JPS5997155A - Electrostatic image developing carrier - Google Patents

Abstract

PURPOSE:To form an electrostatic image developing carrier not causing sweeping streaks, image roughening, and crushing of characters on the obtained image by specifying saturation magnetization and a content of metallic iron. CONSTITUTION:Saturation magnetization is kept in 50-150emu/g and a content of metallic iron is regulated to 1-50wt%. Such an electrostatic image developing carrier is prepared by introducing pulverived iron powder 2 obtainable on the market through oxidative flames A and oxidizing it. A content of metallic iron varies on the basis of oxidation degrees, and saturation magnetization also changes. In the case of <50emu/g, scattering and attachment of the carrier occur, and in the case of >150emu/g, sweeping streaks and image roughening occur remarkably on an image, and crushing of characters takes place. The content of metallic iron can be controlled by selecting the particle diameter of the iron powder material, oxidation conditions, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carrier for developing an electrostatic image, and particularly to a carrier that constitutes an electrostatic image developer together with a toner.

In electrophotography, a photoreceptor consisting of a photoconductive element is given a uniform surface charge in a dark place, an electrostatic charge image is formed by imagewise exposure, and this electrostatic charge image is developed with a developer. A visual image is formed.

Methods for developing such electrostatic images can be broadly classified into liquid development methods and dry development methods. The liquid development method is a method in which development is carried out using a liquid developer made by dispersing various pigments and dyes as fine particles in an insulating organic liquid. This method uses a fine powder, usually called a toner, which contains a coloring agent such as black dispersed therein. In the latter method, toner is charged to a polarity opposite to that of the electrostatic charge image, and the charged toner is electrostatically attached to the electrostatic charge image to form a visible image. This dry developing method includes a method using a so-called one-component developer whose main component is only the above-mentioned toner, and a method using a so-called two-component developer where a carrier made of iron powder or glass beads is mixed with the toner. The former includes the bristle brush method, the Impressiro 7 method, and the powder cloud method, and the latter includes the magnetic brush method and the cascade method.

By the above-mentioned developing method, the visible image formed by the toner adhering to the electrostatic charge image can be transferred directly onto the photoreceptor, or directly or indirectly through an intermediate transfer member to paper or other image support. After being transferred onto the image, it is fixed by heat, pressure, solvent vapor, etc.

The present invention relates to a carrier for a two-component developer used in the magnetic brush method or cascade method among the above-mentioned developing methods, that is, a carrier that is mixed with a toner and used for developing an electrostatic image. , especially regarding iron powder carriers.

Conventionally, the iron powder used as a carrier has metallic iron accounting for more than 90% of its components, so the saturation magnetization is as high as about 200 emu/' in a magnetic field of 30,000 e, and for this reason, the ears formed on the developing brush are not exposed to light. If you rub your body with too much force, it may cause scratches or roughness in the resulting image.
Another disadvantage was that the resolution was poor and characters were distorted.

As a result of repeated research by the present inventors to solve the above drawbacks,
Focusing on the fact that sweeping marks, rough images, and crushed characters are phenomena that occur because the toner on the developing brush, which is causing the bubbling phenomenon, rubs the surface of the photoreceptor with strong force,
As a result of further research, it has been found that if the toner is developed with a force weaker than the force with which it is attracted by the charge lines of force on the photoreceptor, no scratches, rough images, or crushed characters will occur.
As a means for this purpose, the inventors discovered that it is necessary to use a carrier with low saturation magnetization to form so-called soft spikes on the developing brush and bring them into contact with the photoreceptor, leading to the completion of the present invention.

An object of the present invention is to provide a carrier for developing electrostatic images that does not cause scratches, rough images, or crushed characters in the resulting images.

The above object of the present invention is achieved by a carrier for developing an electrostatic image, which has a saturation magnetization of 50 to 150 emu/f and has a metal iron content of 1 to 50% by weight.

The electrostatic image developing carrier according to the present invention can be obtained by melting and oxidizing a commercially available pulverized iron powder carrier in an oxidizing flame using, for example, an oxidizing apparatus shown in FIG.

