U.S. patent number 3,909,262 [Application Number 05/423,958] was granted by the patent office on 1975-09-30 for imaging migration member employing a gelatin overcoating.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to George A. Brown, William L. Goffe.
United States Patent |
3,909,262 |
Goffe , et al. |
September 30, 1975 |
Imaging migration member employing a gelatin overcoating
Abstract
A migration imaging system wherein migration imaging members
typically comprising a substrate, a layer of softenable material,
and migration marking material, additionally contain one or more
overlayers of material to produce improved results in the imaging
system. The overlayer may variously comprise another layer of
softenable material, a layer of material which is harder than the
softenable material layer, or a gelatin layer.
Inventors: |
Goffe; William L. (Webster,
NY), Brown; George A. (Penfield, NY) |
Assignee: |
Xerox Corporation (Stamford,
CT)
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Family
ID: |
26793728 |
Appl.
No.: |
05/423,958 |
Filed: |
December 12, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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97866 |
Dec 14, 1970 |
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172 |
Jan 2, 1970 |
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Current U.S.
Class: |
430/14; 430/18;
430/67; 430/41 |
Current CPC
Class: |
G03G
17/10 (20130101) |
Current International
Class: |
G03G
17/10 (20060101); G03G 17/00 (20060101); G03G
005/00 () |
Field of
Search: |
;96/1.5,1PS,1PE,1M |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Torchin; Norman G.
Assistant Examiner: Miller; John R.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional application of copending
application Ser. No. 97,866, now abandoned filed Dec. 14, 1970,
which is a continuation-in-part of application Ser. No. 172, filed
Jan. 2, 1970, now abandoned.
Claims
What is claimed is:
1. An imaged member comprising a substrate, a layer of electrically
insulating softenable material, a layer consisting of gelatin
overlying said layer of softenable material and agglomerable
migration marking material distributed in depth in said softenable
material in a first image configuration with said first image
configuration of agglomerable material agglomerated and/or fused
and comprising in addition to said first image configuration, an
unagglomerated complementary background pattern of agglomerable
migration marking material remaining substantially unagglomerated
contactng the gelatin layer - softenable layer interface.
2. The imaged member of claim 1 wherein said layer of gelatin is
substantially transparent.
3. The imaged member of claim 1 wherein said layer of gelatin is a
thickness in the range not greater than about 75 microns.
4. The imaged member of claim 1 wherein said layer of gelatin is a
thickness of from about 0.01 to about 1.0 microns.
5. The imaged member of claim 1 wherein said layer of gelatin is a
thickness of from about 0.1 to about 0.5 microns.
6. The imaged member of claim 1 wherein the layer of gelatin
comprises photographic grade gelatin with a molecular weight
ranging from about 20,000 to about 100,000.
7. The imaged member of claim 1 wherein said layer of gelatin is of
a hardness greater than the softenable material.
8. The imaged member of claim 1 wherein the agglomerable migration
marking material is electrically photosensitive material.
9. The imaged member of claim 8 wherein said electrically
photosensitive material is vitreous selenium.
10. The imaged member of claim 1 comprising a second overlayer of
material overlying said layer of gelatin, said second overlayer
being harder than said softenable layer and of such construction as
to permit charge transport therethrough.
11. The imaged member of claim 10 wherein the second overlayer of
material is substantially transparent.
Description
BACKGROUND OF THE INVENTION
This invention relates in general to imaging, and more specifically
to a migration imaging system employing overcoated migration
imaging members.
Recently, a migration imaging system capable of producing high
quality images of high density, continuous tone, and high
resolution has been developed. Such migration imaging systems are
disclosed in copending applications Ser. No. 837,780, filed June
30, 1969, and Ser. No. 837,591, filed June 30, 1969. In a typical
embodiment of the new migration imaging system an imaging member
comprising a substrate, a layer of softenable material and
photosensitive marking material is latently imaged 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 was originally in the form of a
fracturable layer contiguous the upper surface of the softenable
layer, the marking particles in the exposed areas of the member
migrate toward the substrate when the member is developed by
softening the softenable layer.
"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, melting,
and softening, by methods, 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.
"Fracturable" layer or material as used herein, means any layer or
material which is capable of breaking up during development,
thereby permitting portions of said layer to migrate toward the
substrate or to be otherwise removed. The fracturable layer may be
particulate, semi-continuous, or microscopically discontinuous in
various embodiments of the migration imaging members of the present
invention. Such fracturable layers of marking material are
typically contiguous the surface of the softenable layer spaced
apart from the substrate, and such fracturable layers may be near,
at, coated onto, or slightly, partially or substantially embedded
in the softenable layer in the various embodiments of the imaging
members of the inventive system. "Contiguous" for the purpose of
this invention is defined as in Webster's New Collegiate
Dictionary, Second Edition, 1960: "In actual contact; touching;
also, near, though not in contact; adjoining," and is intended to
generically describe the relationship of the fracturable layer of
marking material in the softenable layer, vis-a-vis the surface of
the softenable layer spaced apart from the 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 copending
applications which also disclose a variety of methods which may be
used to form latent images upon such migration imaging members.
