WO2013025209A1

WO2013025209A1 - Electrophotographic printing of electrical conductors

Info

Publication number: WO2013025209A1
Application number: PCT/US2011/048015
Authority: WO
Inventors: Detlef Schulze-Hagenest
Original assignee: Eastman Kodak Company
Priority date: 2011-08-17
Filing date: 2011-08-17
Publication date: 2013-02-21

Abstract

A method for producing an electrical conductor on a receiver using an electrophotographic printer includes providing a metallic toner having a composition including 60-90 wt. pct. of an aggregate of metallic particles and frit particles and 10-40 wt. pct. polymeric binder particles. The aggregate includes 40-95 wt. pct. metallic particles and 5-60 wt, pet. frit particles. A continuous layer of the metallic toner is applied in a selected pattern on the substrate using the electrophotographic printer. The metallic toner is cured by heating the metallic toner so that the metallic particles form the electrical conductor.

Description

ELECTROPHOTOGRAPHIC PRINTING OF ELECTRICAL

CONDUCTORS FIELD OF THE INVENTION

This invention pertains to the field, of electrophotographic printing and more particularly to producing electrical conductors on high-temperature substrates.

BACKGROUND OF THE INVENTION

Electrophotography is a useful process for printing images or other patterns on a receiver (or "imaging substrate"), such as a piece or sheet of paper or another planar medium, glass, fabric, metal, or other objects as will be described below. In this process, an electrostatic latent image is formed on a photoreceptor by uniformly charging the photoreceptor and then discharging selected areas of the uniform charge to yield an electrostatic charge pattern corresponding to the desired image (a "latent image").

After the latent image is formed, charged toner particles are brought into the vicinity of the photoreceptor and are attracted to the latent image to develop the latent image into a visible image. Note that the visible image may not be visible to the naked eye depending on the composition of the toner particles (e.g. clear toner).

After the latent image is developed into a visible image on the photoreceptor, a suitable receiver is brought into juxtaposition with the visible image. A suitable electric field is applied to transfer the toner particles of the visible image to the receiver to form the desired print image on the receiver. The imaging process is typically repeated many times with reusable photoreceptors.

The receiver is then removed from its operative association with the photoreceptor and subjected to heat or pressure to permanently fix ("fuse") the print image to the receiver.

Electrophotographic (EP) printers typically transport the receiver past the photoreceptor to form the print image. The direction of travel of the receiver is referred to as the slow-scan, process, or in-track direction. This is typically the vertical (Y) direction of a portrait-oriented receiver. The direction perpendicular to the slow-scan direction is referred to as the fast-scan, cross- process, or cross-track direction, and is typically the horizontal (X) direction of a portrait-oriented receiver. "Scan" does not imply that any components are moving or scanning across the receiver; the terminology is conventional in the art- Electrophotographic (EP) printers are commonly used to produce text, photos and graphical images. It has also been suggested to use electrophotographic printers for producing electrical conductors, for example, for antenna structures.

WO 2009 080 087 A describes a method using an electrophotographic printer for producing an antenna structure for an RFID device and a dry toner for use in an electrophotographic printer in producing such antenna structure. The dry toner is made up of toner particles having a composition of polymeric binder particles and metallic particles. Electrical conductors formed from such a dry toner are likely to be brittle when exposed to high temperatures.

Buettner et. al. "Laser Printing of RFID Antenna Coils on

Ceramic" in 2011 IMAPS/ACerS 7^th CICMT International Conference and

Exhibition, describe a silver toner using a glass binder for printing on a ceramic receiver. Electrical conductors formed from such a silver toner are likely to form cracks during curing or firing thereof, as described by Buettner et al.

U.S. Patent No. 6,110,632 describes a toner containing inorganic ceramic color for printing decals for the decoration of wares such as table china and porcelain. The toner includes an organic polymeric material and ceramic toner; the toner includes a ceramic pigment and glass frit.

There is therefore a need for an improved way of producing an electrical conductor on a high temperature substrate, and a corresponding toner useful for forming durable electrical conductors with an electrophotographic printer.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a toner for use in electrophotographic printing, the toner having a composition including 60-90 weight percent (wt. pet.) of an aggregate of metallic particles and frit particles and 10-40 wt. pet. polymeric binder particles, wherein the aggregate includes 40-95 wt. pet. metallic particles and 5-60 wt. pet. frit particles. According to another aspect of the present invention, there is provided a method for producing an electrical conductor on a high-temperature substrate using an electrophotographic printer. The method includes providing a toner composition including 60-90 weight percent (wt. pet.) of an aggregate of metallic particles and frit particles and 10-40 wt. pet. polymeric binder particles, wherein the aggregate includes 40-95 wt. pet. metallic particles and 5-60 wt. pet. frit particles, applying a continuous layer of the toner composition in a selected pattern on the substrate using the electrophotographic printer, and curing the metallic toner by heating the metallic toner so that the metallic particles form the electrical conductor.

The receiver can be the high temperature substrate, in which case the toner can be cured on the substrate by heating the toner so that the metallic particles form the electrical conductor. It is also possible that the receiver is different from the high temperature substrate, in which case the toner is transferred to the high temperature substrate prior to curing the same thereon. The method can use a specific toner composition having metallic particles useful for forming electrical conductors and polymeric binder particles to bind the particles for initial printing, and frit particles to bind the metallic particles after curing.

The invention advantageously enables durable electrical conductors to be produced using an electrophotographic printing process, which provides great flexibility with respect to the layout of the electrical conductors.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the present invention will become more apparent when taken in conjunction with the following description and drawings wherein identical reference numerals have been used, where possible, to designate identical features that are common to the figures, and wherein:

FIG. 1 is an elevational cross-section of an electrophotographic reproduction apparatus according to an embodiment;

FIG. 2 is an elevational cross-section of the reprographic image- producing portion of the apparatus of FIG. 1 ; and FIGS. 3-4 are flow diagrams showing sequences of steps for producing an electrical conductor on a receiver using an electrophotographic printer according to various embodiments.

