Fixing method using polyarylsiloxanes as release agents

Polyarylsiloxanes are used on fusing devices in photocopiers to fix particulate thermoplastic toner to a substrate while the toner is in a fused state. The polyarylsiloxanes can be continuously applied in minimal thicknesses on the fusing device to form a thermally stable, renewable, self-cleaning layer having excellent toner release properties. A preferred polyarylsiloxane is polyphenylmethyl dimethyl siloxane.

BACKGROUND OF THE DISCLOSURE 
This invention relates generally to xerographic copying methods and 
apparatus, and more particularly, it relates to the fixing of particulate 
thermoplastic toner by direct contact with the surface of a fusing member 
having a novel fluid release surface. 
In the process of xerography, a light image of an original to be copied is 
typically recorded in the form of a latent electrostatic image upon a 
photosensitive member with subsequent rendering of the latent image 
visible by the application of electroscopic marking particles, commonly 
referred to as toner. The visual toner image can be either fixed directly 
upon the photosensitve member or transferred from the member to another 
support, such as a sheet of plain paper, with subsequent affixing of the 
image thereto. 
In order to affix or fuse electroscopic toner material onto a support 
member permanently by heat, it is necessary to elevate the temperature of 
the toner material to a point at which the constituents of the toner 
material coalesce and become tacky. This action causes the toner to flow 
to some extent into the fibers or pores of support members or otherwise 
upon the surfaces thereof. Thereafter, as the toner material cools, 
solidification of the toner material occurs causing the toner material to 
be bonded firmly to the support member. In both the xerographic as well as 
the electrographic recording arts, the use of thermal energy for fixing 
toner images onto a support member is old and well known. 
One approach to thermal fusing of electroscopic toner images onto a support 
has been to pass the support with the toner images thereon between a pair 
of opposed roller members, at least one of which is internally heated. 
During operation of a fusing system of this type, the support member to 
which the toner images are electrostatically adhered is moved through the 
nip formed between the rolls with the toner image contacting the fuser 
roll thereby to affect heating of the toner images within the nip. By 
controlling the heat transferred to the toner, virtually no offset of the 
toner particles from the copy sheet to the fuser roll is experienced under 
normal conditions. This is because the heat applied to the surface of the 
roller is insufficient to raise the temperature of the surface of the 
roller above the "hot offset" temperature of the toner at which 
temperature the toner particles in the image areas of the toner liquify 
and cause a splitting action in the molten toner resulting in "hot 
offset". Splitting occurs when the cohesive forces holding the viscous 
toner mass together are less than the adhesive forces tending to offset it 
to a contacting surface such as a fuser roll. 
Occasionally, however, toner particles will be offset to the fuser roll by 
an insufficient application of heat to the surface thereof (i.e. "cold" 
offsetting); by imperfections in the properties of the surface of the 
roll; or by the toner particles insufficiently adhering to the copy sheet 
by the electrostatic forces which normally hold them. In such a case, 
toner particles may be transferred to the surface of the fuser roll with 
subsequent transfer to the backup roll during periods of a time when no 
copy paper is in the nip. 
Moreover, toner particles can be picked up by the fuser and/or backup roll 
during fusing of duplex copies or simply from the surroundings of the 
reproducing apparatus. 
One arrangement for minimizing the foregoing problems, particularly that 
which is commonly referred to as "offsetting", has been to provide a fuser 
roll with an outer surface or covering of polytetrafluoroethylene, known 
by the trade name "Teflon" to which a release agent such as silicone oil 
is applied, the thickness of the Teflon being on the order of several mils 
and the thickness of the oil being less than 1 micron. Silicone oil, 
polydimethylsiloxane, which possesses a relatively low surface energy, has 
been found to be a material that is suitable for use in the heated fuser 
roll environment where Teflon constitutes the outer surface of the fuser 
roll. In practice, a thin layer of silicone oil is applied to the surface 
of the heated roll to form an interface between the roll surface and the 
toner images carried on the support material. Thus, a low surface energy 
layer is presented to the toner as it passes through the fuser nip and 
thereby prevents toner from offsetting to the fuser roll surface. 
A fuser roll construction of the type described above is fabricated by 
applying in any suitable manner a solid layer of abhesive material to a 
rigid core or substrate, such as the solid Teflon outer surface or 
covering of the aforementioned arrangement. The resulting roll structure 
is subject to wear and degradation due to continued operation at elevated 
temperatures and also to damage from accidental gouging by stripper 
fingers conventionally employed in such systems. The foregoing, in many 
instances, necessitates replacement of the fuser roll which is quite 
costly when a large number of machines is involved. 
Moreover, the polytetrafluoroethylene along with the coating of silicone 
oil is of sufficient thickness to constitute a poor thermal conductor, and 
longer nip dwell and higher fuser roll temperatures are required to 
deliver the fusing energy required to fix toner. Also, control of the 
surface temperature of the roll presents a problem due to large 
temperature variations occurring before and after contacting of the 
substrate carrying the images. 
Silicone elastomers have also been used on the surface of fuser members for 
fixing thermoplastic toners on receptor surfaces. In U.S. Pat. No. 
