of this type are described in copending Goldman and Johnson U.S. pat. application Ser. No. 650,664, filed July 3, 1967 and Johnson application Ser. No. 755, now U.S. Pat. No. 3,607,257, filed Aug. 27, 1968.
  • organic photoconductors An especially useful class of organic photoconductors is referred to herein as organic amine photoconductors.
  • Such organic photoconductors have as a common structural feature at least one amino group.
  • Useful organic photoconductors which can be spectrally sensitized in accordance with this invention include, therefore, arylamine, compounds comprising (1) diarylamines such as diphenylamine, dinaphthylamine, N,N-diphenylbenzidine, N- phenyl-l-naphthylamine, N-phenyl-Z-naphthylamine, N, 'N-diphenylp-phenylenediamine, 2-carboxy-5 chloro-'4'- methoxydiphenylamine, p-anilinophenol, N,N'-di-2-naphthyl-p-phenylenediamine, those described in Fox U.S. Pat.
  • triarylamines including (a) nonpolymeric triarylamines, such as triphenylamine, N,N,N,Ntetraphenyl-m-phenylenediamine, 4-acetyltriphenylamine, 4-hexanoyltriphenylamine, 4-lauroyltriphenylamine, 4-hexyltriphenylarnine, 4- dodecyltriphenylamine, 4,4-bis(diphenylamino)benzil, 4, 4-bis(diphenylamino)benzophenoneand the like, and (b) polymeric triarylamines such as poly[N,4"-(N,N, N'-triphenylbenzidine)], polyadipyltriphenylamine, polysebacyltriphenylamine, polydecamethylenetriphenylamine, poly-N-(4 vinylphenyl)diphenylamine, poly N (vinylphenylphenyl)
  • T represents a mononuclear or polynuclear divalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group naving from 1 to about 6 carbon atoms (e.g., acetyl, propiouyl, butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, pentogy, etc.), or a nitro group; M represents a mononuclear or polynuclear 'monovalent aromatic radical, either fused or linear (e.g., phenyl, naph
  • phenyl phenyl, naphthyl, biphenyl, etc.
  • a substituted aromatic radical wherein said substituent comprises an alkyl group, an alkoxy group, an acyl group, or a nitro group, or a poly(4'-vinylphenyl) groupwhich is bonded to the nitrogen atom by a carbon atom of the phenyl group.
  • Polyarylalkane photoconductors are particularly useful in producing the present invention. Such photoconductors are described in US. Pat. 3,274,000 by Noe et al., issued Sept. 20, 1966, French Pat. 1,383,461 and in copending application of Seus and Goldman titled Photoconductive Elements Containing Organic Photoconductors, Ser. No. 627,857, now U.S. Pat. No. 3,542,544 filed Apr. 3, 1967.
  • photoconductors include leuco bases of diaryl or triaryl methane dye salts, 1,1,l-triarylalkanes wherein the alkaue moiety has at least two carbon atoms and tetraarylmethanes, there being substituted an amine group on at least one of the aryl groups attached to the alkane and methane moieties of the latter two classes of photoconductors which are non-leuco base materials.
  • Preferred polyarylalkane photoconductors can be represented by the formula:
  • each of D, E and G is an aryl group and J is a hydrogen atom, an alkyl group, or an aryl group, at least one'of D, E and G containing an amino substituent.
  • the aryl groups attached to the central carbon atom are preferably phenyl groups, although naphthyl groups can also be used. Such aryl groups can contain such substituents as alkyl and alkoxy typically having 1 to 8 carbon atoms, liydroxy, halogen, etc., in the ortho, meta or para positions, ortho-substituted phenyl being preferred.
  • the aryl groups can also be joined together or cyclized to form a fluorene moiety, for example.
  • the amino substituent can be represented by the formula:
  • each L can be an alkyl group typically having 1 to 8 carbon atoms, a hydrogen atom, an aryl group, or together the necessary atoms to form a heterocyclic amino group typically having 5 to 6 atoms in the ring such as morpholino, pyridyl, pyrryl, etc.
  • At least one of D, E and G is preferably p-dialkylaminophenyl group.
  • I is an alkyl group, such an alkyl group more generally has 1 to 7 carbon atoms.
  • Representative useful polyarylalkane photoconductors include the compounds listed in Table 3.
  • photoconductors useful in this invention are the 4-diarylamino-substituted chalcones.
