JPS6115153A - Developer for positive charge image - Google Patents

Abstract

PURPOSE:To improve the cleanability of the surface of a photosensitive body and to obtain a clear image without causing filming by mixing externally a toner which is negatively charged by rubbing with iron powder as a carrier with metallic oxide powder treated with a compound which is positively charged by rubbing with the carrier. CONSTITUTION:A toner which is negatively charged by rubbing with iron powder as a carrier is mixed externally with metallic oxide powder treated with a compound which is positively charged by rubbing with the carrier such as aminosilane. The treated metallic oxide powder has high and uniform positive electrification, and when the negatively chargeable toner is mixed with the powder, positively chargeable fine powder is supported on the surface of the negatively chargeable toner. This toner coated with positively chargeable particles is mixed with iron powder as a carrier to manufacture a developer for a positive charge image. When the developer is used in a PPC electronic copying machine provided with a brush cleaning mechanism, the cleanability of the surface of the photosensitive body is improved, and a clear image free from fog can be obtd. without causing toner filming.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developer for developing positively charged images used in electrophotography.

As is well known, in PPC electrophotography, a required electrostatic latent image is formed on the surface of a photoconductor, and a developer containing a toner having an opposite charge is brought into contact with this electrostatic latent image to produce a toner image. The image is then transferred to transfer paper and fixed to obtain a visible image.

By the way, in such a toner transfer type electrophotographic method, the toner remaining on the photoreceptor after the transfer process must be cleaned in order to reuse the photoreceptor. This cleaning can be done using a brush, blade, magnetic brush, or a special transfer material. Brush cleaning is a method in which a cylindrical brush with a diameter of about 10 cm is rotated at high speed to brush off residual toner on the photoreceptor, and has been used for a long time since the development of xerographic copying machines. .

However, like other cleaning methods, this brush cleaning inevitably places a mechanical load on the surface of the photoreceptor, and moreover, the surface of the photoreceptor gets coated with toner due to repeated use! (filming) was formed, resulting in poor cleaning and deterioration of electrophotographic performance.

Therefore, many attempts have been made in the past to improve brush cleaning performance in terms of machines and toner materials. In other words, the fur of machinzide is made longer in order to prevent toner filming on the surface of the photoreceptor. Measures have been taken, such as increasing the number of rotations of the brush and changing the material of the fur, but these methods scratch the surface of the photoreceptor, and the desired results have not been obtained.

In addition, attempts have been made to improve the cleaning properties of toner materials by varying the charge potential and fixed resistance of the toner, increasing the particle size, and improving fluidity. This caused toner scattering, etc., and lacked a means to satisfy overall electrophotographic performance.

The present invention has been made in view of the above-mentioned circumstances. Metal oxide powder treated with a compound that becomes positively charged by friction with an iron powder carrier is externally mixed into a toner which becomes negatively charged by friction with the carrier. The object of the present invention is to provide a developer for positively charged images, which is characterized by the following characteristics, and thereby improves brush cleaning properties from the viewpoint of toner materials and makes it possible to obtain excellent image quality.

In the present invention, metal oxide powder treated with a compound that becomes positively charged by friction with an iron powder carrier includes silica, alumina, titanium dioxide, titanium oxide, zinc oxide, silica sand, clay, iron oxide, fluoride, etc. - The surface of a metal oxide powder such as light is treated with a positively charged compound such as aminosilane, hinylbilycine, or aminopyridine. Among these, silica surface-treated with aminosilane or a mixture of aminosilane and helimethyldisilazane (HMDS) is preferred.

Aminonlan used for surface treatment of metal oxide powder is a so-called aminofunxiolyl silane, and has the general formula m5iYn (X is an alkoxy group or a chlorine atom, ``Kabura'' is an integer from 1 to 3, and Y is a primary to tertiary amino group. Hydrocarbon group with 3 openings
), for example, the following compound CH3 □ 82N-CH2C)(2N)(C)(2CH2C)12
s H-(OCI-13)2 82N-CONI(-CH2C)12C)I2-3i-
(OC2H6)3 H2N CH2CH2CH25I (OCH2CH3
)al-12Nc)I2C82N)lcH2c)]2C
Examples include H2Si(OCH3)3, and these may be used alone or in a mixed system of two types.

