Note: Descriptions are shown in the official language in which they were submitted.
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PRESSURE-FIXING APPARATUS
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Field of_the Invention
This invention relates to electrostatic duplicat-
ing or copying apparatuses and processes. More particular-
ly, this invention relates to the pressure-fixing of
imaging powders to a receptor, such as a sheet of paper,
and provides apparatuses and methods for fixing such powders
to such a receptor. The resultant copies have substantially
reduced gloss in image and background areas. Additionally,
the images are firmly anchored to the receptor.
Electrostatic copying processes generally comprise
the steps of electrostatically charging a photosensitive
substrate, ~mage-wise exposing the charged substrate to a
graphic original, developing the charged image areas with
image powder, and then fixing the powder.
Two types of processes, the "transfer process"
and the "direct process", are well known. In the "transfer
process", a permanent photosensitive substrate is employed
and the developed image areas are transferred from it to
an expendable receptor, such as paper, where the toner is
then permanently fixed. In the "direct process" the
substrate and the receptor are the same and comprise an
expendable electrostatic copy paper to which the developed
image is fixed without transfer. The present invention
provides apparatuses and methods for pressure fixing imaging
powders in both of these processes.
Pressure-fixable imaging powders become affixed
to a receptor by the application of a minimum fixing
pressure. Consequently, an apparatus which fixes imaging
powders to a receptor by application of pressure must be
capable of exerting sufficient pressure on the powder to
exceed the minimum fixing pressure and cause the particles
to coalesce and bond thereto. Generally pressure is
applied by a pair of steel rolls known as "fusing rolls".
The fusing rolls employed in the first pressure-
fixing apparatuses had fine (i.e., smooth) surface finishes.
The fine surface finish in combination with the fixing
pressures necessary to cause the developing powder
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particles to coalesce resulted in copies that had shiny
(i.e., glossy) image and background areas. This made the
copies difficult to read and aesthetically unpleasant
in appearance.
Many attempts were made to eliminate these
problems. One approach was to reduce the amount or
pressure applied to the fixing rolls. This, however, was
not entirely satisfactory. Thus, while the non-imaged
(i.e., background) areas exhibited some reduction in
gloss, the imaged areas exhibited virtually no reduction
in gloss. Additionally, the imaged areas were less
permanently fixed to the receptor surface.
Other attempts to eliminate these problems have
also been made. Thus see U.S. Patent Nos. 3,854,975 and
3,874,894. In 3,854,975, two cylindrical pressure members
are employed. The pressure member that contacts the
unfixed image is a hard surfaced metal roll whose surface
is preferably smooth and non-porous. The other pressure
member preferably has a surface that is softer and more
compliant.
In 3,874,894, two cylindrical pressure members
are also employed. The pressure member that contacts the
unfixed image areas has a smooth and deformable surface.
The other pressure member has a surface which is at least
as hard as that of the first.
These approaches have not proven entirely
satisfactory because the imaged surface still exhibits
relatively high gloss.
Still other attempts to solve this problem are
disclosed in German Patent Publication 28 23 359 published
June 13, 1979, and German Patent Publication 29 11 526
published September 27, 1979. These documents disclose
pressure fixation devices that employ a pair of pressure
members wherein the member that contacts the unfixed image
areas has an irregular surface.
In the former German patent publication the
irregularly surfaced pressure member comprises minute
rounded peaks. This pressure member is said to contact
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the other pressure memberO However, this publication further discloses
that if there is nothing between the members, the rounded peaks will be
worn away by the continued contact of the members. Consequently, it is
preferred, for practical use, that the members be maintained in a spaced
apart relationshipD This, however, places limitations upon the physical
configuration of the pressure-fixing device relative to the degree of skew
that can be utilized with the pressure members. Additionally, it is clear
that the two members each have hard, non-compliant surfacesO
In the ]atter German patent publication the surface of both
pressure members is hardO The member that contacts the image areas has
an "aventurine-like" surfaceO This surface is prepared by sandblasting a
surface and then treating the surface with steel ballsO The other pressure
member has a hard surface which may, if desired, be "aventurine-like"O
Another attempt to solve the gloss problem is described in
United States Patent NoO ~,290,691 dated September 22, 1981 (No L. Giorgini)O
This patent describes a pressure fixing device that employs two textured
pressure members. The one that contacts the unfixed images has a
compliant surface while the other pressumre member has a non-compliant
surfaceO
Copies produced from this apparatus have low gloss;in both
image and background areasO Furthermorel the images are firmly fixed to
the receptorO However, it has been found that the present invention
provides even lower gloss copies while s~ill firmly anchoring the images
to the receptor.
