Abstract: A method for applying instant self-fixing adherent printing images from a recording member to a substrate includes applying a liquid toner including toner material and a liquid carrier to a latent image on a ferro-electric recording member, removing an excess amount of the liquid carrier from the adherent image using an extraction mechanism, and transferring the adherent image without the excess liquid carrier to a substrate. The present invention also includes a apparatus for performing the inventive method.

Abstract: In an air circulation system of a liquid electrophotographic printer, an engine shell includes a developing unit for developing an electrostatic latent image which is formed on a photoreceptor belt and having an air injector, a drying unit for drying the developed image, and a transferring unit for transferring the developed image to print paper. Air in the engine shell is taken in and exhausted to the outside though a main path. A filter is installed on the main path for filtering air. A return path is branched from the main path and through which the air taken in from the engine shell is supplied to the air injector. An air pump provides a driving force such that air can flow along the main path and the return path. Thus, as air can be exhausted from the engine shell and the exhausted air can be re-supplied to the air injector using a single pump, the structure of the system is simplified.

Abstract: The invention relates to a digital electrostatic printing machine, comprising a cylinder with an electrostatically chargeable surface (PIP cylinder), to which charging electrodes, a laser write head and a quench electrode are assigned, and comprising an ink applicator, a transfer cylinder and a central cylinder. According to the invention, the ink applicator comprises an engraved roller.

Abstract: In an apparatus for elevating a squeeze roller of a liquid developing apparatus, a sub-block having the squeeze roller selectively pressing a photoreceptor web installed thereon, is installed at a main block of the liquid developing apparatus to be capable of moving up and down. A mobile block is installed at the main block to be capable of moving up and down to support the sub-block. The mobile block is moved up and down by an elevating unit to allow the squeeze roller to contact or be separated from the photoreceptor web. A piezoelectric element is installed at the mobile block to support the sub-block and to move the sub-block up and down in a predetermined range by being reversibly transformed by electric current. A power supply selectively provides electric current to the piezoelectric element. Thus, the decline over time of the elastic force of the spring employed in the conventional elevating apparatus can be fundamentally solved.

Abstract: An image forming apparatus is provided with developing units of different colors. Each developing unit is made up of a developing roller and a squeeze roller located downstream of the developing roller with respect to the rotating direction of a photosensitive drum. The outer circumference of the squeeze roller is a resin layer whose surface roughness Rz is less than 3 .mu.m. The squeeze roller is formed of a conductive material, and serves to remove a residual carrier solution from the photosensitive drum. The squeeze roller can be applied with a predetermined bias voltage. Due to the application of the bias voltage, a transfer medium is prevented from becoming dark in the background portion thereof, despite the use of small-diameter toner particles.

Abstract: A developer removing apparatus is provided of a liquid printer for removing a developer remaining between a photoreceptor belt and a squeeze roller. The apparatus includes a suction nozzle having a suction portion formed in an axial direction of the squeeze roller to suck the developer and an exhaust portion for exhausting the developer sucked by the suction portion. The apparatus further includes a suction pump providing a suction force to the suction nozzle so that the suction portion can suck the developer and exhaust the developer from the exhaust portion.

Abstract: A cleaning member on a surface of a developer roller can effectively remove toner particles on the developer roller. The cleaning member has a plurality of flexible blades slidingly contacting with the surface of the developer roller on a peripheral surface of a rotary roller arranged in parallel to the developer roller and brushes provided on the surface of the roller at a position between the blades and slidingly contacting with the surface of the developer roller. The cleaning roller is housed within a cleaning chamber and driven to rotate at a higher speed than the developer roller.

Abstract: A squeegee apparatus and method for removing excess developer liquid from an imaging substrate in a liquid electrographic imaging system make use of a squeegee roller having a core with a crowned profile. With determination of a proper loading force, the squeegee apparatus and method achieve substantially uniform loading force along the length of the squeegee roller, and thus along the width of a nip formed along an the imaging region of the imaging substrate. As a result, the squeegee apparatus and method provide substantially uniform removal of developer liquid from the imaging substrate, enhancing quality of an ultimate printed image.

