Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-03-30
2001-02-06
Martin, Roland (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S111400
Reexamination Certificate
active
06183928
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for full color development used for development of electrostatic latent images which are formed in electrophotography, electrostatic recording method, electrostatic printing method, or the like.
2. Discussion of the Related Art
Heat roll fixing methods have been widely employed as a method for fixing of a visible image. In the toner for full color development, since a polymer having a low molecular weight and a narrow molecular weight distribution is used as a resin binder in order to satisfy the melting characteristics important for color reproducibility, the resulting toner has a narrow fixable region. In order to solve such a problem, therefore, a silicone oil is applied on a heat roll. However, there arise such defects that the device becomes larger in size, and that a silicone oil remains on the transferred sheets, which makes it difficult to over-write thereon.
Japanese Patent Laid-Open Nos. Hei 6-59505, Hei 8-220808, and the like each discloses a toner comprising a polyester and a releasing agent having a low melting point. However, there have not yet been reported any toners satisfying many of properties required for toners for full color development such as durability and color reproducibility.
An object of the present invention is to provide a toner for full color development having a wide fixable region, and being excellent in durability and color reproducibility.
The above object and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
The present invention relates to a toner for full color development comprising:
(a) a resin binder comprising a polyester;
(b) a releasing agent having a melting point of 60°to 115° C.;
(c) a colorant; and
(d) an external additive,
wherein the toner has a sum of an acid value and a hydroxyl value of from 40 to 60 KOH mg/g, a softening point of from 97° to 115° C., and a glass transition point of from 58° to 65° C., and wherein the amount of the external additive is from 1 to 5 parts by weight, based on 100 parts by weight of a toner without a treatment with the external additive.
DETAILED DESCRIPTION OF THE INVENTION
The toner of the present invention has a sum of an acid value and a hydroxyl value of 40 KOH mg/g or more, in order to improve the durability, and a sum of 60 KOH mg/g or less, in order to improve the color reproducibility. Therefore, the toner has a sum of an acid value and a hydroxyl value is from 40 to 60 KOH mg/g, preferably from 42 to 50 KOH mg/g. The sum of an acid value and a hydroxyl value corresponds to the number of terminal functional groups per unit weight, and the sum is closely related to many of molecular structural features such as polarity, average molecular weight, and cross-linking degree of a resin binder which is a main component of the toner. Therefore, the sum is an index highly significant to the toner properties such as durability, triboelectric chargeability, and color reproducibility.
The toner of the present invention has an acid value of preferably from 1 to 50 KOH mg/g, more preferably from 1 to 30 KOH mg/g, in order to obtain an appropriate level of the triboelectric charges.
The toner of the present invention has a hydroxyl value of preferably from 10 to 60 KOH mg/g, more preferably from 10 to 50 KOH mg/g, still more preferably from 20 to 50 KOH mg/g, from the viewpoint of the environmental stability of the triboelectric charges.
The toner of the present invention has a softening point of from 97° to 115° C., preferably from 98° to 112° C., from the viewpoint of the fixable region.
The toner of the present invention has a glass transition point of from 58° to 65° C., preferably from 60° to 63° C., from the viewpoints of the storage stability and the durability.
The resin binder usable for the toner of the present invention comprises one or more kinds, preferably from 1 to 3 kinds of polyesters. It is desired that the content of the polyester is from 50 to 100% by weight, preferably from 90 to 100% by weight, more preferably 100% by weight, in the resin binder, from the viewpoints of the dispersibility of the colorant, the fixing ability and the durability. Incidentally, the resins which can be used for the resin binder other than the polyester include styrene-acrylic resins, epoxy resins, polycarbonates, polyurethanes, and the like.
The polyester is obtainable, for instance, by polycondensing an alcohol component comprising a compound represented by the formula (I):
wherein R is an alkylene group having 2 to 4 carbon atoms; and each of x and y is a positive number, wherein a sum of x and y is from 1 to 16, with a carboxylic acid component comprising a dicarboxylic acid compound.
In the present invention, the alcohol component contains the compound represented by the formula (I) in an amount of preferably 5% by mol or more, more preferably 50% by mol or more from the viewpoints of the dispersibility of the colorant and the fixing ability.
The compound represented by the formula (I) includes alkylene oxide adducts (additional molar number: 1 to 16) of bisphenol A such as polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane and polyoxyethylene(2.2)-2,2-bis(4-hydroxyphenyl)propane. In addition, other alcohol components include ethylene glycol, propylene glycol, glycerol, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or alkylene oxide adducts (additional molar number: 1 to 16) thereof of which alkylene moiety has 2 to 4 carbon atoms. These alcohol components comprise one or more of these compounds.
The carboxylic acid component comprises a dicarboxylic acid compound and, optionally, a tricarboxylic or higher polycarboxylic acid compound.
The dicarboxylic acid compound includes phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, adipic acid, substituted succinic acids having a substituent such as 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, anhydrides thereof, and alkyl(1 to 8 carbon atoms) esters thereof, and the like.
The tricarboxylic or higher polycarboxylic acid compound includes trimellitic acid, pyromellitic acid, acid anhydrides thereof, alkyl(1 to 8 carbon atoms) esters thereof, and the like.
The polycondensation of the alcohol component with the carboxylic acid component can be carried out, for instance, by reacting the components at a temperature of from 180° to 250° C. in an inert gas atmosphere, optionally in the presence of an esterification catalyst.
The toner of the present invention comprises one or more kinds, preferably 1 to 3 kinds, of polyesters. Here, in one embodiment, a linear polyester is preferably used. In addition, the linear polyester is excellent in the fixing ability and the color reproducibility, while a cross-linked polyester is excellent in the durability. Therefore, in another embodiment, these two kinds of polyesters are used in admixture.
In the present invention, the linear polyester is preferably one obtained by using a carboxylic acid component comprising a tricarboxylic or higher polycarboxylic acid compound in an amount of less than 5% by mol and/or an alcohol component comprising a trihydric or higher polyhydric alcohol in an amount of less than 5% by mol, especially one obtained by using an alcohol component and a carboxylic acid component without containing any of trihydric or higher alcohol and tricarboxylic or higher polycarboxylic acid compound.
Also, the cross-linked polyester is preferably one obtained by using a carboxylic acid component comprising a tricarboxylic or higher polycarboxylic acid compound in an amount of from 5 to 50% by mol and/or an alcohol component comprising a trihydric or higher polyhydric alcohol in an amount of 5 to 50% by mol, especially one obtained by using the carboxylic acid component comprising a tricarboxylic or higher polycarboxylic acid compound in an amount of 5 to 50% by mol. Incidentally, in this case, it
Sata Shin-ichi
Shirai Eiji
Birch & Stewart Kolasch & Birch, LLP
Kao Corporation
Martin Roland
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