Heat fixing roll for electrophotographic duplicators

Silicone rubber is employed as an outer coating material on a fuser member and is applied to the base member by means of a novel construction which prevents the separation of the outer silicone rubber coating from the roll even when silicone oil is applied thereto. The fuser member comprises a base member, a layer of a heat-resistant resin formed on the base member and a layer of a silicone rubber formed on the heat-resistant resin layer, the silicone rubber being vulcanized after the formation of the layer of silicone rubber on the resin layer. A primer layer may be used between the heat-resistant resin layer and the silicone rubber layer.

BACKGROUND OF THE INVENTION 
This invention relates generally to members utilized for pressure fusing 
toners at elevated temperatures, and more particularly to improved heat 
fixing rolls for preventing offsetting of dry toners onto the roll during 
the fusing operation in electrophotographic duplicators. 
In the process of electrophotographic duplication 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 particles, 
commonly referred to as toner. The visual toner image can be either fixed 
directly upon the photosensitive member or transferred from the member to 
another support, such as a sheet of plain paper, with subsequent affixing 
of the image thereto. Toners are well known in the art and may be of 
various types. 
In order to affix or fuse electroscopic toner material onto a support 
surface 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 sheets or member or 
otherwise upon the surface thereof. Thereafter, as the toner material 
cools, solidification of the toner material occurs causing the toner 
material to be bonded firmly to the support sheet or member. In both the 
xerographic as well as the electrograhic recording arts, the use of 
thermal energy for fixing toner images onto a support member is old and 
well known. 
Several approaches to thermal fusing of electroscopic toner images onto a 
support have been described in the prior art and include providing the 
concomitant application of heat and pressure as by a roll pair maintained 
in pressure contact, a flat or curved plate member in pressure contact 
with a roll, a belt member in pressure contact with a roll, and the like. 
Heat may be applied by heating one or both of the rolls, plate members or 
belt members. The fusing of the toner takes place when the proper 
combination of heat, pressure and contact time are provided, the balancing 
of these parameters being well known in the art and varying according to 
various factors which must be independently determined for each particular 
situation. 
During operation of a fusing system of the type where there is a thermal 
fusing of electroscopic toner images onto a support in which at least one 
fuser member, such as a roll, plate or belt, is heated, the support member 
to which the toner images are electrostatically adhered, it moved through 
the nip formed between the members with the toner image pressure 
contacting the fuser roll thereby to effect heating of the toner images 
within the nip. By controlling the heat transfer to the toner, virtually 
no offset of the toner particles from the copy sheet to the fuser member 
is experienced under normal conditions. This is because the heat applied 
to the surface of the fuser member is insufficient to raise the 
temperature of the surface of the member 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 in the molten toner 
resulting in "hot offset." Splitting occurs when the cohesive forces 
holding the viscous toner mass together is less than the adhesive forces 
tending to offset it to a contacting surface such as a fuser roll, fuser 
belt, or fuser plate. 
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 imperfection in the properties of the surface of the roll; 
by the toner particles insufficiently adhering to the copy sheet; by the 
electrostatic forces which normally hold them there; or in certain cases 
by the reactivity of the toner material itself. In such as case, toner 
particles may be transferred to the surface of the fuser member with 
subsequent transfer to the backup member which provides pressure contact, 
during periods of time when no copy paper is in the nip. 
In many of these pressure contact, heat fixing systems, a heated member, 
e.g. a roll, provided with a covering of a heat-resistant, releasing 
material on the outer surface thereof is contacted with a back-up or 
pressure roll covered with a heat-resistant, flexible material layer under 
nip pressure, between which the sheet to be fixed, is passed for fixing 
the toner image. 
As an example of the heat-resistant, release material for the fuser member, 
there are well known materials such as polytetrafluoroethylene, silicone 
rubber, fluorocarbon elastomers and the like. In certain cases, a suitable 
off-set preventing liquid is fed onto the fuser member to minimize or 
avoid such problems as "offsetting." Silicone oils are widely applied as 
the off-set preventing liquid. 