The aminosilane-treated metal oxide powder thus obtained has an extremely strong uniform positive charge, and this is combined with the toner, which becomes negatively charged by friction with the carrier iron powder.
By mixing using a mechanical means such as a Henschel mixer, positively charged fine powder is supported on the surface of the negatively charged toner.

In this case, the mixing ratio is 0.05 to 2%, preferably 0.1 to 0.5%, of the positively charged fine powder to 100 parts of the negatively charged toner.
%, but what is important at this time is that the frictionally charged polarity of the L-ner particles whose surfaces are covered with positively charged fine powder particles maintains their negative chargeability through friction with the carrier iron powder. This is the reason why a positively charged image on a photoreceptor such as selenium is developed. Further, the toner that becomes negatively charged due to friction with the carrier includes all negatively charged toners of ordinary two-component developers. In other words, acrylic resin, styrene-acrylic copolymer, polyester, epoxy resin, etc. are used as the binder resin, and various negatively charged metal-containing dyes, carbon black, and other coloring pigments and additives are blended with this resin. It is obtained by melt-kneading and pulverizing.

The toner whose surface is covered with positively charged particles is mixed with a conductive carrier iron powder or a coating carrier that is normally used in two-component developers to obtain the positively charged image developer of the present invention.

When the thus obtained developer of the present invention was applied to a PPC electronic copier having a brush cleaning mechanism, the cleaning performance of the photoreceptor surface was extremely good, there was no toner filming, and clear images without fog were always produced during development. was able to obtain.

Further, in the present invention, since the developer itself has a cleaning function, the range of selection of the material of the fur brush, the rotation conditions of the brush, etc. is widened, and there are many advantages as a cleaning system.

Next, Examples and Comparative Examples of the present invention will be described.

EXAMPLE The above components were melt-kneaded in an extruder and then pulverized and classified to prepare a negatively chargeable l-ner having an average particle diameter of 14 μm and a blow-off charge amount of 124 μc/g. 0.2 parts by weight of positively charged silica fine powder (Aerosil RA 20011, manufactured by Nippon Aerosil Co., Ltd.) having a BET surface area of about 130 nt/g that has been surface-treated with aminosilane and HMDS is mixed with 100 M parts of the toner using a Henschel mixer;
A negatively charged toner having positively charged silica supported on its surface area was obtained. 6 parts by weight of this toner is mixed with conductive carrier iron (TE
By mixing with 100 parts by weight of F V2O0/: +00, manufactured by Nippon Tetsuko Co., Ltd., the rib blow-off charge amount is 121μ
A developer of the present invention of c/g was obtained.

When this developer was applied to a PPC electronic copying machine equipped with a selenium photoreceptor and a brush cleaning mechanism and more than 50,000 copies were made continuously, clear images without fogging or scumming could be maintained. Furthermore, it was confirmed that this clear image was due to the cleaning tendency of the surface of the photoreceptor.

Comparative Example The above components were melt-kneaded in an extruder, then pulverized and classified to obtain an average particle size of 14 (tm, blow-off charge ik
-14ltc/gh nawo production site. d h Chi 1
O0! 0.2 parts by weight of hydrophobic Silituno (A]-Rosil R972, manufactured by Japan AJ-Rosil Co., Ltd.), which is strongly negatively charged by friction with carrier iron powder, is mixed in a Henschel Migisser, A negatively charged toner supported on the surface of the negatively charged toner was obtained. By mixing 6 parts of this toner with 100 parts by weight of conductive carrier iron (TEFV200/300), a developer having a blow-off charge amount of 12 luc/g was obtained.

When this developer was applied to an I)PC electronic copying machine with a selenium photoreceptor and a brush cleaning mechanism for continuous copying, the initial images were clear and good. During copying, filming occurred on the photoreceptor surface due to poor cleaning, resulting in an unclear image with a lot of scumming.

Claims (2)

[Claims] (1) A developer for positively charged images, characterized in that a metal oxide powder treated with a compound that becomes positively charged by friction with an iron powder carrier is externally mixed with a toner which becomes negatively charged by friction with the carrier. . (2) The developer for positively charged images according to claim 1, wherein the compound that becomes positively charged by friction with the iron powder carrier is aminosilane.