[0001] This invention relates generally to an apparatus and method for image fusing in an
ink jet printing system and, more specifically, to an apparatus and method that utilize
separate image transfer and image fusing operations for improved fusing of an ink
image into media.
[0002] Ink jet printing involves ejecting ink droplets from orifices in a print head onto
a receiving surface to form an image. The image is made up of a grid-like pattern
of potential drop locations, commonly referred to as pixels. The resolution of the
image is expressed by the number of ink drops or dots per inch (dpi), with common
resolutions being 300 dpi and 600dpi.
[0003] Ink-jet printing systems commonly utilize either direct printing or offset printing
architecture. In a typical direct printing system, ink is ejected from jets in the
print head directly onto the final receiving substrate. In an offset printing system,
the image is formed on an intermediate transfer surface and subsequently transferred
to the final receiving substrate. The intermediate transfer surface may take the form
of a liquid layer that is applied to a support surface, such as a drum. The print
head jets the ink onto the intermediate transfer surface to form an ink image thereon.
Once the ink image has been fully deposited, the final receiving substrate is then
brought into contact with the intermediate transfer surface and the ink image is transferred
to the final receiving substrate.
[0004] U.S. Patent 5,389,958 entitled IMAGING PROCESS and assigned to the assignee of the
present application (the '958 patent) is an example of an indirect or offset printing
architecture that utilizes phase change ink. The intermediate transfer surface is
applied by a wicking pad that is housed within an applicator apparatus. Prior to imaging,
the applicator is raised into contact with the rotating drum to apply or replenish
the liquid intermediate transfer surface.
[0005] Once the liquid intermediate transfer surface has been applied, the applicator is
retracted and the print head ejects drops of ink to form the ink image on the liquid
intermediate transfer surface. The ink is applied in molten form, having been melted
from its solid state form. The ink image solidifies on the liquid intermediate transfer
surface by cooling to a malleable solid intermediate state as the drum continues to
rotate. When the imaging has been completed, a transfer roller is moved into contact
with the drum to form a pressurized transfer nip between the roller and the curved
surface of the intermediate transfer surface/drum. A final receiving substrate, such
as a sheet of media, is then fed into the transfer nip and the ink image is transferred
to the final receiving substrate.
[0006] To provide acceptable image transfer and final image quality, an appropriate combination
of pressure and temperature must be applied to the ink image on the final receiving
substrate. US Patent No 5,777,650 entitled PRESSURE ROLLER and assigned to the assignee
of the present application discloses a roller for fixing an ink image on a final receiving
substrate. The preferred embodiment of the roller is described in the context of an
offset ink jet printing apparatus similar to the one described in the '958 patent.
In this embodiment, the final receiving medium is preheated to a preferred temperature
of about 63° C and the pressure in the transfer nip is preferably about 1150 psi (7,929
kPa). Additionally, the speed of the final receiving medium through the transfer nip
is approximately five inches/sec. (13cm./sec.).
[0007] In a color printing system, the ink image on the final receiving surface is composed
of individual drops of ink that form primary and secondary colors. The primary and/or
secondary colors may include two or more drops of ink placed on top of one another.
In the image transfer process, the ink image is transferred from the drum to the final
receiving substrate. A portion of the ink image is fused or pressed into the final
receiving substrate. The height of the remaining ink that lays above the surface of
the final receiving substrate is referred to as the "ink pile height."
[0008] The ink pile height of an image affects the "look and feel" of the image. In general,
a lower ink pile height is preferred, as the appearance of the image will more closely
resemble an image created by a commercial web press. The ink pile height also affects
the ability of a user to write on the image. In images having ink pile heights approaching
1 x 10
-3 in., and higher, the tip of a writing instrument will often furrow through the ink
"pile." This can hinder the flow of writing ink through a ball point pen, or prevent
the graphite writing surface of a pencil from contacting and marking the receiving
substrate. Additionally, depending upon the composition of the ink used in the printer,
ink pile height can hinder media from being transported through an automatic document
feeder in a photocopier.