Abstract: A wet image forming unit for developing an electrostatic latent image formed onto a surface of a photosensitive body by a liquid developing solution containing toner particles is characterized in that a squeeze roller for squeezing of a surplus developing solution on the photosensitive body and cleaning the photosensitive body is provided and, just before stop of an image forming operation, a voltage whose polarity is opposite to a charging polarity of the toner particles is applied to the squeeze roller. The squeeze roller rotates in the direction similar to the photosensitive body upon the image forming operation. However, just before the stop of the image forming operation, the squeeze roller rotates in the direction opposite to the photosensitive body. During printing, the liquid developing solution which remains and gathers at the interval between the photosensitive belt and squeeze roller is removed by the reverse rotation of the squeeze roller not only mechanically, but also electrically.

Abstract: A squeezing apparatus of a liquid developing apparatus including a mobile block installed under a photoreceptor web, the mobile block being capable of moving up and down, a squeeze roller supported by the mobile block and moving up and down with the mobile block, the squeeze roller contacts a transfer surface of the photoreceptor web when moving up and removes excess developer therefrom, an air injection nozzle, installed at the mobile block, for injecting air to a portion of the photoreceptor web where the squeeze roller contacts the photoreceptor web to separate and drip the excess developer downward, an air supply pump for supplying air to the air injection nozzle, and a bellows pipe connecting the air injection nozzle and the air supply pump and to be capable of expanding or being compressed as the mobile block moves up and down.

Abstract: In an image forming apparatus having a liquid developing device, a thin layer of dense and viscous developing liquid is formed on a developer carrier and brought into contact with a latent image electrostatically formed on the surface of an image carrier in order to develop it. A preselected electric field is formed between the developer carrier and a device for regulating the thickness of the above layer, providing a dense layer with a uniform high toner content and an excess liquid surface layer. The excess liquid surface layer, formed with the developing liquid layer, is removed by a developing layer removing device. With this configuration, the apparatus ensures images free from irregularity.

Abstract: A squeeze roller elevating apparatus for a liquid electrophotographic printer in which a squeeze roller selectively presses a photoreceptor belt, the photoreceptor belt being supported by a belt, the apparatus including a squeeze frame fixed to the belt frame to support the squeeze roller, the squeeze roller being capable of elevating, and an elevating mechanism for elevating the squeeze roller. The elevating mechanism includes a driving motor, a winch drum being rotated by the driving motor, a mobile pulley rotatably installed at one end portion of a rotation shaft of the squeeze roller, and a wire having one end thereof fixed to the squeeze frame and the other end thereof wound about the winch drum, to support the mobile pulley, wherein, when the winch drum is rotated by the driving motor, the wire is wound or released so that the mobile pulley and the squeeze roller ascend or descend, respectively.

Abstract: An electrophotographic system includes a photoreceptor belt for carrying a toner image including solvent, a solvent absorbing roller for absorbing the solvent from the toner image, a solvent evaporation roller for receiving the solvent from the solvent absorbing roller and evaporating the solvent therefrom, a cleaning roller for cleaning the solvent absorbing roller, and a cleaning roller for removing the toner on the cleaning roller. The electrophotographic system effectively removes the toner from the solvent evaporation roller without damage of thereof.

Abstract: An apparatus and method provide improved custom color capabilities. A pre-mixed custom color toner having a high solids content of approximately 10-50% is used to generate a custom color toner layer to develop an electrostatic latent image. In contrast to conventional liquid developing systems, a complex control system is not needed to achieve consistent and stable color toner images using the invention. A custom color toner layer assembly can also be formed and used to develop an electrostatic latent image. Because the color and density of the toner layer assembly is formed before image development, color correction steps can be avoided.

Abstract: An image formation apparatus for performing development by supplying to a photosensitive body a developing solution containing toner includes a developing roller; a developing solution supply port; a squeeze roller for wiping off an unnecessary portion of the developing solution from the photosensitive body; a moving frame reciprocally moving toward/from the photosensitive body; a squeeze support body for holding the squeeze roller; and two elastic bodies having different natural lengths that are provided between the moving frame and the squeeze support body and can be expanded and contracted for urging depression of the squeeze roller toward the photosensitive body.

