US 3840397 A
Description (OCR text may contain errors)
United States Patent [191 Amidon et al.
[451 7 Oct. 8, 1974 1 PARTICLE PLACING SYSTEM [751 Inventors: Alan B. Amidon, Penfield; William L. Goffe, Webster, both of NY.
 Assignee: Xerox Corporation, Rochester, NY.
 Filed: July 13, 1972 [211 App]. No.: 271,439
Related US. Application Data  Continuation of Ser. No. 685,536, Nov. 24, 1967,
 US. Cl 117/201, ll7/l7.5, 96/1 R, 96/1 E  Int. Cl G03g 13/00  Field of Search 117/16, 17, 9, 17.5, 201; 96/1 R, 1, E
 References Cited UNITED STATES PATENTS 4/1933 Cutler 118/106 Middleton; 96/1 2,924,519 2/1960 Bertelsen 96/1.4 3,054,716 9/1962 Bergstein 117/64 3,264,132 8/1966 Merill 117/31 3,266,932 8/1966 Anolick 117/62 3,318,697 2/1967 3,520,681 7/1970 Goffe 96/1 Primary ExaminerRalph S. Kendall Assistant Examiner-Michael F. Esposito 57 ABSTRACT A particle placing system wherein particulate material is placed in or on a softenable layer by pressing a donor uniformly coated with particulate material, a1- ternatively, at least partially in softenable material against a free surface of a softenable layer or a substrate of a migration imaging member.
6 Claims, 6 Drawing Figures PATENTED 0m 8 I974 3. 840.397
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[ HI I FIG. 1C FIG. 10
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PARTICLE PLACING SYSTEM This is a continuation of copending application Ser. No. 685,536, filed Nov. 24, 1967 now abandoned.
BACKGROUND OF THE INVENTION This invention relates in general to imaging, and more specifically to a new process of making a particle migration imaging member.
There has recently been developed a migration imaging system capable of producing high quality images of high density, continuous tone, and high resolution, an embodiment of which is described in copending application Ser. No. 460,377, filed June 1, 1965 now US. Pat. No. 3,520,681. Generally, according to an embodiment thereof, an imaging member comprising a conducting substrate with a layer of softenable (herein also intended to include soluble) material, containing photosensitive particles overlying the conductive substrate is imaged in the following manner: a latent image is formed on the member, for example, by uniformly electrostatically charging and exposing it to a pattern of activating electromagnetic radiation. The imaging member is then developed by exposing it to a solvent which dissolves only the softenable layer. Thephotosensitive particles which have been exposed to radiation migrate through the softenable layer as it is softened and dissolved, leaving an image of migrated particles corresponding to the radiation pattern of an original, on the conductive substrate. The image may then be fixed to the substrate. Those portions of the photosensitive material which do not migrate to the conductive substrate may be washed away by the solvent with the softenable layer. As disclosed therein, by other developing techniques, the softenable layer may at least partially remain behind on the substrate.
For some preferred photosensitiveparticles, for example those comprising amorphous selenium, the image produced by the above process is a negative of a positive original, i.e., the photosensitive particles migrate in the imagewise illuminated areas.
However, by certain process step sequences and member configurations, positive to positive imaging may be accomplished, i.e., the photosensitive particles.
migrate in the imagewise unexposed areas. For example, see copending applications Ser. Nos. 634,757 and 642,828, filed, Apr. 28, 1967 and June 1, 1967, respectively.
In general, three basic imaging members may be used: a layered configuration which comprises a substrate coated with a layer of softenable material, and a fracturable and preferably particulate layer of photosensitive material at or embedded nearthe upper surface of the softenable layer; a binder structure in which the photosensitive particles are dispersed in the softenable layer which overcoats a substrate; and an overcoated structure in which a substrate is overcoated with a layer of softenable material followed by an overlayer of photosensitive particles and a second overcoating of softenable material which sandwiches the photosensitive particles. Fracturable layer or material as used herein, is intended to mean any layer or material which is capable of breaking up into discrete particles of the size of an image element or less during development and permitting portions to migrate towards the substrate in image configuration.
This imaging system generally comprises a combination of process steps which includes forming a latent image and developing with a solvent liquid or vapor, or
.heat or combinations thereof to render the latent image visible. In certain methods of forming the latent image, non-photosensitive or inert, fracturable and particulate layers and material may be used to form images as described in copending application Ser. No. 483,675, filed Aug. 30, 1965, wherein a latent image is formed by a wide variety of methods including charging in image configuration through the use of a mask or stencil or first forming such a charge pattern on a separate photoconductive insulating layer according to conventional xerographic reproduction techniques and then transferring this charge pattern to the members hereof by bringing the two layers into very close proximity and utilizing breakdown techniques as described, for example, in Carlson US. Pat. No. 2,982,647 and Walkup US. Pat. No. 2,825,814 and 2,937,943; In addition, charge patterns conforming to selected, shaped, electrodes or combinations of electrodes may be formed by the TESI discharge techniques as more fully described in Schwertz US. Pat. No. 3,023,731 and 2,919,967 or by techniques described in Walkup US. Pat. No. 3,001,848 and 3,001,849, as well as by electron beam recording techniques, for example, as described in Glenn U.S'. Pat.'No. 3,113,179.