  • Typical compounds of this type are low molecular weight nonpolymeric ketones having the general formula:
  • R and R are each phenyl radicals including substituted phenyl radicals and particularly when R is a phenyl radical having the formula:
  • R and R are each aryl radicals, aliphatic residues of l to 12 carbon atoms such as alkyl radicals preferably having 1 to 4 carbon atoms or hydrogen. Particularly advantageous results are obtained when R is a phenyl radical including substituted phenyl radicals and where R is diphenylaminophenyl, dimethylaminophenyl or phenyl.
  • photoconductors which can be used with the present aggregate compositions include rhodamine B, malachite green, crystal violet, phenosafranine, cadmium sulfide, cadmium selenide, parachloronil, benzil, trinitrofluorenone, tetranitrofluorenone, etc.
  • photoconductor In preparing photoconductive comopsitions in accordance with this invention, useful results are obtained when the photoconductor is present in an amount equal to at least about /2% by weight of total solids added to the coating solvent.
  • the upper limit of the amount of photoconductor present can be varied widely with up to 99% by weight of total solids being useful.
  • a preferred weight range for the photoconductor is from about to about 80 weight percent.
  • polymeric photoconductors e.g., poly(N-vinylcarbazole), halogenated poly(N-vinylcarbazole), etc., can also be used if desired.
  • a pyrylium dye as hereinbefore defined is dissolved in a suitable organic solvent, up to a predetermined concentration.
  • the limit of concentration is deter-mined by the solubility of the dye in the dope resulting when the accompanying polymer is dissolved in the dye-containing solution.
  • the amount of dye thus dissolved may be any amount from the solubility limit to about ten percent less than the solubility limit of the dye in the dope as above. It may be a greater or lesser amount than the amount which would dissolve in the solvent alone in the absence of polymer or other addendum, such as, for example, photoconductor, coating aid, and the like.
  • the solubility limit of the dye in any dope will be dependent upon the particular materials present in the dope and their concentrations.
  • Solvents useful for preparing the dye-containing dope or compositions and elements to be coated therefrom in accordance with this invention can include a number of solvents such as aromatic hydrocarbons, e.g., benzene, toluene, including halogenated aromatic solvents such as chlorobenzene, dichlorobenzene, etc.; ketones such as dialkyl ketones having 1 to about 3 carbon atoms in the alkyl moiety, e.g., dimethyl ketone, methylethyl ketone, etc.; chlorinated hydrocarbons such as dichloroalkanes having 1 to about 3 carbon atoms, e.g., methylene chloride, ethylene chloride, trimethylene chloride, etc.; ethers, such as tetrahydrofuran, etc.; and mixtures of these and other solvents.
  • solvents such as aromatic hydrocarbons, e.g., benzene, toluene, including halogenated aromatic solvents such as
  • the hydrophobic polymer is dissolved in the solution.
  • Mild stirring can be applied, if desired, to facilitate thorough mixing of the dissolved dye and polymer in the dope. Times of stirring can vary widely, with up to about 24 hours being employed if required. In general, the time required to dissolve the dye is somewhat longer than the time required to dissolve the polymer in the dye-containing solution. If necessary or desirable, a photoconductor can also be added at this stage, as can any other addendum which it is desired to incorporate.
  • the concentrated dope containing dye and dissolved polymer is next diluted to well below the solubility limit of the dye.
  • the solvents used for diluting the dope are generally the same as are used in preparing the initial dye solution and polymer-containing dope produced therefrom, although it may be desirable in certain instances or even preferred to use difierent solvents.
  • the amount of solvent added can vary widely depending upon the final solids content desired in the dope from which an electrophotographic element is to be prepared. In general, the amount added is between about 25 and about 100% by weight of the amount used in preparing the initial solution of dye.
  • further polymer or dye may be added to give the desired proportion of dye ot photoconductor in the coating dope, and at the same time to adjust the solids content.
  • the total solids content of the resultant coating dope is about 10 to about 20% by weight of the dope.
  • the total dye concentration is typically from about 0.5 to about 20% by weight of the total solids.
  • the dye concentration of the final dope is preferably in the range in j ⁇ f/ ll l l I
  • D represents the ratio of dye to solvent, with values increasing the upward direction.
  • P represents the ratio of polymer to solvent, with values increasing to the right.
  • the dye is added to the solvent in an amount within about 10% of the solubility limit of the dye. This results in a ratio D of dye to solvent.
  • the polymer and other ingredients are then added, resulting in a value of P, for example, P P or P which is not critical.
  • D is at least about 25% below the solubility limit of the dye in the dope.
  • P the value of P at the first dilution stage can vary widely as shown by points 0, 1, 2 and 3.
