Process and apparatus for manufacturing migration imaging members

Abstract: A process and apparatus for preparing migration imaging members are disclosed. Two substrates (144,154) with softenable layers (146,156) applied to them travel through a vacuum chamber (108) where they are simultaneously exposed (160) to vapor deposition of the migration marking material (162,164). After the migration marking material is deposited, the two softenable layers are laminated together (174,176) in the same vacuum chamber to form the migration imaging member. In one of the embodiments, the softenable layers are applied to the substrates in the same sweep of the substrate through the vacuum chamber vapor deposition and lamination steps.

Description: The present invention is directed to migration imaging members. Migration imaging systems capable of producing high quality images of high optical contrast density and high resolution have been developed. Such migration imaging systems are disclosed in, for example, US-A-3,975,195, US-A-3,909,262, US-A-4,536,457, US-A-4,536,458, US-A-4,013,462, and "Migration Imaging Mechanisms, Exploitation, and Future Prospects of Unique Photographic Technologies, XDM and AMEN", P.S. Vincett, G.J. Kovacs, M.C. Tam, A.L. Pundsack, and P.H. Soden, Journal of Imaging Science 30 (4) July/August, pp. 183 - 191 (1986). Migration imaging members containing charge transport materials in the softenable layer are also known, and are disclosed, for example, in US-A-4,536,457 and US-A-4,536,458. In a typical embodiment of these migration imaging systems, a migration imaging member comprising a substrate, a layer of softenable material, and photosensitive marking material is imaged by first forming a latent image by electrically charging the member and exposing the charged member to a pattern of activating electromagnetic radiation such as light. Where the photosensitive marking material is originally in the form of a fracturable layer contiguous with the upper surface of the softenable layer, the marking particles in the exposed area of the member migrate in depth toward the substrate when the member is developed by softening the softenable layer. The expression "softenable" as used herein is intended to mean any material which can be rendered more permeable, thereby enabling particles to migrate through its bulk. Conventionally, changing the permeability of such material or reducing its resistance to migration of migration marking material is accomplished by dissolving, swelling, melting, or softening, by techniques, for example, such as contacting with heat, vapors, partial solvents, solvent vapors, solvents, and combinations thereof, or by otherwise reducing the viscosity of the softenable material by any suitable means. The expression "fracturable" layer or material as used herein means any layer or material which is capable of breaking up during development, thereby permitting portions of the layer to migrate toward the substrate or to be otherwise removed. The fracturable layer is preferably particulate in the various embodiments of the migration imaging members. Such fracturable layers of marking material are typically contiguous to the surface of the softenable layer spaced apart from the substrate, and such fracturable layers can be substantially or wholly embedded in the softenable layer in various embodiments of the imaging members. The expression "contiguous" as used herein is intended to mean in actual contact, touching, also, near, though not in contact, and adjoining, and is intended to describe generically the relationship of the fracturable layer of marking material in the softenable layer with the surface of the softenable layer spaced apart from the substrate. The expression "optically sign-retained" as used herein is intended to mean that the dark (higher optical density) and light (lower optical density) areas of the visible image formed on the migration imaging member correspond to the dark and light areas of the illuminating electromagnetic radiation pattern. The expression "optically sign-reversed" as used herein is intended to mean that the dark areas of the image formed on the migration imaging member correspond to the light areas of the illuminating electromagnetic radiation pattern and the light areas of the image formed on the migration imaging member correspond to the dark areas of the illuminating electromagnetic radiation pattern. The expression "optical contrast density" as used herein is intended to mean the difference between maximum optical density (D max ) and minimum optical density (D min ) of an image. Optical density is measured for the purpose of this invention by diffuse densitometers with a blue Wratten No. 94 filter. The expression "optical density" as used herein is intended to mean "transmission optical density" and is represented by the formula: D = log 10 [l o /l] where I is the transmitted light intensity and l o is the incident light intensity. For the purpose of this invention, all values of transmission optical density given in this invention include the substrate density of about 0.2 which is the typical density of a metallized polyester substrate. There are various other systems for forming such images, wherein non-photosensitive or inert marking materials are arranged in the aforementioned fracturable layers, or dispersed throughout the softenable layer, as described in the aforementioned patents, which also disclose a variety of methods which can be used to form latent images upon migration imaging members. Various means for developing the latent images can be used for migration imaging systems. These development methods include solvent wash away, solvent vapor softening, heat softening, and combinations of these methods, as well as any other method which changes the resistance of the softenable material to the migration of particulate marking material through the softenable layer to allow imagewise migration of the particles in depth toward the substrate. In the solvent wash away or meniscus development method, the migration marking material in the light struck region migrates toward the substrate through the softenable layer, which is softened and dissolved, and repacks into a more or less monolayer configuration. In migration imaging films supported by transparent substrates alone, this region exhibits a maximum optical density which can be as high as the initial optical density of the unprocessed film. On the other hand, the migration marking material in the unexposed region is substantially washed away and this region exhibits a minimum optical density which is essentially the optical density of the substrate alone. Therefore, the image sense of the developed image is optically sign reversed. Various methods and materials and combinations thereof have previously been used to fix such unfixed migration images. One method is to overcoat the image with a transparent abrasion resistant polymer by solution coating techniques. In the heat or vapor softening developing modes, the migration marking material in the light struck region disperses in the depth of the softenable layer after development and this region exhibits D min which is typically in the range of 0.6 to 0.7. This relatively high D min is a direct consequence of the depthwise dispersion of the otherwise unchanged migration marking material. On the other hand, the migration marking material in the unexposed region does not migrate and substantially remains in the original configuration, i.e. a monolayer. In known migration imaging films supported by transparent substrates, this region exhibits a maximum optical density (D max ) of about 1.8 to 1.9. Therefore, the image sense of the heat or vapor developed images is optically sign-retained. Various techniques are used to deposit the migration imaging material onto the surface of the softenable layer. One technique is described in US-A-3,598,644, and involves vacuum deposition of migration marking material onto the surface of a softenable layer by positioning a heat softened layer opposite a source of migration marking material vapors, such as selenium, which produces particles of migration marking material on the surface of the softenable layer. Another deposition technique is described in US-A-4,482,622, which teaches a multistage deposition process of evaporating selenium onto a softenable layer of a migration imaging member. This is accomplished by heating the surface of the softenable layer to soften the surface, contacting the surface at a high impingement rate in a first deposition zone with selenium vapors to form a sub-surface monolayer of spherical particles and moving the surface to a second deposition zone. At the second deposition zone the surface is contacted at a low impingement with selenium vapors which increases the size of the spherical particles and optical density while maintaining a narrow size distribution and achieving a high surface packing density. There are various known methods for pressing two softenable layers together. US-A-3,741,758 shows a process for removing background migration material from an image member comprising a layer of softenable material and migration material in the softenable material. Once the image member is exposed, the background particles and contiguous portions are extruded and sheared by passing the image member with the softenable layer at the proper viscosity through a pressure nip where some of the softenable material is extruded in front of the nip carrying with it the unmigrated particles. A second member with a substrate and softenable layer is also extruded at the roller so that a puddle is formed across the image member which aids in the extruding process. Another method for pressing two softenable layers together is disclosed in US-A-3.840,397 which teaches a particle placing system where particulate material is placed in or on a softenable layer by pressing a donor uniformly coated with particulate matter in softenable material against a free surface of a softenable layer. The donor and free surface members are in the form of a continuous web advancing from supply rolls past a pressure roller transfer station where the donor material is pressed into contact with the free surface member. As the members continue to advance, the members are stripped apart as layers, the free surface member having picked up the particles from the donor member. Multiple layer migration imaging systems are known as taught by US-A-3,982,939 (Bean). These systems use batch coating methods to coat the various layers onto the substrate. It is also known to laminate polymer layers with vacuum deposited metal layers in a vacuum. US-A-5,260,095 discloses formation of polymer layers under a vacuum which improves material and surface characteristics. More specifically, this patent teaches the use of "standard" polymer layer-making equipment that is generally used in an atmospheric environment in a vacuum. Additional layers of polymer or metal may be vacuum deposited onto the solid polymer layers in the vacuum. While known imaging members and imaging processes are suitable for their intended purposes, a need remains for improved migration imaging members. In addition, a need remains for migration imaging members with improved optical contrast density. Further, there is a need for migration imaging members wherein the optical density of the D max areas of the imaged member is increased without a corresponding increase in the optical density of the D min areas of the imaged member. Additionally, there is a need for migration imaging members wherein the optical density of the D max areas of the imaged member with respect to ultraviolet light passing through the imaging member is increased without a corresponding increase in the optical density of the D min areas of the imaged member with respect to ultraviolet light passing through the imaging member. There is a great need for improved processing of imaging members. In conventional film manufacturing processes, the various layers are usually applied sequentially with drying occurring between each coating step. The number of coating steps has a large impact on the manufacturing yield and consequently cost. It is also desirable to overcome the difficulties of the lamination process due to air being trapped between the two layers. The air bubbles cause defects as well as breakdown and trapping at the lamination interface. The trapped charge can sensitize the migration imaging particles when they are exposed to light which results in sporatic migration when the film is subsequently heated in the image development process. It is an object of the present invention to provide a process and apparatus for manufacturing migration imaging members which meet these needs. The present invention provides a process for preparing a migration imaging member, comprising: applying a first softenable layer (146) to a first substrate (144) and a second softenable layer (156) to a second substrate (154); softening (170,172) the first and second softenable layers and; contacting the first softenable layer and the second softenable layer in a deposition