Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
  • G03G15/225—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 using contact-printing
• • 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
  • G03G5/043—Photoconductive layers characterised by having two or more layers or characterised by their composite structure
• • 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
  • G03G5/043—Photoconductive layers characterised by having two or more layers or characterised by their composite structure
  • G03G5/047—Photoconductive layers characterised by having two or more layers or characterised by their composite structure characterised by the charge-generation layers or charge transport layers
• • 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
• • 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
  • G03G5/0644—Heterocyclic compounds containing two or more hetero rings
  • G03G5/0646—Heterocyclic compounds containing two or more hetero rings in the same ring system
  • G03G5/065—Heterocyclic compounds containing two or more hetero rings in the same ring system containing three relevant rings
• • 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
  • G03G5/07—Polymeric photoconductive materials
  • G03G5/071—Polymeric photoconductive materials obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • G03G5/072—Polymeric photoconductive materials obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising pending monoamine groups
  • G03G5/073—Polymeric photoconductive materials obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising pending monoamine groups comprising pending carbazole groups
• • 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
  • G03G5/09—Sensitisors or activators, e.g. dyestuffs
• • 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

Definitions

• the light from the reflected areas, being depolarized, contains light with an electric vector which will be absorbed by the photoconductive element and the element is thus exposed to a pattern corresponding to the pattern of the document.
• This invention relates in general to contact reflex reproduction and in particular to electrophotography with a contact reflex exposure of a photoconductive element.
• graphic information has normally been transferred from original to photoconductive element by employing lenses or similar optical systems with the result that the photoconductive element is exposed to a pattern of ligh and dark, corresponding o the graphic information on the original.
• optical graphic information transfer a substantial part of the cost of the electrophotographic apparatus is attributable to the optical system.
• a relatively large and bulky housing must be provided to support not only the optical system but to provide, as well, predetermined distances between the optical system and the original depending on the focal length of the optical system.
• optical systems are very ineflicient in their utilization of available light and, therefore, some photoconductors would require too high an exposure time in an optical system employing a conventional relatively inexpensive light source so that more powerful and more expensive light sources must be employed.
• a non-electrophotographic contact reflex exposure process has been described in which this drawback is overcome because the photoprinting material contains an oriented dichroic light sensitive diazo compound.
• the original to be copied is brought into contact with the photoprinting material and the sandwich thus formed is uniformly exposed through the photoprinting material.
• the uniform incoming light is plane polarized with its electric vector normal to the principal transition moment of the dichroic light sensitive diazo compound. Decomposition of the diazo compound is produced only by absorbed light. Since the uniform incoming light is not absorbed due to the lack of parallelism between the electric vector of the plane polarized light and the absorption axis of the dichroic diazo compound, no photo decomposition occurs.
• the polarized light upon reflection by the surface of the original, the polarized light becomes substantially depolarized (e.g., no preferred electric vector direction exists) in being reflected from the white areas of the original back to the photoprinting material, and since a component of electric vector now exists in the direction of the transition moment of the dichroic diazo it is now substantially absorbed by the diazo compound thereby decomposing the diazo compound to form a developable image corresponding to the original image.
• Such substantial depolarization as described always results when plane polarized light is reflected from the diffusely reflecting surface, such as paper.
• Still another object of the invention is to provide a novel reusable photoconductive element which is capable of use in electrophotographic reproduction processes with contact reflex exposure using polarized light and which produces high quality copies in such reproduction processes.
• a further object of the present invention is to provide a novel photoconductive element which is well adapted to copying half tone images of extended area with high quality, even with differential voltage development methods such as the so-called cascade developing method.
• a novel reusable photoconductive element comprising an oriented dichroic material which is capable of transmitting essentially all of the polarized light having a direction of electric vibration such that the photoconductive element does not absorb the light and hence does not become conductive when exposed to such polarized light.
• the photoconductive element can be brought into contact with a document and uniformly exposed to such polarized light and the light is efficiently transmitted to the surface of the document without the photoconductive element becoming photoconductive as the light initially passes through the element.
• a substantial portion of the light reflected back from the light reflecting and depolarizing areas of the document is absorbed, thereby resulting in a high contrast latent image in the photoconductive element corresponding to the image of the document.
• This latent image is the basis for an electrostatic image which can be developed in any of the conventional ways to provide a copy of the document. Because the element is a photoconductor, it can be used repeatedly to provide copies of the same or different documents.
