Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
(1) Field Of The Invention
The present invention relates to an electrostatic .
duplicating process and apparatus and, in particular, to the
improved development of electrostatic latent images in such
processes and apparatus. --
The term "electrostatic duplicating process"
as used herein this specification includes all duplicating
processes which include the formation of an electrostatic
latent image. For example, there would be included electro- ~~photographic duplicating processes where an electrostatic
latent image is formed by electrifying the surface of a
photoconductor and subjecting it to imagewise exposure;
electrostatic recording processes where an electrostatic
latent image is formed by scanning the surface of a .
dielectric with a needle electrode; duplicating processes
where an electrostatic latent image is formed by imagewise
exposing a photoconductor while applying thereto a by-pass
electric potential and the like.
(2) Descr~iption Of The Prior Art
Heretofore, electrostatic latent images on a
photoconductive member have been developed with ink-supplying
members having a fine, uneven peripheral portion such as
disclosed in United States Patent No. 3,084, 043. In such ~'
processes, liquid ink is held in the depressions formed on
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ink-supplying member, and the raised portions thereof are
positioned against or close to the surface of the electro- ,
static latent image-bearing photoconductive member, whereby
the ink in the depressions is transferred via the raised
portions to the surface bearing the electrostatic latent -
image by the electrostatic attracting force of the electro-
static charge on the photoconductive member to develop the
latent image. The ink-supplying member may be prepared by
forming slots or grooves, for example, on the surface of a ,~
hard, electroconductive substance such as an iron pipe or by
forming hardened resin dot patterns on a metal plate. Since
the ink-supplying member is in physical contact with the -~
photoconductive member or can contact it if positioned close
thereto, the surface of the photoconductive member is subject
to damage, which in turn results in image ~uality deteriora-
tion. ;A . ~ '
SUMMARY OF THE INVEN~ION
In accordance with one aspect of this inventlon there
is provided apparatus for wet-developing an electrostatic
latent image comprising an electroconductive ink-supply `
member having an uneven surface comprising a plurality of
raised portions and depressions below said raised portions,
at least the surface of said ink-supply member being electro- ~`
conductive; means for supplying ink to said ink-supply member
so that the ink is held in said depressions; an electrophoto-
graphic member bearing said electrostatic latent image; an
elastic, electroconductive support member for said electro-
photographic member, the support member having a resistivity
no greater than 1~1 ohm. cm; and means for bringing the
ink-supply membe-r~and the electrophotographic member into
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substantial contact with one another so that said ink is
attracted to said electrostatic latent image to thereby
develop the image while minimizing damage to the electro-
photographic member because of the elasticity of said elastic
support member.
In accordance with another aspect of this invention
there is provided a method of wet-developing an electro-
static latent image comprising selecting an electroconductive,
ink-supply member having an uneven surface comprising a
plurality of raised portions and depressions below said raised
portions, at least the surface of said ink-supply member being
electroconductive; supplying ink to said ink-supply member so
that the ink is held in said depressions; selecting an
electrophotographic member bearing said electrostatic latent
- image; selecting an elastic, electroconductive support member
for said electrophotographic member, the support membe~ having
a resistivity no greater than 101 ohm. cm; and bringing the
ink-supply member and the electrophotographic member into
substantial contact with one another so that said ink is
attracted to said electrostatic latent image to thereby develop ,~
the image while minimizing damage to the electrophotographic
member because of the elasticity of said elastic support
member.
BRIEF DESCRIPTION OF THE DR~WING
Figure 1 is a diagrammatic view of an ink-supplying
member applying ink to an illustrative embodiment of an
electrophotographic member in accordance with this invention.
Figure 2 is a diagrammatic view of an electrophoto-
graphic apparatus utilizing the wet-developing process of -
this invention.
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`DETAI'-LED DES'~RIPTI'ON :~F PREFE~ EMBO'DIMENTS ,' '`
OF INVENTI`ON ,,.,:
Referring to Figures 1 and 2, various illustra- . -
tive embodiments of the invention will now be described.
An ink-supply member 10 is provided which may
be inelastic (as shown in Figure 1) or elastic and have a
fine, uneven surface. Thus, ink-supply member 10 may comprise
an elastomer having electroconductivity at least at the
surface thereof. A liquid ink 12 is supplied to the ink-
supply member 10 by ink-supplying means (typically com
prising ink container 14 and inking roller 16) to the
depressions or valleys 18 formed on the ink-supplying 'r': ` '
member. The raised portions of the ink-supplying member
are brought into contact with the electrostatic latent
image-bearing surface a light-sensitive member, which ~`
comprises a light-sensitive layer 22 on the surface of an
electroconductive elastic support 24, which may be grounded. ~;
The liquid ink thus held in the depressions 18 is supplied
to the latent image-bearing surface via the raised portions
of the ink-supply member 10 by the electrostatic attracting
action of the electrostatic charge on the light-sensitive
layer 22. A thin metallic layer 26 may be provided between
the electroconductive, elastic support 24 and the light-
sensitive layer 22. Since the latent image-forming surface
of the light-sensitive member is supported by an elastomer,
there is little, if any, probability of the surface of the
light-sensitive layer 22 being damaged upon contact with the
ink-supply member 10. Thus, the durability of the light-
sensitive layer 22 is greatly enhanced and, in addition, the '~?,:`
distinctness of the resulting image is markedly improved.
The resistivity of the electroconductive elastic support
24 should be no greater than 101ohm.cm and preferably no
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greater than lOfi oh~.cm and the thickness should be sufficient
to provide elasticity and should be at least 1 mm.
