Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1996-06-05
1998-08-04
Mosley, Terressa
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
430 31, 524824, 525437, 526 78, 528279, 528283, 528296, 528297, C08G 6302
Patent
active
057895279
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a polyester resin for use in a toner binder which is appropriate as a toner for developing an electrostatic image that is used in the field of electrophotography, electrostatic recording, electostatic printing or the like, to a process for producing the same, and to a toner using the same.
BACKGROUND OF THE INVENTION
The conventional electrophotography comprises, as described in the specifications of U.S. Pat. Nos. 2,297,691 and 2,357,809, a step of forming an electrostatic latent image on the surface of a roller made of a photoconductive insulator and developing this latent image as a toner image using a dry developer formed of colored fine particles, a step of transferring the thus-obtained toner image onto a transfer sheet such as paper or the like, and a step of permanently fixing the transferred image through heating, pressuring or the like.
Recently, a higher speed, a smaller size and energy saving have been required in a copier. In order to meet these requirements, a fixing step is preferably conducted using a heating roller which has excellent thermal efficiency, which has a compact mechanism and which allows a higher speed operation.
However, since the surface of the heating roller is brought into contact with the surface of the toner image in this heating roller fixing method, a so-called offset phenomenon occurs in which the toner is transferred onto the surface of the heating roller and then onto a paper, causing a next paper to be stained with the toner image.
In order to prevent such an offset phenomenon, Japanese Patent Publication No. 23,354/1976 proposed that a crosslinking styrenic resin is used as a resin for use in a toner binder. Since then, various improvements have been conducted, and a styrene-acrylate ester copolymer has been mainly used as a resin for use in a toner binder.
Meanwhile, recently, it has been found that a polyester resin is superior to the conventional styrene-acrylate ester copolymer in that the former allows the fixing at a lower temperature, is excellent in terms of durability to vinylchloride plasticizers, and can be applied to coloring for its excellent transparency. Thus, the polyester resin has attracted attention as a resin for use in a toner binder.
Generally, a polyester resin is produced by a condensation reaction between a dicarboxylic acid and/or its lower alkyl ester and a dihydric alcohol. When the thus-obtained polyester resin consisting only of a linear component is used as a toner binder, the offset resistance is very poor, making it impossible to obtain a good transferred image.
Therefore, as a means for decreasing the offset phenomenon when a polyester resin is used as a toner binder, it was proposed in Japanese Laid-Open Unexamined Patent Application Nos. 75,043/1975, 86,342/1979 and 195,680/1987 that polyester resins having a three-dimensional network structure obtained by copolymerizing a tricarboxylic acid and/or a trihydric alcohol are used as toner binders.
However, when a tricarboxylic or polycarboxylic acid and/or a trihydric or polyhydric alcohol is copolymerized as mentioned above, a crosslinking reaction abruptly proceeds in the condensation reaction step for crosslinking. As a result, the reaction product undergoes gelation at times and cannot be discharged from the reaction vessel. Further, when the product has an excessively crosslinked structure, the flowability of the resin decreases, impairing the fixability at a low temperature which is an inherent property of polyester resins.
In order to solve this problem, first, Japanese Laid-Open Unexamined Patent Application No. 54,574/1991 discloses a method in which a reaction temperature and a degree of vacuum on reaction are controlled to suppress the abrupt gelation. However, it substantially involves problems in which the viscosity of the polymer excessively increases owing to the distillation of low-boiling components formed by the transesterification reaction, making it impossible to obtain a resin having a desired degree o
REFERENCES:
International Search Report dated Jul. 26, 1995 and mailed Aug. 15, 1995.
Kubota Tomoko
Kurebayashi Hideki
Nakadera Kazue
Nakamichi Kikumi
Okutani Haruo
Mosley Terressa
Tomoegawa Paper Co. Ltd.
Unitika Ltd.
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