In the pressure contact heat fixing device of the type described above, the 
fuser member is covered with a certain thickness of heat-resistant 
silicone rubber which releases toner material and has an elastic, 
compressible surface. When silicone rubber is used as the outer layer of 
the fuser member, the fused image has excellent quality. 
The silicone rubbers which can be used as the outer layer coating the base 
or core of the fuser member, can be classed into three groups according to 
vulcanization method and temperature, i.e., room temperature 
vulcanization-type silicone rubber, hereinafter referred to as RTV 
silicone rubber, low temperature vulvanization-type silicone rubber, 
hereinafter referred to as LTV rubber, and high temperature 
vulcanization-type silicone rubber, hereinafter referred to as HTV rubber. 
These silicone rubbers are well known in the art and are commercially 
available. 
When employed as a fuser member covering material, the RTV and LTV silicone 
rubbers are generally superior in releasing property to the HTV silicone 
rubber and thus generally produce favorable results in fusing toner 
images. The RTV silicone rubbers now commercially available exhibit 
excellent release of toner images for about 5,000 to 30,000 copies fused 
by heat. Thereafter, there is a tendency for the off-set problem and 
winding of copying paper about the fuser roll to occur. When this occurs, 
it is necessary to replace the used fuser roll. 
To overcome the foregoing problems it is well known that silicone oil may 
be applied to the surface of the fuser member (upon the silicone rubber 
layer) as an off-set preventing liquid during fixing operations. However, 
when silicone rubber is used as a heat-resistant, release layer to cover 
the fuser member, the use of a silicone oil is disadvantageous in that the 
silicone rubber is susceptible to swelling by the action of the silicone 
oil, so that the oil readily penetrates the rubber, resulting in 
separation of the rubber from a base or core. Thus, the application of 
silicone oil is effective in improving the release characteristics but it 
sacrifices the durability of the silicone rubber layer covering the fuser 
member. For this reason, silicone rubber coated fuser members have a short 
life time and generally permit no more than about 30,000 fusing cycles per 
fuser member. 
OBJECTS OF THE INVENTION 
Accordingly, it is the principal object of this invention to provide a new 
and improved silicone rubber coated fuser member for use in fuser 
assemblies in xerographic duplicating machines which overcome the 
foregoing disadvantages. 
Another object of the present invention is to provide a fuser member which 
has a heat resistant, silicone rubber surface layer or coating as a 
release material for toner images in which no separation occurs between 
the base or core and the silicone rubber layer when silicone oil is fed or 
metered on the silicone rubber. 
Still another object of the invention is to provide a silicone rubber 
coated fuser member having an improved life. 
SUMMARY OF THE INVENTION 
The above-cited objects of the present invention are accomplished by a 
fusher member for pressure fusing toned electrostatic images at elevated 
temperatures, comprising a base member or core, a layer of a 
heat-resistant resin material coated on the base member or core surface 
and an outer layer of silicone rubber coated upon the layer of 
heat-resistant resin material, the silicone rubber layer being vulcanized 
after it is placed upon the layer of heat-resitant resin material. 
Alternatively, a layer or primer material may be used between the 
heat-resistant resin material and the silicone rubber layer, and the 
primer material must be one which promotes the adhesion of the silicone 
rubber to the base member or core surface. 
Exemplary of silicone rubbers which may be vulcanized after a layer of the 
rubber is placed upon the heat-resistant resin material or the primer 
material, are conventional RTV, LTV or HTV silicone elastomers, and the 
vulcanization may be carried out according to procedures well known by 
those skilled in the art. 
The heat-resistant material may be the polyamide resins, polyamideimide 
resins or polyimide resins well-known in the art. These heat-resistant 
resins may be formed on the base member or core by techniques well known 
in the art. 