The attached drawings are for purposes of illustration and are not necessarily to scale.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, "toner particles" are particles of one or more material(s) that are transferred by an EP printer to a receiver to produce a desired effect or structure (e.g. a print image, texture, pattern, or coating) on the receiver. Toner particles can be ground from larger solids, or chemically prepared (e.g. precipitated from a solution of a pigment and a dispersant using an organic solvent), as is known in the art. Toner particles can have a range of diameters, e.g. less than 8um, on the order of 10-15μπι, up to approximately 30um, or larger ("diameter" refers to the volume-weighted median diameter, as determined by a device such as a Coulter Multisizer). Toner particles having a volume-weighted median diameter, e.g., as measured by Coulter Multisizer between 5 and 30μιη are especially contemplated to be beneficial for forming electrical conductors.

"Toner" refers to a composition of materials that form toner particles, and that can form an image, pattern, or coating when deposited on an imaging member including a photoreceptor, a photoconductor, or an

electrostatically-charged or magnetic surface. Toner can be transferred from the imaging member to a receiver. Toner is also referred to in the art as marking particles, dry ink, or developer, but note that herein "developer" is used differently, as described below. Toner can be a dry mixture of particles or a suspension of particles in a liquid toner base.

In this application toners are classified as metallic toner or non- metallic toner. As used herein, a metallic toner is considered to be a toner having a sufficient amount of metallic particles that are capable of forming an electrical conductor after curing thereof by forming a continuous chain of metallic particles. Such a continuous chain can contain islands of other materials, voids,

irregularities, contaminants in the continuous chain, as long as the chain permits electrical current to pass therethrough. A specific metallic toner composition will be described in more detail hereinbelow. As used herein, a non-metallic toner is considered to be a toner not having metallic particles or having such a small amount of metallic particles that is not sufficient to form an electrical conductor after curing thereof.

Toner includes toner particles and can include other particles. Any of the particles in toner can be of various types and have various properties. Such properties can include absorption of incident electromagnetic radiation (e.g.

particles containing colorants such as dyes or pigments), absorption of moisture or gasses (e.g. desiccants or getters), suppression of bacterial growth (e.g. biocides, particularly useful in liquid-toner systems), adhesion to the receiver (e.g. binders), electrical conductivity or low magnetic reluctance (e.g. metal particles), electrical resistivity, texture, gloss, magnetic remnance, fluorescence, resistance to etchants, and other properties of additives known in the art.

In various embodiments, the metallic toner has a composition including 60-90 weight percent (wt pet.) of an aggregate of metallic particles and frit particles and 10-40 wt. pet. polymeric binder particles, wherein the aggregate includes 40-95 wt. pet. metallic particles and 5-60 wt. pet. frit particles. The aggregate can be formed in various ways. It does not have to be premixed and then mixed with the polymeric binder. The metallic particles and the frits particles can form complexes, electrostatically attract each other, or have other effects on each other in the aggregate or the metallic toner composition. In one embodiment the aggregate includes at least 60 wt. pet. metallic particles and less than 40 wt. pet, frit particles to facilitate formation of electrical conductors during curing of the metallic toner. In another embodiment, the aggregate includes at least 80 wt. pet. metallic particles and less than 20 wt. pet. frit particles.

The polymeric binder can be any polymer having the ability to form toner that is having acceptable electrostatic properties and having physical properties permitting the production of toners. Furthermore, the polymeric binder should not negatively influence a subsequent curing process. In particular, if the polymeric binder at least partially evaporates during the curing process, such evaporation should not lead to excessive voids or bubbles in the remaining cured toner layer. The polymeric binder can particularly be an acrylate-based oligomer or polymer including polymers of methyl methacrylate or methyl methacrylate-butyl methacrylate copolymers. The polymeric binder can also include other co-polymers such as styrene- or vinyl-acrylates such as polystyrene- n-butylmethacrylate or polystyrene-n-butylacrylate. In particular, a polymeric binder including 65% styrene and 35% n-butyl methacrylate copolymer is envisaged.

Other polymers, however, can be used as an alternative to, or blended with, the acrylate-based materials mentioned above. Organic component or components of the polymeric binder can be selected from olefin polymers such as polyethylene or polypropylene, dienepolymers such as polybutadiene, polyisobutylene or polychloroprene, vinyl or vinylidene polymers such as polystyrene, styrene butyl-methacrylate copolymers, styrene-acrylonitrile copolymers, acrylonitrile-butadiene styrene terpolymers, polyvinyl butyral, polyvinylethers or polyvinyl ketones, fluorocarbon polymers such as

polytetrafluoroethylene and polyvinylidene fluoride, heterochain thermoplastics such as polyamides, polyesters, polyethanes, polypeptides, casein, polyglycols, polysulphides and polycarbonates, and cellulosic copolymers such as regenerated cellulose, cellulose acetate, and cellulose nitrate.

The organic component must meet the requirements set out at the beginning of this paragraph with respect to the formation of toners and the evaporation characteristics. The polymeric binder will have a substantially lower melting point compared to the metallic and frits particles in the toner composition. The metallic toner can be cured at a temperature at which at least some of the polymeric binder evaporates, thereby increasing the amount of the aggregate in the cured metallic toner. The metallic toner can optionally comprise charge control agents in an amount of 0.1 to 5 wt. pet. or wax in an amount of 0.1 to 10 wt. pet. The charge control agents can facilitate the electrophotographic process and wax can be useful in contact curing applications. In one embodiment the metallic particles have a volume-weighted median diameter, e.g., as measured by a Coulter Multisizer, of smaller than lOOnm. The metallic particles are preferred to be substantially spherical. The toner composition has toner particles having a volume-weighted median diameter, e.g., as measured by a Coulter Multisizer, between 5 and 30μηι.

The non-metallic toner can have a similar composition with a substantially lower amount of metallic particles in order to avoid formation. In one embodiment the metallic particles can be replaced by non-conducting particles such as ceramic particles or glass. Such a non-metallic toner can have similar curing behavior to the metallic toner, in particular with respect to the required curing temperature or expansion coefficients. The non-metallic toner can include color pigments to permit the toner to be distinguishable over the metallic toner to permit text or images to be printed.