Various means for developing the latent images in the novel
migration imaging system may be used. 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 said softenable
layer to allow imagewise migration of the particles toward the
substrate. In the solvent wash-away development method, the
migration marking material migrates in imagewise configuration
toward the substrate through the softenable layer and it is
softened and dissolved, leaving an image of migrated particles
corresponding to the desired image pattern on the substrate, with
the material of the softenable layer substantially completely
washed away. In the heat or vapor softening developing modes, the
softenable layer is softened to allow imagewise migration of
marking material toward the substrate and the developed image
member generally comprises the substrate having migrated marking
particles near the softenable layer-substrate interface, with the
softenable layer and unmigrated marking materials intact on the
substrate in substantially their original condition.
Various methods and materials and combinations thereof have
previously been used to fix unfixed migration images. For example,
fixing methods and materials previously used are disclosed in
copending applications Ser. No. 590,959, filed Oct. 31, 1966, now
abandoned and Ser. No. 695,214, filed Jan. 2, 1968 now
abandoned.
In addition to the aforementioned copending applications, another
copending application Ser. No. 71,781, filed Sept. 14, 1970,
discloses a migration imaging system which relates to
transparentizing background portions of an imaged member,
apparently by an agglomeration effect. In that system an imaging
member comprising a softenable layer containing a fracturable layer
of electrically photosensitive migration marking material is imaged
in one process mode by electrostatically charging the member,
exposing the member to an imagewise pattern of activating
electromagnetic radiation, and then softening the softenable layer
by exposure for a few seconds to a solvent vapor thereby causing a
selective migration of the migration material in the softenable
layer in the areas which were previously exposed to the activating
radiation. The vapor developed member is then subjected to a
heating step causing the migration material in unexposed areas to
agglomerate or flocculate, often accompanied by fusion of the
marking material particles, thereby resulting in a very low
background image. Alternatively, the migration image may be formed
by heat followed by exposure to solvent vapors and a second heating
step which results in background reduction. In this imaging system,
the softenable layer remains substantially intact after
development, with the image being self-fixed because the marking
material particles are trapped within the softenable layer. In the
embodiments thereof the final migration image having low background
is typically formed by some combination of vapor-heat
treatment.
In new and growing areas of technology such as the migration
imaging systems of the present invention, new methods, apparatus,
compositions of matter, and articles of manufacture continue to be
discovered for the application of the new technology in new modes.
The present invention relates to a new and advantageous migration
imaging system employing overcoated imaging members.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to provide a novel
migration imaging system.
It is another object of this invention to provide novel migration
imaging members.
It is another object of this invention to provide a novel migration
imaging system wherein development is carried out substantially by
heat.
It is another object of this invention to provide developed
migration images having very low backgrounds.
It is another object of this invention to provide a more simple and
more economical migration imaging system.
It is a further object of this invention to provide a novel
migration imaging member and system wherein the imaging members are
protected from external destructive forces such as abrasion,
fingerprinting, dusting and the like, both before and after
imaging.
It is still another object of this invention to provide an imaging
system capable of producing opaque, translucent or even transparent
imaged members, the latter resembling photographic film and
microfilm in some embodiments.
The foregoing objects and others are accomplished in accordance
with this invention wherein overcoated migration imaging members
are used in conjunction with migration imaging systems.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention as well as other
objects and further features thereof reference is made to the
following detailed disclosure of the preferred embodiments of the
invention taken in conjunction with the accompanying drawings
thereof, wherein;
FIG. 1 shows a partially schematic, cross sectional view of a
typical layered configuration migration imaging member.
FIG. 2 shows a partially schematic, cross-sectional view of a
typical binder-structured migration imaging member.
FIG. 3 shows a partially schematic, cross-sectional view of a
preferred embodiment of the novel multi-layered or overcoated
migration imaging member of this invention.
FIG. 4 illustrates in partially schematic, cross-sectional views,
the process steps in preferred embodiments of the advantageous
system of the present invention.
FIG. 5 shows a partially schematic, cross-sectional view of another
preferred embodiment of the novel multi-layered or overcoated
migration imaging member of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Migration imaging members typically suitable for use in the
migration imaging processes described above and in the copending
applications cited above, are illustrated in FIGS. 1 and 2. In the
migration imaging member 10, illustrated in FIG. 1, the member
comprises substrate 11 having a layer of softenable material 13
coated thereon, and the layer of softenable material 13 has a
fracturable layer of migration marking material 14 contiguous the
upper surface of softenable layer 13. In various embodiments, the
supporting substrate 11 may be either electrically insulating or
electrically conductive. Electrically insulating substrate
materials will typically have resistivities of not less than about
10.sup.12 ohm-cm., and resistivities preferably not less than about
10.sup.14 ohm-cm. In some embodiments the electrically conductive
substrate 11 may comprise a supporting substrate 11 having a
conductive coating 12 coated onto the surface of the supporting
substrate upon which the softenable layer 13 is also coated. The
substrate 11 may be opaque, translucent, or transparent in various
embodiments including embodiments wherein the electrically
conductive layer 12 coated thereon may itself be partially or
substantially transparent. The fracturable layer of marking
material 14 contiguous the upper surface of the softenable layer 13
may be coated onto, or slightly, partially, or substantially
embedded in softenable material 13 at the upper surface of the
softenable layer.
