Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-12-13
2002-12-03
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108100, C430S109300, C430S108800
Reexamination Certificate
active
06489074
ABSTRACT:
TECHNICAL FIELD
This invention relates to a toner resin composition and a toner for use in the electrophotography and the like, and more particularly to a toner resin composition for use in a dry electrostatic image development process and a toner made therefrom.
BACKGROUND ART
In the field of electrophotography and the like, a dry development process has been widely employed for developing electrostatic images. In this dry development process, triboelectrically chargeable toners and magnetic toners are utilized. The former is prepared by mixing fine particles containing toner resin particles serving as a binder and a coloring material, such as carbon black or the like, with carrier particles such as iron powder or glass beads. The latter is prepared by incorporating a coloring material, such as carbon black or the like, and a magnetic powder, such as magnetite or the like, in toner resins.
A so-called, hot press roll fixation process has come into widespread use in obtaining copies. According to this process, development is generally accomplished by allowing triboelectrically chargeable or magnetic toners to adhere electrically to electrostatic latent images formed on a photoreceptor. The resulting toner images are transferred onto a sheet, such as a paper, and then fixed thereon by toner-releasable hot press rolls.
For future high-speed operation or size reduction of copiers utilizing the hot press roll fixation process, a need has arisen for a toner which can be fixed at a lower temperature. From a point of low temperature fixability, the use of lower molecular-weight toner resins is effective in lowering a fixing temperature to some degree. However, the results have been limited and still insufficient.
Specifically, the toner incorporating a low-molecular-weight toner resin presents the following problems: it tends to accompany a phenomenon (offset) whereby a part of the toner that has failed to form images during fixation is transferred onto hot press roll surfaces and retransferred therefrom onto a coming paper or sheet to result in blurring images; its incorporation of lower molecular weight resins not only reduces the fixing strength of such a toner onto a sheet as of paper, but also increases a tendency for the formed images to be destructed, for example, when rubbed.
In order to solve such problems, Japanese Patent Laying-Open No. Hei 4-226473 has proposed the use of a specific resin composition to provide a toner which exhibits excellent fixability, offset resistance and image quality. The resin composition is prepared by thermally desolvating a resin solution containing a styrene resin such as styrene-(meth)acrylate copolymer, a low-molecular weight wax such as low-molecular weight polypropylene, and a styrenic block copolymer such as styrene-butadiene-styrene block copolymer.
The toner incorporating the resin composition as proposed by the above-identified reference shows improved low-temperature fixability, offset resistance and fixing strength. However, such toner performances are desired to be further increased to sufficiently higher levels that meet future demands of high-speed operation or size reduction.
DISCLOSURE OF THE INVENTION
The present invention provides a toner resin composition which, when incorporated in a toner, imparts thereto improved low-temperature fixability, offset resistance, storage stability and fixing strength with respect to a sheet as of paper. The present invention also provides a toner incorporating the toner resin composition.
In accordance with a broad aspect of this invention, a toner resin composition is provided which is characterized in that the composition contains a vinyl copolymer prepared principally from a styrene monomer and a (meth)acrylic ester monomer, 2-10% by weight of Fischer-Tropsch wax and 0.5-5% by weight of styrenic block copolymer, and that the vinyl copolymer, when its molecular weight distribution is determined by gel permeation chromatography, shows maximum peaks at least in the molecular weight range of 5,000-20,000 and in the molecular weight range of not below 500,000.
In accordance with another broad aspect of this invention, a toner is provided which is characterized in that the toner contains a coloring material and a toner resin composition comprised of a vinyl copolymer prepared principally from a styrene monomer and a (meth)acrylic ester monomer, 2-10% by weight of Fischer-Tropsch wax and 0.5-5% by weight of styrenic block copolymer, and that the vinyl copolymer, when its molecular weight distribution is determined by gel permeation chromatography, shows maximum peaks at least in the molecular weight range of 5,000-20,000 and in the molecular weight range of not below 500,000.
In the present invention, a primary contributor of good low-temperature fixability and offset resistance is the vinyl copolymer prepared principally from a styrene monomer and a (meth)acrylic ester monomer and having maximum peaks at least in the molecular weight range of 5,000-20,000 and in the molecular weight range of not below 500,000.
The Fischer-Tropsch wax, when included in the amount of 2-10% by weight, plays a principal roll of preventing a toner from depositing on hot press roll surfaces and thereby preventing the occurrence of offset at a lower temperature range. Further incorporation of the styrenic block copolymer in the amount of 0.5-5% by weight plays a principal roll of increasing a melt viscosity, leading to the improved offset resistance and fixing strength. While a reason is not clear, the presence of such a styrenic block copolymer also renders the Fischer-Tropsch wax more dispersible than conventional low-molecular weight waxes, such as low-molecular weight polypropylene, thereby enabling its uniform dispersion.
From viewpoints of low-temperature fixability and offset resistance, the present invention utilizes the vinyl copolymer prepared principally from a styrene monomer and a (meth)acrylic ester monomer and showing maximum peaks at least in the molecular weight range of 5,000-20,000 and in the molecular weight range of not below 500,000 when its molecular weight distribution is determined by gel permeation chromatography (GPC).
Examples of styrene monomers used to constitute the above-specified vinyl copolymer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, &agr;-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-ter-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene and the like.
Examples of (meth)acrylic ester monomers used to constitute the above-specified vinyl copolymer include alkyl esters of acrylic and methacrylic acids, such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, stearyl methacrylate and the like.
Particularly suitable are ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate and butyl methacrylate.
Other useful (meth)acrylic ester monomers include 2-chloroethyl acrylate, phenyl acrylate, &agr;-chloromethyl acrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, bisglycidyl methacrylate, polyethylene glycol monomethacrylate, methacryloxyethyl phosphate and the like.
The following substances can be used in combination with the above-listed styrene monomer and (meth)acrylic ester monomer: unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, citraconic acid, itaconic acid; and crosslinking monomers such as monoacryloyloxyehtyl succinate, monomethacryloyloxyethyl succinate, acrylonitrile, methacrylonitrile, acrylamide, divinyl benzene, ethylene glycol diacrylate, trimethylolpropane triacrylate, triallyl isocyanurate.
Preferably, the viny
Shinjo Takashi
Takehara Hiroaki
Rodee Christopher
Sekisui Chemical Co. Ltd.
Townsend & Banta
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