[0009] In the prior art offset phase change ink printers, such as the printer described
in the '958 patent, the ink pile height of images on the final receiving surface ranges
from about 1 x 10
-5 inch for a single pixel primary color to about 1 x 10
-3 in. for a solid fill secondary color. By comparison, a liquid ink jet printer using
a direct printing process and an aqueous-based ink produces images having a negligible
ink pile height of less than 1 x 10
-5 inch.
[0010] In the image transfer process described above for the '958 patent, higher temperatures
and pressures in the transfer process will generally yield lower ink pile heights.
However, higher pressures in the transfer process also increase the loadings on the
pressure roller, support surface or drum and other printer components. This accelerates
wear on these components and tends to limit the maximum printing speed of the apparatus.
Increased nip temperatures can inhibit duplex printing and cause the ink image to
partially liquify and smear. These undesirable effects are magnified in an offset
printing system in which the image transfer process is performed continuously; that
is, the support surface or drum is under continuous loading and a high nip temperature
is maintained. Thus, a need remains for an image fusing system that reduces ink image
pile height, allows faster print speeds, reduces the transfer nip pressure and overcomes
the other drawbacks of the prior art.
[0011] It is an aspect of the present invention to provide an apparatus and related method
for image fusing in an ink jet printing system.
[0012] It is another aspect of the present invention that the apparatus and method utilize
separate image transfer and fusing operations for improved fusing of an ink image
into media.
[0013] It is a feature of the present invention that the apparatus and method allow faster
print speeds by utilizing separate image transfer and fusing operations.
[0014] It is another feature of the present invention that the fusing operation may be utilized
to apply a coating to the final receiving substrate.
[0015] It is yet another feature of the present invention that the apparatus and method
are capable of producing images having an ink pile height of 7 x 10
-4 inch and less.
[0016] It is an advantage of the present invention that the apparatus and method reduce
the loading on the drum and transfer roller by using lower pressures in the image
transfer operation.
[0017] It is another advantage of the present invention that the apparatus and method are
capable of reducing the ink pile height in images for better image durability and
improved writability.
[0018] To achieve the foregoing and other aspects, features and advantages, and in accordance
with the purposes of the present invention as described herein, an apparatus and related
method for improved image fusing in an ink jet printing system are provided. An ink
image is transferred to a final receiving substrate by passing the substrate through
a transfer nip. The substrate and ink image are then passed through a fusing nip that
fuses the ink image into the final receiving substrate. By utilizing separate image
transfer and fusing operations, improved image fusing is possible without compromising
print speed. The secondary fusing operation enables the image transfer process to
use reduced pressures, whereby the load on the drum and transfer roller is reduced.
Additionally, the secondary fusing operation may be utilized to apply a supplemental
coating to the transferred image.
[0019] Nip pressures that may be utilised in the image transfer step are generally less
than about 13.79 x 10
6 Pa (2000psi), preferably less than about 5.52 x 10
6 Pa (800psi), more preferably about 69 x 10
3 Pa (10 psi) to about 4.83 x 10
6 Pa (700 psi), still more preferably about 689 x 10
3 Pa (100 psi) to 4.14 x 10
6 Pa (600 psi), and most preferably about 1.38 x 10
6 Pa (200 psi) to about 4.14 x 10
6 Pa (600psi)
[0020] Nip pressures that may be utilised in the image fusing step are generally less than
about 27.58 x 10
6 Pa (4000psi), preferably about 2.76 x 10
6 Pa (400psi) to about 13.79 x 10
6 Pa (2000psi), more preferably about 3.45 x 10
6 Pa (500psi) to about 6.89 x 10
6 Pa (1000psi), and most preferably about 4.14 x 10
6 Pa (600psi) to about 6.89 x 10
6 Pa (1000 psi).
[0021] The following description is intended to illustrate the invention, by way of example
only, reference being made to the accompanying drawings in which:
[0022] Fig. 1 is a diagrammatic illustration of a multiple print head offset ink jet printing
apparatus that utilizes the apparatus and method of the present invention.
[0023] Fig. 2 is an enlarged diagrammatic illustration of the transfer of the inked image
from the liquid intermediate transfer surface to a final receiving substrate.
