Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-09-15
2002-01-22
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...
C430S126200, C430S137210
Reexamination Certificate
active
06340549
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a toner for the development of an electrostatic image for use in the development of an electrostatic latent image in electrophotography or electrostatic recording method, a process for the preparation thereof, a developer for the development of an electrostatic image, and a process for the formation of an image.
A method for rendering an image data visible via electrostatic image such as electrophotography has been used in various fields. In electrophotography, an electrostatic latent image is formed on a photoreceptor at a charging/exposure step. The electrostatic latent image is developed with a developer containing a toner, and then processed at a transferring step and a fixing step to become visible. Examples of the developer to be used in electrophotography include two-component developer comprising a toner and a carrier and one-component developer comprising a magnetic or non-magnetic toner alone. Such a toner is normally prepared by a knead-grinding method which comprises melt-kneading a thermoplastic resin with a pigment, a static controller and a release agent such as wax, cooling the mixture, finely grinding the mixture, and then classifying the particles. In this method, inorganic or organic particles may be attached to the surface of the toner particles to improve the fluidity or removability of the toner.
On the other hand, with the recent development of advanced information-oriented society, there has been a growing demand for the provision of data documents built by various methods in an even higher image quality. Thus, the enhancement of image quality is understudy in various arts of image formation. This demand has been given to every art of image formation, not excepting image formation methods using electrophotography. In electrophotography, the development of technique for reducing a particulate toner having a reduced particle diameter and a sharp grain size distribution and making toner particles spherical is now under way to realize an even higher precision in color image formation.
Referring to the process for making toner particles spherical, the shape of the resulting toner particles has an effect on the precision in transferring of toner particles at the transferring step. The more spherical the toner particles can be kept until the final image is obtained, the smaller is the contact area of the toner particles with the carrier and hence the higher is the precision in transferring of toner particles and the more can be expected the enhancement of final image quality such as reproducibility of fine line.
However, there is a problem that when such spherical toner particles are used, the toner particles which have been left untransferred from the carrier can be hardly removed.
In order to remove the untransferred toner, a method using a blade is widely used because the device is simple and durable. In this blade cleaning method, however, it is much likely that spherical toner particles can be passed by the blade because of its shape, causing poor removability leading to deterioration of image quality. Thus, the art must consider how spherical toner particles used for higher image quality can be removed.
In order to solve this problem, some approaches have been attempted. One of these approaches is to raise the linear pressure applied to the edge of the blade, preventing the toner particles from being passed by the blade. However, this approach is disadvantageous in that the mere rise in linear pressure accelerates the abrasion of the edge of the blade and the carrier and causes the blade to vibrate and give noise.
In order to eliminate such noise and abrasion, an approach has been proposed which comprises supplying a particulate lubricant into the edge of the blade to reduce the friction coefficient of the edge of the blade. In order to efficiently reduce the friction coefficient of the edge of the blade with a lubricant thus supplied, the particle diameter of the particulate lubricant is preferably as small as about 0.2 &mgr;m or less. However, these submicron lubricant particles can be scattered inside the machine, staining the static charger or like parts and hence causing malcharging or like defects. The resulting image has a deteriorated quality.
Further, an approach has been proposed which comprises supplying onto the edge of the blade submicron irregular shape inorganic particles that then form a sealing material on the edge of the blade to make it difficult for spherical toner particles to be passed by the blade. This approach is based on a mechanism that spherical toner particles which can be otherwise easily passed by the blade are trapped by irregular shape particles such as irregular shape silica and alumina which have been supplied onto the blade of the blade. However, this approach, too, is disadvantageous in that the particle diameter of the irregular shape particles needs to be about 0.2 &mgr;m or less to be efficiently supplied onto the edge of the blade and prevent the spherical toner particles from being passed by the blade similarly to the foregoing lubricant. In this approach, too, problems arise as in the case of the foregoing lubricant.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to solve the foregoing problems. In other words, an object of the present invention is to provide a toner for the development of an electrostatic image which can give solution to the problems with poor removability of spherical toner particles without causing the foregoing problem of stain of the static charger or other parts with scattered submicron particles, a process for the preparation thereof, a developer for the development of an electrostatic image and a process for the formation of an image.
The inventors made extensive studies. As a result, the inventors found the use of a toner for the development of an electrostatic image formed by externally adding to spherical toner particles a predetermined amount of agglomerated particles having a shape factor of 130 or more and a volume-average particle diameter of from 0.5 &mgr;m to 10 &mgr;m which are made of (i) a particulate resin alone, (ii) a particulate lubricant alone or (iii) at least two particulate materials selected from the group consisting of particulate resin, particulate lubricant and inorganic particulate material. It is found that such agglomerated particles, if used, are disintegrated under load developed at the forward end of the cleaning member to form irregular shape particles having a diameter of 0.2 &mgr;m or less which are then effectively supplied into the edge portion of the cleaning member, making it possible to solve the foregoing problems with poor removability of spherical toner particles without causing the foregoing stain of the static charger with scattered submicron particles. In other words, the inventors found the following inventions <1>to <19>.
<1>A toner for the development of an electrostatic image comprising toner particles containing a binder resin and a colorant, and additive, said additive being agglomerated particles, characterized in that the agglomerated particles are made of (i) a particulate resin alone, (ii) a particulate lubricant alone or (iii) at least two particulate materials selected from the group consisting of particulate resin, particulate lubricant and inorganic particulate material and have a shape factor of 130or more as represented by the following equation I and a volume-average particle diameter of from 0.5 &mgr;m to 10 &mgr;m:
Shape factor=(
ML
2
/A
)×(&pgr;/4)×100 (I)
wherein ML represents the absolute maximum length of agglomerated particles, and A represents the projected area of agglomerated particles.
<2>The toner for the development of an electrostatic image according to Clause <1>, wherein the toner particles preferably have a shape factor of 125 or less and a volume-average particle diameter of 1 &mgr;m or more.
<3>The toner for the development of an electrostatic image accordi
Maehata Hideo
Matsumura Yasuo
Suwabe Masaaki
Yoshizawa Hisae
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