In accordance with the present invention it has been found that even when 
the fusing of toner images is carried out in a pressure contact heat 
fusing device while feeding a silicone oil to the heat fixing roll, the 
high adhesion between the roll core and the silicone rubber layer is 
ensured by forming on the roll core a heat-resistant layer of a polyamide 
resin, a polyamideimide resin or a polyimide layer, prior to the formation 
of the silicone rubber layer upon the heat-resistant layer or upon an 
optional primer layer. The resultant pressure contact heated fuser member 
has an extended life even though silicone oil is applied to the surface of 
the fuser. 
These as well as other objects of the invention and further features 
thereof will be better understood upon reference to the following detailed 
description of the invention when read in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The fuser embodiments of the present invention may be used in an automatic 
xerographic reproducing or duplicating machine, such as the automatic 
xerographic reproducing machine described in U.S. Pat. No. 3,937,637, said 
patent being incorporated herein by reference. Therein is illustrated a 
reproducing machine which employs an image recording drum-like member, the 
outer periphery of which is coated with a suitable photoconductive 
material. One type of photoconductive material is disclosed in U.S. Pat. 
No. 2,970,906 issued to Bixby in 1961. The photoconductive drum is 
suitably journaled for rotation within a machine frame by means of a shaft 
which rotates to bring the image retaining surface thereon past a 
plurality of xerographic processing stations. Suitable drive means are 
provided to power and coordinate the motion of the various cooperating 
machine components whereby a faithful reproduction of the original input 
scene information is recorded upon a sheet of final support material such 
as paper or the like. 
Since the practice of xerography is well known in the art, the various 
processing stations for producing a copy of an original are represented as 
stations A to E. Initially, the drum moves the photocondcutive surface 
through a charging station A. At charging station A an electrostatic 
charge is placed uniformly over the photoconductive surface of the drum 
preparatory to imaging. The charging may be provided by a corona 
generating device of a type described in U.S. Pat. No. 2,836,725 issued to 
Vyverberg in 1958. 
Thereafter, the drum is rotated to exposure station B where the charged 
photoconductive surface is exposed to a light image of the original input 
scene information, whereby the charge is selectively dissipated in the 
light exposed regions to record the original input scene in the form of a 
latent electrostatic image. A suitable exposure system may be provided by 
one skilled in the art. 
After exposure the photoconductive drum rotates the electrostatic latent 
image recorded on the photoconductive surface to development station C, 
wherein a conventional developer mix is applied to the photoconductor 
surface rendering the latent image visible. A suitable development station 
may include a magnetic brush development system utilizing a magnetizable 
developer mix having carrier granules and toner comprising 
electrophotographic resin plus colorant from dyes or pigments. A developer 
mix is continuously brought through a direction flux field to form a brush 
thereof. The electrostatic latent image recorded on the photoconductive 
surface is developed by bringing the brush of developer mix into contact 
therewith. The developed image on the photoconductive surface is then 
brought into contact with a sheet of final support material within a 
transfer station D and the toner image is transferred from the 
photoconductive surface to the contacting side of a final support sheet. 
The final support material may be plain paper, gummed labels, 
transparencies such as polycarbonate, polysulfone and Mylar, etc., as 
desired. 
After the toner image has been transferred to the sheet of final support 
material, the sheet with the image thereon is advanced to a suitable fuser 
assembly which fuses the transfer powder image thereto. After the fusing 
process, the final support material is advanced by a series of rolls to a 
copy paper tray for subsequent removal therefrom by a machine operator. 
Although most of the toner powder is transferred to the final support 
material, some residual toner remains on the photoconductive surface after 
the transfer of the toner powder image to the final support material. The 
residual toner particles remaining on the photoconductive surface after 
the transfer operation are removed from the drum as it moves through 
cleaning station E. Here the residual toner particles may first be brought 
under the influence of a cleaning corona generating device adapted to 
neutralize the electrostatic charge remaining on the toner particles. The 
neutralized toner particles are then mechanically cleaned from the 
photoconductive surface by conventional means as for example, the use of a 
resiliently biased knife blade. Other cleaning modes may be used at 
cleaning station E as desired by one skilled in the art. 