zone in a vacuum chamber with vapors (160) comprising a migration marking material so that the migration marking material is simultaneously deposited (162,164) on the first softenable layer and the second softenable layer. The present invention further provides an apparatus for preparing a migration imaging member comprising: a vacuum chamber (108); means (190,192) for moving a first and a second substrate (144,154) though said vacuum chamber; means (160) for vapor depositing a material (162,164) simultaneously on the first substrate and the second substrate. Preferred embodiments of the present invention are set forth in the daims. A process and apparatus in accordance with the invention will now be described, by way of example, with reference to the accompanying dawings, in which: Figures 1, 2, and 3 illustrate schematically migration imaging members prepared by the process according to the present invention. Figures 4 and 5 illustrate schematically portions of processes for preparing migration imaging members according to the present invention. Figures 6, 7, and 8 illustrate schematically processes for imaging and developing a migration imaging member according to the present invention. Figures 9A, 9B, 10A, 10B, 11A, 11B. 11C, 12A, 128, 13A, 138, 13C, 14A, and 148 illustrate schematically processes for imaging and developing migration imaging members according to the present invention containing an infrared or red-light sensitive layer by imagewise exposure to infrared or red light. Figure 15 illustrates schematically another process for preparing migration imaging members. Figure 16 illustrates schematically yet another process for preparing migration imaging members. The migration imaging member of the present invention comprises a substrate, a first softenable layer comprising a first softenable material and a first migration marking material contained at or near the surface of the first softenable layer spaced from the substrate, and a second softenable layer comprising a second softenable material and a second migration marking material. The migration marking material in the second softenable layer can be situated at any location within the layer. For example, as shown in Figures 1, 2, and 3, the second migration marking material can be situated at or near the surface of the second softenable layer in contact with the first softenable layer. Alternatively, the second migration marking material can be situated at or near the surface of the second softenable layer most distant from the substrate. Any other possible variations are also suitable. As illustrated schematically in Figure 1, migration imaging member 1 comprises in the order shown a substrate 4, an optional adhesive layer 5 situated on substrate 4, an optional charge blocking layer 7 situated on optional adhesive layer 5, an optional charge transport layer 9 situated on optional charge blocking layer 7, a first softenable layer 10 situated on optional charge transport layer 9, said first softenable layer 10 comprising first softenable material 11, optional first charge transport material 16, and first migration marking material 12 situated at or near the surface of the first softenable layer spaced from the substrate, and a second softenable layer 18 situated on first softenable layer 10 comprising second softenable material 19, optional second charge transport material 20, and second migration marking material 21 situated at or near the surface of second softenable layer 18 in contact with first softenable layer 10. Optional overcoating layer 17 is situated on the surface of the imaging member spaced from the substrate 4. As illustrated schematically in Figure 2, migration imaging member 2 comprises in the order shown a substrate 4, an optional adhesive layer 5 situated on substrate 4, an optional charge blocking layer 7 situated on optional adhesive layer 5, an optional charge transport layer 9 situated on optional charge blocking layer 7, a first softenable layer 10 situated on optional charge transport layer 9, said first softenable layer 10 comprising first softenable material 11, first optional charge transport material 16, and first migration marking material 12 situated at or near the surface of the first softenable layer spaced from the substrate, a second softenable layer 18 situated on first softenable layer 10 comprising second softenable material 19, optional second charge transport material 20, and second migration marking material 21 situated at or near the surface of second softenable layer 18 in contact with first softenable layer 10, and an infrared or red light radiation sensitive layer 13 situated on second softenable layer 18 comprising infrared or red light radiation sensitive pigment particles 14 optionally dispersed in polymeric binder 15. Alternatively (not shown), infrared or red light radiation sensitive layer 13 can comprise infrared or red light radiation sensitive pigment particles 14 directly deposited as a layer by, for example, vacuum evaporation techniques or other coating methods. Optional overcoating layer 17 is situated on the surface of the imaging member spaced from the substrate 4. As illustrated schematically in Figure 3, migration imaging member 3 comprises in the order shown a substrate 4, an optional adhesive layer 5 situated on substrate 4, an optional charge blocking layer 7 situated on optional adhesive layer 5, an infrared or red light radiation sensitive layer 13 situated on optional charge blocking layer 7 comprising infrared or red light radiation sensitive pigment particles 14 optionally dispersed in polymeric binder 15, an optional charge transport layer 9 situated on infrared or red light radiation sensitive layer 13, a first softenable layer 10 situated on optional charge transport layer 9, said first softenable layer 10 comprising first softenable material 11, first optional charge transport material 16, and first migration marking material 12 situated at or near the surface of the first softenable layer spaced from the substrate, and a second softenable layer 18 situated on first softenable layer 10 comprising second softenable material 19, optional second charge transport material 20, and second migration marking material 21 situated at or near the surface of second softenable layer 18 in contact with first softenable layer 10. Optional overcoating layer 17 is situated on the surface of imaging member 1 spaced from the substrate 4. Any or all of the optional layers and materials shown in Figures 1, 2, and 3 can be absent from the imaging member. In addition, the optional layers present need not be in the order shown, but can be in any suitable arrangement. The migration imaging member can be in any suitable configuration, such as a web, a foil, a laminate, a strip, a sheet, a coil, a cylinder, a drum, an endless belt, an endless mobius strip, a circular disc, or any other suitable form. The substrate can be either electrically conductive or electrically insulating. When conductive, the substrate can be opaque, translucent, semitransparent, or transparent, and can be of any suitable conductive material. When insulative, the substrate can be opaque, translucent, semitransparent, or transparent, and can be of any suitable insulative material. In addition, the substrate can comprise an insulative layer with a conductive coating, such as vacuum-deposited metallized plastic, such as titanized or aluminized Mylar® polyester, wherein the metallized surface is in contact with the softenable layer. It is desirable to have the substrate be easily releasable from the softenable layer. The manufacturing process requires that the softenable layer adhere reasonably well to the substrate, however easily peel away from the substrate when the substrate is removed from the softenable layer. The softenable layer must adhere to substrate well enough so as to allow the softenable layer to be loaded onto the substrate and then rolled and unrolled without the softenable layer being removed. Another consideration in applying the softenable layer releasably to the substrate is that the softenable layer cannot chemically react with the substrate. This is important so that the imaging properties of the softenable layer will not degrade due to such a chemical reaction. Many of the above mentioned substrates are "releasable" substrates, an aluminum/polyester substrate and an acrylic emulsion substrate or layer being examples. The substrate has any effective thickness, typically from 6 to 250 µm (microns), and preferably from 50 to 200 µm (microns), although the thickness can be outside of this range. The first and second softenable layers may be either of the same materials or of different materials, and can comprise one or more layers of softenable materials, which can be any suitable material, typically a plastic or thermoplastic material which is either heat softenable or soluble in a solvent or softenable, for example, in a solvent liquid, solvent vapor, heat, or any combinations thereof. When the softenable layer is to be softened or dissolved either during or after imaging, it should be soluble in a solvent that does not attack the migration marking material. By softenable is meant any material that can be rendered by a development step as described herein permeable to migration marking material migrating through its bulk. This permeability typically is achieved by a development step entailing dissolving, melting, or softening by contact with heat, vapors, partial solvents, as well as combinations thereof. Examples of suitable softenable materials include styrene-acrylic copolymers, such as styrene-hexylmethacrylate copolymers, styrene acrylate copolymers, styrene butylmethacrylate copolymers, styrene butylacrylate ethylacrylate copolymers, and styrene ethylacrylate acrylic acid copolymers, polystyrenes, including polyalphamethyl styrene, alkyd substituted polystyrenes, styrene-olefin copolymers, styrene-vinyltoluene copolymers, polyesters, polyurethanes, polycarbonates, polyterpenes, silicone elastomers, mixtures thereof, and copolymers thereof, as well as any other suitable materials as disclosed, for example, in US-A-3,975,195. The first softenable layer can be of any effective thickness, typically from 1 to 30 µm (microns), and preferably from 2 to 25 µm (microns), although the thickness can be outside of this range. The second softenable layer can be of any effective thickness, typically from 1 to 30 µm (microns), preferably from 2 to 25 µm (microns), more preferably from 1 to 10 µm (microns), and even more preferably from 2 to 5 µm (microns), although the thickness can be outside of this range. The first and second softenable layers can be applied to the substrate by any suitable process. Typical coating processes include draw bar coating, spray coating, extrusion, dip coating, gravure roll coating, wire-wound rod coating, air knife coating, and reverse roll coating. The softenable layers can also be added by a lamination process as described hereinbelow. The softenable layers also contain migration marking material, which may be either the same or different in the first and second softenable layers. The migration marking material is electrically photosensitive or photoconductive. In embodiments of the present invention wherein an infrared or red light sensitive layer is also present in the imaging member, the migration marking material is sensitive to radiation at a wavelength other than that to which the infrared or red light sensitive pigment is sensitive; while the migration marking material may exhibit some photosensitivity in the wavelength to which the infrared or red light sensitive pigment is sensitive, it is preferred that photosensitivity in this wavelength range be minimized so that the migration marking material and the infrared or red light sensitive pigment exhibit absorption peaks in distinct, different wavelength regions. The migration marking materials preferably are particulate, wherein the particles are closely spaced from each other. Preferred migration marking materials generally are spherical in shape and submicron in size. The migration marking material generally is capable of substantial photodischarge upon electrostatic charging and exposure to activating radiation and is substantially absorbing and opaque to activating radiation in the spectral region where the photosensitive migration marking particles photogenerate charges. The migration marking material is preferably present in the first softenable layer as a thin layer or monolayer of particles situated at or near the surface of the first softenable layer spaced from the substrate, although the migration marking material may also be dispersed throughout the first softenable layer. In the second softenable layer the migration marking material can be present either as a dispersion or as a monolayer of particles. Preferably, the migration marking material is present in both the first softenable layer and in the second softenable layer as a monolayer of particles because this configuration enables the highest possible D max values for the lowest mass of migration marking material, and may