Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-05-15
2004-05-11
Goodrow, John L (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S110300, C430S111400, C430S124300
Reexamination Certificate
active
06733941
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin composition for toners used for electrophotographs and the like, and a toner.
BACKGROUND ART
Electrophotography in copiers and printers generally uses a process that includes electrostatically forming a latent image on a photosensitive material, developing the latent image by use of a toner, transferring the toner image on a sheet to be fixed, such as a piece of paper, and subsequently pressure fixing the image by a heat roller (the heat roller-fixing process). This heat roller fixing process requires a toner with good fixation properties, which permits fixation at lower temperature, for the improvement of cost efficiency in power consumption and the like, the increase of copying speed, and the prevention of curling of a sheet and the like. In addition, needs for a high quality image and high resolution of a copy image have recently been growing as a result of the development of computers, high resolution TV's, or the like.
In response to such demands, the proposals of the prior art include a product in which the molecular weight and molecular weight distribution of the binder resin are improved. The fixing temperature can be lowered by making low the molecular weight of the binder resin to thereby decrease the melt viscosity thereof. However, lowering the molecular weight decreases the melt viscosity, which simultaneously decreases the cohesive strength of the resin, leading to the problem of causing a toner offset to the fixing roll.
In order to prevent such a problem, a material of a wide molecular distribution, made by mixing a resin of a high molecular weight and a resin of a low molecular weight, is utilized as the binder resin and further the high molecular weight portion of a binder resin is made cross-linked. However, this method increases the viscosity of the resin and thus, on the contrary, makes it difficult to satisfy the fixation properties.
In addition, in order to acquire sufficient fixation properties, a method of decreasing the glass transition temperature of the resin is known; however, in this case, loss of preserving properties of the toner is unavoidable.
Further, in order to impart offset resistance, a method is known in which a polypropylene wax is made contained as a releasing agent. However, the melting point of polypropylene is generally as slightly high as from 130 to 150° C., which causes the problem of not showing its effect at a low fixing temperature.
Furthermore, a method in which a Fischer-Tropsch wax or a microcrystalline wax is made contained as a releasing agent is known in U.S. Pat. Nos. 5,629,122, 5,547,799, 5,702,859 and 5,780,197, etc. These waxes have melting points lower than that of a polypropylene wax, and so they are thought to show releasing agent effects even at lower temperatures. However, even these methods are not sufficient in hot offset properties and thus improvement is required.
So far, a variety of methods were attempted; however, a method in which particularly the aforementioned problems are solved has not provided yet.
DISCLOSURE OF THE INVENTION
The present invention can solve the aforementioned problems of the conventional toners and its object is to provide a resin composition for toners and a toner, excellent in low temperature fixation, offset resistance and preserving properties.
The inventors carried out investigations in order to solve the aforementioned problems; as a result, they have made the inventions described below.
[1] A resin composition for toners comprising:
(A) a wax composition comprising an ethylene polymer having a melt index value of from 0.1 to 100 as measured at 190±0.4° C. and a paraffin wax having a melting point of from 70° C. to 120° C. or a Fisher-Tropsch wax having a melting point of from 70° C. to 120° C.; and
(B) a binder resin for toners.
[2] The resin composition for toners according to [1], in which
with respect to a whole resin composition for toners, a content of the (A) component is from 0.05% by weight to 15.0% by weight, and a content of the (B) component is from 85.0% by weight to 99.95% by weight; and
with respect to a whole (A) component, a content of the ethylene polymer is from 0.01% by weight to 5.0% by weight, and a total content of the paraffin wax and the Fisher-Tropsch wax is from 95.0% by weight to 99.99% by weight.
[3] The resin composition for toners according to [1] or [2], in which
the aforementioned binder resin for toners is a styrene polymer (copolymer).
[4] The resin composition for toners according to [3], in which
the aforementioned styrene polymer (copolymer) contains a constituent derived from a styrene monomer and a constituent derived from a (meth)acrylate monomer or a (meth)acrylic acid monomer;
the styrene polymer (copolymer) has a glass transition temperature Tg of from 45° C. to 75° C.; and
in a chromatogram as measured by GPC, the styrene polymer (copolymer) has an weight-average molecular weight (Mw) of 100,000 or higher, has at least one maximum value or one shoulder in both a molecular weight range of from 3,000 to 12,000 and a molecular weight range of 100,000 or higher, and has a ratio (Mw/Mn) of Mw to number average molecular weight (Mn) of from 15 to 100.
[5] The resin composition for toners according to [1] or [2], in which
the aforementioned binder resin for toners is a polyester copolymer.
[6] The resin composition for toners according to [5], in which
the aforementioned polyester copolymer has a glass transition temperature Tg of from 45° C. to 75° C.; and
in a chromatogram as measured by GPC, the polyester copolymer has an Mw of from 6,000 to 150,000, has at least one maximum valve or one shoulder in the molecular weight range of from 3,000 to 12,000, and has an Mw/Mn of 5 or more.
[7] The resin composition for toners according to any of [1] to [6], in which
the resin composition for toners further includes a polyolefin wax.
[8] A toner comprising the resin composition for toners according to any [1] to [7].
The wax composition of the present invention is a mixture containing an ethylene polymer composed of an ethylene monomer as a primary constituent and a paraffin wax or a Fisher-Tropsch wax and preferably further containing a polyethylene wax.
Inclusion of an ethylene polymer composed of an ethylene monomer as the primary constituent in the wax composition allows good dispersion of a paraffin wax or a Fisher-Tropsch wax into the binder resin. This permits the appearance of good fixation and good offset performance. Inclusion of a polyethylene wax is more preferable for better wax dispersion.
A resin composition for toners and a toner of the present invention are made composed as described above and are excellent in offset resistance, fixation and preserving properties.
As a consequence, a resin composition for toners and a toner of the present invention can sufficiently meet recent increasing demands such as speedup of copying, energy conservation and high image quality.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described in detail.
(Wax)
A paraffin wax of the present invention refers to a mixture of hydrocarbons whose main component is normal paraffin, a mixture that is extracted, separated and highly refined by operation including reduced-pressure distillation of petroleum.
A Fisher-Tropsch wax of the present invention refers to a synthesized wax composed mainly of linear hydrocarbons, which are obtained by, for example, causing water gas, of which main components are carbon monoxide and hydrogen, to react using a catalyst such as cobalt, nickel or an iron-based material at normal pressure at 170 to 250° C. This Fisher-Tropsch wax can be synthesized by means of the Fisher-Tropsch process for utilization or a commercially available one can be utilized.
In the present invention, the melting points of both the paraffin wax and the Fisher-Tropsch wax ra
Takei Hiroyuki
Terauchi Tomoya
Uchiyama Kenji
Yamamoto Takashi
Burns Doane , Swecker, Mathis LLP
Goodrow John L
Mitsui Chemicals Inc.
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