[0024] Fig. 3 is a diagrammatic illustration of the secondary fusing operation of the present
invention showing the final receiving substrate passing through the fusing nip.
[0025] Fig. 1 is a schematic illustration of a multiple print head, offset or indirect ink
jet printing apparatus 10 that utilizes the secondary fusing method and apparatus
of the present invention. The printing apparatus 10 is more fully disclosed in copending
European Patent Application No (not yet assigned; attorney reference APEP98048) entitled
PHASE CHANGE INK PRINTING ARCHITECTURE SUITABLE FOR HIGH SPEED IMAGING and assigned
to the assignee of the present application. This Application is hereby specifically
incorporated by reference in pertinent part.
[0026] The following description of a preferred embodiment of the fusing method and apparatus
of the present invention refers to its use in this type of printing apparatus. It
will be appreciated, however, that the method and apparatus of the present invention
may be used with various other printing apparatus that utilize different imaging technologies
and/or architectures, such as direct ink jet printing in which ink drops are ejected
directly onto a receiving substrate. Accordingly, the following description will be
regarded as merely illustrative of one embodiment of the present invention.
[0027] The imaging apparatus 10 in Fig. 1 utilizes an offset printing process to place a
plurality of ink drops in imagewise fashion on a final receiving substrate. In the
preferred embodiment, the apparatus 10 includes 16 print head modules 12A - 12N, 12P
and 12Q positioned around a support surface or drum 14. With reference now to Fig.
2, the print head modules jet drops of ink 23, 25 in a molten or liquid state onto
an intermediate transfer surface 9 on the drum 14. The intermediate transfer surface
9 is preferably a liquid layer that is applied to the drum 14 by contacting the drum
with an applicator assembly 16 (See Fig. 1). Suitable liquids that may be used as
the intermediate transfer surface include water, fluorinated oils, glycol, surfactants,
mineral oil, silicone oil, functional oils and combinations thereof. The preferred
liquid is amino silicone oil.
[0028] As shown in Fig. 1, the applicator assembly 16 includes a reservoir 18, a wicking
pad 20 for applying the liquid and a metering blade 22 for consistently metering the
liquid on the surface of the drum 14. Wicking pad 20 is preferably formed from any
appropriate nonwoven synthetic textile with a relatively smooth surface. A preferred
configuration can employ the smooth wicking pad 20 mounted atop a porous supporting
material, such as a polyester felt. Both materials are available from BMP Corporation
as BMP products NR 90 and PE 1100-UL, respectively. The metering blade meters the
liquid to have a thickness of from about 0.025 microns to about 60 microns, and more
preferably from about 0.05 to about 10 microns. To allow continuous imaging and printing,
the wicking pad 20 and blade 22 are continuously in contact with the drum 14. The
reservoir 18 may also be supplied by a separate liquid supply system (not shown) to
insure an uninterrupted supply of liquid.
[0029] The support surface may take the form of a drum 14 as shown in Fig. 1, or alternatively
may be a belt, web, platen, or other suitable design. The support surface 14 may be
formed from any appropriate material, such as metals including, but not limited to,
aluminum, nickel or iron phosphate, elastomers, including but not limited to, fluoroelastomers,
per fluoroelastomers, silicone rubber and polybutadiene, plastics, including but not
limited to, polytetrafluoroethylene loaded with polyphenylene sulfide, thermoplastics
such as polyethylene, nylon, arid FEP thermosets such as acetals or ceramics. The
preferred material is anodized aluminum.
[0030] With continued reference to Figs. 1 and 2, liquid or molten ink is ejected from the
print head modules 12A - 12N, 12P and 12Q onto the intermediate transfer surface 9
on the drum 14 to form an ink image thereon. A final receiving substrate or media
11 is fed through a preheater 30 and into a transfer nip 32 formed between the drum
14 and a transfer roller 34. The preheater 30 preheats the media 11 to a temperature
of between about 50° C to about 100° C and preferably to about 70° C. In the preferred
embodiment, the transfer roller 34 has a metallic core, preferably steel, with an
elastomeric covering 15 having a 40 - 45 Shore D rating (see Fig. 2). Suitable elastomeric
covering materials include silicones, urethanes, nitriles, EPDM and other appropriately
resilient materials. With reference now to Fig. 2, the elastomeric covering 15 on
roller 34 engages the media 11 on the side opposite to the side to which the ink image
is transferred from the exposed surface of the intermediate transfer surface 9. As
explained in more detail below, as the media 11 passes through the nip 32, it is pressed
against the deposited ink image to transfer the ink image to the media.