In another variation 'of this imaging system an image is formed by the selective disruption of a particulate material overlying'or in an electrostatically'deformable, or wrinkable film or layer. This variation differs from the system described above in that the softenable layer is deformed in conjunction with a disruption of the particulate material as described more-fully in copending application Ser. No. 520,423, filed Jan. 13, 1966, now abandoned.
The characteristics. of the images produced by this new system are dependent on such process steps as charging, exposure, and development, as well as the particular combination of process steps. High density, continuous tone and high resolution are some of the image characteristics possible. The image is generally characterized as a fixed or unfixed particulate image with or without a portion of the softenable layer and unmigrated portions of the fracturable layer left on the imaged member, which can be used in a number of applications such as microfilm, hard copy, optical masks, and stripout applications using adhesive materials.
When using the layered imaging member, i.e., where basically the member comprises a substrate, a softenable layer and an overcoating of a particulate material near the free surface of the softenable layer, it is preferable in order to form uniform images that the particulate material be uniformly deposited over the entire imageable surface of the member. It is also preferred to have the particulate material adhere sufficiently to or be sufficiently embedded inthe soluble or softenable layer so that the imaging member may be conveniently handled and stored prior to processing.
As disclosed in aforementioned copending application Ser. No. 460,377, now US. Pat. No. 3,520,681, two methods of depositing the particulate material which reasonably satisfy the requirements of uniformity and stability of the particulate layer are vacuum deposition techniques and cascade techniques where the particulate material is mixed with larger carrier beads for example of the type used in xerography and poured or cascaded over the free surface of the soluble or softenable layer.
Each of these techniques has certain limitations. For example, vacuum evaporation works only for some types of particulate material, requires a vacuum and requires careful control of substrate temperature and rate of evaporation to obtain optimum results. The cascade technique may produce static electricity effects due to interaction of the carrier beads with the particulate material, and in many applications requires more than one cascade to deposite particulate material to sufficient thickness, may be humidity sensitive, may be slow and cumbersome and is sometimes difficult to control.
Also, im making binder type imaging members typically comprising a layer of softenable material containing dispersed particles, on a substrate, it is found that normally advantageous modes of forming the particle containing softenable layer, which employ coating of a dispersion comprising particles and softenable material in a liquid solvent vehicle may attack or degrade certain substrates especially where such substrate materials are soluble in the solvent used in the coating dispersion.
Thus, there is a continuing need for a better system for concentrating a greater amount of particulate material near the free surface of the softenable layer and for fabricating binder type migration imaging members.
SUMMARY OF THE INVENTION satisfies the above noted wants.
It is a further object of this invention to provide a system of placing particulate material in or on a softenable layer which does not require a vacuum.
It is a further object of this invention to provide a system of placing particulate material in or on a softenable layer which produces no static electricity effects.
It is a still further object of this invention to provide a system of placing particulate material in or on a softenable layer which produces better uniformity and thickness control of the particulate material.
It is a still further object of this invention to provide a system of placing particulate material in or on a softenable layer which produces a very dense concentration of particulate material contiguous the surface of said layer.
It is a still further object of this invention to produce stable imaging members which may be handled and stored.
It is a still further object of this invention to provide a system for placing particulate material in or on a softenable layer which lends itself to mass production techniques.
It is a still further object of this invention to provide a system of fabricating a binder migration imaging member which does not necessitate coating a dispersion directly on said membe'rs substrate.
The foregoing objects and others are accomplished in accordance with this invention by providing a system of placing particulate material in or on a softenable layer by pressing a donor uniformly coated with particulate material alternatively, at least partially in softenable material against the free surface of a softenable layer or a substrate of a migration imaging member.
BRIEF DESCRIPTION OF THE DRAWINGS according to this invention.
FIG. 2 is a partially schematic illustration of an embodiment of apparatus for continuously accomplishing the placing of particles according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1A, there is shown layered type migration imaging member 10 according to this invention comprising substrate 11, electrically insulating softenable layer 12 which contains contiguous its upper surface a fracturable layer of particulate photosensitive material l3.-
Substrate 11 may be electrically conductive or insulating; Conductive substrates generally facilitate the chargingor sensitizationof the member according to the inventionand typically maybe of copper, brass, nickel, zinc,'chromium, stainless steel, conductive plastics and rubbers, aluminum, steel, cadmium, silver and gold. The substrate maybe in any suitable form such as a metallic strip, sheet, plate, coil, cylinder, drum, endless belt, moebius strip or the like. If desired, the conductive substrate may be coated on an insulator such as paper, glass or plastic. Examples of this type of substrate are a substantially transparent tin oxide coated glass available under the trademark NESA from the Pittsburgh Plate Glass Co., aluminized polyester film, the polyester film available under the trademark Mylar from DuPont, or Mylar coated with copper iodide.