• the reflected light it is not necessary that the reflected light be completely depolarized, but only that, following reflection, it contains components of electric vibration which will be absorbed by the photoconductive element; for example, components of electric vibration normal to the polarized light transmitted through the element.
• Absorption or emission of light in a single molecule or a cooperating array of molecules is qualitatively ascribable to a motion of electric charge within the molecule or cooperating molecular array.
• Light generated by the motion of electric charge within a molecule is characterized by an electric field disturbance (the electric vector) whose direction coincides precisely with the direction of motion of the electric charge in the molecule giving rise to the light.
• the electric vector the electric field disturbance
• light absorption requires that the incident light possess a component of electric field disturbance in the direction of the electric moment of the molecule.
• the magnitude and direction of the electric charge motion within the molecule is measured by the socalled transition moment of the molecule and governs the intensity of the absorption and emission of light.
• a molecule is characterized by three mutually perpendicular transition moments which relate directly to the capability of the molecule to interact with light.
• the three transition moments may vary considerably in magnitude and, in particular, one moment may be very large relative to the remaining two. If a large number of such molecules are aligned (oriented) into an (uniaxially crystalline) structure so that the major transition moments are all parallel for all the molecules, the components of electric field of natural light incident on the array which are parallel to the aligned electric moments of the array are preferentially absorbed with the result that the remaining light is plan polarized, i.e.light is produced whose electric vector vibrates in a single well-defined direction.
• dichroic polarizer as exemplified by a Polaroid sheet. It will be understood that this explanation as to molecules is equally applicable to crystals.
• a material then is dichroic or exhibits dichroism if the absorption of linearly polarized light varies in accordance with the direction of the electric vector.
• a strongly dichroic material is one which will transmit essentially all of the linearly polarized light having an electric vector normal to its absorption axis while strongly absorbing the linearly polarized light whose electric vector is parallel to its absorption axis. It should be evident that, if linearly polarized light encounters an oriented dichroic array whose principal transition moment or absorption axis is normal to the direction of the electric vector of the light, no light can be absorbed by the oriented dichroic array, e.g.such light will be without substantial effect of any kind on the oriented dichroic array.
• the photoconductive element of this invention can be embodied in a number of ways, the preferred of which is by employing one of the novel photoconductors of US. Pats. 3,489,558 and 3,501,293, which exhibits dichroism when uniaxially oriented.
• Such photoconductors may be used either alone as the photoconductive material or in association with another material which is capable of transporting charge carriers and which is transparent to the wavelengths of polarized light employed.
• This material may be either insulating or semiconducting so long as its resistivity is sufiiciently high so that the composite photoconductive element will retain a charge on its surface in the dark.
• the resistivity of the material is 10 ohm-cm. or greater.
• this second material is inactive until light is absorbed by the dichroic photoconductor.
• Another embodiment for the photoconductive element of the invention is to use a photoconductor, again which is transparent to the wavelengths of polarized light, in conjunction with an oriented dichroic activator or sensitizer, which coacts with a photoconductor in some manner such as through the formation of a charge transfer complex.
• the photoconductor is photoconductively inactvie until the dichroic activator or sensitizer absorbs light and transfers the absorbed energy to the photoconductor.
• the dichroism of the element is either due to the crystalline form or the molecular form of the dichroic material.
• essentially all of the crystals or molecules must be aligned so that they act as a single dichroic unit, i.e., have essentially the same preferred absorption axis.
• this can be accomplished by dispersing the crystals in a stretchable sheet such as a sheet of polyvinyl alcohol, and stretching the sheet in an unidirection.
• the stretchable sheet must be essentially transparent to the Wave lengths of light which the dichroic material absorbs.
• the crystals should be microcrystalline in size to minimize light scattering.
• Dichroic molecules can be aligned in a number of ways, such as-(a) stretching as previously described, (b) attaching the molecules chemically within. a homogeneous material that already has a high degree of orientation in an unidirection, (c) coating the molecules onto the surface of a sheet which already has a preferred direction of orientation, (d) coating them on a surface by undirectional rubbing which may be followed by stretching, and extruding.
• d is the optical density obtained when the incident light is linearly polarized with the direction of the electric vector parallel to the transition moment axis for maximum absorption and wherein d is the optical density obtained when the incident light is linearly polarized with the direction of the electric vector perpendicular to the axis for minimum absorption.
