JPS58144839A - Magnetic carrier particles - Google Patents

Abstract

PURPOSE:To provide magnetic carrier particles used for magnetic brush development, capable of forming an image superior in resolution, minute accuracy, black solid uniformity, gradation, etc., by using ferrite particles having spinel structure and average particle diameter smaller than a specified value. CONSTITUTION:Necessary metal oxides, such as FeO or Fe2O3 are mixed in water into slurry, granulated, dried, heat treated, crushed, and classified to obtain ferrite particles having average particle diameter not exceeding 30mum and spinel structure. An especially preferable ferrite is ferrite or magnetite consisting of <=60mol% MO (M is Ni, Mn, Mg, Zn, Cu, or Co) in terms of divalent metal oxide, and >=40mol% Fe2O3 in terms of trivalent metal oxide, and spinel structure. These ferrite particles are used for magnetic carrier particles, and combined with a toner to prepare a developer.

Description

[Detailed description of the invention] ! Background of the invention Technical field The present invention relates to magnetic carrier particles.

More specifically, it relates to special K, magnetic carrier particles used in magnetic brush development.

Prior art and its problems Conventionally, iron powder, 7-elite particles, etc. have been used as magnetic carrier particles in magnetic push development, and the average particle diameter is preferably 30 to 1000 μm sacrificial density. has been done.

However, when conventional carrier particles are used, image quality such as image resolution, density, black solid uniformity, and gradation is still not fully satisfactory.

Summer Purpose of the Invention The present invention was made in view of the above circumstances, and
The main object of the present invention is to provide magnetic carrier particles capable of obtaining images with improved image quality such as resolution, fine writing ability, solid black uniformity, and gradation.

As a result of intensive research into this objective, the present inventors discovered that this objective could be achieved when the average particle size of ferrite particles was made smaller than the conventional one, leading to the present invention. .

That is, the present invention is a magnetic carrier particle made of ferrite particles having a spinel structure and having an average particle diameter of less than 30/J#.

Note that there has been no example of using ferrite particles having such a particle size alone as a carrier.

Concrete structure of the invention Hereinafter, the specific configuration of the present invention will be explained in detail.

The magnetic carrier particles of the present invention consist of ferrite with a spinel structure.

In this case, ferrites with a spinel structure include so-called soft ferrites such as 2-3 spinel and 1-3 spinel, as well as magnetite (Fe, 0.
, or Maghemai) (r-Fe, 05).

Among such ferrites, the following i) or ii) are preferable in terms of magnetic properties.

i) 60 mol% or less MO in terms of divalent metal oxide
・(However, M is Ni, Mn, MW, Z
n.

Represents a combination of one or more of Cu and CO. ) and 40 mol% in terms of trivalent metal oxide
A ferrite with a spinel structure consisting of the above Fe and (J5).

In this case, when M is composed of two or more kinds of metals, the composition ratio thereof can be set arbitrarily.

ii) Magnetite.

Among the ferrites of i) and ii) which are preferably used, the following ia) or ib) is preferable among the ferrites of i).

is) In the above e), the above M is Ni or Mn.

One or a combination of two to five of My%Cu and Zn. In this case, when M is a combination of two or more metals, the composition ratio can be arbitrary.

ib) 1) l (wherein, M is Ni, Mn, M
f, Cu and Zn, with an atomic ratio of 2
In combination with 0% or less CO.

In this case, when two or more of M, Ni, Mn, MP, Cu, and Zn are included.

The composition ratio can be set arbitrarily.

In the case of the above compositions ia) and ib), the saturation magnetization is extremely strong, and so-called carrier-pulling development in which carriers adhere to the photoreceptor or development in which carriers scatter from the magnetic brush are completely eliminated.

Ferrite particles with such a composition generally contain:
It may be contained within a range of 5 mol% of the total.

Such ferrite particles have an average particle size of less than 30 microns.

If the average particle diameter is 30 μm or more, the quality, especially the dissolving power, density, uniformity, and gradation, will deteriorate. In addition, the image quality becomes high-contrast, making it easy for the viewer to get tired.

