JPS62238580A - Carrier for electrophotographic developing agent - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic developer, particularly a carrier in a two-component developer consisting of a toner and a carrier.

More specifically, the present invention relates to an electrophotographic developer carrier made of substantially spherical magnetite containing hematite.

In conventional electrophotography, the dry developer used to develop an electrostatic image formed on a photoreceptor by a magnetic brush method is a two-component developer consisting of toner and carrier. This developer typically consists of a mixture of relatively fine toner particles and relatively large carrier particles, with the toner particles being retained on the surface of the carrier particles by electrostatic charges of opposite polarity created by the contact of the particles. When this developer comes into contact with the electrostatic charge image on the photoreceptor, toner particles are attracted to the electrostatic charge image to form an image. In this case, the toner particles must necessarily have the correct chargeability and charge magnitude so that they are preferentially attracted to the desired image area on the photoreceptor.

The special requirements for the carrier used in the sleepy brush development method are that it has appropriate triboelectrification properties7 and retains toner particles well, and has a mechanical strength that does not cause particle destruction7 during stirring in the developing device. strength, sufficient fluidity to facilitate transport on the Magroll sleeve and agitation with the toner, individual carrier particles uniformity in electrical and magnetic customization, and temperature control. The electrical customization is stable against environmental changes such as humidity, and it has sufficient durability to withstand long-term use.

It goes without saying that the quality of copy images in electrophotography is dominated by the hardware (type of developing equipment), especially the development process, but the developer used in the development process also plays an extremely important role. It shows the In particular, from the viewpoint of improving the quality of copy images that faithfully reproduce the original images, various improvements have been made to developers, that is, carriers and toners.

Conventionally, various materials have been used as such carrier materials, but the most commonly used is an amorphous iron powder carrier. Developers using amorphous iron powder carrier χ tend to have long and hard magnetic brush ears due to the large saturation magnetization of the iron powder and shape anisotropy.

This is particularly noticeable when a flat, amorphous iron powder carrier is used. The tips of the magnetic brushes also become rough, making it difficult to perform precise development with excellent gradation. However, in terms of achieving image density, a developer using an amorphous iron powder carrier is preferable, and is particularly suitable under development conditions where the development gap between the photoreceptor and the Magroll sleeve is relatively wide, so it is widely used. has been used.

On the other hand, developers using spherical iron powder carriers are used to improve gradation and achieve dense development, but because the carrier particles are spherical, they suffer from shape anisotropy. This factor disappears, and the magnetic brush ears become extremely short and dense, and the developing torque is considerably reduced, but this is far from sufficient.In other words, since the spherical iron powder carrier is iron powder, its specific gravity is too large. In addition, because the apparent density is large (more than 4.0 og/c!), carrier scattering, etc. are emitted (this makes it necessary to design mag rolls, etc., making it complicated).Furthermore, the stress on the toner is large (the developer life is In terms of image quality, relatively high-quality copy images with good gradation can be obtained, but the image density tends to be poor in general, and the surface of the photoreceptor Hardware measures have been taken, such as increasing the potential.

It has been reported that ferrite, which is an oxide material, should be used from the viewpoint of improving the quality of copied images and extending the life of the developer. The saturation magnetization of ferrite carrier is smaller than that of iron powder (200 emu 7 g) (4
0 to 70 emu/g), the ears of the magnetic brush become soft, allowing for precise development with excellent gradation, and since the specific gravity is lower than that of iron powder, the developing torque is also reduced, reducing stress on the toner. It has the advantage of being able to provide a developer with good durability and greatly reduced costs. On the other hand, since ferrite is custom-made, its electrical resistance, which is one of its electrical properties, is generally high, so the tone of the copied image is monotonous, resulting in a narrow range of use in terms of image quality. Furthermore, it has not reached a level where the copy image Z can be maintained stably against environmental changes such as humidity. There are ferrites coated with resin to improve environmental dependence 7, but the coating makes the electrical resistance even higher and the range of use is narrower in terms of image quality (and at the same time, it is relatively expensive, making it less economical). σ) will also be disadvantageous.

Problems to be Solved by the Invention The main purpose of the present invention is to eliminate the various drawbacks of the conventional carrier for electrophotographic developer as described above, and to provide a carrier that is suitable for customizing images and has good stability against environmental changes. , provides a durable and inexpensive carrier.