  • the arrows starting from points 1 and 2 indicate addition of polymer is required, along with the solvent, in the second stage dilution to reach the desired polymer/ solvent ratio at X.
  • the arrow from point 2 could likewise represent dilution with a polymercontaining dope having the concentration contained in the starting dope. This would reduce dye concentration only, leaving polymer concentration unaffected.
  • the arrow from point 3 could result from the addition of solvent alone, as such addition would reduce the concentration of both dye and polymer in the solution.
  • the final value of P after the second stage dilution will depend on that desired or required in the final composition.
  • the sensitizer-containing photoconductive dope thus prepared is next formed into an electrophotographic element by coating the dope onto a conductive support by.
  • Suitable supporting materials for coating sensitizer-containing photoconductive layers in accordance with the method of this invention can include any of a wide variety of electrically conducting supports, for example, paper (at a relative humidity above 20% aluminum-paper laminates; metal foils such as aluminum foil, zinc foil, etc; metal plates, such as aluminum, cop per, zinc, brass and galvanized plates; vapor deposited metal layers such as silver, nickel, aluminum and the like coated on paper or conventional photographic film bases such as cellulose acetate, polystyrene, etc.
  • Such conducting materials as nickel can be vacuum deposited on transparent film supports in sufiiciently thin layers to allow electrophotographic elements prepared therewith to be exposed from either side of such elements.
  • An especially useful conducting support can be prepared by coating a support material such as poly(ethylene terephthalate) with a conducting layer containing a semiconductor dispersed in a resin or vacuum deposited on the support.
  • a suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer.
  • Coating thicknesses of the photoconductive composition on the support can vary widely. Normally, a coating in the range of about microns to about 300 microns before drying is useful for the practice of this invention. The preferred range of coating thickness is found to be in the range from about SOmicrons to about 150 microns before drying, although useful results can be obtained outside of this range. , The resultant dry thickness of the coating is preferably between about 2 microns and about 50 microns, although useful results can be obtained with a'dry coating thickness between about 1 and about 200 microns.
  • drying conditions should be reasonably well controlled.
  • temperature and air flow are preferably adjusted so that not over about 80% of the solvent has been removed after about seconds after coating.
  • the photoconductive elements prepared according to the method of this invention can be employed in any of the well-known electrophotographic processes which require photoconductive layers.
  • One such process is the xerographic process.
  • an electrophotographic element is held in the dark and given a blanket electrostatic charge by placing it under a corona discharge. This uniform charge is retained by the layer because of the substantial dark insulating property ofthe layer, i.e., the low conductivity of the layer in the dark.
  • the electrostatic charge formed on the surface of the photoconductive layer is then selectively dissipated from the surface of the layer by imagewise exposure to light by means of a conventional exposure operation such as, for exaample, by a contact-printing technique, or by lens :projection of an image, and the like, to thereby form a latent electrostatic image in the photoconductive layer.
  • Exposing the surface in this manner forms a pattern of electrostatic charge by virtue 'of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be con ducted away from the surface in proportion to the intensity of the illumination in a particular area.
  • the charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charged or uncharged areas rendered visible, by treatment with a medium comprising electrostatically responsive particles having optical density.
  • the developing electrostatically responsive particles can be in the form of a dust, i.e., powder, or a pigment in a resinous carrier, i.e., toner.
  • a preferred method of applying such toner to a latent electrostatic image for solid area development is by the use of a magnetic brush. Methods of forming and using a magnetic brush toner applicator are described in the following U.S. patents: 'Young 2,786,439, issued Nov. 18, 1952; Giaimo 2,786,440, issued Mar.
  • Liquid development of the latent electrostatic image may also be used.
  • the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier.
  • Methods of development of this type are widely known and have been described in the patent literature, for example, U.S. Pat. 2,907,674 by Metcalfe et al., issued Oct. 6, 1959 and in Australian Pat. 212,315.
  • the most widely used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a low melting resin. Heating the powder image then causes the resin to melt or fuse into or onto the element.
  • the powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer.
  • a transfer of the electrostatic charge image formed on the photoconductive layer can be made to a second support such as paper which would then become the final print 14 after development and fusing.
  • Techniques of the type indicated are well known in the art.
  • EXAMPLE 1 A 0.3 gram portion of the dye 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium fluoroborate is dissolved with stirring in a solvent mixture comprising 24.0 grams of dichloromethane and 16.0 grams of 1,1,2-trichloroethane. After addition of the dye is complete, the solution is stirred for 16 hours to ensure complete dissolution. This concentration of dye is about 95% of the solubility limit of the dye in the dope resulting when the resin and photoconductor are added in the next step.