also enable very low D min values. In this embodiment, it is preferred that the monolayer of particles be situated in the first softenable layer at or near the surface spaced from the substrate, while the monolayer of particles in the second softenable layer can be situated at or near the surface of the second softenable layer in contact with the first softenable layer, or at or near the surface of the second softenable layer most distant from the substrate, or at any other location within the layer. Alternatively, either one or both of the softenable layers can contain dispersions of migration marking material. When present as particles, the particles of migration marking material preferably have an average diameter of up to 2 µm (microns), and more preferably of from 0.1 to 1 µm (micron). The layer of migration marking particles in the first softenable layer is situated at or near that surface of the first softenable layer spaced from or most distant from the substrate. Typically, the particles are situated at a distance of from 0.01 to 0.1 µm (micron) from the layer surface, although the distance can be outside this range. Preferably, the particles are situated at a distance of from 0.005 to 0.2 µm (micron) from each other, and more preferably at a distance of from 0.05 to 0.1 µm (micron) from each other, the distance being measured between the closest edges of the particles, i.e. from outer diameter to outer diameter. The migration marking material contiguous to the outer surface of the softenable layer is present in any effective amount, preferably from 2 percent to 25 percent by total weight of the softenable layer, and more preferably from 5 to 20 percent by total weight of the softenable layer. Examples of suitable migration marking materials include selenium, alloys of selenium with alloying components such as tellurium, arsenic, and mixtures thereof, and any other suitable materials as disclosed, for example, in US-A-3,975,195. The migration marking particles can be included in the imaging members by any suitable technique. For example, a layer of migration marking particles can be placed at or just below the surface of a softenable layer by solution coating a substrate containing the softenable layer material, followed by heating the softenable material in a vacuum chamber to soften it, while at the same time thermally evaporating the migration marking material onto the softenable material in the vacuum chamber. Other techniques for preparing monolayers include cascade and electrophoretic deposition. An example of a suitable process for depositing migration marking material in the softenable layer is disclosed in US-A-4,482,622. One preferred method for preparing imaging members of the present invention entails preparing a portion of the imaging member comprising the substrate and, coated thereon, the first softenable layer comprising the first softenable material, first migration marking material, and optional first charge transport material. The second softenable layer comprising the second softenable material, second migration marking material, and optional second charge transport material is coated onto a support, optionally coated with a release agent. This support can be of any suitable material, such as paper, polyester or other polymeric films, or the like. It is preferred for the support to be of minimum thickness to enable greatest possible surface area of the support coated with the second softenable material for a roll of given diameter of the coated support; minimum thickness of the support is also preferred for cost and recycling purposes. The optional release agent controls or reduces adhesion between the support and the second softenable layer. Examples of suitable release agents include long-chain alkyl derivatives, natural products, synthetic polymers, fluorinated compounds, and inorganic materials. Silicone release agents are common. In some instances, the release agent is cured by exposure to ultraviolet light. Fluorocarbons such as polytetrafluoroethylene are also available but are relatively expensive. Highly cross-linked thermoset materials are also suitable release materials. When the second migration marking material is to be added to the second softenable layer by a vacuum evaporation process, the second softenable material and optional second charge transport material are coated onto the support, followed by vacuum evaporation of the migration marking material onto the second softenable material to form the second softenable layer. The first and second softenable layers are then brought into contact with each other so that the first softenable material and second softenable material are in intimate contact. Heat and/or pressure and/or solvent vapors can be applied to the substrate and/or the support while the first and second softenable layers are in intimate contact, causing the first softenable layer to adhere to the second softenable layer. Thereafter, the support is removed from the second softenable layer. As illustrated schematically in Figure 4 (not drawn to scale), migration imaging member 41 comprising substrate 43 and first softenable layer 45, which comprises first softenable material 47 and first migration marking material 49, passes around optional idling roller 51 and then around roller 53. Support 55 has coated thereon second softenable layer 57, which comprises second softenable material 59 and second migration marking material 61. Support 55 bearing second softenable layer 57 passes around optional idling roller 63 and then around roller 65. Preferably, either one or both of rollers 53 and 65 are heated. Rollers 53 and 65 are situated with respect to each other so as to form a nip, such that pressure is applied to first softenable layer 45 and second softenable layer 57 while they are in intimate contact with each other. Thereafter, subsequent to exiting the nip formed by rollers 53 and 65, second softenable layer 57 adheres to first softenable layer 45 and support 55 is peeled away from second softenable layer 57. Support 55 then passes around optional idling roller 67 and the migration imaging member 41, which now comprises substrate 43, first softenable layer 45, and second softenable layer 57, then passes around optional idling roller 69. The temperature of rollers 53 and 65 and the pressure in the nip created by rollers 53 and 65 is selected so that second softenable layer 57 preferentially adheres to whichever layer is situated topmost on substrate 43 (which is first softenable layer 45 as illustrated in Figure 4) subsequent to exiting the nip, and so that support 55 can be removed as cleanly as possible from second softenable layer 57, with little or no residual second softenable material 59 adhering to support 55 subsequent to exiting the nip. Preferred temperatures for rollers 53 and/or 65 typically are from 80°C to 120°C, and more preferably from 90°C to 110°C, although the temperature can be outside these ranges. Preferred pressures within the nip between rollers 53 and 65 typically are from 7.0·10 2 to 5.6·10 5 Pa (0.007 to 5.6 Kg.cm -2 ), although the pressure can be outside this range. In one specific embodiment of the present invention, roller 53 is heated to a temperature of 93 to 110°C, roller 63 is not heated, and the pressure created between roller 53 and roller 65 is about 4.2·10 5 Pa (4.2 Kg.cm -2 ). In embodiments wherein both rollers 53 and 65 are heated, they can be heated either to the same temperature or to different temperatures. Alternatively, as illustrated schematically in Figure 5 (not drawn to scale), migration imaging member 41 comprising substrate 43 and first softenable layer 45, which comprises first softenable material 47 and first migration marking material 49, passes around optional idling roller 71 and then around roller 73. Support 55 has coated thereon second softenable layer 57, which comprises second softenable material 59 and second migration marking material 61. Support 55 bearing second softenable layer 57 passes around optional idling roller 75 and then around roller 77. Preferably, either one or both of rollers 73 and 77 are heated. Rollers 73 and 77 are situated with respect to each other so as to form a nip, such that pressure is applied to first softenable layer 45 and second softenable layer 57 while they are in intimate contact with each other. Thereafter, subsequent to exiting the nip formed by rollers 73 and 77, second softenable layer 57 adheres to first softenable layer 45. The "sandwich" created by, in the order shown, substrate 43, first softenable layer 45, second softenable layer 57, and support 55 continues moving and enters the nip created between rollers 79 and 81, either or both of which may or may not be heated. Subsequent to exiting the nip formed by rollers 79 and 81, support 55 is peeled away from second softenable layer 57. Support 55 then passes around optional idling roller 83 and the migration imaging member 41, which now comprises substrate 43, first softenable layer 45, and second softenable layer 57, then passes around optional idling roller 85. The temperature of rollers 73 and 77 and the pressure in the nip created by rollers 73 and 77 is selected so that second softenable layer 57 preferentially adheres to whichever layer is situated topmost on substrate 43 (which is first softenable layer 45, as shown in Figure 5) subsequent to exiting the nip. The temperature of rollers 79 and 81 and the pressure in the nip created by rollers 79 and 81 is selected so that support 55 can be removed as cleanly as possible from second softenable layer 57, with little or no residual second softenable material 59 adhering to support 55 subsequent to exiting the nip. Preferred temperatures for both sets of rollers typically are from 80°C to 120°C, and more preferably from 90°C to 110°C, although the temperature can be outside these ranges. Preferred pressures within the nips between both sets of rollers typically are from 7.0·10 2 to 5.6·10 5 Pa (0.007 Kg.cm -2 to 5.6 Kg.cm -2 ), although the pressure can be outside this range. This embodiment is particularly preferred when the materials selected for the first softenable layer, second softenable layer, support, and optional release material situated between the support and the second softenable layer are such that the optimum temperature and/or pressure for effecting adhesion between the first softenable layer and the second softenable layer is different from the optimum temperature and/or pressure for effecting separation of the support from the second softenable layer. With respect to rollers 73 and 77, one or both rollers may be heated to either the same temperature or to different temperatures. Similarly with respect to rollers 79 and 81, one or both rollers may be heated to either the same temperature or to different temperatures. Figure 15 shows another embodiment of the invention in which the migration marking material is deposited in the same vacuum chamber as the laminating process. The migration marking material is deposited on two sheets at the same time just before the two layers are laminated together. Simultaneously depositing the migration marking material on the two softenable layers results in less processing steps than the traditional deposition methods. Laminating the two sheets in a vacuum will overcome the problems of air entrapment at the lamination interface. The deposition and lamination steps take place in vacuum chamber 108 which operates at a vacuum pressure in the range between 13.3 Pa to 1.33·10 -8 Pa (10 -1 to 10 -10 torr) or better, preferably in the 1.33·10 -1 to 1.33·10 -2 Pa (10 -3 to 10 -4 torr) range. Outlet 130 shows the connection between the main vacuum chamber and a vacuum pump (not shown). In the vacuum chamber there are two supply rolls 140 and 150 which supply a receiver member 142 and a donor member 152 to the process described above. The supply rolls may also be located outside of the vacuum chamber. The receiver/donor relationship terminology is used to distinguish the member which is to be imaged (receiver) and the member which provides the support for the second softenable layer (donor). The receiver member is comprised of a substrate 144 and a softenable layer 146 and the donor member is comprised of a substrate 154 and a softenable layer 156. The substrate, softenable layer and migration marking materials used are the same as described earlier. A vapor deposition source 160 is also located in the vacuum chamber. The vapor deposition source deposits migration marking material 162 and 164 on the receiver and donor softenable layers respectively. An example of a suitable process for depositing migration marking material in the softenable layer is disclosed in US-A-3,598,644 and US-A-4,482,622. There may be more than one vapor deposition source with different migration marking materials deposited from each source. As required by the vapor deposition process, the members are heated by heated rollers 170 and 172 to a temperature of approximately 50° C to 135°C, preferably 90°C to 125°C, although the temperatures may be outside of this range, so that the softenable