Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-02-06
2002-08-27
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...
C430S110300, C430S126200, C430S137140
Reexamination Certificate
active
06440627
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a toner for developing an electrostatic image used upon developing an electrostatic image formed by an electrophotographic process or an electrostatic recording process with a developer, and a process for preparation of the toner, as well as a developer for an electrostatic image and a process for forming an image using the toner.
BACKGROUND OF THE INVENTION
A method for visualizing image information through an electrostatic image, such as an electrophotographic process and an electrostatic recording process, is being applied to various fields of art. In the electrophotographic process, an electrostatic image is formed on a photoreceptor by charging and exposing steps and then developed with a developer containing a toner, followed by being visualized through transferring and fixing steps.
The developer used herein includes a two-component developer formed with a toner and a carrier, and a one-component developer using a magnetic toner or a non-magnetic toner solely. As a production process of a toner used in these developers, a kneading and pulverization method has been mainly employed, in which a thermoplastic resin is melted and kneaded with a pigment, a charge controlling agent and a releasing agent, such as a wax, and after cooling, the mixture is finely pulverized. To particles of a toner produced by the kneading and pulverization method, inorganic fine particles or organic fine particles are added depending on necessity to the surface of the particles of the toner for improving the fluidity and the cleaning property.
In recent years, a production process of a toner by a wet production process is also proposed. For example, JP-A-63-282749 and JP-A-6-250439 propose an emulsion polymerization aggregation method, in which a dispersion of resin particles is prepared by emulsion polymerization, and a dispersion of a colorant is prepared by dispersing in an aqueous medium (solvent), both of which are mixed to form aggregated particles corresponding to a toner particle diameter, followed by fusing by heating to produce a toner.
A demand of high image quality is being increased in recent years owing to widespreading of color images. In a digital full color duplicator or printer, a color original image is subjected to color separation by filters of B (blue), R (red) and G (green), and latent images formed with dots of a diameter of from 20 to 70 &mgr;m corresponding to the original image are developed with developers of Y (yellow), M (magenta), C (cyan) and BK (black) by utilizing a subtractive color mixing function. Therefore, colorants contained in the developers greatly influence the image quality. Important factors of the colorants (Y, M and C) added to the toners include good transparency and high coloring power. It has been conventionally difficult to satisfy the factors particularly in a yellow pigment, and various investigations have been made.
In a yellow toner containing a yellow pigment, it is important to have good transparency that the crystalline diameter of the yellow pigment itself is small, and the average particle diameter of the colorant in the toner is small. In the case where the average particle diameter of the colorant is large or the colorant contains a large amount of coarse particles due to aggregation of the yellow pigment itself or aggregation caused in the toner, the OHP transparency is deteriorated owing to deterioration in light transmissibility of the toner. It brings about other problems, such as isolation of the colorant from the toner resin, and deterioration in charging property due to exposure of the colorant on the surface of the toner. In some kinds of yellow pigments, when the average particle diameter of the colorant is too small, it sometimes causes a problem in that the resulting toner has insufficient coloring property.
SUMMARY OF THE INVENTION
Therefore, the invention has been made to solve the problems associated with conventional toner to provide a toner for developing an electrostatic image, a process for producing the same, a developer for an electrostatic image and a process for forming an image.
The invention provides:
1. a toner for developing an electrostatic image excellent in fixing property and particularly in light transmissibility and coloring property to satisfy high image quality and high reliability, and a developer for an electrostatic image using the toner for developing an electrostatic image;
2. a process for producing a toner for developing an electrostatic image that can produce the toner for developing an electrostatic image having the excellent characteristics in a convenient and simple manner without isolation of a colorant and a releasing agent; and
3. a process for forming an image that can form a full color image of high color saturation on paper and an OHP sheet in a convenient manner.
According to an aspect of the invention, the toner for developing an electrostatic image contains at least a resin component and colorant particles, and the colorant particles exhibit a dispersion state inside the toner observed by a transmission electron microscope satisfying two conditions, where
(1) the colorant particles have a dispersion average particle diameter of 100 nm or less, and
(2) a content of coarse colorant particles of a diameter of 400 nm or more is 5% by number or less based on the total of the colorant particles.
According to another aspect of the invention, the process for preparing the toner for developing an electrostatic image includes an aggregation step of mixing at least one kind of resin particle dispersion, at least one kind of colorant dispersion, at least one kind of releasing agent dispersion, and an aggregating agent to form aggregated particles, and a fusing step of fusing the aggregated particles by heating to a temperature higher than a glass transition point of the resin particles to form toner particles.
The colorant dispersion used in the aggregation step preferably has a 50% particle diameter (volume basis) of colorant particles of 100 nm or less, and also preferably has a 84% particle diameter (volume basis) of colorant particles of 200 nm or less.
In the case of the one-component developer, the toner for developing an electrostatic image of the invention constitutes a developer for an electrostatic image only with the toner for developing an electrostatic image, and in the case of the two-component developer containing a carrier and a toner, the toner for developing an electrostatic image of the invention is used as the toner to constitute the developer for an electrostatic image.
According to still another aspect of the invention, the process for forming an image includes a latent image forming step of forming a latent image on a surface of an electrostatic latent image holding member, a developing step of developing the electrostatic latent image on the surface of the electrostatic latent image holding member by using a layer of a developer for an electrostatic image formed on a surface of a developer holding member to form a toner image, and a transferring step of transferring the toner image on the surface of the electrostatic latent image holding member to a surface of a transfer material. The developer for an electrostatic image contains the toner for developing an electrostatic image according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The invention will be described in detail below.
Toner for Developing Electrostatic Image
(a) Dispersion State of Colorant Particles
In the toner for developing an electrostatic image according to the invention, the dispersion state of the colorant particles inside the toner measured by a transmission electron microscope (TEM) necessarily satisfies the following conditions (1) and (2).
(1) The colorant particles have a dispersion average particle diameter of 100 nm or less.
The colorant particles necessarily have a dispersion average particle diameter of 100 nm or less, and preferably from 70 to 90 nm. When the dispersion average particle diameter of the colorant particles exce
Ishiyama Takao
Matsumura Yasuo
Sato Shuji
Serizawa Manabu
Shoji Takeshi
Fuji 'Xerox Co., Ltd.
Goodrow John
Oliff & Berridg,e PLC
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