In FIG. 1, 1 is the main body of the oxidizer, and a supply section 3 for supplying pulverized metal iron powder 2 is installed in the upper part of the main body 1. 4 is inside the main body 1. It is a burner for forming the oxidation flame A, 5 is a fuel supply pipe such as oil, 6 is an air supply pipe, T is a product outlet part, 1C is the iron powder supplied from the supply part 3 2 is oxidizing flame A
After that, it is oxidized and discharged from the outlet T as a product.

It should be noted that as the iron powder oxidizing apparatus in the present invention, a known apparatus other than the apparatus shown in FIG. 1 can be used, and for example, the apparatus described in Japanese Patent Application Laid-Open No. 53-60379 can be used.

According to the above oxidation device, the surface of iron powder is oxidized and FeO
+ Fe2O3+ Iron oxides such as Fe3O4 are formed,
Metallic iron (Fa) remains as it is up to the middle part. From this, the content of metallic iron varies depending on the degree of oxidation, and the saturation magnetization also varies. In the present invention, saturation magnetization refers to the maximum magnetization value in a magnetic field of 30,000 e.

The saturation magnetization of the carrier in the present invention is 50 to 150 em
u/f, more preferably 70-130emu
/l. When the saturation magnetization is less than 50 emg/f, carrier scattering and carrier adhesion occur;
If it exceeds / f, sweeping lines, image roughness, and crushed characters will occur.

The content of metallic iron (Fe) in the carrier in the present invention is 1
-50% by weight, more preferably 5-40% by weight. This content can be controlled by the particle size of the iron powder material, oxidation treatment conditions, etc.

Although the particle size of the carrier according to the present invention is not limited, it is, for example, 20 to 1000 μm. Preferably 20-30
It is 0 μm.

The carrier according to the present invention may be mixed with other carriers such as ferrite, magnetite, etc. when forming a developer.

The toner constituting the developer together with the carrier of the present invention includes a coloring agent consisting of a natural or synthetic resin, a pigment such as carbon black, or various dyes, and, if necessary, [
A fine powder of a composition mixed and dispersed with a charge control agent for controlling triboelectrification is used. Examples of resins used include rosin, giltnite, and phenol.
Formaldehyde resin, p-zine modified phenol-formaldehyde resin, methacrylic resin, polystyrene resin, polyethylene resin, polypropylene resin, epoxy resin, coumaron-indene resin, Askuald, polyamide resin, polyurethane resin, polyester resin, styrene-acrylic acid copolymer , styrene-methacrylate copolymer, or a mixture thereof. Carbon black is the most typical coloring agent, but examples include nigrosine dye, aniline blue, carfoil blue, Coombe Yea A-1+Flutramarine Blue, DuPont Oil Red, quinoline Yep-, methylene blue chloride, phthalocyanine blue, and malachite green. A wide range of dyes can be used, including so-called reactive dyes such as offsalate, lamp black, rose bengal and mixtures thereof;
These need to be included in the toner in sufficient amounts to color the toner so that it can be developed to form a visible image. Generally, certain kinds of dyes and pigments are used as charge control agents that are added as necessary. The 5 Fetschwarz HBN (color index (N + 16tso), alcohol-soluble nigrosine (color index tooth 5o4t5), Sudan Chief Schwarz BB (color index 42tso) described in the publication No.
6150), Priri7nt Spirit Spartz TN (
(manufactured by Bayer), Zabonschwarz X (manufactured by Hoechst)
, triphenylmethane and other dyes are used, and in order to impart negative triboelectricity, Celsus Schwarz (R) is used.
G (Bayer AG!1 Ri, Ri p Mogenschwarz ETCO
(Color Index N1114645), Azo Oil Black R (6) (manufactured by National Aniline Co.), and metal-containing dyes such as Phthalocyanine Blue are used. In addition, when using a heated roller in the fixing process,
As a mold release agent to prevent the occurrence of offset phenomenon,
For example, fatty acid metal salts, low molecular weight polyalkylene resins, etc. can also be contained in the toner. A toner having the above-mentioned composition is, for example, mixed with each component, kneaded using hot rolls, cooled, pulverized, and then classified to have a desired particle size. The average particle diameter is 1 to 50 μm, preferably 2 to 30 μm. Any toner can be used in the developer to which the present invention is applied, but the proportion of toner mixed with the iron powder carrier of the present invention will vary depending on the content of metallic iron in the carrier according to the present invention. However, for example, in the case of a developer to which a magnetic brush method is applied, the amount is generally 0.1 to 20% of the developer weight, and in the case of a developer to which a cascade method is applied, it is generally 0.5 to 2%.