layers 146 and 156 are softened. The rollers may be the same or different temperatures and are located so that the two members may pass through the two rollers without touching. The migration marking materials 162 and 164 are then deposited on the the softenable layers 146 and 156. Immediately after the migration marking materials are deposited, the members are laminated together. The temperature at which the migration marking material is deposited is very close to the temperature at which the the members are laminated. In order to laminate the members together, the members must pass through rollers 174 and 176. Rollers 174 and 176 are situated with respect to each other so as to form a nip, such that pressure is applied to first softenable layer 146 and second softenable layer 156 while they are in intimate contact with each other. Preferred temperatures for rollers 174 and 176 are from 50°C to 135°C, and more preferably from 90°C to 125°C, although the temperature can be outside these ranges and one or both of the rollers may be heated. If both rollers are heated they may be heated to either the same temperature or different temperatures. Preferred pressures within the nip between rollers 174 and 176 typically are from 7.0·10 2 to 7.0·10 5 Pa (0.007 to 7.0 Kg.cm -2 ), although the pressure can be outside this range. In one specific embodiment of the present invention, rollers 174 and 176 are heated to a temperature of about 105°C and the pressure created between rollers 174 and 176 is 2.8·10 5 to 4.2·10 5 Pa (2.8-4.2 Kg.cm -2 ). Following the lamination process the laminated member passes through optional guide rollers 178 and 179 and the donor substrate 154 is peeled from the softenable layer 156 to produce the desired imaging member. The imaging member is taken up by roll 190 and the donor substrate is taken up by roll 192 as shown. Another embodiment of the invention shown in FIG. 16 provides for the supply rolls to be located outside of the vacuum chamber so that the substrate may be coated with the softenable layer in the same sweep of the substrate as the deposition and lamination steps. Coating the substrate with the softenable layer in this manner allows for a more efficient process than the previous batch processing where the substrate is coated in a separate process. This embodiment also shows delaminating and laminating the substrates steps in a single apparatus. The additional lamination/delamination steps results in the manufacturing process having as little waste as possible because the substrates 144 and 154 can be thinner than the finished imaging member substrate 149. An added benefit of the substrate delamination/lamination process is that imaging substrate 149 has not been exposed to the heat and pressures of the deposition and lamination processes. The main vacuum chamber is a differentially pumped vacuum and has additional air lock chambers 104, 105 and 106. The air lock chambers operate at a lower vacuum than the main vacuum chamber at preferably 13.3 Pa (10 -1 torr). Outlets 132, 134 and 136 show the connections between air lock chambers 104, 105 and 106 to their respective vacuum pumps (not shown). Outside of the vacuum chamber are located supply rolls 145 and 155 which supply the substrate for the donor and receiver members respectively. As the substrates travel towards the vacuum chamber, each substrate has a softenable layer applied; at applying station 148 for the receiver substrate and at applying station 158 for the donor substrate. Any of the optional layers may also be applied in the applying stations. The applying stations may be located inside or outside of the vacuum chamber. As disclosed earlier, the softenable layers can be applied to the substrate by any suitable process which include spray coating, extrusion, gravure roll coating, wire-wound rod coating, air knife coating and reverse roll coating. Other softenable layer application methods can include vacuum deposition and sputtering in inert gases. The optional layers may also be applied to the substrate by using either batch or sequential application methods. The receiver member comprising substrate 144 and first softenable layer 146 enters air lock 105 at entrance 110 and the main vacuum chamber at entrance 112, while the donor member comprising support member 154 and second softenable layer 156 enters air lock 104 at entrance 114 and the main vacuum chamber at entrance 116. The deposition and lamination process is the same as that described above for FIG. 15 FIG. 16 shows an additional vapor deposition source 166. A partition 168, separates the two deposition sources so that only material from vapor deposition source 166 is deposited on softenable layer 146 and only material from vapor deposition source 160 is deposited on softenable layer 156. The migration marking material deposited by vapor deposition source 166 may be the same or different than the migration marking material deposited by vapor deposition source 160 depending upon the desired qualities of the finished imaging member. Air lock chamber 106 contains the substrate delaminating and laminating processes. The laminated member passes from the main vacuum chamber and enters air lock 106 at entrance 118. As shown in the drawings, the substrates 144 and 154 are "releasably" attached substrates so that the substrates are easily peeled from the softenable layers. When a non-releasable substrate is used, an additional releasing step will be necessary . Such releasing step can include heating the rollers to a sufficient temperature to soften the softenable layers so that the substrates can be peeled from the softenable layer. The donor and receiver substrates may be removed in any order. FIG. 16 shows the receiver substrate 144 as the first disposable substrate to be delaminated or removed. The delaminated receiver substrate passes over guide roll 180 before it exits the air lock chamber at 122 and is taken up by a substrate roll (not shown). As explained above, substrates 144 and 154 are very thin, in the 12.5 to 100 µm (micron) range for the softenable layers laminating process, while the imaging member substrate is in the 75 to 500 µm (micron) range which is required for further processing of the imaging member. The laminated member continues to pass through air lock 106 until it is captured by rollers 182 and 184. At this position an imaging member substrate 149 which enters the air lock chamber at 124 from a supply roll (not shown) is laminated or attached to softenable layer 146 in substantially the same manner as the laminating process between rollers 174 and 176, however only the surface of exposed softenable layer 146 needs to be softened. After imaging member substrate 149 is adhered to the laminated member, the member exits the air lock at 120. The donor substrate 154 is then peeled from the laminated member as it passes over guide roll 188 to a take-up roll 196. This produces the imaging member which has two softenable layers on a handable substrate. The imaging member passes over guide roll 186 as it travels to its take-up roll 194. The rollers can be heated by any suitable method. For example, the rollers can have hollow cores and a heated liquid, such as oil or water, can be circulated through the cores. A heater can also be situated inside of the heated roller. Any of the methods known for heating fuser rolls in electrophotographic imaging devices can also be employed to heat the rollers. One or both of the softenable layers can also be heated by any desired method, such as exposure to radiation or illumination. Typically, in the processes illustrated in Figures 4, 5, 15 and 16, the imaging member passes between the rollers at speeds of from 0.152 to 1.52 m.s -1 , although the speed can be outside this range. If desired, a third softenable layer containing a third softenable material and a third migration material, which may be the same as or different from the materials in the first and second softenable layers, can be added to the imaging member, as well as additional softenable layers as desired. Alternatively (not shown), both the first softenable layer and the second softenable layer can be coated onto supports optionally coated with a release agent. The first and second softenable layers can then be laminated to each other as described above, followed first by removal of one of the supports and lamination of the first layer-second layer laminate to another layer within the imaging member structure, such as the substrate, and then secondly followed by removal of the other support and, if desired, subsequent lamination of the surface of the first layer-second layer laminate thus exposed to another layer within the imaging member structure, such as an infrared or red-light sensitive layer. Layers of the imaging member can thus be applied to each other by solvent coating processes, lamination processes, or any other suitable process. When present, the infrared or red light sensitive layer generally comprises a pigment sensitive to infrared and/or red light radiation. While the infrared or red light sensitive pigment may exhibit some photosensitivity in the wavelength to which the migration marking material is sensitive, it is preferred that photosensitivity in this wavelength range be minimized so that the migration marking material and the infrared or red light sensitive pigment exhibit absorption peaks in distinct, different wavelength regions. This pigment can be deposited as the sole or major component of the infrared or red light sensitive layer by any suitable technique, such as vacuum evaporation. An infrared or red light sensitive layer of this type can be formed by placing the pigment and the imaging member comprising the substrate and any previously coated layers into an evacuated chamber, followed by heating the infrared or red light sensitive pigment to the point of sublimation.. The sublimed material recondenses to form a solid film on the imaging member. Alternatively, the infrared or red light sensitive pigment can be dispersed in a polymeric binder and the dispersion coated onto the imaging member to form a layer. In another embodiment, the infrared or red light sensitive pigment can be dispersed within the softenable material of one of the softenable layers. Examples of suitable red light sensitive pigments include perylene pigments such as benzimidazole perylene, dibromoanthranthrone, crystalline trigonal selenium, beta-metal free phthalocyanine, azo pigments, as well as mixtures thereof. Typical thicknesses for infrared or red light sensitive layers comprising a pigment and a binder are from 0.05 to 2 µm (microns), and preferably from 0.1 to 1.5 µm (microns), although the thickness can be outside this range. Typical thicknesses for infrared or red light sensitive layers consisting of a vacuum-deposited layer of pigment are from 20 to 200 nm, and preferably from 30 to 100 nm, although the thickness can be outside this range. The migration imaging members may contain a charge transport material in one or both of the softenable layers and may also contain a charge transport material in an optional separate charge transport layer. The charge transport material can be any suitable charge transport material. The charge transport material can be either a hole transport material (transports positive charges) or an electron transport material (transports negative charges). The sign of the charge used to sensitize the migration imaging member during preparation of the master can be of either polarity. Charge transporting materials such as diamine transport molecules are well known in the art. Particularly suitable are charge transport materials such as triarylamines, including tritolyl amine, of the formula as disclosed in, for example, US-A-3,240,597 and US-A-3,180,730, and substituted diarylmethane and triarylmethane compounds, including bis-(4-diethylamino-2-methylphenyl)-phenylmethane. of the formula as disclosed in, for example, US-A-4,082,551, US-A-3,755,310, US-A-3,647,431, GB-A-984,965, GB-A-980,879, and GB-A-1,141,666. In embodiments of the present invention wherein an infrared-sensitive layer is also present in the imaging member, at least one softenable layer generally contains a charge transport material, and preferably at least the layer situated closest to the substrate toward which the migration marking material will migrate (i.e., the first softenable layer as illustrated in Figures 2 and 3) contains a charge transport material. When the charge transport molecules are combined with an insulating binder to form the softenable layer, the amount of charge transport molecule which is used can vary depending upon the particular charge transport material and its compatibility (e.g. solubility) in the continuous insulating film forming binder phase of the softenable matrix layer and the like. The charge transport material can be present in the softenable material in any effective amount, generally from 5 to 50 percent by weight and preferably from 8 to 40 percent by weight. The charge transport material can be incorporated into the softenable layer by any suitable technique. For example, it