• This optical dichroic ratio is an indication of the usefulness of a particular dichroic material in the photoconductive element of the present invention
• a dichroic photodecay ratio is more accurate and more important in determining the suitability of a particular material.
• This ratio, R is defined as 12 /11 wherein p is the decay rate of an electrostatic charge on the photoconductive element when the incident light is linearly polarized having the electric vector for maximum absorption and wherein p, is the decay rate obtained when the incident polarized light has the electric vector for a minimum absorption. These two rates may be based either on the initial decay rate or the decay at T (the exposure time required to reach one-half of the original electrostatic potential).
• This ratio is a measure of the usefulness of the oriented dichroic material of the present invention.
• the dichroic photodecay ratio should be at least greater than 2 and preferably should be greater than 5. It should be recognized that the dichroic photodecay ratio can be varied by changing the concentration of the dichroic material and will vary depending upon the method of fabrication of the element and its final configuration.
• the ratio, R can be increased by activating or sensitizing a dichroic photoconductive material so as to increase 1ts photoconductivity through the formation of a charge transfer complex or some other mechanism.
• the photoconductive element employing a charge transporting material insensitive to the wave lengths of polarized light it too can be activated or sensitized as long as it is not rendered sensitive to the wave lengths of polarized light.
• the photoconductive element of the present invention With the above general description of the photoconductive element of the present invention, the following describes the use of such an element in the electrophotographic process of the present invention.
• the photoconductive element is uniformly electrostatically charged, following which a document to be reproduced is brought into contact with the charged surface of the photoconductive element.
• the free surface of the photoconductive element is exposed to polarized light having its electric vector so oriented with respect to the absorption axis of the ele ment that there is maximum transmittance of the light through the dichroic photoconductive element.
• the polarized light Upon striking the original, the polarized light is essentially absorbed in the dark or black areas, usually the print areas, and depolarized in the light or white areas, normally background.
• the electrostatic charge pattern can be developed with toner in one of the known electrophotographic ways, such as cascade, magnetic brush or fur brush, and the developed pattern transferred to paper to provide 6 a high quality copy of the document.
• the electrostatic charge pattern can be transferred to a dielectric surface and developed thereon. After being cleaned, if the electrostatic charge pattern is developed on the photoconductive element, the photoconductive element is ready for additional cycles from which result additional high quality reproductions of the same or different documents.
• document includes not only those having areas which without further intervention depolarize and reflect the light back into the photoconductive element but also includes printed transparencies or translucencies which have been backed by a depolarizing and reflecting element.
• the preferred embodiment of the photoconductive element of the present invention comprises a transparent conductive substrate, such as a layer of cellulose triacetate having an aluminized surface, carrying an oriented dichroic photoconductor, such as 2,6-bis-[p-dimethylaminocinnamyldeneamino] benzo 1,2-d 4,5 -d' bisthiazole described in US. Pat. 3,501,293.
• the dichroic photoconductor is rubbed on in dry powder form in an unidirection which establishes a preferred axis for maximum absorption when the electric vector of the polarized light is parallel to the axis and a minimum absorption or maximum transmission of the light when its electric vector is perpendicular to the axis.
• the layer On top of the oriented dichroic photoconductor is a layer of a transparent normally insulating material which is essentially insensitive to the wave lengths of polarized light, but capable of transporting charges generated by the dichroic photoconductor.
• the layer comprises poly-N-vinylcarbazole which is essentially insensitive to the visible light to be used for the exposure of the photoconductive element.
• the photoconductive element With the surface of the tarnsparent poly-N-vinylcarbazole layer carrying a uniform electrostatic charge, the photoconductive element is exposed to visible polarized light from, for example, an unpolarized incandescent light source fitted with a light polarizing sheet, such as a H- sheet polarizer (manufactured by Polaroid Corporation).
• the photoconductor element is oriented relative to the "polarizer such that the electrical vector of the polarized light is prependicular to the absorption axis of the dichroic photoconductor.
• there is maximum transmittance of the polarized light through the oriented dichroic photoconductor and, hence, through the photoconductive ele ment as the light strikes the substrate side of the element.
• the polarized light With a document in contact with the charged surface of the photoconductive element during this exposure, the polarized light is essentially depolarized in the light colored or White areas of the document and is reflected back to the photoconductive element. This time, however, the electric vibrations of up to one-half of the depolarized light are parallel with the absorption axis of the dichroic photoconductor so that up to one-half of the reflected light may be absorbed.