[0031] The pressure exerted on the ink image/media 11 within the transfer nip 32, in combination
with the temperature of the ink image and media 11 and the residence time of the media
within the nip, should be sufficient to insure that the ink image is fully transferred
to the media 11. Figure 2 diagrammatically illustrates the sequence involved when
drops of ink 23, 25, 27 and 29 forming a portion of the ink image are transferred
to the final receiving substrate 11. In the preferred embodiment, the drum 14 and
the transfer roller 34 have a length of about 14 inches (35 cm.), and the width of
the transfer nip is between about 0.020 in. (0.508 mm.) and about 0.140 inch (3.553
mm.), and more preferably between about 0.070 in. (1.777 mm) and about 0.090 inch
(2.28 mm.). The force urging the transfer roller 34 into contact with the drum 14
is between about 100 lbf. (445 N.) and about 800 lbf. (3558 N.), and preferably about
700 lbf. (3114 N.). Thus, for a transfer nip width of 0.090 in. (2.28 mm.), the preferred
nip pressure is about 556 psi (3.83 X 10
6 Pa.).
[0032] With reference now to Figure 1, the liquid intermediate transfer surface 9 on the
surface of drum 14 and the ink image deposited thereon are maintained within a predetermined
temperature range by an appropriate heater device 28. Heater device 28 may be a radiant
heater positioned as shown or, alternatively, positioned internally within the drum
14. Heater device 28 increases the temperature of the drum 14/ liquid intermediate
transfer surface 9 from ambient temperature to between about 25° C and about 100°
C or higher. This temperature is dependent upon the exact nature of the liquid employed
in the intermediate transfer surface 9, the composition of the ink forming the ink
image and other parameters of the printing process. Using amino silicone oil as the
intermediate transfer surface and the preferred ink described below, a more preferred
temperature range for the drum 14/liquid intermediate transfer surface 9 is between
about 45° C to about 90° C, with the most preferable temperature being about 65° C.
[0033] In the preferred embodiment, a phase change ink is utilized in the printing apparatus
10. The phase change ink is initially in solid form and is then changed to a molten
state by the application of heat energy to raise the temperature to between about
85° C and about 150° C. The molten ink is then applied in raster fashion from the
nozzles 42 in the print head modules 12A-12N, 12P and 12Q to the exposed surface of
the liquid intermediate transfer surface 9. The ink cools to an intermediate temperature
and solidifies to a malleable state in which it is transferred to the final receiving
substrate 11 via the transfer nip 32. This intermediate temperature where the ink
is maintained in its malleable state is between about 30° C and about 80° C, and preferably
about 65° C.
[0034] The ink used to form the ink image preferably has fluidic and mechanical properties
that meet the parameters needed for high speed indirect printing at speeds of 100
ppm and higher. In particular, the viscosity of the ink in a molten state must be
matched to the requirements of the print head modules utilized to apply it to the
intermediate transfer surface 9. The viscosity of the molten ink must also be optimized
relative to other physical and rheological properties of the ink as a solid, such
as yield strength, hardness, elastic modulus, loss modulus, ratio of the loss modulus
to the elastic modulus, and ductility. Additionally, the hardening time required for
the molten ink drops on the intermediate transfer surface 9/drum 14 to reach a malleable
state suitable for transfer must be sufficiently short to support the desired printing
speed.
[0035] A preferred phase change ink is comprised of a phase change ink carrier composition
admixed with a phase change ink compatible colorant. More specifically, the preferred
phase change ink carrier composition comprises an admixture of (1) at least one urethane
resin; and/or (2) at least one mixed urethane/urea resin; and (3) at least one mono-amide;
and (4) at least one polyethylene wax. A more detailed description of the preferred
phase change ink is found in European Patent Application No 99 300521.4.