It is believed that the foregoing description is sufficient for purposes of 
the present application to illustrate the general operation of a preferred 
automatic xerographic copier which can embody the teachings of the present 
invention. 
As discussed above, fuser assemblies include cylindrical rolls, flat 
plates, curved plates, belts and the like having at least an outer surface 
of silicone rubber. 
A typical prior art fuser roll as shown in FIG. 1, comprises fuser roll 
core 1 and layer 2 made of a self-adhesive RTV silicone rubber which is a 
heat-resistant release material place upon or formed around core 1. 
Numeral 5 represents a hollow core for a heating element or it may be a 
solid body to support the core structure 1. In FIG. 2, there is shown 
another prior art fuser roll which comprises fuser roll core 1, primer 
undercoat layer 3 and outer layer 2 of a RTV, LTV or HTV silicone rubber 
placed upon or formed around the outer surface of core 1 in the order 
shown, outer layer 4 being vulcanized after it is placed upon core 1. 
Numeral 5 may be the same structure as described in FIG. 1. The prior art 
primer material which is used for adhering silicone rubber to a roll core 
includes, for example, a silane having an unsaturated bond such as 
vinyl-trimethoxysilane, gamma-methacryloxypropyltrimethoxysilane, 
vinyltris(b-butylperoxy) silane and the like, or a partially hydrolyzed 
condensate thereof. 
The present invention is described in detail with reference to FIGS. 3, 4, 
and 5. As shown in the drawings and preferred embodiments, the invention 
is described in the form of a fuser roll, however, the invention is also 
applicable to the fuser member configuration described above. 
According to FIG. 3 of the present invention, there is provided a fuser 
roll 10 which comprises a hollow heated roll core 1 (heating element not 
shown), a layer 4 of a heat-resistant resin composition such as a 
polyamide, a polyamideimide, a polyimide or combinations thereof, placed 
upon or formed on the surface of core 1, and outer covering layer 2 of a 
RTV, LTV or HTV silicone rubber placed upon or formed around layer 4, 
outer covering layer 2 being vulcanized after it is placed upon or formed 
around layer 4. 
In FIG. 4, one embodiment of the present invention is shown as 
incorporating a primer layer 3 between silicone rubber layer 2 and 
heat-resistant resin layer 4. Thus, fuser roll 40 comprises a hollow 
heated roll core 1 (core heating element not shown), a layer 4 of a 
heat-resistant resin composition such as a polyamide resin, a 
polyamideimide resin, or a polyimide resin formed upon roll core 1, a 
primer layer 3 formed upon heat resistant resin layer 4, and an outer 
covering layer 2 of a RTV, LTV or HTV silicone rubber placed upon or 
formed around primer layer 3, outer covering layer 2 being vulcanized 
after it is placed upon or formed around layer 3. 
A number of primer materials are well-known for the adhesion of silicone 
rubbers to substrates, and it is within the purview of one skilled in the 
art to select such primers. These primers include, for example, silanes 
having unsaturated bonds, such as vinyltrimethoxysilane, 
gamma-methacryloxypropyltrimethoxysilane, vinyltris(t-butylperoxy)silane, 
and the like, and partially hydrolyzed products thereof. Other adhesive 
primers include the polysiloxane compositions disclosed and claimed as 
adhesive layers in U.S. patent application Ser. No. 751,825 filed Dec. 17, 
1976 and assigned to the instant assignee. Therein is disclosed and 
claimed a polysiloxane composition intermediate the silicone rubber layer 
and a base member comprising: 
(a) 100 Parts by weight of an organopolysiloxane expressed by the empirical 
formula, R.sup.1.sub.n SiO.sub.(4-n/2) wherein R.sup.1 represents a 
substituted or unsubstituted monovalent hydrocarbon group, at least 80 
mole percent of R.sup.1 being a methyl group and having no more than 0.2 
mole percent of an aliphatic unsaturated group, and n is a positive 
numerical value of from 1.98 to 2.01, and having a viscosity greater than 
100,000 centistokes at 25.degree. C; 
(b) 5 to 100 parts by weight of an organopolysiloxane expressed by the 
empirical formula, R.sup.2.sub.m SiO.sub.(4-m/2) wherein R.sup.2 
represents a substituted or non-substituted monovalent hydrocarbon, 3 to 
25 mole percent of R.sup.2 being a vinyl group, and m is a positive 
numerical value of from 1.9 to 2.3, and having a viscosity of from 5 to 
10,000 centistokes at 25.degree. C; 
(c) 1 to 80 parts by weight of an allyl ester of a polybasic acid; 
(d) 3 to 20 parts by weight of an aliphatic acid salt of a metal; and 
(e) 0.2 to 20 parts by weight of a silane compound expressed by the general 
formula, R.sup.3 Si(OR).sup.4.sub.3, wherein R.sup.3 represents an 
unsaturated hydrocarbon group and R.sup.4 represents a member selected 
from the group consisting of a methyl group, a B-methoxyethyl group, a 
B-ethoxyethyl group and a tertiarybutylperoxy group. B stands for beta. 