Since the carrier of the present invention is magnetite containing hematite 'Y, its electrical resistance is lower than that of ferrite, and therefore, it has the characteristic that the carrier and its electrical resistance can be varied over a wide range by coating with resin. Therefore, it is possible to create a custom-made carrier that is optimal for various hardware. Furthermore, since it is spherical, it has good fluidity, and its specific gravity is smaller than that of iron powder carriers and its apparent density is about the same as that of ferrite, so the developing torque is small and it is extremely advantageous in terms of durability. Saturation magnetization (σg) is 40 to 70 emu
/9, which is on the same level as ferrite, which allows the magnetic brush to move more softly and more precisely, making it possible to develop high-quality images. In addition, the reduction in saturation magnetization reduces the torque of the ear cut portion during conveyance on tube rolls, resulting in a carrier with a long life.

Any of the following methods can be used to manufacture the core material of the carrier of the present invention. That is, it is produced by spraying and granulating a uniform mixture of water and slurry of hematite powder and magnetite powder using a 7 spray dryer, followed by sintering and S crushing and 2nd classification process Z, or by oxidizing spherical magnetite particles. This is the way to do it.

The carrier σ3 in the present invention is 40 to 80 emu/
The measurement of 0σ3, which is
The maximum magnetization value at e is 7. When σS is less than 40 emu/g, it is difficult to ensure particle uniformity during production.

That is, although it is possible to produce a material with a density of 30 emu/7, the uniformity of individual particles (magnetic uniformity) cannot be obtained. Also 80em
If u/gχ is exceeded, the magnetic brush σ) is in the direction of becoming harder, and the characteristics of the present invention cannot be fully utilized, and in either case, the characteristics of the present invention σ) are lost, which is not preferable.

Further, the particle diameter of the spherical carrier in the present invention is 30 to 20
Preferably, it is 0μ.

Consisting of magnetite containing the above hematite σS
is 40 to 80 emu/9 and when a spherical core with a particle size of 30 to 200 μ is coated with resin, methyl ethyl ketone,
The resin component is dissolved in a solvent such as xylene, n-butanol, methylcyclohexane, methyl isobutyl ketone, toluene, etc., and the core material is immersed in the solution, or the core material is fluidized in advance, and the resin solution is sprayed onto it. This is done by After coating, heat treatment can be performed at a predetermined temperature depending on the type of resin used to obtain a coated carrier.

If14 used as a coating material for the core material in the present invention
There are no particular restrictions on the fat, and any resin that is soluble in ordinary solvents may be used. The optimum amount of resin coating varies depending on the type of resin and the type of hard material, but in order to clearly bring out the characteristics of the present invention, it should be 0.5 to 8% by weight, more preferably 1.5 to 6% by weight. Good 0 Furthermore, there are no particular restrictions on the toner used in combination with the carrier of the present invention, and toners manufactured by dispersing various well-known dyes and pigments of a wide range of materials including natural resins, natural and synthetic resins, and combination improving materials can be used. is used.

Example The present invention will be explained in more detail with reference to Example 1 below.

Example 1 Water slurry 7 was prepared by uniformly mixing a mixed powder in which 35% hematite powder was added to magnetite powder using a wet attritor. Next, spray drying was performed using this water slurry spray dryer to obtain spherical particles of 30 to 150 microns. The spherical particles were then sintered under a nitrogen atmosphere at a temperature of about 1200'C for about 2 hours, and then cooled.

After crushing the above-mentioned sintered hematite-containing spherical magnetite particles, they were classified to separate particles of 75 to 150 microns.

The saturation magnetization of the hematite-containing spherical magnetite particles was 60 emu/9.

Styrene acrylic resin (MH7015 manufactured by Moshoku Kasei Co., Ltd.) for 10 kg of the above hematite-containing spherical magnetite particles.
A toluene solution (resin content 10%) of 2ky4 was spray coated to obtain a carrier of the present invention.

A developer is prepared by stirring and mixing the resin coated carrier χ with a commercially available toner for magnetic brush development (negative polarity toner for XEROX 3870), and the developer is prepared by stirring and mixing the resin coated carrier χ with a commercially available magnetic brush developing toner (negative polarity toner for XEROX 3870).
When the L image was developed, a high quality image with good halftone reproducibility was obtained. Further, no significant change in image quality was observed even after 60,000 times of development.

Example 2 A water slurry of magnetite powder was spray-dried using a spray dryer to obtain spherical particles of 30 to 150 microns. The spherical particles were then sintered at a temperature of about 1200° C. for about 2 hours under a nitrogen atmosphere, and then cooled. After crushing the sintered spherical magnetite particles, the spherical magnetite particles were classified and separated into particles of 75 to 150 microns.The above spherical magnetite particles were heat-treated in a rotary kiln at 300°C for 3 hours to produce hematite-containing spherical magnetite. Particle 2 was obtained.