[0036] This application is hereby specifically incorporated by reference in pertinent part.
[0037] It will be appreciated that many other types of phase change inks having various
compositions may be utilized with the printing apparatus 10 in practicing the method
and apparatus of the present invention as described herein. Examples of suitable alternative
phase change inks are described in U.S. Patent Nos. 4,889,560 (the '560 patent) and
5,372,852 (the '852 patent). The '560 patent and '852 patent are hereby specifically
incorporated by reference in pertinent part. The inks disclosed in these patents consist
of a phase change ink carrier composition comprising one or more fatty amide-containing
materials, preferably consisting of a mono-amide wax and a tetra-amide resin, one
or more tackifiers, one or more plasticizers and one or more antioxidants, in combination
with compatible colorants.
[0038] Returning to Fig. 1 and in an important aspect of the present invention, after the
media 11 passes through the transfer nip 32 and the ink image is transferred to the
media, the ink image is fused into the media by passing the media through a secondary
fusing nip 39 downstream from the transfer nip. With reference now to Fig. 3, after
passing through the transfer nip 32, the media 11 and ink image are first heated by
a fusing preheater 50 to a temperature of between about 50° C and about 100° C, and
more preferably to between about 65° C and about 70° C. The media 11 then passes through
the secondary fusing nip 39.
[0039] The secondary fusing nip 39 is formed by a first fuser roller 36 and a second fuser
roller 38. First and second radiant heaters 37, 41 are used to maintain the first
and second fuser rollers 36, 38, respectively, within a predetermined temperature
range. First and second IR thermocouples 35, 55 monitor the temperature of the first
and second fuser rollers 36, 38, respectively. Preferably, the first and second fuser
rollers 36, 38 are maintained between about 50° C and about 100° C, and more preferably
between about 65° C and about 70° C.
[0040] The first fuser roller 36 is driven to rotate at the same speed as the drum 14. In
the preferred embodiment, the first fuser roller 36 is fabricated from a metal, such
as steel, to provide a sufficiently hard contact area within the fusing nip 39. The
second fuser roller 38 is a passive roller that is driven by contact with the powered
first fuser roller 36. Preferably, the second fuser roller 38 includes a hard inner
core 52 and an elastomeric outer layer 54 having a durometer of about 85 Shore A.
The outer elastomeric layer 54 gives the second fuser roller 38 a measure of compliance
and allows for the creation of a wider fusing nip 39, as described below. Suitable
elastomeric covering materials include silicones, urethanes, nitriles, EPDM and other
appropriately resilient materials.
[0041] The second fuser roller 38 is biased into contact with the first fuser roller 36
to create the fusing nip 39. In the preferred embodiment, each end of the second fuser
roller 38 is attached to a moving linkage that is actuated by two pneumatic cylinders.
A portion 56 of the linkage and a pneumatic cylinder 58 are schematically shown in
Fig. 3. It will be appreciated that other means for biasing the second fuser roller
38 into contact with the first fuser roller 36 may be utilized, including, but not
limited to, solenoids, motors and hydraulic cylinders.
[0042] In an important aspect of the present invention, the pressure and temperature in
the secondary fusing nip 39 combines with the pressure and temperature in the transfer
nip 32 to fuse the ink image into the media 11 and achieve an improved ink pile height
in the final image. In the preferred embodiment, the force urging the second fusing
roller 38 into contact with the first fusing roller 36 is between about 400 lbf (1779
N.) and about 2000 lbf (8896 N.), and is preferably about 720 lbf. (3203 N.). The
preferred width of the fusing nip 39 is between about 0.035 in. (0.888 mm.) and about
0.150 in. (3.807 mm.), and more preferably between about 0.085 in. (2.157 mm.) and
about 0.100 in. (2.538 mm.). The first and second fusing rollers 36, 38 have a preferred
length of about 14 in. (35 cm.). Thus, for a fusing nip width of 0.085 in. (2.157
