Note: Descriptions are shown in the official language in which they were submitted.
XC~
FJ51: _ ~10;:~7~ii 49
..: IMAGE FIXING IM ELECTl~OSl~ATOGT~ PHy
This in~ention.relates in general to electrostatographic
copying systems. The invention relates.more particularly to an .
, . . . .
improved method and material for fixîng a reproduced...image.to a
record medium in electrostatographic copying systems.
In one electrostatographic.copying.system, an electrosta-
tic latent image is established.on an image.retention.surface and
is de~eloped by passing.a.developer material ovex the surface.
Electrostatic.forces cause the..de~eloper material to adhere to the.
10 surface and to conform-to the..latent image. The image is then gen-
erally transferred to a.recordLmedium.for..recording.. .A permanent
. record is.established by.:fixing the.deve~oper material.which has
. been transferred in image co~figuration to.the.. record medium~
In the dry.or powder fonn o~.electros~tographic.develop-.
ing process,.particulate.development materials have been employedO
. . In general, these developer partic:les.. ar.e made up of a.thermoplas-
: . tic electroscopic resin.blended.wiith a.pi~ment.or dye.in order to
,,;; . ~
;. . impart a coloration.to:.the particles... .Images.which are developed
~ by the~e particles.. are fixed to.the.record medium or other substrate
.
.; 20 by sub~ecting them.to.heat.. or alternatively to solvent vapors.which
~ render the resin and the.toner particles su~fi~iently so~t and vis~
.:
COuS 50 that the substrate.becomes wetted and the developer parti-
.~: cles ~ecome firmly.. attached thereto.
, ~ .
. ~ ................ Solvent vapor fixing acts.more e~fectively.than.heat fix- :.
. : 25 ing. Kowever, it is accompanied by certain.disad~antages which
; .
. have led.to the relatively.widespread use of heat.fixing.. .For ex-
.:: ample, solvent vapor fumes,.which may be toxLc if the solvent con- .:
centration in the air 1s..suf.ficiently high, can escape into the .
~ atmosphere in offices or other business establishments where elec-
: . , .
trostatographic.copying apparatus îs.being utilized. On the other
hand, heat fixing although non-toxic, tends to unduly complicate the
: . electrostatographic reproduction apparatus especially where means
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` I for forming, developing and f~x:i~g an imaye are included in a sin-,
, gle apparatus. T~e heat generated ~ a ~ixing unit must be remo~ed
rom the machine in order to avoid damage to heat sensit~ve elements
in the apparatus such as amorphous selenium photoconductive plates
'i 5 which are used as image retention surfaces. Heat fixing also in-
: i troduces limitations with respect to the use oî toner resins which
.~ can be.employed in developing the electrostatic latent image. The
~ r~sins employed in manufacturing the toner must have melting points
'f~ which are low enough to facilitate heat fixing of the images~, This
, , . 10 requirement conflicts with certain desirable properties of the toner
, including the one that the toner particles will not agglomerate upon
. . subjection to mild hea~ing encountered with hot summer temperatures,
; , j . , .
' ¦ and that the resin be relatively tough and be able to withstand
,~ . mechanical handling in the apparatus without breaking up i~to ultra
~ 15. fine particles during handling o~ the.toners within the apparatus.
"`'! For these reasons various propo.sals have been made for
employing solvent toner fixing rather than heat fixing. These pro-
posals relate to.improved materials..or.reducing the hand}ing of
the,material and its accompanying agltation which previously had
~i, 2Q~ increased.the.pPssibility o~ dispersion o~ the ~apors into the at-
~,'',:'.~ ..' mosphere. In one arrangement which is described in U. S. Patent
3,080,250 a liquid solvent is encapsulated within a.hydrophylic
colloid material and this capsule is in turn encapsulated within a
; hydrophobic resin toner material. The capsules are handled~in the
. 25 sam~ ma~ner that particulate toner particles have heretofore been
~ .' . handled and the image is fixed on a sur~ace by crushing the capsules
E.,¦ ~ thereby releasing the encapsulated sol~ent for fixing the developer
~` ! material. While this arrangement has worked satisfactorily, it in-
,"l t-oduces several limitations with respec~ to ~he encapsulating toner
~:,1 - 30 material a~d additi~onalIy:restricts,the resolution.o~ the developed
image in.view o~.the size of. the encapsulated particl s.. Another
. ' .
arran~e~er~.t described i~ U. S. Patent.3,386,822 emplovs a record,
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medium havin~ deposited thereon a coatinq of encapsulated solyent
particles to which the toner image confi~uration is trans~erxea.