3,669,707 issued June 13, 1972, silicone elastomers containing fluorinated 
organic polymer fillers of specified surface energy are used on the 
surface of fuser members for fixing toner materials. However, the coating 
is of sufficient thickness to constitute a poor thermal conductor, and 
longer nip dwell and higher fuse roll temperatures are required as in the 
case described above. Furthermore, the silicone gum filler is, of 
necessity, a dual component system to prevent hot offset. This in turn 
leads to additional preparation and handling problems. 
In view of the foregoing it would appear that the high thermal conductivity 
and wear resistance of bare metals or similar materials would be desirable 
for utilization in fuser member structures and certain materials have been 
found which are satisfactory for such application. Commonly used release 
agents such as pure silicone oils and mineral oils, have been tried in 
combination with various metals and other high surface energy materials 
but with relatively little or no success. However, certain materials have 
been found which are satisfactory for such application. These materials, 
fusing methods and devices are described in Assignee's co-pending patent 
application Ser. No. 383,231 filed July 27, 1973, now U.S. Pat. No. 
3,937,637 which includes providing a coating of a polymer release material 
of the type which oxidizes and thereafter is capable of reacting with the 
fuser surface material to form a first barrier coating portion upon the 
fuser member and a second replenishing release portion thereon. In 
Assignee's copending application Ser. No. 419,415 filed July 24, 1974, a 
coating of polymeric fluid containing built-in functional groups which 
interact with the fuser member surface to provide an interfacial barrier 
layer and a low surface energy film of the fluid, is provided upon a fuser 
member. Exemplary of the built-in functional groups in the foregoing 
reference are carboxy, hydroxy, epoxy, amino, isocyanate, thioether and 
mercapto. Polyalkylsiloxane fluids have also been successfully used on 
bare metal fuser members as described and claimed in a co-pending patent 
application assigned to the same assignee and filed herewith. 
OBJECTS OF THE INVENTION 
It is the principal object of this invention to provide a new and improved 
fusing process and device for use in fixing toner images. 
Another object of this invention is to provide, for use in a photocopying 
apparatus and process, a fusing process, device and release agent wherein 
the fuser member has a continuously renewable surface. 
Another object of this invention is to provide a fusing process and device 
wherein toner is displaced from the exposed surface of the fuser member by 
the action of a release agent on the surface of the fuser member, the 
release agent having a polysiloxane backbone with aryl or substituted aryl 
groups thereon. 
Still another object of this invention is to provide a fusing process, 
device and release agent wherein an interfacial barrier is formed 
intermediate the fuser member surface and the fluid release layer applied 
thereto. 
Another object of this invention is to provide a fusing device and process 
for toner images wherein a barrier is formed during operation of the fuser 
at the interface of the fuser roll surface and a release agent through 
interaction between the fluid release agent and the fuser roll material. 
Still another object of this invention is to provide a new and improved 
release agent, device and method for fusing toner images to a substrate 
wherein toner barrier and toner release coatings are formed on a thermally 
conductive core and wherein the combined thickness of the coatings is 
insufficient to establish an appreciable thermal barrier to the energy 
being conducted through the core, thereby lowering the power requirements 
for maintaining a heated core and for the overall fusing operation. 
Other objects and advantages of the present invention will become apparent 
when read in conjunction with the accompanying drawings and specification. 
SUMMARY OF THE INVENTION 
The above-cited objects of the present invention are accomplished by 
applying polyarylsiloxane (polydimethylsiloxane polymers having methyl 
groups replaced by aryl or substituted aryl groups) to a heated fuser 
member in an electrostatic reproducing apparatus. The aryl groups of the 
polyarylsiloxane, said aryl groups or substituted aryl aryl groups being 
attached to the silicon atoms, must comprise at least about 0.5 aryl group 
or at least about 0.5 substituted aryl group per polymer molecule capable 
of interaction with the fuser member surface and thereby provide a 
thermally stable interfacial barrier to the toner. The polysiloxane may 
also comprise a mixture of aryl and substituted aryl groups. 
The polyarylsiloxane is applied in an amount sufficient to cover the 
surface of the fuser member with at least a continuous, low surface energy 
film of polyarylsiloxane to provide the fuser member with a surface which 
releases toner heated by the fuser member and prevents said toner from 
contacting the surface of the fuser member. The polyarylsiloxane must be 
capable of interacting with the fuser member surface to form a 
thermally-stable barrier to toner, said barrier designated herein as an 
interfacial layer, which strongly adheres to the metal, glass or other 
substrate of the fuser member and provides a thin coating which has 
excellent release properties for the toners used in electrostatic 
printing. The polysiloxanes containing substituent aryl and/or haloaryl 
groups are preferred for the method and device of the present invention 
and include phenyl and chlorophenyl groups. 
The polyarylsiloxanes may be applied to the surface of the fuser member in 
thicknesses ranging from submicron to several microns to constitute a 
minimal barrier to heat transfer. By employing the polyarylsiloxane fluid 
release agent and process of this invention there is provided a fuser 
member having a surface surrounded only by a minute layer of material 
which prevents toner from contacting the surface. 