In single-component or monocomponent development systems, "developer" refers to toner alone. In these systems, none, some, or all of the particles in the toner can themselves be magnetic. However, developer in a monocomponent system does not include magnetic carrier particles. In dual- component, two-component, or multi-component development systems,

"developer" refers to a mixture including toner particles and magnetic carrier particles, which can be electrically-conductive or -non-conductive. Toner particles can be magnetic or non-magnetic. The carrier particles can be larger than the toner particles, e.g. 15-20μτη or 20-300um in diameter. A magnetic field is used to move the developer in these systems by exerting a force on the magnetic carrier particles. The developer is moved into proximity with an imaging member or transfer member by the magnetic field, and the toner or toner particles in the developer are transferred from the developer to the member by an electric field, as will be described further below. The magnetic carrier particles are not intentionally deposited on the member by action of the electric field; only the toner is intentionally deposited. However, magnetic carrier particles, and other particles in the toner or developer, can be unintentionally transferred to an imaging member. Developer can include other additives known in the art, such as those listed above for toner. Toner and carrier particles can be substantially spherical or non-spherical.

As used herein, "high-temperature substrate" refers to any type of planar substrate that is capable of withstanding the temperatures required in curing toner. Examples of such substrates are ceramics (fired or unfired), green tape (fired or unfired), glass substrates in particular of quartz or borosilicate glass. The high temperature substrate can be of a type to be used in electrophotographic printing, i.e. permitting the toner to be applied directly thereon using an electrophotographic printing process. Alternatively, it is possible to use an intermediate receiver which can be used to apply toner thereon using an electrophotographic printing process. Thereafter the toner can be transferred from the intermediate receiver to a high temperature substrate. A well known example for such an intermediate receiver is a water-slide paper, which permits formation and fixing of toner images thereon using the electrophotographic printing process. Such water-slide paper permits easy removal of the thus printed and fixed toner images, which toner images can then be transferred to the high temperature substrate.

The electrophotographic (EP) printing process can be embodied in devices including printers, copiers, scanners, and facsimiles, and analog or digital devices, all of which are referred to herein as "printers." Electrostatographic printers such as electrophotographic printers that employ toner developed on an electrophotographic receiver can be used, as can ionographic printers and copiers that do not rely upon an electrophotographic receiver. Electrophotography and tonography are types of electrostatography (printing using electrostatic fields), which is a subset of electrography (printing using electric fields).

A digital reproduction printing system ("printer") typically includes a digital front-end processor (DFE), a print engine (also referred to in the art as a "marking engine") for applying toner to the receiver, and one or more post-printing system(s) (e.g. a curing system, a sorting system, a testing system, or a packaging system). A printer can produce selected patterns of toner on a receiver (e.g. electrical conductors, electrical circuit patterns and antenna structures). The DFE receives input electronic files (such as Postscript command files) composed of images from other input devices (e.g., a computer system, a CAD-system). The DFE can include various function processors, e.g. a raster image processor (RIP), image positioning processor, image manipulation processor, or image storage processor. The DFE rasterizes input electronic files into image bitmaps for the print engine to print. In some embodiments, the DFE permits a human operator to set up parameters such as layout, media type, or post- printing options. The print engine takes the rasterized image bitmap from the DFE and renders the bitmap into a form that can control the printing process from the exposure device to transferring the print image onto the receiver. The post- printing system applies features such as curing, sorting, testing and packaging of the prints. The post-printing system can be implemented as an integral component of a printer, or as a separate machine through which prints are fed after they are printed. It is also feasible, that certain features (e.g. curing) are implemented as an integral component of a printer, while others (sorting, testing, packaging) are implemented as a separate machine. Testing can, for example, relate to testing of the conductivity/functionality of electrical conductors, electrical circuit patterns and antenna structures formed during printing and curing of toner. Packaging can, for example, relate to laminating the receiver, having printed and cured toner thereon, to provide insulation with respect to the environment.

In an embodiment of an electrophotographic modular printing machine, e.g. the NEXPRESS 3000SE printer manufactured by Eastman Kodak Company of Rochester, N. Y., print images are made in a plurality of imaging modules arranged in tandem, and the print images are successively

electrostatically transferred to a receiver adhered to a transport web moving through the modules. Multiple toner layers can be at least partially overlaid to build up thicker toner layers. Commercial machines of this type typically employ intermediate transfer members in the respective modules for transferring images from the photoreceptor and transferring print images to the receiver. In other electrophotographic printers, each image is directly transferred to a receiver to form the corresponding print image.

A fixing device for fixing the toner layers applied by the imaging modules is typically provided downstream of the last imaging module arranged in line. Further fixing devices can be provided between imaging modules arranged in tandem. Fixing relates to heating of the toner transferred to the receiver to a temperature, where at least part of the toner particles melt to form a bond between the toner particles and also to the receiver. Typical fixing temperatures are between 120 to 180°C, which temperature is for example sufficient to at least partially melt polymeric binder particles included in the toner. Typical fixing devices use contact fixing, in which the receiver and the toner layer applied thereto is moved between two rollers, which are biased towards each other, to apply pressure to the toner layer and receiver. At least one of the rollers can be heated, to provide an elevated temperature. Non-contact fixing devices, using for example, radiation for heating the receiver or the toner layer, can be used herein for fixing the toner.

The downstream fixing device can also be replaced by a curing device, which permits at least partial melting of frits/metallic particles contained in the toner. Such a curing device can be provided either in-line, i.e. within an electrophotographic printer or off-line. The curing device typically heats the toner or receiver typically to temperatures of 750 to 900 °C. Curing can be performed in a contact manner by applying heat and pressure. Curing can also be performed in a non-contact manner by applying heat, for example, by baking in an oven to perform convective curing, using radiation, in particular IR- or UV radiation emitted by lamps, to perform radiation curing, exposing to radiation from arc lamps or a laser, passing a time- varying magnetic field through to perform microwave curing, passing radio-frequency (RF) electromagnetic waves through to perform RF curing, or using a hot plate. In various embodiments, curing includes heating the metallic toner to a temperature at which at least 50% of the polymeric binder particles evaporate out of the metallic toner composition. In various embodiments, the curing device heats the metallic toner above the melting temperature of the metallic particles.