, The record medium is then transported ~etween rollars which rupture
! the encapsulated solvent.material causing the image to be fixed on
. 5 the record medium~ This arrangement suf~ers from the disadvantage
, . that a record medi~m bearing the necessary coating is reguired,
. thereby limiting the use~ulness of this concept.
. ~ccordingly, it is an object o~ this invention to provide
an improved method.for fixing an image in an electrostatographic
copying process. . . . . ..
, Another object of the invention is to provide an improved! toner material for developing and fixing electrostatic latent images
¦ in an electrostatographic copying apparatus.
. ~ A further object of the invention is to provida an im-
; 15 proved electrostatographic.recording process for ixing an image ;;
configuration which avoids one or more of the diisadvantages en-
coun~ered in the prior art arrangements.
I Another object o~ the invention is to provide an improvedil I , .
developing and fixing material having physical and chemical
properties superior to.those o~ known toner and developers.
. In accordance wi.th the general features Q~ this in~ention
.~ a method of electrostatographic recording comprises the steps.of ;:
~ orming an electrostatic latent image on an image retention surface, ~:
:, . developing the latent image by contacting the image with a toner :
~ 25 material comprising a mixture of toner particles and toner ~ixing
.
.. particles which consist o.a toner fixin~ 1uid conta.ined within
. ~ capsule body, and rupturing the capsule particles for releasing
.
: ~ the toner fixing material theraby fixing the image to the surface~ .~
., .
I~ accordance with other features o~ the in~ention, a
` 30 ;toner ma~erial for an electrostato~raphic copying process com-
. prises a mixture of~toner particlPs and toner fîxing particles, the
.. toner fixing particles consisting o~ a toner ~ixing 'luid contained .
. in a capsule body.~
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These and ~er o~ ects an~ features of the invention
will become apparent with references to t~e ~ollowing specification.
and the drawings wherein:
~i Figures lA-lE are schema~îc representations of the steps
i 5 employed for practicing the process of this invention;
¦ Figure 2 is a sectional view of a toner fixing particle
. component of a toner material mixture of this invention; and,
. Figure 3 is.a schematic representation of an automated n-
'. . apparatus for practicing the process of this invention.
! lo -A electrostatic latent image is formed in an electro-
statogxaphic apparatus by.establishing a uniform surface charge on
l an image retention surface and b~ altering the uniform charge to
¦ . provide an image configuration. .Figure lA illustrates an electro-
statographic plate assembly.9 Which includes a substrate body 1
formed of an electrically conductive material such as stainless
.1 : .
~ steel and an image retention thin layered surface 12 supported on
.~ . the body 10. The surface 12 comprises ~or example a photoconductiYe
¦ insulating layer such as.amorphous selenium~ The pIate assembly:~
~, ~ is positioned at;'an;electrostatic.charging~station 13 beneath a
~, ` 20 corotron 14 which includes an inner..rod I6 to ~hich a relatively
: high DC potential is applied from a.source 18. As is.well known,
`I . ~ .
~, ~ the corotron establ~ishes.. a u~iform elect~ic charge on the photocon-
: ductive surface 12. . :
he plate assembly 9 bearing a uni~orm electrostatic
,~ .
` 25 charge is then t~ansported to an imaging station 19 illustrated in
. Figure lB. At the imaging station, the photoconductive surface 12
., .
j . is positioned beneath.a ~ransparent plate 20.which supp~rts an image
~ ! transparençy 22 which is~to be repxoduced. The surface 12 lS ex~
i posed to Lhe image.22`by light from a source 24 which is focused on:
.1 30 ~he surface 12 by.a lens 26~ Lîght which is incident on the photo-
conductive surface..l2 will discharge electrîc charge on portions of
. the surface 12 to provide.a x sultant electrostatic latent image~ -
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The plate 9 bearing an electrostatic latent i~age is then transported
to a development station.27, illustrated in Figure 1 C at w~ich
station a developing material 28 which is contained in a s~orage
; hopper 3a flows from the hopper.onto the conductive surface 12 as
the plate is drawn beneath the hopper. In accordance with the fea-
tures of this invention, the developin~ material 28 includes a
toner material comprising a mixture of toner particles and particles
which consist of a fluid toner fixing material 31 contained within
a thin wall capsule body 32 tFigure 2~. This material is described
in greater detail hereinafter. In a cascade developing arrangement,
the developing material would additionally include well known
carrier particles and can.include other additives such as a non-
. agglomerative; The developin~ material exhibits triboelectric
characteristics whereby a charge is established on the toner
. 15 material which~is of a polarity opposite ~D the polarity of the
charge of the latent image which has been establishèd on the image
.l retention sur~ace 12. The.toner material.will therefore adhere to
the image retention surface in accordance with the image configuration
. . and will provide a developed image.
