Patent Application
20190316001
The disclosure herein is directed to release fluids or agents that are useful in release coating in toner-based technologies.
In electrostatographic reproducing apparatuses, including digital, image on image, and contact electrostatic printing apparatuses, a light image of an original to be copied is typically recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and pigment particles, or toner. The residual 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 fixing or fusing.
In order to fix or fuse the toner onto a support member permanently by heat, it is necessary to elevate the temperature of the toner to a point at which the constituents of the toner coalese and become tacky. This heating action causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner cools, solidification of the toner causes the toner to be bonded firmly to the support member.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of from about 90° C. to about 200° C. or higher, depending on the softening range of the particular resin used in the toner. It may be undesirable, however, to increase the temperature of the substrate substantially higher than about 250° C. because the substrate may discolor or scorch or ignite at such elevated temperatures, particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described. These methods include providing the application of substantial heat and pressure concurrently by various means, including fuser members such as a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat can be applied by heating one or both of the rolls, plate members, belt members, or the like. The fuser member can be in the form of a roller, drum, belt, sheet, film, drelt (a hybrid between a roll and a belt), and the like. The fusing of the toner particles occurs when the proper combination of heat, pressure, and/or contact for the optimum time period are provided. The balancing of these variables to bring about the fusing of the toner particles can be adjusted to suit particular machines or process conditions.
During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate or belt members. The concurrent transfer of heat and the application of pressure in the nip affect the fusing of the toner image onto the support.
Different types of release fluids or agents can be used to provide sufficient release. However, the sufficiency of the release depends on the selected release fluid or agent and an appropriate combination of the fuser member surface material and any filler to be incorporated into the fuser member surface material.
It would be desirable to have release fluids that have long shelf life and predictable properties.
According to various embodiments, there is provided a fuser member including a substrate; an outer layer covering the substrate; and a release fluid on the outer layer. The release fluid including a hindered amine stabilizer represented by:
wherein q is an integer between 1 and 100.
According to various embodiments, there is disclosed a release fluid including an amino functional fluid and a hindered amine stabilizer. The hindered amine stabilizer is represented by:
wherein q is an integer between 1 and 100.
A further aspect described herein is an image forming apparatus. The image forming apparatus includes a photoreceptor having a photosensitive layer; a charging device which charges the photoreceptor; an exposure device which exposes the charged photoreceptor to light, thereby forming an electrostatic latent image on a surface of the photoreceptor. The image forming apparatus includes a developer station for developing a toner image on a surface of the photoreceptor; at least one transfer device for transferring the toner image to a recording medium and a fuser station for fixing the toner images transferred to the recording medium, onto the recording medium by heating the recording medium, thereby forming a fused image on the recording medium wherein the fuser station includes; a fuser member, a pressure member and a release fluid in combination with said fuser member. The release fluid is an amino functional fluid and a hindered amine stabilizer represented by:
wherein q is an integer between 1 and 100.
A further aspect described herein is a fuser member. The fuser member includes a substrate; an outer layer covering the substrate, the outer layer comprising fluoroelastomer; and a release fluid on the outer layer. The release fluid includes a hindered amine stabilizer having a structure:
wherein q is an integer between 1 and 100.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the present teachings and together with the description, serve to explain the principles of the present teachings.
It should be noted that some details of the FIGS. have been simplified and are drawn to facilitate understanding of the embodiments rather than to maintain strict structural accuracy, detail, and scale.
Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary embodiments in which the present teachings may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present teachings and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present teachings. The following description is, therefore, merely illustrative.
Illustrations with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” The term “at least one of” is used to mean one or more of the listed items can be selected.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of embodiments are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5. In certain cases, the numerical values as stated for the parameter can take on negative values. In this case, the example value of range stated as “less than 10” can assume negative values, e.g. −1, −2, −3, −10, −20, −30, etc.
Although embodiments of the disclosure herein are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more.” The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. For example, “a plurality of resistors” may include two or more resistors.
Referring to
After the toner particles have been deposited on the photoconductive surface, in image configuration, they are transferred to a copy sheet 116 by transfer apparatus 115, which can be performed by pressure transfer or electrostatic transfer. Alternatively, the developed image can be transferred to an intermediate transfer member, or bias transfer member, and subsequently transferred to a copy sheet. Examples of copy substrates include paper, transparency material such as polyester, polycarbonate, or the like, cloth, wood, or any other desired material upon which the finished image will be situated.
