Note: Descriptions are shown in the official language in which they were submitted.
1~4~
This in~ention~relates genera Tao
electrophotographic imaging methods and apparatus for
making permanent transparencies for archival or for
secondary usage such as for projection or the like. Gore
p~ticularly, the invention concerns the provision ox an
improved eIectrophbtographic imaging method and means
including dry transfer of an electrostatically formed
toned image under localized heat and pressure to a transfer
medium comprising Arizona coated transparent sheet to
form a high resolution transparency having the transferred
image embedded within and below the surface of the coating
carried by said sheet.
Various processes have been proposed for
producing an image electrostatically upon a substrate,
including photographic processes involving actinic exposure
of a photosensitive material carried on a substrate or by
exposing a charged electrophotographic member having a
photo conductive surface coating or layer to radiation to
produce an electrostatic latent image thereupon. This
latent images rendered visible by application of dry toner
particles thereto as in cascade type develop mentor by wet
application thereto of a liquid toner suspension wherein
the toner particles have electrophoretic properties.
The production of suitable transparencies
commonly requires the skill of a trained technician and
the substantial expenditure of money and time. Photographic
reproduction processes require controlled exposure,
development, washing and fixing of a light sensitive
composition present one support with or without the
intermediate production of a negative image.'
Jo
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447~
Xerographic processes have proven to be an easy
and reliable techni~ue'for the production of transparencies.
Notwithstanding the desirability of these processes,
drawbacks have been encouIItered in that the adherence of the
image on the transparent support leaves machete be desired.
additionally, loss- of optical density and resolution is .'
experienced when the toned image is transferred to a
receiving member.
With the advent of the electxoph~ogxaphic
member disclosed in US Patent 4,025,339, the achievement
of heretofore impossible to obtain resolution Al capabilities
became possible, Toned images were formed
eIectrophotographically by applying a charge potential on
the photoconductive'coating, expose the charged coating to-
a radiation image, usually actinic light, toning of the
resultant latent image and transferring the toned image onto
a carries by electrically assisted methods. The carriers
employed were paper or plastic sheet material.
The toning step was effected generally by
2Q. electrophoretic methods employing very finely divided
particulate toner material suspended in an insulating liquid
and attracted to the photo conductive surface by the charge
magnitude of the latent image. Electrically assisted
methods employing development electrodes and the like have
been applied to achieve complete transfer. Normally, the
toned image adheres to the photo conductive surface in
accordance with the electrical field strength of the latent
image until the toner either was fused onto the surface or
transferred to the carrier material and used thereupon.
methods employed for transfer.convention~lly often resulted
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in formation ox copies which lose a considerable degree of
the ox~ginal optical density and could note transerxed
with retention of the high degree of resolution capable of
being achieved with'the'photoconductiYe coating of the'
S patented eIectrophQtographic member. Toner particles had
difficulty adhering as well as desired and may flake or
chip off the surface to which they were transferred. The
toner particles adhered to the surface only and were fused
onto the surface. Lateral movement of the particles could
lo ooze during transfer so that the'faithul reproduction of
the ox~ginal image may be'di~ficu~t, if not impossible.
The particle size of toner particles desirably
should be as small as possible in order to gain the most
~dvantage`o~ the novel patented ~lectxophotographi'c member.
Dry particles useful for toning purposes as by cascade
tuning methods generally have a particle size which is too
large. Toner particles of proper size are encountered in
liquid suspensions and axe not available except in such
suspensions. 'Pry tones normally are applied by way of
squalled cascade systems normally bulky and expensive. The
Tokyo facing the art Was to Cain the advantages of using a
toner to achieve maximum resolution yet have the convenience
of a dry transfer system. Adhesives have been employed as
coatings for transfer carriers but for many reasons have
I not been widely accepted since they normally require curing
to eliminate distortion of the transferred image both
initially and in subsequent handling and storage. Also, complete
transfer is difficult to achieve. Toner material may be
left on the Aztecs electrophQtographic member so that the
member cannot be immediately reused.
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It is important in Mooney iodize of use such as
microfilm or microfiche reproduction to acquire the
maximum resolution of the image. Thus of the
patented film as archival material has been possible
and in act sought in order to gain advantage of the
resolution capabilities of the said material. Of
disadvantage is the photocanductive coatings employed
within the-scope ox the patented eIectxophotographic
material which generally have a characteristic tint.
When the photo conductive coating is cadmium sulfide,
these is a characteristic yellow color. Of
disadvantage also is the relatively high cost of the
electrophotoconductive material. Using conventional
methods, one could transfuser the toned image to
lo txan~parent plastic sheet material but adherence was
not satisfactory. Resolution and optical density
retention was reduced during transfer. disavow coatings
have been suggested but have not been satisfactory to
the extent desired dun to "blocking" tendencies, that
is the tendency of coated sheets to adhere to superposed
like coated sheets, difficulties encountered in coating
the adhesive materials, the lack of satisfactory light
transoms characteristics of the coated material,
axing and loss of adhesiveness of the coating, peeling
ox flaking of the coating from the substrate.
One problem involved in the achievement of
transfer of the toned image from the electrophotographic
material to a coated transfer medium is the transport
without damage or disturbance of the toner image.
Conventional transfer media require that the transferred
toner image be fixed or fused to the receiving surface
44~
subsequent to receipt thereon. This rickshaws performance
of another function upon the transfer medium,
requiring more time and expense, as well as complex
mechanisms. The transparent transfer media which Jay
be conventionally employed as well as the types of
fusible toner available for use may distort the
transferred image as the same is being transported
through the apparatus. Materials may be ove~coated
upon the transfixed image to aid in binding the same
to the undersurface. on addition to the presence of
still another layer, there would have'to'be'deleterious
effect of such material upon the transparency of the
finished product, the flexibility thereof, etc.
