Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1996-01-26
2001-12-18
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...
C430S106100, C430S111400
Reexamination Certificate
active
06331373
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a developer for electrostatic images. More particularly, this invention relates to an electrostatic image developer which exhibits properties such as charge stability and fluidity at improved levels.
2. Prior Art
The electrophotography produces a visible image by forming an electrostatic image on the surface of a photoconductive element and exposing the surface bearing the electrostatic image to a developer which contains a toner charged to a polarity opposite to that of the image thereby inducing deposition of the toner on the image. The visible toner image consequently obtained, when necessary, may be transferred to a transfer paper and fixed thereon to obtain a copy.
The charging of the toner which is used for developing such electrostatic image is fulfilled in the two-component developing method by mixing and diffusing the toner with a substance generally called a carrier thereby imparting an electric charge to the toner, or in the one-component developing method by causing the toner to contact a developing sleeve or a toner regulating plate thereby imparting an electric charge to the toner. In any event, the steps of development and transfer of the image pose various problems unless the electric charge is imparted uniformly and stably to the toner. For example, the inferiority of developed image due to the lack of the developer soavenging effect and the developing electrode effect and the liability of the sensitizing surface to gather smear due to insufficient transfer of developed image are counted among the problems.
For the purpose of solving these problems, JP-A-52-135,739 proposes an electrostatic image developing toner which has as a component thereof a metal oxide or silicone dioxide powder treated with amino silane. Since this toner is capable of maintaining a positive charge property, it is enabled to exhibit its developing property and transferring property at improved levels. When the metal oxide powder or silicon dioxide powder is blended with the binding resin of the toner and the coloring agent such as carbon black, however, it inevitably poses problems such as consuming much time for dispersion and suffering ready agglomeration of the produced toner particles. For the purpose of improving the fluidity of toner and enhancing the stability of charging, the practice of adding hydrophobic colloidal silica to toner particles has been introduced to the art and put to use (as disclosed in JP-B-63-36,499, for example). The addition of such colloidal silica indeed results in improving the fluidity of toner. It nevertheless consumes much time for dispersion of components being mixed during the manufacture of toner as in the former case and fails to enhance the charging property of toner to a fully satisfactory extent. Specifically, it entails the problem that unduly heavy fogging and unduly low image density ensue when the total number of produced copies exceeds 10,000 to 20,000. This particular problem gains in consipicuity with rising temperature and moisture of the ambience.
JP-A-63-101,854 discloses a toner containing a polymethylsilsesquioxane powder possessing a negative charge property and JP-A-63-101,855 a toner containing a polymethylsilsesquioxane powder endowed with a positive charge property by a surface treatment with an amino group-containing silane compound. Though these toners enjoy fully satisfactory charge properties, they have the problem that they suffer loss of fluidity, tend to smear the sensitizing surface, and exhibit a poor transferring property because the polymethylsilsesquioxane has unduly low mechanical strength.
SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to provide a novel electrostatic image developer. Another object of this invention is to provide an electrostatic image developer which is improved in various properties such as fluidity, charging property, and transferring property.
To accomplish the objects described above, this invention provides an electrostatic image developer, which comprises:
toner particles containing (a) a binding resin and (b) a coloring agent and having a mean particle diameter of not more than 25 &mgr;m; and
(c) organic-inorganic composite particles attached or fixed to the surface or to the proximity of surface of the toner particles, containing an organic polymer framework and a polysiloxane framework, wherein the polysiloxane framework has in the molecule thereof an organosilicon which has a silicon atom to which at least one carbon atom in the organic polymer framework combined directly, the (c) organic-inorganic composite particles having SiO
2
as a component of polysiloxane framework at a content in the range of 10 to 90% by weight, and the composite particles having a mean particle diameter in the range of 0.01 to 5 &mgr;m;
the mixing ratio of (b) the coloring agent to (a) the binding resin in the toner particles being 20 to 2 parts by weight of (b) the coloring agent to 80 to 98 parts by weight of (a) the binding resin, when the total amount of (a) and (b) is 100 parts; and
the mixing ratio of the organic-inorganic composite particles to the toner particles being 0.01 to 20 parts by weight of the organic-inorganic composite particles to 100 parts by weight of the toner particles.
In the electrostatic image developer of this invention, it is preferable that the (c) the organic-inorganic composite particles have the SiO
2
which constitutes the polysiloxane framework at a content in the range of 25 to 85% by weight.
In the electrostatic image developer of this invention, (c) the organic-inorganic composite particles appropriately have a mean particle diameter in the range of 0.01 to 2 &mgr;m.
In the electrostatic image developer of this invention, it is preferable that the mixing ratio of (c) the organic-inorganic composite particles to 100 parts by weight of the toner particles appropriately is in the range of 0.1 to 3 parts by weight.
This invention further provides an electrostatic image developer, wherein (c) the organic-inorganic composite particles are obtained by a step of hydrolyzing and condensing at least one radically polymerizable group-containing, hydrolyzable and condensable silicon compound selected from the group consisting of compounds represented by the following general formula (I):
R
m
1
SiX
4-m
(I)
(wherein R
1
stands for a radically polymerizable organic group having C
2
~C
20
, X for a C
1
~C
5
alkoxy group or an acyloxy group, and m for an integer in the range of 1 to 3, providing that where m is 2 or more, at least one of the plurality of substituents R
1
's may be a radically polymerizable organic group having C
2
~C
20
and the remainder may be an organic group containing no radically polymerizing group) and derivatives thereof, and a step of subjecting the radically polymerizable groups to a reaction of radical polymerization.
In this invention, it is preferable that the substituent R
1
in the general formula (I) mentioned above is at least one group selected from the class consisting of:
CH
2
═CH—
(wherein R
2
stands for a hydrogen atom or a methyl group and R
3
for a C
1
~C
10
alkylene group)
(wherein R
4
stands for a hydrogen atom or a methyl group and R
5
for a phenylene group or a C
1
~C
10
alkylene group).
This invention further provides an electrostatic image developer, wherein (c) the organic-inorganic composite particles are obtained by a step of partially or wholly hydrolyzing in the presence of an acid at least one hydrolyzable and condensable silicon compound selected from the group consisting of compounds represented by the following general formula (I):
R
m
1
SiX
4-m
(I)
(wherein R
1
stands for a radically polymerizable organic group having C
2
~C
20
, X for a C
1
~C
5
alkoxy group or an acyloxy group, and m for an integer in the range of 1 to 3, providing that where m is 2 or more, at least one of the plurality of substituents R
1
's may be a radically polymerizable organic group having C
2
~C
20
a
Ando Nobuyuki
Ikeda Hayato
Kuramoto Shigefumi
Sakai Yasuhiro
Goodrow John
Nippon Shokubai Co. , Ltd.
Selitto Behr & Kim
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