. 20 The developed image is ~enerally, although not necessar-
.. ~ . . .
ily, transferred to another surface such as a record medium for per-
` manent recording. After.. development, the plate 9 is transported to
. . an image transfer station 33 as shown in Figure lD. A sheet of
.. . paper 34 or other suitable transfer record medium is placed on the
., ~ .
.. . 25 photoconductive surface and ~he de~eloped image configuration is
transferred to this sheet by establishing.a charge.on a~ opposite
. surface of this sheet 34.. .The charge is established by.a corotron : ;
. 35 to which is applied a.DC potential from a source.36.. ~lterna-
tively~ ~he image may.be transferred by pressure contact between
the sheet 34 and image retention surface..
.~ , . .
Upon completion of t.he ~rans~er st.ep-, a deYeloped.image on
the transfer sheet 34 will be formed by toner particles and the
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encapsulated fixing liquid. I~ order to fix the i~age to this shee~
34, the s~eet is transported to a ~ix~ng station 37 and passed
beneath a pressure roller 38 which applies to the sheet a force o~
sufficient magnitude for rupturing the walls of the capsules 32
containing the fixin~j fluid. The fixing fluid thus released then
operates to fix the toner particles to the sheet 34 and pro~ides a
permanent record.
The toner material employed in accordance with this
invention is a mixture comprlsing toner particles and toner fixing
particles. The toner particles generally comprise a colorant such
as a dye or an organic or inorganic pigment dispersed in a resin
binder. The colorant is present in the tone~ in amounts of about
5 to about 20~ by weight of the toner depending upon the desired
intensity of coloratio~. When the fixing fluid comprises a solvent,
lS the toner will include as one of îts components an electroscopic
material which is soluble or at least partially soluble in the
sol~ent and which will wet and adhere to the imaging web when
subject to the solvent action. The soluble component of the toner
is its major component and will in most instances constitute from
about 80~ to about 95~ o tne weight of the toner. By way of
example, the electroscopic soluble component of the tonPr may
consist of gum copal, sealing wax, coumarone-indene resinr polystyrene,
- rosin modified phenol-formaldehyde, or plasticized copolymers of
methacrylic esters and styrene:as descri~ed for example in U. S.
Patents: ~E~ 25,136; 2,297,691; 2,659,67Q; and 3,079,342 as well as
a great number of the natural, modi~ied natural and synthetic
xesins. The toner particles will generally range from submicron
size up to about 50 microns in diameter ~or best results with the
particular size selected dependent ~or the most part upon the
electrostatographic system in wh~ch it is employed.
~ he tonex fixing particles comprise a fluld ehcapsulate~
by a body of material. The fixing fluid comprises, ~or example, a
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volatile toner solyent such as Freon 113 ~luorinated h~drocarbon
solvent, xy'ene, toluene, acetone, chloroform, or perchlorethylene
or a non-volatiie solvent whic~ behaves as a plasticizer such as '
dioctyl phthalate, N-methyl sulfonamide, or diethyl phthalate. The
fixing fluid is encapsulated in a body o~ a natural or synthetic '
. .
polymeric material which is insoluble in the toner fixing solvent.
The choice of pol~mer wall material for the capsule body depends on
the solubility characteristics of the toner fixing sol~ent which in
turn are dependent upon the solubility of the toner. The toner fix-
ing solvent is a solvent which will freely dissolve the polymericcomponent of the toner particles. For example, if the~toner polymer
is a polymer o~ styrene'such as copolymer of styrene and n-butyl
methacrylate, then any one of ~he a~orementioned group of solvents
can be mployed since they are capable of rapidly dissolving styxene
,
polymers. The polymer which is employecl to form the wall of the
capsule must be insoluble in the solvent: in order that the capsule
exhibit the desirable characteristics oi' stability during storage`
prior to use and nonagglomeration. ~hen any of the aforementioned
solvents is employed, suitable wall ~orming polymeric materials are
nonsolvent soluble polymers suah as gelatin, dialkyd type made for
example by reacting a difunctional acid or anhydride such as phthalic,
- isophthalic~ terephthalic, malic, maleic, citric, succinic, glutaric,
adipic, tartaric, pimelic, suberic, azelaic, sebacic, or camphoric
with a polyol such as glycerin, et~ylene glycol, propylene gl~col, '~
sorbitol, mannitol, pentaerythritol, diethylenè glycol or polyethylene`''~
glycol. The epoxies made for example by condensing epichlorohydrin '~;
with any one of the bisphenol A, resorcinol, hydroquinone, e.hylene ~;-
glycol, glycerol, or other hydroxyl containing compounds, and the
'' polyurethanes prepared, for examp~e, by reac~ing a diisocyanate
such as toluene-2,4-diisocyana~e ~ethylene ~is t4-PhenYliSocyanate~,
bitalylene diisocyanate, 1,5 r.apthalene diisocyanate, and hexa
methylene diisocyanate with a poly~ydroxy c~pound, ;~
* Trademark
~7s~g
In general it is desirable that the encapsulated toner
fixing particles exhibit develop~ent characteristics in a
xerographic system similar to those exhi~îted by the toner parti-
cles relative to the xerographic plate or carrier materials i~
carrier materials are utilized. More particularly, it is
desirable that the toner fixing particle exhibit the same charge
polarity relative to the plate charge or the toner particles so
that the developed image has sufficient toner to satisfy the image
density requirements and sufficient fixing fluid to satisfy the
toner fixing requirements. It is also desirable that the encap-
sulated fixing particles exhibit stable storage characteristics
and be nonagglomerative as indicated hereinbefore.