After the transfer of the developed image is completed, copy sheet 116 advances to fusing station 119, depicted in
The outer layer 203 may be selected from the group consisting of a silicone elastomer, a fluorosilicone elastomer, a fluoroelastomer, a fluorinated hydrocarbon polymer, a fluorinated hydrocarbon and silicone polymer blend, silicone copolymers, and crosslinked blends of fluorinated hydrocarbon copolymers and silicone copolymers. Examples of the outer surface of the fuser system members include fluoroelastomers and hydrofluoroelastomers.
Specifically, suitable fluoroelastomers are those described in detail in U.S. Pat. Nos. 5,166,031, 5,281,506, 5,366,772 and 5,370,931, together with U.S. Pat. Nos. 4,257,699, 5,017,432 and 5,061,965, the disclosures each of which are incorporated by reference herein in their entirety. As described therein, these elastomers are from the class of: 1) copolymers of vinylidenefluoride and hexafluoropropylene; 2) terpolymers of vinylidenefluoride, hexafluoropropylene and tetrafluoroethylene; and 3) tetrapolymers of vinylidenefluoride, hexafluoropropylene, tetrafluoroethylene and cure site monomer, are known commercially under various designations as VITON A®, VITON B®, VITON E®, VITON E 60C®, VITON E430®, VITON 910®, VITON GH®; VITON GF®; and VITON ETP®. The VITON® designation is a Trademark of E.I. DuPont de Nemours, Inc. The cure site monomer can be 4-bromoperfluorobutene-1,1,1-dihydro-4-bromo-perfluorobutene-1,3-bromoper-fluoro-propene-1,1,1-dihydro-3-bromoperfluoro-propene-1, or any other suitable, known cure site monomer commercially available from DuPont. Other commercially available fluoropolymers include FLUOREL 2170®, FLUOREL 2174®, FLUOREL 2176®, FLUOREL 2177® and FLUOREL LVS 76®, FLUOREL® being a Trademark of 3M Company. Additional commercially available materials include AFLAS®, a poly(propylenetetra-fluoroethylene), and FLUOREL II® (LII900), a poly(propylene-tetrafluoroethylene-vinylidenefluoride), both also available from 3M Company, as well as the Tecnoflons identified as FOR-60KIR®, FOR-LHF®, NM® FOR-THF®, FOR-TFS®, TH®, and TN505®, available from Montedison Specialty Chemical Company.
The fluoroelastomers VITON GH® and VITON GF® have relatively low amounts of vinylidenefluoride. The VITON GF® and Viton GH® have about 35 weight percent of vinylidenefluoride, about 34 weight percent of hexafluoropropylene and about 29 weight percent of tetrafluoroethylene with about 2 weight percent cure site monomer.
The amount of fluoroelastomer compound in solution in the outer layer solutions, in weight percent total solids, is from about 10 to about 25 percent, or from about 16 to about 22 percent by weight of total solids. Total solids as used herein include the amount of fluoroelastomer, dehydrofluorinating agent and optional adjuvants and fillers, including metal oxide fillers. In addition to the fluoroelastomer, the outer layer may comprise a fluoropolymer or other fluoroelastomer blended with the above fluoroelastomer. Examples of suitable polymer blends include the above fluoroelastomer, blended with a fluoropolymer selected from the group consisting of polytetrafluoroethylene and perfluoroalkoxy. The fluoroelastomer can also be blended with non-fluorinated ethylene or non-fluorinated propylene.
An inorganic particulate filler may be used in connection with the polymeric outer layer, in order to provide anchoring sites for the functional groups of the fuser agent. Examples of suitable fillers include inorganic fillers such as silicas or a metal-containing filler, such as a metal, metal alloy, metal oxide, metal salt, or other metal compound. The general classes of metals which can be used include those metals of Groups 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6b, 7b, 8, and the rare earth elements of the Periodic Table. For example, the filler can be an oxide of aluminum, copper, tin, zinc, lead, iron, platinum, gold, silver, antimony, bismuth, zinc, iridium, ruthenium, tungsten, manganese, cadmium, mercury, vanadium, chromium, magnesium, nickel and alloys thereof. Other specific examples include inorganic particulate fillers of aluminum oxide, and cupric oxide; reinforcing and non-reinforcing calcined alumina and tabular alumina, respectively, along with silicas. Other fillers include various forms of carbon, such as carbon nanotubes, graphene or other forms of carbon; and doped metal oxides such as antimony-doped tin oxide, indium-doped tin oxide, and the like. The filler may include just one filler or a mixture of fillers.
The thickness of the outer layer 203 of the fuser member herein is from about 10 to about 250 micrometers, or from about 5 to about 100 micrometers, or from about 1 to about 50 micrometers.
