Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-04-29
2004-12-07
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...
C430S109200
Reexamination Certificate
active
06828074
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a binder resin usable in toners for developing electrostatic latent images, a toner for developing electrostatic latent images, an image-forming method making use of the toner and an image-forming apparatus making use of the toner. More particularly, it relates to a binder resin, a toner for developing electrostatic latent images, an image-forming method and an image-forming apparatus which are used in electrophotography, electrostatic recording and electrostatic printing performed in copying machines, printers, facsimile machines and so forth, in which a toner image is previously formed on an electrostatic-latent-image-bearing member (hereinafter simply “image-bearing member”) and is thereafter transferred onto a transfer medium to form an image. Still more particularly, it relates to a binder resin which has a biodegradability and at the same time contributes to superior fixing performance (low-temperature fixing performance, fixing temperature characteristics and anti-offset properties) and blocking resistance, and which has hydrolyzability and biodegradability and can readily be deinked, where existing deinking systems can be utilized as they are, also enabling waste disposal with ease; a toner for developing electrostatic latent images which contains such a binder resin; and an image-forming method and an image-forming apparatus which make use of the toner.
2. Related Background Art
A number of methods are conventionally known as methods for electrophotography. In general, copies are obtained by forming an electrostatic latent image on an image-bearing member (photosensitive member) by utilizing a photoconductive material and by various means, subsequently developing the latent image by the use of a toner to form a visible image (toner image), transferring the toner image to a transfer medium as occasion calls, and then fixing the toner image to the transfer medium by heating and/or pressing. As methods by which the electrostatic latent image is formed into a visible image, cascade development, magnetic brush development, pressure development and so forth are known in the art. Another method is also known in which, using a magnetic toner and a rotary developing sleeve provided with magnetic poles at the core, the magnetic toner is caused to fly from the developing sleeve surface to the photosensitive member surface by the aid of an electric field.
As development methods used when electrostatic latent images are developed, available are a two-component development method making use of a two-component type developer comprised of a toner and a carrier and a one-component development method making use of no carrier and comprised only of a toner.
Now, fine colored particles commonly called a toner are constituted of a binder resin and a colorant as essential components and besides optionally a magnetic material and so forth. Here, the binder resin occupies the greater part of the toner, and hence the physical properties of such a binder resin influence toner's physical properties greatly. For example, the binder resin is required to have delicate hardness and thermal melt properties, and a toner obtained by pulverizing a binder resin having a colorant and so forth dispersed therein followed by classification must show good fluidity without producing any fine powder against a mechanical impact caused by agitation in a developing assembly and also without causing agglomeration of the toner itself. Also, at the time of fixing, the toner must immediately melt at a low temperature and, when melts, the molten toner must show agglomeration properties. Namely, the controlling of binder resin's physical properties enables control of toner's physical properties.
As the binder resin, conventionally used are a styrene-acrylate copolymer, polyester resin, epoxy resin, olefinic resin and so forth. In particular, polyester resin is widely used at present as a resin for toners for heat-roll fixing, because, e.g., it has advantages such that, when melt, it makes toner additives such as carbon black disperse well and is well wettable to transfer paper.
In recent years, from the viewpoint of environmental conservation, it is also of worldwide consciousness how resources be recycled, how waste be curtailed, how the safety of waste be improved, and so forth. Such a subject is not exceptional also in the field of electrophotography. More specifically, with wide spread of copying machines and printers, the disposal of fixed toner on paper, waste toner after use, printed paper, copying paper and so forth is increasing year by year. Here, conventional toners are sparingly degradable because they are constituted of components all of which are stable artificial compounds, and may remain in all environment, e.g., in soil and in water over a long period of time. Hence, there is a possibility that they may come to be a source of environmental pollution when toners having been used are, e.g., buried in soil for their disposal. Also, in order to recycle resources, it is one of important subjects to regenerate plain paper for its reuse. However, conventional binder resins composed chiefly of styrene resins, it is difficult to remove them from paper surface (deinking) by alkali hydrolysis. This has come to be one of difficulties in the recycling of plain paper. The safety of waste is also an important subject from the standpoints of the conservation of global environment and the influence on human bodies.
Under such circumstances, development is being made on resins which are harmless to human bodies and degradable by the action of microorganisms, i.e., biodegradable resins. For example, it has been reported that many microorganisms are capable of producing a biodegradable resin having a polyester structure (polyhydroxyalkanoate; hereinafter abbreviated “PHA”) and accumulating it in the bacterial body (“Handbook of Biodegradable Plastics”, Biodegradable-Plastic Institute, K.K. NTS, pp.178-197, 1995). It is known that such a PHA can have various compositions and structures depending on the type of microorganisms used for its production, the composition of culture medium, the conditions for culturing and so forth. Researches on how to control the composition and structure of the PHA to be produced have hitherto chiefly been made from the viewpoint of the improvement in its physical properties. With regard to the application of such biodegradable resins, they have already given reasonable actual results especially in the field of materials for medical use. In the field of agriculture, too, the biodegradable resins have been put into practical use in multifiles, gardening material, sustained-release agricultural chemicals, fertilizers and so forth. In the field of leisure industry, too, the biodegradable resins are used in fishing lines, fishing articles, golf goods and so forth. Besides, as packaging materials for daily necessities, they have been put into practical use in containers or the like of living articles. However, considering their wide application as plastics, under the existing conditions they can not still be said to be satisfactory in respect of physical properties. For example, in order to make the PHA utilizable in much wider ranges, it is important to study the improvement of physical properties more widely. For that end, it is essential to make development and research on PHAs containing monomer units of various structures.
In the field of electrophotography, too, methods in which biodegradable resins are used in binder resins are proposed as methods by which toners which are disposable without causing environmental pollution are realized. For example, Japanese Patent Application Laid-Open No. 6-289644 discloses an electrophotographic toner particularly used for heat-roll fixing, which is characterized in that at least a binder resin contains a vegetable wax and a biodegradable resin (as exemplified by polyesters produced by microorganisms and natural polymeric materials derived from vegetables or ani
Imamura Takeshi
Kenmoku Takashi
Sugawa Etsuko
Yano Tetsuya
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