When an electrostatic charge image is developed using a developer to which the carrier of the present invention is applied as described above, a clear image with no streaks or image roughness is produced, regardless of whether it is applied to either the magnetic brush method or the cascade method. is obtained. In particular, when applied to a magnetic brush method using a developing electrode, clear images can be obtained even when a large number of copies are continuously developed using a transfer method.

The present invention will be described below with reference to Examples, but the present invention is not limited thereto. In addition, hereinafter, "parts" refers to "parts by weight" unless otherwise specified.

Example 1 A carrier containing 38.3% metallic iron (saturation magnetization 115 emu/P1200/300
mesh) was obtained, and the carrier, 100 parts of polyester resin, and 10 parts of carbon black had an average particle size of l.
A two-component developer with a toner amount of 4% by weight of the developer weight was prepared by mixing with a toner having a particle diameter of 0 μm. When this developer was used to print images on a U-BIX-V (manufactured by Konishiroku Photo Industry Co., Ltd.) modified copying machine, 8 copies/...
It had enough resolution to clearly reproduce images, and there were no image roughness, scratches, crushed letters, or capri. The amount of charge at that time was 22 μCat.

Example 2 In Example 1, carrier containing 48% metallic iron (saturation magnetization 142 emu/f, 200/300 mes
h), 100 parts of styrene-10-acrylic acid copolymer, which is the same as the toner for the U-BIX-V copier manufactured by Konishi Roku Photo Industry Co., Ltd., was used as the binder resin, and 3.5 parts of polypropylene was used as the release agent. A two-component developer containing 5% by weight of toner was prepared in the same manner as in Example 1, except that the developer was used, and image printing was carried out under the same conditions as in Example 1.

As a result, the resolution was high enough to clearly reproduce the 8 lines per battle, and there was no image roughness, smeared edges, crushed letters, or fog. The amount of charge at that time is 18μc
/r.

Example 3 In Example 1, a carrier containing 26.7% of metallic iron had a saturation magnetization of 80 emu/S' and 100/200 m.
esh), the same comb as in Example 1, and the toner amount is 2.
A two-component developer was prepared, and image printing was carried out under the same conditions as in Example 1.

As a result, it had a resolution sufficient to clearly reproduce 8 lines/Wa, and no image roughness, smeared lines, crushed characters, or fog were observed. The amount of charge at that time is 24μc
/f.

Example 4 In Example 1, a carrier containing metallic iron 17.7X (saturation magnetization 53 emu/l, 200/300 m
esh), and the toner amount was 4 in the same manner as in Example 1.
．． A two-component developer having a concentration of 5% by weight was prepared, and image printing was carried out under the same conditions as in Example 1.

As a result, it had enough resolution to clearly reproduce 8 lines/m, and no image roughness, smeared lines, crushed characters, or fog were observed. The amount of charge at that time was 19μc/
It was f.

Comparative Example 1 A carrier containing 90% metallic iron in Example 1 (saturation magnetization 203emu/V, 100/200mes
A two-component developer with a toner amount of 2% by weight was prepared in the same manner as in Example 1 except that h) was used.
I made the illustrations by request.

As a result, the reproduction of 5 lines per shot was the limit, and there were some defects such as poor image quality and sweeping marks.

Comparative Example 2 In Example 1, iron oxide powder with metallic iron θ% (saturation magnetization 30 emu/P, 100/200 mes) was used as a carrier.
A two-component developer containing 2% by weight of toner was prepared in the same manner as in Example 1, except that b) was used, and image printing was carried out under the same conditions as in Example 1.

As a result, carrier scattering and carrier adhesion occurred.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an oxidizing device preferably used in the present invention. Patent applicant: Konishiroku Photo Industry Co., Ltd., agent patent attorney
Nobuaki Sakaguchi (and 1 other person)

Claims (1)

[Claims] A carrier for developing an electrostatic image, characterized in that it has a saturation magnetization of 50 to 150 emu/f and a metal iron content of t-1 to 50% by weight.