Disclosure of Invention
In one aspect, the present invention provides an apparatus for
fixing unfixed image areas of pressure-fixable imaging powder on an imaged
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surface of a receptor that comprises
a) first and second pressure members that have skewed
longitudinal axis with respect to each other and that contact each other
along a narrow nip, wherein,
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said first pressure member has an Irregular,
non-compliant surface comprising a plurality of
randomly sized~ domed projections that contact
the imaged surface of said receptor and wherein
said second pressure member has a compliant
surface that contacts the non-imaged surface of
said receptor; and
b) means for rotating said first and second
pressure members so that said receptor is transported
through said nip.
In another aspect, the present invention provides
a method of fixing pressure-fixable imaging powder on the
surface of a receptor comprising the steps of:
a) forming an imaged surface that comprises
areas of unfixed pressure-fixable imaging powder on the
surface of a receptor; and
b) passing said receptor through the nip formed
by first and second contacting pressure members to fix said
image areas to said receptors, said pressure members being
rotated so that said receptor is transported therethrough,
wherein said pressure members are as described above.
Brief Description of the Drawings
The present invention is described in greater
detail hereinafter with reference to the accompanying
drawings wherein like reference characters refer to the
same elements in the several views and wherein:
Figure 1 is a perspective view of an apparatus
according to the present invention;
~ Figure 2 is a cross sectional view of the pressure
members shown in Figure 1 showing an exaggerated degree of
depression of the compliant pressure roll;
Figure 3 is an enlargement of a section of the
surface of the non-compliant pressure member of Figure 1
showing the domed projections, and
Figure 4 is an enlarged cross sectional view of
a portion of the non-compliant roll of Figure 2.
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Detailed Description
The present invention is based upon the discovery
that the co~bination of a first pressure member (sometimes
referred to hereinafter as a fixing member or fixing roll)
that has an irregular, non-compliant surface and a second
pressure menlber (sometimes referred to hereinafter as a
back-up member or back-up roll) that has a compliant surface
provides low gloss in image and background areas on a
receptor surface while at the same time firmly anchoring
the imaging powder to the receptor surface. Surprisingly,
the combination of the non-compliant pressure roll with the
compliant back-up roll has extended life even though the
two rolls are in contact with each other when no receptor
is passing therebetween~ Apparently, the compliant back-
up roll acts as a cushion thereby substantially eliminatingwear on the non-compliant pressure roll and also preventing
the domed projections from being crushed.
Preferably the pressure members are cylindrical
rolls that each have a substantially circular cross-section.
Additionally, it is preferred that the non~compliant
surface of the first pressure membe-r comprise a plurality
of sharp peaks that have been coated with a layer of non-
compliant material having a thickness in the range of from
about 0.01 to 0.1 mm, and most preferably from about
0.015 to 0.08 mm, so as to provide said randomly sized
domed projections. It is also preferred that these sharp
peaks be coated with chrome.
The compliant surface of the second pressure
member preferably is smooth and comprises a material such
as nylon. However, it may be irregular if desired.
Referring now specifically to the figures, Figure
1 illustrates an apparatus 2 for pressure-fixing imaging
powder in imaged areas. The apparatus 2 comprises a first
cylindrical pressure roll 3 and a second cylindrical pressure
roll 4. Roll 3 has an irregular, non-compliant surface
that comprises a plurality of randomly sized domed
projections 5 (see Figures 3 and 4). Roll 4 has a
compliant surface. Rolls 3 and 4 are preferably held in
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position by means of a split journal box that comprises an
upper section 6 and a lower section 7. Pin 8 is provided
in upper section 6 so that upper section 6 may be pivoted
tfierearound to permit separation of the two sections,
This permits rolls 3 and 4 to be removed if desired. Bear-
ings 9 are also provided in each of section 6 and 7, Means
for rotating rolls 3 and 4 are also provided so that a
receptor may be transported through these rolls~ These
means are not shown.
Pressure adjusting means are also provided on
the journal box. They comprise threaded posts 10, nuts 11
and spring 12. In operation, nuts 11 are tightened on
posts 10 until the desired degree of compression is obtain-
ed in springs 12.
Figure 1 further shows a receptor 13 that has
unfixed image areas 14 and fixed image areas 15 thereon.
The receptor 13 is situated with respect to apparatus 2
such that fixing roll 3 contacts the unfixed image areas
14 thereby forming fixed image areas 15, Back-up roll
4 contacts the unimaged surface of receptor 13~ Fixing
roll 3 and back-up roll 4 rotate in opposite directions
with respect to each other as is shown by arrows 1 so that
receptor 13 is transported through apparatus 2,
As can be seon from Figures 2 and 4, fixing roll
3 comprises a rigid core 16 that has a non-compliant layer
17 therearound, Core 16 may be selected from any rigid and,
preferably, non-compliant material. Metallic materials,
sucK as steel, are especially useful.
Non-compliant layer 17 covers core 16 and provides
an irregular surface that comprises a plurality of randomly
sized domed projections, This layer is preferably in the
range of from about 0,01 to 0,1 mm thick. Most
preferably, the material of layer 17 is chrome, Layer 17
covers a surface of sharp peaks 18 on roll 3 (see Figure 4).