Optional intermediate adhesive layers and/or intermediate polymer or elastomer layers may be applied to achieve desired properties and performance objectives of the embodiments herein. The intermediate layer may be present between the substrate and the outer polymeric surface. Examples of suitable intermediate layers include silicone rubbers such as room temperature vulcanization (RTV) silicone rubbers; high temperature vulcanization (HTV) silicone rubbers and low temperature vulcanization (LTV) silicone rubbers. These rubbers are known and readily available commercially such as SILASTIC® 735 black RTV and SILASTIC® 732 RTV, both from Dow Corning; and 106 RTV Silicone Rubber and 90 RTV Silicone Rubber, both from General Electric. Other suitable silicone materials include the siloxanes (such as polydimethylsiloxanes); and the like. Another specific example is Dow Corning Sylgard 182. An adhesive intermediate layer may be selected from, for example, epoxy resins and polysiloxanes.
There may also be provided an adhesive layer between the substrate and the intermediate layer. There may also be an adhesive layer between the intermediate layer and the outer layer. In the absence of an intermediate layer, the outer layer may be bonded to the substrate via an adhesive layer. The thickness of the intermediate layer is from about 0.5 to about 20 mm, or from about 1 to about 10 mm, or from about 3 to about 5 mm.
In embodiments, the release fluids or agents described herein are provided onto the outer layer of the fuser member via a delivery mechanism such as a delivery roll. The delivery roll is partially immersed in a sump, which houses the release fluid or agent.
The release fluids or agents are renewable in that the release fluid or agent is housed in a holding sump and provided to the fuser roll when needed, optionally by way of a release fluid donor roll in an amount of from about 0.1 to about 20 mg/copy, or from about 1 to about 12 mg/copy. The system by which fuser release fluid is provided to the fuser roll via a holding sump and, optionally, a donor roll is well known. The release fluid may be present on the fuser member surface in a continuous or semi-continuous phase. The release fluid in the form of a film is in a continuous phase and continuously covers the fuser member.
The term “drive” or “drive motor” can apply to any electromechanical arrangement capable of providing a desired rotational speed, and could include, for example, simply an electrical motor, such as a brush, brushless, or stepper motor, with or without accompanying transmission mechanisms. Also, any roll, including a fuser roll, donor roll, or metering roll, can, in alternate embodiments, be in the form of a belt entrained around two or more rollers.
A traditional release agent management system (RAM) applies release fluid to the fuser roll at an idle release fluid rate (or no release fluid) when a print job is not running, and at a steady state running release fluid rate when a print job is running. These systems change from the idle release fluid rate to the steady state running oil rate when a print job is started.
Embodiments herein use an amino functional fluid. In an embodiments, the amino functional fluid is a blend containing an amino functional silicone fluid and a non-functional silicone fluid. The release fluid blend enables good clear toner fix.
The blended release fluid described herein includes a blend of Formula I (amino functional silicone fluid) and Formula II (non-functional silicone fluid).
Examples of suitable amino functional silicone fluids include those having pendant amino groups, such as those having the following Formula I:
where Q represents —R1—X, wherein R1 represents an alkyl group having from about 1 to about 10 carbons. X represents —NH2 or —NHR2NH2 with R2 having the same description as R1. In Formula I, n is an integer from 1 to 50, m is an integer from 10 to 5,000. T1 and T2 are methyl (—CH3), or hydroxyl (—OH) group. The structure in Formula I can be a block or a random copolymer. An amount of silanol (Si—OH) is defined as a molar ratio of Si—OH moieties over total number of silicon atoms. The amount of silanol is less than 200 ppm in the release fluid. In embodiments the amount of silanol is less than 150 ppm of the release fluid, or the amount of silanol is less than 50 ppm of the release fluid. The amount of silanol (Si—OH) is defined as moles of Si—OH moieties over total moles of silicon atoms.
In embodiments in Formula I, n is from about 1 to about 50, or from about 1 to about 25 or from about 1 to about 10; m is from about 10 to about 5,000, or from 50 to 1000 or from 100 to 1000. In embodiments, n is from about 1 to about 10 providing pendant groups that are mono-amino, di-amino, tri-amino, tetra-amino, penta-amino, hexa-amino, hepta-amino, octa-amino, nona-amino, deca-amino, and the like.
In embodiments, X represents —NH2, and in other embodiments, R1 is propyl. In embodiments, X represents —NHR2NH2, and in embodiments, R2 is propyl.
In embodiments, the Formula I has a molecular weight (Mw) of from about 1,000 to about 100,000, or from about 1,000 to about 10,000 daltons and a viscosity of from about 10 to about 1,500 cS, or from about 50 to about 1,000 cS.