While the mechanism is not completely understood, it is believed that when 
this class of polyarylsiloxane fluids having at least about 0.5 aryl or 
substituted aryl group per polymer molecule are applied to the surface of 
a fuser device, there is an interaction (a chemical or physical reaction, 
e.g., chemisorption, hydrogen bonding or other mechanism) between the 
metal or glass surface of the fuser member and the polyarylsiloxane, so 
that an interfacial barrier layer comprising the interaction product 
between the metal, glass or other material of the fuser members and the 
aryl groups of the polyarylsiloxane forms a barrier layer intermediate the 
metal or glass or other substrate of the fuser member and the outer layer 
of polyarylsiloxane coating the fuser member. This outer layer may be 
referred to as the non-reacted release layer, or generally, the release 
layer. The coating, however formed, has been observed to have a greater 
affinity for the fuser substrate material than the toner and thereby 
prevents electroscopic toners from contacting the core, while the release 
coating provides a material, the cohesive force of which is less than the 
adhesive forces between the heated toner and the substrate to which it is 
applied, and the cohesive forces of the toner. Not only do these coatings 
or films have excellent release properties, but it has also been observed 
that the thermally-stable layer is continuously renewable and 
self-repairing. That is to say, if this coating is damaged, for example, 
by uneven pressures exerted by the blade utilized for metering the release 
material to the core, or by undue forces exerted by the finger employed 
for stripping the substrate from the fuser roll structure, the 
thermally-stable coating will repair itself. 
The foregoing ability of this class of polyarylsiloxanes to form a 
thermally stable, renewable, self-cleaning layer or layers having 
excellent toner release properties is surprising in view of the prior art 
disclosures which affirm the stability of these compounds. In a report by 
Willis and Shaw in Journal of Colloid and Interface Science, Vol. 31, No. 
3, November 1969, pp. 397-408, directed to the thermal oxidative 
decomposition of polyorganosiloxane fluids at metal surfaces, it is 
reported that the thermal oxidative stability of the polyorganosiloxane 
fluids is dependent on the nature of the substituent organic radicals, and 
that in this respect, the methyl- and, to a somewhat greater extent, the 
phenyl-derivatives are particularly stable. 
However, in accordance with this invention, toner of the type commonly used 
in electrostatic printing is displaced from damaged or worn areas which 
interrupt the coatings on the heated fuser member when polyarylsiloxanes 
as above described, are used as release agents or materials on fuser 
members. The softened or tacky toner is substantially removed by the 
polyarylsiloxane, and the interrupted, damaged or worn area is repaired by 
newly metered or applied polyarylsiloxane without entrainment of excessive 
levels of toner which would ordinarily print out or transfer to successive 
substrates. This mechanism has substantially reduced offset problems 
common to the devices and processes of the prior art. 
Generally, the polysiloxanes having aryl or aryl substituted groups are 
applied to fuser members as fluids and by using the term "fluid" in 
describing the coating materials or release fluids of this invention is 
meant the state which the polyarylsiloxane material assumes at operating 
temperatures. 
By use of the phrase "capable of displacing electroscopic toner" as used 
herein, is meant that the polyarylsiloxane fluid substantially prevents 
the toner from contacting the surface of the fuser member and is more 
reactive than the toner with the material of the fuser member surface to 
the extent that it repels or displaces the toner from the surface of the 
fuser member even when the surface thereof is exposed to or contacts the 
toner.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The polysiloxanes capable of releasing electroscopic toners are operable in 
accordance with the present invention only when the appropriate aryl or 
substituted aryl group or groups or combinations thereof are present on 
the backbone of the polysiloxane and substituted on the silicon atoms. The 
polyarylsiloxanes preferably form an interfacial barrier between the 
metal, glass or other material of the fuser member and the outer fluid 
layer of the same release material. In accordance with the present 
invention, this characteristic is found in polyarylsiloxane fluids which 
have at least about 0.5 aryl or substituted aryl groups per polymer 
molecule. 
The specific polyarylsiloxane fluids of the present invention have a 
polymeric backbone of the general formula: 
##STR1## 
where n is an appropriate number such that the polymeric material assumes 
a fluid state (liquid) at operating temperatures which are generally from 
about 200.degree. F (93.degree. C) to about 450.degree. F (232.degree. C); 
where at least one R in the molecule is an aryl group or a substituted 
aryl group and the remaining R constituents are alkyl having one or more 
carbon atoms and mixtures thereof and preferably methyl groups. More than 
one R in the molecule may be aryl groups, substituted aryl groups or 
combinations thereof. For example, one R in the molecule may be a phenyl 
group and the remaining R groups may be methyl groups, or for example, in 
another embodiment one R in the molecule may be a phenyl group and the 
other R may be a chlorophenyl group. Thus, all R's in the molecule may be 
the same, or they may be mixtures of aryl groups and substituted aryl 
groups. Furthermore, the R's may also comprise other substituents, for 
example, alkyl groups and halogenated alkyls and the like, and even 
substituted nonreactive inorganic substituents substituted on the silicon 
atom as long as there is the critical aryl or substituted aryl, said aryl 
being capable of interacting with the material of the fuser member surface 
to provide a thermally stable interfacial barrier layer to electroscopic 
toner. 
