Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1999-12-14
2001-02-27
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...
Reexamination Certificate
active
06194116
ABSTRACT:
This application is based on applications Hei 10-355794 and Hei 10-355798 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrostatic latent image-developing toner for forming a monochrome image or a full color image, and also concerns an image-forming method for forming images with such a toner.
2. Description of the Related Art
In the field of electrophotography, it is an effective method to miniaturize the toner particle size in order to obtain high image quality. However, the miniaturization of the toner particle size causes degradation in the cleaning properties and the electrification properties. Moreover, in order to improve the fluidity that deteriorates due to the miniaturization of the toner particle size, a little excessive fluidizing agent is added; however, an increased amount of the fluidizing agent also causes degradation in the cleaning properties and the electrification properties.
With respect to techniques proposed to improve the cleaning properties, for example, Japanese Patent Application (JPA) Laid-Open No. 76406/1996 disclosed that organic fine particles made of polyvinylidene fluoride are added to the toner surface, or JPA Laid-Open No. 160165/1995 discloses that zinc stearate is added to the toner surface.
U.S. Pat. No. 4,933,253, U.S. Pat. No. 4,943,505 and JPA Laid-Open No.186876/1985 have proposed techniques in which fine particles of methylmethacrylate or copolymer particles thereof with styrene are added to the toner surface as an cleaning-assist agent, or U.S. Pat. No. 4,187,329 has proposed a technique in which fine particles of a fluorine compound, typically Teflon, is added to the toner surface as a cleaning-assist agent.
Furthermore, for example, in a technique proposed by U.S. Pat. No. 4,883,736, alkyl alcohol with a long chain is added to the toner surface.
With respect to inorganic fine particles, for example, U.S. Pat. No. 5,759,731 has proposed a method in which a metal oxide such as strontium titanate is added to the toner surface as a polishing agent for a photosensitive member.
However, in the above-mentioned method for adding a metal salt of fatty acid such as zinc stearate to the toner surface, the cleaning properties improve, but an increased amount of addition to the toner raises a problem in which the electrification properties of toner deteriorates extremely.
With respect to metal oxides such as alkyl alcohol with a long chain and strontium titanate, the adverse effect is not as serious as the above-mentioned metal salt of fatty acid. The addition thereof to the toner surface, however, tends to cause degradation of the electrification properties of toner.
With respect to the fine particles of methylmethacrylate or a copolymer thereof with styrene or fine particles of a fluorine compound, the addition thereof to the toner surface gives a little improving effect to the cleaning properties. But, it gives little effect, in particular, to prevent black spots on the photosensitive member caused by toner components.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a toner in which the cleaning properties and the electrification properties are not degraded even when a toner particles size is made small in an attempt to meet the demand for high image quality.
Another object of the present invention is to provide a toner which can achieve high image quality, high reliability as well as high durability.
Still another object of the present invention is to provide a toner which has an excellent electrification build-up properties.
The other object of the present invention is to provide a toner which maintains excellent charging stability even when used for a long time.
These objects are achieved by adding organic fine particles that has a volume average particle size in the range of 0.1 to 20 &mgr;m and contains a specific alkyl carboxylic acid to the toner.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a toner comprising:
toner particles containing a binder resin and a colorant; and
organic fine particles admixed with the toner particles, the organic fine particles having a volume average particle size of 0.1 to 20 &mgr;m and containing alkyl carboxylic acid having a number average molecular weight of 300 to 1000.
The addition of the above-mentioned organic fine particles in accordance with the present invention makes it possible to provide a toner which is not susceptible to degradation in the cleaning properties and the electrification properties even when the toner particle size is miniaturized in an attempt to meet the demand for high image quality. High image quality can be achieved as well as high reliability and durability.
It is effective to use the toner of the present invention in a toner image-forming method in which an electrostatic latent image, which is developed but not transferred onto a sheet of recording paper, is formed between the formations of electrostatic latent images corresponding to the images when forming a plurality of desired images.
A carboxylic acid used in the present invention is mainly made of a saturated hydrocarbon carboxylic acid with a straight chain having a number average molecular weight (Mn) in the range of 300 to 1000, preferably 300 to 800, more preferably 350 to 750, and an acid value (mgKOH/g) in the range of 50 to 130, preferably 60 to 120. This compound may be represented by the average number of carbon atoms instead of the number average molecular weight. The average number of carbon atoms is in the range of C20 to C70, preferably C22 to C55, more preferably C24 to C50, still more preferably C24 to C48. Such an alkyl carboxylic acid is commercially available as Unicid™ carboxylic acid made by Toyo Petrolite Co., Ltd. Moreover, it is desirable to use alkyl carboxylic acid having a specific gravity (g/cc) of 0.70 to 0.80, preferably 0.75 to 0.79 in the present invention.
In the present invention, the alkyl carboxylic acid may be specified only by the average number of carbon atoms or only by the number average molecular weight instead of the average number of carbon atoms, preferably being specified by the average number of carbon atoms and the acid value or by the average molecular weight and the acid value. Of course, the alkyl carboxylic acid may be specified by all the physical properties including the average number of carbon atoms, the average molecular weight and the acid value. In the present invention, the object of the invention is sufficiently achieved by an alkyl carboxylic acid specified by the average number of carbon atoms and the acid value, or the average molecular weight and the acid value. Normally, an alkyl carboxylic acid specified by the average molecular weight and the acid value is used as it is easy to specify it.
When an alkyl carboxylic acid that does not satisfy the above-mentioned physical properties is used, the heat resistance of toner may deteriorate, the electrification build-up properties of toner may deteriorate, fog may occur, and the effect for preventing black spots may be reduced.
The present invention uses an average molecular weight obtained by a permeation pressure method and a specific gravity measured by an ASTMD 1705, and an acid value measured by a BWM3.10A.
The above-mentioned alkyl carboxylic acid is externally added to a toner in the form of fine particles having a volume average particle size in the range of 0.1 to 20 &mgr;m, preferably 1 to 10 &mgr;m, more preferably 4 to 8 &mgr;m. If the size is smaller than 0.1 &mgr;m, the adhesion strength of the alkyl carboxylic acid to the toner surface increases, with the result that the effect for preventing black spots (BS) is reduced, and the amount of adhesion of the alkyl carboxylic acid to the charge-giving member increases; thus, fog is more likely to occur as the number of printed sheets of paper increases due to inappropriate toner charging. If the particle size is greater than 20 &mgr;m, the surface of the photosensitive member
Arai Takeshi
Hagi Masayuki
Nishihara Yoshikazu
Tamaoki Junichi
Burns Doane , Swecker, Mathis LLP
Goodrow John
Minolta Co. , Ltd.
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