can be mixed with the softenable layer components by dissolution in a common solvent. If desired, a mixture of solvents for the charge transport material and the softenable layer material can be employed to facilitate mixing and coating. The charge transport molecule and softenable layer mixture can be applied to the substrate by any conventional coating process. The optional charge transport layer can comprise any suitable film forming binder matenal. The specific charge transport molecule utilized in the charge transport layer of any given imaging member can be identical to or different from any optional charge transport molecule employed in the softenable layer. Similarly, the concentration of the charge transport molecule utilized in the charge transport spacing layer of any given imaging member can be identical to or different from the concentration of any optional charge transport molecule employed in the softenable layer. When the charge transport material and film forming binder are combined to form the charge transport spacing layer, the amount of charge transport material used can vary depending upon the particular charge transport material and its compatibility (e.g. solubility) in the continuous insulating film forming binder. Satisfactory results have been obtained using between 5 percent and 50 percent based on the total weight of the optional charge transport spacing layer, although the amount can be outside of this range. The charge transport material can be incorporated into the charge transport layer by similar techniques to those employed for the softenable layer. The optional adhesive layer can include any suitable adhesive material. Typical adhesive materials include copolymers of styrene and an acrylate, polyester resin such as DuPont 49000 (available from E.I. du Pont & de Nemours Company), copolymer of acrylonitrile and vinylidene chloride, polyvinyl acetate, polyvinyl butyral and mixtures thereof. The adhesive layer can have any effective thickness, typically from 0.05 to 1 µm (micron), although the thickness can be outside of this range. When an adhesive layer is employed, it preferably forms a uniform and continuous layer having a thickness of 0.5 µm (micron) or less to ensure satisfactory discharge during the xeroprinting process. It can also optionally include charge transport molecules. The optional charge blocking layer can be of various suitable materials, provided that the objectives of the present invention are achieved, including aluminum oxide, polyvinyl butyral, silane as well as mixtures thereof. This layer, which is generally applied by known coating techniques, is of any effective thickness, typically from 0.05 to 0.5 µm (micron), and preferably from 0.05 to 0.1 µm (micron), although the thickness can be outside of this range. The optional overcoating layer can be substantially electrically insulating, or have any other suitable properties. The overcoating preferably is substantially transparent, at least in the spectral region where electromagnetic radiation is used for imagewise exposure step in the master making process and for the uniform exposure step in the xeroprinting process. The overcoating layer is continuous and preferably of a thickness of up to 1 to 2 µm (microns). More preferably, the overcoating has a thickness of from 0.1 to 0.5 µm (micron) to minimize residual charge buildup. Overcoating layers greater than 1 to 2 µm (microns) thick can also be used. Typical overcoating materials include acrylic-styrene copolymers, methacrylate polymers, methacrylate copolymers, styrene-butylmethacrylate copolymers, butylmethacrylate resins, vinylchloride copolymers, fluorinated homo or copolymers, high molecular weight polyvinyl acetate, organosilicon polymers and copolymers, polyesters, polycarbonates, polyamides and polyvinyl toluene. If an optional overcoating layer is used on top of the softenable layer to improve abrasion resistance and if solvent softening is employed to effect migration of the migration marking material through the softenable material, the overcoating layer should be permeable to the vapor of the solvent used and additional vapor treatment time should be allowed so that the solvent vapor can soften the softenable layer sufficiently to allow the light-exposed migration marking material to migrate towards the substrate in image configuration. Solvent permeability is unnecessary for an overcoating layer if heat is employed to soften the softenable layer sufficiently to allow the exposed migration marking material to migrate towards the substrate in image configuration. Further information concerning the structure, materials, and preparation of migration imaging members is disclosed in US-A-3,975,195, US-A-3,909,262, US-A-4,536,457, US-A-4,536,458, US-A-4,013,462, US-A-4,883,731, US-A-4,123,283, US-A-4,853,307, US-A-4,880,715, and P.S. Vincett, G.J. Kovacs, M.C. Tam, A.L Pundsack, and P.H. Soden, Migration Imaging Mechanisms, Exploitation, and Future Prospects of Unique Photographic Technologies, XDM and AMEN, Journal of Imaging Science 30 (4) July/August, pp. 183 - 191 (1986). The migration imaging member of the present invention is imaged and developed to provide an imagewise pattern on the member. The imaged member can be used as an information recording and storage medium, for viewing and as a duplicating film, as a mask for exposing photosensitive lithographic printing plates, as a xeroprinting master in a xeroprinting process, or for any other desired purpose. The process for imaging an imaging member of the present invention as shown schematically in Figure 1 is illustrated schematically in Figures 6, 7, and 8. Figures 6, 7, and 8 illustrate schematically a migration imaging member comprising a conductive substrate layer 90 that is connected to a reference potential such as a ground, a first softenable layer 91 comprising first softenable material 92, first migration marking material 93, and optional first charge transport material 94, and a second softenable layer 95 comprising second softenable material 96, second migration marking material 97, and optional second charge transport material 98. As illustrated schematically in Figure 6, the member is uniformly charged in the dark to either polarity (negative charging is illustrated in Figure 6) by a charging means 99 such as a corona charging apparatus. As illustrated schematically in Figure 7, the charged member is then exposed imagewise to radiation 100 at a wavelength to which the migration marking materials 93 and 97 are sensitive. For example, when the first and second migration marking materials are both selenium particles, blue or green light can be used for imagewise exposure. Substantial photodischarge then occurs in the exposed areas. As illustrated schematically in Figure 8, subsequent to formation of a charge image pattern, the imaging member is developed by causing the first and second softenable materials to soften by any suitable means (in Figure 8, by uniform application of heat energy 101 to the member). The heat development temperature and time depend upon factors such as how the heat energy is applied (e g. conduction, radiation or convection), the melt viscosity of the softenable layers, thickness of the softenable layers, and the amount of heat energy. For example, at a temperature of 110°C to 130°C, heat need only be applied for a few seconds. For lower temperatures, more heating time can be required. When the heat is applied, the first and second softenable materials decrease in viscosity, thereby decreasing their resistance to migration of the marking materials 93 and 97 through the softenable layers 91 and 95. As shown in Figure 8, in areas 102 of the imaging member, wherein the migration marking materials have a substantial net charge, upon softening of the softenable layers 91 and 95, the net charge causes the charged marking material to migrate in image configuration towards the conductive layer 90 and disperse in the first softenable layer 91, resulting in a D min area. The uncharged migration marking particles in areas 103 of the imaging member remain essentially neutral and uncharged. Thus, in the absence of migration force, the unexposed migration marking particles remain substantially in their original position in softenable layers 91 and 95, resulting in a D max area. If desired, solvent vapor development can be substituted for heat development. Vapor development of migration imaging members is well known in the art. Generally, if solvent vapor softening is utilized, the solvent vapor exposure time depends upon factors such as the solubility of the softenable layers in the solvent, the type of solvent vapor, the ambient temperature, and the concentration of the solvent vapors. The application of either heat, or solvent vapors, or combinations thereof, or any other suitable means should be sufficient to decrease the resistance of the softenable materials of softenable layers 91 and 95 to allow migration of the migration marking materials 93 and 97 through softenable layers 91 and 95 in imagewise configuration. With heat development, satisfactory results can be achieved by heating the imaging member to a temperature of 100°C to 130°C for only a few seconds when the unovercoated softenable layers contain an 80/20 mole percent copolymer of styrene and hexylmethacrylate having an intrinsic viscosity of 0.179 dl/gm and N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine. The test for a satisfactory combination of time and temperature is to maximize optical contrast density and electrostatic contrast potential for xeroprinting. With vapor development, satisfactory results can be achieved by exposing the imaging member to the vapor of toluene for between 4 seconds and 60 seconds at a solvent vapor partial pressure of between 6.67·10 2 and 4.0·10 3 Pa (5 millimeters and 30 millimeters of mercury) when the unovercoated softenable layer contains an 80/20 mole percent copolymer of styrene and hexylmethacrylate having an intrinsic viscosity of 0.179 dl/gm and N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine. The imaging member illustrated in Figures 6, 7, and 8 is shown without any optional layers such as those illustrated in Figure 1. If desired, alternative imaging member embodiments, such as those employing any or all of the optional layers illustrated in Figure 1, can also be employed. The process for imaging an imaging member of the present invention as shown schematically in Figure 2 or Figure 3 by imagewise exposure to infrared or red radiation and developing a migration imaging member of the present invention is illustrated schematically in Figures 9A and 9B through 14A and 14B. The process illustrated schematically in Figures 9B, 10B, 11B, 11C, 12B, 13B, 13C, and 148 represents an embodiment of the present invention wherein the first and second softenable layers are situated between the infrared or red light sensitive layer and the substrate and both of the softenable layers contain a charge transport material capable of transporting charges of one polarity. In the process steps illustrated in Figures 98, 10B, 11B, 12B. and 138, the imaging member is charged to the same polarity as that which the charge transport materials in the softenable layers are capable of transporting; in the process steps illustrated schematically in Figures 11C and 13C, the imaging member is recharged to the polarity opposite to that which the charge transport materials are capable of transporting. In Figures 9B, 108, 116, 11C, 12B, 138, 13C, and 14B, the softenable materials in both softenable layers contain hole transport materials (capable of transporting positive charges). Figures 9A and 9B through 14A and 14B illustrate schematically a migration imaging member comprising a conductive substrate layer 22 that is connected to a reference potential such as a ground, an infrared or red light sensitive layer 23 comprising infrared or red light sensitive pigment particles 24 dispersed in polymeric binder 25, a first softenable layer 26 comprising first sohenable material 27, first migration marking material 28, and first charge transport material 30, and a second softenable layer 34 comprising second softenable material 36, second migration marking material 38, and second charge transport material 39. As illustrated in Figures 9A and B, the member is uniformly charged in the dark to either polarity (negative charging is illustrated in Figure 9A, positive charging is illustrated in Figure 9B) by a charging means 29 such as a corona charging apparatus. As illustrated schematically in Figures 10A and 10B, the charged member is first exposed imagewise to infrared or red light radiation 31. The wavelength of the infrared or red light radiation used is preferably selected to be in the region where the infrared or red-light sensitive pigments exhibit maximum optical absorption and maximum photosensitivity. When the softenable layers 26 and 34 are situated between the infrared or red light sensitive layer 23 and the radiation source 31, as shown in Figure 10A, the infrared or red light radiation 31 passes through the non-absorbing migration marking