A preferred class of polyarylsiloxanes useful as release agents in 
accordance with the present invention are the polymethylphenyl dimethyl 
siloxanes, the molecular structure of which may be designated as: 
##STR2## 
where m is at least 1, n is at least 1 and X is halogen or hydrogen. A 
particularly useful polyphenylsiloxane fluid is polyphenylmethylsiloxane 
where m=0.5-1.0, n=6-8, and X is hydrogen. Where m=less than 1.0, then all 
siloxane molecules do not have the structure represented within the 
brackets designated "m". Generally, those polyphenylsiloxanes with chain 
length where m + n is equal to less than about 20 are liquid at room 
temperature, and are useful in accordance with the present invention, 
however, as explained supra, as long as the polysiloxane is fluid or 
liquid at operating temperatures, it is useful herein. Where the alkyl 
substitution on the silicon atom comprises 2 or more carbon atoms and 
combinations thereof and/or other non-reactive substituted groups the 
fluid nature of the polymer is dependent upon such substitution, and 
appropriate polyarylsiloxanes for use as release agents on fuser members 
can be chosen according to the fluid state of the polysiloxane at 
operating temperatures. 
Representative examples of aryl and substituted aryl groups in the 
polyarylsiloxanes of the present invention, are phenyl, biphenyl, 
chlorophenyl, dichlorophenyl, trichlorophenyl, mono-, di-, and tri-nitro 
phenyl, bromophenyl, iodophenyl, naththyl, anthranyl, chloronaphthyl, 
pyrenyl and the like and combinations thereof. As indicated supra, 
preferred polyarylsiloxane release materials have at least about 0.5 aryl 
groups, substituted aryl groups or a combination of said groups per 
siloxane molecule. For example, in the preceding molecular structure for a 
polyphenylmethyl dimethyl siloxane, the molecular structure comprises at 
least about 0.5 phenyl groups, substituted groups or combinations thereof. 
Alternatively stated, this preferred class of polyarylsiloxane release 
materials are the polyarylmethyl dimethyl siloxanes having at least about 
0.5 methyl groups per single polymer chain to at least about 1.0 methyl 
group per two polymer chains substituted by an aryl or aryl substituted 
group. The only limitation is that the polyarylsiloxane be fluid at 
operating temperatures and capable of interacting with the fuser member 
surface at least at such operating temperatures. As used herein, 
polyarylsiloxane or aryl polysiloxane are used interchangeably and include 
all of the substituted forms suggested above. 
It is to be considered within the purview of one skilled in the art of 
manufacturing polyarylsiloxanes to provide the release fluids of the 
present invention. For example, methods of making such fluids are 
described by Kirk-Othmer "Encyclopedia of Chemical Technology", 
Interscience Publishers, volume 18, p.p. 237-241 (1969) where it is 
suggested that phenyl substituents are added as [Ph.sub.2 SiO].sub.n or 
[MePhSiO].sub.n. 
In order to provide suitable release of toner when bare fuser rolls are 
used in the process and device of the present invention, the 
polyarylsiloxane release agents preferably have the following properties 
either before, during or after application to the fuser member surface. 
The polyarylsiloxane release agents are preferably nonvolatile, that is, 
they do not produce excessive levels of volatile fumes and vapors which 
penetrate the surrounding atmosphere and thereby cause deposits upon 
surrounding parts in the copying apparatus or fumes which are toxic, in 
the environment. The release material upon the fuser member should be 
thermally stable, that is the fluid must not form a gel or decompose at 
operating temperatures over reasonable periods of time, for example, at 
least about 200 hours at operating temperature. This is dependent upon the 
particular machine and machine use. The fluid is preferably noncorrosive 
to the machine parts and to the paper, and nonreactive, that is, inert, to 
the toner used in the development of the electrostatic latent image. 
During operation the polyarylsiloxane fluid must present a low energy 
surface to the toner which is undergoing fusing by heat, that is, it must 
be abhesive, and the surface energy must be less than the surface energy 
of the molten or heated toner. For example, a conventional toner has a 
room temperature surface energy of about 28-36 dynes/cm, and the fluid 
must have a surface energy less than that of the toner. The interfacial 
layer is preferably impenetrable to the toner, that is, electroscopic 
toner applied to the fuser member and softened should not be able to 
penetrate the intact interfacial barrier layer so that the fuser member 
surface will be exposed to toner particles which may become entrapped 
within the layers upon the member. The fluids must be capable of 
application to the fuser member in minute thicknesses preferably of the 
order of magnitude of 10 microns or less so that only a minimum thermal 
barrier will be coated upon the bare fuser member. It is also preferred 
that any interfacial layer which forms a barrier between the fuser member 
surface and the outer release layer remain insoluble in the non-volatile 
fluid release layer even at the operating temperatures of the device. 
Generally, the modes in which the release agents of the present invention 
are utilized are those wherein the coating can be continuously applied to 
the surface of the fuser member, and accordingly, the coating is deemed 
self-renewing in these cases. The polyarylsiloxane may be applied to the 
fuser member by any of the standard or conventional methods or devices 
known to those skilled in the art, and includes application by brushes, by 
spraying, by metering from a sump, by application from a wiper blade or 
wiper comprising the polyarylsiloxane, by applying from a suitable sump, 
by applying from a wick, by padding, and the like. In general, one skilled 
in the art will be able to use this invention in the fuser assembly of a 
copying device wherein thermoplastic resin toner applied to a substrate in 
image configration must be heated or fused in order to fix permanently the 
colored substance in image configuration upon the substrate. The 
polyarylsiloxane release material may also be applied in the form of a 
solid which becomes fluid at operating temperatures, for example, a block 
of the polymer or elastomer may rub against the heated fuser member to 
apply a fluid film on the fuser member. The release agent may also be 
applied in conjunction with a cutting or dilution agent with which it is 
miscible, that is, as two or more miscible components as described in a 
copending patent application assigned to the same assignee as the instant 
patent application and filed herewith. For example, the polyarylsiloxane 
fluids may be mixed with polydimethylsiloxane to provide effective 
release. Effective release is generally provided when there are at least 
about 0.5 aryl or substituted aryl groups per molecule. The release agents 
of the present invention may also be applied as a single component to 
provide both the interfacial barrier and the release surface. 