The electrophase magnetization of the hematite-containing spherical magnetite particles was 45 emu/i.

To the above hematite-containing spherical magnetite particles 10? The carrier of the present invention was obtained by spray coating the same resin solution 1 as in Example 1.

A developer was prepared using the above resin coated carrier in the same manner as in Example 1, and the electrostatic latent image on the selenium photoreceptor was developed.
A high-quality image with good halftone reproducibility is obtained, with a rating of 60.0
No significant change in image quality was observed even after 00 times of development.

Comparative Example 1 A water slurry of magnetite powder was spray-dried using a 7 spray dryer to obtain spherical particles of 30 to 150 microns. The spherical particles were then heated to about 1.200°C under a nitrogen atmosphere.
After sintering at a temperature of about 2 hours, it was cooled. After crushing the sintered spherical magnetite particles, they were classified to separate 75 to 150 micron (σ) particles.

The saturation of the above spherical magnetite particles is 86 emu/g
Met.

The above spherical magnetite particles were coated in the same manner as in Example 1, a developer was prepared in the same manner as in Example 1, and an electrostatic latent image was developed on a selenium photoreceptor.
Compared to the carrier of the present invention, the reproducibility of intermediate tones was poor, and images with high contrast and not high quality were obtained.

Comparative Example 2 A water slurry of magnetite powder was spray-dried using a spray dryer to obtain spherical particles of 30 to 150 microns. Next, the spherical particles were heated at about 1200°C under a nitrogen atmosphere.
After sintering at a temperature of about 2 hours, it was cooled. After crushing the sintered spherical magnetite particles, they were classified to separate 7 particles of 40 to 75 microns.

In the above spherical magnetite particle rotary kiln, 8
Heat treatment was performed in air at 00°C for 2.5 hours to obtain hematite-containing spherical magnetite particles 2.

The electrophase magnetization of the hematite-containing spherical magnetite particles was 35 emu/g.

Acrylic resin (BR83 manufactured by Mitsubishi Rayon) (7) for the above hematite-containing spherical magnetite particles 10 and 5c
A resin-coated carrier was obtained by applying a 1.5 kp Kesbre coating with l-toluene solution (resin content: 6%).

The above resin coated carrier was stirred and mixed with a commercially available magnetic brush developing toner (negative polarity toner for Toshiba BD8811) at ℃
When an electrostatic d image on a selenium photoreceptor was developed using developer Nr111, carrier adhesion to the selenium photoreceptor occurred.
It was impractical.

As a result of collecting the adhesion carriers 7 and investigating the magnetic customization, the saturation magnetism was 15 to 25 emu/g.

Example 3 A water slurry of magnetite powder was spray-dried using a 7 spray dryer to obtain spherical particles of 30 to 150 microns. Next, the spherical particles were heated at about 1200°C under a nitrogen atmosphere.
, 2 hours, and then cooled. After crushing the sintered spherical magnetite particles, they were classified to separate particles of 40 to 75 microns.

The above-mentioned spherical magnetite particles were heated to 4o in a fluidized bed.

C. for 30 minutes to obtain hematite-containing spherical magnetite particles 2.

The electrophase magnetization of the hematite-containing spherical magnetite particles was 73 emu/i.

The hematite-containing spherical gnetite particles 101y were spray-coated with 2.5kyY of toluene f81&c (resin content: 6%) of acrylic/l/resin (BR83 manufactured by Mitsubishi Rayon Co., Ltd.) to obtain a carrier of the present invention.

Stir and mix with the above-mentioned resin-coated carrieran commercially available magnetic brush developing toner (negative polarity toner for Toshiba BD8811),
When the developer was used and the electrostatic latent image on the selenium photoreceptor was developed, a high-quality image with relatively good halftone reproducibility was obtained.

Patent applicant: Kanto Denka Kogyo Co., Ltd. (external name)

Claims (3)

[Claims] (1) A carrier for an electrophotographic developer, characterized in that the core material is substantially spherical particles, the spherical particles are made of magnetite containing hemarwite, and the core material is coated with a resin. (2) The carrier for electrophotographic developer according to claim 1, which has a saturation magnetization of 40 to 80 emu/g. (3) The carrier for electrophotographic development according to claim 1, having a particle size of 30 to 200 μm.