Abstract: A squeeze roller elevating apparatus of a liquid electrophotographic printer for selectively pressing a photoreceptor belt, which is installed at a belt frame for circulation, by elevating a squeeze roller. The apparatus includes a housing fixed at the belt frame, a squeeze frame installed in the housing and operative to elevatingly support the squeeze roller, a first elevating member installed at the squeeze frame for elevating movement, a second elevating member installed at the squeeze frame for elevating movement by being interlocked with the elevating movement of the first elevating member and moving the squeeze frame upward so that the squeeze roller presses the photoreceptor belt while ascending, a first spring coupling the first elevating member and the second elevating member to be interlocked with one another, a second spring coupling the second elevating member and the squeeze frame to be interlocked with one another, and an elevator which elevates the first elevating member.

Abstract: A wet-type image forming apparatus providing a uniform pressure applied to a photoconductor belt is disclosed. A squeezing roller is provided in the development side of the photoconductor belt and a backup roller in provided in the non-development side of the photoconductor belt. The photoconductor belt is held by the squeezing and backup rollers under a predetermined pressure during development. The squeezing roller is moved toward or away from the photoconductor belt and the longitudinal axis of the backup roller is titled to a predetermined angel with respect to that of the squeezing roller about an longitudinal middle point thereof during the development.

Abstract: An electrostatic recorder includes electrostatic latent image recorder elements for forming an electrostatic latent image on a recording medium conveyed at a predetermined speed, a liquid toner feed for feeding a toner to a surface of the recording medium on which an electrostatic image is formed, and a toner recoverer for recovering an excess of toner stuck to the recording medium. The toner recoverer can execute the recovery of an excess of toner not only by suction but also by scraping from the recording medium prior to this suction. Members for eliminating the mixing of foreign matters into the feed side in conjunction with the recovered toner are also provided.

Abstract: A method and apparatus for improving the quality of an image that has been developed by a liquid carrier is disclosed. Generally speaking, the invention is a blotter roll which includes an absorbing layer wrapped around a non-permeable rigid core. A vacuum system communicates with the exterior surface of the blotter roll to remove the excess fluid from the blotter roll and transport it out of the printing system.

Abstract: A blotter/charging device is provided for simultaneously removing excess liquid carrier from a developed toner image and recharging a photoreceptor in preparation for generating and developing another electrostatic latent image on the photoreceptor. The blotter/charging device is useful for all types of liquid developing systems that generate two or more toner images on a photoreceptor, including image-next-to-image, image-on-image, highlight and other types of systems. A method is also provided for generating a plurality of toner images on a support wherein excess liquid carrier is removed from a developed toner image simultaneous with recharging of the support in preparation for generating and developing a second electrostatic image on the support.

Abstract: A development roller cleaning apparatus includes a cleaning blade installed with an end contacting an outer surface of a development roller for removing an excess developer liquid therefrom, and a guide for guiding an excess developer liquid removed by a squeegee roller installed downstream from the development roller to the end of the cleaning blade.

Abstract: The invention provides a belt type photosensitive member cleaning apparatus for a wet type image forming apparatus which can effectively remove liquid developer pressed out by a pair of pressing out rollers for removing remaining liquid developer from a belt like photosensitive member after developed to prevent such liquid developer from flowing out and soiling to a window for a sensor or the photosensitive member. Each of the pressing out rollers provided in a stage next to a first pressing out roller has grooves formed at the opposite end portions thereof such that liquid developer which tends to be pressed out from the opposite ends of each of the second pressing out rollers is collected in the grooves.

Abstract: A method and apparatus for improving the quality of an image that is developed by a liquid carrier is disclosed. The invention relates to image blotting and is directed to reducing disruptive forces on the wet image during blotting. The invention relates to the conditions under which liquid carrier is removed from the surface of an image supportable member.

Abstract: A developing device develops a latent image formed on a latent image carrier by supplying a developer to the latent image carrier. The developer comprises a carrier liquid and a toner dispersed in the carrier liquid. A gelling agent adding device adds a gelling agent to the developer remaining in the developing device so as to gel the developer.

Abstract: A system for removing residual contaminants from an image conditioning apparatus that removes excess liquid from a developed image made up of toner particles immersed in a liquid carrier medium on an image bearing member. The system includes a vacuum blotting device that contacts the liquid developed image and absorbs a portion of the liquid carrier and residual contaminants remain thereon. A contact member adapted to be shifted from a non-operative position spaced from the vacuum blotting device, to an operative position in contact with the vacuum blotting device operates to transfer the contaminants therefrom. A scraper removes the transferred contaminants from the contact member. The contact member is pivotally mounted about the pivot point to effect shifting of the contact member between the non-operative and the operative position.