mm.), the preferred nip pressure is about 605 psi (4.17 X 10
6 Pa.).
[0043] As described above, the fusing preheater 50 heats the media 11 and ink image to a
preferred temperature of between about 65° C and about 70° C. In the preferred operation
of the printing apparatus 10, the speed of the media 11 through the transfer nip 32
and secondary fusing nip 39 is preferably about 15 in./sec. (ips) (38 mm./sec.). Advantageously,
and in an important aspect of the present invention, the preferred combination of
the pressures, temperatures and media speed recited above allow the secondary fusing
nip 39 to fuse the ink image into the media 11 to achieve an ink pile height of about
7 x 10
-4 in. (0.0178 mm.) or less. It has been observed that images having ink pile heights
of 7 x 10
-4 in. and less have an improved appearance as compared with images from prior art ink
jet printers that produce ink pile heights of greater than 7 x 10
-4 in. Additionally, images having ink pile heights of 7 x 10
-4 inch and less embody improved writability and travel more effectively through an
automatic document feeder.
[0044] In another important advantage of the present invention, utilizing separate nips
for transferring and fusing the ink image allows the transfer nip to utilize a lower
pressure and temperature. Advantageously, by utilizing a lower pressure within the
transfer nip 32, less force is exerted by the transfer roller 34 on the drum 14 during
the imaging process. This reduces the possibility of the transfer roller 34 introducing
position errors resulting in misalignment between the drum 14 and the print head modules
12A-12N, 12P and 12Q, particularly in the Y-axis direction. In this manner, the present
invention allows for greater consistency in image quality. This advantage is especially
important in printing systems that image, transfer and fuse simultaneously and continuously,
such as the apparatus 10 described in the present application. In these systems the
drum 14 is under constant load from the transfer roller 34, and reducing the load
on the drum substantially reduces wear on the drum components and the power required
to rotate the drum.
[0045] While the invention has been described above with references to specific embodiments
thereof, it is apparent that many changes, modifications and variations in the materials,
arrangements of parts and steps can be made without departing from the inventive concept
disclosed herein. For example, while the preferred embodiment is described in connection
with a multiple print head ink jet printer that utilizes phase change ink, it is to
be understood that the invention may be practiced with other ink jet printing architectures
and with other types of inks, such as aqueous-based and solvent-based inks.
[0046] A release agent may be applied to the first fuser roller to prevent the ink image
from adhering to the first fuser roller. Preferably, the release agent is applied
by contacting the first fuser roller with a liquid impregnated surface.
[0047] Using the method and apparatus of the present invention, it is also possible to apply
a coating to the final receiving substrate when it passes through the second nip.
1. A method of offset printing in an ink jet printer (10), the method comprising the
steps of:
(a) forming an ink image on a preliminary receiving surface (9);
(b) passing a final receiving substrate (11) through a first nip (32) where it comes
into contact with the preliminary receiving surface (9);
(c) exerting a first pressure on the final receiving substrate (11) in the first nip
(32) to transfer the ink image from the preliminary receiving surface (9) to the final
receiving substrate (11);
(d) passing the final receiving substrate (11) through a second nip (39); and
(e) exerting a second pressure on the final receiving substrate (11) in the second
nip (39) to fuse the ink image into the final receiving substrate (11).
2. A method as claimed in claim 1 wherein the pressure exerted on the final receiving
substrate (11) in the second nip (39) is sufficient to achieve an ink pile height
of about 0.0178mm (0.0007inch) or less.
3. A method as claimed in claim 1 or claim 2 wherein the pressure exerted on the final
receiving substrate (11) in the first nip (32) is less than about 5.52 x 106 Pa (800 psi).
4. A method as claim in any preceding claim wherein the pressure exerted on the final
receiving substrate (11) in the second nip (39) is between about 2.76 x 106 Pa (400 psi) and about 13.79 x 106 Pa (2000 psi).
5. A method as claimed in any preceding claim wherein the final receiving substrate (11)
is preheated to a temperature of between about 50°C and about 100°C before it is passed
through the first nip (32).
6. A method as claimed in any preceding claim wherein the final receiving substrate (11)
is heated to a temperature of between about 50°C and about 100°C after the ink image
is transferred to the final receiving substrate (11) and prior to passing the final
receiving substrate (11) through the second nip (39).
