JP2921992B2 - Carrier for full color copier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic carrier,
In particular, the present invention relates to a carrier for a full-color copying machine in a two-component developer including a toner and a carrier.

[0002]

2. Description of the Related Art Electrophotography is disclosed in US Pat.
As disclosed in JP-B-42-23910 and JP-B-43-24748, the developer used in this method usually contains relatively fine toner particles and relatively large carrier particles. And the toner particles are retained on the surface of the carrier particles by electrostatic force of the opposite polarity generated by the contact of the particles,
When the developer contacts the electrostatic image on the photoreceptor, the toner particles are attracted to the electrostatic image to form an image,
This is transferred to paper or the like, and then heat-fixed.

Further, in recent years, an electrostatic latent image of an original is formed by exposing with a spectrally separated light, and this is developed with a color toner of each color to obtain a colored copy image or to superimpose a copy image of each color. In addition, a color copying method for obtaining a full-color copy image has been put to practical use, and a carrier for a color copying machine used for the method has been manufactured. As the carrier for the color copying machine, a granular or flat atomized iron powder or sponge iron powder coated with a silicone resin is used (for example, JP-B-53-42259 and JP-B-53-25959).
-26945, 61-39663 and Tokuhei 2-
No. 3181).

[0004] The above-mentioned carrier for a color copying machine is required to have the following characteristics in the same manner as a normally used black carrier. Excellent triboelectric characteristics and no change in image quality. Provide sufficient concentration. Deterioration is less for repeated continuous use.

[0005]

However, a polyester resin is generally used for a color toner, and a conventional carrier coated with the above-mentioned silicone resin or the like,
Since the spent toner easily adheres to the carrier, problems such as a decrease in charge amount, a decrease in density due to an increase in developer resistance, and chipping at the leading end occur.

Accordingly, an object of the present invention is to provide a long-life carrier for a full-color copying machine which has solved the above-mentioned problems, that is, has excellent chargeability and durability.

[0007]

SUMMARY OF THE INVENTION The present invention provides the above object,
A carrier comprising a core material coated with at least two layers, wherein the lower layer coating material is an ethylene tetrafluoride-based resin containing a polyamideimide resin, and the surface layer coating material is an ethylene tetrafluoride perfluoroalkyl vinyl ether copolymer resin. And a core material is a mixture of 60 to 80% by weight of iron powder and 40 to 20% by weight of spherical ferrite, thereby providing a carrier for a full-color copying machine.

Hereinafter, the carrier for a full-color copying machine of the present invention will be described in detail. In the carrier of the present invention, as the tetrafluoroethylene-based resin containing a polyamideimide resin used as a lower layer coating material, a resin containing 10 to 40% by weight of a polyamideimide resin represented by the following formula 1 as a binder is preferable. Specifically, Teflon S958-207, 958P-10255 manufactured by DuPont.
And the like.

[0009]

Embedded image

As the tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin used as the surface layer coating material, those having an alkyl of C _{1 to} C ₃ are preferred. 500CL, M
P-10, MP-102, MP-103 and the like.

The iron powder used as the main material of the core material in the carrier of the present invention is preferably a sponge iron powder having a flattened average particle diameter of 60 to 150 microns. When the flat iron powder is used, the resistance change of the developer is small even if the spent toner is slightly adhered. However, flat iron powder has the disadvantage that the ears on the sleeve become longer, the developing torque increases, and the coating resin tends to peel off.

By mixing the spherical ferrite with the iron powder, the developing torque is reduced and the peeling of the coating resin is reduced. However, if the mixing ratio of the spherical ferrite exceeds 40% by weight, the ears on the sleeve become extremely short, and do not meet the iron powder-based development conditions, resulting in a decrease in image density. On the other hand, when the content is less than 20% by weight, the developing torque becomes large, and the coating resin is easily peeled off. Therefore, the amount of spherical ferrite mixed with the iron powder is 20 to 40% by weight in the core material. The spherical ferrite has an average particle size of 6%.
Preferably from 0 to 150 microns.

The coating of the core material with the above coating material may be performed, for example, as follows.

First, an ethylene tetrafluoride resin containing a polyamideimide resin as an undercoat is dispersed in a single solvent such as methyl ethyl ketone or tetrahydrofuran or a mixed solvent thereof to prepare a resin solution. Spray coat the core material. After spray coating, heat treatment is performed at 250 to 350 ° C. for about 30 minutes while fluidizing the core material. Next, a resin solution is prepared by dispersing a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin in a solvent such as methanol as a top coat, and the resin solution is spray-coated on an undercoated core material. After spray coating, heat treatment is performed at 250 to 300 ° C. for about 30 minutes while fluidizing the core material. In addition, the resin coating amount is
Preferably, the undercoat is 1.0 to 2.0% by weight and the top coat is 1.5 to 2.5% by weight. Further, without being limited to the above two layers, an intermediate layer may be provided.

The toner used in combination with the carrier of the present invention is preferably a polyester toner having a positive polarity.

[0016]

The present invention will be specifically described below with reference to examples and comparative examples.