Abstract: A liquid electrophotographic printer having an improved drying unit is provided. The liquid electrophotographic printer includes a photoreceptor belt circulating and supported by a plurality of rollers on an endless track, for forming a latent electrostatic image on the photoreceptor belt, a development unit for supplying a developer liquid to the photoreceptor belt and developing the latent electrostatic image into a toner image, a drying unit for drying the photoreceptor belt on which the toner image is formed, and a transfer unit for transferring the toner image to a sheet of paper, wherein the drying unit includes a heating device installed in the vicinity of one surface of the photoreceptor belt for heating the photoreceptor belt on which the toner image is formed to evaporate a carrier sticking to the photoreceptor belt, and a collector installed in the vicinity of another surface of the photoreceptor belt for collecting the carrier evaporated by the heating device.

Abstract: The undesirable image defect of dragout of liquid ink development (LID) toned images generated from the development zone, formed by an imaging member and a metering/development member, can be prevented. Background development of the toned images is suppressed in an image enhancement zone. With the aid of an enhanced electrostatic field, created by an electrode biased at a voltage other than normal development bias in the metering zone, the toned layer can resist higher viscous forces. Image dragout, due to the viscous shear from liquid ink, can therefore be eliminated.

Abstract: An ink delivery system for a liquid electrophotographic color printer delivers a developer liquid to a plurality of development units, and includes a plurality of circulation tanks containing developer liquid, connected to the respective development units; a plurality of jet portions for jetting the developer liquid in the circulation tanks to development gaps in the respective development units; a plurality of ink tanks having concentrated inks incorporated in a printer body; a plurality of agitators installed in the respective ink tanks for agitating the concentrated ink; a refill ink cartridge detachably installed in the printer body, for refilling the concentrated ink consumed in the ink tanks through a concentrated ink refill path; a plurality of concentrated ink supply paths to supply concentrated ink to the corresponding circulation tanks; a carrier tank containing carrier, which is fixed in the printer body; a carrier supply path through which the carrier is supplied to the respective circulation tank

Abstract: An electric field applying device is disposed in a position opposite to a surface of rotary developing device within an area defined between the surface of the developing means and a position of scratching device after the surface of the developing device passes through a developing area so as to apply an electric field in a direction in which ions having the polarity opposite to that of toner particles are separated from the surface of the developing device.

Abstract: A single image development and conditioning apparatus is disclosed for removing excess liquid carrier from a developed image developed in a liquid immersion development machine using liquid developer material having a first toner concentration. The single image development and conditioning apparatus includes a first zone located downstream of a coating device relative to a direction of movement of a surface bearing the developed image, a second zone located downstream of the first zone, and a third zone located downstream of the second zone. The first zone includes a first biased electrode for partially removing charged solid toner particles from background areas of the developed image. The second zone includes a second biased electrode for completing removal of charged solid toner particles from the background areas, and the third zone includes a third biased electrode.

Abstract: A liquid electrophotographic printer includes a photoreceptor belt supported by and traveling around a plurality of rollers, a development device for supplying a developer liquid to the photoreceptor belt, and a drying roller having a cylindrical roller body having a hollow and through holes leading to the hollow, a rotation member rotatably installed on the outer surface of the roller body and having a plurality of mesh-like inlet holes, and an absorbing member coupled to the outer surface of the rotation member, for absorbing the liquid carrier in contact with the photoreceptor belt.

Abstract: A development apparatus for a liquid electrophotographic printer includes a development roller for supplying a developer liquid to a photoreceptor belt on which a latent electrostatic image is formed, a plurality of squeegee rollers for removing excess developer liquid sticking to the photoreceptor belt, at least one cleaning device having a rotary body rotatably installed in proximity with at least one of the plurality of squeegee rollers, and a plurality of blades installed on the perimeter of the rotary body at a predetermined spacing, in contact with the surfaces of the respective squeegee rollers, and a rotation mechanism for selectively bringing one of the plurality of blades into contact with the surface of each squeegee roller. Therefore, when one blade is worn, the worn blade can be replaced with a new one without dismantling the development apparatus, and thus the life of the development apparatus is prolonged.