7. A method as claimed in any preceding claim wherein the step of passing the final receiving
substrate (11) through a first nip (32) comprises the step of passing the final receiving
substrate between the preliminary receiving surface (9) and a transfer roller (34).
8. A method as claimed in any preceding claim wherein the step of passing the final receiving
substrate (11) through a second nip (39) comprises the step of passing the final receiving
substrate (11) between a first fuser roller (36) and a second fuser roller (38).
9. A method as claimed in claim 8 wherein the second fuser roller (38) has an elastomeric
outer layer (54).
10. A method as claimed in claim 8 or claim 9 wherein the first fuser roller (36) has
a metallic outer surface.
11. A method as claimed in any of claims 8 to 10 further including the step of applying
a release agent to the first fuser roller (36) to prevent the ink image from adhering
to the first fuser roller (36).
12. A method as claimed in claim 11 wherein the step of applying a release agent to the
first fuser roller (36) further comprises the step of contacting the first fuser roller
(36) with a liquid impregnated surface.
13. A method as claimed in any of claims 8 to 12 further including the step of maintaining
the first fuser roller (36) at a temperature of between about 50°C and about 100°C.
14. A method as claimed in any preceding claim wherein the step of passing the final receiving
substrate (11) through a second nip (39) further comprises the step of applying a
coating to the final receiving substrate (11) in the second nip (39).
15. An ink jet printing system (10) for forming an ink image on a final receiving substrate
(11) comprising:
a print head (12) for ejecting drops of ink onto a preliminary receiving surface (9)
to form an ink image thereon;
a first nip (32) formed by the preliminary receiving surface (9) and an opposing surface,
the first nip (32) receiving the final receiving substrate (11) and exerting a first
pressure on the final receiving substrate (11) to transfer the ink image to the final
receiving substrate (11); and
a second nip (39) for receiving the final receiving substrate (11) after the final
receiving substrate (11) passes through the first nip (32), the second nip (39), exerting
a second pressure on the final receiving substrate to fuse the ink image into the
final receiving substrate (11).
16. An ink jet printing system as claimed in claim 15 wherein the pressure exerted on
the final receiving substrate (11) in the second nip (39) is sufficient to achieve
an ink pile height of about 0.0178mm (0.0007 inch) or less.
17. An ink jet printing system (10) as claimed in claim 15 or claim 16 wherein the pressure
exerted on the final receiving substrate (11) in the second nip (39) is between about
2.76 x 106 Pa (400 psi) and about 13.79 x 106 Pa (2000 psi).
18. An ink jet printing system (10) as claimed in any of claims 15 to 17 wherein the pressure
exerted on the final receiving substrate (11) in the first nip (32) is less than about
5.52 x 106 Pa (800 psi).
19. An ink jet printing system as claimed in any of claims 15 to 18 further including
a media heater (50) between the first nip (32) and the second nip (39) for heating
the final receiving substrate (11) to a temperature of between about 50°C and about
100°C prior to the final receiving substrate (11) entering the second nip (39).
20. An ink jet printing system (10) as claimed in any of claims 15 to 19 wherein the second
nip (39) comprises a first fuser roller (36) and a second fuser roller (38), the second
fuser roller (38) being biased into contact with the first fuser roller (36).
21. An ink jet printing system (10) as claimed in claim 20 wherein the first fuser roller
(36) has a metallic outer surface.
22. An ink jet printing system (20) as claimed in claim 21 wherein the second fuser roller
(38) has an elastomeric outer layer (54) forming an outer surface.
23. An ink jet printing system as claimed in any of claims 20 to 22 further comprising
an applicator in contact with the outer surface of the first fuser roller (36), the
applicator applying a coating to the outer surface of the first fuser roller (36).
24. An ink jet printing system (10) as claimed in claim 23 wherein the coating comprises
a release agent for preventing the ink image from adhering to the outer surface of
the first fuser roller (36).
25. An ink jet printing system (10) as claimed in any of claims 20 to 24 further comprising
a roller heater (37) for maintaining the first fuser roller (36) at a temperature
of between about 50°C and about 100°C.