Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-01-15
2004-06-29
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C528S272000
Reexamination Certificate
active
06756171
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a polyester resin and a toner including the same, and more particularly, to a polyester resin for preparing a toner useful for developing an electrostatic latent image, such as a statically charged image, in an electrophotographic image forming process.
(b) Description of the Related Art
Generally, an image-forming process, such as the electrophotographic image forming process or an electrostatic printing process, includes the steps of forming an electrostatic latent image, such as a statically charged image or an electro-conductive image corresponding to a recorded image, on a surface of an electrostatic recording member, developing the latent image with charged toner, transferring the toner image on the electrostatic recording member onto a paper or a recording film, and finally fixing the transferred image. The image-forming process has some advantages in that the printed matter can be obtained with high speed, the image formed on the electrostatic recording member is stable, and an image-forming device for such electrophotography process is easy to manipulate. Accordingly, such an image-forming process is widely used in a field of copiers and printers.
In more detail, the image-forming process includes the following steps.
1. an charging process for electrically charging a drum(for example, organic photoconductor drum: OPC) coated with a photoconductive or a photosensitive material,
2. an exposing process for exposing the original image to be copied to a light, and forming an electrostatic latent image on the drum with the light reflected from the original image,
3. a developing process for statically adhering a charged toner onto the drum in a developing machine,
4. a transferring process for sticking a charged paper to the drum, and, electrostatistically transferring the toner from the drum to a paper,
5. a fixing process for fixing the transferred toner with a thermo-pressing roller,
6. a cleaning process for removing the residual toner on the drum,
7. a process for removing the residual charge on the drum by projecting a light.
Generally, the toner including crosslinked polyester as a binder is used in the developing process. Since the image-forming process should be rapidly performed to increase the operating efficiency of the copier or printers, there are various trials to increase the image-forming speed. It is important to increase the toner fixing speed onto the surface of the recording member for rapid image forming. To fix the toner rapidly, the toner should have superior fixing property at low and high temperature, but the toner including conventional polyester does not have such properties.
The low-temperature fixing property of toner can be improved by using a polyester of low softening temperature. However, the toner using polyester of low softening temperature has drawback in its transferability. Therefore, the toner may remain on the surface of the hot roller used for fixing the toner, and the contamination (generally called as “the offset”) of the following paper may occur.
As a binder for preventing the offset, the use of crosslinked polyester is generally known. The crosslinked polyester is obtained by reacting an esterified bisphenol A with dicarboxylic acid to produce a linear polyester, and then reacting the produced linear polyester with trivalent or higher carboxylic acid, such as trimellitic acid anhydride. However, the obtained crosslinked polyester has high softening temperature, thus the low-temperature fixing property of the toner is insufficient, and the desired rapid fixing property cannot be obtained. For example, when the same toner is used for the electrophotographic image forming process with a speed of about 50 sheets/minute, the fixing property of the toner is insufficient and the obtained copies does not have the desired toner fixing property.
Polyester having reduced softening temperature for producing a toner having superior offset preventing property and low-temperature fixing property can be obtained by performing the crosslinking reaction so that a long-chain aliphatic hydrocarbon is included into the polyester. However, such polyester has too low glass transition temperature (Tg), and the toner particles are liable to be flocculated while storage, which deteriorates the toner storage property.
In U.S. Pat. Nos. 4,804,622, 4,849,495, and 5,057,596, a binder for toner having improved offset preventing property, improved storage stability, and low and high temperature fixing property is disclosed. The binder includes polyester produced from dicarboxylic acid, diol, and at least one crosslinking agent selected from the group consisting of trivalent or higher carboxylic acid, and trihydric or higher alcohol. Especially, polyester which includes bisphenol A derivative as the diol component is disclosed as the binder. However, in case of an aromatic diol containing the bisphenol A derivative, for example, polyoxypropylene(2,3)-2,2i-bis(4-hydroxyphenyl) propane and polyoxyethylene(1,0)-2,2-bis(4-hydroxyphenyl) propane, the storage stability and low and high temperature fixing property of the toner according to mole number of a repeating unit, that is, ethylene oxide or propylene oxide group is not disclosed. That is, as shown in following chemical equation 1, the mole number w+z of the additional ethylene oxide in polyoxyethylene(1,0)-2,2-bis(4-hydroxyphenyl) propane and the mole number y+z of the additional propylene oxide in polyoxypropylene(2,3)-2,2-bis(4-hydroxyphenyl) propane are not same in every molecule, but has specific distribution, and the storage stability and the low and high temperature fixing property are varied according to the distribution degree.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polyester resin for producing a toner having improved storage stability, low-temperature and high-temperature fixing properties by optimizing the composition, the amount of each component, and the range of mole number of additional alkylene oxide in aromatic diol of bisphenol A derivative for the production of the polyester. It is another object of the present invention to provide a toner including the same polyester resin.
To achieve these objects, the present invention provides a polyester resin for toner comprising aromatic dicarboxylic acid, trivalent or higher carboxylic acid, aliphatic diol, aromatic diol of bisphenol A derivative, and trihydric or higher alcohol, characterized in that the amount of the aromatic diol of bisphenol A derivative having the mole number of ethylene oxide and/or propylene oxide of 2 mole is equal to or more than 85 weight % in the entire aromatic diol of bisphenol A derivative, and the amount of the aromatic diol of bisphenol A derivative having the mole number of ethylene oxide or propylene oxide of 1 mole is less than 0.2 weight % in the entire aromatic diol of bisphenol A derivative. The present invention further provides a toner including such polyester resin.
Preferably, the polyester resin has 1~25 KOHmg/g of acid value, 130~190° C. of softening temperature, and 50~70° C. of Tg.
DETAILED DESCRIPTION OF THE INVENTION
For a better understanding of the present invention, reference will now be made in detail to the following disclosures. In this specification, the amount of diacid component is represented by mol % in the total diacid components, the amount of trivalent or higher carboxylic acid is represented by mol % to the entire amount of diacid components, and the amount of alcohol component is represented by mol % to the entire amount of diacid components (i.e. mole of alcohol component to the 100 mole of the entire diacid components).
Acid component of the inventive polyester resin for the production of a toner comprises aromatic dicarboxylic acid and trivalent or higher carboxylic acid, and, if necessary, further comprises aliphatic dicarboxylic acid.
The preferable aromatic dicarboxylic acid includes dibasic acid such as terephthalic acid and isophthalic aci
Lee Kye Yune
Lee Tae Woong
Roh Jae Kyoung
Chapman Mark A.
Pennie & Edmonds LLP
SK Chemicals Co. Ltd.
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