In-line curing can be used where printing occurs directly on a high temperature substrate. Off-line curing can especially be used where printing occurs on an intermediate receiver, which requires the transfer of a print image to the high temperature substrate prior to a curing step. Off-line curing can also be used where printing occurs directly on a high temperature substrate in order to avoid high temperature within the electrophotographic printer, which can influence the components and processes therein. Electrophotographic printers can deposit different toners (e.g. having different compositions) in the different imaging modules. For example a metallic toner layer (or multiple metallic toner layers, at least partially overlapping each other, to build up the heights of the toner layer) can be provided in a specific pattern to form an electrical conductor, an electrical circuit, an antenna structure after curing thereof. A uniform or patterned layer of non-metallic toner can be provided as an overcoat or an insulator. A non-metallic toner layer that varies inversely according to heights of the metallic toner layers can also be used to establish level total toner stack heights. The respective toners can be deposited one upon the other at respective locations on the receiver and the height of a respective toner stack is the sum of the toner heights of each respective toner layer. Uniform stack height provides the print with a more even surface that can be beneficial in providing protection against damage.

FIGS. 1 and 2 are elevational cross-sections showing portions of a typical electrophotographic printer 100. Printer 100 is adapted to produce print images, such as single-layer, or multi-layer toner images, on a receiver. Print images include in particular any type of pattern, circuit structure, antenna structure, which can for example be formed by metallic toner and can also include text, graphics, photos, and other types of visual content which can for example be formed by non-metallic toner. An embodiment involves printing using an electrophotographic print engine having five sets of image-producing or -printing stations or modules arranged in tandem, but more or less than five of such stations or modules can be used to form a print image on a given receiver. Other electrophotographic writers or printer apparatus can also be included. Various components of printer 100 are shown as rollers; other configurations are also possible, including belts.

Referring to FIG. 1, printer 100 is an electrophotographic printing apparatus having a number of tandemly-arranged electrophotographic image- forming printing modules 31, 32, 33, 34, 35, also known as electrophotographic imaging subsystems. Each printing module 31, 32, 33, 34, 35 produces a toner image for transfer using a respective transfer subsystem 50 (for clarity, only one is labeled) to a receiver 42 successively moved through the modules. Receiver 42 is transported from supply unit 40, which can include active feeding subsystems as known in the art, into printer 100. In various embodiments, the visible image can be transferred directly from an imaging roller to a receiver 42, or from an imaging roller to one or more transfer roller(s) or belt(s) in sequence in transfer

subsystem 50, and thence to receiver 42. Receiver 42 is, for example, a selected section of a web of or a cut sheet or section of a high temperature planar media. Suitable high temperature media can be from any material capable of withstanding the temperatures used for curing toner on the receiver. Examples of such material are green tape; a ceramic (both fired or unfired); stone; and artificial or natural glass, such as quartz glass or a borosilicate glass. If the green tape or ceramic is not yet fired, it can be fired during the curing process of the toner by elevating the receiver and the toner to the required firing and curing temperature. The firing temperature is a temperature at which the ceramic substrate is caused to become rigid. Receiver 42 can also be an intermediate receiver, such as a water slide paper onto which a toner image is formed, and which toner image is later transferred to a high temperature substrate. Such water-slide paper and such a transfer process is known in the art. Use of such an intermediate receiver can be advantageous as no or only small modifications of known electrophotographic printers such as the NEXPRESS 3000SE printer mentioned above can be required in the process described herein.

Each receiver 42, during a single pass through the five printing modules 31, 32, 33, 34, 35, can have transferred in registration thereto up to five toner images to form multiple toner layers to build up the stack heights thereof. In particular, printing modules 31, 32 and 33 can apply metallic toner while printing modules 34 and 35 can apply non-metallic toner, either to provide a cover layer or to fill up spaces between the metallic toner portions. The skilled person will realize that other arrangements with respect to use of the metallic and non-metallic toner are possible. In this context it is noted that all printing modules can use a metallic toner.

Receiver 42 A is shown after passing through printing module 35.

Print image 38 on receiver 42 A includes uncured toner particles. Subsequent to transfer of the respective print images, which can be at least partially overlaid in registration, one from each of the respective printing modules 31, 32, 33, 34, 35, receiver 42A is advanced to a curing device 60, , to cure the print image 38. Transport web 81 transports the print-image-carrying receivers (e.g., 42 A) to curing device 60, which cures the toner particles to form a bond therebetween and to the receiver 42 A by the application of heat and optionally pressure. Non-contact heating e.g. by irradiation with IR-radiation, UV-radiation, microwaves is preferred, but curing can also include applying heat and pressure, for example using a pressure roller as shown in FIG. 1. The receivers 42 A are released from transport web 81 to permit them to feed cleanly into curing device 60. Transport web 81 is then reconditioned for reuse at cleaning station 86 by cleaning and neutralizing the charges on the opposed surfaces of the transport web 81. A mechanical cleaning station (not shown) for scraping or vacuuming toner off transport web 81 can also be used independently or with cleaning station 86. The mechanical cleaning station can be disposed along transport web 81 before or after cleaning station 86 in the direction of rotation of transport web 81.

Curing device 60 includes a heated fusing roller 62 and an opposing pressure roller 64 that form a nip 66 therebetween. In an embodiment, curing device 60 also includes a release fluid application substation 68 that applies release fluid, e.g. silicone oil, to fusing roller 62. Alternatively, wax-containing toner can be used without applying release fluid to fusing roller 62. Other embodiments of fusers, both contact and non-contact, can be employed.

Photoflash fusing uses short bursts of high-frequency electromagnetic radiation (e.g. ultraviolet light) to melt the toner. Radiant fixing uses lower-frequency electromagnetic radiation (e.g. infrared light) to more slowly melt the toner.