In applying the polyarylsiloxane fluid to the surface of the fuser member, 
the fluid which is capable of interacting with the fuser member surface to 
form a thermally stable interfacial barrier to the toner, must be applied 
in an amount sufficient to cover the surface with at least a continuous 
low surface energy film in order to provide the fuser member with a 
surface which not only releases toner heated by the fuser member but also 
with an amount which will prevent the toner from contacting the surface of 
the fuser member. Generally, in accordance with the objects of the present 
invention, the amount sufficient to cover the surface must be that amount 
which will maintain a thickness of the fluid in a range of submicron to 
microns and is preferably from about 0.5 micron to about 10 microns in 
thickness, and more preferably from about 1 to about 4 microns. Thus, in 
essence, the layer of the polyarylsiloxane fluid on the surface of the 
fuser member is so slight that there is essentially a bare fuser member. 
Although this layer or coating of the polyarylsiloxane fluid may be 
applied to the fuser member surface intermittently, it is generally 
preferred to apply the fluid continuously on the heated fuser member to 
maintain thereon a coating of the fluid and the interaction product or 
products formed by interaction with the material of the fuser member. 
During operation of any automatic electrostatic reproducing apparatus, it 
is generally preferred to apply continuously the fluid on the heated fuser 
member in order to replace the fluid which is retained by the substrate 
when the substrate is the type which absorbs the fluid or to which the 
fluid may adhere, generally in an amount which is measured in fractions of 
a microliter for each copy. However, in embodiments where there is little 
or no loss of the fluid from the surface of the fuser member, continuous 
application of the fluid may not be necessary, and it may be preferred to 
utilize application techniques which only apply fluid intermittently to 
the surface. 
In general, the method of the present invention applies to fusing 
electroscopic toner images to a substrate and includes the steps of 
forming a coating or layer on a heated fuser member of an electrostatic 
reproducing apparatus, said coating being a barrier to the electroscopic 
toner and comprising the product resulting from the interaction of the 
fuser member and polyarylsiloxane fluid, said polyarylsiloxane being fluid 
at the temperatures of the fuser member and acting as a release coating 
for the electroscopic toner. The toner image on the substrate, e.g., 
paper, polymeric sheets, metals, and the like, is contacted with the 
heated fuser member for a period of time sufficient to soften the 
electroscopic toner, and then the softened toner is allowed to cool. The 
toner barrier coating and the fluid toner release coating are preferably 
on the order of about 0.5 micron in thickness. The thickness of the 
barrier coating and release layer is limited only to the extent that such 
barrier coating and release layer do not substantially prevent heat 
transfer from the inner core of the fuser member to the toner undergoing 
fusing upon a substrate, and to the extent that there is a sufficient film 
of the release material on the surface of the fuser member to prevent hot 
offsetting on the heated fuser member, that is, to prevent the retention 
of the tackified or molten toner by the surface of the heated fuser member 
so that the retained toner will not transfer to the next substrate 
containing the heated fuser member. 
The electroscopic toners that form the toner images, for example, numeral 
14 in FIG. 1, are preferably comprised of a thermoplastic resin in 
addition to colorant such as dyes and/or pigments. Examples of 
conventional pigments are carbon black and furnace black. The developer 
material may also contain cleaning materials, plasticizers, and other 
additives in accordance with the desired formulation. Typical toners may 
be chosen by one skilled in the art and also include thermosetting resins 
and other conventional heat fusible materials comprising resinous 
components. For example, a copolymerized mixture of styrene or a blend of 
styrene monologs with 10-40 percent (by weight) of one or more 
methacrylate esters selected from the group consisting of ethyl, propyl 
and butyl methacrylates as described in U.S. Pat. No. 3,709,342 may be 
used, said reference being incorporated herein by reference. Typical toner 
materials include gum copal, gum sandarac, rosin, asphaltum, pilsonite, 
phenol formaldehyde resins, rosin-modified phenol formaldehyde resins, 
methacrylic resins, polystyrene resins, polypropylene resins, epoxy 
resins, polyethylene resins and mixtures thereof. Among other patents 
describing the electroscopic toner compositions are U.S. Pat. No. 
2,659,670 to Copley; U.S. Pat. No. 2,754,408 to Landrigan; U.S. Pat. No. 
3,079,342 to Insalaco; U.S. Pat. Reissue No. 25,136 to Carlson and U.S. 
Pat. No. 2,788,288 to Rheinfrank et al. 
The surface to which the polyarylsiloxane is applied, may be heated to 
insure proper formation of the interfacial layer which is the result of 
interaction between the polyarylsiloxane fluid and the surface of the 
fuser member. Thus, the interfacial layer becomes heated and remains as a 
barrier layer upon the surface of the fuser member. Generally, the 
unreacted or virgin release fluid as it is applied to the fuser member, is 
heated to the temperature of the fuser roll, however, the release fluid 
may be somewhat cooler than the roll during operation of the device when 
heat transfer takes place, that is, when heat is transferred from the 
fuser member to the substrate containing toner undergoing the fusing 
process. The temperature may be adjusted by one skilled in the art in 
accordance with the particular type of toner, in accordance with the speed 
of the apparatus, and in accordance wih any other parameters which are 
known to one skilled in the art. 