Electrically insulating substrates may also be used which opens up a wide variety of film formable materi als such as plastics for use as substrate 11.
Softenable layer 12 may be any suitable material which is soluble or softenable in a solvent liquid or vapor or heat or combinations thereof and in addition is substantially electrically insulating during the latent image forming and developing steps hereof. Typical materials include Staybelite Ester 10, a partially hydrogenated rosin ester, Foral Ester, a hydrogenated rosin triester, and Neolyne 23, an alkyd resin, all from Hercules Powder Co.; SR type silicone resins available from General Electric Corporation; Sucrose Benzoate, Eastman Chemical; Velsicol X-37, a polystyreneolefin copolymer from Velsicol Chemical Corp.; Hydrogenated Piccopale 100, a highly branched polyolefin, Piccotex 100, polystyrene-vinyl toluene copolymer, Piccolastic A--75,' and 125, all polystyrenes, Piccodiene 2215, a polystyreneolefin copolymer, all from Pennsylvania Industrial Chemical Corp.; Araldite 6060 and 6071, epoxy resins from Ciba; R506lA, a phenylmethyl silicone resin, from Dow Corning; Epon 1001, a bisphenol A-epichlohydrin epoxy resin, from Shell Chemical Corp.; and PS-Z, PS-3, both polystyrenes, and ET693, a phenol-formaldehyde resin, from Dow Chemical; a customsynthesized copolymer of styrene and hexylmethacrylate, a custom synthesized polydi- The above group of materials is not intended to be limiting, but merely illustrative of materials suitable for softenable layer 12. The softenable layer may be of any suitable thickness, with thicker layers generally requiring a greater charge potential for imaging. In general, thicknesses from about V2 to about 16 microns have been found to be preferred with a thickness from about 1 to about 4 microns being found to be optimum. Layer 12 may also be of multilayer construction, with layers of different softenable materials.
' The material comprising particles 13, portions of which migrate to the substrate during image formation, may comprise any suitable photosensitive fracturable material. While it is preferred for images of highest resolution and density that the fracturable material be particulate, and preferably with an average particle size from about 0.01 to about 2.0 microns, it may comprise any continuous or semi-continuous, such as a swiss cheese pattern, fracturable layer which is capable of breaking upduring the development step and permitting portions to migrate to the substrate in image configuration.
Photosensitive materials comprising amorphous selenium, for example, amorphous selenium or amorphous selenium alloyed with arsenic, tellurium, antimony, bismuth, etc., or amorphous selenium or an alloy thereof doped with a halogen and those comprising phthalocyanine particles, for example, as listed in copending application Ser. No. 375,191, filed June 15, 1964 and including the new X-form metal-free phthalocyanine produced as described in Byrne, et al, U.S. Pat. No. 3,357,989 are preferred photosensitive materials because of their ability to form uniform particle layers according to this invention and their ability to be optically imaged to form high quality migration images.
However, any suitable photosensitive fracturable material may be used herein. Typical such materials include inorganic or organic photoconductive insulating materials.
Typical inorganic photoconductors include amorphous selenium; amorphous selenium alloyed with arsenic, tellurium, antimony or bismuth, etc.; amorphous selenium or its alloys doped with halogens; cadmium sulfide, zinc oxide, cadmium sulfoselenide, cadmium yellows such as Lemon Cadmium yellow X2273 from Imperial Color and Chemical Dept. of Hercules Powder Co., and many others. Middleton et al, U.S. Pat. No. 3,121,006 lists typical inorganic photoconductive piigments. Typical organic photoconductors include azo dyes such as Watchung Red B, a barium salt of 1- (4-methyl-5'-chloro-azobenzene-2-sulfonic acid)-2- hydrohydroxy-3-napthoic acid, C. I. No. 15865, and Monastral Red B, both available from DuPont; Indofast double scarlet toner, a Pyranthrone-type pigment available from Harmon Colors; quindo magenta RV6803, a quinacridone-type pigment available from Harmon Colors; Cyan Blue, GTNF, the beta form of copper phthalocyanine, C. I. No. 74160, available from Collway Colors; Monolite Fast Blue GS, the alpha form of metal-free phthalocyanine, C. I. No. 74100, available from Arnold Hoffman Co.; commercial indigo available from National Aniline Division of Allied Chemical Corp.; yellow pigments prepared as disclosed in Weinberger U.S. Pat. No. 3,447,922 or as disclosed in Weinberger U.S. Pat. No. 3,402,177, X-form metal-free phthalocyanine prepared as disclosed in Byrne, et al, U.S. Pat. No- 3,357,989, quinacridonequinone from DuPont, sensitized polyvinyl carbazole Diane Blue, 3,- 3'-methoxy-4,4-dipheny l-bis (1" azo-2" hydroxy-3"- naphthanilide), C. I. No. 21180, available from Harmon Colors; and Algol G. C. l,2,5,6-di (D,D'- diphenyl)-thiazole-anthraquinone, C. 1. No. 67300, available from General Dyestuffs and mixtures thereof. The above list of organic and inorganic photoconduc-v tive photosensitive materials is illustrative of typical materials, and should not be taken as a complete listing of photosensitive materials.