The thickness of thè capsule wall is selected to provide .
su~ficient wall strength so as to inhibit rupturing of the capsule .
during ordinary handling and to avoid agglomèration of the parti-
. cles. On the okher hand, the part:icle size which is desirably inthe micron range limits the overalL size of the particle and the
. quantity of solvent which is contained in any particle. Thus, the
. thickness of the wall is determined in part on the provision o~ a
sufficient qua~tity of solvent to provide proper fixing of the
toner material. ~he proportions of the materials of a toner fixing
par~icle are l0~ to about 75% by weisht of wall material and 90~ to
: `abou~ 25~ by weight of toner fixing solvent material. The encap-
sulated fixing material has a particle size on the order of 5 to
~5 40 microns for example.
The encapsulated toner fixing particles can be manufac-
. tured by various methods. The.capsules may be formed, for ex.ample,
- by extruding the solvent core and the shell ~aterial through coaxial- ;
tubes rotating in the head of a spray drying unit. Additional
30 techniques for forming encapsulated solvents are disclosed in U. S.
Patents 2,800!457 and 2,800,458 to Green ~nd 2,96~,330 and 2,969,331
- to Brynko. The Green patents describe encapsulation o~ the solvents
. . .
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~ )3754~9
in a h~drophilic collold mat~rial and generall~ may be.employed to
encapsulate.any ~ater immiscible solyent which is less than a~out
1% soluble in water including for example, kerosene, xylene,
chlorinated diphenyls such as trichlorodiphenyl and the like. The
Brynko patent describes encapsulation o~ these solvents in a cross-
. linked synthetic polymer sucn as a cross-linked polystyrene and
because of this fact it can retain some solvents which might tend
to attack the hydrophilic colloid capsule shell described in the
Green patents~ Techniques for encapsulating solvent with condensa-
- 10 tion polymers such as urea formaldehyde resins are also known in
the art and may be employed.
An automated electrostatographic apparatus for practicing
.
the method of this invention is illustrated in Figure 3. This
apparatus includes a cylindrical drum 42 mounted for rotation.about
a horizontal axis 43. Drum 42 supports a substrate 44 and an image
retention sur~ace 46. By way of example, the substrate layer
consists of an electrically grounded layer of a conductive metal
such as aluminum while the image retention surface 46 consists for
example of a photoconductive layer of amorp~ous selenium. As the
20 drum 42 ro ates in the direction indicated by the arrowj the ima~e
~etention surface is initially uniformly charged so as to sensitize
it to light exposure. This is accomplished with a corotr~n charg-
ing unit 47 which is connected to a source of DC potential 48. ~he
charging unit 47 contains one or more wire filaments which are
. 25 connected to the potential source and operate on the well known
. corona discharge technique. As the drum 42 rotates at a uniform
velocity, it passes beneath a projector 49 or other means for
exposing the charged surface 46 with light or other electromagnetic ~
radiation to an image which is t~ be reproduced. This exposure .-
step serves to dissipate charge ~rom those areas of the image
retention surface which have been exposed to light thereby resulting
in a residual charge pattern on the plate corresponding to the
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image to be reproduced. The drum then rotates past a deyeloping
unit designated generall~ as 51. This dey~loping unit.is of the
cascade type which includes an outer container ox cover 52 wikh a
resexvoir located at a lower portion thereof containing a supply
o~ developing material 53. This developing material includes a
toner material comprising a ~ixture of toner particles and toner
fixing particles which consist of an encapsulated fixing fluid.