The primer composition or mixture of primer compositons may further 
comprise for example, finely powdered silica to improve the mechanical 
strength thereof, or ferric oxide or cerium oxide to improve heat 
resistance. To facilitate application of the primer composition onto the 
heat-resistant layer upon a roll core surface, suitable solvents may be 
added to the composition for controlling the viscosity of the composition. 
Examples of the solvents include benzene, toluene, xylene, 
trichloroethylene, perchloroethylene, methylene chloride, ethanol, 
isopropanol, butanol, n-hexane and the like. These solvents may be used 
separately or in combination with each other. 
FIG. 5 shows a pressure contact heated fuser assembly having fuser roll 20 
which comprises heating element 22, metal core 24 accommodating therein 
heating element 22, and outer layer or coating 26 made of a 
heat-resistant, release material placed upon or formed around metal core 
24. The fuser assembly of FIG. 5 also comprises pressure roll 30 made of a 
heat-resistant, flexible surface material and which comprises metal core 
32, silicone rubber layer 34 formed around or coated upon core 32, and 
polyfluoroethylenepropylene layer 36 covering silicone rubber layer 34. 
The fuser roll 20 and the pressure roll 30 contact and cooperate with each 
other by a suitable mechanism (not shown) so that a suitable pressure is 
applied on a nip line designated by numeral 38. Sheet 40 bearing thereon 
toner image 42 is passed between rolls 20 and 30. On fuser roll 30 is 
mounted an intermediate oil-feeding member 44 from which a silicone oil 
46, on an off-set preventing liquid, is fed to the fuser roll 20 and which 
also serves to clean the fuser roll 20. The silicone oil 46 in sump 56 is 
fed to the oil-feeding member 44 through another intermediate oil-feeding 
member 50 by means of feeding roll 48. Indicated at 52 is a weight for 
pressing oil-feeding member 44 against silicone rubber layer (outer layer) 
26. The pressure roll 30 is contacted with a cleaning member 60 held on a 
supporting member 62. the fuser roll 10 of FIG. 3 or the fuser roll 40 of 
FIG. 4 may be substituted for fuser roll 20 in FIG. 5, and heating element 
22 may be incorporated therein if desired. 
The fuser roll body or core which is suitable for coating with the layers 
of this invention, can be made of various kinds of metals such as iron, 
aluminum, nickel, chromium, copper, and the like, and alloys thereof, such 
as stainless steel, brass, and the like, and various synthetic resins. Of 
these, iron, aluminum, copper, stainless steel, brass and the like 
materials are preferred. One skilled in the art can select an appropriate 
core material. 
The method of providing the necessary heat is not critical in the present 
invention, and the fuser members can be heated by internal means, external 
means or both, all heating being well known in the art for providing 
sufficient heat to fuse toner to its substrate. 
A preferred fuser assembly comprises a heated roll structure having a 
hollow core. The heated roll structure includes a hollow cylinder portion 
thereof which is coextensive with the cylinder. The heating element may 
comprise any suitable type heater for elevating the surface temperature of 
the cylinder to operational temperatures therefor, for example, 
200.degree.-450.degree. F. For example, it may be a quartz lamp. 