Microwave fixing uses electromagnetic radiation in the microwave range to heat the receivers (primarily), thereby causing the toner particles to melt by heat conduction, so that the toner is cured to the receiver 42.

The receivers (e.g., receiver 42B) carrying the cured image (e.g., cured image 39) are transported in a series from the curing device 60 along a path either to a remote output tray 69, or back to printing modules 31, 32, 33, 34, 35 to create an image on the backside of the receiver (e.g., receiver 42B), i.e. to form a duplex print. Receivers (e.g., receiver 42B) can also be transported to any suitable output accessory. For example, an auxiliary curing device can apply additional heat. Printer 100 can also include multiple curing devices 60 to support applications such as overprinting, as known in the art. Such curing devices can for example be arranged between printing modules arranged in tandem, to provide a certain degree of curing to a toner applied by the upstream printing module and before another toner layer is applied by the downstream module. For example, a two stage curing process can be used in which the curing devices arranged between printing modules arranged in tandem primarily melt the polymeric binder. This can lead to a certain degree of bonding between the particles sufficient to avoid the toner particles to be substantially disturbed during a subsequent application of a toner layer. After the toner layers, or at least the metallic toner layers, are applied a final curing is performed in which the toner layers are heated to a temperature at which at least a part of the frits particles or the metallic particles is melted to form an electrical conductor.

In various embodiments, between fuser 60 and output tray 69, receiver 42B passes through finisher 70. Finisher 70 can perform various operations, such as sorting, testing, and packaging.

Printer 100 includes main printer apparatus logic and control unit

(LCU) 99, which receives input signals from the various sensors associated with printer 100 and sends control signals to the components of printer 100. LCU 99 can include a microprocessor incorporating suitable look-up tables and control software executable by the LCU 99. It can also include a field-programmable gate array (FPGA), programmable logic device (PLD)„ microcontroller, or other digital control system. LCU 99 can include memory for storing control software and data. Sensors associated with the fusing assembly provide appropriate signals to the LCU 99. In response to the sensors, the LCU 99 issues command and control signals that adjust the heat or pressure within nip 66 and other operating parameters of curing device 60 for receivers. This permits printer 100 to print on receivers of various thicknesses. Image data for writing by printer 100 can be processed by a raster image processor (RIP; not shown). The output of the RIP can be stored in frame or line buffers for transmission of the print data to each of respective LED writers, e.g. for metallic and non-metallic toner. The RIP can be a part of printer 100 or remote there from. Image data processed by the RIP can be produced by a computer or from a memory or network which typically includes image data for the layout of electrical conductors. The RIP can be a suitably-programmed computer or logic device and is adapted to employ stored or computed matrices and templates for processing image data into rendered image data in the form of information suitable for printing. These matrices can include a screen pattern memory (SPM).

Further details regarding printer 100 are provided in U.S. Patent No. 6,608,641, issued on Aug. 19, 2003, to Peter S. Alexandrovich et al., and in U.S. Publication No. 2006/0133870, published on Jun. 22, 2006, by Yee S. Ng et al., the disclosures of which are incorporated herein by reference.

FIG. 2 shows more details of printing module 31, which is representative of printing modules 32, 33, 34, and 35 (FIG. 1), Primary chargmg subsystem 210 uniformly electrostatically charges photoreceptor 206 of imaging member 111, shown in the form of an imaging cylinder. Charging subsystem 210 includes a grid 213 having a selected voltage. Additional components provided for control can be assembled about the various process elements of the respective printing modules. Meter 211 measures the uniform electrostatic charge provided by charging subsystem 210, and meter 212 measures the post-exposure surface potential within a patch area of a latent image formed from time to time in a non- image area on photoreceptor 206. Other meters and components can be included.

LCU 99 sends control signals to the charging subsystem 210, the exposure subsystem 220 (e.g., laser or LED writers), and the respective development station 225 of each printing module 31, 32, 33, 34, 35 (FIG. 1), among other components. Each printing module can also have its own respective controller (not shown) coupled to LCU 99.

Imaging member 111 includes photoreceptor 206.

Photoreceptor 206 includes a photoconductive layer formed on an electrically conductive substrate. The photoconductive layer is an insulator in the substantial absence of light so that electric charges are retained on its surface. Upon exposure to light, the charge is dissipated. In various embodiments, photoreceptor 206 is part of, or disposed over, the surface of imaging member 111, which can be a plate, drum, or belt. Photoreceptors can include a homogeneous layer of a single material such as vitreous selenium or a composite layer containing a

photoconductor and another material. Photoreceptors can also contain multiple layers.

An exposure subsystem 220 is provided for image-wise modulating the uniform electrostatic charge on photoreceptor 206 by exposing

photoreceptor 206 to electromagnetic radiation to form a latent electrostatic image (e.g., of a separation corresponding to the color of toner deposited at this printing module). The uniformly-charged photoreceptor 206 is typically exposed to actinic radiation provided by selectively activating particular light sources in an LED array or a laser device outputting light directed at photoreceptor 206. In embodiments using laser devices, a rotating polygon (not shown) is used to scan one or more laser beam(s) across the photoreceptor in the fast-scan direction. One dot site is exposed at a time, and the intensity or duty cycle of the laser beam is varied at each dot site. In embodiments using an LED array, the array can include a plurality of LEDs arranged next to each other in a line, all dot sites in one row of dot sites on the photoreceptor can be selectively exposed simultaneously, and the intensity or duty cycle of each LED can be varied within a line exposure time to expose each dot site in the row during that line exposure time.

As used herein, an "engine pixel" is the smallest addressable unit on photoreceptor 206 or receiver 42 (FIG. 1) which the light source (e.g., laser or LED) can expose with a selected exposure different from the exposure of another engine pixel. Engine pixels can overlap, e.g., to increase addressability in the slow-scan direction (S). Each engine pixel has a corresponding engine pixel location, and the exposure applied to the engine pixel location is described by an engine pixel level.