The developing material.is removed ~rom the reservoir and is
. dumped or cascaded over the Lmage retention surface 46 by a
.. 10 number o buckets 54 which are mounted on a driven, endless
conveyer.belt 56. This developing technique additionally includes
a plurality of.relatively larger carrier beads. The carrier beads
serve both to deagglomerate the toner particles and toner fixing
particles and to charge them and the toner fixing particles.
Changing occurs by virtue of the rubbing together of the particles
and the carrier bead in the apparatus. Upon development of ~he .
residual charge pattern on the ima~e retention surace 46, the
drum bearing this developed particulate image rotates until it
I . . . .
comes into contact with a copy web 57 which:is pressed against
the image retention surface by two idle.rollers 58 and 59 in a
manner or providing that the web moves at.the.same speed as the
.periphery of.the drum. ~ transer unit 61 is placed behind the
web and.spaced slightly from it between.the rollers 58 and 59. This
- - unit is similar in nature to the plate.charging mechanism 47 and
25 operates on the corona discharge principle~ The.transfer unit is : :
.~ connected to a source of high potential 62 of the same polarity
as that employed in.the charging unit 47 thereby providing that .
the deposited charge on the back o the web 57 is opposite in
. .
polarity to the charge on the toner particles utili2ed in developing
~he image. Upon:transfer of the toner in image configuration to
tne web 57, the web is separated from contact with the surface 46
and the drum continues in its rotation pass.ing a cleaning brush 67
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which pre~ares it ror another cycle of operation while the web
passes between two pressure rollers 64 and 66 which serve to
rupture the toner fixing capsules. The rupturing of these cap~
sules -eleases the fixing material and causes softening of the
toner particles, coalescence of a number of particles and ad-
herence of the particle to the transfer web 57 and fixing of the
image on the web.
~ he following illustrative examples are given to enable
those s~illed in the art to more clearly understand the practice
of the invention.
Examp]e 1
. '. . ' .
~ A toner material is formed of a mix.ure of about 90% by
weight of toner particles and about 10% by weight of encapsulated
toner fixing particles. The toner particles comprise about 70%
by weight of styrene-isobutyl mathacrylate copolymer, about 20% , -
by weight of pentaerythitol tetrabenzoate, and about 10% carbon
blac~. The encapsulated toner matexial comprise perchlorethylene
solvent encapsulated in a protein base gelatin available from the
National Cash Register Company. The encapsulated toner particles
:
are in the size range of about 10-40 microns. This toner material ;
~ ~ mixture is combined with carrier particles comprisins steel par-
-~ ticles of about 250 micron diameter coated with a terpolymer com-
prising styrene, methyl methacrylate and vinyltriethoxysilane.
~I The carrier particles and toner material are combined in a mix
! 25 ture of about 9~/O to 99.7% by weight of carrier particle or
about 1% to about 0.3% by weight of toner material. An electro-
static latent image is formed on a flat selenium plate of a model.
l A xerographic device and the above developer material is flowed -
`~ ~ onto the electrosta~ic latent image in order to develop the
I 30 image.~ A developed image configuration is passed beneath a three
.
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~ C~3'17S~9
inch diameter steel roller ~hic~ is loaded at 200 pounds.per linear
inch at 1~ inches per second to provide a useful ~ixed Lmaye. It
is found that the Xerox 66Q toner ~y itsel~ easlly rubs of~ the
paper under similar conditions.
Example 2
: The above example is repeated and the percentage by
weight of encapsulated toner fixing particles to the toner
particles is about 50% - 50%. Again, a useful fixed image is
provided.
Example 3
. The steps of Example number 1 are repeated in which case
a carrier material of 450 micron diameter.glass beads were employèd
in place of the coated steel capsules o~ Example.l. The carrier
particles and developer material axe combined in a rnixture of ::
about 99% to about 99.7% by ~eight of carrier particles and about
1~ to about .3% by weight of de~eloper material. A use~ul fixed .
imagè`is provided by this exampleO ~ :
Example 4
,
: The steps of Example number 2 are repeated with the
~20 ~xception that the coated steel beads o~ Example number 2 are . `
replaced by 45Q micron diameter glass carrier beads as indicated
in Example 3. A use~ul ixed image is thereby provided. :
- There has thus been described an improved process and :
material for fixing a developed image in an electrostatographic
25 reproduction system~ ~
While there has been illustrated and described particular -. :
:. embodLments of the invention, it will be understood that various
modifications.may.be made.therein without departing from the.
spirit of the invention and the scope o the ~ppended claims.
~hese.are intended.to be.included within the scop of this invention~ ~ .
* Trademar~ . .
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