Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-11-29
2002-12-31
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S137150
Reexamination Certificate
active
06500593
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a toner for developing an electrostatic image in an image-forming process such as electrophotography or electrostatic printing, or a process for producing a toner for forming a toner image in a toner-jet type image-forming method. More particularly, this invention relates to a process for producing a toner used in a fixing method in which a toner image formed using the toner is fixed to a transfer medium such as a printing sheet under application of heat and pressure.
2. Related Background Art
In order to render visible an electric or magnetic latent image formed on a recording member, an image-forming method is available in which electroscopic or magnetosensitive fine particles called a toner are attracted to the latent image to form a visible image. It may typically include electrophotography, and a number of methods are known as methods therefor as disclosed in, e.g., U.S. Pat. No. 2,297,691. In this electrophotography, copies are commonly obtained by forming an electrostatic latent image on a photosensitive member by various means, utilizing a photoconductive material, subsequently developing the latent image by the use of a toner to form a toner image, transferring the toner image to a transfer medium such as paper as occasion calls, and thereafter fixing the toner image to the transfer medium by the action of heat, pressure or solvent vapor.
In recent years, the above technique has become used in output means, i.e., what is called printers, of computers, word processors and so forth because of its high image quality and stillness. Usually, toners used in printers and copying machines are fine particles composed chiefly of a resin, a colorant such as a magnetic material, carbon black, a dye or a pigment and a wax, and have particle diameters usually ranging from 6 to 30 &mgr;m. Toners are commonly produced by mixing and melting a colorant comprising a dye or pigment or a magnetic material in a thermoplastic resin to disperse the colorant uniformly therein, followed by fine pulverization and classification to obtain toners having a desired particle diameter. This method is stable as a technique, and enables relatively easy management of materials and production steps.
Meanwhile, a method of producing a toner by polymerization, in particular, a method of producing a toner by what is called suspension polymerization is proposed. Such a method is disclosed in, e.g., Japanese Patent Publication Nos. 36-10231 and 51-14895 and Japanese Patent Application Laid-Open Nos. 53-17735, 53-17736 and 53-17737. This method is a method in which a binder resin and materials to be incorporated in the toner, including a colorant such as a dye or a pigment (e.g., a magnetic material or carbon block), a charge control agent, and a release agent such as wax or silicone oil, are dissolved or dispersed in a polymerizable monomer optionally together with a polymerization initiator and a dispersant to prepare a polymerizable composition, which is then dispersed in an aqueous continuous phase containing a dispersion stabilizer by means of a dispersion apparatus to form a dispersion of fine particles, and this dispersion is polymerized and then solidified to obtain toner particles having any desired particle diameter and composition. This method has no pulverization step, and is expected to bring about the effect of energy saving, improvement in process yield and cost reduction.
As a method of improving print quality, studies are energetically made on a technique by which the latent image can faithfully be reproduced by making the particle diameter of the toner smaller. However, making the particle diameter smaller makes the quantity of toner per unit are smaller, and hence the coloring power per unit volume of the toner must be made higher in order to attain the desired image density. As a means therefor, it is common to use a means by which the colorant dye or pigment is introduced in a larger quantity. There, however, is a problem that pigments, in particular quinacridone pigments, used as colorants of toners are no expensive as to result in an increase in the production cost. Accordingly, in order to make the coloring power of dyes and pigments themselves higher and improve the transparency of OHP images, studies are energetically made on how the dispersion of dyes and pigments in the interior of toner particles be improved.
In order to improve the dispersion of dyes and pigments, it is commonly important to make the dyes and pigments readily compatible with resins. Accordingly, the dyes and pigments are subjected to surface treatment. Proposals on the surface treatment of dyes and pigments to improve their dispersibility are disclosed in Japanese Patent Application Laid-open No. 11-119461, Japanese Patent No. 2800558 and so forth. There, however, has been room for improvement with regard to the dispersibility of pigments.
In the case of pulverization toners, the surface treatment of dyes and pigments must be regulated in conformity with the composition of binder resins, and there has been a problem that any good state of dispersion can not be attained if the matching of the both is improper.
In the case of polymerization toners, the surface treatment of dyes and pigments is made in many cases, most of which, however, is to make hydrophobic treatment with silane coupling agents or to make a pigment dispersant (which is a polymer having a polar group) adsorbed on the particle surfaces of a colorant so that the pigment can be prevented from agglomerating.
In the case when such a pigment dispersant is used, the state of dispersion to a certain extent can be achieved. However, the pigment may undergo re-agglomeration in post steps of drying, shaping, polymerization reaction and so forth, or, in the production of polymerization toner in an aqueous medium, the presence of polar groups on the pigment particle surfaces may cause the migration of pigment to toner particle surfaces, resulting in a lowering of charging performance and environmental stability.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a toner having solved the above problems, and a process for producing the toner.
More specifically, an object of the present invention is to provide a toner having superior coloring powder and transparency, and a process for producing such toner.
Another object of the present invention is to provide a toner having a pigment added in a small quantity, and having achieved a cost reduction, and a process for producing such toner.
Still another object of the present invention is to provide a toner which does not cause any migration of pigment to toner particle surfaces and has superior charging performance and environmental stability, and a process for producing such toner.
To achieve the above objects, the present invention provides a toner containing at least a binder resin, a pigment and a pigment dispersant:
the pigment dispersant having a structure represented by the following Formula (1):
wherein at least one of R
1
and R
2
is a substituent X
1
represented by
where Y
1
is an oligomer or a polymer, and the other is a hydrogen atom.
The present invention also provides a toner containing at least a binder resin, a pigment and a pigment dispersant;
the pigment dispersant having a structure represented by the following Formula (2):
wherein at least one of R
3
and R
4
is a substituent X
2
represented by
where Y
3
and Y
4
are each a substituent selected from the group consisting of H, CH
3
, an oligomer and a polymer,
and the other is a hydrogen atom.
The present invention still also provides a process for producing the above toner.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The pigment dispersant according to the present invention has a structure wherein a quinacridone molecular skeleton which is readily adsorptive on the colorant pigment and an oligomer or polymer which has good affinity for the solvent and for the resin serving as a toner binder are covalently bonded. Als
Abe Koji
Itabashi Hitoshi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Goodrow John
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