The thickness of the fracturable layer in the layered type configuration of FIG. 1A is generally preferably from about 0.01 to about 2.0 microns although 5 micron layers have been found to give good results for some materials. A more detailed description of the layered configuration imaging member may be found in copending application Ser. No. 635,256, filed May 1, 1967 In addition to the configuration shown in FIG. 1A additional modifications in the basic structure such as the use of the binder form in which the structure consists of photosensitive fracturable material dispersed in the softenable layer may also be used. In addition, an overcoated structure in which the photosensitive fracturable material is sandwiched between two layers of the softenable material which overlying a substrate is also included within the scope of this invention.
The. member 10 is processed to form an image, generally by forming a latent image on or in layer 13 followed by development of the latent image. Forming the latent image and development are typically carried out in the substantial absence of ambient actinic radiation for the imaging member. As described in aforementioned copending application 460,377 new U.S. Pat. No. 3,520,681, and others referenced herein, the latent image may be formed by uniformly electrostatically charging layer 13, for example, to a surface potential of from about 1- 60-200 volts, exposing said layer to an optical image and developing by dissolving away layer 12 with a solvent.
However, any suitable method of forming a'latent image on members hereof and then developing may be used. Other methods of forming a latent image on member 10 are known in the art and include corona charging through a stencil as shown in aforementioned application Ser. No. 483,675, or forming a latent image by the other means described therein where the fracturable material need not be photosensitive. Another mode of optically forming a latent image is to use a member comrising a photoconductive soluble layer and fracturable material which need not be photosensitive as more fully described in copending application Ser. No. 553,837, filed May 31, 1966, now abandoned.
Also any suitable method to cause migration of particles to develop the imaging members hereof may be used including softening the softenable layer, for example, with solvent vapor and/or heat to cause migration as more particularly described in aforementioned copending applications 460,377 now US. Pat. No. 3,520,681 and 483,675, and in copending application Ser. No. 612,122, filed Jan, 27, 1967. Although layer 12 and nonmigrated areas of fracturable material, are not washed away in vapor and heat development, the image produced may be viewed by means of special display techniques including, for example, focusing light reflected from the member onto a viewing screen. Moreover, a liquid solvent including electrically conductive liquids may at any time thereafter be applied to such an image to convert it into a solvent wash-away image. It should be understood that the inventive process hereof may be used to form any layered configuration, binder or overcoated structure used for any purpose so long as the product is formed according to the description herein.
Referring now to FIG. 2, there is illustrated a donor layer 14 in the form of a continuous web advancing from supply roll 15 consecutively past donor loading station 16 and transfer station 18 to be wound onto takeup roll 20 powered by motor 22.
At the transfer station 18 a suitable softenable layer 12 on a suitable substrate 11 as described in relation to FIG. 1A advances from supply roll 28to join with the particle loaded donor and the two members are advanced together between pressure rolls 30 and 36. The two members are stripped apart as layers 11 and 12 are advanced around guide and tension roller 31. Layers 11 and 12, layer 12 having picked up particles from the donor, are then advanced past fuser 33 to takeup roll 32 powered by motor 34.
Donor 14 may be any suitable web material, such as a metal or a plastic, coatable with particulate material, alternatively, in softenable material, which by pressure contact with a softenable layer or a substrate transfers a substantial portion of said carried particulate material to said softenable layer or substrate. Preferred donors for use herein, because of their ability to be uniformly coated with particulate material, their mechanical strength either alone or on asupporting substrate and their ability to transfer said material to layer 12 according to this invention, have been foundto be various film formable plastics, a partial listing of which is found in copending application Ser. No. 598,279, filed Dec. 1, 1966. Mylar film is found to be especially preferred for donor 14 because it is flexible, dimensionally stable, in soluble in many solvents and releases particulate material in a pressure transfer step.,
At donor loading station 16, donor 14 is coated by any suitable method to uniformly coat on the donor, particulate material tobe subsequently layered onto the surface of the softenable layer 12. Particulate material may conveniently be deposited onto the donor in a uniformly distributed releasably adhering layer by a wide variety of techniques including vacuum evaporation such as disclosed in copending application Ser. No. 423,167, filed Jan. 4, 1965, now abandoned, running the donor through a quantity of particulate material, powder cloud techniques, wiping the material on the donor, cascading or dusting material over the donor, for example, as described in copending application 460,377, now US. Pat. No. 3,520,681, applying it by various brushing techniques, examples of which are described in Vogt US. Pat. No. 3,375,806, or depositing a uniform layer of particles by the migration imaging process described in the aforementioned copending applications, for example by vacuum evaporating selenium on a softenable layer and charging, uniformly exposing and liquid solvent developing to form a layer of selenium particles on donor 14.