In FIG. 2 migration imaging member 10 also comprises supporting
substrate 11 having softenable material layer 13 coated thereon.
However, in this configuration the migration marking material 14 is
dispersed throughout softenable layer 13 in a binder-structured
configuration. As in the layered configuration embodiment
illustrated in FIG. 1, the substrate may be opaque, translucent, or
transparent, electrically insulating or electrically
conductive.
Copending applications in Ser. No. 837,780, filed June 30, 1969,
and Ser. No. 837,591, filed June 30, 1969, describe migration
imaging systems suitable for use in the present invention in great
detail, and all the disclosure therein, and especially the
disclosure relating to such imaging processes, imaging members and
materials suitable for use in the migration imaging members used
therein, is hereby expressly incorporated by reference in the
present specification.
In FIG. 3 a preferred embodiment of the novel multilayered or
overcoated structure of the present invention is shown wherein
supporting substrate 11 has a layer of softenable material 13
coated thereon. In the embodiment illustrated in FIG. 3 the
migration marking material 14 is initially arranged in a
fracturable layer contiguous the upper surface of softenable
material layer 13. However in other embodiments, the migration
marking material 14 may be dispersed throughout softenable layer 13
as in the binder structured configuration illustrated in FIG. 2. In
the preferred embodiment illustrated in FIG. 3 the migration
imaging member also includes an advantageous overcoating layer 15
which is coated over softenable layer 13, of the fracturable layer
of marking material 14 contiguous the upper surface of softenable
layer 13. In various embodiments of this novel migration imaging
member, the overcoating layer 15 may comprise another layer of
softenable material, a hard protective overlayer, a gelatin
overlayer which gives particularly advantageous imaging results, or
any other suitable overlayer material.
The materials suitable for use as substrates 11, softenable layers
13, and migration marking materials 14, are the same materials
disclosed in the aforementioned copending applications which are
incorporated by reference herein. As stated above, the substrate 11
may be opaque, translucent, transparent, electrically insulating or
electrically conductive. Similarly, the substrate and the entire
migration imaging member which it supports may be in any suitable
form including a web, foil, laminate or the like, strip, sheet,
coil, cylinder, drum, endless belt, endless mobius strip, circular
disk or other shape. The present invention is particularly suitable
for use in any of these configurations.
In various embodiments of the novel migration imaging members of
the present invention, the migration marking material may be
electrically photosensitive, photoconductive, photosensitively
inert, magnetic, electrically conductive, electrically insulating,
or any other combination of materials suitable for use in the
migration imaging system.
The softenable material 13 may be any suitable material which may
be softened by liquid solvents, solvent vapors, heat, or
combinations thereof. In addition, in many embodiments of the
migration imaging member, the softenable material 13 is typically
substantially electrically insulating and does not chemically react
during the migration force applying and developing steps of the
advantageous system of the present invention. It should be noted
that layer 11 should preferably be substantially electrically
insulating for the preferred modes hereof of applying electrical
migration forces to the migration layer but more conductive
materials may be used because of the increased capability in the
electrical mode hereof of applying a constant and replenishing
supply of charges in image configuration. Although the softenable
layer has been described as coated on a substrate, in some
embodiments the softenable layer may itself have sufficient
strength and integrity to be substantially self-supporting, and may
be brought into contact with a suitable substrate during the
imaging process.
Where the advantageous overlayer 15 comprises a softenable material
similar to the material of layer 13, the overlayer may include
materials in the classes of polystyrenes, alkyd substituted
polystyrenes, polyolefins, styrene-acrylate copolymers,
styrene-olefin copolymers, silicone resins, phenolic resins,
amorphous glasses and others. Such materials more particularly
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 polystyrene-olefin copolymer
from Velsicol Chemical Corp.; Hydrogenated Piccopale 100, Piccopale
H-2, highly branched polyolefins, Piccotex 100, a styrene-vinyl
toluene copolymer, Piccolastic A-75, 100 and 125, all polystyrenes,
Piccodiene 2215, a polystyrene-olefin copolymer, all from
Pennsylvania Industrial Chemical Corp.; Araldite 6060 and 6071,
epoxy resins from Ciba; Amoco 18, a polyalpha-methylstyrene from
Amoco Chemical Corp.; R5061A, a phenylmethyl silicone resin and
M-140, a custom synthesized styrene-co-n-butylmethacrylate, from
Dow Corning; Epon 1001, a bisphenol A-epichlohydrin epoxy resin,
from Shell Chemical Corp.; and PS-2, PS-3, both polystyrenes, and
ET-693, and Amberol ST, phenol-formaldehyde resins; ethyl
cellulose, and Dow C4, a methylphenylsilicone, all from Dow
Chemical; a custom synthesized 80/20 mole percent copolymer of
styrene and hexylmethacrylate having an intrinsic viscosity of
0.179 dl/gm; other copolymers of styrene and hexylmethacrylate, a
custom synthesized polydiphenylsiloxane; a custom synthesized
polyadipate; acrylic resins available under the trademark Acryloid
from Rohm & Haas Co., and available under the trademark Lucite
from the E.I. duPont de Nemours & Co.; thermoplastic resins
available under the trademark Pliolite from the Goodyear Tire &
Rubber Co.; a chlorinated hydrocarbon available under the trademark
Aroclor from Monsanto Chemical Co.; thermoplastic polyvinyl resins
available under the trademark Vinylite from Union Carbide Co.;
other thermoplastics disclosed in Gunther et al. Pat. No.