The exposure subsystem 220 can be a write-white or write-black system. In a write-white or charged-area-development (CAD) system, the exposure dissipates charge on areas of photoreceptor 206 to which toner should not adhere. Toner particles are charged to be attracted to the charge remaining on photoreceptor 206. The exposed areas therefore correspond to white areas of a printed page. In a write-black or discharged-area development (DAD) system, the toner is charged to be attracted to a bias voltage applied to photoreceptor 206 and repelled from the charge on photoreceptor 206. Therefore, toner adheres to areas where the charge on photoreceptor 206 has been dissipated by exposure. The exposed areas therefore correspond to black areas of a printed page.

A development station 225 includes toning shell 226, which can be rotating or stationary, for applying toner of a selected color to the latent image on photoreceptor 206 to produce a visible image on photoreceptor 206. Development station 225 is electrically biased by a suitable respective voltage to develop the respective latent image, which voltage can be supplied by a power supply (not shown). Developer is provided to toning shell 226 by a supply system (not shown), e.g., a supply roller, auger, or belt. Toner is transferred by electrostatic forces from development station 225 to photoreceptor 206. These forces can include Coulombic forces between charged toner particles and the charged electrostatic latent image, and Lorentz forces on the charged toner particles due to the electric field produced by the bias voltages.

In an embodiment, development station 225 employs a two- component developer that includes toner particles and magnetic carrier particles. Development station 225 includes a magnetic core 227 to cause the magnetic carrier particles near toning shell 226 to form a "magnetic brush," as known in the electrophotographic art. Magnetic core 227 can be stationary or rotating, and can rotate with a speed and direction the same as or different than the speed and direction of toning shell 226. Magnetic core 227 can be cylindrical or non- cylindrical, and can include a single magnet or a plurality of magnets or magnetic poles disposed around the circumference of magnetic core 227. Alternatively, magnetic core 227 can include an array of solenoids driven to provide a magnetic field of alternating direction. Magnetic core 227 preferably provides a magnetic field of varying magnitude and direction around the outer circumference of toning shell 226. Further details of magnetic core 227 can be found in U.S. Patent No. 7,120,379 to Eck et al., issued October 10, 2006, and in U.S. Publication No. 2002/0168200 to Stelter et al., published November 14, 2002, the disclosures of which are incorporated herein by reference. Development station 225 can also employ a mono-component developer comprising toner, either magnetic or non- magnetic, without separate magnetic carrier particles.

As used herein, the term "development member" refers to the member(s) or subsystem(s) that provide toner to photoreceptor 206. In an embodiment, toning shell 226 is a development member. In another embodiment, toning shell 226 and magnetic core 227 together compose a development member.

Transfer subsystem 50 (FIG. 1 ) includes transfer backup member 113, and intermediate transfer member 112 for transferring the respective print image from photoreceptor 206 of imaging member 1 11 through a first transfer nip 201 to surface 216 of intermediate transfer member 112, and thence to a receiver (e.g., 42B) which receives the respective toned print images 38 from each printing module in superposition to form a composite image thereon.

Surface 216 can be compliant. Print image 38 is e.g., a separation of one color, such as cyan. Receivers are transported by transport web 81. Transfer to a receiver is effected by an electrical field provided to transfer backup member 113 by power source 240, which is controlled by LCU 99. Receivers can be any objects or surfaces onto which toner can be transferred from imaging member 111 by application of the electric field. In this example, receiver 42B is shown prior to entry into second transfer nip 202, and receiver 42A is shown subsequent to transfer of the print image 38 onto receiver 42 A.

Still referring to FIG. 2, toner is transferred from toning shell 226 to photoreceptor 206 in toning zone 236. As described above, toner is selectively supplied to the photoreceptor by toning shell 226. Toning shell 226 receives developer 234 from developer supply 230, which can include a mixer.

Developer 234 includes toner particles and carrier particles.

With reference to FIG. 3, a sequence of process steps for producing an electrical conductor on a receiver using an electrophotographic printer will be described herein below. FIG. 3 shows a flow diagram of a basic sequence of process steps for producing an electrical conductor on a receiver. In block 310, the process starts by providing a metallic toner having a composition including 60-90 wt. pet. of an aggregate of metallic particles and frit particles and 10-40 wt. pet polymeric binder particles, wherein the aggregate includes 40-90 wt. pet. metallic particles and 5-60 wt. pet. frit particles. In one embodiment, the aggregate includes at least 60 wt. pet. metallic particles and less than 40 wt. pet. frit particles. It is envisaged that for the formation of electrical conductors, it would be beneficial if the aggregate included at least 80 wt. pet. metallic particles and less than 20 wt. pet. frit particles. Furthermore, the metallic toner composition can include 75-85 wt. pet of the aggregate of metallic particles and frit particles and 15-25 wt. pet. of polymeric binder particles. In one embodiment, the polymeric binder is a polyester binder, i.e., the polymeric binder particles include polyester particles or molecules.

Optionally, the metallic toner composition can further include at least one of charge control agents in an amount of 0.1-5 wt. pet. and wax in an amount of 0.1 - 10 wt. pet. The metallic particles in the toner composition can have a volume weighted median diameter, for example as measured by a Coulter Multisizer of smaller than lOOnm, in one embodiment. The metallic particles can preferably be substantially spherical. The term "substantially spherical" can encompass also elliptical particles having a ratio of major axis to minor axis of smaller than 1:0.8.

In one embodiment, the metallic toner composition has toner particles having a volume weighted median diameter, for example as measured by a Coulter Multisizer, between 5 and 30um.

After providing the metallic toner in block 310, dimensions of a pattern for an electrical conductor to be formed are optionally selected based on the composition of the toner so that the resistance load per unit length of a resulting structure of metallic toner after applying and curing the toner is approximately 4 to 6 Ω cm along a direction of extension of the resulting structure, as shown by block 315. Block 315 is an optional step and the dimensions to be chosen here are the thickness and width (normal to the direction of extension of the resulting structure) of a toner structure. Other dimensions such as length (in the direction of extension) and shape of the structure are predefined by the pattern of the electrical conductor to be formed. Both the thickness and the width can influence the resistance load per unit length of a resulting structure of metallic toner after applying and curing the toner. These parameters are dependent on the toner composition, as the composition defines the amount of conductive metallic particles that will influence the resistance load per unit length of the resulting structure. The thickness of the toner structure can be limited by the toner coverage which can be achieved in a single toner layer and the number of toner layers that can be applied in an overlapping manner. The width of the structure can be limited by the pattern of the electrical conductor to be formed and the required spacing between adjacent conductive areas. Alternatively, these parameters can already be included in the pattern information for an electrical conductor, in which case the selection step can be dispensed with.