In one preferred working embodiment, the resulting fuser roll structure has 
an outside diameter on the order of 1.5 to 3.0 inches (3.8 to 7.6 cm.) and 
has a length on the order of 10 to 15 inches (25.4 to 38.1 cm.). Power 
requirements for the foregoing are 500-2500 watts peak power with an 
average power of 300-2000 watts and 75-250 watts for standby. The surface 
temperature of the fuser member structure may be controlled by contacting 
the surface thereof with a thermistor probe as described in U.S. Pat. No. 
3,327,096 issued to Bernous. 
The pressure roll or backup roll 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, 
may comprise any suitable construction, for example, a steel cylinder, but 
preferably comprises a rigid steel core having a Viton elastomer surface 
or layer thereon. A preferred backup roll has a core approximately 1.8 
inches (4.5 cm.) in diameter with a 0.1 inch (0.25 cm.) cover or layer 
structure of Viton elastomer or other suitable high temperature 
elastomeric layer structure, for example, silicone rubber and a 
combination of Viton or silicone rubber with Teflon thereon. Viton is the 
trademark of duPont Co. The specific dimensions of the members making up 
the backup roll will be dictated by the requirements of the particular 
copying apparatus wherein the fuser assembly is employed, the dimensions 
being greater or less depending upon the process speed of the machine. 
The thickness of the silicone rubber, the heat-resistant resin layer, 
and/or the thickness of the layer of primer or multiple layers of any or 
all of the foregoing, are not critical in the practice of the present 
invention. Generally where the fuser member is heated by internal means, 
the silicone rubber the heat resistant material and the optional primer 
material are preferably of such thicknesses as to constitute a minimal 
thermal barrier to heat radiating from inside the fuser member to the 
outermost layer of silicone rubber. Recommended combined thickness in this 
case ranges from about 1 mil (0.0025 cm.) to about 200 mils (0.5 cm.), the 
most preferred range being about 5 mils (0.12 cm.) to about 90 mils (0.22 
cm.). 
The advantages of the present invention were confirmed by comparative life 
tests wherein several fuser rolls having different kinds of roll 
configurations and silicone rubbers were used and are described in detail 
in the Examples. The fuser rolls having the structure as described 
hereinbefore were placed in a pressure contact fuser assembly of the type 
shown in FIG. 5. The various fuser rolls were substituted in the fuser 
assembly after the previous roll failed. 
The term "life" or "lifetime" as used herein refers to the number of 
reproduced copies until the heat-resistant, release layer of silicone 
rubber deteriorated in release characteristics resulting in off-set or 
winding of copying paper around the fuser roll in cases where no silicone 
oil is fed to the roll surface. In those tests where a silicone oil was 
used, the lifetime is defined as the number of reproduced copies until the 
heat-resistant, release layer of silicone rubber was either reduced in 
mechanical strength and had an irregular surface, or separated from the 
fuser roll core by the action of the silicone oil, which makes it 
impossible to continue the copying (fusing) operation. In tests where 
silicone oil was not used, the silicone oil-feeding system including the 
intermediate oil-feeding member 44, the roll 48, the silicone oil 46, the 
feeding roll 48, the container or sump 56 and the weight 52 were 
eliminated from the fuser assembly of FIG. 5. 
The following examples further define, describe and compare prior art fuser 
rolls and fuser rolls prepared by the present invention and illustrate the 
preferred embodiments of the present invention. 