material 28 and 38 (which are selected to be substantially insensitive to the infrared or red light radiation wavelength used in this step) and exposes the infrared or red light sensitive pigment particles 24 in the infrared or red light sensitive layer. Absorption of infrared or red light radiation by the infrared or red light sensitive pigment results in substantial photodischarge in the exposed areas. Thus the areas that are exposed to infrared radiation become substantially discharged. As shown in Figure 10B, when the infrared or red light sensitive layer 23 is situated between the softenable layers 26 and 34 and the radiation source 31 and the member is charged to the same polarity as the charge transport materials in the softenable layers are capable of transporting, absorption of infrared or red light radiation by the infrared or red light sensitive pigment results in substantial photodischarge in the exposed areas. Thus the areas that are exposed to infrared radiation become substantially discharged. As illustrated schematically in Figures 11A and B, the charged member is subsequently exposed uniformly to activating radiation 32 at a wavelength to which the migration marking materials 28 and 38 are sensitive. For example, when both the first and second migration marking materials are selenium particles, blue or green light can be used for uniform exposure. As shown in Figure 11A, when layers 26 and 34 are situated above layer 23, the uniform exposure to radiation 32 results in absorption of radiation by the migration marking materials 28 and 38. (In the context of the present invention, "above" with respect to the ordering of the layers within the migration imaging member indicates that the layer is relatively nearer to the radiation source and relatively more distant from the substrate, and "below" with respect to the ordering of the layers within the migration imaging member indicates that the layer is relatively more distant from the radiation source and relatively nearer to the substrate.) In charged areas of the imaging member 35, the migration marking particles 28a and 38a acquire a negative charge as ejected holes (positive charges) discharge the surface charges, resulting in an electric field between the migration marking particles and the substrate. Areas 37 of the imaging member that have been substantially discharged by prior infrared or red light exposure are no longer sensitive, and the migration marking particles 28b and 38b in these areas acquire no or very little charge. As shown in Figure 11B, when the infrared or red light sensitive layer 23 is situated above the softenable layers 26 and 34 and the member is charged to the same polarity as the charge transport materials in the softenable layers are capable of transporting, uniform exposure to radiation 32 at a wavelength to which the migration marking materials 28 and 38 are sensitive is largely absorbed by the migration marking materials 28 and 38. The wavelength of the uniform light radiation is preferably selected to be in the region where the infrared or red-light sensitive pigments in layer 23 exhibit maximum light transmission and where the migration marking particles 28 and 38 exhibit maximum light absorption. Thus, in areas of the imaging member which are still charged, the migration marking particles 28a and 38a acquire a negative charge as ejected holes (positive-charges) transport through the softenable layers to the substrate. Areas 37 of the imaging member that have been substantially discharged by prior infrared or red light exposure are no longer light sensitive, and the migration marking particles 28b and 38b in these areas acquire no or very little charge. In the embodiment illustrated in Figure 11B, the resulting charge pattern is such that the imaging member cannot be developed by heat development, since there is no substantial electric field between the migration marking materials and the substrate. The imaging member with a charge pattern as illustrated in Figure 11B can be developed by a development process, such as solvent vapor exposure followed by heating, in which the non-charged particles agglomerate and coalesce into a few large particles, resulting in a D min region, and the non-charged particles, which repel each other because they bear like charges, are not agglomerated or coalesced and remain substantially in their original positions, resulting in a D max region, as disclosed in, for example, US-A-4,880,715. Satisfactory results can be achieved with a vapor exposure time of between 10 seconds and 2 minutes at about 21°C, followed by heating to a temperature between 80°C and 120°C for from 2 seconds to 2 minutes and with solvent vapor partial pressures of between 2.67·10 3 and 1.07·10 4 Pa (20 millimeters of mercury and 80 millimeters of mercury) when the solvent is methyl ethyl ketone and the softenable layer contains an 80/20 mole percent copolymer of styrene and hexylmethacrylate having an intrinsic viscosity of 0.179 deciliters per gram and N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine. However, heat development generally is preferred to vapor or solvent development for reasons of safety, speed, cost, simplicity, and easy implementation in a machine environment. As shown in Figure 11C, the imaging member is further subjected to uniform recharging to a polarity opposite to that which the charge transport materials in the softenable layers are capable of transporting (negative as illustrated in Figure 11C), resulting in the migration marking materials in areas of the imaging member which have not been exposed to infrared or red light radiation becoming negatively charged, with an electric field between the migration marking particles and the substrate, and areas of the imaging member previously exposed to infrared or red light radiation becoming charged only on the surface of the member. It is important to emphasize that in general, the step of imagewise exposing the member to infrared or red light radiation and the step of uniformly exposing the member to radiation at a wavelength to which the migration marking material is sensitive can take-place in any order. When the member is first imagewise exposed to infrared or red light radiation as illustrated in Figures 10A and 10B and subsequently uniformly exposed to radiation to which the migration marking materials are sensitive as illustrated in Figures 11A, 11B, and 11C, the process proceeds as described with respect to Figures 10A, 10B, 11A, 11B, and 11C. When the member is first uniformly exposed to radiation to which the migration marking materials are sensitive and subsequently imagewise exposed to infrared or red light radiation, the process proceeds as described with respect to Figures 12A, 12B, 13A, 138, and 13C. As illustrated schematically in Figures 12A and 12B, the charged member illustrated schematically in Figures 9A and 9B is first exposed uniformly to activating radiation 32 at a wavelength to which the migration marking materials 28 and 38 are sensitive. For example, when both the first and second migration marking materials are selenium particles, blue or green light can be used for uniform exposure. As shown in Figure 12A, when layers 26 and 34 are situated above layer 23, the uniform exposure to radiation 32 results in absorption of radiation by the migration marking materials 28 and 38. The migration marking particles 28 and 38 acquire a negative charge as ejected holes (positive charges) discharge the surface negative charges. As shown in Figure 12B, when layer 23 is situated above layers 26 and 34, uniform exposure to activating radiation 32 at a wavelength to which the migration marking materials are sensitive results in substantial photodischarge as the photogenerated charges (holes in this instance) in the migration marking particles are ejected out of the particles and transported to the substrate. As a result, the migration marking particles acquire a negative charge as shown schematically in Figure 12B. As illustrated schematically in Figures 13A, 13B, and 13C, the charged member is subsequently exposed imagewise to infrared or red light radiation 31. As shown in Figure 13A, when the softenable layers 26 and 34 are situated between the infrared or red light sensitive layer 23 and the radiation source 31, the infrared or red light radiation 31 passes through the non-absorbing migration marking materials 28 and 34 (which are selected to be insensitive to the infrared or red light radiation wavelength used in this step) and exposes the infrared or red light sensitive pigment particles 24 in the infrared or red light sensitive layer, thereby discharging the migration marking particles 28b and 38b in area 37 that are exposed to infrared or red light radiation and leaving the migration marking particles 28a and 38a charged in areas 35 not exposed to infrared or red light radiation. As shown in Figure 13B, when layer 23 is situated above layers 26 and 34, and the charged member is subsequently imagewise exposed to infrared or red light radiation 31, absorption of the infrared or red light by layer 23 in the exposed areas results in photogeneration of electrons and holes which neutralize the positive surface charge and the negative charge in the migration marking particles. In the embodiment illustrated in Figure 138, the resulting charge pattern is such that the imaging member cannot be developed by heat development, since there is no substantial electric field between the migration marking materials and the substrate. The imaging member with a charge pattern as illustrated in Figure 13B can be developed by a development process, such as solvent vapor exposure followed by heating, in which the non-charged particles agglomerate and coalesce into a few large particles, resulting in a D min region, and the non-charged particles, which repel each other because they bear like charges, are not agglomerated or coalesced and remain substantially in their original positions, resulting in a D max region. However, heat development generally is preferred to vapor or solvent development for reasons of safety, speed, cost, simplicity, and easy implementation in a machine environment. As shown schematically in Figure 13C, the imaging member is further subjected to uniform recharging to a polarity opposite to that which the charge transport materials in the softenable layers are capable of transporting (negative as illustrated in Figure 13C), resulting in the migration marking materials in areas of the imaging member which have not been exposed to infrared or red light radiation becoming negatively charged, with an electric field between the migration marking particles and the substrate, and areas of the imaging member previously exposed to infrared or red light radiation becoming charged only on the surface of the member. The charge image pattern obtained after the processes illustrated schematically in Figures 12A and 12B and Figures 13A, 13B, and 13C is thus identical to the one obtained after the processes illustrated schematically in Figures 10A and 10B and Figures 11A, 11B, and 11C. As illustrated schematically in Figures 14A and 148, subsequent to formation of a charge image pattern, the imaging member is developed by causing the softenable materials to soften by any suitable means (in Figures 14A and 14B, by uniform application of heat energy 33 to the member). The heat development temperature and time depend upon factors such as how the heat energy is applied (e.g. conduction, radiation or convection), the melt viscosity of the softenable layers, thickness of the softenable layers, and the amount of heat energy. For example, at a temperature of 110°C to 130°C, heat need only be applied for a few seconds. For lower temperatures, more heating time can be required. When the heat is applied, the softenable materials 27 and 36 decrease in viscosity, thereby decreasing their resistance to migration of the marking materials 28 and 38 through the softenable layers 26 and 34. As shown in Figure 14A, when layers 26 and 34 are situated above layer 23, in areas 35 of the imaging member, wherein the migration marking materials 28a and 38a have a substantial net charge, upon softening of the softenable materials 27 and 36, the net charge causes the charged marking material to migrate in image configuration towards the conductive layer 22 and disperse or agglomerate in the first softenable layer 26, resulting in a D min area. The uncharged migration marking particles 28b and 38b in areas 37 of the imaging member remain essentially neutral and uncharged. Thus, in the absence of migration force, the unexposed migration marking particles remain substantially in their original position in softenable layers 26 and 34, resulting in a D max area. As shown in Figure 14B, in the embodiment wherein layer 23 is situated above layers 26 and 34 and the member was charged in step 98 to the same polarity as that which the charge transport materials in the softenable layers are capable of transporting and in which the member has been recharged as shown in Figure 11C or 13C to the polarity opposite to that which the