Embodiment 1

Flat iron powder (average particle size: 63.3 microns)
/ Spherical ferrite (average particle size: 110.3 microns) =
Teflon S-958-20 is used as an undercoat for 100 parts by weight of a core material composed of 60/40 (weight ratio).
7 (manufactured by DuPont) was dispersed in tetrahydrofuran to prepare a resin solution (coating solution). This resin solution was spray-coated on the above core material using a fluidized coating apparatus, and then 330 ° C in a fluidized bed.
For 30 minutes. Next, X as top coat
2.0 parts by weight of -500CL (manufactured by DuPont) was dispersed in methanol to prepare a resin solution. After performing the spile coating in the same manner as the undercoat, a heat treatment was performed in a fluidized bed at 280 ° C. for 30 minutes to produce a carrier of the present invention having two resin coatings.

To 1000 parts by weight of the thus-obtained coated carrier, 60 parts by weight of a commercially available full-color toner (positive toner) were mixed with a 5 LV blender to prepare a developer. The charge amounts of this developer by the blow-off method were 21 μC / g for yellow, 20 μC / g for magenta, and 20 μC / g for cyan. Using this developer, a continuous actual copying test was performed with a full-color copying machine using a commercially available OPC photoreceptor. Even after actual copying of 20,000 sheets, a beautiful copy with high image density and no image quality was observed, with little difference from the initial image quality. was gotten. At this time, the charge amount of the developer was 22 μC / g for yellow and 20.5 μC / g for magenta.
g and cyan were stable at 21 μC / g, which proved to be excellent in chargeability and durability.

Embodiment 2

The core material is flat iron powder / spherical ferrite = 80
/ 20 parts by weight, and the lower layer resin is 958P manufactured by DuPont.
A carrier of the present invention was produced in the same manner as in Example 1 except that the value was changed to -10255, and a developer was obtained in the same manner as in Example 1 using the carrier. Using this developer, a continuous real-photographing test was performed in the same manner as in Example 1 above. As a result, a beautiful copy with high image density and high image density was obtained without any significant difference from the initial image quality even after 20,000 actual copies were taken.

Embodiment 3

The core material is flat iron powder / spherical ferrite = 70
A carrier of the present invention was produced in the same manner as in Example 1 except that the amount was / 30 parts by weight, and a developer was obtained in the same manner as in Example 1 using the carrier. Using this developer, a continuous real-photographing test was performed in the same manner as in Example 1 above. As a result, a beautiful copy with high image density and high image density was obtained without any significant difference from the initial image quality even after 20,000 actual copies were taken.

Comparative Example 1

The core material is flat iron powder / spherical ferrite = 50
A carrier comprising a core material coated with at least two layers in the same manner as in Example 1 except that the carrier is manufactured in the same manner as in Example 1 except that the amount is / 50 parts by weight, The lower layer coating material is a polytetrafluoroethylene-based resin containing a polyamideimide resin, the surface layer coating material is a polytetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin, and the core material is iron powder 60 to 80% by weight. A continuous real-photographing test characterized by a mixture of spherical ferrite of 40 to 20% by weight showed that the initial charge amount and the change in the charge amount in the continuous real-photographing test were reduced, and that the fog was extremely low in the initial and continuous real-photographing tests. It turned out that the image quality was extremely high, and it was not applicable to a carrier for a full-color copying machine.

Comparative Example 2

A test was conducted in which the core material of Example 3 was coated with a single layer of Teflon S958-207 manufactured by DuPont, which is a tetrafluoroethylene resin containing a polyamideimide resin, without a top coat.

The method for producing the carrier and the method for producing the developer are as follows.
The procedure was performed in the same manner as in Example 3 except that the top coat was not applied. When a continuous actual shooting test was performed using the obtained developer, the charge amount increased in the middle, and a sensor for keeping the toner concentration of the developer constant could not be controlled, and the toner concentration decreased. For this reason, it was found that the image density was remarkably reduced, and it was not applicable to a carrier for a full-color copying machine.

[0029]

The carrier for a full-color copying machine according to the present invention is a long-life carrier excellent in chargeability and durability, and is particularly suitably used for a magnetic brush method.

Continuation of front page (72) Inventor Shuichi Miya 425 Kanai, Shibukawa-shi, Gunma Kanto Denka Kogyo Co., Ltd. Research and Development Center (56) References JP-A-54-92242 (JP, A) JP-A-54-126040 (JP, A) JP-A-55-67754 (JP, A) JP-A-62-18967 (JP, A) JP-A-52-154640 (JP, A) JP-A-60-239758 (JP, A) ( 58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 9/113 G03G 9/107 CA (STN)

Claims (2)

(57) [Claims] 1. A carrier comprising a core material coated with at least two layers, wherein the lower layer coating material is an ethylene tetrafluoride-based resin containing a polyamideimide resin, and the surface layer coating material is ethylene tetrafluoride perfluoro. An alkyl vinyl ether copolymer resin, wherein the core material is iron powder 60 to 80;
1% by weight and a mixture of 40 to 20% by weight of spherical ferrite. 2. The carrier for a full-color copying machine according to claim 1, wherein the iron powder is a flat iron powder having an average particle size of 60 to 150 microns.