The release properties of the polyarylsiloxane fluids, are related to the 
splitting of the image when the toner is softened and becomes sufficiently 
sticky to adhere to the surface of the fuser roll which results in a 
partial or ghost image on the next sheet, producing what is referred to as 
an offset image. Therefore, the release property of the particular 
polyarylsiloxane fluid is a function of the offset image, and the higher 
the temperature of the fuser member before hot offsetting occurs, the 
better the release properties of the particular fluid. Furthermore, the 
fusing latitude, that is, the temperature at which the toner begins to 
fuse up to the temperature at which hot offset occurs, is also a function 
of the release properties of the particular polyarylsiloxane fluid. This 
fusing latitude, that is, the temperature range at which the fusing member 
can operate and including the temperature from which the toner begins to 
fuse up to the temperature where hot offset begins to occur, is also known 
as the fusing window of the fuser member. The fusing latitude is 
substantially improved over conventional art agents and polymeric coatings 
when the polyarylsiloxane fluids are applied to the fuser member. 
Exemplary of fusing the toner material to the substrate is a fuser assembly 
which comprises a heated roll structure including a hollow cylinder or 
core having a suitable heating element disposed in the hollow portion 
thereof which is coextensive with the cylinder. The heating element may 
comprise any suitable type of heater for elevating the surface temperature 
of the cylinder to operational temperatures which are generally from 
250.degree.-400.degree. F (121.degree.-205.degree. C), and for example, 
may be a quartz lamp. The cylinder must be fabricated from any suitable 
material capable of accomplishing the objects of the invention, that is, a 
material which not only will transfer heat to the surface to provide the 
temperature required for fusing the toner particles, but also a material 
having a surface which is capable of interacting with the polyarylsiloxane 
release agent to form a product which becomes an interfacial layer or 
barrier layer to toner intermediate the release layer and the surface of 
the bare fuser member to prevent toner particles from contacting the fuser 
surface. 
Typical fuser member materials are anodized aluminum and alloys thereof, 
steel, stainless steel, nickel, and alloys thereof, nickel plated copper, 
copper, glass, zinc, cadmium, and the like and various combinations of the 
above. The cylinder may be fabricated from any suitable material which is 
capable of interacting with the polyarylsiloxane release fluid. Surface 
temperature of the fuser member may be controlled by means known to those 
skilled in the art, for example, by means described in U.S. Pat. No. 
3,327,096. 
In general, the fuser assembly further comprises a backup member, such as a 
roll or belt structure which cooperates with the fuser roll structure to 
form a nip through which a copy paper or substrate passes such that toner 
images thereon contact the fuser roll structure. The backup member may 
comprise any suitable construction, for example, a steel cylinder on a 
rigid steel core having an elastomeric layer thereon, or it may be a 
suitable belt material which provides the necessary contact between the 
fuser member and the substrate carrying the developed latent image. The 
dimensions of the fuser member and backup member may be determined by one 
skilled in the art and generally are dictated by the requirements of the 
particular copying apparatus wherein the fuser assembly is employed, the 
dimension being dependent upon the process speed and other parameters of 
the machines. Means may also be provided for applying a loading force in a 
conventional manner to the fuser assembly to create nip pressures on the 
order of about 15 to 150 psi average. 
The fuser member treated by the method of the present invention wherein at 
least one polyarlysiloxane fluid is applied to a fuser member surface, 
said fluid being capable of interacting with the fuser member surface to 
form a thermally stable interfacial layer and being applied in an amount 
sufficient to cover the surface with at least a continuous, low surface 
energy film of the fluid to prevent the toner from contacting the surface 
of the fuser member and to provide a surface which releases the toner 
heated by the fuser member, is illustrated in the fuser assembly shown in 
FIG. 1. In FIG. 1, the numeral 1 designates a fuser assembly comprising 
heated roll structure 2, backup roll 8 and sump 20. Heated roll 2 includes 
a hollow cylinder 4 having a suitable heating element 6 disposed in a 
portion thereof which is coextensive with the cylinder. 
Backup roll 8 cooperates with roll structure or hollow substrate 2 to form 
a nip 10 through which a copy paper or other substrate 12 passes such that 
toner images 14 thereon contact heated roll 2. As shown in FIG. 1, the 
backup roll 8 has a rigid steel core 16 with an elastomer surface or layer 
18 thereon. 
Cylinder 4 being fabricated of metal such as anodized aluminum, aluminum 
and alloys thereon, steel, nickel and alloys thereof, copper, and the like 
as described above or glass, has a surface made of relatively high surface 
energy materials, and consequently toner material 14 contacting such 
surfaces when they are heated, would readily wet the surface. Accordingly, 
there is provided in accordance with the embodiment of FIG. 1, sump 20 for 
containing at least one of the designated polyarylsiloxane release agents 
22 capable of displacing heat fusible electroscopic toner when the agent 
is in a fluid state, said release agent being capable of interacting with 
the fuser member surface to form a thermally stable interfacial layer 
thereon when in the fluid state. The release material 22 may be a solid or 
liquid at room temperature, but it must be a fluid at operating 
temperatures preferably having a relatively low viscosity at the operating 
temperatures of heated roll 2. 