charge transport materials in the softenable layers are capable of transporting, the migration marking particles that are charged (those not exposed to infrared or red light radiation) migrate in depth toward the substrate 22 and disperse or agglomerate in first softenable layer 26, resulting in a D min area. The uncharged migration marking particles 28b and 38b in areas 37 of the imaging member remain essentially neutral and uncharged. Thus, in the absence of migration force, the unexposed migration marking particles remain substantially in their original positions in softenable layers 26 and 34, resulting in a D max area. If desired, solvent vapor development can be substituted for heat development. Vapor development of migration imaging members is well known in the art. Generally, if solvent vapor softening is utilized, the solvent vapor exposure time depends upon factors such as the solubility of the softenable layers in the solvent, the type of solvent vapor, the ambient temperature, and the concentration of the solvent vapors. The application of either heat, or solvent vapors, or combinations thereof, or any other suitable means should be sufficient to decrease the resistance of the softenable materials 27 and 36 of softenable layers 26 and 34 to allow migration of the migration marking materials 28 and 38 through softenable layers 26 and 34 in imagewise configuration. With heat development, satisfactory results can be achieved by heating the imaging member to a temperature of 100°C to 130°C for only a few seconds when the unovercoated softenable layers contain an 80/20 mole percent copolymer of styrene and hexylmethacrylate having an intrinsic viscosity of 0.179 dl/gm and N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine. The test for a satisfactory combination of time and temperature is to maximize optical contrast density. With vapor development, satisfactory results can be achieved by exposing the imaging member to the vapor of toluene for between 4 seconds and 60 seconds at a solvent vapor partial pressure of between 6.67·10 2 to 4.0·10 3 Pa (5 millimeters and 30 millimeters of mercury) when the unovercoated softenable layers contain an 80/20 mole percent copolymer of styrene and hexylmethacrylate having an intrinsic viscosity of 0.179 dl/gm and N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine. The imaging members illustrated in Figures 9A and 98 through 14A and 14B are shown without any optional layers such as those illustrated in Figures 2 and 3. If desired, alternative imaging member embodiments, such as those employing any or all of the optional layers illustrated in Figures 2 and 3, can also be employed. Specific embodiments of the invention will now be described in detail. These examples are intended to be illustrative, and the invention is not limited to the materials, conditions, or process parameters set forth in these embodiments. All parts and percentages are by weight unless otherwise indicated. EXAMPLE I A Three migration imaging members each having a single softenable layer were prepared as follows. A solution for the softenable layer was prepared by dissolving about 84 parts by weight of a terpolymer of styrene/ethylacrylate/acrylic acid (prepared as disclosed in US-A-4,853,307) and about 16 parts by weight of N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (prepared as disclosed in US-A-4,265,990) in about 450 parts by weight of toluene. N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine is a charge transport material capable of transporting positive charges (holes). The resulting solution was coated by a solvent extrusion technique onto three 75 µm (micron) thick polyester substrates (Melinex 442, obtained from Imperial Chemical Industries (ICI), aluminized to 20 percent light transmission), and the deposited softenable layers were allowed to dry at about 115°C for about 2 minutes, resulting in dried softenable layers with thicknesses of about 4 µm (microns). The temperature of the softenable layers was then raised to about 115°C to lower the viscosity of the exposed surfaces of the softenable layers to about 5·10 2 Pa.s (5 x 10 3 poises) in preparation for the deposition of marking material. Thin layers of particulate vitreous selenium were then applied by vacuum deposition in a vacuum chamber maintained at a vacuum of about 5.33·10 -2 Pa (4 × 10 -4 Torr). The imaging members were then rapidly chilled to room temperature. Reddish monolayers of selenium particles having an average diameter of about 0.3 µm (micron) embedded 0.05 to 0.1 µm (micron) below the surfaces of the copolymer layers were formed. B Two additional migration imaging members were prepared as described above in Paragraph A. These imaging members were wound onto 25 mm diameter cardboard tube laminating cores. The two rolls of imaging member sheets were mounted on the support brackets in a GBC 5270 laminator, obtained from GBC Canada, Don Mills, Ontario, Canada. The normal operation of this laminator is to have two rolls of laminating material mounted on support brackets. The film is threaded and joined. An item, such as a poster or placemat, for instance, can be placed between the two sheets and run through pinch and drive rollers, resulting in placement of a protective overcoat on both sides of the item. In this instance, the rolls of imaging member were mounted on the support brackets which ordinarily bear the rolls of protective coating material. The imaging members were threaded and joined so that the softenable layer of the first member was in contact with the softenable layer of the second member. Sections of the "sandwich" thus formed were then fed through the laminator at temperatures of 104.4°C, 121.1°C, 135.0°C and 148.9°C. After the "sandwich" had passed through the laminator and was cut from the machine, it was left to cool for a few minutes, after which the two layers were carefully peeled apart, resulting in formation of a single migration imaging member having two softenable layers on the aluminized Mylar® substrate. C Optical densities of the imaging members formed in Paragraphs A and B above were as follows. All optical density measurements were done using a MacBeth TR927 densitometer. The background values attributable to the substrate were not subtracted from the values shown in the table. The blue setting corresponds to a Wratten No. 47 filter, the blue setting corresponds to a Wratten No. 25 filter, and the ultraviolet setting corresponds to a Wratten No. 18A filter. Ranges of optical density values are provided in instances wherein the optical density varied across the structure. Imaging Member Blue Optical Density Red Optical Density Ultraviolet Optical Density IA 2.02 1.11 - 1.29 3.25 IB at 104.4°C 3.25 1.44 - 1.50 4.32 IB at 121.1°C 3.06 1.46 - 1.59 4.27 IB at 135.0°C 2.94 - 2.99 1.51 4.18 - 4.23 IB at 148.9°C 2.68 - 2.55 1.50 - 1.54 4.05 - 3.99 For comparison purposes, the optical density of the aluminized polyester substrate was measured at 0.49 (blue), 0.66 (red), and 0.43 (ultraviolet). As the data indicate, the optical density of the unimaged imaging member with a single softenable layer containing a single monolayer of migration marking material was significantly less than the optical densities of the unimaged members having two softenable layers and two monolayers of migration marking material and prepared at various temperatures. EXAMPLE II One migration imaging member containing a single softenable layer as prepared in Paragraph A of Example I and four imaging members prepared as described in Paragraph B of Example I (passed through the laminator at 121.1°C) were imaged as follows. The surfaces of the members were uniformly negatively charged to surface potentials as indicated in the table below with a corona charging device and were subsequently optically exposed by placing a test pattern mask comprising a silver halide image in contact with the imaging members and exposing the members to blue light of 490 nanometers through the mask for a period of 5 seconds (corresponding to 36.5 ergs per square centimeter). The imaging members were then developed by subjecting them to temperatures as indicated in the table below for about 5 seconds using a small aluminum heating block in contact with the polyester substrates. The temperature of the block was measured using a YSI probe attached to a temperature controller, and the temperatures shown in the table are the values measured by the probe, which would typically be about 5°C less than the actual surface temperature. The optical densities of the imaging members in the D max and D min areas were as follows. All optical density measurements were done using a MacBeth TR927 densitometer. The background values attributable to the substrate were not subtracted from the values shown in the table. The blue setting corresponds to a Wratten No. 47 filter, the blue setting corresponds to a Written No. 25 filter, and the ultraviolet setting corresponds to a Wratten No. 18A filter. Ranges of optical density values are provided in instances wherein the optical density varied across the structure. Imaging Member Charge (volts) Dev. Temp. (°C) Optical Density (blue) Optical Density (ultraviolet) D max D min ΔO.D. D max D min ΔO.D. IA -388 95 1.97 0.89 1.08 - - - - - - - - - IB at 121.1°C -675 90 3.05 - 3.11 1.24 - 1.38 1.67 - 1.87 5.02 3.04 1.98 IB at 121.1°C -650 92 3.09 - 3.11 1.20 - 1.24 1.85 - 1.91 4.99 2.89 2.10 IB at 121.1°C -647 95 3.03 - 3.08 1.11 - 1.13 1.90 - 1.97 5.03 2.82 2.21 IB at 121.1°C -674 98 3.01 - 3.06 1.13 1.88 - 1.93 4.84 2.82 2.02 - - - indicates not measured As the data indicate, the blue optical contrast density (ΔO.D.) of the imaged imaging member with a single softenable layer containing a single monolayer of migration marking material was significantly less than the blue optical contrast densities of the imaged members having two softenable layers and two monolayers of migration marking material. EXAMPLE III A Two infrared-sensitive migration imaging members were prepared as follows. A solution for the softenable layer was prepared by dissolving about 84 parts by weight of a terpolymer of styrene/ethylacrylate/acrylic acid (prepared as disclosed in US-A-4,853,307) and about 16 parts by weight of N,N'-diphenyl-N,N'-bis(3"-methylpheriyl)-(1,1'-biphenyl)-4,4'-diamine (prepared as disclosed in US-A-4,265,990) in about 450 parts by weight of toluene. N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine is a charge transport material capable of transporting positive charges (holes). The resulting solution was coated by a solvent extrusion technique onto two 75 µm (micron) thick polyester substrates (Melinex 442, obtained from Imperial Chemical Industries (ICI), aluminized to 20 percent light transmission), and the deposited softenable layers were allowed to dry at about 115°C for about 2 minutes, resulting in dried softenable layers with thicknesses of about 2 µm (microns). The temperature of the softenable layers was then raised to about 115°C to lower the viscosity of the exposed surfaces of the softenable layers to about 5·10 2 Pa.s (5 × 10 3 poises) in preparation for the deposition of marking material. Thin layers of particulate vitreous selenium were then applied by vacuum deposition in a vacuum chamber maintained at a vacuum of about 5.33·10 -2 Pa (4 × 10 -4 Torr). The imaging members were then rapidly chilled to room temperature. Reddish monolayer of selenium particles having an average diameter of about 0.3 µm (micron) embedded 0.05 to 0.1 µm (micron) below the surfaces of the copolymer layers were formed. The migration imaging members thus formed and having a single softenable layer were divided in half and wound onto 25 mm diameter cardboard tube laminating cores. The two rolls of imaging member sheets were mounted on the support brackets in a GBC 5270 laminator which ordinarily bear the rolls of protective coating material. The imaging members were threaded and joined so that the softenable layer of the first member was in contact with the softenable layer of the second member. The "sandwiches" thus formed were then fed through the laminator at a temperature of 121.1°C at a rate of 76.2 mm.s -1 with the cooling fan in the laminator on. After the "sandwiches" had passed through the laminator and were cut from the machine, they were left to cool for a few minutes, after which the two layers of each "sandwich" were carefully peeled apart, resulting in formation of a single migration imaging member having two softenable layers on the aluminized Mylar® substrate. The migration imaging members thus formed and having two softenable layers and two monolayers of selenium particles were then treated as follows. A pigment dispersion was prepared by ball milling for 24 hours a mixture comprising 10.6 parts by weight solids in a solvent (wherein the solvent comprised 40 percent by weight 2-propanol and 60 percent by weight deionized water), wherein the solids comprised 20 percent by weight X-metal-free phthalocyanine (prepared as described in US-A-3,357,989) and 80 percent by weight of a styrene-butyl methacrylate copolymer (ICI Neocryl A622). The resulting dispersion