EXAMPLE I 
For comparative testing, a conventional fuser roll of the type shown in 
FIG. 1 was made by applying a conventional self-adhesive single liquid RTV 
silicone rubber identified as KE-45RTV, a product of Shinetsu Chemical 
Co., onto the outer surface of a degreased aluminum core 1 in a thickness 
of 400 microns (15.75 mils) to form a heat-resistant, release material 
layer 2 around the core. The fuser oil was then mounted in the fuser 
assembly of FIG. 5 and subjected to the above lifetime test using no 
silicone oil. Failure occurred when a copying sheet (paper) wound around 
the roll after making 470 copies (fusing 470 copies). When the above 
process was repeated using a silicone oil metered onto the surface of the 
roll, the lifetime corresponded to 3,000 copies, at which point the 
heat-resistant release material layer 2 was separated from the aluminum 
core 1. 
EXAMPLE II 
A fuser roll was made in accordance with the present invention for 
comparing with the fuser roll of EXAMPLE I. This fusing roll was 
fabricated according to the structure shown in FIG. 3. Using an aluminum 
core identical to the one described in EXAMPLE I, core 1 was first 
subjected to a degreasing treatment, and a heat-resistant polyimide resin 
(Toraneese 2000, a product of Toray Co., Ltd) was applied to the core in a 
dry thickness of 50 microns, followed by baking at 120.degree. C for 3 
minutes and at 240.degree. C for an additional 15 minutes. Then the baked 
roll was covered with KE-45 RTV silicone rubber identical to that of 
EXAMPLE I to form a 400 micron heat-resistant, release layer 2 to obtain a 
fuser roll as shown in FIG. 3. This fuser roll was mounted in the fuser 
assembly of FIG. 5 for use as a heat fixing roll and subjected to the same 
lifetime test as in EXAMPLE I. 
When no silicone oil was used, paper wound around the roll after fusing 
almost the same number of copies as in the case of the rolls in EXAMPLE I. 
Use of silicone oil in the fuser assembly prolonged the life, and a total 
of 9600 copies were fused using the fuser roll of this invention before 
the release material layer separated from the core. 
EXAMPLE III 
For comparative testing, another conventional fuser roll of the type shown 
in FIG. 2 was made by applying onto the aluminum core 1, vinylperoxysilane 
(CH.sub.2 .dbd. CHSi[OOC(CH.sub.3).sub.3 ].sub.3) primer designated by 
numeral 3 in FIG. 2. Then 400 microns (15.75 mils) of a RTV silicone 
rubber identified as KE-12RTV, a product of Shinetsu Chemical Co., was 
applied to form a heat-resistant, release material layer 2 around the 
core. This fuser roll was subjected to a lifetime test in the fuser 
assembly of FIG. 5 without the use of any silicone oil. Failure occurred 
when a copying sheet (paper) wound around the roll after the reproduction 
of 16,500 copies. 
When the above process was repeated using a silicone oil metered onto the 
surface of the roll, the lifetime corresponded to 4,500 copies before the 
heat-resistant silicone rubber layer 2 separated from the core. 
EXAMPLE IV 
For comparative testing another prior art roll identical to that of EXAMPLE 
III was made using vinylperoxysilane primer except the silicone rubber 
layer was formed from KE-530U HTV, a HTV silicone elastomer supplied by 
Shinetsu Chemical Company. This fuser roll was subjected to a lifetime 
test in the fuser assembly of FIG. 5. 
The roll was not usable under conditions of feeding no silicone oil because 
toner offset occurred from the beginning. When silicone oil was fed to the 
roll, 6700 copies were fused before the silicone rubber layer 2 was 
separated from the roll core 1. 
EXAMPLE V 
Several heat fixing rolls of the type as shown in FIG. 4 were made 
according to the invention, using a heat-resistant resin layer 4, 
different kinds of heat-resistant resins such as a heat-resistant 
polyimide resin identified by the tradename Toraneese #2000; a heat 
resistant polyamideimide identified by the tradename Amoco AI and supplied 
by Amoco Chemical Co., Inc.; and a heat resistant polyimide identified by 
the tradename Pyer Enamel and supplied by E. I. duPont De Numours & Co. 