Examples of suitable non-functional silicone release fluids (component b) include those having the following Formula II:
In Formula II, r is an integer from 10 to 5,000. T1 and T2 are methyl (—CH3), or hydroxyl (—OH). The structure in Formula II can be a block or a random copolymer.
In embodiments in Formula II, r is from about 10 to about 5,000, or from 50 to 1000 or from 100 to 1000.
In embodiments, Formula II has a molecular weight (Mw) of from about 1,000 to about 100,000, or from about 1,000 to about 10,000 daltons and a viscosity of from about 10 to about 1,500 cS, or from about 50 to about 1,000 cS.
The amount of Formula I in the release fluid blend is from 10 weigh percent to about 50 weight percent of the blended release fluid. In embodiments, the amount of Formula I is from 15 weight percent to 45 weight percent in the release fluid blend, or from 20 weight percent to about 40 weight percent blended release fluid blend. In embodiments, the amount of Formula II is from 50 weight percent to 90 weight percent. In embodiments, the amount of Formula II is from 55 weight percent to 85 weight percent or from 60 weight percent to about 80 weight percent of the release fluid blend.
In embodiments, the release fluid of the blend of Formula I and Formula II has a specific amine content and viscosity. For example, the release fluid has a mole percent amine of about 0.01 to about 0.9, or from about 0.03 to about 0.6, or from about 0.08 to about 0.50, or from 0.09 to 0.40, or from 0.15 to 0.25. Mole percent amine refers to the relationship: 100×(moles of amine groups/moles of silicon atoms).
In embodiments, the release fluid of the blend of Formula I and Formula II has a viscosity of from about 50 to about 600 or from about 60 to about 500 or from about 70 to about 400 centipoise. The silicone release fluid can have terminal silanol Si—OH groups during synthesis of the silicone release fluid.
When the outer layer is made of a fluorinated elastomer, it has been hypothesized and demonstrated that the amine group on the release fluid blend chemically reacts with the surface carbon-carbon double bonds of the fluorinated elastomer.
A RAM system described previously, applies a metered amount of the release fluid to the fuser member. The fuser roll topcoat is made of a fluorinated Viton elastomer. It is hypothesized that the amine group in the release fluid chemically reacts with the surface carbon-carbon double bonds of Viton elastomers, a hydrofluoroelastomers. This forms a homogenous robust release fluid layer on the roll surface, enabling good release, good IQ and long fuser roll life. Hence stability of amine groups over time is critical to proper functioning of fuser roll.
The pendant amine groups, in embodiments propylamine groups, of the release fluid are known to undergo oxidative degradation over time, and the release fluid may end up with a lower amine mole percent upon shelf storage than at time of manufacture. In addition, amine groups can also undergo further oxidative degradation as the release fluid sits at an elevated temperature in the release fluid sump in machine. Hence, adding a stabilizer to a release fluid prevents amine degradation and extends shelf life. Hindered amines are known to decrease the rate at which pendant amine groups undergo oxidative damage in silicone release fluids. The hindered amine group acts as a free radical scavenger and prevents oxidative degradation by trapping free radicals that may be generated over time. Disclosed herein is a hindered amine stabilizer, added at low levels, of less than or equal to 1000 parts per million (ppm) of release fluids to improve shelf life stability. In embodiments, the hindered amine stabilizer is from about 100 ppm to about 800 ppm based on the total amount of the release fluid. In embodiments, the hindered amine stabilizer is from about 150 ppm to about 500 ppm based on the total amount of the release fluid
The general structure of hindered amine stabilizer used is given in Formula III, wherein q is integer from 1 to 100, or in embodiments, q is from 3 to 80, or from 5 to 70, or from 6 to 50.
Specific embodiments will now be described in detail. These examples are intended to be illustrative, and not limited to the materials, conditions, or process parameters set forth in these embodiments. All parts are percentages by solid weight unless otherwise indicated.
Measuring Silanol Level in Release Fluid
Silanol (terminal Si—OH groups) were measured by 1H NMR using a Bruker AV500 NMR spectrometer. 100 μL of release fluid were dissolved in 500 μL deuterated chloroform and 30 μL of trichloroacetyl isocyanate (TAIL) were added to the solution. Upon addition TAIC reacts with Si—OH forming urethane and shifts adjacent dimethyl peaks downfield, separating them from the bulk of the methyl peaks therefore allowing quantification of the underlying Si—OH groups.
