Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-10-19
2003-04-08
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C428S195100, C428S413000, C428S480000, C428S484100
Reexamination Certificate
active
06544709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrophotographic recording media suitable for use with toner printing systems such as copiers and laser printers. Particularly, the media comprise an opaque substrate material coated with a toner-receptive layer.
2. Brief Description of the Related Art
In recent years, consumers and businesses have turned to electrophotographic printing systems (e.g., color copiers and color laser printers) to produce digital photographic images on a variety of products. Consumers and businesses can now create digital color images on greeting cards, posters, calendars, newsletters, business cards, advertising brochures, and the like. Manufacturers have introduced new digital cameras, computers, software, color copiers, color laser printers, and imaging media to meet growing demand in the home and business markets.
Generally, in an electrophotographic printing process, toner is used to form an image (i.e., photo, illustration, text, and the like) on a recording medium. Typically, the recording medium comprises a specially coated paper or film substrate. The toner comprises a binder resin and colorant particles, and it is magenta, cyan, yellow, or black colored. The process involves electrically charging a photoconductive surface of a drum or belt in the printing device (copier, printer, etc.). Light is directed at the photoconductive surface to form a latent image. The latent image on the photoconductive surface comprises electrostatic charges replicating the image that will be printed onto the medium. Toner particles are brought into contact with the photoconductor, and the particles are attracted to the charged regions on the photoconductive surface. As the recording medium passes over the toner-containing photoconductive surface, the toner particles are transferred to the medium. The toner image then can be fixed by briefly heating the medium. The heat fuses the toner to the medium creating a final imaged product.
Typically, in the fusing step, the medium passes between heated fuser rollers. Many color copiers and color laser printers contain fuser rollers coated with oil (e.g., silicone oil) to prevent smearing of the image and sticking of the imaged medium to the surface of the roller. For example, the Xerox Docucolor 12 color copier contains such oil-coated fuser rollers. However, such oil-based copiers and printers can have high maintenance costs. Recently, copiers and printers that do not use oil in their fusing stations have been introduced. Several popular models of color laser printers, such as Hewlett Packard (HP) 4500 and Xerox Phaser 790, do not contain oil-coated fuser rollers.
The quality of the printed image is dependent on many factors including the composition of the paper or film media. There is a growing demand for media that can produce digital images of similar quality to traditional photographic camera prints. For example, traditional photo developing machines create a glossy finish on the photo print. Many consumers find the glossy finish of conventional photo prints appealing. High gloss digital photo prints would also be desirable.
McAneney et al., U.S. Pat. No. 6,177,222 B1 discloses photographic papers suitable for use in electrophotographic imaging systems. The paper is coated with a polyester coating having a thickness of about 1 to about 15 microns. According to the patent, the polyester coating absorbs the fused toner particles, thereby resulting in a smooth imaged surface. The patent describes the paper as capable of forming a glossy image, wherein the gloss is uniform across the image. Particularly, the images have a gloss value from about 50 GU to about 100 GU and a gloss variation between about 20 GU to about 10 GU.
Cobum et al., U.S. Pat. No. 6,060,203 discloses coated papers for producing photographic-like output having a uniform glossy finish in an electrostatographic printing process. The printing system comprises: a) a toner comprising a polyester resin having a glass transition temperature (T
gt
), and b) a coated substrate comprising a polyurethane, acrylic, or styrene-acrylic copolymer-based coating having a glass transition temperature (T
gc
). The patent discloses that good results are obtained when (T
gc
) is less than or equal to (T
gt
). The patent further discloses that coatings having high gloss values of 60 to 95% after fusing are preferred.
Chernovitz et al., U.S. Pat. No. 5,837,351 discloses a multi-purpose sheet suitable for use in manual drafting, ink-jet and electrophotographic printing and copying applications. The sheet comprises a base support coated with an aqueous dispersion of a cross-linkable polymer, a cross-linking agent, and pigment. The patent describes transparent vellum paper, film, and opaque paper as suitable base supports. The patent describes bisphenol A—based epoxy resins as suitable cross-linkable polymers and silica, silicate, and calcium carbonate as suitable pigments. According to the patent, the cross-linkable binder polymers coalesce and cross-link to produce a hard discrete surface layer that is ink-wettable and has controlled surface resistivity.
Matthew, U.S. Pat. No. 5,145,749 discloses an electrophotographic paper comprising a coating composition adhered to a substrate. The patent discloses that the coating composition is erasable by local breakage of adhesion of the coating to the substrate. The coating comprises an aqueous emulsion of an acrylic polymer and polymethylmethacrylate, and a wax is selected from polyalkane and polyalkene waxes. The patent discloses that there is a direct and proportional increase in erasability as the amount of wax in the coating composition is increased. According to the patent, the erasability of the coating is improved by replacing at least 15 wt. % of the binder with the wax.
Although some of the above-described media may be capable of providing digital images of adequate quality for some applications, there is a need for media capable of recording improved colored images. Particularly, there is a need for media that can produce high quality digital color images using printers and copiers that do not contain oil-coated fuser rolls. The present invention provides such electrophotographic media.
SUMMARY OF THE INVENTION
The present invention relates to an electrophotographic recording medium comprising an opaque substrate. The front surface of the medium is coated with a toner-receptive layer comprising a resin selected from the group consisting of epoxy and polyester resins having a melting point in the range of about 105° C. to about 200° C., and wax having a melting point in the range of about 90° C. to about 200° C. The amount of wax in the layer is no greater than 14% by weight based on total weight of the layer. The recording~medium has a surface gloss of at least 70 GU.
Cellulosic materials or polymeric films are suitable opaque substrates. The epoxy resin can be derived from bisphenol A and epichlorohydrin, and the wax can be hydrocarbon (e.g., polyethylene or polypropylene), hydrohalocarbon, ester-containing, synthetic, or natural (e.g., carnauba) waxes. Suitable anti-static agents include cationically and anionically conductive polymers. The toner-receptive layer can further comprise pigment particles such as silica, calcium carbonate, kaolin, aluminum hydroxide, starch, polystyrene, and poly(methyl methacrylate) particles. The coat weight of the toner-receptive layer can be in the range of about 1 to about 15 grams per square meter (gsm). The substrate can have a thickness in the range of about 50 microns (2 mils) to about 200 microns (8 mils).
In one embodiment, the back surface of the medium is also coated with the above-described toner-receptive layer so that the medium is capable of being imaged on either of its surfaces.
The present invention also encompasses a process for producing an image on the electrophotographic recording medium. The process comprises the steps of: a) providing an electrophotographic recording medium as described above; b) applying toner to form an
Chin Janice Lee
Wang John
Wu George
Arkwright, Inc.
Barlow Josephs & Holmes, Ltd.
Chapman Mark A.
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