Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-02-09
2002-05-07
Dote, Janis L. (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108800, C430S111400
Reexamination Certificate
active
06383705
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for electrophotography used for developing electrostatic latent images formed in electrophotography, electrostatic recording method, electrostatic printing, and the like.
2. Discussion of the Related Art
In the heat roller fixing method widely employed as a fixing method for a toner image, the method is excellent in that fixed images having excellent fastness can be obtained at a faster speed, as compared to other fixing methods, and that energy efficiency is high and little harm is caused to the environment by evaporation of a solvent or the like. However, there arises a defect that the offset phenomenon tends to be generated since the toner image is in direct contact with a fixing roller or belt.
On the other hand, from the viewpoint of energy-saving, there have been desired that a waiting time until which the temperature of the fixing device reaches an operable temperature is shortened, and that a toner is fixed at a lower temperature. Therefore, various methods have been tried, including a method of lowering a glass transition point of a resin binder or the like, a method of increasing low-molecular weight components, or a method using a plasticizer or the like. However, there arises a so-called “blocking,” wherein the toner is aggregated and solidified during storage or in the developer device.
Therefore, as a method for lowering a fixing temperature, there has been known a toner comprising a crystalline polyester as a resin binder. For instance, Japanese Examined Patent Publication No. Sho 62-39428 discloses a toner comprising a resin binder comprising, a crystalline polyester made from an aromatic polycarboxylic acid component as an acid component, the aromatic polycarboxylic acid component being contained in an amount of 50% by mol or more, and an amorphous polyester made from an aromatic polycarboxylic acid component as an acid component, the aromatic polycarboxylic acid component being contained in an amount of 60% by mol or more. However, when the basic structure of the both polyesters is the same, these resins undesirably become compatible to each other when kneaded during the toner preparation, so that the glass transition point of the crystalline polyester cannot be maintained. In addition, Japanese Examined Patent Publication No. Hei 5-44032 discloses a toner comprising a crystalline polyester having a softening point of from 50° to 100° C., and a crystalline polyester having a high softening point. However, when the basic structure of the both polyesters is the same, the softening point of the polyester at a lower melting point side has mal-affects to pulverizability and storage stability for the same reasons as above.
An object of the present invention is to provide a toner for electrophotography which is excellent all of the low-temperature fixing ability, the offset resistance, the blocking resistance, and the pulverizability, and capable of maintaining a high level of triboelectric charges for a long period of time, without causing contamination of the photoconductor.
These and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a toner for electrophotography comprising a resin binder comprising as its main components:
(a) a crystalline polyester having a softening point of from 85° to 150° C., obtainable by polycondensing an alcohol component which comprises 80% by mol or more of an aliphatic diol having 2 to 6 carbon atoms and a carboxylic acid component which comprises 80% by mol or more of fumaric acid; and
(b) an amorphous polyester and/or an amorphous polyester-polyamide, obtainable by polycondensing monomers comprising 50% by weight or more of an aromatic compound,
wherein a weight ratio of the crystalline polyester to the amorphous polyester and/or the amorphous polyester-polyamide, i.e. crystalline polyester/(amorphous polyester and/or amorphous polyester-polyamide), is from 1/99 to 50/50.
DETAILED DESCRIPTION OF THE INVENTION
The toner for electrophotography of the present invention comprises a resin binder comprising a crystalline polyester (Resin A) and an amorphous polyester and/or an amorphous polyester-polyamide (Resin B) as its main components. A total amount of the crystalline polyester and the amorphous polyester and/or the amorphous polyester-polyamide in the resin binder is preferably from 50 to 100% by weight, more preferably from 80 to 100% by weight, especially preferably 100% by weight.
The crystalline polyester used as Resin A is obtained by using monomers containing an alcohol component comprising a dihydric or higher polyhydric alcohol, and a carboxylic acid component comprising a dicarboxylic or higher polycarboxylic acid, an acid anhydride thereof, or an ester thereof. From the viewpoints of the softening point and the crystallinity of the resin, there can be used an aliphatic diol having 2 to 6 carbon atoms in an amount of 80% by mol or more, preferably from 90 to 100% by mol in the alcohol component, and fumaric acid in an amount of 80% by mol or more, preferably from 85 to 100% by mol in the carboxylic acid component. The aliphatic diol having 2 to 6 carbon atoms includes 1,4-butanediol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, and the like. Among them, &agr;,&ohgr;-linear alkylene glycols are preferable, and 1,4-butanediol are more preferable.
The dihydric alcohol which may be used other than the aliphatic diol having 2 to 6 carbon atoms includes diethylene glycol, triethylene glycol, 1,8-octanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hydrogenated bisphenol A, and the like. Among them, aliphatic diols having 7 to 20 carbon atoms, condensates thereof and condensates of the aliphatic diol having 2 to 6 carbon atoms are preferable.
The trihydric or higher polyhydric alcohol includes sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, and the like. Among them, from the viewpoints of the softening point and the crystallinity of the resin, glycerol is preferable.
In addition, preferred dicarboxylic acids, acid anhydrides thereof, or esters thereof other than fumaric acid are maleic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or a substituted succinic acid of which substituent is an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, such as dodecenylsuccinic acid and octylsuccinic acid; and derivatives thereof such as acid anhydrides thereof and alkyl(1 to 3 carbon atoms) esters thereof.
The tricarboxylic or higher polycarboxylic acid, an acid anhydride thereof, or an ester thereof includes 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, Empol trimer acid, and derivatives thereof such as acid anhydrides thereof and alkyl(1 to 3 carbon atoms) esters thereof. Among them, from the viewpoints of the softening point and the crystallinity of the resin, trimellitic acid and derivatives thereof are preferable.
In the present invention, in order to form a non-linear polyester as the crystalline polyester, it is desired that trivalent or higher polyvalent monomers, which are selected from the group consisting of trihydric or higher polyhydric al
Akiyama Koji
Aoki Katsutoshi
Fukushima Yoshihiro
Kanamaru Yutaka
Birch & Stewart Kolasch & Birch, LLP
Dote Janis L.
Kao Corporation
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