3,196,011; other materials disclosed in copending application Ser.
No. 27,890, filed Apr. 13, 1970; waxes and blends, mixtures and
copolymers thereof. The above group of materials is not intended to
be limiting, but merely illustrative of materials suitable for such
softenable overlayers.
The above list of softenable materials suitable for overlayer 15
generally includes materials also suitable for softenable layer 13.
However, in various embodiments the overlayer 15 and softenable
layer 13 need not comprise the same material. In various
embodiments advantageous overlayer 15 may itself be substantially
electrically insulating, electrically conductive, photosensitive,
photoconductive, photosensitively inert, or have any other desired
properties. For example, where the overlayer is photoconductive, it
may be used to impart light sensitivity to the imaging member
through the techniques of xerographic technology. The overlayer may
also be transparent, translucent or opaque depending upon the
imaging system in which the overcoated member is desired for use.
Where the overlayer comprises substantially electrically insulating
softenable materials, it will typically have resistivities not less
than about 10.sup.10 ohm-cm., and preferably have resistivities of
not less than about 10.sup.12 ohm-cm.. Advantageous overlayer 15 is
typically preferably of a thickness up to about 75 microns,
although thicker overlayers may be suitable and desirable in
certain embodiments. For example if the overlayer is electrically
conductive there are virtually no limitations except for the
practical ones of handling and economics. Where the overlayer is
greater than about 75 microns thick, undesirably high potentials
may have a greater tendency to build up on the imaging member
during processing in migration imaging systems.
Where the advantageous overlayer 15 comprises material which is
typically harder than the softenable material typically used in
layer 13, the overlayer may include materials such as Bavick 11, a
copolymer of alpha methyl styrene and methyl methacrylate; Mylar, a
polyester resin available from DuPont; Elvacet, a polyvinyl acetate
resin available from DuPont; and others as well as mixtures and
copolymers thereof.
These harder overcoatings are particularly advantageous for the
purpose of protecting the migration imaging members of the present
invention from external destructive forces such as abrasion,
fingerprinting, dusting, and the like. It will be appreciated that
these advantageous overcoatings protect the migration imaging
members before imaging, during imaging and after the members have
been imaged to contain the desired migration image. These
overcoatings are typically preferably not greater than about 75
microns thick if they are substantially electrically insulating.
Conductive overcoatings may typically be as thick as desired.
These harder overcoatings, unlike the softenable material
overcoatings described above, are typically not preferred for use
in softenable layer 13. However, the harder overcoatings typically
permit charge transport through the overlayer 15 (at least during
development of the latent image on the member), transfer of the
charge to the imaging particles 14, subsequent migration of the
marking particles 14 in the suitably softened underlayer 13, and
possess various other properties which allow the migration imaging
process of the present invention to be performed
satisfactorily.
These harder overcoatings will typically not appreciably soften
when the migration imaging members are developed by the application
of heat sufficient to soften the softenable layer 13. However in
various embodiments, it may be advantageous to use harder overlayer
materials which, while not preferred as materials for softenable
layer 13, may soften with increased application of heat or solvent
vapors; may permit solvent vapor to penetrate to the softenable
layer; may allow charge migration before or during heating or
exposure to solvent vapor; may permit removal of the overlayer by
stripping or solvent flushing without effecting the underlying
imaging structure; or may be suitable for use as substrates where
the overlayered migration imaging member is split to produce
complementary images, for example, as described in copending
application Ser. No. 784,164, filed Dec. 16, 1968, now U.S. Pat.
No. 3,741,757.
In still other embodiments, the advantageous overlayer 15 may
comprise a suitable layer of gelatin. Such gelatin layers have been
found to be particularly advantageous in a preferred embodiment of
the novel migration imaging system of the present invention. Any
suitable grade of gelatin may comprise overlayer 15 in this
embodiment. For example, typical grades are edible, photographic,
technical, and U.S.P. XVII. These gelatins are generally colorless;
transparent; odorless; tasteless; absorb up to five to 10 times
their weight of water; are soluble in hot water, glycerol and
acetic acid; and insoluble in alcohol, chloroform, and other
organic solvents. These gelatins are commonly used in the
manufacture of photographic films; lithography; sizing; plastic
compounds; textile and paper work; foods; rubber substitutes;
adhesives; cements; capsules for medicinals; artificial silk;
matches; light filters; clarifying agents; bacteriology; and
medicine.