This layer provides the plurality of randomly sized domed
projections 5 shown in enlarged size in Figure 3,
Roll 3 may be prepared by conventional processing
technigues~ Thus, for example, a rigid, preferably non-
compliant, cylindrical roll (such as a steel roll7 may have
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its surface roughened by, for example, sand blasting with
100 grit abrasive material This provides the plurality of
sharp peaks 18 shown in Figure 4. This rough surface is
then coated with a non-compliant material so as to provide
the randomly sized domed projections 5~ This may be done
by conventional plating techniques using conventional
plating materials, Preferably the plating material is
chrome.
Figure 2 further shows that back-up roll 4 is
preferably made up of a layer or sheath 19 of a compliant
material over a central core 20 Layer 19 may be selected
from any compliant material and is commonly an organic
polymeric substance. A particularly useful material for
use as layer 19 is nylon, especially nylon-66 Core 20
is a rigid, and preferably, non-compliant material. A
variety of materials are useful as core 20, Preferably
core 20 is selected from a metallic material such as steel.
Other ingredients may be incorporated into the
sheath 19 of compliant material. Thus, for example, glass
filled nylon may be employed if desired. Such materials
are useful when the characteristics of the imaging powder
and the paper to which the imaging powder is to be fixed
are such that the amount of pressure required for imaging
would normally induce compression set in the sheath of
compliant material. Other compliant materials that may be
employed to provide the compliant surface of roll 4 include
hard rubber, and acetal resins.
In operation, an image comprising a plurality of
unfixed pressure fixable imaging powder particles is formed
on the surface of a suitable receptor. The receptor is then
passed between the first and second contacting pressure
members (that fs between rolls 3 and 4) to fix the imaged
areas to the receptor. The first pressure member contacts
the imaged surface of the receptor while the second pressure
member contacts the unimaged surface of the receptor.
Preferably the pressure members are driven so that the
receptor is transported through the nip of contact formed
between the two pressure members. The resultant copy
demonstrates superior quality in that the copy does not have
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a slick, glossy finish either in background or image areas.
Consequently, the imaged surface is easy to read and
aesthetically pleasing.
The present invention is further described in the
following examples.
EXAMPLES 1-2
The gloss produced on paper receptors processed
according to the method and using the apparatus of the
present invention was compared with the gloss produced on
paper receptors processed according to conventional
techniques and using known equipment.
The photocopier employed in this example was
VQC III LDC copier from 3M Company. The paper receptor
employed was Type 3706 paper available from 3M Company.
The toner powder employed was Type 371 pressure f~xable
toner from 3M Company.
When the present invention was used to prepare
the copies (see Example 1), the standard fixing station of
the copier was replaced with the device of the invention.
When the known techniques and equipment were employed
(See Example 2), the standard VQC III LDC fixing station
was employed. This fixing station utilized smooth steel
rolls.
Three separate paper receptors were processed
through each machine. The first receptor was a plain
white sheet. No toner was applied to it. This demonstrated
the background gloss imparted to the receptor. The second
receptor was toned over essentially one entire surface with
toner powder and then passed through the fixing station.
This demonstrated the image gloss imparted to the receptor.
The third sheet was an imaged sheet containing toned image
areas and untoned background areas.
After the copies were made, the gloss of the
first and second receptors was determined with a Hunter Lab
Model D-16 Multipurpose Gloss Meter available from Hunter
Associates Laboratories Incorporated of Fairfax, Virginia.
The angle of the incident light was 75 from vertical. The
technique for measuring gloss is described in the Technical
association of Pulp and Paper Industries test method
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T-48000s-72,
The gloss values obtained are given in Table 1.
High gloss values indicate high gloss (i.e., a shiny and
reflective surface) on the copy.
TABLE 1
EXAMPLE RECEPTOR GLOSS
1 First (White) 11
Second (Black~ 12
2 First (White) 22
Second (Black) 43
This data clearly demonstrates the unexpected
results achieved by practice of the present invention~
Thus, the first and second receptors of Example 1 had a
matte-like finish as is shown by their low gloss values.
The first and second receptors of Example 2, on the
other hand, had a shiny finish as is clearly shown by their
high gloss values.
The third receptors of each Example even more
clearly illustrate the dramatic reduction in gloss achieved
by the process and apparatus of the present invention~
Thus, the third receptor of Example 1 had a flat appearance
(i.e., it did not reflect a great deal of light) and was
easy to read. However, the third receptor of Example 2 had
a glossy appearance (i.e., it reflected a great deal of
light) and was difficult to read.
The preceding disclosure describes the more
preferred aspects of the present invention. However, minor
variations of the invention are possible and will be obvious
to those skilled in the art as a result of this disclosure.
3Q These variations are included within the scope of the
accompanying claims.
