Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-08-01
2002-01-01
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...
C430S125320
Reexamination Certificate
active
06335134
ABSTRACT:
This application is based on an application No. 219834/1999 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 a toner for an electrostatic latent image development which may be used in an electrophotography, an electrostatic printing and the like.
2. Description of the Related Art
In the fields of the electrophotography and electrostatic printing, there are problems that inorganic fine particles which are added to toner particles are adhered to a photosensitive member, and black spot (BS) which brings about image defects is occurred in a process of a blade cleaning.
For example, the following prior arts have heretofore been proposed in order to solve these problems.
U.S. Pat. No. 4,883,736 teaches that toner spots can be suppressed by adding internally or externally a higher alcohol whose carbon atom numbers are 30-300, preferably 30-50. Japanese Patent Publication (KOKAI) No. 282096/1994 discloses that it is possible to suppress a comet or a filming of fine powders onto the photosensitive member in the blade cleaning by employing a higher alcohol in the case where an external additive is used within a specified range.
In Japanese Patent Publication No. 72798/1993, a technical idea is exemplified wherein a carboxylic acid having a lower alkyl chain is added to toner particles as a solid lubricant in order to solve the aforementioned problems. However, in fact the technical idea has a problem that a heat resistance of the toner to which the carboxylic acid is externally added becomes worse, and the toner is not fit for a practical use unless the carboxylic acid is converted to a metallic salt in order to increase a melting point of the acid.
According to the aforementioned prior arts, the functions to suppress noises on the photosensitive member may be explained by a technical idea wherein the higher alcohol or higher fatty acid forms a lubricative film on the photosensitive member at the time of cleaning, and the lubricative film suppress the adhesion and filming of the toner components onto the photosensitive member. With respect to the electrophotographic process having the blade cleaning process, it has publicly been known that the adhesion and filming (black spot (BS)) of the inorganic fine powders and other components of the toner can be suppressed by externally adding the higher alcohol or higher fatty acid.
However, as described in any of the aforementioned publications, it has been indicated that there is a problem that a maintenance of heat resistance of the toner cannot be ensured unless carbon atom numbers of the higher alcohol or higher fatty acid employed in these prior arts are 30 and more from the viewpoint of the relationship between the carbon atom numbers and a starting point of a melting of said higher alcohol or higher fatty acid. According to a follow-up test by the inventors of the present application to confirm the effect of the higher alcohol described in the aforesaid publications, it has been confirmed that (i) a large quantity of the higher alcohol is necessary to suppress BS, (ii) an effect of forming the lubricative film is insufficient, and (iii) problems, such as a poor electrification of the toner, a decrease of an environmental stability and the like are newly occurred when a large amount of the higher alcohol is added to the toner particles.
In consideration of the functions of the aforementioned higher alcohol or higher fatty acid, although there is a reason to expect that the higher alcohol or higher fatty acid having lower molecular weight may bring about a higher effect from the viewpoint of the suppression of the adhesion and filming onto the photosensitive member, they cause a lethal problem that the heat resistance of the toner becomes worse. The prior arts could not cope with the problem.
SUMMARY OF THE INVENTION
The present invention provides a toner composition which suppresses an occurrence of BS (black spot) which brings about image defects in the process of a blade cleaning, said black spots being caused by an adhesion of inorganic fine particles which are added to the toner particles to the photosensitive member.
The present invention relates to a toner for an electrostatic latent image development which comprises the following aliphatic higher alcohols (1) or higher fatty acid (2) as an external additive:
H&Parenopenst;CH
2
&Parenclosest;
n
OH (n: an integer) (1)
H&Parenopenst;CH
2
&Parenclosest;
m
COOH (m: an integer) (2)
wherein number-average carbon atom numbers of the aliphatic higher alcohol or the higher fatty acid are 21-29, contents of the ingredients having carbon atom numbers of not more than 20 are not more than 2% by weight, and contents of the ingredients having carbon atom numbers of not less than 30 are not more than 2% by weight.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the investigating course to achieve the present invention, it has been proven that the higher alcohols or the higher fatty acids which have formerly been on the market as a general-purpose product contain large amounts of hydrocarbons having no hydroxyl group or carboxyl group, and that the commercially available products having carbon atom numbers of not less than 30 actually contain not less than 3% by weight of the ingredients whose carbon atom numbers are not more than 20.
The high-purity higher alcohols (e.g., Uniline Alcohol™ (Petroright Co.) and the like) or higher fatty acids (e.g., Unisit™ (Petroright Co.) and the like) which are produced by a different process from a general preparation process have been on the market, and said high-purity products are actually employed in the examples of the aforementioned prior arts. However, as regards these higher alcohols and higher fatty acids, it becomes clear that although contents of the hydrocarbons become little, a molecular weight distribution is broad and few percents of the ingredients whose carbon atom numbers are not more than 20. According to the results of actual differential thermal analyses of these commercially available higher alcohols and higher fatty acids by means of a differential scanning calorimeter (DSC), it has been confirmed that the higher alcohols or fatty acids whose carbon atom numbers are not less than 30 begin to slightly exhibit an endothermic process from around 50° C. Therefore it could have easily been predicted that these higher alcohols or fatty acids exert bad influence on the heat resistance of the toner in the case where large amounts of these compounds are added to the toner.
The present inventors have purified the general-purpose aliphatic higher alcohols or higher fatty acids which are on the market in such a way that a purity of single molecular weight of these compounds whose carbon atom numbers are 15-40 becomes not less than 98%, and prepared plural standard samples according to a molecular difference of said purified compounds. A starting temperature of a melting of the single standard sample or homogeneous mixtures thereof was measured by means of DSC. According to the results of these measurements, it could have been confirmed that the starting temperature of the melting (starting temperature of the endothermic process) becomes not less than 55° C. provided that a distribution of molecules whose carbon atom numbers are not more than 20 is not more than 2% by weight even if average carbon atom numbers of the higher alcohols or higher fatty acids are not more than 29. From a viewpoint of a maintenance of the heat resistance, the desirable starting temperature of the melting is not less than 55° C. If said temperature becomes less than 50° C., said maintenance becomes worse, and the higher alcohols or the higher fatty acids could not be used. On the other hand, it has been proven that it is necessary to add large amounts of the high-purity higher alcohols or higher fatty acids having carbon atoms of not less than 30 in order to suppress BS, said higher alcohols or higher fatty acids being regarded as a suit
Aoki Megumi
Arai Takeshi
Hagi Masayuki
Kido Kenichi
Mikuriya Yoshihiro
Goodrow John
Minolta Co. , Ltd.
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