On the other hand, if the average particle diameter becomes too small, adhesion of carrier particles to the photoreceptor and carrier scattering become apparent, and the fluidity of the developer deteriorates. Therefore, the average particle diameter is 5a
In particular, when the average particle diameter is 5 to 25 sm, more preferable results are obtained.

Note that the particle distribution is generally set so that about 70% of the total number is within ±30% of the average particle diameter.

In addition, such ferrite particles have a ferrite layer formed on their surface, or contain a plurality of particles in a resin to serve as a carrier.

Therefore, the magnetic carrier particles of the present invention have high mechanical strength, little thermal deterioration, little deterioration of properties over time, long life, and no decrease in saturation magnetization due to decrease in space factor. , and SaraK are easy to manufacture.

7 constituting the magnetic carrier particles of the present invention as described above
It is preferable that the resistance of the engineered particles is 10 4 to 10 16 Ω, more preferably 10 6 to 10 12 Ω, when 100 Ω is applied when the following measurement is performed.

The resistance measurement of ferrite particles is performed as follows, imitating the magnetic brush development method.

That is, the north pole and the south pole are made to face each other with an opening between the magnetic poles of 1jJ8■. In this case, the surface magnetic flux density of the magnetic pole is 150
0 Gauss, and the opposing magnetic pole area is 10×30×.
Nonmagnetic parallel plate electrodes are arranged with a magnetic pole distance K and an interelectrode gap of 8 mm, a test sample 200119 is placed between the electrodes, and the sample is held between the electrodes by magnetic force. In this way, the resistance may be measured using a Zetsuretsu resistance meter or an ammeter.

When the resistance measured in this manner exceeds 101'Ω, the image density decreases. On the other hand, when it is less than 10'Ω, the image quality tends to be high contrast.

Furthermore, the saturation magnetization σ of the ferrite particles in the present invention,
is preferably greater than or equal to 35 emu/.
At this time, the so-called carrier attraction in which the carrier adheres to the photoreceptor is eliminated, and the scattering of the carrier during repeated development is eliminated. In this case, - is 4
More preferable results are obtained when it is at least gemu/r.

Magnetic carrier particles made of such ferrite particles are generally described in U.S. Pat. No. 3,839,029 and U.S. Pat.
No. 1, No. 3926657, etc.

That is, first, a brew of the corresponding metal is prepared.

Next, a solvent, usually water, is added to form a slurry using, for example, a ball mill at equal pressure, and a dispersant, a binder, etc. are added as necessary.

Then, it is granulated and dried using a spray dryer.

After that, firing is performed in a predetermined firing atmosphere and firing temperature profile. In this case, if the firing is performed using a fluidized fluidized furnace, rotary kiln, tunnel furnace, etc.
Particles having the average particle diameter as described above are efficiently produced.

After the firing, the particles are crushed or dispersed and then dispersed to a desired particle size to produce the magnetic carrier particles of the present invention.

(2) Specific effects of the invention The magnetic carrier particles of the invention are combined with a toner to form a present agent. In this case, there are no restrictions on the type of toner used.

Further, in obtaining an electrostatic copy image, there are no particular limitations on the magnetic brush development method, photoreceptor, etc. to be used (an electrostatic copy image can be obtained according to a known magnetic brush development method).

V. Specific Effects of the Invention According to the present invention, extremely good image quality can be obtained. That is, the resolution, density, black solid uniformity, gradation, etc. are extremely good.

Furthermore, the image has a soft tone and is less tiring for the viewer.

In addition, since it is made of ferrite particles, it is possible to easily obtain one image and images with different gradations by changing the composition and firing conditions and arbitrarily changing the amount of magnetism and resistance.

Furthermore, since it does not have a coating layer and is not contained in the resin as an aggregate, there is little deterioration in properties during long-term use (it has good durability and a long lifespan).

Moreover.

There is no deterioration in magnetic properties due to the inclusion of a resin component. In addition, the number of manufacturing steps is reduced, manufacturing is easy, and manufacturing costs are low.

The present inventors conducted various experiments to confirm the effects of the present invention.

An example is shown below.

Experimental Example The corresponding metal oxides were prepared at the respective child composition ratios (divalent metal oxide and Fe, converted to 05pc) shown in Table 1 below, and 1 part by weight of water was added per 1 part by weight of the blended composition. The mixture was mixed in a ball mill for 5 hours to form a slurry, and appropriate amounts of a dispersant and a binder were added thereto.