Inc., as heat-resistant releasing layer 2. Three kinds of vulcanization 
silicone rubbers were used, KE-13RTV, KE-53OU HTV and KE-555U HTV 
(products of Shinetsu Chemical Co.). The primer layer 3 was 
vinylperpoxysilane. The life test results using silicone oil are shown in 
Table I below: 
TABLE I 
______________________________________ 
Number of Copies Fused 
with with with 
heat heat heat 
resistant resistant resistant 
silicone silicone silicone 
rubber rubber rubber 
HEAT RESISTANT KE- KE-530U KE-555U 
RESIN USED 12RTV HTV HTV 
______________________________________ 
Toraneese #2000 
baking conditions: 
42000 46000 53000 
120.degree. C, 3 min and 
copies copies copies 
240.degree. C, 15 min 
Amoco AI Baking con- 
44000 46000 54000 
ditions: 200.degree. C, 1 hr 
Skygard 700 baking con- 
42000 45000 52000 
ditions: 200.degree. C, 1 hr 
Pyer enamel baking con- 
46000 47000 56000 
ditions: 200.degree. C, 1 hr 
______________________________________ 
As will be understood from the above results, the fuser rolls of the 
invention have a life several times longer than that of the prior art 
fuser rolls. In the foregoing examples, the fuser roll and the pressure 
roll each had an outer diameter of 30 mm. The silicone oil used was KF-96 
350 centistokes (product of Shinetsu Chemical Co.) and its feeding rate 
was 0.04 cc/copy. Further, the surface temperature of the fuser roll was 
controlled at 160.degree. C by changing a voltage fed to a tubular infra 
red lamp (rating: 100 V 1000 W) by a temperature control means (not 
shown). The toner employed was 2400 toner (product of Fuji Xerox Co.) and 
the copy paper was L-1 paper (product of Fuji Xerox Co.). 
From the foregoing experimental results, it can be seen that the improved 
life of the fuser rolls of this invention over the prior art rolls is 
mainly due to early adhesion failure between the roll core and the 
silicone rubber layer or between the primer layer and the roll core in the 
prior art fusers resulting from the application of heat and from the 
presence of silicone oil. In the improved fuser rolls of this invention 
wherein a heat-resistant resin layer such as a polyamide, polyamideimide 
or polyimide resin is provided either between the metal roll core and the 
self-adhesive silicone rubber or between the metal roll core and the 
primer, the strengths of adhesion between the metal roll core and the 
heat-resistant resin layer and also between the heat-resistant resin layer 
and the self-adhesive silicone rubber layer, or between the metal roll 
core and the heat-resistant resin layer and also between the 
heat-resistant resin layer and the primer layer, are greater than the 
ahesion strength between the metal roll core and the self-adhesive 
silicone rubber or between the metal roll core and the primer layer. 
In the practice of the invention, the silicone rubber layer may be made of 
a silicone rubber which has been impregnated with silicone oil since the 
heat-resistant resin layer has a strong adhesion even to such 
oil-impregnated silicone rubbers. 
The fuser rolls of this invention may be used either as the fuser roll or 
the pressure roll in a fusing assembly of the type using two heated fuser 
rolls. Further, the fuser rolls may be employed in a fusing assembly 
having an external heating source. 
As will be understood from the foregoing detailed description there is 
provided a fuser roll having a silicone rubber layer covering as a 
heat-resistant, release material strongly adhered to a metal roll core 
through a heat-resistant layer of a specified class of resins. The rolls 
of this invention are advantageous because the adhesion between the heat 
roll substrate and the silicone rubber layer did not fail even when a 
silicone oil was used as offset preventing liquid on the fuser roll, and 
the fuser rolls of the invention have a longer life than the prior art 
fuser rolls. 
The silicone rubbers useful in this invention are conventional commercial 
rubbers described above. The silicone rubbers or elastomers may be 
cross-linked on the fuser member by techniques well known in the art, such 
as with benzoyl peroxide or other free radical initiators, with or without 
catalyst. Conventional techniques may be used to vulcanize the HTV, RTV, 
or LTV silicone rubbers on the roll surface. Conventional application of 
the layers to the base member can be used to form the fuser member. These 
techniques are well known by one skilled in the art. 
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.