Print tests were conducted on a 4 station iGen machine running CMYK (cyan, magenta, yellow and black) toner. Fuser roll life was evaluated by running prints on the iGen machine and counting the number of prints to fuser roll failure. A stress print designed to stress the fuser roll and result in early roll failure was printed repeatedly on the iGen machine till failure. The paper used in the print test was an offset grade coated paper, brand named Creator. Failure occurs when toner components (resin, pigments and additives) build up on the fuser roll and results in image quality defect showing up on the print. If the release fluid is ineffective in protecting the fuser roll, contaminants may build up on the roll over time. These contaminants could be components of the toner or components of the paper or dust and dirt present in general ambient environment. As contaminants build up on fuser roll, they eventually transfer to the prints in unwanted locations and result in image quality defects. These defects may show up as streaks or bands on the prints, or they may show up as patches on the print, or they may show up as gloss differentials on the prints.
Four different fuser release fluids were tested in iGen machine for fuser roll life. Control 1 was the current mainline release fluid for iGen, labelled Control 1 herein. Release Fluid 1 (RF-1), Release Fluid 2 (RF-2) and Release Fluid 3 (RF-3) were test silicone release fluids provided by Wacker Chemical Corporation. Control 1 has no hindered amine stabilizer. RF-1, RF-2 and RF-3 each have about 250 ppm of the hindered amine stabilizer of Formula III added. Table 1 shows the amount of amino functional silicone fluid and non-functional silicone fluid in each fluid tested. The results are summarized in Table 1.
The release fluid delivery RAM and fuser components were cleaned thoroughly before swapping and testing release fluids. The average life of fuser roll with test release fluids is given in Table 2 below. As can be seen clearly, RF-1, RF-2 and RF-3 release fluids having lower levels of free silanol and having added hindered amine stabilizer described herein gave significantly improved fuser roll life than control 1 release fluid.
In summary, using release fluid with low levels of free silanol significantly improves fuser roll life. This can result in significant cost savings in fuser roll replacement. The hindered amine stabilizer improves the shelf life stability of release fluids by preventing oxidative degradation of the amine groups. *Roll did not fail—test was suspended
Amine groups in the release fluid are critical for good performance of the fuser roll i.e. good toner release from the roll surface and long operating life of the fuser roll. The amine groups in the release fluid can interact with the fluoroelastomer on the fuser roll surface. For example, pendent propylamine groups in the release fluid may chemically react with vinyl groups in the fluoroelastomer, thereby anchoring the release fluid to the fuser roll surface via a covalent bond. A robust and reliable layer of the release fluid on the fuser roll surface is critical for achieving clean release of the toner from the fuser roll surface, and for also enabling long fuser roll life.
The pendant amine groups, in embodiments propylamine groups, of the release fluid are known to undergo oxidative degradation over time, and the release fluid may end up with a lower amine mole percent upon shelf storage than at time of manufacture. In addition, amine groups can also undergo further oxidative degradation as the release fluid sits at an elevated temperature in the release fluid sump in machine.
Amine group stability with and without hindered amine stabilizer.
Two release fluids, one having added hindered amine stabilizer and one having no hindered amine stabilizer were evaluated for amine group stability at elevated temperature. 10 mL of each oil was added to 20 mL glass vials. The open vials were placed in the air circulating oven at 170° C. to simulate accelerated oxidative degradation of the amine groups. Sample of release fluids were withdrawn at different time intervals and were analyzed for amount of remaining propylamino groups using NMR method. Molar concentrations of propyl amino groups were measured by proton NMR using a Bruker AVANCE500 NMR spectrometer. Release fluid 4 (RF-4) was a silicone release fluid (Xerox Part number 008R13031) containing approximately 250 ppm of the hindered amine stabilizer. Release fluid 5 (RF-5) containing no hindered amine stabilizer was obtained from Wacker Chemical Corporation. As can be seen clearly from Table 3, RF-4 containing hindered amine stabilizer had higher amount of remaining amine group than RF-5, indicating that the hindered amine stabilizer protects amine group against oxidative degradation. RF-5 release fluid having no hindered amine stabilizer shows approximately 45 percent degradation in propylamino groups after 18 hours at 170° C. RF-4 release fluid having the hindered amine stabilizer shows no degradation in propylamino groups.
It will be appreciated that variants of the above-disclosed and other features and functions or alternatives thereof may be combined into other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also encompassed by the following claims
This application relates to commonly assigned copending application Ser. No. ______ (Docket 20180124US01, XRX-0155), RELEASE FLUID COMPOSITION, filed simultaneously herewith and incorporated by reference herein. This application relates to commonly assigned copending application Ser. No. ______ (Docket 20180152US01, XRX-0157), METHOD OF PRINTING, IMAGE FORMING APPARATUS AND PRINT, filed simultaneously herewith and incorporated by reference herein.