Due to their desirable film forming characteristics and chemical
composition, photographic grade gelatins are preferred grades of
gelatins for use in the instant invention. These gelatins comprise
any naturally occurring protein used as the binding medium for
silver halide crystals in the common type of photographic
emulsions, and are not limited to any particular definite chemical
compound. A given sample of gelatin may contain molecules of
various molecular weights ranging from about 20,000 to over
100,000, and of various amino-acid compositions. The gelatin
coating is normally dissolved in water and coated over the surface
of the softenable layer 13 which contains the migration marking
particles. A more inclusive definition for gelatin compounds
falling within the scope of this invention is set forth under the
definition of "gelatin" contained in the Focal Encyclopedia of
Photography, Vol. 1, Focal Press, London and New York, 1965, pp.
695 and 696.
The thickness of the gelatin layer generally should range from
about 0.01 to 1.0 microns. A preferred range of thickness which
yields outstanding results is from about 0.1 to 0.5 microns. The
thin gelatin layer may be applied by any suitable technique.
The advantageous imaging members of the present invention described
above, are useful in the novel imaging systems described in
conjunction with FIG. 4. The imaging steps in the advantageous
processes using the novel imaging members of the present invention
typically comprise the steps of forming an electrical latent image
upon the imaging member, and developing the latently imaged member
by decreasing the resistance of the softenable material to the
migration of the particulate marking material through the
softenable layer 13 whereby migration marking material is allowed
to migrate in depth in softenable material layer 13 in an imagewise
configuration. The imaging members illustrated in FIG. 4 are the
layered configuration imaging members like that illustrated in FIG.
3. However, binder structured imaging members such as illustrated
in FIG. 2 and as described in conjunction with FIG. 3 may also be
used in the advantageous imaging systems of the present invention
as described in FIG. 4.
Any method for forming an electrical latent image upon the imaging
member may typically be used in the advantageous process of the
present invention. For example, the surface of the imaging member
may be electrically charged in imagewise configuration by various
modes including charging or sensitizing an image configuration
through the use of a mask or stencil, or by first forming such a
charge pattern on a separate layer such as a photoconductive
insulator layer used in conventional xerographic reproduction
techniques, and then transferring this charge pattern to the
surface of a migration imaging plate by bringing the two into very
close proximity and utilizing break-down techniques as described
for example in Carlson U.S. Pat. No. 2,982,647, and Walkup U.S.
Pat. Nos. 2,825,814 and 2,937,943. In addition, charge patterns
conforming to selected shaped electrodes or combinations of
electrodes may be formed on a support surface or combinations of
electrodes may be formed on a support surface by the TESI discharge
technique, as more fully described in Schwertz U.S. Pat. Nos.
3,023,731 and 2,919,967, or by techniques described in Walkup U.S.
Pat. Nos. 3,001,848, or by induction imaging techniques, or even by
electron beam recording techniques, as described in Glenn U.S. Pat.
No. 3,113,179.
Where the migration marking material or the softenable material is
electrically photosensitive material, the electrical latent image
may be formed on the imaging member by electrostatically charging
the member and then exposing the charged member to activating
electromagnetic radiation in an imagewise pattern. This is the
method illustrated in FIG. 4A and 4B. In FIG. 4A the advantageous
imaging member of the present invention comprising substrate 11
having softenable layer 13 thereon with fracturable layer of
marking material 14 contiguous the surface of the softenable layer
13, and advantageous overcoating 15 thereon, is shown being
electrostatically charged with corona charging device 16. Where
substrate 11 is conductive, the charging step is enhanced by
grounding the conductive substrate as shown at 17. Similarily,
where the substrate 11 is electrically insulating, the electrically
insulating substrate may be placed on a grounded conductive backing
to enhance the charging step. Still another method of electrically
charging such a member is to electrostatically charge both sides of
the member to surface potentials of opposite polarity. In FIG. 4B
the charged member is shown being exposed to activating
electromagnetic radiation 18 in area 19, thereby forming an
electrical latent image upon the imaging member.
The member havng the electrical latent image thereon is then
developed by decreasing the resistance of the softenable material
to migration of the particulate marking material through the
softenable layer 13, here for example as shown in FIG. 4C by
softening by the application of heat shown radiating into the
softenable material at 21. The application of heat, solvent vapors,
or combinations thereof, or any other means for decreasing the
resistance of the softenable material of softenable layer 13 to
migration of the migration marking material may be used to develop
the latently imaged member, whereby migration marking material 14
is allowed to migrate in depth in softenable layer 13 in imagewise
configuration. In FIG. 4C the migration marking material is shown
migrated in areas 20, and in its initial, unmigrated state in area
19. It is seen that areas 19 and 20 correspond to the formation of
the electrical latent image described in conjunction with FIGS. 4A
and 4B.
