Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1999-11-15
2001-10-02
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S120400
Reexamination Certificate
active
06296980
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a toner for developing electrostatic image and an image forming method employing the toner, applied to a copying machine a printer and so on.
BACKGROUND OF THE INVENTION
In the electrophotography heat-pressure fixing method in which an image folding material having an image formed with toner is transferred between heating roller and pressure roller to fix the image, is widely employed because the apparatus therefor is simple and fixing property to a support such as a paper is satisfactory. In this method transmission of heat to the toner is caused by contact with the heating roller, and toner is fused by the heat. This method has disadvantage to tend to bring offset phenomenon, which fused toner adheres to the heat roller, as fused toner contact with the heating roller.
Various means for improving image disarrange caused by the offset have been proposed. In general the offset is explained as it occurs in case that adhesive force between the toner and heating parts such as heating roller is greater than the inner coagulation force. On the other hand, many methods of addition of agent giving releasing ability into a toner are proposed in view of the adhesion to heating device. Further, methods to prevent offset phenomenon by coating silicone oil etc. on a heating device is also proposed. These method demonstrate the effect by employed solely or in combination.
There is another problem of fixing property in heat-pressure fixing, which adhesion characteristics to a transfer material such as paper. There are methods employing with high fixing temperature or rather induce offset phenomenon. For these reasons, many improvement methods have been proposed of resins as for fixablity in view of viscosity when the toner melts.
It is a extremely important problem how to obtain wider fixable temperature range between the fixable minimum temperature and the temperature at which offset occurs. The problem has not been dissolved satisfactory, particularly, for small particle size toner and color tone.
There have been other subjects such as obtaining high quality image at initial stage, preventing of grade down of image quality as repeating employing, and preventing poor image in a process utilizing electrostatic image developing toner. For example, the problems includes gradation characteristics, reproduction ability of fine lines, change of image density, uneven image density, fogging. These are manly caused by unstable toner charging quantity, which is difficult in controlling. Stabilizing and controlling of charge quantity of toner are extremely difficult as the charging is caused triboelectrically.
Various kinds of improvement such as binder resin for toner, charge control agent, external additives, other additives and so on, have been proposed for above mentioned problems. However, further improvement in higher image quality and higher durability of developer are demanded in accordance with the progress of performance and reliability in each step of image forming process utilizing the toner.
In recent years, the electrophotography has been applied to various fields. For example, printer for output terminal of computer, color copying machine, color printer in addition to monochrome copying machine. As advancing of utility for the area, higher image quality is much more demanded. Variation of hue of secondary color by superposing color images becomes remarkable because of slight change of developing property (amount of residual toner) caused by very little change of charging characteristics etc., or change of transferring characteristics of half tone image in the image forming method in which toner images by color toner are superposed multiply. And consequently demand for stabilizing charging characteristics becomes extremely strict. Similarly stabilization of charging characteristics is demanded extremely strict in image forming method employing digital exposing which requires reproduction of fine lines.
SUMMARY OF THE INVENTION
The object of the invention is to provide a toner capable of forming images which exhibit minimal offsetting, excellent fixing property, developability, fine line reproducibility, and forming high quality images over a long period of time and an image forming method employing the toner.
The invention and embodiments of the invention are described.
1. A toner for developing electrostatic image comprising a resin and colorant wherein the toner has a variation coefficient of shape coefficient of not more than 16 percent and a number variation coefficient in the number particle size distribution of not more than 27 percent.
2. The toner described above wherein at least 65 percent of toner particles has a shape coefficient in the range of 1.0 to 1.6.
3. The toner described above wherein at least 65 percent of toner particles has a shape coefficient in the range of 1.2 to 1.6.
4. The toner described in above items 1 to 3, wherein at least 50 percent of toner particles in number have no corners.
5. The toner described above in items 1 to 4, wherein number average particle diameter of toner particles is 3 to 8 &mgr;m.
6. The toner described above in 1 to 5, wherein the toner has M of at least 70 percent, M being sum of m1 and m2 wherein m1 is relative frequency of toner particles, included in the most frequent class, and m2 is relative frequency of toner particles included in the second frequent class in a histogram showing the particle size distribution, which is drawn in such a manner that natural logarithm lnD is used as an abscissa, wherein D (in &mgr;m) represents the particle diameter of a toner particle, while being divided into a plurality of classes at intervals of 0.23, and number of particles is used as an ordinate.
7. The toner described in above 1 to 6, wherein the toner is prepared by polymerizing polymerizable monomers an aqueous medium.
8. The toner described above in 1 to 7, wherein the toner is prepared by a method wherein resin particles are associated in an aqueous medium.
9. A toner for developing electrostatic image comprising a resin and colorant wherein at least 50 percent of toner particles in number have no corners and the toner particles have a number variation coefficient in the number particle size distribution is not more than 27 percent.
10. The toner described in above item 9 wherein at least 65 percent of toner particles has a shape coefficient in the range of 1.0 to 1.6.
11. The toner described in above item 9 wherein at least 65 percent of toner particles has a shape coefficient in the range of 1.2 to 1.6.
12. The toner described in above items 9 to 11, wherein number average particle diameter of toner particles is 3 to 8 &mgr;m.
13. The toner described in above items 9 to 12, wherein the toner has M of at least 70 percent, M being sum of m1 and m2 wherein m1 is relative frequency of toner particles, included in the most frequent class, and m2 is relative frequency of toner particles included in the second frequent class in a histogram showing the particle size distribution, which is drawn in such a manner that natural logarithm lnD is used as an abscissa, wherein D (in &mgr;m) represents the particle diameter of a toner particle, while being divided into a plurality of classes at intervals of 0.23, and number of particles is used as an ordinate.
14. The toner described in above items 9 to 13 wherein the toner is prepared by polymerizing polymerizable monomers an aqueous medium.
15. The toner described in above items 9 to 14 wherein the toner is prepared by a method wherein resin particles are associated in an aqueous medium.
16. A toner for developing electrostatic image comprising a resin and colorant wherein at least 65 percent of toner particles has a shape coefficient in the range of 1.0 to
1.6 and a variation coefficient of shape coefficient of not more than 16.
17. The toner described in above item 16 wherein at least 50 percent of toner particles in number have no corners.
18. The toner described in above items 16 or 17 wherein number average particle diameter of toner parti
Kouno Shigenori
Matsushima Asao
Ohmura Ken
Oshiba Tomomi
Yamanouchi Takao
Bierman Jordan B.
Bierman, Muserlian and Lucas
Goodrow John
Konica Corporation
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