Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-03-26
2004-01-13
Dote, Janis L. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108300, C430S108700
Reexamination Certificate
active
06677094
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for non-magnetic monocomponent development which is employed to develop an electrostatic image formed using electrophotographic methods, electrostatic recording methods, and electrostatic printing methods.
2. Description of Related Art
Examples of developing methods, which have been conventionally employed in electrophotographic methods include a two-component developing method and a monocomponent developing method. The two-component developing method is a method of charging insulating fine powders containing a binder resin as a main component, that is, an insulating toner and a magnetic carrier, to form a magnetic brush by friction, and developing an electrostatic latent image formed on a photosensitive member by using the magnetic brush. The monocomponent developing method can be further classified into a magnetic monocomponent developing method and a non-magnetic monocomponent developing method. The magnetic monocomponent developing method is a method of developing using a toner for magnetic monocomponent development, whereas the non-magnetic monocomponent developing method is a method of forming a toner for non-magnetic monocomponent development on a developing roller in the form of a thin layer and developing with or without contacting with a photosensitive member.
In particular, the non-magnetic monocomponent developing method, among these developing methods, requires that the toner for non-magnetic monocomponent development should be charged with a sufficient charge amount equivalent to the two-component developing method in order to obtain a good image without carrier. It is indispensable to uniformly control the thickness of the toner layer on the developing roller.
To provide toner particles with a sufficient charge amount or to uniformly control the thickness of the toner layer, a rubber or metal blade member is used by being press-contacted with the developing roller at present. There is proposed a technique of charging a conventional toner for non-magnetic monocomponent development with a relatively high charge amount by using a binder resin such as styrene-acrylic copolymer resin and a colorant as main components and mixing them with a charge control agent such as metal-containing azo dye.
However, a conventional toner for non-magnetic monocomponent development has a problem in that a large amount of an untransferred toner remains on a photosensitive member. When a large amount of the untransferred toner remains on the photosensitive member, a decrease in image density occurs. In a method having a photosensitive member cleaning mechanism, a filming phenomenon also arises wherein a toner is deposited and fused on the surface of a photosensitive member due to a cleaning member press-contacted with the photosensitive member, and/or consumption of the toner is sometimes increased. In a method in which no photosensitive member cleaning mechanism is used, after the toner is transferred onto a transfer medium since the photosensitive member is discharged in the state where the untransferred toner is remaining, and is then charged directly by a charging member, ghosting sometimes appears in a cycle corresponding to the circumference of the photosensitive member as a result of the occurrence of a difference in charge amount between the portion where the untransferred toner remains and the portion where the untransferred toner does not remain.
As used herein, “ghosting” refers to a phenomenon wherein, if a part of developed toner remains on the photosensitive member without being transferred in a previous printing cycle, the light density image remaining from the previous printing cycle appears in light-tone portions, such as non-image or half-tone portions in a new image in a cycle corresponding to the circumference of the photosensitive member, as a result of the occurrence of a difference in charge amount between the remained image portion of the previous cycle and the non-image portion of new cycle.
To solve these problems, as disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 11-202546, it has conventionally been proposed to improve the peelability of a toner from a photosensitive member by applying silicone oil to the surface of toner particles. It has also been proposed that the surface of inorganic fine particles such as silica particles is treated with silicone oil and the treated particles are applied on the surface of the toner particles, thereby to control the charging property and fluidity and to improve the transfer property.
However, none of these methods could sufficiently prevent the untransferred toner from remaining on the surface of the photosensitive member. It was difficult for an apparatus having no cleaning mechanism, which has attracted special interest recently in view of size reduction of the apparatus and avoiding of photosensitive member abrasion, to prevent ghosting from occurring.
In the conventional method of controlling the thickness of a toner layer on the surface of a developing roller thinly and uniformly, aminosilanes, and especially amino-modified silicone oil for imparting the transferrability, are used as a treating agent for inorganic fine particles having a reverse polarity in the case of a negatively chargeable toner. The treating agent having an amino group has a problem in that the charging property drastically varies between high temperature/high humidity environments and low temperature/low humidity environments because of its weak hydrophobicity as compared with a methyl group.
BRIEF SUMMARY OF THE INVENTION
In light of the above-described problems in conventional toners for non-magnetic monocomponent development, the present invention has been made, and an object thereof is to provide a toner for non-magnetic monocomponent development, which sufficiently maintains the image density and prevents fogging in the non-image portion by reducing the untransferred toner on a photosensitive member, and does not produce ghosting when applied to a non-magnetic monocomponent developing device having no cleaning mechanism.
The present invention is directed to a toner for non-magnetic monocomponent development, comprising toner particles and an external additive adhered on the surface of the toner particles, wherein the external additive comprises inorganic fine particles (A), which are surface-treated with aminosilane and dimethylpolysiloxane and have a polarity opposite to that of the toner, and inorganic fine particles (B) having the same polarity as that of the toner.
As the inorganic fine particles (A), silica particles (A′) having a polarity opposite to that of the toner can be employed. As the inorganic fine particles (B), silica particles (B′) having the same polarity as that of the toner can be employed.
A BET specific surface area of the silica particles (A′) is preferably within a range from 40 to 90 m
2
/g, and a BET specific surface area of the silica particles (B′) is preferably within a range from 100 to 300 m
2
/g.
A weight ratio of the silica particles (A′) to the silica particles (B′) is preferably within a range from 10:90 to 50:50.
According to the present invention, it is possible to control the amount of the developing toner, in other words, the amount of toner consumed, to be the minimum necessary, and to reduce the untransferred toner on a photosensitive member by adhering an external additive using inorganic fine particles having the same polarity as that of the toner in combination with inorganic fine particles having a polarity opposite to that of the toner on toner particles. Consequently, the present invention exerts an effect capable of preventing the occurrence of surface fogging of the photosensitive member due to poor cleaning in the case of a device having a cleaning mechanism, and capable of preventing the occurrence of ghosting in the case of a device having no cleaning mechanism.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will n
Dote Janis L.
Nixon & Vanderhye P.C.
Tomoegawa Paper Co. Ltd.
LandOfFree
Toner for non-magnetic monocomponent development does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Toner for non-magnetic monocomponent development, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Toner for non-magnetic monocomponent development will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3261699