However, it is found to be preferred herein in order to provide the most uniform distribution of particulate material on the donor to disperse the particulate material in a liquid vehicle to form a slurry or dispersion which may be applied to the donor by any of the well known conventional painting or coating methods, including spray, drawdown, flow coating, knife coating, electrode coating, coating by uniformly charging the donor and causing charged particles in a tank to adhere to the web, for example as described in Mayer US. Pat. No. 2,877,133, Mayer bar drawdown, dip coating, reverse roll coating, spraying in an electric field and so on. This technique of dispersing the particulate material in a liquid vehicle and then coating on the donor, besides providing for a very uniform coating is also particularly well adapted to the coating process herein since many of the lilquid vehicles used in coating may be solvents for or otherwise might, tend to degrade softenable'layer 12, which thus prohibits the use of such dispersion or slurry coating techniques to directly coat layer 12. Also, such direct coating techniques would not fix or at least partially fix the particulate material to layer 12, which is a desired end result of this invention and is accomplished hereby 'due to the pressure transfer step.
For some particulate fracturable material especially photosensitive phthalocyanine particles, it is found that a small amount of softenable material on the phthalocyanine, as it resides on the donor prior to transfe r,'optimizes transfer of the particles from the donor to the softenable layer of members hereof. The softenable material to be coated with the particulate material may, in the preferred liquid vehicle dispersion coating method described above, conveniently be incorporated in the dispersion by employing a solvent for the incorporated softenable material as at least part of the dispersion liquid vehicle. Alternatively, a softenable layer may be formed on the donor and then loaded with particles which may be embedded in the softenable layer by pressure or softening the softenable layer. The amount of softenable material in the dried layer of particles on the donor prior to transfer to softenable layer 12, may just be thick enough, preferably from about 1 to about 5 microns, for preferred uniformly dense, transfer results; to cause embedding of particles in the softenable material or may be thick enough, up-to a maximum of about 2 microns, for preferred transfer results, to cover a monolayer of particles or to provide a matrix for dispersed particles. At transfer station 18, typically, substantially all of the'particle layer on the donor, alternatively with softenable material, is stripped therefrom and transferred to a softenable layer coated on a substrate or as will be described to a sub strate.
FIG. 1A is illustrative of an imaging member, formed by the invention, after softenable layer 12 has been contacted with a particle loaded donor; FIG; 1B is illustrative of an imaging member after softenable layer '12 has been contacted with a donor that carried layer 13 comprising a monolayer of particles just covered by softenable material which is shown after transfer to layer 12; FIG. 1C is illustrative of an imaging member after softenable layer 12 has been contacted with a donor that carried a layer of softenable material just thick enough to cause embedding of particles therein, shown after transfer to layer 12; FIG. ID is illustrative of an imaging member after softenable layer 12 has been contacted with a donor that carried layer 13 comprising a layer of softenable material containing dispersed particles, which is shown after transfer to layer 12; and FIG. IE is illustrative of an imaging member after substrate 11 has been contacted with a donor that carried layer 13 similar to layer 13 in FIG. 1D.
In the preferred particle-liquid dispersion, alternatively incorporating a softenable material, mode of loading the donor, the dry weight ratio of solids, i.e. particles, alternatively with softenable material/liquid vehicle for suitable particle placing results according to this invention is found to vary between about 1/80 to about l/l, with a preferred range being from about 1/40 to about l/l.
For dispersions containing relatively large amounts of liquid for example approaching the H80 figure, it is found that it becomes increasingly difficult to coat to form a uniform layer of particles on the donor upon drying, in that there is an increasing tendency for the deposition of particles to be blotchy with open areas with no particles. Also, with these larger amounts of liquid it becomes increasingly difficult to coat the dispersion, especially by simple 'draw coating techniques, to a sufficient thickness to produce a sufficiently dense layer of particles on the donor which is needed to produce by this invention a sufficiently dense particle layer on an imaging member preferred to give adequate density and contrast to the developed migration images produced on the members hereof.
For dispersions containing relatively small amounts of liquid, for example, in the area of the 1/ l figure, it is found that if the solids consist solely of particles, the particle layers deposited on the donor after drying have a tendency to crack by the time they are transferred according to this invention. Generally for these lower liquid content dispersions it has been found to be preferred to add softenable material to the particle-liquid mixture. Of course, in this alternative the liquid should be a solvent for the particular softenable material added.
