JPS6237781B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to resin-coated carriers for electrophotographic developers.

Traditionally, electrophotography has been covered by US patents.
No. 2297691, Special Publication No. 23910, Special Publication No. 1977-
These methods are described in Japanese Patent Application No. 24748, etc., but these methods charge the photoconductive layer uniformly and expose it to a light image corresponding to the original, thereby eliminating the charge in the exposed area and forming a latent image. The image is developed, transferred to paper or cloth as necessary, and permanently fixed by heating, pressure, etc. Methods for developing latent images include magnetic brush, cascade, fur brush, and one-component jumping development methods.

In the magnetic brush method using the product of the present invention, a mixture of carrier iron powder and toner is used as a developer. When this developer is used to continuously copy a large number of sheets, the frictional shearing force caused by mechanical impact causes phenomena such as pulverization of the toner, chipping of the carrier surface, or fusion of the toner on the carrier surface, which significantly impairs the tribo-generating function of the carrier. Deterioration of the developer occurs due to damage. The main cause of deterioration is that the carrier surface is covered with undeveloped toner accumulated during the process of continuous copying, and is fused by heat as described above, making it impossible to properly control tribocharging. Resin-coated carriers have been proposed to prevent these deteriorations, and most of the above-mentioned drawbacks can be overcome, but the resin used for these coatings is required to have low electrical resistance. However, since the general coating resin has a high electrical resistance, when the toner and carrier are frictionally charged, the electrode effect of the carrier is lost, and the toner is held on the carrier side and is difficult to develop, resulting in a thin image. Therefore, it is necessary to remove the charge on the carrier side to obtain adequate image density. Carbon black is known to have been used as a resistance adjuster, but pigments like carbon black have poor wettability with resins and do not have good durability. Furthermore, since tribo occurs at a location where the carrier and toner are rubbed together, if there is friction in an area where there is no carbon, that area will be held by the carrier. The present invention provides a coated carrier that overcomes these drawbacks. That is, the present invention is a coated carrier characterized in that the carrier coating resin contains an alkyl ester type surfactant represented by the following formula.

[R-COO(C ₂ H ₄ O) _o H] (In the formula, R represents C8 to C18, and n represents an integer.) Specific substances represented by the above formula include polyoxyethylene laurylate, poly These include oxyethylene oleate and polyoxystearate. These are added in an amount of 0.5 to 10 parts by weight, preferably 1 to 7 parts by weight, per 100 parts by weight of the coating resin.

A large number of coating resins can be used in the present invention, including known materials. Typical examples include various fluorinated polymers such as Teflon resin, melanin, xylene, polyphenylene oxide, silicone, polyester, polyamide, and various styrene compounds.

The method for producing a coated carrier according to the present invention involves using a solvent (toluone, xylene, MEK) in which the coating resin and the alkyl ester type surfactant are dispersed.
It is obtained by coating a carrier with a spray dryer method or a fluidized bed method, and drying and granulating it.
This will be explained below using examples.

Example 1 3000 g of 250 to 400 mesh iron powder (manufactured by Nippon Tetsuko KK, trade name EFV250/400), 150 g of styrene butyl acrylate resin, and 7.5 g of polyoxyethylene laurylate were heated in a toluene solution at a temperature of 50°C.
Stir for 30 minutes, then sprinkle in a flow coater (temperature inside chamber 80°C) and dry for about 20 minutes. The dried material was passed through a 100 mesh sieve and the material under the sieve was used as a carrier. on the other hand,
200 g of styrene acrylic toner and 2500 g of the carrier obtained above were placed in a V-type mixer and stirred for 5 minutes, and then placed in an NP-8500 machine as a starting developer and subjected to a durability test of 200,000 sheets. The results were good, with no change in image quality and image density after 200,000 copies.

Comparative Example A product was manufactured in the same manner as in Example 1 except that the polyoxyethylene laurylate in Example 1 was omitted, and a durability test was conducted. As a result, there was an edge effect from the start, and after 10,000 shots, the image became thinner and poorer.

Example 2 The same results as in Example 1 were obtained as a result of preparation and evaluation in the same manner as in Example 1 except that 10.5 g of polyoxyethylene oleate was used instead of polyethyleneoxyethylene laurylate in Example 1.

Example 3 An image was prepared and evaluated in the same manner as in Example 1, except that 1.5 g of polyoxystearate was used instead of polyethyleneoxyethylene laurylate in Example 1. As a result, a good image was obtained.

Claims (1)

[Scope of Claims] 1. A coated carrier characterized by being coated with an electrophotographic carrier coating resin containing an alkyl ester type surfactant represented by the following formula. [RCOO(C ₂ H ₄ O) _o H] (In the formula, R represents a C8-18 alkyl, and n represents an integer)