Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1998-01-22
2001-10-02
Brunsman, David (Department: 1755)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S201000, C106S311000
Reexamination Certificate
active
06296981
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of fusing toner to paper using hydrofluorocarbons or perfluorinated C
1
-C
4
alkyl alkyl ether. The invention further pertains to a composition suitable for cold fusion which employs hydrofluorocarbons or perfluorinated C
1
-C
4
alkyl alkyl ethers as toner fusing agents.
BACKGROUND OF THE INVENTION
It is known in the art that hot fusion laser printing on a substrate such as paper includes the steps of character generation, character transfer to the paper, and subsequent character fusion on the paper. Character fusion by the hot fusion laser printing process creates a permanent image on the paper by heating characters which have been transferred onto the paper. The characters are typically composed of colored, polymeric toner powder. The toner is ordinarily composed of a polymer such as polyester, styrene/acrylate polymer or polyvinyl butyryl resin and a pigment such as carbon black.
In comparison to the hot fusion laser printing process, the known cold fusion process achieves significantly higher printing speeds. The cold fusion process provides a solvent laden vapor zone in which a fusing agent is used to fuse together, and to the paper, toner partides as the paper is passed through the vapor zone. Compositions such as blends of trichlorotrfluoroethane (CFC-113) and acetone as well as dichlorofluoroethane (HCFC-141
b
) have been used as fusing agents in the cold fusion process. U.S. Pat. No. 5,333,042 teaches a cold fusion method using various hydrochlorofluorocarbons.
However, in recent years, chlorine containing hydrochlorofluorocarbons have proven to be environmentally unacceptable. Therefore, a need exists for environmentally acceptable fusing agents.
DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
It is the unexpected discovery of the invention that satisfactory fusing of a toner composition may be achieved when using a toner fusing agent comprising a chlorine-free hydrofluorocarbon or a perfluorinated alkyl alkyl ether. Thus, the invention provides a method of fusing a toner composition comprising: contacting the toner composition with a toner fusing agent, which toner fusing agent comprises at least one chlorine-free hydrofluorocarbon, perfluorinated C
1
-C
4
alkyl alkyl ether or a mixture thereof. The invention also provides a toner fusing agent which comprises a stable, uniform mixture of at least one chlorine-free hydrofluorocarbon, perfluorinated C
1
-C
4
alkyl alkyl ether or mixture thereof and at least one toner stabilizer.
In the process of the present invention, a fine black powder, generally referred to as toner, applied in the form of characters onto a substrate, such as paper, is passed through a vapor of at least one chlorine-free hydrofluorocarbon or perfluorinated C
1
-C
4
alkyl alkyl ether or a mixture thereof. Useful toners are well known in the art and typically are fine powders of polyester, styrene/acrylate polymer or polyvinyl butyryl polymer and a pigment such as carbon black. These toners are commercially available as Canon NP G-Z and Canon CLC 500, among others. Characters may be generated by a computer and unfused toner characters applied to a substrate such as paper or film base by any of a variety of laser printers known in the art. Suitable laser printers are commercially available from Canon, Hewlett Packard, Brother and other manufacturers. These unfused toner characters are then contacted with a toner fusing agent in a process called cold fusion. The cold fusing process is more fully described in U.S. Pat. No. 5,333,042 which is incorporated in its entirety herein by reference.
The toner may be applied to a substrate by any means known in the art. For example, a computer may begin the printing process by signaling a laser printer to retrieve a substrate, such as a blank sheet of paper, from an input tray and transferring it to an input station. The input station leads the paper to a position adjacent to a photosensitive drum. Characters are generated by forming them on a rotating drum in the laser printer. Initially, the surface of the photosensitive drum is charged to a positive polarity. Subsequently, a laser in conjunction with an acousto-optical deflection system, a polygon mirror and a laser optics assembly, selectively forms characters on portions of the surface of the photo-sensitive drum by removing the charge in character areas. Thus, only the areas occupied by laser generated characters have a neutral polarity on the photo-sensitive drum, while the remaining area of the photosensitive drum remains positively charged.
Continuous rows of dots are formed on the rotating photosensitive drum creating a representation of the character to be printed. As will be appreciated by one skilled in the art, “character” as used in this context refers to any graphic figure, expression, representation, or any part thereof generated on the. polarized photosensitive drum. The photosensitive drum is rotated past a developer station which contains a polyester toner or styrenic polymer toner. The toner is positively charged and is applied across the width of the rotating photosensitive drum by the developer station. The toner, having a positive charge, is repelled into the charge removed areas of the photosensitive drum to represent the characters that will be printed. This process is well known to the art as, for example, in U.S. Pat. No. 4,311,723 which is incorporated herein by reference.
Character transfer occurs as the paper, which is energized with a very strong negative charge moves past a transfer station. Character transfer is accomplished since the differential between the charged paper and the toner is so strong that the toner is attracted away from the surface of the photosensitive drum onto the paper. The toner is held to the paper by the charge difference, and at this stage could be blown or brushed off the paper. A cold fusion step is subsequently performed to cause the toner to adhere securely to the paper. Upon completion of character transfer, the paper is transported by means of a paper transport mechanism to a cold fusing station.
The process of fusing the toner to the paper is accomplished by forming a vapor bath of a toner fusing agent in a cold fusion station, and passing the unfused toner through the vapor bath to achieve cold fusion of the characters. After toner transfer to the substrate, the photosensitive drum rotates past a corona discharge which discharges the positively polarized areas of the photosensitive drum. Thereafter, a cleaning brush removes excess toner for recycling as well as to electrically clean the photosensitive drum. Subsequently, the corona discharge eleclrically charges the surface of the drum with a positive charge. These steps are then repeated for additional printing.
In the process of the invention, a vapor bath is created by forming vapors of a toner fusing agent containing at least one chlorine-free hydrofluorocarbon, perfluorinated C
1
-C
4
alkyl alkyl ether, or mixtures thereof by heating the agent in a cold fusion station or chamber. The chlorinefee hydrofluorocarbons and perfluorinated C
1
-C
4
alkyl alkyl ethers have a zero ozone depletion potential and a global warming potential of not more than about 1600 on a 100 year time horizon. The most preferred toner fusing agents of this invention generally have no flash point as determined by ASTM D 56-87.
Suitable chlorine hydrofluorocarbons for use in this invention non-exclusively include HCF
2
CHFCF
2
CH
2
F(HFC-356pecq); CF
3
CF
2
CH
2
CH
2
F (HFC-356mcfq); CF
3
CFHCFHCF
2
CF
3
(HFC-43-10); HCF
2
CHFCHFCF
2
H (HFC-356peep); HCF
2
CHFCF
2
H (HFC-245ea); CF
3
(CF
2
)
2
CH
2
CH
3
(HFC-467mccf); (CF
3
)
2
CFCH
2
CH
3
(HFC-467 tertiary); H(CF
2
)
4
CH
2
F (HFC-449pccc); CF
3
(CF
2
)
3
CH
2
CH
3
(HFC-569mccc);and C
8
H
6
F
10
(HFC-1345 dimers). These fluorocarbons are either commercially available or may be prepared by any means well-known in the art. Of these, the preferred fusing agents are HCF
2
CHFCF
2
CH
2
F(HFC-356pecq); HCF
2
CHFCHFCF
2
H (HFC-356peep); HCF
2
Allied-Signal Inc.
Brunsman David
Szuch Colleen D.
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