Depending upon the specific imaging system used, including the
specific imaging structure, materials, process steps, and other
parameters, the advantageous imaging system of the present
invention may produce positive images from positive originals or
negative originals from positive originals.
The migrated, imaged member illustrated in FIG. 4C is shown with
the protective layer 15 thereon. It is seen that this layer 15
protects the imaging member before, during, and after imaging.
Where the advantageous imaging member of the present invention
described in FIG. 3 wherein the advantageous overlayer 15 is a
gelatin as described above, is used, the imaging process of the
present invention as described in conjunction with FIG. 4 produces
still other surprising and advantageous results. Particularly
advantageous results are achieved when the migration marking
material is initially oriented in the fracturable layer contiguous
the upper surface of softenable material layer 13. In this process
the imaging steps may be carried out as described in FIGS. 4A, 4B,
and 4C. However, it is particularly noticeable in the advantageous
system of this invention that the migration marking material 14 in
area 19 as shown in FIG. 4C remains substantially exactly in its
initial unimaged position. Surprisingly it has been found that the
presence of gelatin overlayer 15 helps to maintain the unmigrated
marking material 14 in area 19 in this initial position.
In the development step illustrated in FIG. 4C, the imaging member
is typically developed by uniformly heating the structure to a
relatively low temperature. This temperature is generally within
the range between about 60.degree. to about 130.degree.C. and the
heat is applied for only a few seconds. When the heat is applied,
the softenable material layer 13 decreases in viscosity, thereby
decreasing its resistance to migration of the marking material
through the softenable layer, and the marking material is permitted
to migrate in depth in the softenable layer 13, and is here shown
migrating in the unexposed areas 20.
In addition to marking material particle migration, under some
conditions an advantageous fusing or agglomeration effect,
illustrated in FIG. 4D, may occur whereby migrated marking
particles fuse or agglomerate to form larger particles 22 which
typically are migrated away from the gelatin layer-softenable layer
interface. As before, it is noted that the particles which have
been exposed to light in areas 19 did not fuse or agglomerate, and
are maintained in essentially their initial unmigrated position
contiguous the surface of the softenable material 13. This last
effect is aided by advantageous overlayer 15 as discussed
above.
The image formed by the development steps illustrated in FIG. 4
results in a higher quality light absorbing image because of the
agglomeration or selective fusing of the migration marking
material. This image has a lower background than images obtained by
using the same structure without the gelatin overcoating. This
imaging process is further believed to be novel in that contrary to
the usual migration imaging process set forth in copending
application Ser. No. 71,781 filed Sept. 14, 1970 (the entire
disclosure of which is hereby expressly incorporated by reference
in the present specification), only those particles which have
migrated away from the gelatin layer-softenable layer interface,
fuse together. Therefore, it is seen that the novel imaging
structure and process of the present invention offers a new
approach to obtain more fully heat or vapor softened, developed
migration imaging films which have low background images. At the
same time, this film also provides enhanced protective
characteristics such as lower tack and greater resistance to
abrasion, before, during and after image formation.
Furthermore, the system of the present invention puts less critical
demands on the migration process in that the migration marking
particles need only leave the immediate vicinity of the gelatin
layer-softenable layer interface to achieve a higher contrast
image. The migration imaging systems clearly disclosed in the above
mentioned copending applications typically operate with more
extensive migration wherein the migration marking materials migrate
relatively considerably in depth in the softenable material
layer.
Still another embodiment in the advantageous system of the present
invention is described in FIG. 5 wherein the migration imaging
member is overlayered with two separate layers of protective
material. The member illustrated in FIG. 5 comprises substrate 11,
softenable material 13 and migration marking material 14 having an
intermediate protective layer 23 coated onto the softenable
material 13 between the softenable material and protective layer
15. It has been found particularly advantageous to use imaging
members in this configuration wherein the intermediate protective
layer 23 comprises a gelatin such as those described above herein,
and protective layer 15 comprises the hard-type coatings which are
also described above herein.
The following examples further specifically define the present
invention wherein overcoated migration imaging members are used in
conjunction with novel migration imaging systems. The parts and
percentages are by weight unless otherwise indicated. The examples
below are intended to illustrate various preferred embodiments of
the novel migration imaging system.
EXAMPLE I
An imaging member or film such as that illustrated in FIG. 3 is
prepared by first making a mixture of about 20% by weight of
hydrogenated Piccopale 100 (HP-100), a highly branched polyolefin,
available from the Pennsylvania Industrial Chemical Co., dissolved
in a solution of toluene. Using a gravure roller, the mixture is
then roll coated onto an about 3 mil aluminized Mylar polyester
film (E.I. duPont de Nemours Co., Inc.) having a thin,
semi-transparent aluminum coating. The coating is applied so that
when air dried for about 2 hours to allow for evaporation of the
toluene, an imaging plate comprising about a two micron layer of
HP-100 is formed on the aluminized Mylar. A thin layer of
particulate vitreous selenium approximately 0.5 microns in
thickness is then deposited onto the Staybelite surface by inert
gas deposition utilizing the process set forth in copending patent
application Ser. No. 423,167, filed on Jan. 4, 1965. An about 0.5
micron coating of photographic grade gelatin available from the
American Agricultural Chemical Co. under the tradename Keystone
Gelatin is then applied over the selenium layer by dip coating from
a 1% solution by volume of gelatin in water, and allowing the
coating to dry resulting in a gelatin overlayer about 0.5 microns
thick.