Next, a continuous layer of the metallic toner is applied in a selected pattern on a substrate using the electrophotographic printer in block 320. The selected pattern is chosen in accordance with a desired pattern of an electrical conductor to be formed. The term "continuous layer" refers to a continuous line or area, on which the metallic toner is to be applied. Several spaced lines or areas can be provided on the substrate in accordance with the electrical conductor to be formed. The term "continuous" also encompasses the toner particles forming voids and free spaces therebetween, as will be clear to the skilled person. When applying toner particles, on a microscale there will always be some voids between the actual particles, but the toner particles in the continuous layer should be contacting each other. A continuous layer can include multiple connected lines or other patterns with large gaps between them as long as each pattern is electrically conductive. In various embodiments, the continuous layer of the metallic toner is applied on the ceramic substrate using a compliant intermediate transfer member such as intermediate transfer member 112 (FIG. 2) with compliant surface 216 (FIG. 2).

Finally, in block 330, the metallic toner is cured by heating the metallic toner so that the metallic particles form an electrical conductor. Curing includes heating the toner particles to a temperature at which the polymeric binder particles and at least a part of the aggregate of the metallic particles and frit particles are heated above the glass point of said particles, i.e. they are at least partially melted. Formation of the electrical conductor is achieved by the metallic particles providing a continuous chain for an electrical current to flow through the cured toner. The electrical conductor can have voids οτ spaces filled by non- conducting particles, but will nevertheless provide a continuous current path formed by metallic particles contacting each other. During the curing process, the temperature can be chosen high enough that at least some of the polymeric binder particles evaporate out of the toner composition. Therefore, the overall amount of metallic particles in the cured toner can be higher than in the initial toner composition.

FIG. 4 shows another flow diagram, depicting another sequence of steps for producing an electrical conductor on a substrate. The sequence starts in step 410, which is identical to block 310 in FIG. 3. In block 410, a metallic toner is provided having a composition including 60-90 wt. pet. of an aggregate of metallic particles and frit particles and 10-40 wt. pet. polymeric binder particles, wherein the aggregate includes 40-95 wt. pet. metallic particles and 5-60 wt. pet. frit particles. The composition can again be varied or specified, as explained in accordance with FIG. 3. In FIG. 4, block 410 can again be followed by a selection block (not shown) for the dimensions of a pattern for an electrical conductor to be formed, similar to block 315 in FIG. 3. Alternatively, pattern-dimension information can be part of pattern information of an electrical conductor to be formed, which information can be provided from an external source.

Subsequently, in block 420, a first continuous layer of the metallic toner is applied in a select pattern on a receiver using the electrophotographic printer, similar to block 320 described above with reference to FIG. 3.

In block 430, the first toner layer is fixed to the receiver by heating the toner layer above the glass temperature of the polymeric binder, which is typically from 120-180°C. The fixing temperature is well below a curing temperature of the toner layer and the receiver is capable of withstanding the curing temperature. Fixing the first toner layer in the above manner leads to the toner layer obtaining certain stability with respect to disturbances such as mechanical disturbances caused by transport of the receiver or a subsequent application of one or more toner layers. Fixing thus keeps the first toner layer in the selected pattern. This fixing step in the sequence is an optional step, and the heating typically leads to an electrical discharge of the toner particles, which can be electrically charged during the application step. Alternatively, or additionally, the toner particles can also be electrically discharged by grounded electrodes or other structure means.

Next, in block 440, a second continuous layer of the metallic toner is applied in a selected pattern on the substrate on top of the previously applied layer, using the electrophotographic printer. The term "on top of the previously applied layer" relates to an at least partial overlap of the first and second continuous layers. In one embodiment, the overlap should be at least 80%.

Preferably at least 90%.

Application of the second continuous layer can be done by the same printing module of the electrophotographic printer, which was used for applying the first layer, or by a separate printing module, which can for example be arranged in line with the previously used printing module.

Subsequently, the second toner layer can again be fixed to the substrate by heating the toner layer above the glass temperature of the polymeric binder, as shown in block 450. Although not shown in FIG. 4, one or more additional layers of the metallic toner can be applied in the selected pattern on the substrate on top of the previously applied layers followed by an optional fixing step of the respectively applied toner layer. Thus, multiple layers of the metallic toner can be provided on top of each other on the substrate.

In block 460, a layer of non-metallic toner is applied on the substrate using the electrophotographic printer, said layer at least partially filling in free spaces in the selected pattern formed by the layers of metallic toner. Such a layer of non-metallic toner, especially in the free spaces in the selected pattern formed by the layers of metallic toner can for example provide insulation between different lines/areas in the selected pattern and can also form a more homogeneous toner layer. The application of non-metallic toner can again be followed by a fixing step and application of one or more additional layers of non-metallic toner. In particular, it is possible to apply layers of non-metallic toner such that a structure of multiple metallic and non-metallic toner layers is formed which has a substantially continuous and flat surface. This structure can help in reducing stresses within the multiple toner layers, especially the metallic toner layers, during a subsequent curing step. Such a curing step is shown in block 470, in which the toner is cured by heating the toner layer so that the metallic particles form an electrical conductor.

The above flow diagram shows a specific sequence of steps, in which, subsequent to the application of multiple layers of metallic toner, non- metallic toner is applied to the substrate. It is, however, also possible to apply only multiple layers of the metallic toner and not to apply any non-metallic toner to the substrate. Alternatively, it is also possible to first apply one or more non- metallic toner layers to the substrate, preferably leaving free spaces on the substrate according to a selected pattern and subsequently applying one or more continuous layer(s) of metallic toner in the selected pattern on the substrate. Also, metallic and non-metallic toner layers can be alternately applied to the substrate.