~ccoxdingly, the invention provides a method
of forming a transparency electrostatically wherein a
toned image is formed electrostatically on an
electrophotographic member and transferred to a transparent
transfer medium, said method comprising the steps of
providing a transfer medium which consists of a
transparent substrate carrying a thin surface coating
of a resinous composition compatible with said substrate
and bonded thereto, bringing together said film member
and the transfer medium simultaneously with application
of sufficient heat locally to soften the resinous
coating, applying localized pressure to the engaged film
member carrying the toned image and softened coating of
the transfer medium to laminate same and thereafter
separating said laminated transfer medium and
electrophotographic member, the toner image being
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issue
embedded within said coating and remaining with's aid
transfer medium upon separation, the transfer being
effected without loss in resolution or optical density.
Further, the invention also provides toe
apparatus comprising first and second rollers arranged
to define a nip, feed means for directing an
electrostatically formed dry-toner image carrier and
a transfix member simultaneously to said zip, said
transfer member formed of a transparent substrate
having a heat softenable'resin coating bonded
thereto and compatible therewith, the coating side
facing the toned image carried by the carrier, heating
means capable of locally softening thorazine
coating, means for laminating said transfer member
to said image carrier at said nip, means for cooling
the laminate and jeans for separating the laminate,
the toned image being transferred in its entirety
to the coating of the transfer member when the
laminate is separated, said toner image being embedded
in said coating below its surface without loss in
resolution and optical density.
aye
The preferred embodiments of this invention
now will be described, by way of example,with'reference
to the drawings accompanying this specification in which:
Figure 1 is a diagrammatic representation of
the dry transfer process according to the invention, and
Foggier is a fragmentary section illustrating
the transparency resulting from the method of the invention
The electrophotographic member preferably
'employed herein is that-described in US. Patent 4,025,339
ox Jay 24, 1977. The electrophotographic imaging process
includes charting the photo conductive surface of said
' electrophotographic member, imaging the chàxged success by
exposure to a radiation pattern of the information to be
imaged to form a latent charge image on said surface and
developing said latent electrostatic image`~ith'toner material.
The toner employed comprises fine pigmented particles
suspended in an insulating liquid medium. The toned image
then is permitted to dry after application., Normally, the
toned image would be fused to the surface of an
electrophotographic member but in this invention, only drying
ox the toned image is ejected.
Referring to the diagrammatic representation of
the method and apparatus of the invention, in Figure 1 there
is shown an electrophotographic member 10 formed as a sheet
of substrate material 12 on which is applied a thin layer 14
of ohmic material. A thin coating 16 of microcrystalline
photoconducti~e material is of sputter deposited under
carefully controlled conditions in accordance with the
teachings of US. 4,025,339. Generally the coating is from
3000 Angs~xoms to less than two microns in thickness. The
447~
coated substrate is charged at charging station 18 by corona
generator device 20.'. The charged member is exposed to an
actinic radiation pattern of information desired to be'
reproduced at exposure station 22 and toned at developing
station 24 using a suspension of non fusible toner material
in an insulating liquid medium. The toned images dried
at 26,
. A pair of roller members 28 and 30 are
arranged to define nope 32 to which a sheet of transfer
10. medium 34 is fed simultaneous with toned member 10. Roller 28
is heated to about 170C. Roller 30 is biased to exert a
pressure of 60 pounds pox square inch at the nip 32.. Roller
28' may butted sofas to function as the hoeing roller with:
roller 30 functioning to back up pressure roller 30 and define
the nip 32, Where roller 28 is the sole heating roller,
roller 28' functions as an idler roller. In any event the
resin coating is softened sufficiently at or prior to the nip
32 to enable the toned image to be compressed whereunto.
The transfer sheet 34 comprises a transparent
thin sheet 36 of polyester polymer material manufactured and
sold under the trademark MYLAR by the Dupont Company of
Wilmington, Delaware. The transfer sheet 34 has an overreacted
layer 38 formed of compatible resinous material bonded
permanently to one surface thereof. preferable coating .
material is a thermoplastic polyester resin composition coated
on the sheet of Mylar by conventional coating methods. The
preferred coating material has a softening range of about 140
and can be selected from polyester resins compatible with'
Mylar such as Nos. 46950, 46983 or.49000..sold by Dupont
0 Company (Wilmington, Delaware) or one of. Vitel~resins PI 200,
I YO-YO
~Z~4~7~
PI 207, PI 222, VIE 4$83~ or VIE 5545~ (Go~dyeax).
As an alternative to heating the roller 28, a
hot air vent 40 (brazen outline) may be disposed adjacent
the nip 32 to heft the coating proximate to the line of
contact between member lo and the transfer sheet 38 so as
to soften the coating 38 without affecting the substrate.
The pressure roller 30 may ye formed of metal or of hard
tubber of about 80 dormitory.
The resulting laminate is permitted to cool at
42 and then is peeled apart as at 44. Cooling before
delamination lo nut mandatory. The toned image is
transferred completely with no residue being left on the
photo conductive coating 16 of member I The particles 46
transferred to sheet 34 are embedded in the coating 38 below
its outer surface by being drawn therein while the coating
was softened locally. The surface of sheet 34 after transfer
is very smooth. Some particles of the toner even may migrate
further into the interior of the coating 38, with some
reaching the interface between the coating and the substrate
and others simply gloating. Separation can be performed
Molly or by conventional mechanical separator means.
Separation can be performed "hot".
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