Abstract: A developing apparatus develops a latent image with a liquid developer includes a developer container capable of containing the liquid developer therein, a developer carrying device that carries the developer thereon and develops a latent image thereon, a developer applying device that applies the developer to the developer carrying device and forms a thin developer layer thereon, and a developer supplying device positioned in contact with the developer applying device and supplies the developer from the developer container to the developer applying device. The developer-supplying device is separated after the developer carrying device develops a latent image, while the developer applying device removes the developer remaining on the developer carrying device.

Abstract: A liquid carrier withdrawal apparatus for a liquid electrophotographic imaging system for withdrawing a liquid carrier by separating the liquid carrier from a developer liquid embedded on a photoreceptor for a liquid electrophotographic imaging system.

Abstract: An image printing apparatus includes a photoreceptor belt on which a latent electrostatic image is formed, and a plurality of development devices for developing the latent electrostatic image formed on the photoreceptor belt. Each of the development devices has a development roller for coating a developer liquid on the photoreceptor belt, and a squeegee roller for removing excess developer liquid from the photoreceptor belt. A roller driving means drives the squeegee rollers, and an elevating means elevates the development devices. The plurality of development devices are supported by a pair of frames that are spaced apart a predetermined distance from each other. The roller driving means commonly drives the squeegee rollers of the development devices. The frame elevating means displaces the pair of frames, such that the squeegee rollers are simultaneously in contact with or out of contact with the photoreceptor belt.

Abstract: An alignment device for a developing roller and a squeegee roller of an image forming apparatus. The alignment device includes a first supporting block for supporting the shaft of a first backup roller which in turn is disposed opposite to the squeegee roller with a photosensitive belt therebetween; and a second supporting block for fixing the shaft of a developing roller and enabling development by the developing roller, and for supporting the shaft of a second backup roller which in turn is disposed opposite to the developing roller with the photosensitive belt therebetween. A roller frame is provided for fixing the shaft of the squeegee roller, and for supporting the first supporting block and the second supporting block while surrounding a portion of the second supporting block. An elastic member is installed between the first and second supporting blocks for adjusting the centers of the supporting blocks.

Abstract: A method for driving development devices of an image forming apparatus including the steps of: (a) simultaneously rotating gear cams of the respective development devices for colors Y (yellow), M (magenta), C (cyan) and K (black); (b) determining whether the frame of the development devices is lifted to a preset position; (c) rotating a developing roller; (d) coating a developer liquid on an image portion of a photoreceptor belt; (e) determining whether the image portion has passed through a transfer roller or not; (f) simultaneously rotating the gear cams of the respective development devices for colors Y, M, C and K if the image portion has passed through the transfer roller; (g) determining whether the distance between the frame and the photoreceptor belt is a preset value; (h) simultaneously stopping the gear cams of the respective development devices for colors Y, M, C and K if the distance between the frame and the photoreceptor belt is the preset value; and (i) simultaneously removing drip lines by sim

Abstract: A liquid developing head is arranged to confront a surface of an image bearing member via a developing gap and a squeeze gap and carries out a developing by use of a developing liquid.

Abstract: An apparatus and method for removing back-plated developer from a development device in a liquid electrographic imaging system make use of a blade disposed to remove back-plated developer from the development device, and a brush disposed to remove the back-plated developer from the blade and redisperse the back-plated developer into a developer liquid supply. The brush includes a shaft and bristles disposed about the shaft. The shaft preferably is rotated to drive the bristles against the blade. In this manner, the bristles remove the back-plated developer from the blade and redisperse the back-plated developer within the developer liquid supply. The bristles can be formed from a substantially resilient material to generate a flicking action upon deflection and recovery. This flicking action facilitates redispersion of the back-plated developer into the developer liquid supply.

Abstract: In a squeeze roller assembly of a wet type developer of an electrophotographic printer, a shaft is rotatably installed in a frame. A first roller is fixed on the shaft for filming solid toner from a developing liquid onto a photosensitive belt. Second rollers are rotatably installed on the same shaft at both sides of the first roller. The first roller, attached to the central portion of the imaging surface of a photosensitive belt, rotates in the same direction as that of the conveying direction of the photosensitive belt. The second roller rotates in a direction opposite to the direction of the photosensitive belt by an inverse rotator. Therefore, it is possible to reduce the required installation space by having the first and second rollers share a common shaft as a rotating axis.