The invention is inclusive of combinations of the embodiments described herein. References to "a particular embodiment" and the like refer to features that are present in at least one embodiment of the invention. Separate references to "an embodiment" or "particular embodiments" or the like do not necessarily refer to the same embodiment or embodiments; however, such embodiments are not mutually exclusive, unless so indicated or as are readily apparent to one of skill in the art. The use of singular or plural in referring to the "method" or "methods" and the like is not limiting. The word "or" is used in this disclosure in a non-exclusive sense, unless otherwise explicitly noted.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations, combinations, and modifications can be effected by a person of ordinary skill in the art within the spirit and scope of the invention. PARTS LIST, 32, 33, 34, 35 printing module

print image

cured image supply unit

, 42A, 42B receiver

transfer subsystem

curing device fusing roller pressure roller fusing nip

release fluid application substation output tray

finisher

transport web cleaning station logic and control unit (LCU)0 printer

1 imaging member

2 transfer member

3 transfer backup member

1 transfer nip

second transfer nip

6 photoreceptor

charging subsystem

1 meter

meter

3 grid Parts List - continued

216 surface

220 exposure subsystem

225 development station

226 toning shell

227 magnetic core

230 developer supply

234 developer

236 toning zone

240 power source

310 block

315 block

320 block

330 block

410 block

420 block

430 block

440 block

450 block

460 block

470 block

Claims

CLAIMS:

1. A toner for use in electrophotographic printing, the toner having a composition including 60-90 wt. pet. of an aggregate of metallic particles and frit particles and 10-40 wt. pet. polymeric binder particles, wherein the aggregate includes 40-95 wt. pet. metallic particles and 5-60 wt. pet. frit particles.

2. The toner of claim 1, wherein the aggregate includes at least 60 wt. pet. metallic particles and less than 40 wt. pet. frit particles.

3. The toner of claim 2_} wherein the aggregate includes at least 80 wt. pet. metallic particles and less than 20 wt. pet. frit particles.

4. The toner of claim 1 , wherein the toner includes 75-85 wt. pet. of the aggregate and 15-25 wt. pet. polymeric binder particles.

5. The toner of claim 1 , wherein the polymeric binder particles include polyester.

6. The toner of claim 1, further including charge control agents in an amount of 0.1 to 5 wt. pet. or wax in an amount of 0.1 to 10 wt. pet.

7. The toner of claim 1 , wherein the metallic particles have a volume- weighted median diameter of smaller than lOOnm.

8. The toner of claim 1, wherein the metallic particles are substantially spherical.

9. The toner of claim 1 , wherein the toner includes toner particles having a volume-weighted median diameter between 5 and 30um.

10. The toner of claim 1 , wherein the toner is heat-curable at a temperature at which at least some of the polymeric binder particles evaporate.

11. A method for producing an electrical conductor on a substrate using an electrophotographic printer, the method comprising:

providing a metallic toner having a composition including 60-90 wt. pet of an aggregate of metallic particles and frit particles and 10-40 wt. pet. polymeric binder particles, wherein the aggregate includes 40-95 wt. pet. metallic particles and 5-60 wt. pet. frit particles;

applying a continuous layer of the metallic toner in a selected pattern on the substrate using the electrophotographic printer; and

curing the metallic toner by heating the metallic toner so that the metallic particles form the electrical conductor.

12. The method of claim 11 , wherein the aggregate includes at least 60 wt. pet metallic particles and less than 40 wt. pet. frit particles.

13. The method of claim 12, wherein the aggregate includes at least 80 wt. pet. metallic particles and less than 20 wt. pet. frit particles.

14. The method of claim 11, wherein the metallic toner includes 75-85 wt. pet. of the aggregate and 15-25 wt. pet polymeric binder particles.

15. The method of claim 11 , wherein the curing step includes heating the metallic toner to a temperature at which at least some of the polymeric binder particles evaporate out of the metallic toner composition.

16. The method of claim 15, wherein the curing step includes heating the metallic toner to a temperature at which at least 50 pet of the polymeric binder particles evaporate out of the metallic toner composition.

17. The method of claim 1 1, wherein the polymeric binder particles include polyester.

18. The method of claim 11 , further comprising selecting dimensions of the pattern for the electrical conductor based on the composition of the metallic toner so that the resistance load per unit length of a resulting structure of metallic toner after applying and curing the toner is approximately 4 to 6 Ω/cm along a direction of extension of the resulting structure.

19. The method of claim 11 , wherein the metallic toner further includes charge control agents in an amount of 0.1 to 5 wt. pet. or wax in an amount of 0.1 to 10 wt. pet.

20. The method of claim 11 , wherein the metallic particles have a volume-weighted median diameter of less than 1 OOnm.

21. The method of claim 11 , wherein the metallic particles are substantially spherical.

22. The method of claim 11 , wherein the metallic toner includes toner particles having a volume-weighted median diameter between 5 and 30um.

23. The method of claim 11 , wherein the continuous layer of the metallic toner is applied on the substrate using a compliant intermediate transfer member.

24. The method of claim 11 , further including printing two or more metallic toner layers on top of each other in the selected pattern.

25. The method of claim 24, further including, after printing a metallic toner layer and before printing another metallic toner layer on top thereof, the already printed metallic toner layer is electrically discharged.

26. The method of claim 11 , wherein the curing step includes heating the metallic toner above the melting temperature of the metallic particles.

27. The method of claim 11, wherein the curing step includes heating the metallic toner in a non-contact manner using at least one of the following: radiation curing, or convection curing, microwave or radio frequency curing.

28. The method of claim 11 , further including: providing a non-metallic toner;

applying at least one layer of the non-metallic toner in a selected pattern on the substrate using the electrophotographic printer; and

fixing the non-metallic toner on the substrate by heating the non- metallic toner.

29. The method of claim 28, wherein the non-metallic toner layer is applied inversely to the metallic toner to establish a substantially continuous toner layer having a substantially even height.