In the embodiment shown in FIG. 1 for applying release material 22 to the 
surface of heated roll 2, a metering blade 24 preferably of conventional 
non-swelling rubber is mounted to sump 20 by conventional means such that 
an edge 26 thereof contacts the solid substrate 2 of the fuser roll 
structure to serve as a metering means for applying release material 22 to 
the fuser roll in its liquid or fluid state. By using such a metering 
blade, a layer of release fluid 22 can be applied to the surface of heated 
roll 2 in controlled thicknesses ranging from submicron thicknesses to 
thicknesses of several microns of the release fluid. Thus, by metering 
device 24, about 0.1 to 0.5 micron or greater thicknesses of release fluid 
can be applied to substrate 2. In the embodiment shown, a pair of end 
seals 28, for example, of sponge rubber, are provided to contain the 
release material 22 in sump 20. One or more stripper fingers 30 may be 
provided for insuring removal of the substrate 12 from substrate 2. In one 
of the preferred embodiments, thermoplastic resin toner is fused to paper, 
however, thermoplastic resin toner may be fused to other substrates such 
as polymeric films, metals and other substrates by the fuser members and 
process of the present invention, the only limitation being that the 
polyarylsiloxane fluids must not adversely react with the substrate upon 
which the toner is used and must not destroy or alter the coloring 
properties of the toner. 
The embodiment described above in FIG. 1 is merely one of the preferred 
means for applying a layer of polyarylsiloxane release material capable of 
interacting with the fuser member surface to form a thermally stable 
interfacial barrier layer in an amount sufficient to cover the surface 
with at least a continuous, low surface energy film of the fluid to 
provide the fuser member with a surface which releases toner heated by the 
fuser member. Other means for applying the release fluid which is abhesive 
to heat fusible electroscopic toner at elevated temperatures comprise 
means which spray a layer of the release fluid upon the fuser surface, a 
pad or sponge-like material which pads a coating of the release fluid on 
the surface of the fuser member, a wick which contacts the surface of the 
fuser member to provide a film or layer of the release material, extruding 
means which extrude a minute film of the release material on the fuser 
member, a brush having fibers or bristles comprised of the release 
material or a brush or bristle having the release fluid on the surfaces of 
the bristles or brush materials, fluid soaked rolls, sponges or wicks and 
the like. 
The fuser member for an electrostatic reproducing apparatus resulting from 
the method of treating the surface of a heated fuser member with at least 
one polyarylsiloxane fluid capable of displacing electroscopic toner, is 
shown in FIG. 2. The fuser member shown in FIG. 2 is magnified many times 
over the member shown in FIG. 1 in order to show the thin layers on the 
fuser member surface. In FIG. 2, the solid portion of the heated roll is 
designated by numeral 4. A release layer of fluid is designated by numeral 
64 and an interfacial layer is designated by numeral 60. Thus, there is 
described a fuser member having a solid substrate 4, a release layer of 
polyarylsiloxane fluid, 64, which is abhesive to electroscopic toner and 
which interacts with the solid substrate 4, and interfacial layer 60 which 
prevents the electroscopic toner (not shown) from contacting solid 
substrate 4, said interfacial layer 60 being formed by the interaction of 
solid substrate 4 and the polyarylsiloxane fluid release layer 64. 
In one of the preferred embodiments, solid substrate 4 of FIG. 2 comprises 
a metal capable of forming oxides, and in more preferred embodiments, the 
solid substrate 4 may be selected from the group consisting of iron, 
copper, aluminum, titanium, zinc, silver, nickel and cadmium and 
oxide-forming alloys thereof. Solid substrate 4 may also be comprised of 
glass and other oxide media. In accordance with the present invention, it 
has been unexpectedly observed that when solid substrate 4 in FIG. 2 is an 
oxide-containing or -forming material and the release agent 64 is the 
designated polyarylsiloxane fluid, and electroscopic toner is applied 
thereto and softened, the electroscopic toner is displaced from solid 
substrate 4 by the action of fluid 64 applied thereto when release layer 
64 and interfacial layer 60 are interrupted, and the surface of the 
substrate 4 is exposed to the toner. Interruptions in the release layer 64 
and interfacial layer 60 may occur, for example, by scraping the surface 
by the stripper finger, by a thermistor device to control the temperature 
at the surface, by other abrasive forces which scratch or deface the 
layers coated on solid substrate 4, and the like. Thus, when electroscopic 
toner is applied to the surface which has been interrupted by such forces, 
it was unexpectedly found that the electroscopic toner is displaced from 
the solid substrate 4 by the action of the release layer material as it is 
applied to the fuser member. Although the details of this mechanism are 
not completely understood, it is believed that the polyarylsiloxane 
release fluids actually compete with the electroscopic toner for the 
surface of substrate 4, and because the release material is more reactive 
toward the solid substrate surface 4 than is the electroscopic toner, the 
release material actually displaces the electroscopic toner from substrate 
4 as it reforms interfacial layer 60 in the interrupted zone or portion of 
the surface by the interaction of the release material 64 and the surface 
4. Thus, by using conventional electroscopic toners, the release layer 
fluids are actually found to displace the electroscopic toner applied to 
and softened upon the surface of the fuser roll from any interruptions 
occurring therein, thereby preventing offsetting of the material and 
ghosting of the image. 