was hand coated onto the top softenable layers of the migration imaging members with a #5 Meyer rod, followed by drying the deposited infrared-sensitive layers at 50°C for 1 minute by contacting the polyester substrates to an aluminum heating block. B Three infrared-sensitive migration imaging members were prepared as described in Paragraph A above except that the substrate, also obtained from ICI, was 100 µm (microns) thick and aluminized to SO percent light transmission. C The infrared-sensitive migration imaging members prepared in Paragraphs A and B were imaged as follows. The surfaces of the members were uniformly positively charged to surface potentials as indicated in the table below with a corona charging device and were subsequently exposed by placing a test pattern mask comprising a silver halide image in contact with the imaging members and exposing the members to infrared light of 773 nanometers through the mask for a period of 20 seconds (corresponding to 260 ergs per square centimeter). The exposed members were subsequently uniformly exposed to 490 nanometer light for a period of 10 seconds (corresponding to 53 ergs per square centimeter) and thereafter uniformly negatively recharged to surface potentials as indicated in the table below with a corona charging device. The imaging members were then developed by subjecting them to temperatures as indicated in the table below for periods of time as indicated in the table below using a small aluminum heating block in contact with the polyester substrates. The temperature of the block was measured using a YSI probe attached to a temperature controller, and the temperatures shown in the table are the values measured by the probe, which would typically be about 5°C less than the actual surface temperature. The optical densities of the imaging members in the D max and D min areas were as follows. All optical density measurements were done using a MacBeth TR927 densitometer. The background values attributable to the substrate were not subtracted from the values shown in the table. The blue setting corresponds to a Wratten No. 47 filter, the blue setting corresponds to a Wratten No. 25 filter, and the ultraviolet setting corresponds to a Wratten No. 18A filter. Ranges of optical density values are provided in instances wherein the optical density varied across the structure. Imaging Member Positive Charge (volts) Negative Charge (volts) Development Temperature (°C) Development Time (seconds) IIIA(1) + 540 -475 98 5 IIIA(2) + 550 -485 98 2 IIIB(1) +300 -285 95 5 IIIB(2) +286 -232 98 5 IIIB(3) + 285 -270 98 2 Imaging Member Optical Density (blue) Optical Density (ultraviolet) D max D min ΔO.D. D max D min ΔO.D. IIIA(1) 2.43 1.13 1.30 4.47 - 4.96 3.12 - 3.14 1.33 - 1.84 IIIA(2) 2.81 1.36 1.45 5.00 - 5.19 3.39 1.61 - 1.80 IIIB(1) 2.97 1.33 - 1.65 1.32 - 1.64 4.60 - 4.80 2.60 - 2.70 1.90 - 2.20 IIIB(2) 1.85 - 2.93 1.01 - 2.07 0.84 - 0.86 4.65 - 4.90 2.55 2.10 - 2.35 IIIB(3) 2.75 1.05 1.70 - - - - - - - - - - - - indicates not measured The blue optical contrast densities (ΔO.D.) of the imaged imaging members having two softenable layers and two monolayers of migration marking material were, in most instances, higher than the blue optical contrast density of an infrared-sensitive member of similar composition but having only a single softenable layer and a single monolayer of migration marking material, which was 0.90. EXAMPLE IV Five infrared-sensitive migration imaging members were prepared as follows. Into 97 S parts by weight of cyclohexanone (analytical reagent grade, obtained from British Drug House (BOH)) was dissolved 1.75 part by weight of Butvar B-72. a polyvinylbutyral resin (obtained from Monsanto Plastics & Resins Co.). To the solution was added 0.75 part by weight of X-metal free phthalocyanine (prepared as described in US-A-3,357,989) and 100 parts by weight of 3.2 mm diameter stainless steel balls. The dispersion (containing 2.5 percent by weight solids) was ball milled for 24 hours and then hand coated with a #4 wire wound rod onto a 100 µm (microns) thick conductive substrate comprising aluminized polyester (Melinex 442, obtained from Imperial Chemical Industries (ICI). aluminized to 20 percent light transmission). After the material was dried on the substrate at about 80°C for about 20 seconds, the film thickness of the resulting pigment-containing layer was about 0.06 µm (micron). Thereafter a solution for the softenable layer was prepared by dissolving about 84 parts by weight of a terpolymer of styrene/ethylacrylate/acrylic acid (prepared as disclosed in US-A-4,853,30) and about 16 parts by weight of N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (prepared as disclosed in US-A-4,265.990) in about 450 parts by weight of toluene. N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine is a charge transport material capable of transporting positive charges (holes). The resulting solution was coated by a solvent extrusion technique onto the infrared-sensitive pigment containing layer of the imaging member, and the deposited softenable layer was allowed to dry at about 115°C for about 2 minutes, resulting in a dried softenable layer with a thickness of about 8 µm (microns). The temperature of the softenable layer was then raised to about 115°C to lower the viscosity of the exposed surface of the softenable layer to about 5·10 2 Pa.s (5 × 10 3 poises) in preparation for the deposition of marking material. A thin layer of particulate vitreous selenium was then applied by vacuum deposition in a vacuum chamber maintained at a vacuum of about 5.33·10 -2 Pa (4 × 10 -4 Torr). The imaging member was then rapidly chilled to room temperature. A reddish monolayer of selenium particles having an average diameter of about 0.3 µm (micron) embedded 0.05 to 0.1 µm (micron) below the surface of the copolymer layer was formed. Onto an additional 75 µm (microns) thick conductive substrate comprising aluminized polyester (Melinex 442, obtained from Imperial Chemical Industries (ICI), aluminized to 20 percent light transmission) was also coated the solution of the softenable layer composition containing 84 parts by weight of the terpolymer and 16 parts by weight of the charge transport material by the same process, and a thin layer of particulate vitreous selenium was vacuum deposited onto the softenable layer on the 75 µm (microns) thick substrate by the same process, resulting in formation of a softenable layer 4 µm (microns) thick. The two imaging members, one having both an infrared-sensitive layer and a softenable layer and one having only a softenable layer, were then wound onto 25 mm diameter cardboard tube laminating cores. The two rolls of imaging member sheets were mounted on the support brackets in a GBC 5270 laminator which ordinarily bear the rolls of protective coating material. The imaging members were threaded and joined so that the softenable layer of the first member was in contact with the softenable layer of the second member. The "sandwich" thus formed was then fed through the laminator at a temperature of 121.1°C at a race of 76.2 mm.s -1 with the cooling fan in the laminator on. After the "sandwich" had passed through the laminator and was cut in five pieces from the machine, the pieces were left to cool for a few minutes, after which the two layers of each "sandwich" were carefully peeled apart. resulting in formation of a single migration imaging member having two softenable layers on the infrared-sensitive layer on the aluminized Mylar® substrate. The infrared-sensitive migration imaging members thus prepared were then imaged as follows. The surfaces of the members were uniformly negatively charged to surface potentials as indicated in the table below with a corona charging device and were subsequently uniformly exposed to 490 nanometer light for the period of time indicated in the table below, followed by imagewise exposure to infrared light by placing a test pattern mask comprising a silver halide image in contact with the imaging members and exposing the members to infrared light of 773 nanometers through the mask for the period of time indicated in the table below. As indicated in the table below, some of the imaging members were subjected to a second negative charging step after the infrarecl imaging step and some were not. The imaging members were then developed by subjecting them to temperatures as indicated in the table below for 5 seconds using a small aluminum heating block in contact with the polyester substrates. The temperature of the block was measured using a YSI probe attached to a temperature controller, and the temperatures shown in the table are the values measured by the probe, which would typically be about 5°C less than the actual surface temperature. The optical densities of the imaging members in the D max and D min areas were as follows. All optical density measurements were done using a MacBeth TR927 densitometer. The background values attributable to the substrate were not subtracted from the values shown in the table. The blue setting corresponds to a Wratten No. 47 filter, the blue setting corresponds to a Wratten No. 25 filter, and the ultraviolet setting corresponds to a Wratten No. 18A filter Ranges of optical density values are provided in instances wherein the optical density varied across the structure. Imaging Member First Negative Charge (volts) Blue Exposure (seconds) IR Exposure (seconds) Second Negative Charge (volts) Development Temperature (°C) IV(1) -640 10 20 - - - 115 IV(2) -650 10 20 - - - 119 IV(3) -620 10 20 -840 119 IV(4) -650 5 20 -840 119 IV(5) -640 5 10 -750 119 - - - indicates not performed Imaging Member Optical Density (blue) Optical Density (ultraviolet) D max D min ΔO.D. D max D min ΔO.D. IV(1) 2.85 1.12 - 1.63 1.22 - 1.73 4.90 - 5.15 3.15 - 3.69 1.21 - 2.00 IV(2) 2.74 1.39 - 1.53 1.21 - 1.35 4.92 - 5.08 3.42 - 3.57 1.35 - 1.66 IV(3) 2.75 1.31 - 1.40 1.35 - 1.44 5.55 - 5.90 3.37 - 3.44 2.11 - 2.53 IV(4) 2.74 1.24 1.50 4.60 - 4.80 3.31 - 3.35 1.25 - 1.49 IV(5) 2.64 - 2.75 1.31 - 1.41 1.23 - 1.44 4.88 - 5.00 3.28 - 3.74 1.14 - 1.72 The blue optical contrast densities (ΔO.D.) of the imaged imaging members having two softenable layers and two monolayers of migration marking material were significantly higher than the blue optical contrast density of an infrared-sensitive member of similar composition but having only a single softenable layer and a single monolayer of migration marking material, which was 0.90.

Claims: A process for preparing a migration imaging member, comprising: applying a first softenable layer (146) to a first substrate (144) and a second softenable layer (156) to a second substrate (154); softening (170,172) the first and second softenable layers and; contacting the first softenable layer and the second softenable layer in a deposition zone in a vacuum chamber with vapors (160) comprising a migration marking material so that the migration marking material is simultaneously deposited (162,164) on the first softenable layer and the second softenable layer. The process of claim 1, including moving the first substrate (144) and the second substrate (154) through the process in the form of continuous advancing sheets. The process of claim 1 or claim 2, including laminating (174,176) the first softenable layer and the second softenable layer to one another after said contacting step. The process of claim 3, including removing (179) the second substrate (154) from the second softenable layer (156) after said laminating step. The process of claim 3, including, after said laminating step: removing (180) the first substrate (144) from the first softenable layer (146); attaching (182,184) a third substrate (149) to the first softenable layer (146); and removing (188) the second substrate (154) from the second softenable layer (156). The process of any one of claims 1 to 5, wherein said softening step comprises heating the first substrate and the second substrate with heated rollers (170,172). An apparatus for preparing a migration imaging member comprising: a vacuum chamber (108); means (190,192) for moving a first and a second substrate (144,154) through said vacuum chamber; means (160) for vapor depositing a material (162,164) simultaneously on the first substrate and the second substrate. The apparatus of claim 7, including means for applying a first softenable layer (146) to the first substrate (144) and a second softenable layer (156) to the second substrate (154), prior to the vapor deposition of said material, whereby said material (162,164) is deposited on the softenable layers. The apparatus of claim 8, including means (170,172) for softening the softenable layers prior to the vapor deposition of said material. The apparatus of claim 8 or claim 9, including means (174,176) for laminating the first softenable layer and the second softenable layer to one another in the vacuum chamber.

Inventors: LEVY ENRIQUE, PUNDSACK ARNOLD L, SONNENBERG HARDY, TAM MAN C, LEVY, ENRIQUE, PUNDSACK, ARNOLD L., SONNENBERG, HARDY, TAM, MAN C.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1995
Main classification: G03G17
IPC codes: G03G17