A preferred weight ratio range of particles/softenable material is from about 6/1 to about l/12. The dispersions with a relatively large amount of particles typically produce imaging members of the type illustrated in FIGS. 1A, B and C while dispersions with relatively larger amounts of softenable material, i.e., ratios from about 3/1 or 2/ l to about I/ l 2 approach or assume the character of binder layers more particularly described in copending application Ser. No. 634,757, filed Apr. 28, 1967, and illustrated as layers 13 in FIGS. 1D and IE.
As illustrated in FIG. 1D, this binder type layer may be transferred from the donor on which it is formed to a softenable layer 12 on a substrate. Alternatively, the binder layer may be transferred by this invention from the donor on which it is formed directly to substrate 11 to form a binder imaging member as illustrated in FIG. 1E. This alternative mode of forming a binder layer may be distinctly preferred, for example, where the solvent used in a particular particlesoftenable materialliquid solvent dispersion would dissolve or otherwise degrade substrate 11 if directly coated thereon, but not a donor whereon the dispersion could be coated and the solvent evaporated to form a binder layer which may then be transferred, by this invention, to the substrate 11.
Besides incorporating softenable material in the particle dispersion coated on the donor, softenable material may be added to particles loaded on a donor by dip, draw, roll or otherwise coating a particle loaded donor with softenable material dissolved in a solvent, preferably in a dry weight ratio of softenable material/solvent of from about 1/80 to about l/l and optimumly from about N40 to about l/l'.
Also, in solvent liquid wash away development, described for example in copending application 460,377, now US. Pat. No. 3,520,681, the development time may be purposely shortened somewhat to leave a small amount of softenable material remaining behind with the migrated particles. The particles in the softenable material may then be transferred to a softenable layer on a substrate to fabricate the particle layer of a migra tion imaging member.
When loading and transferring only particles, any suitable thickness of particulate material may be coated on the donor at station 16, but to construct the layered configuration illustrated in FIG. 1A, preferred particulate material thicknesses on donor 14, for uniform, dense transfer of particles to a softenable layer range from about 0.5 to about 5.0 microns. FIG. 1B and 1C layer 13 preferred thicknesses range from about 0.01 to about 2.0 microns, while FIG. 1D and 1E preferred thicknesses range from about k to about 16 microns. After loading at station 16 the donor advances to transfer station 18. During this inverval, the liquid vehicle used in loading the particulate material on the donor may be evaporated to the desired degree to optimize the transfer of material at station 18. If the liquid vehicle used in loading is a solvent for layer 12, then it is found to be preferred to substantially evaporate off the liquid before the donor reaches the transfer station 18. It is found in certain applications of the invention that if a small amount of a vehicle, which is a solvent for layer 12, remains on the particulate material at transfer, this vehicle may soften and tackify layer 12 to actually enhance the acceptance of particuate material by said layer. Layer 12 may also be softened or otherwise treated in the region of travel between supply roll 28 and pressure roll 30 to render it more receptive to pickup of particles, alternatively with softenable material, from the donor.
If the interval between stations 16 and 18 is long enough, evaporation into the ambient atmosphere is sufficient, but for high speed operations evaporation may be accelerated by the use of conventional techniques such-as heating, forced air and combinations thereof.
At particulate material transfer station 18 the material loaded on the donor is transferred from the donor to softenable layer 12 which is moved intopreferably non'slipping pressure contact with the loaded donor 14. The two layers are pressed together between pressure rollers 30 and 36.
Any suitable pressure to effect uniform transfer of the particles from the donor to layer 12 may be used. For example, for the transfer apparatus embodiment illustrated, a force from about 10 to about pounds per linear inch of roller for about 2 inch diameter rollers with the layers 12' and 14 advancing at about 1 /2 inches/second was found to effect excellent transfer.
Of course, it will be appreciated that a flat donor may be pressed against a plate-like imaging member to effect the deposition of the particulate material onto and into the softenable layer in a piecework operation as contrasted to the continuous operation illustrated in FIG. 2. Pressures preferred for highest quality particle placing are found to fall in the range of from about 80 to about 1,100 psi.
In addition to pressure, it was generally found to be preferred to effect the pressure contact when the temperature of layer 12 was heated to a temperature between about 50C. and about 200C. and optimumly between about 50C. and about 150C. It is thought that the tackiness imparted to layer 12 at these temperatures enhances the transfer of particles. Employing a heated roller 30 heated to a temperature in the above stated ranges is found to be a preferred mode of heating layer 12 because of its convenience and because of the excellent resultant transfers of particulate material.
Softening layer 12 by exposure to solvents or vapors of a solvent for layer 12 is also found to be suitable.