• the areas of the dichroic photoconductor absorbing the light become conductive and, it is believed, generate charge carriers which are transported by the normally insulating layer. Regardless of the theory, the result is that the charge on the transparent photoconductor is dissipated so that an electrostatic charge pattern is formed corresponding to the pattern of the document.
• the polarized light striking the dark or black areas of the document is essentially absorbed and not reflected so that charge remains in such areas.
• the electrostatic charge pattern can be developed by one of the conventional techniques.
• Another embodiment of the photoconductive element of the present invention is one in which the positions of the transparent photoconductive layer and the dichroic photoconductive layer are reversed so that the transparent layer is adjacent the aluminized substrate. Because the dichroic photoconductive layer now forms the top layer, it is desirable in those cases in which this layer is easily abraded, to overcoat the dichroic layer with a protective layer, such as a transparent insulating material of, for example, cellulose acetate, or any other transparent material which will be sufliciently insulating to hold an electrostatic charge and will not be easily abraded.
• a protective layer such as a transparent insulating material of, for example, cellulose acetate, or any other transparent material which will be sufliciently insulating to hold an electrostatic charge and will not be easily abraded.
• a third embodiment employing a dichroic photoconductor comprises a single layer carried on a transparent conductive substrate.
• the dichroic photoconductor such as one of those described in US. Pat. 3,489,558, is dispersed in an insulating transparent matrix, such as polyvinyl formal.
• the matrix is stretched in a unidirection prior to applying it, for example, by lamination, to the conductive substrate, such as aluminized cellulose triacetate.
• the insulating film may also be photoconductive as long as the film is essentially insensitive to, or not rendered photoconductive by virtue of transmitting, the wave lengths of polarized light used for exposure.
• a dye sensitizer or an activator which is also known as an electron acceptor or, in some cases, when the photoconductor is an electron acceptor, an electron donor.
• dye sensitizers and activators are set forth in U.S. Pats. 3,037,861, 3,169,060 and 3,287,113.
• the dye sensitizer and activator combinations described in U.S. application Ser. No. 474,977, filed July 26, 1965 may be used in the preparation of such photoconductive elements.
• the embodiment of the photoconductive element is one in which a charge transfer complex is formed, either with a dichroic photoconductor and an activator, or a photoconductor and a dichroic activator, and the complex acts as a dichroic entity
• the absorption spectrum of the complex should be within or essentially match the wave lengths of polarized light employed.
• the non-dichroic activator or non-dichroic photoconductor must absorb essentially outside the wave lengths of the polarized light employed.
• a non-dichroic dye sensitizer When the photoconductive element comprises one of the embodiments which includes a charge transporting layer, the dye sensitizer or activator added to this layer must absorb essentially outside the wave lengths of polarized light being employed.
• the first of these embodiments comprises a transparent conductive substrate on which is applied a polymeric layer having a direction of orientation due to, for example, unidirectional stretching.
• This polymeric layer is stained with a material such as iodine which causes the polymer to exhibit dichroism and also serves as an activator for a photoconductive layer applied over the polymeric layer.
• This photoconductive layer is essentially transparent to the wave lengths of polarized light to be employed.
• the activator must be sufliciently abundant at the interface of the polymeric layer and the photoconductive layer to activate or render the latter layer conductive when light is absorbed by the polymeric layer.
• the two above-described layers may be reversed so that the polymeric layer is uppermost.
• the polymeric layer must be capable of holding an electrostatic charge in the dark on its surface, it must have a dark resistivity of at least 10 ohm-cm. and preferably should be in the range of 10 to 10 ohm-cm.
• some polymeric materials such as polyvinyl alcohol, may not be suited for this embodiment, or may have to be overcoated with an insulating material to achieve the proper resistivity.
• Another activator or sensitizer embodiment of the present invention comprises a single layer of an oriented polymeric photoconductor, such as a terpolymer of N- pentenylcarbazole, N-hexenylcarbazole, and pentene-l (mole ratio of 40:40:20, respectively) which has been stained by, for example, 2,4,7-trinitro-9-fluorenone which activates the polymeric photoconductor as well as serves to render it dichroic.
• an oriented polymeric photoconductor such as a terpolymer of N- pentenylcarbazole, N-hexenylcarbazole, and pentene-l (mole ratio of 40:40:20, respectively) which has been stained by, for example, 2,4,7-trinitro-9-fluorenone which activates the polymeric photoconductor as well as serves to render it dichroic.
