Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1999-11-23
2001-07-24
Rodee, Christopher (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C428S405000, C428S407000
Reexamination Certificate
active
06265126
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a hydrophobic metal oxide powder suitably added to an electrophotographic developer in order to improve fluidity of a toner, control the charge thereof, etc., and an electrophotographic developer containing the same.
BACKGROUND ART
In electrophotography, the development process is carried out by adhering a toner to an electrostatic latent image on a photosensitive member. A general electrophotographic developer contains a toner and a carrier for imparting charge to the toner by frictional charging and carrying the toner to a development region. In general, the toner comprises a thermoplastic resin, a colorant, and a charge controller, and the carrier comprises a magnetic powder of iron, ferrite (iron oxide) or the like. It is known that besides the toner and carrier, various additives can be added to the developer for the purpose of controlling the charge of the toner, improving the fluidity and cleaning properties of the toner, etc.
For example, a hydrophobic metal oxide powder obtained by making hydrophobic the surfaces of a metal oxide powder of silica, alumina, titania or the like using an organic material is added as an agent for improving the fluidity and cleaning properties of the toner to an electrophotographic developer. Such a hydrophobic metal oxide powder is also known to be used as a charge controller. Therefore, hydrophobicity and frictional charge are important features for this type of hydrophobic metal oxide powder, and these features are controlled by the type and the coating amount of the organic materials used for surface treatment of a metal oxide powder.
In general surface treatment of a metal oxide powder, surface treatment of the powder with an amine organic compound is known to decrease the negative charge of the powder or impart positive charge to the powder. It is also proposed that the metal oxide powder surface-treated with such an amine organic compound is used as a charge controller for toner.
For example, Japanese Examined Patent Publication No. 53-22447 proposes that a metal oxide powder surface-treated with aminosilane (an amino-containing silane coupling agent) is used as a positive charge controller for toner. In addition, Japanese Unexamined Patent Publication No. 62-52561 discloses an electrophotographic toner containing as a positive charge controller a powder obtained by treating vapor phase silica with epoxy-containing silane and then with an amine. In general, a metal oxide powder surface-treated with such silane cannot be sufficiently increased in hydrophobicity, and does not have the sufficient effect of improving the fluidity and cleaning properties of the toner.
Japanese Unexamined Patent Publication Nos. 6-80406 and 6-83099 disclose that organopolysiloxane containing epoxy groups and a metal oxide powder surface-treated with polyalkyleneimine are added to an electrophotographic developer for the purpose of both improving fluidity and controlling charge. However, it was found that since the polyalkyleneimine (for example, polyethyleneimine) used as an amine is a polymeric amine containing many amino groups per molecular weight and having a high molecular weight, and the surface of the powder is covered with polyalkyleneimine chains with relatively high hydrophilicity, hydrophobicity and fluidity become insufficient.
Japanese Unexamined Patent Publication No. 63-155155 discloses an electrostatic image developer containing inorganic fine particles which are treated with silicone oil containing epoxy groups and then with an amino compound. However, the inorganic particles treated in two steps as described above have unreliable charge controllability and/or insufficient hydrophobicity.
An object of the present invention is to provide a hydrophobic metal oxide powder which can be controlled in frictional charge within a wide range by using a relatively small amount of coating, and which is provided with high hydrophobicity and fluidity, and also an electrophotographic developer containing the hydrophobic metal oxide powder.
DISCLOSURE OF THE INVENTION
The above object can be achieved by simultaneously surface-treating a metal oxide powder with silicone oil containing epoxy groups and an amine compound having active hydrogen, or surface-treating a metal oxide powder with silicone oil containing epoxy groups and amino groups and previously obtained by reaction. When hydrophobicity is desired to be further improved, straight silicone oil may be further used with above components.
In according to the present invention, there are provided the following:
(1) A hydrophobic metal oxide powder having surface coating and formed by simultaneous surface treatment with silicone oil containing epoxy groups and a non-polymeric amine compound having a lower number of primary and/or secondary amino groups than the total number of the epoxy groups; and
(2) A hydrophobic metal oxide powder having surface coating and formed by surface treatment with silicone oil containing epoxy groups and amino groups.
In the surface treatments for the hydrophobic metal oxide powders (1) and (2), straight silicone oil may be further used with the above components.
For the hydrophobic metal oxide powder (2), silicone oil having epoxy groups and amino groups can be prepared by reacting silicone oil having epoxy groups with a non-polymeric amine compound having a lower number of primary and/or secondary amino groups than the necessary number for reaction with all epoxy groups.
The hydrophobic metal oxide powder of the present invention preferably exhibits a degree of hydrophobicity of 60% or more which is measured by a transmittance method.
In accordance with the present invention, there is provided an electrophotographic developer containing the hydrophobic metal oxide powder.
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the type of the metal oxide powder subjected to surface coating is not limited, and any metal oxide powder can be selected according to application. Preferable metal oxide for improving fluidity of toner include silica, alumina and titania (titanium oxide), but other metal oxides such as zirconia (zirconium oxide), zinc oxide, tin oxide, and the like can also be used according to application.
The particle size of the metal oxide powder may also be selected according to application. A powder having a specific surface area of 50 m
2
/g or more is preferably used for improving fluidity of toner.
The metal oxide may be a composite oxide comprising at least two metals, or a mixture of at least two metal oxides.
The metal oxide powder is preferably synthesized by a vapor phase method. The metal oxide powder synthesized by the vapor phase method has less aggregation of particles, and is thus suitable for improving the fluidity of toner. The metal oxide powder is synthesized by the vapor phase method, for example, the known method of decomposing a metal chloride such as silicon tetrachloride or the like, and industrial synthetic products are commercially available.
In accordance with the present invention, coating is formed on the surfaces of the metal oxide powder by surface treatment with (1) silicone oil having epoxy groups (referred to as “epoxy-modified silicone oil” hereinafter) and an amine compound (=an amine compound having active hydrogen) having a lower number of primary and/or secondary amino groups than the total number of the epoxy groups, (2) silicone oil (referred to as “epoxy/amino-modified silicone oil” hereinafter) having epoxy groups and amino groups, or (3) straight silicone oil in addition to (1) and (2).
Epoxy groups have the function to strongly combine silicone oil with the metal oxide powder, and modified silicone oil imparts hydrophobicity to the metal oxide powder. When the effect of imparting hydrophobicity is insufficient, the effect of imparting hydrophobicity can be increased by using straight silicone oil with modified silicone oil. Amino groups change the charge of the metal oxide powder to positive, and the charge applied to the powder greatly depends u
Nishihara Akira
Sakurai Hideaki
Yamashita Yukiya
Mitsubishi Materials Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Rodee Christopher
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