EXAMPLE II
An imaging member or film is formed by the method of Example I in
which the HP-100 is replaced with an about 20% mixture of an about
80/20 mole per cent copolymer, called P-37, of styrene and
hexylmethacrylate, dissolved in toluene. About 10 grams of Keystone
gelatin powder is dissolved in about 100 cc. of water, and this
gelatin solution is coated onto the surface of the bare imaging
film with a No. 5 draw rod. This structure is then dried in an oven
at about 50.degree.C. for about 1 hour. The resultant member
comprises a thin, particulate vitreous selenium layer approximately
0.5 microns in thickness deposited at the upper surface of the
softenable plastic layer of P-37 which is contained on an about 3
mil aluminized Mylar substrate, and this member is overcoated with
a layer of gelatin of about 0.5 microns in thickness.
EXAMPLE III
The gelatin overcoated imaging structure provided by Example II is
further overcoated by applying a solution of about 10% Bavick II, a
copolymer of alpha methylstyrene and methyl methacrylate from J. T.
Baker Co., in toluene solvent, with a No. 7 draw rod. This Bavick
coating is placed directly over the gelatin coating.
EXAMPLE IV
An uncoated imaging member is provided as described in Example I. A
solution of about 10% Bavick II in toluene solvent is coated with a
No. 7 draw rod onto another film of Mylar which has been previously
coated with zinc stearate (a release agent). The Bavick coated
Mylar is then laminated to the uncoated imaging structure by
placing them face-to-face together and passing this Mylar
sandwiched imaging member between a pair of hot rollers at
temperatures in the range of about 70.degree. to 80.degree.C. This
type of overcoated member is suitable for stripping or splitting
typically after imaging such a member.
EXAMPLE V
An uncoated imaging structure is provided as described in Example
I. A coating solution of Elvacite, an acrylic resin available from
DuPont, is dissolved in n-propanol, and this solution is coated to
a thickness of about 2 microns onto the uncoated imaging structure
with a No. 7 draw rod. This coated structure is then allowed to air
dry at room temperature.
EXAMPLE VI
An uncoated imaging structure is provided as described in Example
I. An about 10% solution of Piccopale H-2, a cyclic hyhdrocarbon
resin produced by polymerizations of unsaturates derived from deep
cracking of petroleum, available from Pennsylvania Industrial
Chemical Corp., is prepared in octane solvent, and an about 1/2
micron layer of this solution is coated onto the uncoated imaging
structure with a No. 5 wire wound draw rod and allowed to dry. A
solution of Bavick in acetone is then coated over the H-2 coating
with a No. 10 draw rod. This structure is then baked for about 1
hour at about 65.degree.C. The H-2 interlayer prevents solvents in
which the Bavick overlayer is prepared from affecting the
underlying imaging member.
EXAMPLE VII
An uncoated imaging structure is provided as described in Example
I. A protective film of Mylar about 19 microns thick is laminated
to the uncoated imaging structure by placing the Mylar film on the
surface of the uncoated member and by passing this Mylar sandwiched
structure between a pair of heated rollers at temperatures in the
range between about 70.degree.C. and about 80.degree.C.
EXAMPLE VIII
An uncoated imaging structure is provided as described in Example
II. A protective overcoating of Saran, poly-vinylidene chloride,
about 10 microns in thickness is coated over the uncoated imaging
structure. This is done by simply laying the Saran film upon the
surface of the uncoated member without a lamination step, or,
alternatively, the Saran layer is laminated to the uncoated imaging
member by passing the sandwiched member between a pair of hot
rollers at about 65.degree.C.
EXAMPLE IX
An uncoated imaging structure is provided as described in Example
II wherein P-37 is the softenable layer. A water solution of
polyvinyl methyl ether is prepared and wipe coated onto the surface
of the uncoated imaging member. This overcoating dries at room
temperature for about 1/2 hour leaving an about 1 micron thick
overcoating on the imaging member.
EXAMPLE X
An uncoated imaging structure is provided as described in Example
II with P-37 as the softenable layer. A solution of usually
crystalline polyester polyxylene sebacate in chloroform is dip
coated onto a film of aluminized Mylar and allowed to dry for about
1 hour at room temperature. The coated aluminized Mylar and the
uncoated imaging structure are then placed face-to-face in a
sandwich configuration and laminated by passing the sandwich
structure through a pair of hot rollers at about 65.degree.C. This
member may be stripped or split.