Any suitable method of stripping apart layers 12 and 14 may be used. It was found to be preferred after pressure contact between layers 12 and 14 to cool layer 12 to around room temperature such as between about 10 and 30C. before the two layers are stripped away at roller 31. Such cooling enhances the ability of layer 12 to more completely receive particulate material from donor 14.
After stripping, layer 12 with particulate material contained fixed therein advances past fixing station 33 and on to takeup roll 32.
Fixing at station 33 is found to be optional but preferred in some embodiments hereof, to cause the particulate material to become more firmly adhered'to layer 12, to prevent offset to adjacent layers when rolled on takeup roll 32. Heat and vapor fixing and combinations thereof are found to be suitable.
Vapor fixing the vapors of strong solvents for layer 12 are found to cause migration and dispersing of particulate material in layer 12, after being deposited as a layer contiguous the free surface of layer 12, some par-.
ticles dispersing to distances up to about 2 microns from the free surface of layer 12 to form a binder type imaging member.
The following Examples further specifically define the present invention with respect to the particle placing system hereof. The parts and percentages are by weight unless otherwise indicated. The Examples below are intended to illustrate various preferred embodiments of this invention. 3
EXAMPLE I A dispersion of particulate material in a liquid vehicle is prepared by ball milling together in a 2 ounce jar on a paint shaker for about 5 hours, about one part of X-form metal-free phthalocyanine, for example prepared as disclosed in Byrne et al. U.S. Pat. No. 3,357,989; about parts of a long chain saturated ali-' phatic hydrocarbon liquid, boiling point 315350F. available under the designation Isopar G from the Humble Oil Co. and about 150 parts of stainless steel shot. After this mixing, about 30 additional parts of Isopar G are added followed by about 5 minutes of shaking. The resultant dispersion is coated onto an about 4 mil thick Mylar film using a Bird applicator and allowed to dry in the ambient air to form an about one 12 micron layer of X-form metal-free phthalocyanine uniformly deposited on the Mylar film.
A softenable layer is deposited on an aluminized Mylar film by coating with a Bird applicator about a 40% solution of Piccopale SE, a petroleum hydrocarbon resin available from Pennsylvania Industrial Chemical Corp., in xylene to form about a 2 micron thick, dried layer of the softenable material on the aluminized Mylar.
The loaded donor and the softenable layer are then pressure rolled together usingapparatus simmilar to that shown in FIG. 2 at a rate of advancement of the two layers of about 1% inches per second with a force on about 2 inch diameter pressure rollers of about 60 pounds per linear inch, with the temperature of the softenable layer at about C. After this pressure contact the two laminated layers are allowed to cool to about room temperature whereupon the two layers are separated to cause transfer of the particulate material from the donor to layer 12.
After separation v or stripping, coated layer 12 is treated with the vapor from trichloroethylene solvent available under the trademark FLO-SET from Xerox Corpqfor about 5 seconds "and then dried for about 5 minutes at about 50C. before being stored.
Dense images with resolutions greater than 25 line pairs/millimeter result, using the imaging member produced in this Example processed as described'in the aforementioned copending application Ser. No. 460,377.
EXAMPLE [I Example I is followed except that the donor is flexible brass sheet instead of Mylar film..
EXAMPLE III Example I is followed except that the softenable layer is formed by coating about a 20% solution of Amberol ST-137X, an unreactive phenol formaldehyde type resin available from Rohm and I-IaasCo., in xylene.
EXAMPLE IV Example I is followed except that the softenable layer is formed by coating about a 20% solution of Staybelite Ester 10 in xylene.
EXAMPLE V Example I is followed except that the'resultant particulate material comprises a trimix of about 50% X-form metal-free phthalocyanine, about 32% Watchung Red B and about 18% of a yellow pigment prepared as described in application Ser. No. 421,281, filed Dec. 28, 1964, now abandoned.
EXAMPLE VI A dispersion is made up of about three parts of X- form metal-free phthalocyanine, prepared as described in Byrne et al. U.S. Pat. No. 3,357,989 about nine parts of a polystyrene-vinyl toluene copolymer available under the designation Piccotex 100 from Pennsylvania Industrial Chemical Corp., and about 40 parts of xylene. The dispersion is ball milled on a paint shaker in a 4 ounce jar with about 20 parts of A; inch steel balls for about 2 hours and then sonically dispersed for about 5 minutes just prior to coating.
The dispersion is draw down bar coated onto Plestar polycarbonate film from Ansco Div. of General Aniline and Film Corp., and dried in air to give a thickness of about 2 microns.
A softenable layered substrate is then prepared by roll coating about a 2 micron layer of Staybelite Ester 10 on Mylar film having a thin transparent aluminum coating.