  • the ratio of sensitizer to solvent is reduced to 0.0053, or 71% of the solubility limit of the dye in the dope, and the ratio of resin to solvent is reduced to 0.106.
  • the percent solids, originally 20.5%, is reduced to 15.4% by the addition of this amount of solvent.
  • the composition is coated at a wet thickness of 75 microns on a conductive support comprising poly(ethylene terephthalate) bearing a layer of nickel coated by evaporation in vacuum to an optical density of about 0.4. After drying, the resultant electrophotographic element is then electrostatically charged under a positive corona source until the surface potential, as measured by an electrometer probe, reaches about 600 volts.
  • the charged element is then imagewise exposed to a pattern of light and shadow to produce an electrostatic charge pattern thereon corresponding to the light pattern.
  • the charge pattern is rendered visible by contacting the charged surface with a developer comprising electroscopic marking particles having optical density.
  • a good reproduction of the light pattern results.
  • a second coating composition is prepared in the identical manner, except that the entire quantity of solvent used to prepare the above composition is present when the dye is initially dissolved.
  • the composition is coated as above to prepare a control element.
  • the control when charged, imagewise exposed and developed as above, also gives a good reproduction. When inspected visually, the two elements appear similar in color to the unaided eye, but the element prepared by the method of this invention appears to have a glossy finish, while the control element appears to have a matte finish.
  • Example 2 The procedure of Example 1 is repeated, using the same initial quantities of solvents, and dissolving therein 0.51 gram of the dye 2-(4-ethoxypheny1)-4-(dimethylaminophenyl)-6-phenylthiapyrylium perchlorate. This concentration of the dye is about of the solubility limit of the dye in the dope resulting when the resin and photoconductor are added in the next step. After stirring, 10.30 grams of the resin and 6.70 grams of the photoconductor of Example 1 are added in the manner described therein. The ratio of sensitizer to solvent is 0.0127, and the ratio of resin to solvent is 0.258.
  • the dope is allowed to stand as in Example 1 and then diluted by the addition of 35.50 grams of dichloromethane and 23.50 grams of 1,1,2-trichloroethane.
  • the ratio of sensitizer to solvent is reduced to 0.0053, or 58% of the solubility limit of the dye in the dope and the ratio of resin to solvent is reduced to 0.106.
  • the percent solids, originally 22.1%, is reduced to 15.4% by the addition of solvent.
  • An element is prepared as in Example 1 using the dope prepared herein, and a similar element is prepared using the same quantities of ingredients but without the two-stage dilution technique of the invention. Each element is charged as in Example 1 and exposed to a 3000 K. tungsten light source through a stepped density gray scale.
  • the exposure causes reduction of the surface potential of the element under each step of the gray scale from its initial potential, V0, to some lower potential, V, whose exact value depends on the actual amount of exposure in meter-candleseconds received by the area.
  • V initial potential
  • V some lower potential
  • the results of these measurements are then plotted on a graph of surface potential V vs. log exposure for each step.
  • the relative speed of the photoconductive composition can then be expresed in terms of the reciprocal of the exposure required to reduce the surface potential to any fixed arbitrarily selected value.
  • the relative speed is a function of the reciprocal of the exposure in meter-candle-seconds required to reduce the "600 volt charged surface potential by 100 volts.
  • the relative positive speeds of the element prepared according to the method of the invention and of the control are 500 and 7, respectively, while the corresponding relative negative speeds are 200 and 5.5, respectively.
  • the spectral absorption peak of the element prepared according to the method of this invention is 685 nm.
  • Cross-section photomicrographs at a magnification of 25 clearly show the presence of submicron-sized aggregates in the element prepared according to the invention, while no such small aggregates are observed in the control element.
  • said dye is selected from the group consisting of a thiapyrylium dye salt, a selenapyrylium dye salt and a pyrylium dye salt.
  • discontinuous phase consists of particles of the co-crystalline complex predominantly in the size range of about 0.01 to about 0.75 micron.