Several illustrative examples of the invention
will now be described, there being no intent to limit the
scope thereof. -
Rxample 1
Silcone rubber having a Shore hardness of 75
and electric resistivity of 1 x 103 ohm.cm was utilized
as support member 24 and wound around an aluminum pipe of
200 mm. outside diameter and 300 mm. width in thickness of
10 mm. A photoconductive substance of cadmium sulfide was
utilized as the light-sensitive layer 22 and coated the
pipe to a thickness of 40~to prepare a light-sensitive mem-
ber. An electrostatic latent image 20 was formed thereon
in a conventional manner such as by uniform charging means
28 and image e~posing means 30 of Figure 2. Separate slots
of 0.1 mm. in pitch and 0.1 mm. in depth were formed on
the surface of an iron pipe of 40 mm. outside diameter to
thereby provide an ink-supply member 10. Liquid ink was
supplied to the slots formed on the ink-supply member.
After removing excess ink by a doctor blade 32, the ink-supply
member 10 was brought into substantial contact with the sur-
face of light-sensitive member 22 to effect development.
In this instance, it is not necessary to mechanically bring
the two members into contact with each other, but it is ,
sufficient to position them close enough to each other for
the liquid ink to move from one to the other. Thus, even
in the foregoing instance, the ink-supply member and the
light-sensitive member can be considered to be in "sub-
stantial contact" with one another for the purpose of this `~
specification and claims. Even when the members are not ;~
in physical contact, there is a high probability that the
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ink-supply member and the light-sensitive member will physi-
cally contact each other and thus damage the light-
sensitive mem~er. However, since an elastic support
member 24 is provided for the light-sensitive member 22,
no damage of the light sensitive member is observed and images
of high quality are formed on the photoconductive surface.
The ink-supply member lO may be replaced by one
which is prepared by winding an elastomer, which has electro-
conductivity at least at the surface layer, around an iron
pipe and having a fine uneven portion over the entire
surface on the elastomer. In this case, both the light-
sensitive member and the ink-supplying member possess
elasticity and damage to the light-sensitive member can be
further reduced.
Example 2
Silicone rubber having a Shore hardness of 75
and a resistivity of 1 x 103 ohm.cm was wound around an
aluminum pipe of 200 mm. outside diameter and 300 mm. width
in a thickness of 10 mm. Nickel (corresponding to
layer 26) was plated thereon in a thickness f 5h~ and
selenium was further vacuum deposited thereon in a thick- `
ness of 80~to prepare the light-sensitive member on which
an electrostatic latent image was formed in a conventional
manner. Thereafter, liquid ink was supplied to the ink slots
formed on the ink-supplying member made of iron pipe des-
cribed in Example 1, and this ink-supplying member was
brought into contact with the surface of the above-
described light-sensitive member. There was obtained a good ;~
image on the photoconductive surface without damaging the
selenium layer on the surface of the light-sensitive member.
Example 3
Silicone rubber having a Shore hardness of 75
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and electric reisitivity of 1 x 10 ohn.cm was wound around
an aluminum pipe of 200 mm. outside diameter and 300 mm. ~'
width in a thickness of 10 mm. Nickel was ~lated thereon in
a thickness of 5~ and a photoconductive surface of cadmium
sulfide was further coated thereon in a thickness of 40~to
prepare the light-sensitive member on which an electrostatic
latent image was formed in a usual manner. Thereafter,
liquid ink was supplied to the slots formed on the ink-
supply member made of iron pipe described in Example 1,
and this ink-supply member was brought into contact with
the surface of the above-described light-sensitive member.
There was obtained a more distinct image than in Example 1
without damaging the surface of the light-sensitive member
of cadmium sulfide.
Example 4
Urethane'rubber having a Shbre hardness o 75 -`
and electric resistivity of 1 x 103 ohm.cm was used instead
of the silicone rubber used in Example 1, and a photoconduc- ~
tive substance of cadmium sulfide was coated thereon in ~^
a thickness of 40~ to prepare the light-sensitive member,
to which liquid ink was applied by the same ink-supplying
member as described in Example 1. There was obtained the
same image quality as in Example 1 with no damage to the
photoconductive layer.
In all of the above-described Examples, image
quality can be stabilized by electrically grounding the
ink-supply member 10, and further a more improved image -
can be obtained by pressing, upon transferring at station ~ '
34, the transfer paper by a rubber roller 36. The above
operations can then be repeated at cleaning station 38. '
The liquid ink used in each of the foregoing '~
examples typically has a volume resistance of 1 x 105 to '~
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1 x 10 ohm.cm and a viscosity of from aibout lon ~ps. to . .
about 10,000 cps. and comprises a single phase. Examples of ,
thie composition are as follows: ..
(A) Polypropylene glycol (molecular ;. :-
weight: 1025) 60% by weight ~:~
Microlith* CT Black (predespersed .: .
carbon black, made by Ciba :-.
Limited) . 25% by weight ~
RucofleX* TG-8 (triethylene : :.
glycol aicaprilate, made by . ~ :.
Hooker Chemical Co.)15~ by weight .~
(B) Light liquid ~araffin45% hy weighit :.
Microlith* CT Black (same as . ,:
in (A)) 25% by weight ~ ~ :
Ganex* V-216 (alkylated ,~:
polyvinylpyrrolidone, made
by.C-eneral.Anyline25% by weight
Solid paraffin 5~ by weight
Numerous modifications of the invention will
become apparent to one of ordinary skill in the art upon .. :
reading the foregoing disclosure. During such a reading .
it will be evident that this invention provides a unique
apparatus and method utilizing wet-developing for accomplish- ~.
ing the objects and advantages hereinstated.
*trade marks
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