EXAMPLE XI
The film made by the method of Example I is imaged as follows: The
film is charged under dark room conditions to a positive potential
of about 200 volts by a corona charging device such as that
disclosed in U.S. Pat. No. 2,588,699 to Carlson. The plate is then
exposed to a light source of about 5 foot-candle-seconds, and then
heated to a temperature of about 100.degree.C. for about 2 seconds.
This procedure results in a formation of a positive to negative
image formed by the fusion of the selenium particles in the
non-exposed areas.
EXAMPLE XII
A sample of the imaging film of Example II is imaged as follows:
The film is charged to a retained negative potential of about 120
volts. The charged film is then exposed to a pattern of light equal
to about 2.5 foot-candle-seconds. The film is then heated to a
temperature of about 100.degree.C. for about 2 seconds resulting in
the formation of a positive to positive image.
EXAMPLES XIV - XVIII
Structures used: Examples III - VII
Charging: negative from 10 to 40 volts/micron with higher fields
preferred
Exposure: 1 .times. 10.sup.12 photons/cm.sup.2 of 4000.sup.A
light
Development: on a hot plate at 110.degree.C. for 1 minute or at
118.degree.C. for a few seconds.
Result: partial migration in the exposed areas. Exposed areas
appear light blue while unexposed areas have original red-orange
color. Image is the same as if there had been no overlayer.
EXAMPLE XIX
Structure used: Example VIII
Charging: -200 to -600 volts with -600 volts preferred
Exposure: 1 .times. 10.sup.12 photons/cm.sup.2 of 4000A light
Development: on a hot plate at 110.degree.C. for 1 minute or
118.degree.C. for a few seconds.
Result: as in Examples XIV - XVIII
EXAMPLE XX
As in Example XIX except additional step of stripping away Mylar
while on the hot plate.
Result: Two images. Positive to negative on the original film base
and positive to positive on the Mylar base.
EXAMPLE XXI
Structure Used: Example IX
Charging: -60 to -160 volts
Exposure: 1 .times. 10.sup.12 photons/cm.sup.2 of 4000 A light
Development: Hot plate for 5 seconds at 110.degree.C.
Result: as in Examples XIV - XVIII
EXAMPLE XXII
Structure used: Example X
Charging: -60 to -300 volts
Exposure: as in Example XXI
Development: as in Example XXI
Result: as in Examples XIV - XVIII
EXAMPLE XXIII
Structure used: Example XI
Charging: -160 volts
Exposure: as in Example XXI
Development: as in Example XXI
Result: as in Examples XIV - XVIII
EXAMPLE XXIV
Structure used: Example IX
Charging: +100 to +400 volts
Exposure: as in Example XXI
Development: as in Example XXI
Result: as in Examples XIV - XVIII
EXAMPLE XXV
Structure used: Example X
Charging: +120 to +200 volts
Exposure: as in Example XXI
Development: as in Example XXI
Result: as in Examples XIV - XVIII
EXAMPLE XXVI
Structure used: Example XI
Charging: +160 volts
Exposure: as in Example XXI
Result: as in Examples XIV - XVIII
EXAMPLE XXVII
Structure used: Example VIII
Charging: +700 to +1300 volts
Exposure: as in Example XXI
Development: as in Example XXI
Result: Partial migration in the unexposed area and no migration in
the exposed area
EXAMPLE XXVIII
Structure used: Example III
Charging: +140 to +260 volts
Exposure: as in Example XXI
Development: as in Example XXI
Result: as in Example XXVII
EXAMPLE XXIX
Same as Example XXVIII except higher temperature (at
120.degree.C.).
Result: Se particles fuse in unexposed areas (partially migrated
areas) producing remarkable increase in transparency in these
areas.
EXAMPLE XXX
An imaging member is prepared by overcoating aluminized Mylar with
an about 2 micron layer of P-37 softenable material, and powdered
graphite is cascaded over the surface of the softenable layer
thereby forming a fracturable layer of graphite at the surface of
the softenable layer. This member is overcoated with an about 19
micron layer of Mylar as in Example VIII. This overcoated imaging
member is imagewise charged by electrostatically charging through a
stencil mask, and is then heated for about 20 seconds at about
110.degree.C. to soften the softenable material thereby allowing
the graphite particles to migrate toward the substrate in the
imagewise charged areas.
EXAMPLE XXXI
An imaging member is prepared by dispersing graphite particles
throughout a P-37 solution before coating upon an aluminized Mylar
substrate. This binder layer having graphite dispersed throughout
the P-37 softenable layer is then overcoated with an about 19
micron layer of Mylar as described in Example VIII. This imaging
member is charged and developed as in Example XXX.
Although specific components and proportions have been stated in
the above description of the preferred embodiments of the novel
migration imaging system wherein overcoated migration imaging
members are used, other suitable materials and variations in the
various steps in the system as listed herein, may be used with
satisfactory results and various degrees of quality. In addition,
other materials and steps may be added to those used herein and
variations may be made in the process to synergize, enhance or
otherwise modify the properties of or increase the uses for the
invention.
It will be understood that various other changes of the details,
materials, steps, arrangements of parts and uses 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 principal and scope of this
invention.
* * * * *