  • a method of preparing from a coating dope a heterogeneous photoconductive composition comprising a photoconductor and a co-crystalline complex of a pyrylium dye and a polymer containing the following moiety in the recurring unit:
  • each of R and R when taken separately is selected from the group consisting of a hydrogen atom, an alkyl radical of from 1 to 10 carbon atoms and a phenyl radical and R and R when taken together, are the carbon atoms necessary to form a cyclic hydrocarbon radical, the total number of carbon atoms in R and R being up to 19;
  • R and R are each selected from the group consisting of hydrogen, alkyl radicals of from 1 to 5 carbon atoms, alkoxy radicals of from 1 to 5 carbon atoms and a halogen;
  • R is selected from the group consisting of divalent radicals having the formulae:
  • R and R are aryl radicals selected from the group consisting of phenyl and substituted phenyl having at least one substituent selected from the group consisting of an alkyl radical of from 1 to 6 carbon atoms and an alkoxy radical of from 1 to 6 carbon atoms;
  • R is an alkylamino-substituted phenyl radical having from 1 to 6 carbon atoms in the alkyl moiety;
  • X is selected from the group consisting of sulfur and oxygen
  • Z- is an anion
  • said dye is selected from the group consisting of perchlorate, fluoroborate and p-toluenesulfonate salts of an anion selected from the group consisting of 4-[4-bis(2-chloroethyl)aminophenyl]2,6-diphenylthiapyrylium, 4-(4-dimetyhlaminophenyl)-2,6-diphenylthiapyrylium, 2,6-bis(4-ethylphenyl)-4-(4-dimethylaminophenyl) thiapyrylium,
  • the solvent is selected from the group consisting of dialkyl ketones, aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents and ethers.

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  • Photoreceptors In Electrophotography (AREA)
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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3973962A (en) * 1974-05-02 1976-08-10 Eastman Kodak Company Aggregate photoconductive composition containing combination of pyrylium dye salts
US4167412A (en) * 1976-08-02 1979-09-11 Eastman Kodak Company Pyrylium sensitizers for photoconductive compositions
US4341894A (en) * 1978-03-13 1982-07-27 Eastman Kodak Company Sensitizers for photoconductive compositions
US4419460A (en) * 1980-12-22 1983-12-06 Monsanto Company Phenolic foams
US4663260A (en) * 1985-09-05 1987-05-05 Fuji Photo Film Co., Ltd. Electrophotographic light-sensitive material comprising organic photoconductor and pyrylium sensitizer
US4774250A (en) * 1987-04-02 1988-09-27 Dana Farber Cancer Institute Composition and method for treating differentiated carcinoma or melanoma cells with thiapyrylium dyes
US5240802A (en) * 1991-12-31 1993-08-31 Eastman Kodak Company Aggregate photoconductive element and method of making same
US20100068640A1 (en) * 2006-08-23 2010-03-18 Noriyoshi Ogawa Binder resin for photosensitive layers and electrophotographic photoreceptor belts

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1153195A (en) * 1980-01-11 1983-09-06 Eastman Kodak Company Preparation of heterogeneous photoconductive composition containing a thiopyrilium dye in a blend of aggregating and non-aggregating polymers
US4840860A (en) * 1988-03-16 1989-06-20 Eastman Kodak Company Multiactive electrophotographic element

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3973962A (en) * 1974-05-02 1976-08-10 Eastman Kodak Company Aggregate photoconductive composition containing combination of pyrylium dye salts
US4167412A (en) * 1976-08-02 1979-09-11 Eastman Kodak Company Pyrylium sensitizers for photoconductive compositions
US4341894A (en) * 1978-03-13 1982-07-27 Eastman Kodak Company Sensitizers for photoconductive compositions
US4419460A (en) * 1980-12-22 1983-12-06 Monsanto Company Phenolic foams
US4663260A (en) * 1985-09-05 1987-05-05 Fuji Photo Film Co., Ltd. Electrophotographic light-sensitive material comprising organic photoconductor and pyrylium sensitizer
US4774250A (en) * 1987-04-02 1988-09-27 Dana Farber Cancer Institute Composition and method for treating differentiated carcinoma or melanoma cells with thiapyrylium dyes
US5240802A (en) * 1991-12-31 1993-08-31 Eastman Kodak Company Aggregate photoconductive element and method of making same
US20100068640A1 (en) * 2006-08-23 2010-03-18 Noriyoshi Ogawa Binder resin for photosensitive layers and electrophotographic photoreceptor belts
EP2058704A4 (en) * 2006-08-23 2012-03-21 Mitsubishi Gas Chemical Co BINDER RESIN FOR LIGHT-SENSITIVE LAYERS AND ELECTRO-PHOTOGRAPHIC PHOTO-RECEPTOR BELTS
US8900781B2 (en) 2006-08-23 2014-12-02 Mitsubishi Gas Chemical Company, Inc. Binder resin for photosensitive layers and electrophotographic photoreceptor belts

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AU460903B2 (en) 1975-05-08
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AU3564571A (en) 1973-05-17
CA939983A (en) 1974-01-15

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