• metallized (i.e.aluminum, and copper) polycarbonate and glass are metallized (i.e.aluminum, and copper) polycarbonate and glass.
• NESA glass may be used.
• the substrate may serve to polarize incoming unpolarized light or change incoming polarized light so that its electric vector is the proper direction for transmission through the photoconductor.
• a further modification of the present invention concerns a process in which a semi-transparent mirror is inserted in back of the photoconductive element. That is, the exposure step now comprises what can be termed mirror dichroic reflex.
• the exposure step now comprises what can be termed mirror dichroic reflex.
• the incoming polarized light passes through the semi-transparent mirror and the photoconductive element, but the depolarized light reflected from the document which is not absorbed by the photoconductive element is reflected back into the photoconductor by the highly reflective surface of the mirror.
• the reflected depolarized light not initially absorbed by the photoconductive element will be reflected between the mirror and the document, with additional light being absorbed by the photoconductive element during each such reflection.
• Filters may be used with the exposing light source if it is necessary to eliminate wavelengths of light which would be absorbed by other than the dichroic entity or to confine the exposure light to those spectral regions which the element exhibits adequate dichroism.
• a glass substrate was metallized with aluminum to a thickness such that the optical transmission density was 1.0 (i.e.10% transmitting, the aluminum serving as a conductive electrode as well as a highly reflective mirror.
• a 10% by weight poly-N- vinyl carbazole in tetrahydrofuran was coated over the dichroic photoconductive coating with a doctor blade set at a 5 mil wet gap, the resulting dry thickness being about 8-l0 microns.
• the thus prepared photoconductive element was electrostatically charged with a Xerox Model D processor set at a negative --7000 volts to form a uniform negative electrostatic charge.
• the charged element was brought into face-to-face contact with a document (black print on a white background).
• the document and charged photoconductive element was exposed to polarized light from a 375 watt photo EBR flood lamp passing through a light polarizing film (supplied by Bausch and Lomb, Catalog No. 31-52-62-26) through the back of the eleconductor (see table below) was rubbed in a unidirection on the coating.
• i /2% solution of poly-n-vinylcarbazole in benzene was coated on the meniscus coater with a sufiicient number of passes to form an approximately micron layer.
• the dichroic photoconductor aligned for low absorption relative to the electric vector of the polarized light so that the light was essentially transmitted through the element.
• the white background of the document it was depolarized, reflected back, and absorbed.
• the exposure was for 0.4 seconds at a distance of 12 inches.
• the document was separated from the photoconductive element and the remaining electrostatic charges in the unexposed (print) areas was de- 'veloped by cascading positively charged toner particles which were attracted to the negative electrostatic charge pattern.
• the developed pattern was transferred to a copy sheet to yield a copy of the document which had high print density, excellent contrast and only a faint background.
• EXAMPLE II A glass substrate was coated with polyvinylidene chloride to form a thermoplastic coating. Next, a dichroic photoconductor of 2,4 bis(p-N,N dimethylaminobenzyhdeneamino)-benzo[1,2-d:4,5-d]-bisthiazole was rubbed in an unidirection on a film of poly-N-vinylcarbazole activated with 2% by weight of tetrachlorophthalic anhydride and carried on a temporary polyethylene terephthalate substrate.
• the poly-N-vinyl carbazole film On the poly-N-vinyl carbazole film was an aqueous solution of a methylvinylether-maleic anhydride copolymer and quaternary ammonium salt in equal parts by weight using a doctor blade set at a 1 /2 mil wet gap. Upon drying, the thickness of this conductive coating was about 2-3 microns.
• the polyvinylidene chloride coating on the glass substrate was brought into contrast with the conductive coating on the poly-N-vinylcarbazole and laminated thereto by heating to about 100 C. After cooling, the polyethylene terephthalate temporary substrate was separated to leave the finished photoconductive element.
• This photoconductive element was used for reproducing a copy of a document in the same manner as Example 1 except that the light source was a 40 watt incandescent lamp and the element was 12 inches from the lamp when exposed for 1 second.
• the copy had high print density and good contrast with fair background.
