Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-01-22
2001-09-11
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S109200, C430S110400
Reexamination Certificate
active
06287740
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electrophotographic toners, and specifically to the composition of toner releasing agents and friction reducing agents.
BACKGROUND OF THE INVENTION
As conventional techniques related to waxes according to the present invention, for example, Japanese Patent Publication No. 8-12447 discloses a toner comprising no more than 10 free polyethylene wax particles per 100 toner particles, which improves fixation as well as offsetting resistance. Further, the same patent discloses a production method in which melt-kneading is carried out employing a binder with a viscosity of at least 1,000 poise and describes excellent offsetting properties and fluidity, minimal staining of a toner holding body and improved cleaning properties, through the addition of polyethylene wax.
In addition, Japanese Patent Publication Open to Public Inspection No. 9-62031 discloses that in a toner for developing an electrostatic image comprising toner particles as well as low molecular weight wax particles, the melt index of said toner is at least 10; 10 to 500 of said low molecular weight wax particles are present per 10,000 toner particles, and long chain alcohols are employed as said low molecular weight wax.
However, these conventional techniques have cause problems in which in the case of employing an organic photoreceptor during blade cleaning, a toner abrades the photoreceptor to lower the sensitivity due to abrasion of the photoreceptor and to shorten the lifetime of the photoreceptor. Further, nitrates formed due to corona discharging during charging and transfer processes accumulate on the surface of the photoreceptor, and when left at high temperature and humidity, a problem occurs in which image smear is caused. Still further, along with the higher speed of roll fixing as well as lower weight load, a conventional technique in which wax is dispersed into the interior of the toner to be included has caused problems of offsetting properties due to the low bleeding rate of the wax.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a toner which improves the durability of the developer material itself, as well as the durability of a photoreceptor. At the same time, another object is to provide a toner which minimizes image smear at high temperature and humidity. Still another object is to provide a toner which exhibits excellent fixation as well as offsetting resistance.
The aforesaid objects of the present invention are accomplished by the embodiments described below.
(1) In a toner comprising at least a binder resin and a colorant, the toner comprises a wax, composed of at least one of polypropylene wax, polyethylene wax, paraffin series wax, amide wax, and fatty acid ester wax, and further, the adhesion power index of wax to toner particles is 0.7 to 2.2. An amount of the wax is preferably 0.5 to 8 percent by weight with reference to toner. More preferably 3.8 to 7.4 percent by weight.
(2) The toner described in (1), which is characterized in that the volume average particle diameter Dw of a wax and the volume average particle diameter Dt of a toner are in a ratio of 0.5<Dw/Dt<0.9, and the ratio of wax component having a particle diameter of 4 to 12 &mgr;m is between 50 and 85 percent, in terms of the number of particles.
(3) The toner described in (1) or (2) which is characterized in that the shape of said wax is substantially amorphous.
(4) In a toner comprising at least a binder resin as well as a colorant, an image forming method which is characterized in that employing a two-component developer material prepared by mixing with a carrier said toner, comprising at least one of polypropylene, polyethylene, paraffin wax, amide wax, and fatty acid esters, and further, having an adhesion index of 0.7 to 2.2, after a negatively charged organic photoconductor is subjected to toner development/transfer, the toner which is not transferred to a transfer material and remains on the photoreceptor is recovered employing a cleaning device in which the cleaning blade, composed of a urethane rubber material, is brought into contact with said photoreceptor at an angle counter to the direction of movement and under a contact load of 18 to 30 g/cm, and the recovered toner is repeatedly employed by returning it to the development device or toner supply device.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be detailed below.
It has become possible to extend the lifetime of a photoreceptor in such a manner that a protective layer is formed on the surface of the photoreceptor through an appropriate supply of the wax during toner development, and the photoreceptor is thereby subjected to reduced abrasion.
It has also become possible to minimize image smear in such a manner that because fresh wax for protecting photoreceptor is constantly supplied and consumed, there occurs no accumulation of nitrate compounds which cause such image smear.
Through melt-adhesion of the wax to the carrier or the development rollers, it has become possible to minimize background stain as well as toner scatter due to insufficient charging.
When a toner contains an appropriate amount of wax, a protective layer is formed on a photoreceptor, to exhibit minimal abrasion of the photoreceptor. However, problems occur in which when excessive wax exists, streak-like image defects result due to photoreceptor filming and the melt-adhesion of the wax to the carrier or development rollers, which degrades charging function and shortens the lifetime of the developer material.
Both the minimized photoreceptor abrasion and the prevention of melt-adhesion to a toner holding body are accomplished by adjusting the adhesion power index of the wax to toner particles to the range specified in the present invention.
Furthermore, with the intention of minimizing streak-like image defects due to excessive filming on the photoreceptor, the toner of the present invention is preferably employed in an image forming method, in which the toner which is not transferred to a transfer material and remains on the photoreceptor, is brought into contact with a cleaning blade composed of an elastic material under a blade load of at least 18 g/cm.
In the present invention, the ratio of the volume average particle diameter Dw of a wax to the average volume particle diameter Dt of a toner is in the range of 0.5<Dw/Dt<0.9. In addition, the ratio of wax components having a particle diameter of 4 to 12 &mgr;m is preferably between 50 and 85 percent in terms of the number of particles, and is more preferably between 55 and 75 percent.
Of the types of photoreceptor protection wax, a polypropylene containing wax is preferred, while a low molecular weight polypropylene containing wax is more preferred.
Wax employed in the invention is exemplified.
Paraffin wax: n-paraffin having carbon atom numbers of 20 to 36 and isoparaffin (microcrystaline wax) having carbon atom numbers of 31 to 50.
Polyethylene wax having molecular weight of 1,000 to 5,000.
Fatty acid ester:
each of R
1
and R
2
is a group having carbon atom numbers of 16 to 32, preferably an alkyl or alkenyl group, more preferably an alkyl group.
each of R
1
and R
2
is a group having carbon atom numbers of 16 to 32, preferably an alkyl or alkenyl group, more preferably an alkyl group, and R
3
is a group having carbon atom numbers of 1 to 32, preferably alkylene group.
Amide wax:
each of R
1
and R
2
is a group having carbon atom numbers of 16 to 32, preferably an alkyl or alkenyl group, more preferably an alkyl group.
each of R
1
and R
2
is a group having carbon atom numbers of 16 to 32, preferably an alkyl or alkenyl group, more preferably an alkyl group, and
R
3
is a group having carbon atom numbers of 1 to 32, preferably alkylene group.
In the above formulae, alkyl group may be straight or branched.
Concrete example of the amide wax includes stearic acid amide, ethylenebisstearic acid amide, methylenebisstearic acid amide, oleic acid amide, palmitic acid amide and behenic acid amide.
Preferab
Ohmura Ken
Oshiba Tomomi
Bierman Jordan B.
Bierman, Muserlian and Lucas
Goodrow John
Konica Corporation
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