A preferred apparatus and method for contact fusing of toner particles to 
substrate are provided by using a heated structure having a rigid core, 
the surface of which has a high surface energy material, e.g., metals and 
glasses. The core may be heated internally or externally. The core is 
coated with a coating of a polyarylsiloxane release material, the 
polyarylsiloxane being the type which is capable of some type of reaction 
(interaction) with the core surface material. The coating on the core 
surface comprises a first barrier coating portion in contact with the core 
surface, this first portion being formed during operation of the apparatus 
at the interface of the core surface and the polyarylsiloxane release 
material. The first portion has a greater affinity for the core surface 
material than the toner particles and thereby prevents toner particles 
from contacting the core. A second replenishing release portion is the 
release material itself, the polyarylsiloxane which has a cohesive force 
which is less than the adhesive forces between the toner particles and the 
substrate and the cohesive forces of the toner particles. A backup member 
is provided to cooperate with the heated structure to form a nip through 
which the substrate having toner particles thereon passes with the toner 
particles contacting the heated structure. 
The following examples further define and describe exemplary materials for 
treating the surfaces of heated fuser members in an electrostatic 
reproducing apparatus with a polyarylsiloxane fluid capable of displacing 
electroscopic toner, the fluid being capable of interaction with the fuser 
member surface to form a thermally stable interfacial layer thereon. Parts 
and percentages are by weight unless otherwise indicated. The examples are 
also intended to illustrate the various preferred embodiments of the 
present invention. 
EXAMPLE I 
In determining the effectiveness of the polyarylsiloxane fluids, flat plate 
toner-release testing (static) was conducted upon a steel surface at 
395.degree. F (202.degree. C). A heat fusible toner comprising carbon 
black pigmented copolymer, styrene-n-butylmethacrylate, (Xerox Corp. 364 
Toner), was used to test release of the tacified toner from the steel 
surface. Phenyl silicone fluids (phenyl polydimethyl siloxane) provided by 
Dow Corning Corporation under the trade designation DC510 and have 
respective viscosities of 50, 100 and 1000 centistokes at 25.degree. C, 
were metered onto the heated plates. These fluids demonstrated excellent 
release of the described toner material when applied to the metal surface 
on a paper substrate. 
EXAMPLE II 
The toner of Example I was fused on both an aluminum and a steel plate 
coated with polydimethyl siloxane fluid (silicone oil). Immediate release 
failure was observed in both cases at 202.degree. C (395.degree. F). 
EXAMPLE III 
In determining the effectiveness of the polyarylsiloxane fluids an 
electrostatic latent image is formed on a conventional recording surface 
in a conventional electrostatic reproducing apparatus, and the 
electrostatic latent image is developed with a heat fusible toner 
comprising carbon black pigmented copolymer, styrene-n-butylmethacrylate 
(Xerox Corporation 364 Toner), the toner particles being held on the 
recording surface in conformance with the electrostatic latent image. The 
toner image is thereafter transferred to plain paper. The paper having the 
toner images electrostatically adhered thereto, is then passed at a speed 
of about 15 inches per second between a fuser roll structure and a backup 
roll, the fuser roll structure being the type wherein temperature can be 
controlled as well as nip pressure. The toner image contacts a fuser roll 
structure which has a 2.0 inch outside diameter and is 4 inches long. The 
backup roll has an outside diameter of about 2.0 inches with a 0.1 inch 
layer of silicone rubber covered with a 0.020 inch coating of fluorinated 
ethylenepropylene resin on the surface and having a durometer of 65 Shore 
A. The fuser roll is fabricated from steel. Phenyl polydimethyl siloxane 
fluid provided by Dow Corning Corporation under the trade designation 
DC510 and having respective viscosities of 50, 100 and 1000 centistokes at 
25.degree. C is metered onto the fuser roll by means of a doctor blade 
prior to contacting thereof by the toner image. Fuser latitude or fusing 
window is then determined. The fusing range at which release of toner 
occurs begins at about 225.degree. F (107.degree. C) and extends to about 
400.degree. F (204.degree. C). This is an advantage of nearly 200.degree. 
F (nearly 100.degree. C) and corresponds to a large increase in fusing 
component life and machine copy per minute speed. The fusing range remains 
about the same for the fluids having viscosities of 50, 100 and 1000 
centistokes at 25.degree. C respectively. 
In accordance with the stated objects there has been demonstrated a release 
agent, a fusing process and a fusing member for fixing toner images. In 
the above experiments with the release agents, toner is actually displaced 
from exposed surfaces of fuser members having the polyarylsiloxane fluids 
with at least one aryl or aryl substituted per polymer molecule coated 
upon the surface, by reason of the action of the release agent. Where the 
surface areas are gouged so that toner material becomes lodged upon the 
steel surface, the toner material is actively displaced from the surface 
of fuser members by the action of the release agent, and toner 
contamination of subsequent copies is avoided. It has been demonstrated 
that fuster members need no longer be coated with solid fluoropolymers, 
gums or elastomers in addition to various oils and fluids to promote 
release of toner comprising resinous components from fuser members. 
While the invention has been described with respect to preferred 
embodiments, it will be apparent that certain modifications and changes 
can be made without departing from the spirit and scope of the invention, 
and therefore, it is intended that the foregoing disclosure be limited 
only by the claims appended hereto.