• EXAMPLE VII A glass substrate was metallized with aluminum to a thickness such that the optical density was 1.0 10% transmitting). A solution of 10% by weight of poly-N- vinyl-carbazole in tetrahydrofuran was coated with a doctor blade set at a 5 mil wet gap, the resulting dry thickness being about 810 microns. Next, a dichroic photoconductor of 2,6-bis-[p-dimethylaminobenzylideneamino]- benzo[l,2-d,5,4-d]bisthiazole in dry powder form was lightly rubbed with an unidirectional motion or in the long direction of the substrate to form a thin coating having an optical density in the region of 0.2-0.6 with polarized light oriented for absorption.
• Example I Following the reproduction procedure of Example I, except that the Xerox Model D processor was set at a positive +7000 volts and that the light source was a 40 watt incandescent lamp spaced at a distance of 12 inches from the above prepared photoconductive element, and the exposure was 1 second, a copy of a document was reproduced and it had high print density, good contrast, and only a faint background.
• EXAMPLE VIII For determining the dichroic photodecay ratio of photoconductive elements and, in addition, the measuring difference in surface potential of the photoconductive elements is exposed to strongly absonbed polarized light and weakly absorbed polarized light, the following described electrometer was used and serves as a simulated reproduction process. The exposures are over a period of time and this gives a measure of the latitude of the photoconductive elements.
• the electrometer comprises an electrostatic corona discharge charging unit set at a potential of 6000 volts and a Model 566 Charge Amplifier (manufactured by Kistler) having a transparent NESA glass probe.
• a rotatable photoconductive element holder on a pivoted arm capable of moving the photoconductive element holder from the charging unit to in front of the transparent glass probe.
• the electrometer has a watt tungsten lamp with a filter holder disposed adjacent the lamp.
• a light tube In optical contact with the 1 1 holder is a light tube which, in turn, is attached to the transparent glass probe.
• On the back side of the glass probe is an H-sheet polarizer (manufactured by Polaroid).
• the charge amplifier is connected to a Type 535 Oscilloscope with a 53/ 54C Plug-In unit.
• a photoconductive element sample is placed in the holder with the photoconductive surface facing out of the holder and aligned, relative to the electric vector of the polarized light, to only weakly absorb the light.
• the arm is moved to place the sample in front of the charging unit and is given an uniform electrostatic charge.
• the charged sample is moved in front of the transparent probe and exposed to polarized light from the lamp passing through the polarized light.
• the exposure is observed on the oscilloscope as a trace moving from left to right. Depending on the dissipation of the electrostatic charge on the photoconductive element, the trace also curves downwardly. The exposure is retained until the trace reaches the right side of the oscilloscope.
• the following table lists the properties of seven photoconductive elements which were prepared by coating a poly-N-vinyl carbazole in tetrahydrofuran solution on polyethylene tcrephthalate substrate carrying a conductive layer of a quaternary ammonium salt in polyvinyl alcohol.
• the respectiwe dichroic photoconductor was applied in powder form with an unidirectional wiping motion.
• the thus prepared elements were tested on the above-described electrometer with the traces on the oscilloscope being photographed.
• the dichroic ratio is also given and was measured on a Cary Model 14 spectrophotometer.
• the filters are Balzers #2 and #3 filters, having x max, respectively, of 4500 A and 4800 A.
• EXAMPLE XV An aqueous solution of polyvinyl alcohol was coated on an aluminum by an unidirectional wiping to form a thin oriented coating. This coating was then stained with a 1% iodine solution in acetone again wiping in the same unidirection. Next, a 10% polyvinylcarbazole solution in tetrahydrofuran was coated on the stained polyvinylalcohol with a doctor blade set at a 5 mil wet gap. When evaluated with the above-described electrometer, it had a dichroic photodecay ratio of 3.0. Accordingly, iodine in an oriented configuration is useful as a dichroic sensitizer in the dichroic reflex process of the present invention.
• EXAMPLE XVI Light source watt incandescent Distance from source: 12 inches Time: 1.0 sec.
• the above-described document was then copied on a Xerox 720 and a visual comparison made.
• the Xerox 720 had good contrast between the black and white areas but there was essentially no grades of half tone reproduction. Instead, the half tone areas reproduced as continuous light black areas.
• the copy reproduced by the dichroic reflex process of the present invention had excellent contrast between the black and white areas and good reproduction of the half tone areas.
• dichroic reflex process and photoconductive element of the present invention may be employed in persistent Diehroic photodecay ratio Optical Full Per- #2 Ier- #3 Perdiehroic tungcent filcent filcent Dichrole photoconductor ratio sten eff. ter etf. ter e11.
• the dichroic photoconductor of Example XIII was prepared according to the procedure of Examples III-VI.