Next, the mixture was granulated and dried using a spray dryer at a temperature of 150° C. or higher.

Each granule was fired using a fluidized bed furnace at the maximum temperature shown in Table 1 and in the atmosphere also shown in Table 1. In Table 1, A represents an air atmosphere and N represents a nitrogen atmosphere.

Thereafter, the particles were crushed and classified to obtain ferrite particles having average particle diameters as shown in Table IK.

In this case, the average particle size is the average particle size of 5000 particles randomly extracted under the field of an electron microscope. In addition, in the table, those with an average particle size of 20 μm are in the particle size range of 5 to 30 μm, and those with an average particle size of 40 μm are in the range of 25 μm.
The particle size range is between 55μ and 70μ, and the average particle size is 70μ and 40 to 100μ.

On the other hand, X-ray analysis of each ferrite particle revealed that each particle had a spinel structure.

Moreover, it was found that the metal content corresponded to the charging composition shown in Table 1.

Next, the saturation magnetization t1m(
efrlu/f) and the resistance (l) when 100 V is applied
was measured. The results are shown in Table 11C.

In this case, the saturation magnetization σ□ was measured with a vibrating sample type f) magnetic needle.

Further, the resistance was measured using an insulation resistance needle when 100V was applied to the 200 Misaki sample as described above.

Next, each of the seven-functional light particles obtained as described above was used as magnetic carrier particles, and the toner concentration was 11.5% by weight.
A commercially available two-component toner (average particle size 11.5±1.
A developer was prepared by mixing with 5μ inertia).

Magnetic brush development was performed using each developer using a commercially available electrostatic copying machine, and the image quality of the obtained images was evaluated.

In this case, the surface magnetic flux density of the magnet roller for the magnetic brush is 1000 Gauss, the rotation speed is 13 Q rpm for the magnet roller, and 3 Orpm for the sleeve roller. Also, the magnetic roller-photoreceptor gap is 30±
It is 0.3m.

Furthermore, a binder type CdS photoreceptor was used as the photoreceptor, and the highest surface potential was 5oov.

Using a test chart made by Data Quest, solving power (
book/fi) was measured.

In addition, the image of the test chart was visually observed to evaluate the denseness. The evaluation was performed on a 5-grade scale from A to E, with A being the best and E being the worst.

Furthermore, gradation was evaluated visually.

The evaluation uses a 13-step gray scale.

Determine whether or not the classification can be determined, and the number of stages (1 to 13)
It was displayed in

In addition, softness was also evaluated visually. In this case, ranking was performed and displayed numerically.

These results are shown in Table 2 below.

Note that in each sample, carrier attraction and carrier scattering were extremely small.

Table 2 Sample A ps image power denseness gradation soft tonality (
book/dew) 1 6.3 A 10
14 6.3 A 1
0 15 6.3 B
11 16 6.3 A
10 17 (comparison) 4.5D
63 8 6.3 A 10
19 5.6 A
8 210 6.3 A
10 111 6.3
A 10 112 6.3
The results shown in Table 2 indicate that the magnetic carrier particles of the present invention provide electrostatic images of extremely good quality compared to those having an average particle diameter of 30 μm or more.

Representative Patent Attorney Yo Ishii - Procedural amendment (voluntary) Kazuo Wakasugi, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 21923 of 1982, Title of the invention, Magnetic Carrier Particles3, Person making the amendment Case Relationship with patent application colonel
Nihonbashi-chome 13-1, Chuo-ku, Tokyo Name
(306) TDC Co., Ltd. Representative Hiroshi Otoshi 4, Agent 171 Address 5-17-11 Nishiikebukuro, Toshima-ku, Tokyo
No. Yabe Building, 1st Floor Telephone: 98B-16806 The statement in column 13, Detailed Description of the Invention j of the Statement of Contents of Amendment is amended as follows.

1) In the 4th and 5th lines of page 11, amend "air atmosphere 1" to "r nitrogen atmosphere containing oxygen".

Claims (1)

[Claims] Magnetic carrier particles comprising heptadite particles having a spinel structure and having an average particle diameter of less than 30 μm.