Abstract: A system for removing excess carrier liquid from an electrostatic image developed with liquid developing material made up of toner particles immersed in a liquid carrier medium on an image bearing member. The system includes an absorbent contact roller for absorbing at least a portion of the liquid carrier off of the liquid image, and vacuum source coupled to the contact roller for generating both negative pressure at the surface of the roller to draw the absorbed liquid through the contact roller, and positive air pressure for pushing contaminated liquid out of the roller.

Abstract: Imaging apparatus including squeegee apparatus for squeegeeing excess material from a surface, from which surface at least a portion of the material remaining after squeegeeing is to be transferred to another surface, comprising: a first surface, having a central portion and two end portions having recessed surfaces and having a liquid material thereon at least in said central portion, said surface moving in a given direction at a squeegee region; and a second, squeegee, surface, urged against at least the central portion of the first surface at the squeegee region and formed with contiguous end portions which mate with the recessed end surfaces of the first surface.

Abstract: A transfer printing apparatus in which a recording image is written by ink drops ejected from an ink jet recording head onto a transfer drum. The ejected ink includes a dispersion medium and coloring material. The apparatus includes a dispersion absorbing member which absorbs the dispersion medium of the ink from the drum without removing the coloring material and which does not contact the transfer medium. The absorption is provided by an absorbing material, by a blower which provides suction, or a combination of both.

Abstract: A method and apparatus for reproducing color images on the electrophotographic printing machine with liquid developer, wherein there is enabled with such developers in embodiments excellent fixing characteristics especially when the developed image being in two distinct liquid phases is transferred from an intermediate substrate to the final substrate, such as paper. In embodiments of the present invention there is provided developers and processes for achieving high fix. The liquid developed image is concentrated to 30 to 45 percent solid by removing carrier liquid and thereafter heated on the intermediate substrate.

Abstract: An image forming apparatus and method in which the flow of a toner image formed on an image carrier is prevented at the time of removing a surplus liquid developer and at the time of transfer of the image onto a transfer material. The apparatus includes an image carrier, a device for forming an electrostatic latent image on a surface of the image carrier, and a developing section for supplying a liquid developer onto the electrostatic latent image so as to form a toner image. The apparatus also includes a device for removing a surplus liquid developer remaining on the surface of the image carrier after the toner image is formed. A transfer device transfers the toner image onto a surface of a transfer material. An electric charge giving device, which is disposed between the developing section and the device for removing the surplus liquid developer, applies an electric charge to the toner image in a same polarity as that of the toner image.

Abstract: A system for conditioning liquid ink made up of toner particles immersed in a liquid carrier medium being delivered to or on an image bearing surface in a multicolor electrostatographic printing machine of the type utilizing liquid developing material, particularly an image-on-image type liquid ink multicolor system. The liquid ink conditioning system includes a first member for electrostatically compressing or compacting the toner particles towards or on the image bearing surface. A second member is provided downstream from the first member for removing excess liquid from the compressed liquid ink layer.

Abstract: An imaging system and method incorporate an apparatus and method for cleaning developer liquid from an imaging substrate such as a photoreceptor.

Abstract: An apparatus for removing back-plated developer from a development device includes a shaft, cleaning media mounted about the outer surface of the shaft, means for loading the cleaning media against the development device, and means for rotating the shaft and the cleaning media, wherein the cleaning media removes back-plated developer from the development device. The cleaning media may include a fiber material having a plurality of flow paths. A fluid flow means can be provided to deliver a cleaning liquid to the cleaning media to flush at least a portion of the removed back-plated developer from the cleaning media.

Abstract: The present invention provides an image recording apparatus and an excess liquid developer removing device used in the apparatus. In the image recording apparatus, the recording medium wound around the rotary drum is developed by liquid developer supplied from a developing device. A dish provided on the developing device is displaced in the vicinity of the recording medium wound around the rotary drum by being declined in a predetermined angle to prevent the bubbles from generating. The excess liquid developer attached on the recording medium is removed by the air from a nozzle of a blower. The nozzle is displaced by a nozzle displacing device in the vicinity of a developing electrode for supplying the liquid developer only in the midst of developing to prevent the nozzle from being chocked up with toner contained in the liquid developer.

Abstract: An imaging system and method incorporate an apparatus and method for cleaning developer liquid from an imaging substrate such as a photoreceptor.