• the element thus electrophotographic methods, such as that disclosed in US. Pat. 2,845,348 or any other method where the photoconductor is exposed before charging.
• the dichroic reflex process and photoconductive element of the present invention can be used in conjunction with charge transfer techniques, such as disclosed in US. Pat. 2,825,814.
• the photoconductive element can be prepared had a dichroic photodecay ratio of 19 with full fabricated with a non-conductive substrate and the charging of the element can be accomplished by dual corona, such as described in U.S. Pat. 2,922,883.
• a photoconductive element suitable for use in electrophotographic reflex copying, comprising a dichroic material oriented in an unidirection to have preferred maximum absorption and transmission axes, and exhibiting photoconductive dichroism, said dichroic material being capable of causing conductivity in those areas of the photoconductive element which are exposed to light having an electric vector of suflicient magnitude and in a direction parallel to said absorption axis.
• the photoconductive element of claim 1 wherein said element comprises a transparent substrate having disposed thereon a thin layer of a dichroic photoconductor and a thicker essentially transparent charge transport layer, said photoconductive layer and said charge transport layer being in contact with each other, the composite of said layers being of suflicient resistivity to support an electrostatic charge in the dark, said dichroic photoconductive layer being oriented in an unidirection to provide said preferred absorption axis, the light absorption spectra of said charge transport layer being essentially outside the light absorption spectra of said dichroic photoconductive layer.
• a photoconductive element of claim 1 wherein said element comprises a transparent substrate having disposed thereon a layer of a polymeric material oriented in an unidirection, a layer of an essentially transparent photoconductor, and a material at the interface of said oriented polymeric layer and said photoconductive layer capable of rendering the oriented layer dichroic to provide said preferred absorption axis and of serving as an activator for the photoconductor.
• An electrophotographic process for the production of reflex copies comprising:
• step comprising:
• exposing a photoconductive element exhibiting photoconductive dichroism and having a preferred absorption axis, to a light pattern resulting from reflection of light from a document in contact with the photoconductive element and in accordance with the pattern of the document, said light pattern containing light with an electric vector parallel to the absorption axis of said element so as to render conductive those areas of the element corresponding the light pattern, said light prior to reflection from the document having a transmission direction opposite to the reflected light pattern and being polarized light with an electric vector essentially normal to the absorption axis of said photoconductive element as it passes the axis so that said polarized light is essentially transmitted by the photoconductive element.
• the photoconductive element contains a semitransparent mirror on the side of the absorption axis opposite to the side of the element in contact with the document whereby said polarized light is transmitted through the mirror but each portion of the reflected light pattern not absorbed at the absorption axis is reflected back and forth between the mirror and the document thereby increasing the total light absorbed by the photoconductive element.
• said photoconductor comprises a transparent substrate having disposed thereon a thin layer of a dichroic photoconductor and a thicker charge transport layer, said photoconductive layer and said charge transport layer being in contact with each other, the composite of said layers being of sutficient resistivity to support an electrostatic charge in the dark, said dichroic photoconductive layer being oriented in an unidirection to provide said preferred absorption axis, and wherein the wavelengths of said polarized light are essentially outside the wavelengths of absorption by said charge transport layer.
• said photoconduc tive element comprises a transparent substrate having dis posed thereon a layer of a polymeric material oriented in an unidirection, a layer of a photoconductor absorbing essentially outside the wavelengths of the polarized light,

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Photoreceptors In Electrophotography (AREA)
• Laminated Bodies (AREA)
• Light Receiving Elements (AREA)

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Cited By (29)

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• 1967
  • 1967-09-18 US US668697A patent/US3598582A/en not_active Expired - Lifetime
• 1968
  • 1968-08-28 FR FR1577855D patent/FR1577855A/fr not_active Expired
  • 1968-08-30 GB GB41417/68A patent/GB1244765A/en not_active Expired
  • 1968-09-03 BE BE720358D patent/BE720358A/xx unknown
  • 1968-09-05 CH CH1335668A patent/CH496264A/de not_active IP Right Cessation
  • 1968-09-10 ES ES357985A patent/ES357985A1/es not_active Expired
  • 1968-09-11 NL NL6812934.A patent/NL158624B/xx unknown
  • 1968-09-17 SE SE12539/68A patent/SE339911B/xx unknown
• 1971
  • 1971-07-05 JP JP46048897A patent/JPS4926907B1/ja active Pending

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