The Stabelite softenable layer is then surface softened by wiping it once with a cloth soaked with Freon 1 l3, and placed against the phthalocyanine coating on Plestar and the two members are passed through pressure roller subjected to a force of about 30 lbs/linear inch of roller, the rollers heated to about lC.
After cooling to about room temperature, the two members are peeled apart, to transfer the phthalocyanine binder layer to the Staybelite softenable layer.
The member is imaged by uniformly electrostatically charging it to a surface potential of about +100 volts, exposing the charged member to a positive (dark characters on a lighter background) optical image including line copy with exposure in illuminated areas of the member being about 2 f.c.s., the light source being a tungsten lamp with a color temperature of about 3,20OK.
The image is developed by immersing the member in cyclohexane liquid solvent for the Piccotex 100 and the Staybelite for about 3 seconds to produce a positive image of migrated phthalocyanine particles on the aluminized Mylar substrate corresponding to said optical image.
EXAMPLE Vll A dispersion coating solution is prepared by combining about grams of elemental selenium alloyed with arsenic (2% by weight of arsenic), about 5 grams of a custom synthesized copolymer of hexylmethacrylate and styrene, about 13 grams of toluene, and milling with flint balls in a size 000 ball mil jar for about 4 days.
After removing the milling balls, this solution is coated onto flexible sheet brass with a Gardner Draw Coater using a /2 mil Bird applicator.
A substrate of aluminized Mylar is then placed against the selenium in a binder coating on the brass, while the coating is still tacky, and the two members are passed through pressure rollers subjected to a force of about 30 lbs/linear inch. of roller, the rollers heate to about l00C.
After cooling to about room temperature, the two members are peeled apart, to transfer the selenium in a binder layer to the aluminized Mylar.
The member produced is imaged by uniformly electrostatically charging it to a surface potential of about +800 volts, exposing it to an optical image with exposure in illuminated areas being about 70 f.c.s., and developing by immersing the member in lightly agitated trichloroethylene liquid for a few seconds, to produce a positive image of a positive original. For example, if a positive transparency is used as the original, the photosensitive particles comprising selenium migrate in the imagewise unexposed areas to produce a deposition pattern of darker selenium, corresponding to the darker or colored areas of the positive transparency, on the relatively lighter aluminized Mylar substrate to produce a directly viewable image and one which may be 6 used as a projection transparency.
Although specific components and proportions have been stated in the above description of preferred embodiments of the particle placing method hereof, other suitable materials as listed herein may be used with similar results. In addition other materials may be added to the mixture or variations may be made in the various processing steps to synergize, enhance or otherwise modify the systems properties. For example, in the interval as donor 14 advances between rollers 30 and 31, external cooling means other than ambient air may be used to accelerate cooling. Also a release agent may be coated on donor 14 before being loaded to facilitate transfer of loaded material at transfer station 18. Also, softenable materials used herein may be modified by adding coloring agents such as dyes or by adding plasticizers or moisture and other proofing" agents, as known to those skilled in the art.
it will be understood that various other changes in the details, materials, steps and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure and such changes are intended to be included within the principle and scope of this invention.
What is claimed is: Y
1. A migration imaging process comprising:
1. providing an imaging member made by the steps a. loading onto a donor surface asubstantially uniform layer of particles, said layer consisting essentially of particles having average particle size in the range between about 0.01 and about 2.0 microns, with said layerof particles of thickness not greater than about 5.0 microns;
b. providing on a supporting substrate a receiver layer of substantially electrically insulating softenable material, of thickness in the range between about /2 and about 16 microns, said softenable material capable of having its resistance to migration of said particles decreased sufficiently to allow migration of said particles through said softenable material toward said substrate;
c. uniformly pressing the loaded donor surface in non-slipping contact against the surface of the softenable layer by advancing said loaded donor and said softenable layer at the same rate in the same direction between pressure rollers with pressures in the range between about and about 1,100 psi; and I d. separating said donor surface and said softenable layer, thereby transferring a uniform layer of particles to the softenable layer whereby a fracturable layer of particles is embedded at the surface of the layer of softenable material;
2. forming an electrical latent image on said imaging member formed by the process of step 1;
3. developing said latent image by decreasing the resistance of the softenable material to migration of the particles at least sufficient to allow imagewise migration in depth of the particles toward the substrate.
2. A method according to claim 1 wherein said softenable layer is a thermoplastic, and at least one of said pressure rollers is heated to between about 50C. and about 200C.
3. A method according to claim 2 wherein after said heat-pressure step the softenable layer is cooled to be- 16 tween about 10C. and about C. before the separat- 6. A method according to claim 5 wherein said phomg P- toconductor is selected from the group consisting of 4. A method according to claim 1 wherein said particles comprise an electrically photosensitive material. 5. A method according to claim 4 wherein said parti- 5 "mes, and mlxtures thereofcles comprise a photoconductor.
materials comprising amorphous selenium, 'phthalocya-